关于足细胞中糖代谢/能量代谢重编程的研究

Approximately 30-40% of patients with diabetes develop diabetic kidney disease (DKD). Identifying decisive factors for DKD initiation is crucial. Here, we observed that glomerular podocytes in male and female patients with DKD and db/db mice specifically displayed BCAA catabolic defects. Podocyte-specific PP2Cm (a key BCAA catabolism enzyme) knockout or exogenous BCAA supplementation induced DKD phenotypes including podocyte dysfunction/apoptosis, glomerular pathology, and proteinuria in high-fat (HF)-diet-fed male mice. Mechanistically, BCAAs promoted PKM2 depolymerization and inactivation in podocytes. Depolymerized PKM2 suppressed glucose oxidative phosphorylation (OXPHOS), diverting glucose metabolism towards serine biosynthesis and folate metabolism. Depolymerized PKM2 is also co-transported with DDIT3 into the nucleus, acting as a co-transcriptional factor to enhance DDIT3 transcriptional activity, which promotes Chac1 and Trib3 expression and directly inducing podocyte apoptosis. Thus, BCAA catabolic defects may be one of the missing factors that determine DKD initiation. Targeting BCAA catabolism or PKM2 activation is a promising DKD prevention strategy. Previous studies have suggested that branched chain amino acids (BCAA) may contribute to the development of diabetic kidney disease (DKD).Here the authors report that genetic disruption of BCAA catabolism in podocytes or exogenous BCAA supplementation can trigger DKD initiation via rewiring of glucose metabolism in mice.

Recent studies have reported that Angiotensin II (Ang II) contributes to podocyte injury by interfering with metabolism. Glycolysis is essential for podocytes and glycolysis abnormality is associated with glomerular injury in chronic kidney disease (CKD). Glycerol-3-phosphate (G-3-P) biosynthesis is a shunt pathway of glycolysis, in which cytosolic glycerol-3-phosphate dehydrogenase 1 (GPD1) catalyzes dihydroxyacetone phosphate (DHAP) to generate G-3-P in the presence of the NADH. G-3-P is not only a substrate in glycerophospholipids and glyceride synthesis but also can be oxidated by mitochondrial glycerol-3-phosphate dehydrogenase (GPD2) to regenerate DHAP in mitochondria. Since G-3-P biosynthesis links to glycolysis, mitochondrial metabolism and lipid synthesis, we speculate G-3-P biosynthesis abnormality is probably involved in podocyte injury. In this study, we demonstrated that Ang II upregulated GPD1 expression and increased G-3-P and glycerophospholipid syntheses in podocytes. GPD1 knockdown protected podocytes from Ang II-induced lipid accumulation and mitochondrial dysfunction. GPD1 overexpression exacerbated Ang II-induced podocyte injury. In addition, we proved that lipid accumulation and mitochondrial dysfunction were correlated with G-3-P content in podocytes. These results suggest that Ang II upregulates GPD1 and promotes G-3-P biosynthesis in podocytes, which promote lipid accumulation and mitochondrial dysfunction in podocytes.

No abstract available

Podocytes, a type of highly specialized epithelial cells, require substantial levels of energy to maintain glomerular integrity and function, but little is known on the regulation of podocytes’ energetics. Lack of metabolic analysis during podocyte development led us to explore the distribution of mitochondrial oxidative phosphorylation and glycolysis, the two major pathways of cell metabolism, in cultured podocytes during in vitro differentiation. Unexpectedly, we observed a stronger glycolytic profile, accompanied by an increased mitochondrial complexity in differentiated podocytes, indicating that mature podocytes boost both glycolysis and mitochondrial metabolism to meet their augmented energy demands. In addition, we found a shift of predominant energy source from anaerobic glycolysis in immature podocyte to oxidative phosphorylation during the differentiation process. Furthermore, we identified a crucial metabolic regulator for podocyte development, pyruvate kinase M2. Pkm2-knockdown podocytes showed dramatic reduction of energy metabolism, resulting in defects of cell differentiation. Meanwhile, podocyte-specific Pkm2-knockout (KO) mice developed worse albuminuria and podocyte injury after adriamycin treatment. We identified mammalian target of rapamycin (mTOR) as a critical regulator of PKM2 during podocyte development. Pharmacological inhibition of mTOR potently abrogated PKM2 expression and disrupted cell differentiation, indicating the existence of metabolic checkpoint that need to be satisfied in order to allow podocyte differentiation.

No abstract available

Metabolic adaptation of podocytes plays an important role in diabetic kidney disease (DKD) progression. Recent studies have highlighted the importance of metabolic regulation in maintaining podocyte function under diabetic stress conditions. While hepatocyte nuclear factor 4 alpha (HNF4α) expression is elevated in diabetic podocytes and is known to regulate cellular metabolism in other tissues, its specific role and downstream metabolic effects in podocyte metabolism remain unclear. Understanding this mechanism is important, as podocytes require precise metabolic control to maintain their specialized functions. To investigate the metabolic regulatory role of HNF4α, we generated stable HNF4α-overexpressing mouse podocytes using lentiviral vectors. Metabolic changes were evaluated by measuring oxygen consumption rate (OCR), while the underlying mechanisms were assessed through Western blot analysis of metabolic enzymes and transcription factors. To determine the effect on cell growth, we performed cell cycle analysis using flow cytometry and proliferation assays. We found increased HNF4α expression in podocytes from db/db mice and DKD patients. To investigate the functional implications of this increased expression, we established HNF4α-overexpressing mouse podocytes. Western blot analysis showed upregulation of metabolic transcription factors, particularly ChREBP and SREBP, compared to control cells, along with increased protein levels of glycolytic enzymes, including PKM and HK2. Seahorse analysis demonstrated enhanced mitochondrial function in these cells, with increased basal OCR and maximal respiratory capacity compared to controls. Flow cytometry analysis revealed enhanced cell cycle progression in HNF4α-overexpressing podocytes, as evidenced by increased S phase population. Our findings suggest that HNF4α influences podocyte metabolic pathways, potentially involving ChREBP/SREBP signaling, and affects cell cycle progression. These results provide insights into the role of HNF4α in podocyte metabolism, which may contribute to our understanding of podocyte regulation in DKD.

BACKGROUND Diabetic kidney disease (DKD) is a chronic disease characterized by high prevalence and mortality rates. Podocyte injury and mitochondrial metabolic disorder are crucial in its progression. Sirtuin3 (SIRT3), a mitochondrial NAD+-dependent deacetylase, exerts renoprotective effects in various kidney pathologies by modulating the acetylation status and activity of energy metabolism related substrates. However, its specific roles in podocytes homeostasis during DKD progression remain unclear. We previously reported the role and acetylation level of mitochondrial pyruvate carrier 2 (MPC2) in DKD, but the regulatory mechanism between SIRT3 and MPC2 has not been elucidated. This study aims to investigate the effect of SIRT3 on mitochondrial reprogramming in podocytes and explore the association between SIRT3 and MPC2 during DKD progression. RESULT SIRT3 expression was downregulated in hyperglycemia-induced podocytes in vivo and in vitro. SIRT3 deficiency aggravated podocyte apoptosis and mitochondrial homeostasis dysregulation, as evidenced by increased ROS production, decreased mitochondrial membrane potential and diminished ATP level. However, the overexpression of SIRT3 alleviated these alterations. In addition, we identified a binding interaction between SIRT3 and MPC2. SIRT3 deacetylated MPC2 at lysine K19/K27, mechanistically implicated in the podocyte injury in the process of DKD. CONCLUSION This study validated that hyperglycemia-induced SIRT3-mediated MPC2 acetylation contributes to mitochondrial dysfunction and cellular apoptosis.

Unlike classical protein kinase A, with separate catalytic and regulatory subunits, EPACs are single chain multi-domain proteins containing both catalytic and regulatory elements. The importance of cAMP-Epac-signaling as an energy provider has emerged over the last years. However, little is known about Epac1 signaling in chronic kidney disease. Here, we examined the role of Epac1 during the progression of glomerulonephritis (GN). We first observed that total genetic deletion of Epac1 in mice accelerated the progression of nephrotoxic serum (NTS)-induced GN. Next, mice with podocyte-specific conditional deletion of Epac1 were generated and showed that NTS-induced GN was exacerbated in these mice. Gene expression analysis in glomeruli at the early and late phases of GN showed that deletion of Epac1 in podocytes was associated with major alterations in mitochondrial and metabolic processes and significant dysregulation of the glycolysis pathway. In vitro, Epac1 activation in a human podocyte cell line increased mitochondrial function to cope with the extra energy demand under conditions of stress. Furthermore, Epac1-induced glycolysis and lactate production improved podocyte viability. To verify the in vivo therapeutic potential of Epac1 activation, the Epac1 selective cAMP mimetic 8-pCPT was administered in wild type mice after induction of GN. 8-pCPT alleviated the progression of GN by improving kidney function with decreased structural injury with decreased crescent formation and kidney inflammation. Importantly, 8-pCPT had no beneficial effect in mice with Epac1 deletion in podocytes. Thus, our data suggest that Epac1 activation is an essential protective mechanism in GN by reprogramming podocyte metabolism. Hence, targeting Epac1 activation could represent a potential therapeutic approach.

No abstract available

T‐2 toxin causes renal dysfunction with proteinuria and glomerular podocyte damage. This work explores the role of metabolic disorder/reprogramming‐mediated epigenetic modification in the progression of T‐2 toxin‐stimulated podocyte injury. A metabolomics experiment is performed to assess metabolic responses to T‐2 toxin infection in human podocytes. Roles of protein O‐linked‐N‐acetylglucosaminylation (O‐GlcNAcylation) in regulating T‐2 toxin‐stimulated podocyte injury in mouse and podocyte models are assessed. O‐GlcNAc target proteins are recognized by mass spectrometry and co‐immunoprecipitation experiments. Moreover, histone acetylation and autophagy levels are measured. T‐2 toxin infection upregulates glucose transporter type 1 (GLUT1) expression and enhances hexosamine biosynthetic pathway in glomerular podocytes, resulting in a significant increase in β‐arrestin‐1 O‐GlcNAcylation. Decreasing β‐arrestin‐1 or O‐GlcNAc transferase (OGT) effectively prevents T‐2 toxin‐induced renal dysfunction and podocyte injury. Mechanistically, O‐GlcNAcylation of β‐arrestin‐1 stabilizes β‐arrestin‐1 to activate the mammalian target of rapamycin (mTOR) pathway as well as to inhibit autophagy during podocyte injury by promoting H4K16 acetylation. To sum up, OGT‐mediated β‐arrestin‐1 O‐GlcNAcylation is a vital regulator in the development of T‐2 toxin‐stimulated podocyte injury via activating the mTOR pathway to suppress autophagy. Targeting β‐arrestin‐1 or OGT can be a potential therapy for T‐2 toxin infection‐associated glomerular injury, especially podocyte injury.

No abstract available

Background: Significant metabolic reprogramming occurs in diabetic kidney disease (DKD). Metabolomics studies of murine models of DKD demonstrate increased glucose metabolism and urinary and kidney lactate production. However, whether such changes occur in individuals with type 1 diabetes (T1D), and the temporal nature of such reprograming with respect to clinical DKD has not been systematically investigated. Stable isotope resolved mass spectrometry using [U-C13] glucose allows dynamic measurement and tracing of relevant glucose-derived metabolic pathways. We performed glycemic clamp study with [U-C13] glucose to evaluate how kidney metabolism is altered in T1D. Methods: Euglycemic-hyperglycemic clamp studies with [U-13C] glucose were conducted in matched healthy control (HC), and in T1D individuals with established early DKD, and without clinical microvascular complications. All groups had similar estimated glomerular filtration rates (eGFR, CKD-EPI equation). Urine and plasma were collected throughout the course of the clamp study. Blood glucose levels were maintained at 100 mg/dl ( ± 20) for the euglycemic clamp and 300 mg/dl ( ± 20) for the hyperglycemic clamp arms of the study. Urine was analyzed with LC-MS for labeled urinary metabolites which reflect kidney metabolism. Results: Urinary metabolites in the glycolytic and TCA cycle (mitochondrial) were detected in all three groups. Analysis of the TCA cycle metabolite isotopologues (malate, fumarate and α -ketoglutarate) under hyperglycemic clamp demonstrated significantly increased labeled glucose incorporation into the HC urine in comparison to T1D individuals with and without DKD. Incorporation into citrate and cis-aconitate were significantly elevated in the HC group only versus T1D DKD group. Conclusions: These metabolic flux labeling studies suggest that T1D results in diminished kidney mitochondrial metabolism, compared to HC under hyperglycemic conditions. This difference was even more pronounced between HC and T1D with DKD. Our data strongly suggests that metabolic changes occur in T1D that results in reduced glucose mitochondrial metabolism, even prior to clinical DKD.

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease, characterized by progressive renal injury driven by mitochondrial dysfunction and metabolic reprogramming. Excessive mitochondrial fission, mediated by dynamin-related protein 1 (Drp1), contributes to mitochondrial fragmentation and cellular injury in the diabetic kidney. Here, we investigate the therapeutic potential of P110, a selective inhibitor of Drp1-mediated mitochondrial fission, in experimental models of DN. We demonstrate that P110 effectively reduces mitochondrial fragmentation and restores metabolic balance in renal tubular cells from DN patients. In streptozotocin (STZ)-induced diabetic mice and db/db mice, P110 treatment significantly mitigates renal injury, as evidenced by decreased fibrosis, inflammation, and podocyte injury, despite having no impact on hyperglycemia or body weight loss. Mechanistically, P110 disrupts the interaction between Drp1 and Fis1, thereby inhibiting mitochondrial fission, and activates the AMPK/PGC-1α/TFAM pathway, promoting mitochondrial biogenesis and function. Our findings suggest that targeting mitochondrial fission with P110 offers a novel therapeutic strategy for preventing and treating DN, potentially addressing a critical gap in current diabetic nephropathy management.

Podocytes are crucial for regulating glomerular permeability. They have foot processes that are integral to the renal filtration barrier. Understanding their energy metabolism could shed light on the pathogenesis of filtration barrier injury. Lactate has been increasingly recognized as more than a waste product and has emerged as a significant metabolic fuel and reserve. The recent identification of lactate transporters in podocytes, the expression of which is modulated by glucose levels and lactate, highlights lactate's relevance. The present study investigated the impact of lactate on podocyte respiratory efficiency and mitochondrial dynamics. We confirmed lactate oxidation in podocytes, suggesting its role in cellular energy production. Under conditions of glucose deprivation or lactate supplementation, a significant shift was seen toward oxidative phosphorylation, reflected by an increase in the oxygen consumption rate/extracellular acidification rate ratio. Notably, lactate dehydrogenase A (LDHA) and lactate dehydrogenase B (LDHB) isoforms, which are involved in lactate conversion to pyruvate, were detected in podocytes for the first time. The presence of lactate led to higher intracellular pyruvate levels, greater LDH activity, and higher LDHB expression. Furthermore, lactate exposure increased mitochondrial DNA-to-nuclear DNA ratios and resulted in upregulation of the mitochondrial biogenesis markers peroxisome proliferator-activated receptor coactivator-1α and transcription factor A mitochondrial, regardless of glucose availability. Changes in mitochondrial size and shape were observed in lactate-exposed podocytes. These findings suggest that lactate is a pivotal energy source for podocytes, especially during energy fluctuations. Understanding lactate's role in podocyte metabolism could offer insights into renal function and pathologies that involve podocyte injury.

Lactate is a cellular product of glycolytic metabolism, serving as both an additional oxidative energy substrate and a signaling molecule in metabolic regulation. Plasma lactate levels are elevated in diabetes, and chronic extracellular lactic acidosis is recognized as a negative prognostic marker for the disease. The development of diabetic kidney disease is closely associated with podocyte injury, which forms a crucial layer of the glomerular filtration barrier. Given that high extracellular glucose concentrations also induce lactate production and excretion in podocytes, we hypothesize that an appropriate LDH expression pattern is crucial for maintaining proper podocyte metabolism and function. Our research shows that hyperglycemia significantly decreases lactate dehydrogenase activity in podocytes. Specifically, reduced LDHA expression under hyperglycemic conditions contributes to metabolic disturbances in these cells. Lower LDH activity results in decreased glycolytic activity, altered expression of monocarboxylate transporters, reduced insulin-dependent glucose uptake, and a decrease in the number of podocyte foot processes. These findings underscore the essential role of LDHA in the metabolic adaptation of podocytes to elevated glucose levels typical of diabetes. By elucidating the molecular mechanisms underlying podocyte injury, our study provides new insights into potential therapeutic targets for preventing or mitigating diabetic kidney disease.

Secretory phospholipase A2 group IB (sPLA2-IB) and M-type phospholipase A2 receptor (PLA2R) are closely related to proteinuria and idiopathic membranous nephropathy (IMN). Podocytes are important components of the glomerular filtration barrier and glucose metabolism, including glycolysis and tricarboxylic acid (TCA) cycle, is crucial for maintaining podocyte physiological function. Aberrant energy metabolism has been reported in proteinuria diseases, including diabetic nephropathy. However, altering energy states in podocytes in IMN remain unknown. The study aimed to determine whether sPLA2-IB induces energy metabolism abnormalities in podocytes. Cultured podocytes were treated with sPLA2-IB. siRNAs were used to knockdown expression of HIF-1α and PLA2R. Adenosine triphosphate (ATP) levels, the oxygen consumption rate and lactate content were assessed. Key enzyme of glycolysis, PKM2 and LDHA, TCA cycle-related enzymes and mTOR/HIF-1α pathway, were analyzed by PCR and immunoblotting. MTT assay was used for cell viability and phalloidin for cytoskeleton staining. sPLA2-IB induced insufficient energy states in podocytes, by decreased ATP production, increased lactate accumulation and reduced oxygen consumption rates. Under sPLA2-IB stimulation, LDHA and PKM2 were increased, while TCA cycle-related enzymes (CS, FH and SDHD) were decreased, with upregulated mTOR and HIF-1α. Mechanically, HIF-1α knockdown mitigated sPLA2-IB -induced LDHA upregulation and downregulated TCA cycle-related enzymes. Rapamycin (inhibitor of mTOR) reversed decreased ATP levels and oxygen consumption. 3-MA (activator of mTOR) aggravated lactate production. PLA2R knockdown reversed PKM2 and LDHA upregulation, FH and SDHD downregulation, and increased mTOR and HIF-1α expression. PLA2R activation by sPLA2-IB caused abnormal energy states in podocytes. The underlying mechanism involved the activation of mTOR/HIF-1α pathway.

Diabetic kidney disease (DKD) is a major complication of diabetes mellitus, characterized by podocyte injury and lipid accumulation, which contribute to high morbidity and mortality. Current treatments primarily alleviate symptoms, underscoring the need for targeted therapies to address the underlying mechanisms of DKD progression. This study explores the protective effects of dapagliflozin (DAPA), a selective sodium-glucose cotransporter 2 (SGLT2) inhibitor, on podocyte lipotoxicity and its regulatory role in the estrogen-related receptor alpha (ERRα)-acyl-CoA oxidase 1 (ACOX1) axis. Using db/db mice and streptozotocin-induced DKD models, we demonstrate that DAPA significantly reduces the urinary albumin-to-creatinine ratio (ACR) and improves renal pathology by alleviating glomerular hypertrophy, mesangial matrix expansion, and podocyte foot process effacement. DAPA also decreases triglyceride and free fatty acid accumulation in glomeruli, as evidenced by Oil Red O and BODIPY staining. Mechanistically, DAPA upregulates ERRα and ACOX1 expression in podocytes, enhancing fatty acid oxidation (FAO) and mitigating lipidtoxicity. Loss of ERRα exacerbates lipid-induced podocyte injury, while ERRα overexpression confers protective effects. These findings highlight DAPA's renoprotective effects via modulation of the ERRα-ACOX1 axis, suggesting that targeting ERRα could be a promising therapeutic strategy for DKD.

Prolonged disruption in the balance of glucose can result in metabolic disorders. The kidneys play a significant role in regulating blood glucose levels. However, when exposed to chronic hyperglycemia, the kidneys' ability to handle glucose metabolism may be impaired, leading to an accumulation of glycogen. Earlier studies have shown that there can be a significant increase in glucose storage in the form of glycogen in the kidneys in diabetes. Podocytes play a crucial role in maintaining the integrity of filtration barrier. In diabetes, exposure to elevated glucose levels can lead to significant metabolic and structural changes in podocytes, contributing to kidney damage and the development of diabetic kidney disease. The accumulation of glycogen in podocytes is not a well-established phenomenon. However, a recent study has demonstrated the presence of glycogen granules in podocytes. This review delves into the intricate connections between hyperglycemia and glycogen metabolism within the context of the kidney, with special emphasis on podocytes. The aberrant storage of glycogen has the potential to detrimentally impact podocyte functionality and perturb their structural integrity. This review provides a comprehensive analysis of the alterations in cellular signaling pathways that may potentially lead to glycogen overproduction in podocytes.

Podocytes play a key role in diabetic nephropathy pathogenesis, but alteration of their metabolism remains unknown in human kidney. By using a conditionally differentiating human podocyte cell line, we addressed the functional and molecular changes in podocyte energetics during in vitro development or under high glucose conditions. In 5 mM glucose medium, we observed a stepwise activation of oxidative metabolism during cell differentiation that was characterized by peroxisome proliferator‐activated receptor‐γ coactivator 1α (PGC‐1α)– dependent stimulation of mitochondrial biogenesis and function, with concomitant reduction of the glycolytic enzyme content. Conversely, when podocytes were cultured in high glucose (20 mM), stepwise oxidative phosphorylation biogenesiswas aborted, and a glycolytic switch occurred, with consecutive lactic acidosis. Expression of the master regulators of oxidative metabolism transcription factor A mitochondrial, PGC‐1α, AMPK, and serine– threonine liver kinase B1 was altered by high glucose, as well as their downstream signaling networks. Focused transcriptomics revealed that myocyte‐specific enhancer factor 2C (MEF2C) and myogenic factor 5(MYF5)expression was inhibited by high glucose levels, and endoribonuclease‐prepared small interfering RNA–mediated combined inhibition of those transcription factors phenocopied the glycolytic shift that was observed in high glucose conditions. Accordingly, a reduced expression of MEF2C, MYF5, and PGC‐1α was found in kidney tissue sections that were obtained from patients with diabetic nephropathy. These findings obtained in human samples demonstrate that MEF2C‐MYF5–dependent bioenergetic dedifferentiation occurs in podocytes that are confronted with a highglucose milieu.—Imasawa, T., Obre, E., Bellance, N., Lavie, J., Imasawa, T., Rigothier, C., Delmas, Y., Combe, C., Lacombe, D., Benard, G., Claverol, S., Bonneu, M., Rossignol, R. High glucose repatterns human podocyte energy metabolism during differentiation and diabetic nephropathy. FASEB J. 31, 294–307 (2017) www.fasebj.org

Diabetic nephropathy (DN) arises from systemic and local changes in glucose metabolism and hemodynamics. We have reported that many glycolytic and mitochondrial enzymes, such as pyruvate kinase M2 (PKM2), were elevated in renal glomeruli of DN-protected patients with type 1 and type 2 diabetes. Here, mice with PKM2 overexpression specifically in podocytes (PPKM2Tg) were generated to uncover the renal protective function of PPKM2Tg as a potential therapeutic target that prevented elevated albumin/creatinine ratio (ACR), mesangial expansion, basement membrane thickness, and podocyte foot process effacement after 7 months of streptozotocin-induced (STZ-induced) diabetes. Furthermore, diabetes-induced impairments of glycolytic rate and mitochondrial function were normalized in diabetic PPKM2Tg glomeruli, in concordance with elevated Ppargc1a and Vegf expressions. Restored VEGF expression improved glomerular maximal mitochondrial function in diabetic PPKM2Tg and WT mice. Elevated VEGF levels were observed in the glomeruli of DN-protected patients with chronic type 1 diabetes and clinically correlated with estimated glomerular filtration (GFR) — but not glycemic control. Mechanistically, the preservations of mitochondrial function and VEGF expression were dependent on tetrameric structure and enzymatic activities of PKM2 in podocytes. These findings demonstrate that PKM2 structure and enzymatic activation in podocytes can preserve the entire glomerular mitochondrial function against toxicity of hyperglycemia via paracrine factors such as VEGF and prevent DN progression.

Activation of the renin-angiotensin system is associated with podocyte injury and has been well demonstrated as a pivotal factor in the progression of chronic kidney disease. Podocyte energy metabolism is crucial for maintaining their physiological functions. However, whether renin-angiotensin system activation promotes chronic kidney disease progression by disturbing the energy metabolism of podocytes has not been elucidated. Angiotensin II, the main active molecule of the renin-angiotensin system, plays a crucial role in chronic kidney disease initiation and progression, but its impact on podocyte metabolism remains unclear. Here, we demonstrate a rapid decrease in the expression of pyruvate kinase M2, a key glycolytic enzyme, and reduced glycolytic flux in podocytes exposed to angiotensin II in vivo and in vitro. Podocyte-specific deletion of pyruvate kinase M2 in mice aggravated angiotensin II-induced glomerular and podocyte injury with foot process effacement and proteinuria. The inhibition of glycolysis was accompanied by adenosine triphosphate deficiency, cytoskeletal remodeling and podocyte apoptosis. Mechanistically, we found that angiotensin II-induced glycolysis impairment contributed to an insufficient energy supply to the foot process, leading to podocyte injury. Additionally, pyruvate kinase M2 expression was found to be reduced in podocytes from kidney biopsies of patients with hypertensive nephropathy and diabetic kidney disease. Thus, our findings suggest that glycolysis activation is a potential therapeutic strategy for podocyte injury.

The Wilms tumor-1 transcription factor regulates a repair process, providing insights on the pathogenesis of kidney disease. In the context of human disease, the mechanisms whereby transcription factors reprogram gene expression in reparative responses to injury are not well understood. We have studied the mechanisms of transcriptional reprogramming in disease using murine kidney podocytes as a model for tissue injury. Podocytes are a crucial component of glomeruli, the filtration units of each nephron. Podocyte injury is the initial event in many processes that lead to end-stage kidney disease. Wilms tumor-1 (WT1) is a master regulator of gene expression in podocytes, binding nearly all genes known to be crucial for maintenance of the glomerular filtration barrier. Using murine models and human kidney organoids, we investigated WT1-mediated transcriptional reprogramming during the course of podocyte injury. Reprogramming the transcriptome involved highly dynamic changes in the binding of WT1 to target genes during a reparative injury response, affecting chromatin state and expression levels of target genes.

Diabetic nephropathy (DN) closely relates to morphological and functional changes of podocytes, and anaerobic glycolysis represents the predominant energy source of podocytes. However, it is unknown whether lactate accumulation in chronic high glucose causes epithelial-mesenchymal transition (EMT) of podocytes through lactate-derived histone lysine lactylation (HKla). Lactate levels increased in high glucose-stimulated mouse podocyte cell line MPC and blood and the kidney of diabetic mice. High glucose or exogenous lactate decreased nephrin levels while increased collagen IV and HKla levels in MPC, but co-treatment with oxamate or dichloroacetate reduced lactate levels and alleviated the decreases in nephrin and zonula occludens- 1 levels and the increases in collagen IV and α-smooth muscle actin as well as HKla levels in high glucose-cultured MPC. However, co-treatment with rotenone diversely affected these indices. Eleven intersection genes were screened in lactate raising and lowering interventions in podocytes using RNA sequencing and four genes were validated by qPCR. Furthermore, lactate-lowering treatments attenuated renal functions, EMT, and histone lactylation in the kidney of diabetic mice. Additionally, the increased lactate might result from the upregulated monocarboxylate transporter 2 in the mitochondria and the decreased pyruvate dehydrogenase activity. Together, we reveal the role of histone lactylation in driving the EMT phenotype of podocytes in chronic high glucose state, subsequently promoting the pathological process of DN. Our study provides a reference for the study of the relationship between lactate-induced histone lactylation modification and diabetic complications.

Podocyte injury is a critical event in the pathogenesis of diabetic nephropathy (DN). Hyperglycemia, oxidative stress, inflammation, and other factors contribute to podocyte damage in DN. In this study, we demonstrate that signaling regulatory protein alpha (SIRPα) plays a pivotal role in regulating the metabolic and immune homeostasis of podocytes. Deletion of SIRPα in podocytes exacerbates, while transgenic overexpression of SIRPα alleviates, podocyte injury in experimental DN mice. Mechanistically, SIRPα downregulation promotes pyruvate kinase M2 (PKM2) phosphorylation, initiating a positive feedback loop that involves PKM2 nuclear translocation, NF-κB activation, and oxidative stress, ultimately impairing aerobic glycolysis. Consistent with this mechanism, shikonin ameliorates podocyte injury by reducing PKM2 nuclear translocation, preventing oxidative stress and NF-κB activation, thereby restoring aerobic glycolysis.

Diabetic nephropathy (DN) is the leading cause of end‐stage kidney disease. TGF‐β1/Smad3 signalling plays a major pathological role in DN; however, the contribution of Smad4 has not been examined. Smad4 depletion in the kidney using anti‐Smad4 locked nucleic acid halted progressive podocyte damage and glomerulosclerosis in mouse type 2 DN, suggesting a pathogenic role of Smad4 in podocytes. Smad4 is upregulated in human and mouse podocytes during DN. Conditional Smad4 deletion in podocytes protects mice from type 2 DN, independent of obesity. Mechanistically, hyperglycaemia induces Smad4 localization to mitochondria in podocytes, resulting in reduced glycolysis and oxidative phosphorylation and increased production of reactive oxygen species. This operates, in part, via direct binding of Smad4 to the glycolytic enzyme PKM2 and reducing the active tetrameric form of PKM2. In addition, Smad4 interacts with ATPIF1, causing a reduction in ATPIF1 degradation. In conclusion, we have discovered a mitochondrial mechanism by which Smad4 causes diabetic podocyte injury.

Hyperglycemic conditions (HG), at early stages of diabetic nephropathy (DN), cause a decrease in podocyte numbers and an aberration of their function as key cells for glomerular plasma filtration. Klotho protein was shown to overcome some negative effects of hyperglycemia. Klotho is also a coreceptor for fibroblast growth factor receptors (FGFRs), the signaling of which, together with a proper rate of glycolysis in podocytes, is needed for a proper function of the glomerular filtration barrier. Therefore, we measured levels of Klotho in renal tissue, serum, and urine shortly after DN induction. We investigated whether it influences levels of FGFRs, rates of glycolysis in podocytes, and albumin permeability. During hyperglycemia, the level of membrane-bound Klotho in renal tissue decreased, with an increase in the shedding of soluble Klotho, its higher presence in serum, and lower urinary excretion. The addition of Klotho increased FGFR levels, especially FGFR1/FGFR2, after their HG-induced decrease. Klotho also increased levels of glycolytic parameters of podocytes, and decreased podocytic and glomerular albumin permeability in HG. Thus, we found that the decrease in the urinary excretion of Klotho might be an early biomarker of DN and that Klotho administration may have several beneficial effects on renal function in DN.

Diabetic nephropathy (DN) is one of the most frequent complications of diabetes. Early stages of DN are associated with hyperinsulinemia and progressive insulin resistance in insulin-sensitive cells, including podocytes. The diabetic environment induces pathological changes, especially in podocyte bioenergetics, which is tightly linked with mitochondrial dynamics. The regulatory role of insulin in mitochondrial morphology in podocytes has not been fully elucidated. Therefore, the main goal of the present study was to investigate effects of insulin on the regulation of mitochondrial dynamics and bioenergetics in human podocytes. Biochemical analyses were performed to assess oxidative phosphorylation efficiency by measuring the oxygen consumption rate (OCR) and glycolysis by measuring the extracellular acidification rate (ECAR). mRNA and protein expression were determined by real-time polymerase chain reaction and Western blot. The intracellular mitochondrial network was visualized by MitoTracker staining. All calculations were conducted using CellProfiler software. Short-term insulin exposure exerted inhibitory effects on various parameters of oxidative respiration and adenosine triphosphate production, and glycolysis flux was elevated. After a longer time of treating cells with insulin, an increase in mitochondrial size was observed, accompanied by a reduction of expression of the mitochondrial fission markers DRP1 and FIS1 and an increase in mitophagy. Overall, we identified a previously unknown role for insulin in the regulation of oxidative respiration and glycolysis and elucidated mitochondrial dynamics in human podocytes. The present results emphasize the importance of the duration of insulin stimulation for its metabolic and molecular effects, which should be considered in clinical and experimental studies of DN.

Sestrin2 regulates cell homeostasis and is an upstream signaling molecule for several signaling pathways. Sestrin2 leads to AMP-activated protein kinase- (AMPK-) and GTPase-activating protein activity toward Rags (GATOR) 1-mediated inhibition of mammalian target of rapamycin complex 1 (mTORC1), thereby enhancing autophagy. Sestrin2 also improves mitochondrial biogenesis via AMPK/Sirt1/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) signaling pathway. Blockade of ribosomal protein synthesis and augmentation of autophagy by Sestrin2 can prevent misfolded protein accumulation and attenuate endoplasmic reticulum (ER) stress. In addition, Sestrin2 enhances P62-mediated autophagic degradation of Keap1 to release nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 release by Sestrin2 vigorously potentiates antioxidant defense in diabetic nephropathy. Impaired autophagy and mitochondrial biogenesis, severe oxidative stress, and ER stress are all deeply involved in the development and progression of diabetic nephropathy. It has been shown that Sestrin2 expression is lower in the kidney of animals and patients with diabetic nephropathy. Sestrin2 knockdown aggravated diabetic nephropathy in animal models. In contrast, upregulation of Sestrin2 enhanced autophagy, mitophagy, and mitochondrial biogenesis and suppressed oxidative stress, ER stress, and apoptosis in diabetic nephropathy. Consistently, overexpression of Sestrin2 ameliorated podocyte injury, mesangial proliferation, proteinuria, and renal fibrosis in animal models of diabetic nephropathy. By suppressing transforming growth factor beta (TGF-β)/Smad and Yes-associated protein (YAP)/transcription enhancer factor 1 (TEF1) signaling pathways in experimental models, Sestrin2 hindered epithelial-mesenchymal transition and extracellular matrix accumulation in diabetic kidneys. Moreover, modulation of the downstream molecules of Sestrin2, for instance, augmentation of AMPK or Nrf2 signaling and inhibition of mTORC1, has been protective in diabetic nephropathy. Regarding the beneficial effects of Sestrin2 on diabetic nephropathy and its interaction with several signaling molecules, it is worth targeting Sestrin2 in diabetic nephropathy.

BACKGROUND Nucleotide leukin-rich polypeptide 3 (NLRP3) inflammasome is documented as a potent target for treating metabolic diseases and inflammatory disorders. Our recent work demonstrated that inhibition of NLRP3 inflammasome activation inhibits renal inflammation and fibrosis in diabetic nephropathy. This study was to investigate the effect of NLRP3 inflammasome on podocyte injury and the underlying mechanism in diabetic nephropathy. METHODS In vivo, db/db mice were treated with MCC950, a NLRP3 inflammasome specific inhibitor. NLRP3 knockout (NKO) mice were induced to diabetes by intraperitoneal injections of streptozotocin (STZ). We assessed renal function, albuminuria, podocyte injury and glomerular lipid accumulation in diabetic mice. In vitro, apoptosis, cytoskeleton change, lipid accumulation, NF-κB p65 activation and reactive oxygen species (ROS) generation were evaluated in podocytes interfered with NLRP3 siRNA or MCC950 under high glucose (HG) conditions. In addition, the effect and mechanism of IL-1β on lipid accumulation was explored in podocytes exposed to normal glucose (NG) or HG. RESULTS MCC950 treatment improved renal function, attenuated albuminuria, mesangial expansion, podocyte loss, as well as glomerular lipid accumulation in db/db mice. The diabetes-induced podocyte loss and glomerular lipid accumulation were reversed in NLRP3 knockout mice. The increased expression of sterol regulatory element-binding protein1 (SREBP1) and SREBP2, and decreased expression of ATP-binding cassette A1 (ABCA1) in podocytes were reversed by MCC950 treatment or NLRP3 knockout in diabetic mice. In vitro, NLRP3 siRNA or MCC950 treatment markedly inhibited HG-induced apoptosis, cytoskeleton change, lipid accumulation, NF-κB p65 activation, and mitochondrial ROS production in cultured podocytes. In addition, BAY11-7082 or tempol treatment inhibited HG-induced lipid accumulation in podocytes. Moreover, exposure of IL-1β to podocytes induced lipid accumulation, NF-κB p65 activation and mitochondrial ROS generation. CONCLUSION Inhibition of NLRP3 inflammasome protects against podocyte damage through suppression of lipid accumulation in diabetic nephropathy. IL-1β/ROS/NF-κB p65 mediates diabetes-associated lipid accumulation in podocytes. The suppression of NLRP3 inflammasome activation may be an effective therapeutic approach to diabetic nephropathy.

Background and purpose: Mitophagy plays a significant role in the progression of diabetic nephropathy (DN), although the regulatory mechanisms remain unclear. Recently, accumulating evidence demonstrated that impaired mitochondrial function and mitophagy are involved in DN. Here, we are aimed to explore the role of c-Src (Src) and FUNDC1-related mitophagy in the development of DN. Methods: The db/db mice were used to establish a DN mice model. The mice accepted PP2 (Src inhibitor) treatment to study the role of Src in DN. Kidney function was measured via biochemical testing. Renal histopathology and morphometric analysis were conducted via hematoxylin-eosin (HE), periodic acid-Schiff (PAS), Masson’s staining, and transmission electron microscopy (TEM). We measured degree of apoptosis in kidney by TUNEL assay. Indices of mitophagy (LC3 and p62) were evaluated by Western blotting and immunofluorescence. Complementary in vitro assays were conducted using human podocytes subjected to high glucose in combination with PP2 treatment or FUNDC1 small interfering RNAs (siRNAs). Flow cytometry was used to detect the apoptotic cells. Mitochondrial function was evaluated by JC-1 staining. Double immunofluorescence labeling of LC3 and TOMM20 used to assess the degree of mitophagy. Results: Increased Src activation was detected in the kidneys of db/db mice, and its expression was positively correlated with mitochondrial damage, podocyte apoptosis, and renal dysfunction. Inhibition of Src activation with PP2 protected against mitochondrial damage and podocyte apoptosis. In vitro experiments in podocytes established that high glucose increased Src activation, promoting FUNDC1 phosphorylation and inhibiting mitophagy. Consistent with the mouse model, inhibiting Src activity protected podocytes against mitochondrial damage. FUNDC1 silencing negated the actions of PP2, indicating that FUNDC1-mediated mitophagy is downstream pathway of Src. Conclusion: In summary, our data indicated that Src is a culprit factor in diabetic renal damage via suppression of FUNDC1-mediated mitophagy, promoting the development of DN.

Rationale: Albuminuria is an early clinical feature in the progression of diabetic nephropathy (DN). Podocyte insulin resistance is a main cause of podocyte injury, playing crucial roles by contributing to albuminuria in early DN. G protein-coupled receptor 43 (GPR43) is a metabolite sensor modulating the cell signalling pathways to maintain metabolic homeostasis. However, the roles of GPR43 in podocyte insulin resistance and its potential mechanisms in the development of DN are unclear. Methods: The experiments were conducted by using kidney tissues from biopsied DN patients, streptozotocin (STZ) induced diabetic mice with or without global GPR43 gene knockout, diabetic rats treated with broad-spectrum oral antibiotics or fecal microbiota transplantation, and cell culture model of podocytes. Renal pathological injuries were evaluated by periodic acid-schiff staining and transmission electron microscopy. The expression of GPR43 with other podocyte insulin resistance related molecules was checked by immunofluorescent staining, real-time PCR, and Western blotting. Serum acetate level was examined by gas chromatographic analysis. The distribution of gut microbiota was measured by 16S ribosomal DNA sequencing with faeces. Results: Our results demonstrated that GPR43 expression was increased in kidney samples of DN patients, diabetic animal models, and high glucose-stimulated podocytes. Interestingly, deletion of GPR43 alleviated albuminuria and renal injury in diabetic mice. Pharmacological inhibition and knockdown of GPR43 expression in podocytes increased insulin-induced Akt phosphorylation through the restoration of adenosine 5'-monophosphate-activated protein kinase α (AMPKα) activity. This effect was associated with the suppression of AMPKα activity through post-transcriptional phosphorylation via the protein kinase C-phospholipase C (PKC-PLC) pathway. Antibiotic treatment-mediated gut microbiota depletion, and faecal microbiota transplantation from the healthy donor controls substantially improved podocyte insulin sensitivity and attenuated glomerular injury in diabetic rats accompanied by the downregulation of the GPR43 expression and a decrease in the level of serum acetate. Conclusion: These findings suggested that dysbiosis of gut microbiota-modulated GPR43 activation contributed to albuminuria in DN, which could be mediated by podocyte insulin resistance through the inhibition of AMPKα activity.

BACKGROUND Diabetic nephropathy (DN) is a serious complication of diabetes mellitus. DN is the main cause of end-stage renal disease (ESRD). SIRT6 becomes the important target of DN. Diosgenin (a monomer from Chinese herbs) is probable to bind to SIRT6. PURPOSE Based on studies presented in the literature on kidney injuries plus screening for the binding effects of the drug to Sirt6, we aimed to carry out the study to assess the effects of diosgenin involved in improving podocyte damage in the early phase of DN.. METHODS DN model was established in spontaneous diabetic db/db mice. Animal experiment was in two parts. The first part includes four groups consisting of control (Con) group, model (Mod) group, low dose of diosgenin (DL) group and high dose of diosgenin (DH) group. The second part includes four groups consisting of control group, model group, DH+OSS_128167 (OSS, inhibitor of SIRT6) group, MDL800 (agonist of SIRT6) group. MPC5 cell line was selected in cell experiment, which was mainly composed of six groups including Con group, palmitic acid (PA) group, PA+DL group, PA+DH group, PA+DH+OSS group, PA+MDL800 group. Some procedures such as transcriptomics, RT-qPCR and so on were used in the study to explore and verify the mechanism. RESULTS The abnormal changes of mesangial matrix expansion, glomerular basement membrane (GBM) thickness, foot process (FP) width, urine albumin/creatinine (UACR), DESMIN, ADRP, NEPHRIN, PODOCIN, SIRT6 in Mod group were alleviated in DH group rather than DL group in the first part of animal experiment. The effect in DH group could be reversed in DH+OSS group and the same effect was observed in MDL800 group in the second part of animal experiment. The same results were also found in cell experiment. Protein level and mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) and Angiopoietin-like-4 (ANGPTL4) were increased in PA group, which could be alleviated in DH group, MDL800 group rather than DH+OSS group. CONCLUSIONS Diosgenin could protect against podocyte injury in early phase of diabetic nephropathy by regulating SIRT6.

Background LncRNA AK044604 (regulator of insulin sensitivity and autophagy, Risa ) and autophagy-related factors Sirt1 and GSK3β play important roles in diabetic nephropathy (DN). In this study, we sought to explore the effect of Risa on Sirt1/GSK3β-induced podocyte injury. Methods Diabetic db/db mice received Risa -inhibition adeno-associated virus (AAV) via tail vein injection, and intraperitoneal injection of lithium chloride (LiCl). Blood, urine, and kidney tissue samples were collected and analyzed at different time points. Immortalized mouse podocyte cells (MPCs) were cultured and treated with Risa -inhibition lentivirus (LV), EX-527, and LiCl. MPCs were collected under different stimulations as noted. The effects of Risa on podocyte autophagy were examined by qRT-PCR, Western blotting analysis, transmission electron microscopy, Periodic Acid-Schiff staining, and immunofluorescence staining. Results Risa and activated GSK3β were overexpressed, but Sirt1 was downregulated in DN mice and high glucose-treated MPCs ( P  < 0.001, db/m vs. db/db, NG or HM vs. HG), which was correlated with poor prognosis. Risa overexpression attenuated Sirt1-mediated downstream autophagy levels and aggravated podocyte injury by inhibiting the expression of Sirt1 ( P  < 0.001, db/m vs. db/db, NG or HM vs. HG). In contrast, Risa suppression enhanced Sirt1-induced autophagy and attenuated podocyte injury, which could be abrogated by EX-527 ( P  < 0.001, db/db +  Risa -AAV vs. db/db, HG +  Risa -LV vs. HG). Furthermore, LiCl treatment could restore GSK3β-mediated autophagy of podocytes ( P  < 0.001, db/db + LiCl vs. db/db, HG + LiCl vs. HG), suggesting that Risa overexpression aggravated podocyte injury by decreasing autophagy. Conclusion Risa could inhibit autophagy by regulating the Sirt1/GSK3β axis, thereby aggravating podocyte injury in DN. Risa may serve as a therapeutic target for the treatment of DN.

Background: G-protein-coupled receptor 43 (GPR43) is a posttranscriptional regulator involved in cholesterol metabolism. This study aimed to investigate the possible roles of GPR43 activation in podocyte lipotoxicity in diabetic nephropathy (DN) and explore the potential mechanisms. Methods: The experiments were conducted by using diabetic GPR43-knockout mice and a podocyte cell culture model. Lipid deposition and free cholesterol levels in kidney tissues were measured by BODIPY staining and quantitative cholesterol assays, respectively. The protein expression of GPR43, LC3II, p62, beclin1, low-density lipoprotein receptor (LDLR) and early growth response protein 1 (EGR1) in kidney tissues and podocytes was measured by real-time PCR, immunofluorescent staining and Western blotting. Results: There were increased LDL cholesterol levels in plasma and cholesterol accumulation in the kidneys of diabetic mice. However, GPR43 gene knockout inhibited these changes. An in vitro study further demonstrated that acetate treatment induced cholesterol accumulation in high glucose-stimulated podocytes, which was correlated with increased cholesterol uptake mediated by LDLR and reduced cholesterol autophagic degradation, as characterized by the inhibition of LC3 maturation, p62 degradation and autophagosome formation. Gene knockdown or pharmacological inhibition of GPR43 prevented these effects on podocytes. Furthermore, GPR43 activation increased extracellular regulated protein kinases 1/2 (ERK1/2) activity and EGR1 expression in podocytes, which resulted in an increase in cholesterol influx and autophagy inhibition. In contrast, after GPR43 deletion, these changes in podocytes were improved, as shown by the in vivo and in vitro results. Conclusion: GPR43 activation-mediated lipotoxicity contributes to podocyte injury in DN by modulating the ERK/EGR1 pathway.

We explored the protection of mangiferin monosodium salt (MGM) on kidney injury in rats with streptozotocin (STZ)-induced diabetic nephropathy (DN) by "multiomics" analysis combined with systems pharmacology, with a specific focus on ferroptosis, inflammation, and podocyte insulin resistance (IR) signaling events in kidneys. MGM treatment afforded renoprotective effects on rats with STZ-induced DN by alleviating systemic IR-induced renal inflammation and podocyte IR. These mechanisms were correlated mainly with the MGM treatment-induced inhibition of the mitogen-activated protein kinase/nuclear factor-kappa B axis and activation of the phosphorylated insulin receptor substrate 1(Tyr608)/phosphorylated phosphatidylinositol 3-kinase/phosphorylated protein kinase B axis in the kidneys of DN rats. MGM had an ameliorative function in renal ferroptosis in rats with STZ-induced DN by upregulating mevalonate-mediated antioxidant capacities (glutathione peroxidase 4 and ferroptosis suppressor protein 1/coenzyme Q10 axis) and weakening acyl-CoA synthetase long-chain family member 4-mediated proferroptotic generation of lipid drivers in kidneys. MGM may be a promising alternative strategy for the treatment of DN.

Abstract Diabetic nephropathy (DN) is the leading cause of kidney failure, with an increasing incidence worldwide. Mitochondrial dysfunction is known to occur in DN and has been implicated in the underlying pathogenesis of disease. These complex organelles have an array of important cellular functions and involvement in signaling pathways, and understanding the intricacies of these responses in health, as well as how they are damaged in disease, is likely to highlight novel therapeutic avenues. A key cell type damaged early in DN is the podocyte, and increasing studies have focused on investigating the role of mitochondria in podocyte injury. This review will summarize what is known about podocyte mitochondrial dynamics in DN, with a particular focus on bioenergetic pathways, highlighting key studies in this field and potential opportunities to target, enhance or protect podocyte mitochondrial function in the treatment of DN.

Purpose The activation of autophagy has potential protective effect on diabetic nephropathy (DN) podocyte injury, and the AMPK/mTOR signaling pathway is an important regulatory pathway of autophagy. Emodin has been reported to effectively delay DN progression; however, the therapeutic mechanisms involved in vivo remain ambiguous. The present study aimed to elucidate the mechanism of emodin in improving renal tissue and podocyte injury in DN by regulating the AMPK/mTOR-autophagy signaling pathway. Methods All rats were divided into 4 groups: a Sham group, a Vehicle group, a low-dose emodin (LD-Emo) group (20 mg/kg/day) and a high-dose emodin (HD-Emo) group (40 mg/kg/day). The different doses of Emo and distilled water were daily administrated for 8 weeks after the induction of DN by the unilateral nephrectomy combined with intraperitoneal injections of streptozotocin (STZ). The rats' general status, blood glucose, biochemical parameters, urinary protein excretion, renal histological changes and cell apoptosis in renal tissue, as well as the key protein expressions in the AMPK/mTOR signaling pathway and apoptosis-related proteins were examined, respectively. Results Emodin ameliorated the general condition, kidney weight and urinary protein excretion of the rats, but has little influence on serum biochemical parameters and did not lower blood glucose; emodin attenuated renal fibrosis including the cell numbers, extracellular matrix rate and collagen area in glomerulus, simultaneously relieved podocyte foot process fusion, up-regulated the expression of nephrin protein and suppressed glomerular and tubular epithelial cell apoptosis. In addition, emodin can induce and enhance autophagy in podocytes including increased expression of LC3-II/I, Beclin-1, p-AMPK protein and decreased expression of p62, p-mTOR protein, as well as increased autophagosomes in podocytes. Conclusion We have demonstrated that emodin, as a natural regulator in vivo, reduced proteinuria and alleviated renal fibrosis without affecting hyperglycemia in DN rats. The potential mechanisms by which emodin exerts its renoprotective effects in vivo are through suppressing cell apoptosis and enhancing autophagy of podocytes via the AMPK/mTOR signaling pathway in the kidney.

Forkhead box M1 (FOXM1) has been reported to play a protective role against acute kidney injury by driving tubular regeneration. This study aims to probe the function of FOXM1 in diabetic nephropathy (DN) and the molecules involved. FOXM1 was poorly expressed in DN-diseased kidney tissues. A murine model of DN was established, and podocytes cells (MPC5) were treated with high-glucose (HG) for in vitro studies. FOXM1 overexpression improved kidney function and reduced pathological changes in mice, and it increased the expression of the podocyte marker Nephrin in kidney tissues. In vitro, FOXM1 increased viability and reduced pyroptosis of the HG-treated MPC5 cells, and it elevated the expression of the podocyte marker Nephrin whereas reduced the expression of pyroptosis-related NLRP3 inflammasome and cleaved caspase 1. FOXM1 bound to the promoter of sirtuin 4 (SIRT4) to induce transcriptional activation. Downregulation of SIRT4 blocked the protective roles of FOXM1 both in vivo and in vitro. Phosphorylation of nuclear factor-kappa B (NF-κB) in HG-treated cells was suppressed by FOXM1 but restored after SIRT4 inhibition. In conclusion, this study suggested that FOXM1 transcriptionally activates SIRT4 and inhibits NF-κB signaling and the NLRP3 inflammasome to alleviate kidney injury and podocyte pyroptosis in DN.

Podocyte lipid accumulation is a potential therapeutic target for diabetic nephropathy (DN). This study was aimed at clarifying the mechanism of Gandi capsule (GDC) ameliorating DN by regulating the lipid metabolism of podocytes. Network pharmacology methods were performed to screen the key molecules and potential targets of GDC for constructing the molecular‐protein interaction network of GDC and conducting signal pathway enrichment analysis. GDC was predicted to ameliorate DN through SIRT1/AMPK/HNF4A pathway. Our results showed that GDC improved renal function in db/db mice. Besides, GDC exhibited effectiveness in relieving kidney tissue damage and renal lipid accumulation in db/db mice, and same effects were present in GDC‐active ingredient baicalin. We further proved the new role of HNF4A in the lipid metabolism of DN mediated by SIRT1 and AMPK signaling pathways. The results suggested decreased expression of SIRT1 and p‐AMPKα in the kidney tissue and increased expression of HNF4A of db/db mice compared with the control group. GDC and baicalin could reverse these expression changes. Furthermore, similar expression changes were observed in the murine podocyte cell line (MPC‐5) treated with different concentrations of GDC and baicalin. Our research suggested that GDC and its active ingredient baicalin could alleviate the abnormal lipid metabolism in the kidney of db/db mice and might exert renal protection through the SIRT1/AMPK/HNF4A pathway.

Introduction Diabetic kidney disease (DKD), a major microvascular complication of diabetes mellitus, is closely associated with abnormal lipid metabolism, which contributes to secondary renal injury. The JAML/SIRT1 signaling pathway plays a critical role in regulating renal lipid metabolism during DKD progression. To investigate the molecular mechanisms underlying the therapeutic effects of Wenyang Jiedu Tongluo Formula (WYJDTLF) on lipid metabolism in DKD, we conducted an animal study using db/db mice. Methods The mice were treated with WYJDTLF for 4 weeks, and its efficacy was evaluated through assessments of liver and kidney function, lipid profiles, and renal histopathology. Renal injury was examined using Hematoxylin and Eosin (H&E), Periodic Acid-Schiff (PAS), and Masson’s trichrome staining. Podocyte damage was assessed by quantifying the expression of podocyte marker proteins (Nephrin and NPHS2) using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Additionally, the expression levels of key proteins in the JAML/SIRT1 signaling pathway were analyzed via Western blot (WB). Results The results demonstrated that WYJDTLF significantly improved liver and kidney function, reduced lipid deposition and inflammatory damage, and alleviated renal fibrosis and pathological injury. These effects were mediated through the regulation of the JAML/SIRT1 signaling pathway. Furthermore, WYJDTLF treatment upregulated the expression of Nephrin and NPHS2, indicating a protective effect on podocyte integrity. Conclusion Our team has revealed for the first time that the WYJDTLF can improve lipid metabolism abnormalities in db/db mice and alleviate diabetic kidney disease-induced renal pathological damage by inhibiting the JAML/SIRT1 signalling pathway. These findings provide a scientific basis for the potential application of WYJDTLF in the treatment of DKD.

Lipid accumulation in podocytes is a major determinant of diabetic kidney disease (DKD) and identification of potential therapeutic targets by mediating podocyte lipid metabolism has clinical importance. This study was to elucidate the role of JAML (junctional adhesion molecule-like protein) in the pathogenesis of DKD. We first confirmed the expression of JAML in podocytes and found that podocyte-specific deletion of Jaml ameliorated podocyte injury and proteinuria in two different models of diabetic mice. We further demonstrated a novel role of JAML in regulating podocyte lipid metabolism through SIRT1-mediated SREBP1 signaling. Similar results were also found in mice with adriamycin-induced nephropathy. Importantly, we observed a higher expression of JAML in glomeruli from subjects with DKD and other types of proteinuric kidney diseases, and the level of JAML was correlated with lipid accumulation and glomerular filtration rate, suggesting that JAML may be an attractive therapeutic target for proteinuric kidney disease.

Lipid deposition plays a key role in the progression of diabetic kidney disease. We previously demonstrated that resveratrol modulates the junctional adhesion molecule-like protein (JAML)/Sirtuin 1 (Sirt1) pathway involved in lipid synthesis in the kidneys of mice under high-fat diet conditions, reducing lipid deposition. However, the specific mechanisms by which resveratrol affects palmitic acid (PA)-induced lipid accumulation and metabolism in podocytes remain unclear. In this study, we used mouse podocyte cell line 5 (MPC-5) to investigate the role of the JAML/Sirt1 pathway in de novo lipid synthesis. Resveratrol attenuated the abnormal expression of key components in the JAML/Sirt1 lipid synthesis pathway induced by PA in MPC-5 podocytes. Specifically, siRNA-mediated silencing of JAML increased Sirt1 expression in PA-treated MPC-5 podocytes, downregulating sterol regulatory element-binding protein-1, carbohydrate response element-binding protein, and adipose differentiation-related protein. In contrast, JAML overexpression reversed these effects. Resveratrol attenuated the metabolic abnormalities caused by JAML overexpression, suggesting that it inhibits intracellular lipid deposition in MPC-5 podocytes by regulating the JAML/Sirt1 pathway. Our findings provide new evidence that resveratrol improves lipid deposition in the kidneys and a new treatment strategy for renal diseases associated with lipid deposition in the kidneys.

No abstract available

Heterogeneous nuclear ribonucleoprotein F (HnRNP F) is a key regulator for nucleic acid metabolism; however, whether HnRNP F expression is important in maintaining podocyte integrity is unclear. Nephroseq analysis from a registry of human kidney biopsies was performed. Age- and sex-matched podocyte-specific HnRNP F knockout (HnRNP FPOD KO) mice and control (HnRNP Ffl/fl) were studied. Podocytopathy was induced in male mice (more susceptible) either by adriamycin (ADR)- or low-dose streptozotocin treatment for 2 or 8 weeks. The mouse podocyte cell line (mPODs) was used in vitro. Nephroseq data in three human cohorts were varied greatly. Both sexes of HnRNP FPOD KO mice were fertile and appeared grossly normal. However, male 20-week-old HnRNP FPOD KO than HnRNP Ffl/fl mice had increased urinary albumin/creatinine ratio, and lower expression of podocyte markers. ADR- or diabetic- HnRNP FPOD KO (vs. HnRNP Ffl/fl) mice had more severe podocytopathy. Moreover, methyltransferase-like 14 (Mettl14) gene expression was increased in podocytes from HnRNP FPOD KO mice, further enhanced in ADR- or diabetic-treated HnRNP FPOD KO mice. Consequently, this elevated Mettl14 expression led to sirtuin1 (Sirt 1) inhibition, associated with podocyte loss. In mPODs, knock-down of HnRNP F promoted Mettl14 nuclear translocation, which was associated with podocyte dysmorphology and Sirt1 inhibition-mediated podocyte loss. This process was more severe in ADR- or high glucose- treated mPODs. Conclusion: HnRNP F deficiency in podocytes promotes podocytopathy through activation of Mettl14 expression and its nuclear translocation to inhibit Sirt1 expression, underscoring the protective role of HnRNP F against podocyte injury.

Diabetic nephropathy (DN) is becoming a research hotspot in recent years because the prevalence is high and the prognosis is poor. Lipid accumulation in podocytes induced by hyperglycemia has been shown to be a driving mechanism underlying the development of DN. However, the mechanism of lipotoxicity remains unclear. Increasing evidence shows that acetyl‐CoA carboxylase 2 (ACC2) plays a crucial role in the metabolism of fatty acid, but its effect in podocyte injury of DN is still unclear. In this study, we investigated whether ACC2 could be a therapeutic target of lipid deposition induced by hyperglycemia in the human podocytes. Our results showed that high glucose (HG) triggered significant lipid deposition with a reduced β‐oxidation rate. It also contributed to the downregulation of phosphorylated ACC2 (p‐ACC2), which is an inactive form of ACC2. Knockdown of ACC2 by sh‐RNA reduced lipid deposition induced by HG. Additionally, ACC2‐shRNA restored the expression of glucose transporter 4 (GLUT4) on the cell surface, which was downregulated in HG and normalized in the insulin signaling pathway. We verified that ACC2‐shRNA alleviated cell injury, apoptosis, and restored the cytoskeleton disturbed by HG. Mechanistically, SIRT1/PGC‐1α is close related to the insulin metabolism pathway. ACC2‐shRNA could restore the expression of SIRT1/PGC‐1α, which was downregulated in HG. Rescue experiment revealed that inhibition of SIRT1 by EX‐527 counteracted the effect of ACC2‐shRNA. Taken together, our data suggest that podocyte injury mediated by HG‐induced insulin resistance and lipotoxicity could be alleviated by ACC2 inhibition via SIRT1/PGC‐1α.

No abstract available

No abstract available

ETHNOPHARMACOLOGICAL RELEVANCE Rostellularia procumbens (L) Nees. (R. procumbens) is a classical Chinese herbal medicine that has been used for effective treatment of kidney disease for nearly a thousand years in China. Recently, significant progress has been achieved in understanding the abnormal mitochondrial structure and function from chronic kidney disease (CKD). However, the regulatory mechanisms underlying R. procumbens treatment for CKD and its association with dysfunctional mitochondrial function remain elusive. AIM OF THE STUDY To study the protective effect of N-butanol extract from R. procumbens (J-NE) on chronic glomerulonephritis (CGN) mice using a mice model and mitochondrial function-related experiments. MATERIALS AND METHODS A renal injury mouse model was developed using a single tail vein injection of adriamycin (9 mg/kg). Renal pathology was analyzed through hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM). Cell apoptosis in kidney tissues was analyzed using TUNEL staining. Protein levels were measured via immunohistochemistry (HIF-1α, FN, α-SMA, and Collagen I) and Western blot (Mn-SOD, p-Drp-S637, MFN1, MFN2, OPA1, TFAM, Nrf1, ATP6, SIRT1, and PGC-1α) analysis. LC-MS was used to analyze the presence of bioactive phytocompounds in J-NE. RESULTS The results reported that the levels of kidney injury markers (urinary protein, glomerular atrophy, and renal cell apoptosis), mitochondrial dysfunction markers (mitochondrial ultrastructure, Mn-SOD, HIF-1α, FN and α-SMA),mitochondrial dynamic imbalance markers (p-Drp-S637, MFN1, MFN2 and OPA1) and SIRT1/PGC-1α signaling pathway markers (TFAM, Nrf1, ATP6, SIRT1, and PGC-1α) were settled to a significant improvement by the oral administration of J-NE. CONCLUSIONS In conclusion, R. procumbens could be able to protect the kidneys from podocyte injury caused mitochondrial dynamics and energy metabolism dysregulation by modulating the SIRT1/PGC-1α signaling pathway.

No abstract available

No abstract available

BACKGROUND Danggui Buxue Decoction (DBD) is a formula used for treating diabetic kidney disease (DKD). However, the pharmacodynamic material basis of DBD in DKD therapy remains unclear, hindering its industrial development and innovation in drug formulations. PURPOSE Lipid metabolism disorder is a key pathological mechanism in DKD progression. This study employs lipidomics to elucidate and validate the pharmacodynamic material basis of DBD in treating DKD. METHODS Forty-eight male SD rats were used in the experiment, with 8 rats per group. The DKD model was constructed with a diet high in fat and sugar, together with intraperitoneal administration of low-dose STZ and unilateral nephrectomy. DBD was administered continuously for 10 weeks to assess its therapeutic efficacy on DKD. Lipid biomarkers in the DKD models were analyzed using lipidomics, while the transitional components in the blood of DBD-treated rats were characterized through UPLC-QE-Orbitrap MS. Potential pharmacodynamic substances were identified by correlating lipid biomarkers with active ingredients in vivo, followed by molecular docking and in vitro experiments to validate key pharmacodynamic components. RESULTS DBD significantly improved blood glucose, blood lipid levels, and renal function in DKD model rats. Lipidomics identified 37 lipid biomarkers in the DKD models, and DBD demonstrated a marked corrective effect on these biomarkers. In the therapeutically effective state, 91 blood transitional components of DBD were identified. Correlation analysis revealed 44 pharmacodynamic substances associated with DKD treatment, with ferulic acid, calycosin, astragaloside IV, and ligustilide being the key components. These substances acted by increasing the levels of SIRT1, PPARG, and ABCA1 proteins in lipid-deposited podocytes. CONCLUSION In conclusion, this study explained the scientific connotation of DBD treatment of DKD with modern scientific language from three aspects: pharmacodynamic evaluation, pharmacodynamic material basis and mechanism of action from the perspective of lipid metabolism balance for the first time, and provided an empirical basis for the modern application of traditional Chinese medicinal prescriptions.

Sirtuin is a nicotinamide adenine dinucleotide–dependent deacetylase. One of its isoforms, Sirt1, is a key molecule in glucose, lipid, and energy metabolism. The renal protective effects of Sirt1 are found in various models of renal disorders with metabolic impairment, such as diabetic nephropathy. Protective effects include the maintenance of glomerular barrier function, anti–fibrosis effects, anti–oxidative stress effects, and regulation of mitochondria function and energy metabolism. Various target molecules subject to direct deacetylation or epigenetic gene regulation have been identified as effectors of the renal protective function of sirtuin. Recently, it was demonstrated that Sirt1 expression decreases in proximal tubules before albuminuria in a mouse model of diabetic nephropathy, and that albuminuria is suppressed in proximal tubule–specific mice overexpressing Sirt1. These findings suggest that decreased Sirt1 expression in proximal tubular cells causes abnormal nicotine metabolism and reduces the supply of nicotinamide mononucleotide from renal tubules to glomeruli. This further decreases expression of Sirt1 in glomerular podocytes and increases expression of a tight junction protein, claudin-1, which results in albuminuria. Activators of the sirtuin family of proteins, including resveratrol, may be important in the development of new therapeutic strategies for treating metabolic kidney diseases, including diabetic nephropathy.

No abstract available

No abstract available

Background It is widely acknowledged that cisplatin-induced nephrotoxicity hinders its efficacy during clinical therapy. Effective pharmaceutical interventions for cisplatin-induced acute kidney injury (Cis-AKI) are currently lacking. Prior studies have implicated the chemokine CX3CL1 in the development of lipopolysaccharide-induced AKI; however, its specific role in Cis-AKI remains uncertain. This research aimed to comprehensively characterize the therapeutic impact and mechanism of CX3CL1 inhibition on Cis-AKI. Methods This study employed an in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes. Kidney pathological changes were assessed using hematoxylin–eosin (HE) and Periodic-Schiff (PAS) staining. Transcriptome changes in mouse kidney tissue post-cisplatin treatment were analyzed through RNA sequencing (RNA-seq) datasets. Evaluation parameters included the expression of inflammatory markers, intracellular free iron levels, ferroptosis-related proteins—solute carrier family 7 member 11 (SLC7A11/XCT) and glutathione peroxidase 4 (GPX4)—as well as lipid peroxidation markers and mitochondrial function proteins. Mitochondrial morphological changes were visualized through transmission electron microscopy. The impact of CX3CL1 on the glucose-regulated protein 78/eukaryotic translation initiation factor 2A/CCAAT enhancer binding protein-homologous protein (GRP78/eIF2α/CHOP) and hypoxia-inducible factor 1-alpha/heme oxygenase-1 (HIF1A/HO-1) pathways in Cis-AKI was assessed via Western Blot and Immunofluorescence experiments, both in vivo and in vitro. Results Kidney CX3CL1 levels were elevated following cisplatin injection in wild-type (WT) mice. Cisplatin-treated CX3CL1-Knockout mice exhibited reduced renal histological changes, lowered blood creatinine (Cre) and blood urea nitrogen (BUN) levels, and decreased expression of inflammatory mediators compared to cisplatin-treated WT mice. RNA-seq analysis revealed the modulation of markers associated with oxidative stress and lipid metabolism related to ferroptosis in the kidneys of mice with Cis-AKI. Both the in vivo Cis-AKI mouse model and in vitro cisplatin-treated podocytes demonstrated that CX3CL1 inhibition could mitigate ferroptosis. This effect was characterized by alleviated intracellular iron overload, malondialdehyde (MDA) content, and reactive oxygen species (ROS) production, alongside increased glutathione/glutathione disulfide ratio, superoxide dismutase (SOD), XCT, and GPX4 activity. CX3CL1 inhibition also ameliorated mitochondrial dysfunction and upregulated expression of mitochondrial biogenesis proteins-uncoupling protein (UCP), mitofusin 2 (Mfn2), and peroxisome proliferators-activated receptor γ coactivator l-alpha (PGC1α)-both in vivo and in vitro. Furthermore, CX3CL1 inhibition attenuated cisplatin-induced endoplasmic reticulum (ER) stress in podocytes. Notably, CX3CL1 inhibition reduced cisplatin-induced expression of HIF-1α and HO-1 in vivo and in vitro. Conclusion Our findings suggest that CX3CL1 inhibition exerts therapeutic effects against Cis-AKI by suppressing podocyte ferroptosis.

Cystinosis is a rare, incurable lysosomal storage disease caused by mutations in the CTNS gene encoding the cystine transporter cystinosin, which leads to lysosomal cystine accumulation in all cells of the body. Patients with cystinosis display signs of podocyte damage characterized by extensive loss of podocytes into the urine at early disease stages, glomerular proteinuria, and the development of focal segmental glomerulosclerosis (FSGS) lesions. Although standard treatment with cysteamine decreases cellular cystine levels, it neither reverses glomerular injury nor prevents the loss of podocytes. Thus, pathogenic mechanisms other than cystine accumulation are involved in podocyte dysfunction in cystinosis. We used immortalized patient-derived cystinosis, healthy, and CTNS knockdown podocytes to investigate podocyte dysfunction in cystinosis. The results were validated in our newly in-house developed fluorescent ctns−/−[Tg(fabp10a:gc-EGFP)] zebrafish larvae model. To understand impaired podocyte functionality, static and dynamic permeability assays, tracer-metabolomic analysis, flow cytometry, western blot, and chemical and dynamic redox-sensing fluorescent probes were used. In the current study, we discovered that cystinosis podocytes demonstrate increased ferroptotic cell death caused by mitochondrial reactive oxygen species (ROS)-driven membrane lipid peroxidation. Moreover, cystinosis cells present a fragmented mitochondrial network with impaired tricarboxylic acid cycle (TCA) cycle and energy metabolism. Targeting mitochondrial ROS and lipid peroxidation improved podocyte function in vitro and rescued proteinuria in vivo in cystinosis zebrafish larvae. Mitochondrial ROS contribute to podocyte injury in cystinosis by driving lipid peroxidation and ferroptosis, which in turn lead to podocyte detachment. This finding adds cystinosis to the list of podocytopathies associated with mitochondrial dysfunction. The identified mechanisms reveal new therapeutic targets and highlight lipid peroxidation as an exploitable vulnerability of cystinosis podocytes.

Abstract Podocytes, as terminally differentiated cells within the glomerulus, play a decisive role in maintaining the molecular selectivity of the glomerular filtration barrier (GFB) through structural integrity and functional homeostasis. Podocyte injury not only directly compromises GFB integrity but also serves as a central pathological mechanism underlying the progression of proteinuric nephropathy. Evidence from studies highlights an intricate link between lipid metabolism dysregulation and podocyte dysfunction: Renal ectopic lipid accumulation (ELA) disrupts intracellular homeostasis via lipotoxic effects, inducing mitochondrial oxidative stress, cytoskeletal remodeling, and inflammatory cascades. Concurrently, excessive reactive oxygen species (ROS) generation coupled with compromised antioxidant defense mechanisms establishes a self-perpetuating cycle of redox imbalance. This bidirectional crosstalk within the lipid-oxidative stress axis triggers irreversible pathological alterations. This review summarizes the effects of abnormal signals during lipid synthesis, breakdown, and metabolism on podocytes, as well as the interaction between mitochondria and podocyte dysfunction through signaling mechanisms in lipid metabolism disorders. We also sorted out the key molecular pathways involved in this axis, and the regulation of key nodes of lipid metabolism (SREBP pathway, HMGCR pathway), improvement of mitochondrial function (mitochondrial dynamics and energy metabolism), and activation of antioxidant defenses (AMPK pathway) are highly promising therapeutic targets for intervening in podocyte damage and blocking the progression of the disease.

No abstract available

Podocytes are critical for maintaining permselectivity of the glomerular filtration barrier, and podocyte injury is a major cause of proteinuria in various primary and secondary glomerulopathies. Lipid dysmetabolism and inflammatory activation are the distinctive hallmarks of podocyte injury. Lipid accumulation and lipotoxicity trigger cytoskeletal rearrangement, insulin resistance, mitochondrial oxidative stress, and inflammation. Subsequently, inflammation promotes the progression of glomerulosclerosis and renal fibrosis via multiple pathways. These data suggest that lipid dysmetabolism positively or negatively regulates inflammation during podocyte injury. In this review, we summarize recent advances in the understanding of lipid metabolism and inflammation, and highlight the potential association between lipid metabolism and podocyte inflammation.

Background: Podocytes, functionally specialized and terminally differentiated glomerular visceral epithelial cells, are critical for maintaining the structure and function of the glomerular filtration barrier. Podocyte injury is considered as the most important early event contributing to proteinuric kidney diseases such as obesity-related renal disease, diabetic kidney disease, focal segmental glomerulosclerosis, membranous nephropathy, and minimal change disease. Although considerable advances have been made in the understanding of mechanisms that trigger podocyte injury, cell-specific and effective treatments are not clinically available. Summary: Emerging evidence has indicated that the disorder of podocyte lipid metabolism is closely associated with various proteinuric kidney diseases. Excessive lipid accumulation in podocytes leads to cellular dysfunction which is defined as lipotoxicity, a phenomenon characterized by mitochondrial oxidative stress, actin cytoskeleton remodeling, insulin resistance, and inflammatory response that can eventually result in podocyte hypertrophy, detachment, and death. In this review, we summarize recent advances in the understanding of lipids in podocyte biological function and the regulatory mechanisms leading to podocyte lipid accumulation in proteinuric kidney disease. Key Messages: Targeting podocyte lipid metabolism may represent a novel therapeutic strategy for patients with proteinuric kidney disease.

ETHNOPHARMACOLOGICAL RELEVANCE Diabetic kidney disease (DKD), a prevalent microvascular complication of diabetes, is a leading cause of end-stage renal disease (ESRD). Emerging evidence implicates ferroptosis in DKD pathogenesis. Qing-Re-Xiao-Zheng-(Yi-Qi) Formula (QRXZYQF), a traditional Chinese medicine with a 30-year clinical application history, exhibits multifaceted pharmacological benefits. But its potential role in DKD has yet to be fully investigated. AIM OF THE STUDY This study investigates whether QRXZYQF alleviates podocyte injury and mitigates DKD progression by modulating ferroptosis through AMP-activated protein kinase (AMPK) pathway activation. MATERIALS AND METHODS We induced DKD in male sprague dawley (SD) rats by performing left unilateral nephrectomy followed by a single intraperitoneal injection of streptozotocin (STZ, 50 mg/kg). Rats received QRXZYQF (12/24 g/kg), metformin (100 mg/kg), and valsartan (8 mg/kg) for 16 weeks. Renal function, blood glucose, lipid profiles, 24-hour urinary protein (24 h-UTP), oxidative stress markers glutathione (GSH) and malondialdehyde (MDA), and histopathology were assessed. In vitro, high-glucose-cultured conditionally immortalized mouse podocytes (MPC-5) cells were analyzed for cell viability assays, ferroptosis markers, mitochondrial integrity, and AMPK signaling. Additionally, we used short hairpin RNA (shRNA) to suppress AMPK expression to confirm whether QRXZYQF exerts protective effects on DKD via AMPK-mediated ferroptosis signaling. RESULTS QRXZYQF improved body weight, glucose-lipid metabolism, and renal function in DKD rats, and alleviated kidney tissue pathology, renal fibrosis and mitochondrial damage. Furthermore, QRXZYQF upregulated the expression of ferroptosis-related proteins glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) while downregulating acyl CoA synthase long-chain family member 4 (ACSL4) expression, and attenuated oxidative stress. Moreover, AMPK silencing partially reversed QRXZYQF's protective effects, confirming AMPK-dependent ferroptosis inhibition. CONCLUSIONS QRXZYQF attenuates DKD progression by activating AMPK signaling, thereby suppressing podocyte ferroptosis. These findings underscore its potential as a therapeutic agent for DKD.

No abstract available

Obesity-related glomerulopathy (ORG) is an independent risk factor for chronic kidney disease and even progression to end-stage renal disease. Efforts have been undertaken to elucidate the mechanisms underlying the development of ORG and substantial advances have been made in the treatment of ORG, but relatively little is known about cell-specific changes in gene expression. To define the transcriptomic landscape at single-cell resolution, we analyzed kidney samples from four patients with ORG and three obese control subjects without kidney disease using single-cell RNA sequencing. We report for the first time that immune cells, including T cells and B cells, are decreased in ORG patients. Further analysis indicated that SPP1 was significantly up-regulated in T cells and B cells. This gene is related to inflammation and cell proliferation. Analysis of differential gene expression in glomerular cells (endothelial cells, mesangial cells, and podocytes) showed that these cell types were mainly enriched in genes related to oxidative phosphorylation, cell adhesion, thermogenesis, and inflammatory pathways (PI3K-Akt signaling, MAPK signaling). Furthermore, we found that the podocytes of ORG patients were enriched in genes related to the fluid shear stress pathway. Moreover, an evaluation of cell-cell communications revealed that there were interactions between glomerular parietal epithelial cells and other cells in ORG patients, with major interactions between parietal epithelial cells and podocytes. Altogether, our identification of molecular events, cell types, and differentially expressed genes may facilitate the development of new preventive or therapeutic approaches for ORG.

To elucidate the molecular mechanisms of the MIX (combined in proportion to the content in Astragali Radix (AR), named the MIX) repairing podocyte damage to ameliorate nephropathy. MTT assay and western blot analysis were used to evaluate the protective effects of MIX on MPC5 cells induced by Adriamycin (ADR). Screening of potential pharmacodynamic markers, relevant drugs and disease targets were conducted by using metabolomics combined with bioinformatics, and the most relevant metabolic pathways were identified by analyzing shared target and KEGG pathways. The key mechanism was subsequently validated by cell adhesion assays, western blot assays, and immunofluorescence staining. The results showed that the MIX has the capacity to repair adriamycin-induced damage in MPC5 cells, as evidenced by enhanced cell viability and synaptopodin expression. Additionally, the MIX shows promise in potentially reinstating the podocyte adhesion through the modulation of the expression of podocyte adhesion-related proteins linked to nucleotide metabolites. The MIX has the potential to beneficially affect podocyte injury by modulating the cell adhesion pathway, contributing to one of the pharmacodynamic mechanisms of AR treatment of nephrotic syndrome. This has implications for the development and utilization of AR resources and achievement the social benefit of empowering rural revitalization.

Podocyte injury plays a critical role in the pathogenesis and progression of focal and segmental glomerulosclerosis (FSGS). Transmembrane protein 30A (TMEM30A) downregulation participates in podocyte injury. This study aimed to identify the critical pathways and molecules associated with the downregulation of TMEM30A in the context of FSGS podocyte injury. In our study, we found TMEM30A and podocyte marker Synaptopodin were significantly downregulated in kidney tissues from patients with FSGS compared to those in normal controls. Using transcriptomic and metabolomic analyses, we characterized Tmem30a knockdown (KD) and normal mouse podocytes to identify differentially expressed genes and metabolites. Then, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA), and Protein-Protein Interaction (PPI) network were constructed, and the differentially expressed genes and metabolites were enriched into glycolytic pathway. Furthermore, we found the key glycolytic enzymes were downregulated in patients with FSGS, podocyte-specific Tmem30aLoxP/LoxP; NPHS2-Cre mice, and Tmem30a KD mouse podocytes. For rescue experiments, shTmem30a-resistant cDNA (resTmem30a) was created to intervene Tmem30a KD mouse podocytes. And we observed that podocyte-related molecules were downregulated in the Tmem30a KD group, along with glycolysis-related molecules, but the resTmem30a partially reversed this trend. Our findings clarified TMEM30A downregulation initiates podocyte injury by reducing glycolysis-related molecules (ALDOA, HK2, LDHA, and GAPDH) in FSGS and have implications for early diagnosis, prevention, and treatment.

No abstract available

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are a novel class of antidiabetic drugs recently approved for use in patients with chronic kidney disease (CKD) and/or heart failure (HF) due to their cardiovascular (CV) and renal protective effects, both in patients with and without type 2 diabetes mellitus (DM). SGLT2i inhibit sodium-glucose cotransporter-2 (SGLT2) in the proximal tubule, reducing renal glucose reabsorption. This mechanism induces glucosuria and natriuresis, leading to weight loss, improved glucose and systolic blood pressure control, and reduced glomerular hyperfiltration and podocyte injury. The ability of SGLT2i to slow kidney disease progression and reduce CV events may represent a significant therapeutic advance for kidney transplant (KT) recipients. However, their use is currently limited by potential adverse effects, including genital infections, urinary tract infections (UTIs), hypoglycemia, and acute kidney injury (AKI). KT recipients are particularly susceptible to infections due to immunosuppressive therapy. This study aimed to investigate the safety of dapagliflozin in diabetic KT recipients and its impact on urine metabolomics. This observational, retrospective, single-center study included 17 diabetic KT patients treated with dapagliflozin over a 12-month follow-up period. Recipients with contraindications to dapagliflozin or recurrent UTIs were excluded. Demographic, clinical, and laboratory data were collected at baseline, 1, 6, and 12 months. Complications related to SGLT2i use were monitored. Urine samples were collected from 9 patients at baseline and after dapagliflozin treatment. These samples were analyzed using a mass spectrometry-based targeted metabolite approach, covering 1019 metabolites across 39 metabolite classes. Data analysis was performed using MetaboAnalyst 6.0. Table 1 summarizes patient demographics, baseline characteristics, and drug-related adverse events. Dapagliflozin was well tolerated during the follow-up period. In our cohort, two patients (11.76%) developed UTIs requiring antibiotic therapy without complications, and two patients (11.76%) developed asymptomatic bacteriuria (ABU). One case of AKI, treated with intravenous hydration and requiring hospitalization, was reported. Urine metabolomics analysis revealed changes in metabolite levels after dapagliflozin treatment. Partial Least Squares Discriminant Analysis (PLS-DA) (Fig. 1) demonstrated a shift in metabolite patterns between pre- and post-treatment groups. Fold-change (FC) analysis and Volcano Plot identified 26 significantly altered metabolites (listed in Fig. 1). Pathway analysis revealed involvement of nine metabolic pathways: glycerophospholipid, linoleic acid, alpha-linolenic acid, glyoxylate and dicarboxylate, histidine, sphingolipid, beta-alanine, arachidonic acid metabolism, and the citrate cycle. The altered metabolites were primarily associated with lipid and energy metabolism, such as triacylglycerols (TG), acylcarnitines (C4:1, C10), phosphatidylcholines (PC O-38:6), and diacylglycerol (DG 16:1_18:2), as well as oxidative stress markers like ascorbic acid. It is known that histidine exhibits important anti-inflammatory and antioxidant effects. Linoleic acid, a fatty acid, has been associated with metabolic diseases and influences energy metabolism. Sphingolipid and arachidonic acid (AA) pathways are involved in various cellular processes, including maintaining cellular membrane integrity, and may be altered in CKD and diabetic nephropathy. Our retrospective study suggests that dapagliflozin use in diabetic KT recipients is not associated with major adverse events, supporting its potential for broader use in selected KT patients to optimize the risk-benefit ratio. The beneficial effects of SGLT2i may stem from their influence on various metabolic pathways. Metabolomics analysis indicates that SGLT2 inhibitors impact lipid and energy metabolism and oxidative stress in KT recipients, potentially improving graft and overall patient survival.

Many biological phenotypes are rooted in metabolic pathway activity rather than the concentrations of individual metabolites. Despite this, most metabolomics studies only capture steady-state metabolism - not metabolic flux. Although sophisticated metabolic flux analysis strategies have been developed, these methods are technically challenging and difficult to implement in large-cohort studies. Recently, a new boundary flux analysis (BFA) approach has emerged that captures large-scale metabolic flux phenotypes by quantifying changes in metabolite levels in the media of cultured cells. This approach is advantageous because it is relatively easy to implement yet captures complex metabolic flux phenotypes. We describe the opportunities and challenges of BFA and illustrate how it can be harnessed to investigate a wide transect of biological phenomena.

No abstract available

No abstract available

No abstract available

No abstract available

Summary: pyTFA and matTFA are the first published implementations of the original TFA paper. Specifically, they include explicit formulation of Gibbs energies and metabolite concentrations, which enables straightforward integration of metabolite concentration measurements. Motivation: High‐throughput analytic technologies provide a wealth of omics data that can be used to perform thorough analyses for a multitude of studies in the areas of Systems Biology and Biotechnology. Nevertheless, most studies are still limited to constraint‐based Flux Balance Analyses (FBA), neglecting an important physicochemical constraint: thermodynamics. Thermodynamics‐based Flux Analysis (TFA) in metabolic models enables the integration of quantitative metabolomics data to study their effects on the net‐flux directionality of reactions in the network. In addition, it allows us to estimate how far each reaction operates from thermodynamic equilibrium, which provides critical information for guiding metabolic engineering decisions. Results: We present a Python package (pyTFA) and a Matlab toolbox (matTFA) that implement TFA. We show an example of application on both a reduced and a genome‐scale model of E. coli., and demonstrate TFA and data integration through TFA reduce the feasible flux space with respect to FBA. Availability and implementation: Documented implementation of TFA framework both in Python (pyTFA) and Matlab (matTFA) are available on www.github.com/EPFL‐LCSB/. Supplementary information: Supplementary data are available at Bioinformatics online.

No abstract available

No abstract available

It is confirmed that adipose-derived stem cells (ADSCs) transplantation effectively relieves kidney fibrosis and type 2 diabetes disease in mice. Currently, exosome from urine-derived stem cells (USCs) can protect type 1 diabetes-mediated kidney injury and attenuate podocyte damage in diabetic nephropathy (DN). Exosome derived from USCs has evolved into the strategy for DN treatment, but the role of ADSCs-derived exosome (ADSCs-Exo) in DN remains unclear. The present study is aimed to investigate the therapeutic action and molecular mechanism of ADSCs-derived exosome on DN. ADSCs and exosome were authenticated by immunofluorescence and flow cytometry. Morphology and the number of exosome were evaluated by electron microscope and Nanosight Tracking Analysis (NTA), respectively. Cell apoptosis was assessed using flow cytometry. Podocyte autophagy and signaling transduction were measured by immunofluorescence and immunoblotting. Dual Luciferase Reporter assay was employed to detect the regulatory relationship between miR-486 and Smad1. ADSCs-Exo attenuated spontaneous diabetes by reducing levels of urine protein, serum creatinine (Scr), blood urea nitrogen (BUN), and podocyte apoptosis in mice. In in vitro experiment, ADSCs-Exo also reversed high glucose-induced decrease of cell viability and the increase of cell apoptosis in MPC5 cells. In terms of mechanism, ADSCs-Exo could enhance autophagy flux and reduce podocyte injury by inhibiting the activation of mTOR signaling in MPC5 and spontaneous diabetic mice. Eventually, we found that miR-486 was the key factors in ADSCs and in the process of ADSCs-Exo-mediated improvement of DN symptom in vivo and in vitro. miR-486 reduced Smad1 expression by target regulating Smad1 whose reduction could inhibit mTOR activation, leading to the increase of autophagy and the reduction of podocyte apoptosis. In conclusion, we illustrated that ADSCs-Exo vividly ameliorated DN symptom by enhancing the expression of miR-486 which led to the inhibition of Smad1/mTOR signaling pathway in podocyte. Possibly, ADSCs-Exo was used as a main therapeutic strategy for DN in future.

Podocytes, specialized epithelial cells that envelop the glomerular capillaries, play a pivotal role in maintaining renal health. The current description and quantification of features on pathology slides are limited, prompting the need for innovative solutions to comprehensively assess diverse phenotypic attributes within Whole Slide Images (WSIs). In particular, understanding the morphological characteristics of podocytes, terminally differentiated glomerular epithelial cells, is crucial for studying glomerular injury. This paper introduces the Spatial Pathomics Toolkit (SPT) and applies it to podocyte pathomics. The SPT consists of three main components: (1) instance object segmentation, enabling precise identification of podocyte nuclei; (2) pathomics feature generation, extracting a comprehensive array of quantitative features from the identified nuclei; and (3) robust statistical analyses, facilitating a comprehensive exploration of spatial relationships between morphological and spatial transcriptomics features.The SPT successfully extracted and analyzed morphological and textural features from podocyte nuclei, revealing a multitude of podocyte morphomic features through statistical analysis. Additionally, we demonstrated the SPT's ability to unravel spatial information inherent to podocyte distribution, shedding light on spatial patterns associated with glomerular injury. By disseminating the SPT, our goal is to provide the research community with a powerful and user-friendly resource that advances cellular spatial pathomics in renal pathology. The implementation and its complete source code of the toolkit are made openly accessible at https://github.com/hrlblab/spatial_pathomics.

Background: Automated podocyte foot process quantification is vital for kidney research, but the established "Automatic Morphological Analysis of Podocytes" (AMAP) method is hindered by high computational demands, a lack of a user interface, and Linux dependency. We developed AMAP-APP, a cross-platform desktop application designed to overcome these barriers. Methods: AMAP-APP optimizes efficiency by replacing intensive instance segmentation with classic image processing while retaining the original semantic segmentation model. It introduces a refined Region of Interest (ROI) algorithm to improve precision. Validation involved 365 mouse and human images (STED and confocal), benchmarking performance against the original AMAP via Pearson correlation and Two One-Sided T-tests (TOST). Results: AMAP-APP achieved a 147-fold increase in processing speed on consumer hardware. Morphometric outputs (area, perimeter, circularity, and slit diaphragm density) showed high correlation (r>0.90) and statistical equivalence (TOST P<0.05) to the original method. Additionally, the new ROI algorithm demonstrated superior accuracy compared to the original, showing reduced deviation from manual delineations. Conclusion: AMAP-APP democratizes deep learning-based podocyte morphometry. By eliminating the need for high-performance computing clusters and providing a user-friendly interface for Windows, macOS, and Linux, it enables widespread adoption in nephrology research and potential clinical diagnostics.

The aim of this study is to analyze the effect of serum metabolites on diabetic nephropathy (DN) and predict the prevalence of DN through a machine learning approach. The dataset consists of 548 patients from April 2018 to April 2019 in Second Affiliated Hospital of Dalian Medical University (SAHDMU). We select the optimal 38 features through a Least absolute shrinkage and selection operator (LASSO) regression model and a 10-fold cross-validation. We compare four machine learning algorithms, including eXtreme Gradient Boosting (XGB), random forest, decision tree and logistic regression, by AUC-ROC curves, decision curves, calibration curves. We quantify feature importance and interaction effects in the optimal predictive model by Shapley Additive exPlanations (SHAP) method. The XGB model has the best performance to screen for DN with the highest AUC value of 0.966. The XGB model also gains more clinical net benefits than others and the fitting degree is better. In addition, there are significant interactions between serum metabolites and duration of diabetes. We develop a predictive model by XGB algorithm to screen for DN. C2, C5DC, Tyr, Ser, Met, C24, C4DC, and Cys have great contribution in the model, and can possibly be biomarkers for DN.

Systematic variation is a common issue in metabolomics data analysis. Therefore, different scaling and normalization techniques are used to preprocess the data for metabolomics data analysis. Although several scaling methods are available in the literature, however, choice of scaling, transformation and/or normalization technique influence the further statistical analysis. It is challenging to choose the appropriate scaling technique for downstream analysis to get accurate results or to make a proper decision. Moreover, the existing scaling techniques are sensitive to outliers or extreme values. To fill the gap, our objective is to introduce a robust scaling approach that is not influenced by outliers as well as provides more accurate results for downstream analysis. Here, we introduced a new weighted scaling approach that is robust against outliers however, where no additional outlier detection/treatment step is needed in data preprocessing and also compared it with the conventional scaling and normalization techniques through artificial and real metabolomics datasets. We evaluated the performance of the proposed method in comparison to the other existing conventional scaling techniques using metabolomics data analysis in both the absence and presence of different percentages of outliers. Results show that in most cases, the proposed scaling technique performs better than the traditional scaling methods in both the absence and presence of outliers. The proposed method improves the further downstream metabolomics analysis. The R function of the proposed robust scaling method is available at https://github.com/nishithkumarpaul/robustScaling/blob/main/wscaling.R

Background: Determining sample sizes for metabolomic experiments is important but due to the complexity of these experiments, there are currently no standard methods for sample size estimation in metabolomics. Since pilot studies are rarely done in metabolomics, currently existing sample size estimation approaches which rely on pilot data can not be applied. Results: In this article, an analysis based approach called MetSizeR is developed to estimate sample size for metabolomic experiments even when experimental pilot data are not available. The key motivation for MetSizeR is that it considers the type of analysis the researcher intends to use for data analysis when estimating sample size. MetSizeR uses information about the data analysis technique and prior expert knowledge of the metabolomic experiment to simulate pilot data from a statistical model. Permutation based techniques are then applied to the simulated pilot data to estimate the required sample size. Conclusions: The MetSizeR methodology, and a publicly available software package which implements the approach, are illustrated through real metabolomic applications. Sample size estimates, informed by the intended statistical analysis technique, and the associated uncertainty are provided.

As metabolomics datasets are becoming larger and more complex, there is an increasing need for model-based data integration and analysis to optimally leverage these data. Dynamical models of metabolism allow for the integration of heterogeneous data and the analysis of dynamical phenotypes. Here, we review recent efforts in using dynamical metabolic models for data integration, focusing on approaches that are not restricted to steady-state measurements or that require flux distributions as inputs. Furthermore, we discuss recent advances and current challenges. We conclude that much progress has been made in various areas, such as the development of scalable simulation tools, and that, although challenges remain, dynamical modeling is a powerful tool for metabolomics data analysis that is not yet living up to its full potential.

High-throughput metabolomics investigations, when conducted in large human cohorts, represent a potentially powerful tool for elucidating the biochemical diversity and mechanisms underlying human health and disease. Large-scale metabolomics data, generated using targeted or nontargeted platforms, are increasingly more common. Appropriate statistical analysis of these complex high-dimensional data is critical for extracting meaningful results from such large-scale human metabolomics studies. Herein, we consider the main statistical analytical approaches that have been employed in human metabolomics studies. Based on the lessons learned and collective experience to date in the field, we propose a step-by-step framework for pursuing statistical analyses of human metabolomics data. We discuss the range of options and potential approaches that may be employed at each stage of data management, analysis, and interpretation, and offer guidance on analytical considerations that are important for implementing an analysis workflow. Certain pervasive analytical challenges facing human metabolomics warrant ongoing research. Addressing these challenges will allow for more standardization in the field and lead to analytical advances in metabolomics investigations with the potential to elucidate novel mechanisms underlying human health and disease.

Untargeted metabolomics based on liquid chromatography-mass spectrometry technology is quickly gaining widespread application given its ability to depict the global metabolic pattern in biological samples. However, the data is noisy and plagued by the lack of clear identity of data features measured from samples. Multiple potential matchings exist between data features and known metabolites, while the truth can only be one-to-one matches. Some existing methods attempt to reduce the matching uncertainty, but are far from being able to remove the uncertainty for most features. The existence of the uncertainty causes major difficulty in downstream functional analysis. To address these issues, we develop a novel approach for Bayesian Analysis of Untargeted Metabolomics data (BAUM) to integrate previously separate tasks into a single framework, including matching uncertainty inference, metabolite selection, and functional analysis. By incorporating the knowledge graph between variables and using relatively simple assumptions, BAUM can analyze datasets with small sample sizes. By allowing different confidence levels of feature-metabolite matching, the method is applicable to datasets in which feature identities are partially known. Simulation studies demonstrate that, compared with other existing methods, BAUM achieves better accuracy in selecting important metabolites that tend to be functionally consistent and assigning confidence scores to feature-metabolite matches. We analyze a COVID-19 metabolomics dataset and a mouse brain metabolomics dataset using BAUM. Even with a very small sample size of 16 mice per group, BAUM is robust and stable. It finds pathways that conform to existing knowledge, as well as novel pathways that are biologically plausible.

In a longitudinal metabolomics study, multiple metabolites are measured from several observations at many time points. Interest lies in reducing the dimensionality of such data and in highlighting influential metabolites which change over time. A dynamic probabilistic principal components analysis (DPPCA) model is proposed to achieve dimension reduction while appropriately modelling the correlation due to repeated measurements. This is achieved by assuming an autoregressive model for some of the model parameters. Linear mixed models are subsequently used to identify influential metabolites which change over time. The proposed model is used to analyse data from a longitudinal metabolomics animal study.

Background. Emerging technologies now allow for mass spectrometry based profiling of up to thousands of small molecule metabolites (metabolomics) in an increasing number of biosamples. While offering great promise for revealing insight into the pathogenesis of human disease, standard approaches have yet to be established for statistically analyzing increasingly complex, high-dimensional human metabolomics data in relation to clinical phenotypes including disease outcomes. To determine optimal statistical approaches for metabolomics analysis, we sought to formally compare traditional statistical as well as newer statistical learning methods across a range of metabolomics dataset types. Results. In simulated and experimental metabolomics data derived from large population-based human cohorts, we observed that with an increasing number of study subjects, univariate compared to multivariate methods resulted in a higher false discovery rate due to substantial correlations among metabolites. In scenarios wherein the number of assayed metabolites increases, as in the application of nontargeted versus targeted metabolomics measures, multivariate methods performed especially favorably across a range of statistical operating characteristics. In nontargeted metabolomics datasets that included thousands of metabolite measures, sparse multivariate models demonstrated greater selectivity and lower potential for spurious relationships. Conclusion. When the number of metabolites was similar to or exceeded the number of study subjects, as is common with nontargeted metabolomics analysis of relatively small sized cohorts, sparse multivariate models exhibited the most robust statistical power with more consistent results. These findings have important implications for the analysis of metabolomics studies of human disease.

Metabolomics is a key approach in modern functional genomics and systems biology. Due to the complexity of metabolomics data, the variety of experimental designs, and the variety of existing bioinformatics tools, providing experimenters with a simple and efficient resource to conduct comprehensive and rigorous analysis of their data is of utmost importance. In 2014, we launched the Workflow4Metabolomics (W4M, http://workflow4metabolomics.org) online infrastructure for metabolomics built on the Galaxy environment, which offers user-friendly features to build and run data analysis workflows including preprocessing, statistical analysis, and annotation steps. Here we present the new W4M 3.0 release, which contains twice as many tools as the first version, and provides two features which are, to our knowledge, unique among online resources. First, data from the four major metabolomics technologies (i.e., LC-MS, FIA-MS, GC-MS, and NMR) can be analyzed on a single platform. By using three studies in human physiology, alga evolution, and animal toxicology, we demonstrate how the 40 available tools can be easily combined to address biological issues. Second, the full analysis (including the workflow, the parameter values, the input data and output results) can be referenced with a permanent digital object identifier (DOI). Publication of data analyses is of major importance for robust and reproducible science. Furthermore, the publicly shared workflows are of high-value for e-learning and training. The Workflow4Metabolomics 3.0 e-infrastructure thus not only offers a unique online environment for analysis of data from the main metabolomics technologies, but it is also the first reference repository for metabolomics workflows.

Large Language Models (LLMs) have demonstrated remarkable capabilities on general text; however, their proficiency in specialized scientific domains that require deep, interconnected knowledge remains largely uncharacterized. Metabolomics presents unique challenges with its complex biochemical pathways, heterogeneous identifier systems, and fragmented databases. To systematically evaluate LLM capabilities in this domain, we introduce MetaBench, the first benchmark for metabolomics assessment. Curated from authoritative public resources, MetaBench evaluates five capabilities essential for metabolomics research: knowledge, understanding, grounding, reasoning, and research. Our evaluation of 25 open- and closed-source LLMs reveals distinct performance patterns across metabolomics tasks: while models perform well on text generation tasks, cross-database identifier grounding remains challenging even with retrieval augmentation. Model performance also decreases on long-tail metabolites with sparse annotations. With MetaBench, we provide essential infrastructure for developing and evaluating metabolomics AI systems, enabling systematic progress toward reliable computational tools for metabolomics research.

Motivation: Untargeted metabolomics comprehensively characterizes small molecules and elucidates activities of biochemical pathways within a biological sample. Despite computational advances, interpreting collected measurements and determining their biological role remains a challenge. Results: To interpret measurements, we present an inference-based approach, termed Probabilistic modeling for Untargeted Metabolomics Analysis (PUMA). Our approach captures measurements and known information about the sample under study in a generative model and uses stochastic sampling to compute posterior probability distributions. PUMA predicts the likelihood of pathways being active, and then derives a probabilistic annotation, which assigns chemical identities to the measurements. PUMA is validated on synthetic datasets. When applied to test cases, the resulting pathway activities are biologically meaningful and distinctly different from those obtained using statistical pathway enrichment techniques. Annotation results are in agreement to those obtained using other tools that utilize additional information in the form of spectral signatures. Importantly, PUMA annotates many additional measurements.

Carriers of two apolipoprotein L1 gene risk variants (RVs), termed G1 and G2, are at increased risk for chronic kidney disease. This study utilized induced pluripotent stem cells (iPSCs) derived from two patients homozygous for G1 and G2 to model human apolipoprotein L1 (APOL1)-mediated kidney disease (AMKD) in kidney organoids. Single-cell transcriptomic analysis and immunofluorescence imaging showed APOL1 upregulation in podocytes after interferon-gamma (IFN-γ) treatment. Transcriptomics and spatial dynamic metabolomics demonstrated a significant reduction in oxidative phosphorylation and tricarboxylic acid (TCA) cycle activity, along with upregulation of glycolysis and hypoxia signaling in RV podocytes. Isolated RV glomeruli exhibited no increase in maximal respiration rate following IFN-γ treatment, while iPSC-derived RV podocytes displayed a reduced number of mitochondrial branches and shorter branch length. This model presents early metabolic reprogramming of RV podocytes upon inflammatory injury and compelling evidence that mitochondrial dysfunction plays a pivotal role in the early pathophysiology of AMKD.

A gradual decline in renal function occurs even in healthy aging individuals. In addition to aging, per se, concurrent metabolic syndrome and hypertension, which are common in the aging population, can induce mitochondrial dysfunction and inflammation, which collectively contribute to age-related kidney dysfunction and disease. This study examined the role of the nuclear hormone receptors, the estrogen-related receptors (ERRs), in regulation of age-related mitochondrial dysfunction and inflammation. The ERRs were decreased in both aging human and mouse kidneys and were preserved in aging mice with lifelong caloric restriction (CR). A pan-ERR agonist, SLU-PP-332, was used to treat 21-month-old mice for 8 weeks. In addition, 21-month-old mice were treated with a stimulator of interferon genes (STING) inhibitor, C-176, for 3 weeks. Remarkably, similar to CR, an 8-week treatment with a pan-ERR agonist reversed the age-related increases in albuminuria, podocyte loss, mitochondrial dysfunction, and inflammatory cytokines, via the cyclic GMP-AMP synthase-STING and STAT3 signaling pathways. A 3-week treatment of 21-month-old mice with a STING inhibitor reversed the increases in inflammatory cytokines and the senescence marker, p21/cyclin dependent kinase inhibitor 1A (Cdkn1a), but also unexpectedly reversed the age-related decreases in PPARG coactivator (PGC)-1α, ERRα, mitochondrial complexes, and medium chain acyl coenzyme A dehydrogenase (MCAD) expression. These studies identified ERRs as CR mimetics and as important modulators of age-related mitochondrial dysfunction and inflammation. These findings highlight novel druggable pathways that can be further evaluated to prevent progression of age-related kidney disease.

No abstract

Metabolic pathways play a critical role in driving differentiation but remain poorly understood in the development of kidney organoids. In this study, parallel metabolite and transcriptome profiling of differentiating human pluripotent stem cells (hPSCs) to multicellular renal organoids revealed key metabolic drivers of the differentiation process. In the early stage, transitioning from hPSCs to nephron progenitor cells (NPCs), both the glutamine and the alanine-aspartate-glutamate pathways changed significantly, as detected by enrichment and pathway impact analyses. Intriguingly, hPSCs maintained their ability to generate NPCs, even when deprived of both glutamine and glutamate. Surprisingly, single cell RNA-Seq analysis detected enhanced maturation and enrichment for podocytes under glutamine-deprived conditions. Together, these findings illustrate a novel role of glutamine metabolism in regulating podocyte development.

Mammalian target of rapamycin (mTOR) signaling is involved in a variety of kidney diseases. Clinical trials administering mTOR inhibitors to patients with FSGS, a prototypic podocyte disease, led to conflicting results, ranging from remission to deterioration of kidney function. Here, we combined complex genetic titration of mTOR complex 1 (mTORC1) levels in murine glomerular disease models, pharmacologic studies, and human studies to precisely delineate the role of mTOR in FSGS. mTORC1 target genes were significantly induced in microdissected glomeruli from both patients with FSGS and a murine FSGS model. Furthermore, a mouse model with constitutive mTORC1 activation closely recapitulated human FSGS. Notably, the complete knockout of mTORC1 by induced deletion of both

Oxidative metabolism in mitochondria regulates cellular differentiation and gene expression through intermediary metabolites and reactive oxygen species. Its role in kidney development and pathogenesis is not completely understood. Here we inactivated ubiquinone-binding protein QPC, a subunit of mitochondrial complex III, in two types of kidney progenitor cells to investigate the role of mitochondrial electron transport in kidney homeostasis. Inactivation of QPC in sine oculis-related homeobox 2 (SIX2)-expressing cap mesenchyme progenitors, which give rise to podocytes and all nephron segments except collecting ducts, resulted in perinatal death from severe kidney dysplasia. This was characterized by decreased proliferation of SIX2 progenitors and their failure to differentiate into kidney epithelium. QPC inactivation in cap mesenchyme progenitors induced activating transcription factor 4-mediated nutritional stress responses and was associated with a reduction in kidney tricarboxylic acid cycle metabolites and amino acid levels, which negatively impacted purine and pyrimidine synthesis. In contrast, QPC inactivation in ureteric tree epithelial cells, which give rise to the kidney collecting system, did not inhibit ureteric differentiation, and resulted in the development of functional kidneys that were smaller in size. Thus, our data demonstrate that mitochondrial oxidative metabolism is critical for the formation of cap mesenchyme-derived nephron segments but dispensable for formation of the kidney collecting system. Hence, our studies reveal compartment-specific needs for metabolic reprogramming during kidney development.

SGLT2 inhibitors offer strong renoprotection in subjects with diabetic kidney disease (DKD). But the mechanism for such protection is not clear. Here, we report that in damaged proximal tubules of high-fat diet-fed ApoE-knockout mice, a model of non-proteinuric DKD, ATP production shifted from lipolysis to ketolysis dependent due to hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1). We further found that empagliflozin raised endogenous ketone body (KB) levels, and thus its use or treatment with 1,3-butanediol, a KB precursor, prevented decreases in renal ATP levels and organ damage in the mice. The renoprotective effect of empagliflozin was abolished by gene deletion of Hmgcs2, a rate-limiting enzyme of ketogenesis. Furthermore, KBs attenuated mTORC1-associated podocyte damage and proteinuria in diabetic db/db mice. Our findings show that SGLT2 inhibition-associated renoprotection is mediated by an elevation of KBs that in turn corrects mTORC1 hyperactivation that occurs in non-proteinuric and proteinuric DKD.

Mitochondrial dysfunction is central to the pathogenesis of podocytopathies, yet the determinants of metabolic resilience versus failure remain elusive. We investigated how distinct disruptions of mitochondrial architecture, specifically hyperfusion via OMA1 deletion versus compromised inner mitochondrial membrane (IMM) integrity via PHB2 knockdown, influence the metabolic fate and insulin responsiveness of podocytes. To this end, we analyzed conditionally immortalized mouse podocytes with genetic OMA1 deletion or inducible PHB2 knockdown and employed an integrated approach combining bioenergetic studies, quantitative proteomics, phosphoproteomics, metabolomics, and stable isotope tracing studies with

Podocytes are highly specialized epithelial cells that play a central role in maintaining integrity of the glomerular filtration barrier. Because of their complex architecture and dynamic actin-based cytoskeleton, podocytes have substantial energy requirements, which are predominantly supported by glycolysis. Insulin signaling and glucose uptake are key regulators of cytoskeletal dynamics in these cells. Recent evidence highlights the importance of lactate metabolism in maintaining podocyte metabolic homeostasis, supported by a well-developed system for controlling lactate levels. Monocarboxylate transporter 1 (MCT1), a principal mediator of lactate transport, has emerged as a critical regulator of cellular energy balance. The present study investigated the role of MCT1 in insulin-stimulated glucose metabolism and its impact on podocyte morphology and function. Our findings showed that MCT1 inhibition impaired glucose uptake and suppressed glycolytic flux. This metabolic disruption was accompanied by alterations of the localization of key insulin signaling proteins, disorganization of the actin cytoskeleton, and an increase in permeability of the podocyte layer. Interestingly, MCT1 inhibition also triggered a compensatory shift toward oxidative phosphorylation, potentially linked to an increase in mitochondrial biogenesis. These results underscore the pivotal role of MCT1 in regulating glucose metabolism and actin cytoskeleton organization in podocytes and suggest that lactate transport is essential for preserving their structure and function. Targeting MCT1 and lactate metabolism may offer a novel therapeutic strategy for glomerular diseases that are characterized by insulin resistance and metabolic dysregulation.

Inherited and acquired mitochondrial defects have been associated with podocyte dysfunction and chronic kidney disease (CKD). Peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) is one of the main transcriptional regulators of mitochondrial biogenesis and function. We hypothesized that increasing PGC1α expression in podocytes could protect from CKD. We found that PGC1α and mitochondrial transcript levels are lower in podocytes of patients and mouse models with diabetic kidney disease (DKD). To increase PGC1α expression, podocyte-specific inducible PGC1α-transgenic mice were generated by crossing nephrin-rtTA mice with tetO-Ppargc1a animals. Transgene induction resulted in albuminuria and glomerulosclerosis in a dose-dependent manner. Expression of PGC1α in podocytes increased mitochondrial biogenesis and maximal respiratory capacity. PGC1α also shifted podocytes towards fatty acid usage from their baseline glucose preference. RNA sequencing analysis indicated that PGC1α induced podocyte proliferation. Histological lesions of mice with podocyte-specific PGC1α expression resembled collapsing focal segmental glomerular sclerosis. In conclusion, decreased podocyte PGC1α expression and mitochondrial content is a consistent feature of DKD, but excessive PGC1α alters mitochondrial properties and induces podocyte proliferation and dedifferentiation, indicating that there is likely a narrow therapeutic window for PGC1α levels in podocytes.

Traditional Chinese medicine (TCM) has shown great promise in treating diabetic nephropathy (DN). However, the key targets and mechanisms underlying the therapeutic effects of the active ingredients of modified prescription Jiawei Qihuangyin (JWQHY) remain unclear. Network pharmacology analysis was employed to identify potential targets of JWQHY in DN. Protein-protein interaction (PPI) and TCM component-target networks were constructed, and KEGG pathway enrichment analysis was performed to determine key therapeutic targets and signaling pathways. Molecular docking suggested an interaction between the major active compound formononetin (FMN) and the central target silent information regulator 1 (SIRT1), which was experimentally validated using cellular thermal shift assay. SIRT1 expression in podocytes was assessed by qRT-PCR and western blotting (WB). Cell viability (CCK-8), apoptosis (flow cytometry), and proinflammatory cytokine secretion (ELISA) were measured to evaluate podocyte injury. The acetylation level of NF-κB p65 and epithelial-mesenchymal transition (EMT)-related proteins were analyzed by WB. In vivo, a DN rat model was established to assess the therapeutic efficacy of JWQHY through biochemical urine analysis, histopathological examination (HE staining), and WB detection of SIRT1, acetylated NF-κB p65, and EMT markers. Network pharmacology identified 52 potential overlapping targets of JWQHY in DN, primarily associated with the NF-κB pathway. Among these, SIRT1 was predicted and experimentally confirmed as the main target of FMN. In a high-glucose-induced podocyte injury model, FMN upregulated SIRT1 expression, promoted NF-κB p65 deacetylation, and inhibited podocyte EMT. Consistently, FMN treatment improved renal function, reduced podocyte injury, and modulated SIRT1/NF-κB signaling in DN rats. JWQHY exerts therapeutic effects in diabetic nephropathy by modulating the SIRT1/NF-κB signaling axis through its active compound formononetin, thereby inhibiting podocyte EMT. These findings provide mechanistic insight into the pharmacological basis of FMN and support its clinical potential in DN treatment.

Podocytes are integral to the maintenance of the glomerular filtration barrier. Their injury results in proteinuria and disease progression in lupus nephritis (LN). Aberrant IgG glycosylation drives podocyte injury in LN and leads to cytoskeletal rearrangement, motility changes, and decreased nephrin production. Based on these findings, we hypothesized that IgG glycosylation patterns differentiate systemic lupus erythematosus (SLE) with and without LN and that this aberrant glycosylation reprograms podocyte metabolism. IgG was isolated from 40 pediatric SLE and from 7 healthy control samples. N-glycan analysis was performed using mass spectrometry. IgG deglycosylation was performed through enzymatic treatment by Peptide N-Glycosidase F for functional studies in podocytes. Untargeted metabolomics was performed in cultured podocytes after exposure to healthy IgG, LN-derived IgG, or deglycosylated LN-IgG and analyzed by metabolite set enrichment analysis. Digital droplet polymerase chain reaction was used to evaluate urine cells and podocytes in culture for pyruvate kinase expression. The glycosylation pattern of IgG from children with LN was different from that in children with SLE without kidney involvement. Successful treatment led to normalization of IgG glycosylation. Cultured podocytes treated with LN-derived IgG had a lower rate of glycolysis compared to podocytes incubated with deglycosylated LN-IgG or IgG from healthy volunteers. Untargeted metabolomics of podocytes revealed glycolysis as the most enriched pathway in LN and identified five key metabolites (pyruvic acid, phosphoenolpyruvic acid, 2-phosoglycerate, 3 phosphoglycerate, and fructose 1,6 bisphosphate) in which their levels significantly differed among podocytes exposed to LN-derived IgG (LN-IgG) compared to healthy IgG and deglycosylated LN-IgG. This analysis also revealed clustering around a rate limiting step of glycolysis catalyzed by PKM (Pyruvate Kinase M). Urine analyses revealed elevated pyruvic acid and greater expression of pyruvate kinase in podocytes shed in urine in patients with LN compared to levels in patients with SLE without kidney involvement. Podocytes in culture had elevated PKM levels when exposed to LN-IgG compared to IgG from patients with nonrenal SLE and LN in remission. Aberrant IgG glycosylation develops in children with LN and adversely alters podocyte metabolism, rendering these cells vulnerable to injury. Successful treatment reverses IgG glycosylation to patterns comparable to those in patients with nonrenal SLE. These data lay a strong foundation for larger translational studies evaluating the potential of IgG glycosylation as a predictive and pharmacodynamic biomarker for LN. This work also supports a need for the development of approaches to control the aberrant glycosylation of self-targeting IgG in patients with LN as a mechanism to minimize podocytopathy.

Compromised glycolysis in podocytes contributes to the initiation of diabetic kidney disease (DKD). Podocyte injury is characterized by cytoskeletal remodeling and foot process fusion. Compromised glycolysis in diabetes likely leads to switch of energy supply in podocyte. However, the underlying mechanism by which disturbed energy supply in podocytes affects the cytoskeletal structure of podocytes remains unclear. Metabolomic and transcriptomic analyses were performed on the glomeruli of db/db mice to examine the catabolism of glucose, fatty, and amino acids. Ornithine catabolism was targeted in db/db and podocyte-specific pyruvate kinase M2 knockout (PKM2-podoKO) mice. In vitro, expression of ornithine decarboxylase (ODC1) was modulated to investigate the effect of ornithine catabolism on mammalian target of rapamycin (mTOR) signaling and cytoskeletal remodeling in cultured podocytes. Multi-omic analyses of the glomeruli revealed that ornithine metabolism was enhanced in db/db mice compared with that in db/m mice under compromised glycolytic conditions. Additionally, ornithine catabolism was exaggerated in podocytes of diabetic PKM2-podoKO mice compared with that in diabetic PKM2 These findings demonstrate that compromised glycolysis in podocytes under diabetic conditions enhances ornithine catabolism. The metabolites of ornithine catabolism contribute to mTOR signaling activation via Rheb and cytoskeletal remodeling in podocytes in DKD.

Diabetic nephropathy (DN) is a major cause of end-stage renal disease, and therapeutic options for preventing its progression are limited. To identify novel therapeutic strategies, we studied protective factors for DN using proteomics on glomeruli from individuals with extreme duration of diabetes (ł50 years) without DN and those with histologic signs of DN. Enzymes in the glycolytic, sorbitol, methylglyoxal and mitochondrial pathways were elevated in individuals without DN. In particular, pyruvate kinase M2 (PKM2) expression and activity were upregulated. Mechanistically, we showed that hyperglycemia and diabetes decreased PKM2 tetramer formation and activity by sulfenylation in mouse glomeruli and cultured podocytes. Pkm-knockdown immortalized mouse podocytes had higher levels of toxic glucose metabolites, mitochondrial dysfunction and apoptosis. Podocyte-specific Pkm2-knockout (KO) mice with diabetes developed worse albuminuria and glomerular pathology. Conversely, we found that pharmacological activation of PKM2 by a small-molecule PKM2 activator, TEPP-46, reversed hyperglycemia-induced elevation in toxic glucose metabolites and mitochondrial dysfunction, partially by increasing glycolytic flux and PGC-1α mRNA in cultured podocytes. In intervention studies using DBA2/J and Nos3 (eNos) KO mouse models of diabetes, TEPP-46 treatment reversed metabolic abnormalities, mitochondrial dysfunction and kidney pathology. Thus, PKM2 activation may protect against DN by increasing glucose metabolic flux, inhibiting the production of toxic glucose metabolites and inducing mitochondrial biogenesis to restore mitochondrial function.

Diabetic kidney disease (DKD) can lead to accumulation of glucose upstream metabolites due to dysfunctional glycolysis. But the effects of accumulated glycolysis metabolites on podocytes in DKD remain unknown. The present study examined the effect of dihydroxyacetone phosphate (DHAP) on high glucose induced podocyte pyroptosis. By metabolomics, levels of DHAP, GAP, glucose-6-phosphate and fructose 1, 6-bisphosphate were significantly increased in glomeruli of db/db mice. Furthermore, the expression of LDHA and PKM2 were decreased. mRNA sequencing showed upregulation of pyroptosis-related genes (Nlrp3, Casp1, etc.). Targeted metabolomics demonstrated higher level of DHAP in HG-treated podocytes. In vitro, ALDOB expression in HG-treated podocytes was significantly increased. siALDOB-transfected podocytes showed less DHAP level, mTORC1 activation, reactive oxygen species (ROS) production, and pyroptosis, while overexpression of ALDOB had opposite effects. Furthermore, GAP had no effect on mTORC1 activation, and mTORC1 inhibitor rapamycin alleviated ROS production and pyroptosis in HG-stimulated podocytes. Our findings demonstrate that DHAP represents a critical metabolic product for pyroptosis in HG-stimulated podocytes through regulation of mTORC1 pathway. In addition, the results provide evidence that podocyte injury in DKD may be treated by reducing DHAP.

Diabetic nephropathy (DN) affects approximately 30-40% of patients with type 1 (T1DM) and type 2 diabetes (T2DM). It is a major cause of end-stage renal disease (ESRD) for the developed world. Hyperglycemia and genetics are major causal factors for the initiation and progression of DN. Multiple abnormalities in glucose and mitochondrial metabolism induced by diabetes likely contribute to the severity of DN. Recent clinical studies in people with extreme duration of T1DM (> 50 years, Joslin Medalist Study) have supported the importance of endogenous protective factors to neutralize the toxic effects of hyperglycemia on renal and other vascular tissues. Using renal glomeruli from these patients (namely Medalists) with and without DN, we have shown the importance of increased glycolytic flux in decreasing the accumulation of glucose toxic metabolites, improving mitochondrial function, survival of glomerular podocytes, and reducing glomerular pathology. Activation of a key glycolytic enzyme, pyruvate kinase M2 (PKM2), resulted in the normalization of renal hemodynamics and mitochondrial and glomerular dysfunction, leading to the mitigation of glomerular pathologies in several mouse models of DN.

Glycolysis dysfunction is an important pathogenesis of podocyte injury in diabetic kidney disease (DKD). Foot process fusion of podocytes and increased albuminuria are markers of early DKD. Moreover, cytoskeletal remodeling has been found to be involved in the foot process fusion of podocytes. However, the connections between cytoskeletal remodeling and alterations of glycolysis in podocytes in DKD have not been clarified. mRNA sequencing of glomeruli obtained from db/db and db/m mice with albuminuria was performed to analyze the expression profiling of genes in glucose metabolism. Expressions of phosphofructokinase platelet type (PFKP) in the glomeruli of DKD patients were detected. Clotrimazole (CTZ) was used to explore the renal effects of PFKP inhibition in diabetic mice. Using mRNA sequencing showed that glycolysis enzyme genes were altered, characterized by upregulation of upstream genes ( These findings provide evidence that PFKP may be a potential target for podocyte injury in DN and provide a rationale for applying podocyte glycolysis enhancing agents in patients with DKD.

The cellular responses induced by mitochondrial dysfunction remain elusive. Intrigued by the lack of almost any glomerular phenotype in patients with profound renal ischemia, we comprehensively investigated the primary sources of energy of glomerular podocytes. Combining functional measurements of oxygen consumption rates, glomerular metabolite analysis, and determination of mitochondrial density of podocytes in vivo, we demonstrate that anaerobic glycolysis and fermentation of glucose to lactate represent the key energy source of podocytes. Under physiological conditions, we could detect neither a developmental nor late-onset pathological phenotype in podocytes with impaired mitochondrial biogenesis machinery, defective mitochondrial fusion-fission apparatus, or reduced mtDNA stability and transcription caused by podocyte-specific deletion of Pgc-1α, Drp1, or Tfam, respectively. Anaerobic glycolysis represents the predominant metabolic pathway of podocytes. These findings offer a strategy to therapeutically interfere with the enhanced podocyte metabolism in various progressive kidney diseases, such as diabetic nephropathy or focal segmental glomerulosclerosis (FSGS).

Lipotoxicity was recently reported in several forms of kidney disease, including focal segmental glomerulosclerosis (FSGS). Susceptibility to FSGS in African Americans is associated with the presence of genetic variants of the Apolipoprotein L1 gene (APOL1) named G1 and G2. If and how endogenous APOL1 may alter mitochondrial function by the modifying cellular lipid metabolism is unknown. Using transgenic mice expressing the APOL1 variants (G0, G1 or G2) under endogenous promoter, we show that APOL1 risk variant expression in transgenic mice does not impair kidney function at baseline. However, APOL1 G1 expression worsens proteinuria and kidney function in mice characterized by the podocyte inducible expression of nuclear factor of activated T-cells (NFAT), which we have found to cause FSGS. APOL1 G1 expression in this FSGS-model also results in increased triglyceride and cholesterol ester contents in kidney cortices, where lipid accumulation correlated with loss of renal function. In vitro, we show that the expression of endogenous APOL1 G1/G2 in human urinary podocytes is associated with increased cellular triglyceride content and is accompanied by mitochondrial dysfunction in the presence of compensatory oxidative phosphorylation (OXPHOS) complexes elevation. Our findings indicate that APOL1 risk variant expression increases the susceptibility to lipid-dependent podocyte injury, ultimately leading to mitochondrial dysfunction.

Clinicians have long been interested in understanding the molecular basis of diabetic kidney disease (DKD)and its potential treatment targets. Its pathophysiology involves protein phosphorylation, one of the most recognizable post-transcriptional modifications, that can take part in many cellular functions and control different metabolic processes. In order to recognize the molecular and protein changes of DKD kidney, this study applied Tandem liquid chromatography-mass spectrometry (LC-MS/MS) and Next-Generation Sequencing, along with Tandem Mass Tags (TMT) labeling techniques to evaluate the mRNA, protein and modified phosphorylation sites between DKD mice and model ones. Based on Gene Ontology (GO) and KEGG pathway analyses of transcriptome and proteome, The molecular changes of DKD include accumulation of extracellular matrix, abnormally activated inflammatory microenvironment, oxidative stress and lipid metabolism disorders, leading to glomerulosclerosis and tubulointerstitial fibrosis. Oxidative stress has been emphasized as an important factor in DKD and progression to ESKD, which is directly related to podocyte injury, albuminuria and renal tubulointerstitial fibrosis. A histological study of phosphorylation further revealed that kinases were crucial. Three groups of studies have found that RAS signaling pathway, RAP1 signaling pathway, AMPK signaling pathway, PPAR signaling pathway and HIF-1 signaling pathway were crucial for the pathogenesis of DKD. Through this approach, it was discovered that targeting specific molecules, proteins, kinases and critical pathways could be a promising approach for treating DKD.

Adiponectin is an adipocytokine that plays a key regulatory role in glucose and lipid metabolism in obesity. The prevalence of obesity has led to an increase in the incidence of obesity-related glomerulopathy (ORG). This study aimed to identify the protective role of adiponectin in ORG. Small-interfering RNA (siRNA) against the gene encoding adiponectin was transfected into podocytes. The oxidative stress level was determined using a fluorometric assay. Apoptosis was analyzed by flow cytometry. The expressions of podocyte markers and pyrin domain containing protein 3 (NLRP3) inflammasome-related proteins were measured by qRT-PCR, immunohistochemistry, and Western blot. Podocytes treated with palmitic acid (PA) showed downregulated expressions of podocyte markers, increased apoptosis, upregulated levels of NLRP3 inflammasome-related proteins, increased production of inflammatory cytokines (IL-18 and IL-1β), and induced activation of NF-κB as compared to the vehicle-treated controls. Decreased adiponectin expression was observed in the serum samples from high fat diet (HFD)-fed mice. Decreased podocin expression and upregulated NLRP3 expression were observed in the kidney samples from high fat diet (HFD)-fed mice. Treatment with adiponectin or the NLRP3 inflammasome inhibitor, MCC950, protected cultured podocytes against podocyte apoptosis and inflammation. Treatment with adiponectin protected mouse kidney tissues against decreased podocin expression and upregulated NLRP3 expression. The knockout of adiponectin gene by siRNA increased ROS production, resulting in the activation of NLRP3 inflammasome and the phosphorylation of NF-κB in podocytes. Pyrrolidine dithiocarbamate, an NF-κB inhibitor, prevented adiponectin from ameliorating FFA-induced podocyte injury and NLRP3 activation. Our study showed that adiponectin ameliorated PA-induced podocyte injury in vitro and HFD-induced injury in vivo via inhibiting the ROS/NF-κB/NLRP3 pathway. These data suggest the potential use of adiponectin for the prevention and treatment of ORG.

The anti-aging gene, klotho, has been identified as a multi-functional humoral factor and is implicated in multiple biological processes. However, the effects of klotho on podocyte injury in diabetic nephropathy are poorly understood. Thus, the current study aims to investigate the renoprotective effects of klotho against podocyte injury in diabetic nephropathy. We examined lipid accumulation and klotho expression in the kidneys of diabetic patients and animals. We stimulated cultured mouse podocytes with palmitate to induce lipotoxicity-mediated podocyte injury with or without recombinant klotho. Klotho level was decreased in podocytes of lipid-accumulated obese diabetic kidneys and palmitate-treated mouse podocytes. Palmitate-treated podocytes showed increased apoptosis, intracellular ROS, ER stress, inflammation, and fibrosis, and these were significantly attenuated by klotho administration. Klotho treatment restored palmitate-induced downregulation of the antioxidant molecules, Nrf2, Keap1, and SOD1. Klotho inhibited the phosphorylation of FOXO3a, promoted its nuclear translocation, and then upregulated MnSOD expression. In addition, klotho administration attenuated palmitate-induced cytoskeleton changes, decreased nephrin expression, and increased TRPC6 expression, eventually improving podocyte albumin permeability. These results suggest that klotho administration prevents palmitate-induced functional and morphological podocyte injuries, and this may indicate that klotho is a potential therapeutic agent for the treatment of podocyte injury in obese diabetic nephropathy.

Fibroblasts from patients with Tangier disease carrying ATP-binding cassette A1 (ABCA1) loss-of-function mutations are characterized by cardiolipin accumulation, a mitochondrial-specific phospholipid. Suppression of ABCA1 expression occurs in glomeruli from patients with diabetic kidney disease (DKD) and in human podocytes exposed to DKD sera collected prior to the development of DKD. We demonstrated that siRNA ABCA1 knockdown in podocytes led to reduced oxygen consumption capabilities associated with alterations in the oxidative phosphorylation (OXPHOS) complexes and with cardiolipin accumulation. Podocyte-specific deletion of Abca1 (Abca1fl/fl) rendered mice susceptible to DKD, and pharmacological induction of ABCA1 improved established DKD. This was not mediated by free cholesterol, as genetic deletion of sterol-o-acyltransferase-1 (SOAT1) in Abca1fl/fl mice was sufficient to cause free cholesterol accumulation but did not cause glomerular injury. Instead, cardiolipin mediates ABCA1-dependent susceptibility to podocyte injury, as inhibition of cardiolipin peroxidation with elamipretide improved DKD in vivo and prevented ABCA1-dependent podocyte injury in vitro and in vivo. Collectively, we describe a pathway definitively linking ABCA1 deficiency to cardiolipin-driven mitochondrial dysfunction. We demonstrated that this pathway is relevant to DKD and that ABCA1 inducers or inhibitors of cardiolipin peroxidation may each represent therapeutic strategies for the treatment of established DKD.

Transforming growth factor (TGF)-β has been associated with podocyte injury; we have examined its effect on podocyte bioenergetics. We studied transformed mouse podocytes, exposed to TGF-β1, using a label-free assay system, Seahorse XF24, which measures oxygen consumption rates (OCR) and extracellular acidification rates (ECAR). Both basal OCR and ATP generation-coupled OCR were significantly higher in podocytes exposed to 0.3-10 ng/ml of TGF-β1 for 24, 48, and 72 h. TGF-β1 (3 ng/ml) increased oxidative capacity 75%, and 96% relative to control after 48 and 72 h, respectively. ATP content was increased 19% and 30% relative to control after a 48- and 72-h exposure, respectively. Under conditions of maximal mitochondrial function, TGF-β1 increased palmitate-driven OCR by 49%. Thus, TGF-β1 increases mitochondrial oxygen consumption and ATP generation in the presence of diverse energy substrates. TGF-β1 did not increase cell number or mitochondrial DNA copy number but did increase mitochondrial membrane potential (MMP), which could explain the OCR increase. Reactive oxygen species (ROS) increased by 32% after TGF-β1 exposure for 48 h. TGF-β activated the mammalian target of rapamycin (mTOR) pathway, and rapamycin reduced the TGF-β1-stimulated increases in OCR, ECAR, ATP generation, cellular metabolic activity, and protein generation. Our data suggest that TGF-β1, acting, in part, via mTOR, increases mitochondrial MMP and OCR, resulting in increased ROS generation and that this may contribute to podocyte injury.

Adiponectin is known to take part in the regulation of energy metabolism. AdipoRon, an orally-active synthetic adiponectin agonist, binds to both adiponectin receptors (AdipoR)1/R2 and ameliorates diabetic complications. Among the lipid metabolites, the ceramide subspecies of sphingolipids have been linked to features of lipotoxicity, including inflammation, cell death, and insulin resistance. We investigated the role of AdipoRon in the prevention and development of type 2 diabetic nephropathy. AdipoRon (30 mg/kg) was mixed into the standard chow diet and provided to db/db mice (db + AdipoRon, n = 8) and age-matched male db/m mice (dm + AdipoRon, n = 8) from 17 weeks of age for 4 weeks. Control db/db (db cont, n = 8) and db/m mice (dm cont, n = 8) were fed a normal diet of mouse chow. AdipoRon-fed db/db mice showed a decreased amount of albuminuria and lipid accumulation in the kidney with no significant changes in serum adiponectin, glucose, and body weight. Restoring expression of adiponectin receptor-1 and -2 in the renal cortex was observed in db/db mice with AdipoRon administration. Consistent up-regulation of phospho-Thr AdipoRon may prevent lipotoxicity in the kidney particularly in both GECs and podocytes through an improvement in lipid metabolism, as shown by the ratio of ceramide to sphingosines, and further contribute to prevent deterioration of renal function, independent of the systemic effects of adiponectin. The reduction in oxidative stress and apoptosis by AdipoRon provides protection against renal damage, thereby ameliorating endothelial dysfunction in type 2 diabetic nephropathy.

With the increasing prevalence of obesity in adults worldwide, the incidence of obesity-related glomerulopathy (ORG) has increased yearly, becoming one of the leading causes of end-stage renal disease. Studies have demonstrated significant correlations between hyperlipidemia and impaired renal function in patients with ORG, indicating that hyperlipidemia causes damage in kidney cells. In podocytes, the endocytosis of lipids triggers an intracellular oxidative stress response that disrupts cellular integrity, resulting in proteinuria and glomerular sclerosis. However, the specific molecular mechanisms through which podocytes endocytose lipids remain unclear. Here, we demonstrated the enhanced endocytosis of lipids by podocytes from patients with ORG. This response was associated with decreased expression of phosphatase and tensin homolog (PTEN). In vitro silencing of PTEN promoted the endocytosis of low-density lipoprotein in mouse podocytes. Conversely, overexpression of PTEN inhibited the endocytosis of lipoproteins in podocytes. PTEN directly dephosphorylates and activates the actin-depolymerizing factor cofilin-1, leading to depolymerization of filamentous actin (F-actin), which is necessary for endocytosis. Notably, inhibition of PTEN resulted in the phosphorylation and inactivation of cofilin-1, leading to F-actin formation that enhanced the endocytosis of lipoproteins in podocytes. When hyperlipidemia was induced in mice with podocyte-specific deletion of PTEN, these mice recapitulated the major pathophysiological features of ORG. Thus, PTEN downregulation in podocytes may contribute to the pathogenesis of ORG.

Adiponectin exerts renoprotective effects against diabetic nephropathy (DN) by activating the AMP-activated protein kinase (AMPK)/peroxisome proliferative-activated receptor-

High fat-induced podocyte injury is one of the important factors leading to obesity related nephropathy (ORG), but the mechanism is not clear. This study aims to explore the mechanism of period circadian clock 3 (PER3) in the oxidative stress and inflammation induced by palmitic acid (PA) in podocytes. The C57BL/6J mice were fed with chow and high-fat diet for 16 weeks. The PER3 expression in kidney tissues were detected in the normal body weight group and the obesity group. The PER3 mRNA and protein expression were detected after the podocytes were induced with different concentrations (0, 50, 150 and 300 μmol/L) of PA for 48 h. The PER3 mRNA and protein expression were detected after the podocytes were induced with 150 μmol/L PA for 0, 24, 36, and 48 h. Triglyceride (TG) levels were examined in the PA group, the adenovirus (ad)-PER3+PA group, and the siRNA-PER+PA group after the podocytes were transfected by Ad-PER3 or small interfering RNA (siRNA)-PER3 for 48 h and subsequently were induced with 150 μmol/L PA for 48 h. The differential gene expression was detected using RNA sequencing (RNA-seq) after podocytes were transfected by siRNA-PER3 (siRNA-PER3 group) and siRNA-control (siRNA-control group), respectively. The mRNA levels of nephrin, podocin, podocalyxin, podoplanin, superoxide dismutase 1 (SOD1), glutathione peroxidase 1 (GPX1), catalase (CAT), and the levels of malondialdehyde (MDA), glutathione (GSH), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and interleukin-2 (IL-2) were detected after podocytes were transfected with Ad-PER3 or Ad-control for 48 h and then they were induced by 150 μmol/L PA for 48 h. The PER3 was down-regulated in the obesity group compared with the normal body weight group ( PER3 can decrease the PA-induced oxidative stress and inflammatory factor secretion via inhibiting the lipogenesis in podocytes. High fat-induced podocyte injury is one of the important factors leading to obesity related nephropathy (ORG), but the mechanism is not clear. This study aims to explore the mechanism of period circadian clock 3 (PER3) in the oxidative stress and inflammation induced by palmitic acid (PA) in podocytes. The C57BL/6J mice were fed with chow and high-fat diet for 16 weeks. The PER3 expression in kidney tissues were detected in the normal body weight group and the obesity group. The PER3 mRNA and protein expression were detected after the podocytes were induced with different concentrations (0, 50, 150 and 300 μmol/L) of PA for 48 h. The PER3 mRNA and protein expression were detected after the podocytes were induced with 150 μmol/L PA for 0, 24, 36, and 48 h. Triglyceride (TG) levels were examined in the PA group, the adenovirus (ad)-PER3+PA group, and the siRNA-PER+PA group after the podocytes were transfected by Ad-PER3 or small interfering RNA (siRNA)-PER3 for 48 h and subsequently were induced with 150 μmol/L PA for 48 h. The differential gene expression was detected using RNA sequencing (RNA-seq) after podocytes were transfected by siRNA-PER3 (siRNA-PER3 group) and siRNA-control (siRNA-control group), respectively. The mRNA levels of nephrin, podocin, podocalyxin, podoplanin, superoxide dismutase 1 (SOD1), glutathione peroxidase 1 (GPX1), catalase (CAT), and the levels of malondialdehyde (MDA), glutathione (GSH), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and interleukin-2 (IL-2) were detected after podocytes were transfected with Ad-PER3 or Ad-control for 48 h and then they were induced by 150 μmol/L PA for 48 h. The PER3 was down-regulated in the obesity group compared with the normal body weight group ( PER3 can decrease the PA-induced oxidative stress and inflammatory factor secretion via inhibiting the lipogenesis in podocytes.

Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are podocytopathies with varying clinical courses and therapeutic responses. FSGS often leads to end-stage renal disease. Consequently, their heterogeneity requires case stratification and pathophysiological elucidation. The involvement of energy metabolism in FSGS pathogenesis and stratification has not been clarified. Therefore, this study aimed to verify whether evaluating energy kinetics can be a new approach to MCD or FSGS stratification and explore the role of energy metabolism in MCD or FSGS. Cultured human podocytes were treated with sera from patients with biopsy-confirmed MCD or FSGS. Serum-treated podocytes were analyzed for apoptosis using flow cytometry, metabolomics via mass spectrometry, and real-time adenosine triphosphate (ATP) production rates using an extracellular flux analyzer. Adriamycin-induced nephropathy was induced in podocyte-specific lactate dehydrogenase (LDH) A (LDHA)-deficient and control mice. The sera from patients with FSGS significantly induced apoptosis in human podocytes compared with those from individuals with MCD. Apoptosis severity was associated with segmental obliteration and corticosteroid resistance. Metabolomic analysis revealed differences in anaerobic glycolysis and tricarboxylic acid cycle (TCA)-related metabolites in podocytes exposed to the sera of patients with MCD and FSGS. In the podocytes treated with sera from patients with FSGS, glycolytic ATP production significantly decreased in cases with high apoptosis rates. The sera from patients with FSGS suppressed LDHA activity, suppressed α-actinin 4 (ACTN4) expression, and promoted actin remodeling of podocytes. Segmental sclerosis was more prominent in podocyte-specific LDHA-deficient mice with adriamycin-induced nephropathy than in control mice. FSGS progression was associated with decreased anaerobic glycolysis in podocytes.