Tubulointerstitial inflammation plays a key role in the pathogenesis of diabetic nephropathy (DN). Interleukin-1β (IL-1β) is the key proinflammatory cytokine associated with tubulointerstitial inflammation. The NLRP3 inflammasome regulates IL-1β activation and secretion. Reactive oxygen species (ROS) represents the main mediator of NLRP3 inflammasome activation. We previously reported that CD36, a class B scavenger receptor, mediates ROS production in DN. Here, we determined whether CD36 is involved in NLRP3 inflammasome activation and explored the underlying mechanisms. We observed that high glucose induced-NLRP3 inflammasome activation mediate IL-1β secretion, caspase-1 activation, and apoptosis in HK-2 cells. In addition, the levels of CD36, NLRP3, and IL-1β expression (protein and mRNA) were all significantly increased under high glucose conditions. CD36 knockdown resulted in decreased NLRP3 activation and IL-1β secretion. CD36 knockdown or the addition of MitoTempo significantly inhibited ROS production in HK-2 cells. CD36 overexpression enhanced NLRP3 activation, which was reduced by MitoTempo. High glucose levels induced a change in the metabolism of HK-2 cells from fatty acid oxidation (FAO) to glycolysis, which promoted mitochondrial ROS (mtROS) production after 72 h. CD36 knockdown increased the level of AMP-activated protein kinase (AMPK) activity and mitochondrial FAO, which was accompanied by the inhibition of NLRP3 and IL-1β. The in vivo experimental results indicate that an inhibition of CD36 could protect diabetic db/db mice from tubulointerstitial inflammation and tubular epithelial cell apoptosis. CD36 mediates mtROS production and NLRP3 inflammasome activation in db/db mice. CD36 inhibition upregulated the level of FAO-related enzymes and AMPK activity in db/db mice. These results suggest that NLRP3 inflammasome activation is mediated by CD36 in renal tubular epithelial cells in DN, which suppresses mitochondrial FAO and stimulates mtROS production.

Abnormal lipid metabolism in renal tubular epithelial cells contributes to renal lipid accumulation and disturbed mitochondrial bioenergetics which are important in diabetic kidney disease. Berberine, the major active constituent of Rhizoma coptidis and Cortex phellodendri, is involved in regulating glucose and lipid metabolism. The present study aimed to investigate the protective effects of berberine on lipid accumulation in tubular epithelial cells of diabetic kidney disease. We treated type 2 diabetic db/db mice with berberine (300 mg/kg) for 12 weeks. Berberine treatment improved the physical and biochemical parameters of the db/db mice compared with db/m mice. In addition, berberine decreased intracellular lipid accumulation and increased the expression of fatty acid oxidation enzymes CPT1, ACOX1 and PPAR-α in tubular epithelial cells of db/db mice. The mitochondrial morphology, mitochondrial membrane potential, cytochrome c oxidase activity, mitochondrial reactive oxygen species, and mitochondrial ATP production in db/db mice kidneys were significantly improved by berberine. Berberine intervention activated the AMPK pathway and increased the level of PGC-1α. In vitro berberine suppressed high glucose-induced lipid accumulation and reversed high glucose-induced reduction of fatty acid oxidation enzymes in HK-2 cells. Importantly, in HK-2 cells, berberine treatment blocked the change in metabolism from fatty acid oxidation to glycolysis under high glucose condition. Moreover, berberine restored high glucose-induced dysfunctional mitochondria. These data suggested that berberine alleviates diabetic renal tubulointerstitial injury through improving high glucose-induced reduction of fatty acid oxidation, alleviates lipid deposition, and protect mitochondria in tubular epithelial cells.

Purpose: The triglyceride-glucose (TyG) index is a new index of insulin resistance (IR), and its association with hyperuricemia (HUA) is unclear. The aim of this study was to investigate whether TyG is an independent risk factor for hyperuricemia (HUA) in patients with nonalcoholic fatty liver disease (NAFLD). Patients and Methods: We retrospectively analyzed 461 patients with ultrasound-confirmed NAFLD and calculated the TyG index. Multivariate logistic regression was used to analyze the relationship between the TyG index and HUA in NAFLD patients. The correlation between the TyG index and HUA was further confirmed by a restricted cubic spline. Furthermore, the stability of the association between TyG index and HUA was examined using subgroup analysis. Receiver operating characteristic (ROC) curves were constructed to evaluate the predictive value of the TyG index on HUA. Multivariate linear regression was used to analyze the linear relationship between the TyG index and serum uric acid. Results: A total of 166 HUA patients and 295 non-HUA patients were included in the study. The results of multivariate logistic regression analysis showed that after controlling the confounding risk factors, TyG was still an independent risk factor for HUA (OR = 2.00, 95% CI: 1.38 − 2.91, p < 0.001). Restricted cubic splines showed that HUA risk increased linearly with TyG across the entire TyG range. The ROC curve showed that TyG index was better than triglyceride in predicting HUA in NAFLD patients, with AUC values of 0.62 and 0.59, respectively. Multiple linear regression analysis showed that TyG index was significantly positively correlated with blood uric acid (B = 1.37, 95% CI: 0.67– 2.08, p < 0.001). Conclusion: TyG index is an independent risk factor for HUA in patients with NAFLD. The increase of the TyG index level is closely related to the occurrence and development of HUA in patients with NAFLD.

Berberine acts via multiple pathways to alleviate fibrosis in various tissues and shows renoprotective effects. However, its role and underlying mechanisms in renal fibrosis remain unclear. Herein, we aimed to investigate the protective effects and molecular mechanisms of berberine against unilateral ureteric obstruction-induced renal fibrosis. The results indicated that berberine treatment (50 mg/kg/day) markedly alleviated histopathological alterations, collagen deposition and inflammatory cell infiltration in kidney tissue and restored mouse renal function. Mechanistically, berberine intervention inhibited NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation and the levels of the inflammatory cytokine IL-1 beta in the kidneys of unilateral ureteric obstruction mice. In addition, berberine relieved unilateral ureteric obstruction-induced renal injury by activating adenosine monophosphate-activated protein kinase (AMPK) signalling and promoting fatty acid beta-oxidation. In vitro models showed that berberine treatment prevented the TGF-beta 1-induced profibrotic phenotype of hexokinase 2 (HK-2) cells, characterized by loss of an epithelial phenotype (alpha smooth muscle actin [alpha-SMA]) and acquisition of mesenchymal marker expression (E-cadherin), by restoring abnormal fatty acid beta-oxidation and upregulating the expression of the fatty acid beta-oxidation related-key enzymes or regulators (phosphorylated-AMPK, peroxisome proliferator activated receptor alpha [PPAR alpha] and carnitine palmitoyltransferase 1A [CPT1A]). Collectively, berberine alleviated renal fibrosis by inhibiting NLRP3 inflammasome activation and protected tubular epithelial cells by reversing defective fatty acid beta-oxidation. Our findings might be exploited clinically to provide a potential novel therapeutic strategy for renal fibrosis.

The mechanisms by which metabolic stress drives epigenetic dysregulation and fibrosis in chronic kidney disease (CKD) remain incompletely understood. Using quantitative histone proteomics in murine fibrosis models, we uncovered a selective increase in histone H3 lysine 27 acetylation (H3K27ac) as a conserved epigenetic feature. Unbiased metabolomics revealed citrate accumulation, nominating ATP‐citrate lyase (ACLY) as a driver of acetyl‐CoA‐dependent histone acetylation. In murine models of folic acid and unilateral ureteral obstruction, ACLY expression, acetyl‐CoA levels, and H3K27ac were increased in injured kidneys. Tubule‐specific Acly deletion reduced acetyl‐CoA, H3K27ac, and attenuated tubulointerstitial fibrosis. Chromatin accessibility profiling revealed that loss of Acly decreased accessibility at pro‐inflammatory loci, including Jak1 and Jak2 , with reduced transcriptional output. These transcriptional and epigenetic signatures were observed in human CKD samples, where higher ACLY expression correlated with worse kidney function and increased JAK1/2 expression. Notably, ACLY inhibitors, including bempedoic acid and BMS‐303141 recapitulated the antifibrotic effects of Acly deletion in vivo in mice, supporting the therapeutic repurposing of ACLY inhibitors for CKD. Together, our findings position ACLY as a key metabolic‐epigenetic checkpoint of kidney fibrosis and a promising, druggable target for halting CKD progression.

Purpose: The epithelial-mesenchymal transition (EMT) plays an important role in renal fibrosis. Defective fatty acid oxidation (FAO) is the metabolic hallmark in injured tubular epithelial cells (TECs) contributing to renal fibrogenesis. Dysregulated cytoskeleton is believed to be an important element of renal injury and its function has been linked to cell metabolism, but little is known about the influence of the cytoskeleton on FAO in TECs. Herein, we aimed to investigate the protective effects and molecular mechanisms of pharmacological stabilization of the cytoskeleton against unilateral ureteric obstruction (UUO) -induced renal tubulointerstitial fibrosis. Materials and Methods: TGF-β 1-treated primary tubular epithelial cells (PTECs) and UUO mice served as renal interstitial fibrosis (RIF) models, with or without pharmacological cytoskeleton stabilization by Bis-T-23 (TargetMol, T30479; 20 mg/kg/day intraperitoneally in vivo; 5 μM in vitro). Biomarkers, HE staining, PAS staining, Masson staining, Sirius red staining, and TUNEL assay were used to assess kidney function and apoptosis. Real-time quantitative PCR (qPCR), Western blotting and immunohistochemistry (IHC) were performed to measure mRNA and protein expression levels respectively. PTECs viability was assessed by CCK-8 assay. Bulk mRNA sequencing was used for transcriptomic analysis of cellular metabolism. FITC-phalloidin fluorescence staining was used to detect the cytoskeleton. Fluorescent co-staining was used to detect the interactions between lipid droplets (LDs) and mitochondria. Results: Pharmacological stabilization of the cytoskeleton alleviated tubulointerstitial injury, functional changes and TEC damage in UUO mouse models. Stabilization of cytoskeleton restored FAO and enhanced FAO-associated respiration impaired by UUO injury. Here, we demonstrate that cytoskeleton rearrangement is a critical regulator of mitochondrial FAO in TECs both in vitro and in vivo. We further show that this cytoskeleton-dependent regulation of FAO occurs through altered interactions between LDs and mitochondria. Conclusion: These findings indicate that cytoskeleton stabilization is required to maintain TECs metabolism and that therapeutic manipulation of cytoskeleton remodeling could protect the kidney from fibrogenesis conditions.