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Background and Aims The G-protein-coupled receptor 43 (GPR43) is a post-transcriptional regulator involved in cholesterol metabolism. Our previous studies demonstrated that intracellular cholesterol accumulation contributed to podocyte injury in diabetic nephropathy (DN). This study aimed to investigate possible roles of GPR43 activation in lipid nephrotoxicity in DN and to explore its potential mechanisms. Method The experiments were conducted by using diabetic GPR43 knockout mice and cell culture model of podocytes. Renal pathological changes were checked by periodic acid schiff staining, immunohistochemical staining and transmission electron microscopy (TEM). The lipid deposition and free cholesterol contents in kidney tissues were detected by Oil Red O staining, BODIPY staining, and cholesterol quantitative assay. The protein expressions of GPR43, LC3II, p62 and related molecules of LDLR pathway in kidney tissues and podocytes were detected by real-time PCR, immunofluorescent staining, and Western blotting. Results There were decreased plasma level of LDL-cholesterol and cholesterol accumulation in kidney tissues of diabetic GPR43 knockout mice. In vitro study demonstrated that acetate, a stimulator of GPR43, increased LDLR-mediated cholesterol uptake in podocytes, accompanied with reduced cholesterol autophagic degeneration, characterized by inhibited LC3 maturation, p62 degradation, and autophagosome formation. These may evoke synergistic effects attributing to cellular cholesterol accumulation in podocytes. While genetic knockdown or pharmacological inhibition of GPR43 inhibited this effect in podocytes. Furthermore, the activation of GPR43 led to the activation of ERK1/2/EGR1 pathway in podocytes, whereas blocking ERK1/2 activity or reducing EGR1 expression reversed cholesterol influx and the inhibition of autophagy mediated by GPR43 activation in podocytes. Meanwhile, deletion of the GPR43 improved autophagy and inhibited the ERK1/2-EGR1 pathway of podocyte in diabetic mice in vivo. Conclusion Activation of the GPR43 mediated lipid nephrotoxicity contributes to podocyte injury in DN, which was mainly through the activation of ERK/EGR1 pathways. These findings suggested that the GPR43 receptor could be a potential therapeutic target for the prevention of DN progression.

Background and Aims Diabetic nephropathy (DN) is the leading cause of end-stage renal disease in the developed world. Podocyte injury has been shown to be a critical cellular event in the progression of DN. Our previous studies demonstrated that platelet-derived microparticles (PMPs) mediated endothelial injury in diabetic rats. Therefore, this study aimed to investigate whether the PMPs deposit in podocytes and its potential effects on podocyte injury in DN. Method Deposition of PMPs in podocytes was checked by immunofluorescent staining and electron microscopy. Renal pathological change and ultra-microstructure were respectively checked by periodic acid-schiff staining and electron microscopy. The protein expression of inflammatory cytokines and extracellular matrix was measured by immunohistochemical staining and Western blot. Results The PMPs were found to be widely deposited in podocytes of glomeruli in diabetic patients and animal models and closely associated with progression of DN. Interestingly, aspirin treatment significantly inhibited accumulation of PMPs in glomeruli of diabetic rats, accompanied with alleviated mesangial matrix expansion, fusion of foot processes, decreased protein expression of inflammatory cytokines and extracellular matrix secretion. The in vitro study further confirmed the deposition of PMPs in podocytes. Moreover, PMPs stimulation induced phenotype transition of podocytes through decreased protein expression of podocin and increased protein expression of α-SMA and fibronectin, which was correlated with increased production of inflammatory cytokines. Conclusion Our findings for the first time demonstrated that deposition of PMPs in podocytes contributed to the development of DN.