Chronic inflammation plays a key role in the pathogenesis of various diseases such as diabetic nephropathy (DN). Resveratrol (RSV), a natural polyphenol, has been proven to have renoprotective effects. In this study, we used a lipopolysaccharide (LPS)induced rat glomerular mesangial cells (RMCs) model, to elucidate the renoprotective effect of RSV on sphingosine kinase 1 (SphK1)/sphingosine 1-phosphate receptor 2 (S1P2)/NF-κB activation and the expression of downstream inflammatory mediators, such as intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and fibronectin (FN) protein expression in RMCs. Methods: Cell proliferation was tested by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). The protein levels of FN, ICAM-1, iNOS, SphK1, S1P2 and NF-κB p65 in RMCs were detected by Western blot. The DNA-binding activity of NF-κB was detected by electrophoretic mobility shift assay (EMSA). SphK1 activity and S1P content were measured by using sphingosine kinase activity assay kit and ELISA assay, respectively. Results: We first found that LPS could stimulate SphK1/S1P axis activation, whereas this occurrence was significantly blocked by RSV pretreatment. RSV obviously repressed LPSinduced upregulated expression of fibronectin (FN), intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS) in RMCs. Moreover, RSV markedly reduced SphK1 activity and its protein expression, and attenuated S1P content in LPSinduced RMCs. Furthermore, RSV could block LPS-induced upregulation of NF-κB p65 and DNA-binding activity of NF-κB. And this phenomenon was notably attenuated by SphK1 inhibitor and S1P2 inhibitor. Conclusion: RSV inhibited LPS-induced RMCs' proliferation and inflammation and FN expression by SphK1/S1P2/NF-κB pathway, suggesting that RSV may be independent of its hypoglycemic effect on preventing or delaying the development of mesangial cell fibrosis.

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Purpose To explore the underlying mechanism of the anti-diabetic effect of resveratrol (RSV) on regulating glycolipid metabolism in diabetic rats induced by streptozotocin (STZ) and a high-fat diet (HFD). Methods Male Wistar rats were randomized into three groups. Two groups were fed a high-fat diet and intraperitoneally injected with STZ (35 mg/kg), with one group also treated with RSV (30 mg/kg/d), and the third, control group was fed a normal diet. After 12 weeks, blood lipid levels and fasting blood glucose (FBG) were assessed. Histopathological changes were evaluated by hematoxylin-eosin (HE) staining and periodic acid-Schiff (PAS) staining. The protein expression of hypoxia-inducible factor 1α (HIF-1α) was assessed by Western blotting and immunofluorescence, and the proteins level of 3-phosphoinositide-dependent protein kinase 1 (PDK1), phosphorylated-PDK1 (p-PDK1), phosphorylated-protein kinase B (p-AKT), glucose transporter 1 (GLUT1) and low-density lipoprotein receptor (LDLR) in the liver were analyzed by Western blotting. The mRNA levels of Hif-1α, Glut1 and Ldlr in the liver were determined by RT-qPCR. Results RSV treatment significantly reduced liver/body weight ratio (L/W, P < 0.05), FBG ( P < 0.01) and serum concentrations of total cholesterol (TC, P < 0.05), triglycerides (TG, P < 0.01) and low-density lipoprotein-cholesterol (LDL-C, P < 0.05) in diabetic rats. RSV also improved diabetic symptoms, attenuated liver steatosis and increased liver glycogen accumulation. RSV treatment significantly downregulated the proteins expression of p-PDK1 and p-AKT ( P < 0.01) and the levels of HIF-1α ( P < 0.05) and GLUT1 ( P < 0.01), while significantly upregulating the level of LDLR ( P < 0.05). Conclusion RSV was effective in improving glycolipid metabolism in diabetic rats, probably by inhibiting the PDK1/AKT/HIF-1α pathway and regulation of its downstream target levels. These findings may provide new insight into the mechanism of action of RSV in the treatment of diabetes.