Renoprotective effects of oleanolic acid and its possible mechanisms in rats with diabetic kidney disease

Dyslipidemia and inflammation have great roles in the development of diabetic nephropathy (DN). Oleanolic acid (OA) is a natural triterpenoid that possesses multiple pharmacological properties including anti-oxidation, anti-inflammatory and hypoglycemia. In the present study, the effects of OA on diabetic kidney disease (DKD) and its underlying mechanisms were investigated in DKD rats. Twenty-five of a total thirty-five male Sprague-Dawley (SD) rats were used to establish for Type 2 diabetes mellitus (T2DM) model by high-fat diet combined with streptozotocin (STZ). Then rats were randomly assigned into four group: control group (n = 10), T2DM group (n = 9), OA (50 mg/kg) group (n = 7), OA (100 mg/kg) group (n = 8). Rats were sacrificed at the end of 18 weeks after feeding by intraperitoneal injection of pentobarbital sodium. Body weight (BW), fasting blood glucose (FBG), kidney weight (KW), serum lipid, 24-h urinary microalbumin (UMA), serum creatinine (Scr) and uric acid (UA) were measured. Histopathological changes were observed by PAS staining and electron microscope. The expressions of nephrin, CD68, Collagen-IV, AMPK, p-AMPK, PGC-1α, TLR4, NF-κB and TGF-β1 in kidney were also detected by immunohistochemistry or western blot. OA significantly decreased the levels of FBG, kidney index (KI), serum lipid levels, 24 h UMA, Scr, UA in diabetic rats. Additionally, OA obviously attenuated renal lipid accumulation and renal structure abnormalities in diabetic rats. Furthermore, the expression levels of nephrin, p-AMPK/AMPK, PGC-1α were elevated, while CD68, Collagen-IV, TLR4, NF-κB and TGF-β1 expressions were decreased in renal tissues of OA treated diabetic rats. OA showed dose-independent. OA can alleviate renal injury in diabetic rats through improving lipid metabolism and inflammation via AMPK/PGC-1α and TLR4/NF-κB signaling pathway.