Quercetin ameliorates diabetic nephropathy by reducing the expressions of transforming growth factor-β1 and connective tissue growth factor in streptozotocin-induced diabetic rats.

Diabetic nephropathy (DN) is one of the main causes of end-stage renal disease. Many studies have indicated that transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF) were involved in the pathophysiological mechanisms of DN. In addition, quercetin has been suggested to attenuate DN. In this study, we aim to examine whether quercetin ameliorates renal function through an effect on the expressions of TGF-β1 and CTGF in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in Sprague-Dawley rats with a single intraperitoneal injection of STZ. The diabetic rats were then randomized to diabetic group and quercetin therapy group. At the end of the 12th week, blood glucose, body weight, kidney weight/body weight, urine albumin excretion (UAE), serum creatinine (sCr), blood urea nitrogen (BUN), and creatinine clearance (Ccr) were measured. The expressions of TGF-β1 and CTGF in the kidneys were determined using real-time PCR and Western blot method. Diabetic rats showed significant increases in blood glucose, kidney weight/body weight, UAE, sCr, BUN, and Ccr than control group. Treatment with quercetin improved these parameters except blood glucose. Compared with the control group, the expressions of TGF-β1 and CTGF were elevated in the diabetic group. The overexpressions of TGF-β1 and CTGF in the renal tissues of diabetic rats were attenuated by administration of quercetin. Our results suggest that quercetin improved renal function in rats with DN by inhibiting the overexpressions of TGF-β1 and CTGF in the kidney.