Effects of grape seed proanthocyanidin extract on renal injury in type 2 diabetic rats.

Grape seed proanthocyanidin extract (GSPE) is known to be an effective natural polyphenol capable of removing free radicals in vivo. It has been reported that GSPE has biological functions including antioxidant, anti-cancer, anti-hyperglycemic, anti-radiation, and prevention and treatment of cardiovascular diseases. This study aims to investigate the effects of GSPE on renal injury in type 2 diabetic rats induced with low-dose streptozotocin and a high-carbohydrate/high-fat diet. Rats (n=12 per group) were administered GSPE at either a low (125 mg/kg · bw), medium (250 mg/kg · bw) or high (500 mg/kg · bw) dose, while control rats and diabetes mellitus group rats received no specific treatment. After 16 weeks, GSPE slightly increased body weight and decreased food consumption, water intake and urine volume in rats. Diabetic rats treated with GSPE demonstrated decreased fasting blood glucose, serum insulin, HbA1c and systolic blood pressure (P<0.05). GSPE significantly improved renal function parameters, reduced the expression of tissue inhibitor of metalloproteinase-1 and also increased the activity of matrix metalloproteinase-9. Moreover, GSPE (particularly at a dose of 500 mg/kg · bw) increased the activity of antioxidant enzymes and reduced the levels of c-reactive proteins (P<0.01) in serum and the expression of tumor necrosis factor-α, monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 (P<0.05) in the kidney. These findings suggest that GSPE ameliorates renal injury in type 2 diabetic rats through its antioxidative activity and anti-inflammatory effects.