Treatment of Experimental Diabetic Nephropathy with Epigallocatechin-3-gallate in Rats

Objective To survey the therapeutic effect of epigallocatechin-3-gallate (EGCG) on the kidney lesion and its influence on renal oxidative stress and content of plasma homocysteine (Hcy) in rats with experimental diabetes. Methods 47 inbred adult SD rats served as the subjects of the study. The rat model of experimental diabetes was set up in 37 rats by a single intraperitoneal injection of 65 mg·kg~(-1) of streptozotocin for each animal. 30 diabetic rats were randomly divided into 3 groups: model group, treatment group Ⅰ and treatment group Ⅱ.10 normal rats served as normal controls. Four weeks after the induction of experimental diabetes, rats of the treatment groups Ⅰ and Ⅱ were given each an intraperitoneal injection of 2.5 (mg·kg~(-1)·d~(-1)) and 5 mg·kg~(-1)·d~(-1 ) of EGCG, respectively. Rats of the model group and normal controls were given each an intraperitoneal injection of 0.1 mol·L~(-1) citric acid buffer solution in equivalent amount q.d.. The course of treatment lasted 12 weeks. During the 12~(th) week of treatment, 24 h urine and blood from the caudal vein from each rat of the 4 groups were collected and all of the animals were then sacrificed. The content of malonyldialdehyde(MDA), the activity of superoxide dismutase(SOD) and GSH-Px in the kidney tissue as well as the plasma concentration of Hcy were determined. Results A striking increase in the ratio of the kidney weight(mg) to body weight(g), a prominent weakening of the renal anti-oxidation capability associated with enhanced oxidative stress and a significant increase in the plasma content of homocysteine were demonstrated in rats of the model group as compared with those of rats in the control group(P0.01).The amount of 24 h urine protein, the contents of blood glucose, blood lipids and serum creatinine were notably greater in rats of the model group than those in rats of the control group (P0.01). In rats of the treatment group Ⅰ and group Ⅱ , the ratio of kidney weight to body weight was smaller than that in rats of the model group(P0.05 or P0.01). The amount of 24 h urine protein, the contents of blood lipid, serum creatinine in EGCG treated rats were also lower than those in rats of the model group(P0.05 or P0.01). In contrast, the activities of SOD and GSH-Px in the kidney tissue of EGCG treated rats were significantly higher than those in rats of the model group(P(0.05)). Meanwhile, the content of MDA in the kidney tissue and that of homocysteine in the blood plasma of EGCG treated rats were remarkably lower than those in rats of the model group(P0.05). Conclusion EGCG was shown to exert a protective effect on the kidney of diabetic rats by increasing the anti-oxidation capability and decreasing the oxidative stress of the kidney as well as lowering the plasma homocysteine.