Protective effects of epigallocatechin gallate (EGCG) on streptozotocin-induced diabetic nephropathy in mice

There is increasing evidence suggesting that antioxidants in green tea extracts may protect kidneys on the progression of end-stage renal disease. We investigated the protective impacts of (−)-epigallocatechin 3-O-gallate (EGCG) against streptozotocin (STZ)-induced diabetic nephropathy in mice. The mice were divided into 5 groups (n = 10 per group): control (saline, i.p.), STZ (200 mg/kg, i.p.), EGCG50 (50 mg/kg, S.Q.), EGCG100 (100 mg/kg, S.Q.), and EGCG200 (200 mg/kg, S.Q.). Animals were sacrificed at scheduled times after EGCG administration and then quantitative and qualitative analysis were performed. Compared with the control group, the STZ group showed an increase in levels of blood glucose, blood urea nitrogen, creatinine and urine protein amounts with a decrease in body weight. All the above parameters were significantly reversed with EGCG treatment, especially in the EGCG100 group. After STZ injection, there was a mesangial proliferation with increased renal osteopontin accumulation and its protein expression in the glomeruli and the proximal tubules. Mice kidneys after EGCG-treatment showed a reduced expression of above parameters and relatively improved histopathological findings. These results indicated that EGCG 100 mg/kg might provide an effective protection against STZ-induced diabetic nephropathy in mice by osteopontin suppression.