Therapeutic effects of epigallocatechin gallate on streptozotocin-induced diabetic nephropathy in mice.

Diabetic nephropathy is one of the most serious complications in diabetes mellitus and has been the most common cause of end-stage renal disease. Green tea extracts have antioxidant properties, and (-)-epigallocatechin 3-O-gallate (EGCG) is known to be the most abundant in green tea. Osteopontin (OPN) is a large phosphoglycoprotein adhesion molecule, and has emerged as a potentially key pathophysiologic contributor in diabetic nephropathy. We examined whether EGCG could amelliorate the development of diabetic nephropathy and its role of OPN. The mice (n=28) were divided into 3 groups. Control group (n=7) was intraperitoneal (IP) injected 0.9% saline, Streptozotocin (STZ) group (n=7) was IP injected STZ 200mg/Kg and induced diabetic nephropathy. After a 8weeks, EGCG groups (n=7/each group) were received EGCG 50mg/kg and 100mg/kg body weight by subcutaneous injection. Serum glucose, blood urea nitrogen, serum creatinine, urine volume and urine protein amounts were measured. Western blot assay of OPN was compared for the different groups. Histopathologic examination and immunohistochemical staining of mice kidney were performed. Compared with control group, STZ-group showed an increase in blood glucose, blood urea nitrogen, creatinine levels and urine protein amounts, and a decrease in body weight. All the above parameters were significantly reversed with EGCG treatment. After STZ injection, there were an diabetic glomerulosclerosis with increased renal OPN accumulation and its protein expression in the kidney cortex. EGCG-treated mice kidney showed a reduced expression of above parameters and an reserved pathologic findings. These results suggest that EGCG ameliorates STZ-induced diabetic nephropathy by OPN suppression. The potential use of EGCG in the treatment of diabetic nephropathy should be further explored