Effects of Green Tea on Matrix Metalloproteinases in Streptozotocin-induced Diabetic Rats

Abstract

Matrix metalloproteinases (MMPs) are considered to be important for cardiovascular disease and nearly associated with the loss of renal function by diabetes mellitus. Green tea catechins inhibit mRNA expression and activity of MMPs in vitro study. We investigated in vivo study whether oral green tea administration could cause a change of MMPs in diabetic rats. Experimental diabetes was induced by single injection of 50 mg/kg streptozotocin (STZ) via the tail vein. The diabetic rats were fed on a green tea-free diet or 5% green tea-containing diet for four weeks. After four weeks, green tea ingestion significantly decreased the HbA1c level in STZ-induced diabetic rats (STZ rats). The activities of MMP-2 and MMP-9 in plasma determined by zymography significantly increased in diabetic rats compared with those of control rats, though both activities showed no change by green tea ingestion. The mRNA expression of MMP-2, MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 in rat whole kidney, was determined by RT-PCR. The mRNA expression of MMP-9 and TIMP-1 significantly decreased in diabetic rat kidney compared with control rat, but green tea ingestion in diabetic rats (STZ+GT rats) allowed both expressions to recover to control level. MMP-2 and TIMP-2 mRNA expression in STZ+GT rats significantly increased compared with control rats and STZ rats. Thus, feeding with 5% green tea-containing diet improved the impairment of MMP regulation in STZ-induced diabetic rat kidney.