2008 Volume 20 Issue 1 Pages 11-20
Matrix metalloproteinases (MMPs) contribute to cardiovascular disease and are associated with vascular lesions in diabetes mellitus. In the present in vivo study, we investigated whether oral administration of green tea changes the mRNA expression of MMPs in diabetic rats, because green tea catechins inhibit mRNA expression and activity of MMPs in vitro. Experimental diabetes was induced in rats by a single injection of 50 mg / kg streptozotocin (STZ) into the tail vein. Diabetic rats were fed either a green tea-free diet (STZ rats) or a diet containing 5 % green tea (STZ + GT rats) for 4 weeks. Control rats are non-diabetic rats not treated with green tea. The mRNA expression of MMP-2, MN'IP-9, tissue inhibitor of metalloproteinases (TIMP) -1, TIMP-2, and TIMP-3 in rat liver and kidney was determined by real-time polymerase chain reaction. In the liver, there were no significant differences in the mRNA expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 between STZ rats and STZ + GT rats. However, TIMP-3 mRNA expression in the liver was significantly increased in STZ + GT rats compared with control and STZ rats. In the kidney, MMP-9 mRNA expression in STZ rats was significantly decreased compared with that in control rats, whereas that in STZ + GT rats recovered to levels the same as in control rats. MMP-2, TIMP-1, TIMP-2 and TIMP-3 mRNA expression in the kidney were significantly increased in STZ + GT rats compared with STZ rats. Thus, 5 % green tea treatment of STZ diabetic rats improved changes in the mRNA expression of MMPs and TIMPs in kidney tissue more efficiently than in the liver. The results of the present study suggest that the imbalance in the mRNA expression of MMPs and TIMPs in STZ diabetic rats is improved by green tea treatment.
