Pathogenesis Of Diabetic Cataract In Rats Induced By Streptozotocin And Preventive Effect Of Green Tea Against It

Objective:To explore the mechanism of diabetic cataract in rats induced by streptozotocin and to investigate the role of green tea in preventing diabetic cataract. Methods:Diabetic cataract was induced by streptozocin(STZ).The diabetic rats (blood glucose>16.7mmol/l) were divided into 2 groups.The 1st group include 15 rats, 1 was examined with transmissional electron microscope ,the others were stained with HE and examined with light microscopy after 10 weeks.The 2nd group include 45 rats: green tea treatment group(Tea-DM)(n=23) and untreated diabetic group(STZ-DM)(n=22).Every rat of Tea-DM group received 100 ml green tea solution ,one day.The normal and STZ-DM groups drink tap water,all rats received normal diet.Progression of lens opacification was recorded using slit lamp at regular time intervals.The levels of glutathione reductase(GR),catalase(CAT) and glutathione(GSH) were detemined spectrometically.The glycosylated hemoglobin and triglyceride(TG) were detemined from the blood of vene caudalis. Results: Morphological changes occurred markedly in diabetic cataract . Green tea treatment delayed the progression of cataracts in diabetic rats and the delay was statistically significant from the 6th to the 9th week of diabetes (about 0.5-1 grade, P<0.05 vs untreated diabetic rats). An increase in CAT and GSH was found in the lens of Green tea treated diabetic rats(P<0.05 vs untreated diabetic rats) after 12 weeks of diabetes. Moreover, an decrease in the body weight and an increase in glycosylated hemoglobin and triglyceride(TG) was found in the blood of vene caudalis of diabetic rats(P<0.05 vs normal contrast rats).Conclusions: Apoptotic of lens epithelial and the abnormal degradation of lens fibrocyte may be the morphological base of diabetic cataract. Maybe oxidative damage play an important role in diabetic cataract. Green tea can delay the progression of lens opacification only during the earlier stages . The delay may associate with the protective effect of green tea against inactivation of antioxidation enzymes.