Abstract:

To explore the mechanism of diabetic cataracts induced by streptozotocin in rats and to investigate the role of tea polyphenols(TP) in preventing diabetic cataracts. MethodsDiabetic cataracts were induced by streptozocin(STZ). The diabetic rats (blood glucose＞16.7mmol/L) were randomly divided into 3 groups: the TP-treatment group(TP-DM), the untreated diabetic group (STZ-DM) and the control group. Each rat of the TP-DM group received 100 ml TP solution per day and of the control and the STZ-DM groups received tap water besides normal diets. Some lenses were stained with HE and examined with light microscopy after 12 weeks. Progression of lens opacification was recorded using a slit lamp at regular time intervals. The levels of glutathione reductase(GR), catalase(CAT) and glutathione(GSH) were determined spectrometically. The glycosylated hemoglobin and triglyceride(TG) of the blood of the vene caudalis were determined. ResultsMorphological changes markedly occurred in diabetic cataracts. The TP 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 the untreated diabetic rats). An increase in CAT and GSH was found in the lenses of the TP treated diabetic rats (P＜0.05 vs the untreated diabetic rats) after 12 weeks of diabetes. Moreover, a decrease in body weight and an increase in glycosylated hemoglobin and triglyceride(TG) were found in the blood of the vene caudalis of the diabetic rats (P＜0.05 vs the normal control rats). Conclusions The abnormal degradation of lens fibrocytes may be the morphological base of diabetic cataracts. The oxidative damage may play an important role in diabetic cataracts. TP can delay the progression of lens opacification only during the early stages, which may be related to the protective effect of TP against inactivation of anti-oxidation enzymes.

Key words: Diabetic cataracts; Streptozocin; Tea polyphenols; Oxidative stress