Green Tea Prevents Hyperglycemia-Induced Retinal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Rats

Purpose: Our objective was to investigate the effect of green tea (GT) on diabetes-induced retinal oxidative stress and proinflammatory parameters in rats. Methods: Treatment (200 mg/kg body weight) was carried out for a period of 16 weeks in streptozotocin-induced diabetic rats and was evaluated for hypoglycemic, antioxidant [reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT)] and anti-inflammatory [tumor necrosis factor (TNF) alpha, vascular endothelial growth factor (VEGF)] activity. Histological changes were evaluated by transmission electron microscopy. Results: Retinal GSH levels were 1.5-fold lower in diabetic rats as compared to normal rats (p < 0.05). However, in GT-treated rats, retinal GSH levels were restored close to those of the normal group. The antioxidant enzymes SOD and CAT showed a more than 2-fold decrease in activity in diabetic retinae as compared to normal retinae (p < 0.05). Both SOD and CAT enzymatic activities were restored close to normal in the GT-treated group. Expression of proinflammatory parameters (TNF-alpha and VEGF) was significantly inhibited in GT-treated retinae as compared to diabetic retinae (p < 0.05). Moreover, GT treatment prevented retinal capillary basement membrane thickness. Conclusion: The beneficial effects of GT suggest its potential role in the prevention and treatment of diabetic retinopathy in human subjects. Copyright (C) 2011 S. Karger AG, Basel