Effect of iridoid glucoside on streptozotocin induced diabetic rats and its role in regulating carbohydrate metabolic enzymes

Vitex negundo is a medicinal plant used to treat many ailments. An active compound of iridoid glucoside was isolated from V. negundo leaves and its efficacy was investigated in streptozotocin induced diabetic rats with special reference to carbohydrate metabolizing enzymes. The optimum dose of iridoid glucoside was determined by oral glucose tolerance test. The effects of iridoid glucoside were compared with glibenclamide Administration of iridoid glucoside (50 mg/kg body weight) to diabetic rats for 30 days resulted in significant reduction in the levels of plasma glucose, glycosylated hemoglobin and increase in the levels of insulin and hemoglobin. Administration of iridoid glucoside showed a significant increase in the levels of glycolytic enzymes and glycogen content and decrease in the levels of gluconeogenic enzymes in the liver of diabetic treated rats. Further, iridoid glucoside showed antihyperlipidemic activity as evidenced by significant reduction in serum total cholesterol, triglyceride, low density lipoprotein and very low density lipoprotein coupled together with elevation of high density lipoprotein in diabetic rats. A significant decrease was observed in the activities of aspartate aminotransferase, alanine aminotransferase and decrease in the levels of serum urea and creatinine in diabetic treated rats when compared to diabetic untreated rats. Treatment of iridoid glucoside alleviated body weight loss in diabetic rats. The effect produced by iridoid glucoside on various parameters was comparable to that of glibenclamide. These results indicate that iridoid glucoside possess antihyperlipidemic effect in addition to its antidiabetic effect.