THERAPEUTIC SUBSTANCES

Diet and nutrition have substantial impact on reducing the incidence of diabetes mellitus, where oxidative stress is an important etiopathological factor. The combined protective role of low dose of naringin (15 mg kg(-1)) and vitamin C (25 mg kg(-1)) and high dose of naringin (30 mg kg(-1)) and vitamin C (50 mg kg(-1)) on streptozotocin (STZ)-induced toxicity was studied in male Wistar rats. To induce type II diabetes mellitus, rats were injected with STZ intraperitoneally at a dose of 45 mg kg(-1) body weight. STZ-induced diabetic rats showed significant increase in blood glucose, water intake, food intake and glycated hemoglobin and significant decrease in plasma insulin, total hemoglobin, body weight and liver glycogen. Diabetic rats also showed significant decrease in the activity of hexokinase and significant increase in the activities of glucose-6-phosphatase and fructose-1,6-bisphosphatase in liver and kidney. The levels of plasma thiobarbituric acid reactive substances, lipid hydroperoxides and vitamin E were elevated while the level of reduced glutathione was decreased in diabetic rats. Glycoprotein components such as hexose, hexosamine, fucose and sialic acid were increased in plasma, liver and kidney of diabetic rats. Oral administration of high doses of naringin (30 mg kg(-1)) and vitamin C (50 mg kg(-1)) to diabetic rats for a period of 21 days normalized all the above-mentioned biochemical parameters. The effect exerted by naringin (30 mg kg(-1)) and vitamin C (50 mg kg(-1)) was similar to the effect exerted by insulin (6 units kg(-1)). Thus, our study shows the antihyperglycemic and antioxidant effects of naringin and vitamin C in STZ-induced type II diabetes mellitus in rats. Copyright 2008 John Wiley & Sons, Ltd.