American Journal of Pharmacology and Toxicology 2 (1): 4-9, 2007 ISSN 1557-4962 © 2007 Science Publications Corresponding Author: Amr Amin, Department of Biology, Faculty of Science, UAE University, Al-Ain, P.O. Box 17551, UAE, Tel: +97137134381, Fax: +97137671291 4 The Effect of Vitamin C on the Metabolic Parameters of Experimental Diabetes Mellitus 1 Mariam Al-Shamsi, 2 Amr Amin, 3 Ernest Adeghate 1 Enviromental Graduate Program, 2 Department of Biology, Faculty of Science 3 Department of Anatomy Faculty of Medicine and Health Sciences, UAE University Al-Ain, UAE Abstract: The role of vitamin C on diabetes mellitus is unknown. The purpose of this study was to examine the effect of oral administration of vitamin C on some of the metabolic parameters of diabetic rats. Diabetes was induced by intraperitoneal injection of STZ (60 mg kg¯ 1 body weight at 12 weeks of age). Vitamin C (10, 50, 100 mg kg¯ 1 body weight) was administered orally for a period of four weeks to normal and diabetic male Wistar rats. In some experiments vitamin C was given either before or after the induction of diabetes mellitus. Glucose tolerance test (GTT) was performed on fasted normal, diabetic and vitamin C-treated rats at the end of the experimental period. Blood sugar level and weight were also recorded on a weekly basis for each rat in different groups. Vitamin C significantly (p<0.05) reduced blood glucose level and decreased weight gain in experimental diabetes mellitus at all doses when compared to untreated rats. This beneficial effect of vitamin C on the hyperglycemia of diabetic rats was dose-dependent. Moreover, vitamin C also improved GTT in diabetic rats compared to untreated diabetic rats. In conclusion, vitamin C may play a role in insulin metabolism and thus be a useful adjuvant therapy in diabetes mellitus. Key words: ROS, vitamin C, antioxidants, diabetes, glucose INTRODUCTION Diabetes mellitus (DM) is currently taking its place as one of the main threats to human health in the 21 st century. In the past two decades the number of people with diabetes has increased worldwide. DM affects approximately 6% of the world population [1] . It is also one of the most prevalent (the estimated lifetime risk of developing diabetes for individuals born in 2000 is 32.8% for males and 38.5% for females) and costly chronic diseases, which significantly reduces life expectancy [2,3] . In the year 2000, the total number of people with DM was 151 million and the number is projected to increase by 46% to reach 221 million by the year 2010 and 300 million in 2025 [4] . DM is a heterogeneous group of disorders characterized by high blood glucose level [5] . DM is associated with abnormal changes in protein, carbohydrate and fat metabolism [6] and induce disturbances in lipid profiles especially, an increased susceptibility to lipid peroxidation [7] . DM is a chronic disease associated with severe late complications. Diabetes accounts for a substantial burden of morbidity and mortality through micro- and macro vascular complications [8,9] . The most common chronic complications of diabetes include retinopathy, nephropathy, neuropathy and atherosclerosis [10] . Strict control of blood glucose, blood pressure and cholesterol can reduce the risk of diabetes-related complications [8,11] . It has been postulated that diabetes- associated complications involves oxidative stress perhaps as a result of hyperglycemia [12] . In diabetes, the elevated blood glucose increases the reactive oxygen species (ROS). ROS then causes membrane damage through facilitating peroxidation of membrane lipids and protein glycation [13,14] . The sources of ROS in diabetes include free radical reactions related to glycation of proteins, consumption of NADPH through the polyol pathway, glucose autoxidation, hyperglycemia-induced pseudo hypoxia and activation of protein kinase C [15] . Vitamin C is a water soluble antioxidant that was firstly isolated and characterized by Szent-Gyorgyi in 1928 [16] . Ascorbic acid has several antioxidant properties. It is an essential cofactor involved in many biochemical functions and it acts as an electron donor or reducing agent, it is said to have ascorbate oxidant activity [17] . Ascorbate effectively scavenge singlet oxygen, superoxide, hydroxyl and water soluble peroxyl radical and hypochlorous acid [18] . The purpose of this study was to characterize some