Effects of Vitamin E Supplementation on Oxidative Stress in Streptozotocin Induced Diabetic Rats: Investigation of Liver and Plasma

Abstract

This experimental study was designed to investigate the effects of vitamin E supplementation, especially on lipid peroxidation and antioxidant status elements 3/4 namely, glutathione (GSH), CuZn superoxide dismutase (CuZn SOD), and glutathione peroxidase (GSH Px), both in blood and liver tissues of streptozotocin (STZ) diabetic rats. The extent to which blood can be used to reflect the oxidative stress of the liver is also investigated. In diabetic rats, plasma lipid peroxide values were not significantly different,from control,whereas erythrocyte CuZn SOD (p < 0.01), GSH Px (p < 0.001) activities and plasma vitamin E levels (p < 0.001), were significantly more elevated than controls. Vitamin E supplementation caused significant decreases of erythrocyte GSH level (p < 0.01) in control rats and of erythrocyte GSH Px activity (p < 0.05) in diabetic rats. Liver findings revealed significantly higher lipid peroxide (p < 0.001) and vitamin E (p < 0.01) levels and lower GSH (p < 0.001), CuZn SOD (p < 0.001) and GSH Px (p < 0.01) levels in diabetic rats. A decreased hepatic lipid peroxide level (p < 0.01) and increased vitamin E/lipid peroxide ratio (p < 0.001) were observed in vitamin E supplemented, diabetic rats. A vitamin E supplementation level which did not cause any increase in the concentration of the vitamin in the liver or blood, was sufficient to lower lipid peroxidation in the liver. Vitamin E/lipid peroxide ratio is suggested as an appropriate index to evaluate the efficiency of vitamin E activity,independent of tissue lipid values. Further, the antioxidant components GSH, GSH Px and CuZn SOD and the relationships among them, were affected differently in the liver and blood by diabetes or vitamin E supplementation.

Regulation of Glutathione S-Transferase Mu with type 1 diabetes and its regulation with antioxidants

“…Lipid peroxidation also cause protein damage and inactivation of membrane bound enzymes either through direct attack by free radicals or through chemical modification by its end products which are MDA and 4-hydroxynonenal (4-HNE) [26]. According to our results, lipid peroxidation levels in the liver tissues of diabetic rats were significantly higher compared to controls and these findings are in agreement with the results of other related studies [23,27,28]. This marked increase in the lipid peroxidation rates in diabetic tissues suggests an accumulation of oxygen free radicals which can be due to either increased production and/or decreased elimination.…”

“…Numerous studies proposed that, inhibition of oxidative stress with antioxidants might be an effective strategy for reducing the complications of diabetes. The beneficial effects of antioxidants in the treatment of diabetes have been shown by several investigators [19][20][21][22][23]. Although it is clear that oxidative stress plays a major role in diabetic complications, the molecular mechanisms of the effects of antioxidants especially on antioxidant and detoxification enzymes have not been clearly established.…”

A Review on Role of Antioxidants in Diabetes

“…It is believed Vitamin E playing a key role in controlling hyperglycemia, and the combined antioxidants therapy also considered for control and prevention of diabetic complication. The studies in an animal model have shown supplementation of Vitamin E decreases the hepatic lipid peroxide level in streptozotocin-induced diabetes [11]. However, the increased level of lipid peroxide due to change of antioxidant status in the diabetic rat.…”

Effect of vitamins A, E, C and omega-3 fatty acids supplementation on the level of catalase and superoxide dismutase activities in streptozotocin-induced diabetic rats

“…Eukaryotic cells are equipped with a variety of primary and secondary defenses against the deleterious effects of oxidative stress. As lethal injury can occur when these defenses are overwhelmed, supplementation with antioxidant vitamins such as vitamins A, E and C may be benefi cial (4). Vitamin E is a hydrophobic antioxidant found in lipoproteins and membranes and can afford primary as well as secondary stage protection.…”