Effects of vitamin E suplementation on renal non-enzymatic antioxidants in young rats submitted to exhaustive exercise stress

Background: Exercise stress was shown to increase oxidative stress in rats. It lacks reports of increased protection afforded by dietary antioxidant supplements against ROS production during exercise stress. We evaluated the effects of vitamin E supplementation on renal non-enzymatic antioxidants in young rats submitted to exhaustive exercise stress. Methods: Wistar rats were divided into three groups: 1) control group; 2) exercise stress group and; 3) exercise stress + Vitamin E group. Rats from the group 3 were treated with gavage administration of 1 mL of Vitamin E (5mg/kg) for seven consecutive days. Animals from groups 2 and 3 were submitted to a bout of swimming exhaustive exercise stress. Kidney samples were analyzed for Thiobarbituric Acid Reactive Substances to (TBARS) by malondialdehyde (MDA), reduced glutathione (GSH) and vitamin-E levels. Results: The group treated with vitamin E and submitted to exercise stress presented the lowest levels of renal MDA (1: 0.16+0.02mmmol/mgprot vs. 2: 0.34+0.07 mmmol/mgprot vs. 3: 0.1+0.01 mmmol/mgprot; p<0.0001), the highest levels of renal GSH (1: 23+4μmol/gprot vs. 2: 23+2 μmol/gprot vs. 3: 58+9 μmol/gprot; p<0.0001) and the highest levels of renal vitamin E (1: 24+6μM/gtissue vs. 2: 28+2 μM/gtissue vs. 3: 43+4 μM/gtissue; p<0.001). Conclusion: Vitamin E supplementation improved non-enzymatic antioxidant activity in young rats submitted to exhaustive exercise stress. BACKGROUND During exercise stress, free radicals may be produced in excess of the body’s natural defense. Strenuous exercise increases the whole body and tissue oxygen consumption up to 20 fold, which then elevates electron leakage from the mitochondrial transport system and disturbs the intracellular pro-oxidant and antioxidant homeostasis [1]. There have been many reports showing that exercise causes oxidative stress, e.g., the direct detection of free radical generation in rat skeletal muscle [2] and kidney [3] increases in oxidative damage biomarkers such as thiobarbituric acid reactive substances. The protective capacity of the antioxidant defense system of sedentary individuals may therefore be more easily exceeded under conditions of acute physical exercise. Exogenous antioxidants, primarily obtained as nutrients or nutritional supplements, may help to counteract the oxidative stress of exercise in such subjects unaccustomed to physical activity. Supplementations are a non-pharmacological therapy that has been received attention in the literature [4-7]. More than 40% of people who practice physical activity use some type of dietetic supplementation in order to keep a good health. Vitamin E (a-tocopherol) seems to be a very important agent in providing protection against oxidation of cellular lipids by free radicals that are potentially damaging byproducts of cellular metabolism [8]. Vitamin E supplementation was shown to present protective effects against deterioration of kidney function in rats with streptozotocin-induced Type 1 diabetes mellitus [9]. Exercise stress was already shown to increase oxidative stress in old [3] and just weaned rats [10]. However, reports of increased protection afforded by dietary antioxidant supplements against ROS production during exercise are conflicting. For instance, several authors observed little or no effect of vitamin C and E supplementation on plasma ascorbic acid [11] and lipid peroxidation (LP) [11-13] levels whereas others have demonstrated increases in the concentration of ascorbic acid [14] and unchanged LP level [15] in blood following supplementation. Thus, we aimed to evaluate the effects of vitamin E supplementation on renal non-enzymatic antioxidants in young rats submitted to exhaustive exercise stress.