Effect of vitamin E (Tri E®) on antioxidant enzymes and DNA damage in rats following eight weeks exercise

Nutrition Journal Effect of vitamin E (Tri E ) on antioxidant enzymes and DNA damage in rats following eight weeks exercise Noor Aini Abd Hamid 0 Mohd A Hasrul 1 Rusdiah J Ruzanna 1 Ibrahim A Ibrahim 0 Prasamit S Baruah 0 Musalmah Mazlan 1 Yasmin Anum Mohd Yusof 1 Wan Zurinah Wan Ngah 1 0 Division of Basic Medical Sciences, Cyberjaya College of Medical Sciences , No 3410, Jalan Teknokrat 3, 63000 Cyberjaya, Selangor Darul Ehsan , Malaysia 1 Department of Biochemistry , Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz 50300 Kuala Lumpur , Malaysia Background: Exercise is beneficial to health, but during exercise the body generates reactive oxygen species (ROS) which are known to result in oxidative stress. The present study analysed the effects of vitamin E (Tri E) on antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (Cat) activity and DNA damage in rats undergoing eight weeks exercise. Methods: Twenty four Sprague-Dawley rats (weighing 320-370 gm) were divided into four groups; a control group of sedentary rats which were given a normal diet, second group of sedentary rats with oral supplementation of 30 mg/kg/d of Tri E, third group comprised of exercised rats on a normal diet, and the fourth group of exercised rats with oral supplementation of 30 mg/kg/d of Tri E. The exercising rats were trained on a treadmill for 30 minutes per day for 8 weeks. Blood samples were taken before and after 8 weeks of the study to determine SOD, GPx, Cat activities and DNA damage. Results: SOD activity decreased significantly in all the groups compared to baseline, however both exercised groups showed significant reduction in SOD activity as compared to the sedentary groups. Sedentary control groups showed significantly higher GPx and Cat activity compared to baseline and exercised groups. The supplemented groups, both exercised and non exercised groups, showed significant decrease in Cat activity as compared to their control groups with normal diet. DNA damage was significantly higher in exercising rats as compared to sedentary control. However in exercising groups, the DNA damage in supplemented group is significantly lower as compared to the non-supplemented group. Conclusions: In conclusion, antioxidant enzymes activity were generally reduced in rats supplemented with Tri E probably due to its synergistic anti-oxidative defence, as evidenced by the decrease in DNA damage in Tri E supplemented exercise group. - Background Exercise is beneficial for the maintenance of a good health but it generates reactive oxygen species (ROS) that may result in oxidative stress [1]. ROS are continuously produced in the normal process of cellular metabolism, but in healthy individuals these are destroyed immediately well within the bodys antioxidant defense system. Physical activity increases the generation of ROS in several ways. Two to five percent of oxygen used in the mitochondrial oxidative phosphorylation forms ROS. As the oxidative phosphorylation increases in response to exercise due to increased oxygen consumption, there will be a concomitant increase in free radicals. Potential sources of ROS during exercise include leakage of electrons from the mitochondrial electron transport chain [2], enhanced purine oxidation, damage to iron-containing proteins, and disruption of Ca2+ homeostasis [3]. Other sources of free radicals that increase with exercise include prostanoid metabolism, xanthine oxidase, NAD(P)H oxidase, and several secondary sources, such as the release of radicals by macrophages recruited to repair damaged tissue [4]. Hence, exercise can produce an imbalance between ROS and antioxidants, which is referred to as oxidative stress. Oxidative stress defined as the imbalance in the oxidants and antioxidants, in favour of the oxidants potentially leading to cellular damage [5]. Oxidative damage results when the generation of ROS produced exceeds the cellular capacity to destroy them to protect or repair it. ROS lead to alterations in membrane protein structure and also brings changes in enzymatic activity [6]. These events may promote damage to cells by causing alterations in mitochondrial and sarcoplasmic reticular membranes and breakdown of lysosomal membranes. An increase in ROS production may occur during and after exercising by an increase of oxygen consumption, increase of catecholamine levels, lactic acid production, elevated rate of hemoglobin auto oxidation and hyperthermia [7-10]. If the free radical generation is greater than the cells ability to neutralise them, the radicals will attack cellular components, especially membranous lipids. They initiates a chain reaction involving oxidation of membranous lipids called lipid peroxidation, which leads to generation of more toxic radicals which may harm other cellular components [11]. Antioxidant defence system comprises of enzymes such as catalase, superoxide dismutase, glutathione peroxidase and non-enzymatic antioxidants including vitamin A, vitamin C, vitamin E, ubiquinone and flavonoids. Antioxidants are molecules which interact with ROS and scavenge the free radicals before cellular vital molecules are damaged preventing cellular damage and disease. Vitamin E, a potent naturally occurring lipid-soluble antioxidant possesses the ability to directly quench free radicals and function as a membrane stabilizer. It protects critical cellular structures against the damage from oxygen free radicals and reactive products of lipid peroxidation. The protective effect of vitamin E supplementation against exerciseinduced oxidative stress has been reported in humans and rats [12-14]. Vitamin E (Tri E) used in this study was tocotrienolrich fraction (TRF) palm oil which contains 70% -tocotrienol and 30% a-tocopherol. The TRF from palm oil proved to be a more economical and efficient substitute for alpha-tocopherol, significantly inhibited oxidative damage in-vitro to both lipids and proteins in rat brain mitochondria. Studies have shown the ability of vitamin E supplementation to reduce oxidative stress or muscle damage caused by exercise [11]. TRF deficiency can increase free-radical induced tissue injury to levels comparable to those found after exercise, so an adequate status of TRF is important for maintaining membrane integrity during exercise [15,16]. In this research, training protocols with rats running on the specially designed treadmill 30 minutes per day for eight weeks were designed to simulate exercise conditions common to rat. The aim of the study was to demonstrate the oxidative stress and DNA damage due to the treadmill exercise protocols on rats and the effect of supplementation with Tri- E. Methods Animals and exercise training protocol Twenty four male rats (weighing 320-370 gm) were obtained from the Animal House, Universiti Kebangsaan Malaysia. They were maintained at 23C. The Animal Ethical Committee of UKM (UKMAEC) approved the experimental procedure of thi (...truncated)