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Despite the knowledge on the antiatherogenic effects of exercise, the mechanism by which exercise reduces atherogenic risk remains unknown. In this study, we investigated the hypothesis that chronic exercise-induced oxidative stress may increase plasma total antioxidant capacity and antioxidant defense in the red cells. For 8 weeks, 60 male Dutch rabbits were fed rabbit chow with or without the addition of 2% cholesterol. The animals were further divided into rest and exercise groups (n = 15 for each group). Animals in exercise groups ran on a rodent treadmill at 15 m/min for 10 to 60 minutes gradually for 5 days per week for a total of 8 weeks. At the end of experiments, blood samples were collected and glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) activities were determined in red blood cells. Total antioxidant capacity (TAC), malondialdehyde (MDA) and total thiol (T-SH) levels were measured in plasma. Thoracic aorta and carotid arteries were isolated for histological examination to evaluate atherosclerosis. Eight weeks of chronic exercise reduced atherogenic diet-induced atherosclerotic lesions in all the arteries studied, along with positive changes in cholesterol profile, especially increase of serum HDL-C level. Plasma MDA, TAC and T-SH concentrations were enhanced by exercise in both control and hypercholesterolemic diet groups. Erythrocyte catalase activity was significantly increased by chronic exercise (p < 0.05), whereas total SOD activity rose with exercise only in the control group. Surprisingly, GPX activity was significantly reduced (P < 0.05) in response to exercise in the control group and also in the high cholesterol diet group. Exercise is a useful tool for the prevention and regression of atherosclerosis which is evident by our findings of the enhancement of plasma TAC and positive change in serum cholesterol profile. However, the effect of exercise on red cell antioxidant activities is limited in the hypercholesterolemic animals compared to control animals, possibly in part because of alterations in the ability to adapt to exercise-induced oxidative stress in high cholesterol diet. |
