Effect of Exercise on Antioxidant Enzyme Activities of Skeletal Muscle and Liver in STZ-diabetic Rats

Seok, Kwang Ho; Lee, Suck Kang

Abstract

BACKGROUND: The purpose of the present study was to investigate the effect of exercise on the activities of antioxidant enzymes, superoxide dismutase(SOD), glutathione peroxidase(GPX) and catalase(CAT) of skeletal muscle(gastrocnemius) and liver in streptozotocin(STZ) induced diabetic rats. The malondialdehyde(MDA) concentration was also measured as an index of lipid peroxidation of the tissues by exercise-induced oxidative stresses in the diabetic rats. MATERIAL AND METHODS: Male Sprague-Dawley rats were randomly divided into control and STZ-induced diabetic rats. The STZ in citrate buffer solution was injected twice at 5 days intervals intraperitoneally(50, 70 mg/kg respectively). On the 28th day after the first STZ injection, the diabetic animals were randomly divided into pre- and post-exercise groups. The exercise was introduced to the rats of post-exercise group by treadmill running till exhaution with moderate intensity (VO2max: 50-70%) of exercise. The duration of average running time was 2 hours and 19 minutes.
RESULTS
The blood glucose concentration was increased(p<0.001) and plasma insulin concentration was decreased(p<0.001) in the diabetic rats. The glycogen concentration in the muscle and liver was decreased by exhaustive exercise in the diabetic rats(p<0.001). In the skeletal muscle, the activities of GPX was increased(p<0.05) and the activities of SOD and CAT were not changed in the diabetic rats compare to the control rats. The activities of GPX was not changed by exercise but the activities of SOD(p<0.01) and CAT (p<0.01) were decreased by exercise in the diabetic rats. The concentration of MDA was not changed by exercise in diabetic rats. and the values of pre-exercise and post-exercise diabetic rats were not different from the value of control rats. In the liver, the activities of SOD was decreased(p<0.01) and the activities of GPX and CAT were not changed in diabetic rats compared to the values of control rats. The activities of SOD, GPX and CAT were not changed by exercise in diabetic rats but the the slight decreasing tendency of the activity of SOD was observed. The MDA concentration was increased in the diabetic rats compared to the values of control rats(p<0.001) but there was no change of MDA concentration by exercise in diabetic rats.
CONCLUSIONS
In summary, the exhaustive physical exercise has not been shown to impose oxidative stress on skeletal muscle due to oxygen free radicals regardless of decreament of SOD and CAT in the diabetic rats. In liver tissue, the tissue damage by oxidative stress was observed in diabetic rats but the additional tissue damage by the exhaustive physical exercise was not observed.