Effects of food restriction on antioxidant defense system in exercised rats

Abstract

The present study was designed to investigate the effects of food restriction on the activities of hepatic antioxidant enzymes in exercised male Fischer-344 rats. Weanling male Fischer-344 rats were fed semipurified diet containing 10% corn oil diet (CO), or lab chow (LC), ad libitum (AL) and at 40% food restriction (FR). After being on the diets for two months, the animals in each diet group was divided into sedentary (S) and exercised (EX) groups. The diets were continued and the animals in the exercise group were run everyday for two months on tread mill to exhaustion. The three key enzymes involved in the antioxidant defense system were determined in the hepatic cytosolic fraction. Catalase activity was significantly higher in the livers of rats fed restricted diets when compared to AL fed rats with the exception of the LC-EX group. Superoxide dismutase (SOD) activity in the CO diet fed groups was significantly lower compared to rats fed the LC diet. Exercise significantly increased SOD activity only in the LC-AL group. In the CO-AL group, SOD activity in exercised rats decreased significantly compared to those from the sedentary group. Exercise resulted in modest increase in the glutathione peroxidase (GSH-Px) activity in these food restricted groups. The LC diet groups had significantly higher levels of saturates (16:0 and 18:0) and monounsaturated fatty acids and significantly lower levels of 18:2n-6, 18:3n-3, 20:3n-3, 20:4n-6, 20:5n-3, 22:5n-3 and 22:6n-3 compared to the CO-fed groups in the liver microsomes. Lipid peroxidation in the liver microsomes of CO fed rats was significantly higher compared to that of LC-AL-S group. The data from the present study suggest that food restriction and exercise have differential effects on the enzymes involved in antioxidant defense and the microsomal fatty acid composition was not altered by exercise or food restriction. Moreover, exercise did not increase lipid peroxidation in these rats.