Dietary conjugated linoleic acid reduces lipid peroxidation by increasing oxidative stability in rats

The antioxidative effect of conjugated linoleic acid (CIA) was examined by determining lipid peroxidation and antioxidative enzyme activities. Male Sprague-Dawley rats were fed one of the experimental diets-normal diet, vitamin E-deficient control diet, 0.5% CLA vitamin E-deficient diet, or 1.5% CLA vitamin E-deficient diet for 5 wk. Hepatic thiobarbituric acid reactive substances (TBARS) were increased in the vitamin E-deficient control group, but they were was significantly lowered in the CLA groups. Similarly, hepatic glutathione peroxidase activity was increased in the vitamin E-deficient diet and reduced by CLA supplementation. In addition, CLA caused a significant decrease in superoxide dismutase activity while having no effect on catalase activity. Analyses of the fatty acid composition revealed that dietary CLA was incorporated into hepatic microsomal membrane dosedependently. Compared to the vitamin E-delicient control, CLA resulted in significantly higher saturated and monounsaturated fatty acids (palmitic and oleic acids) while lowering levels of oxidation-susceptible polyunsaturated fatty acids (linoleic, linolenic, and arachidonic acids) in both plasma and hepatic membrane. The concentrations of plasma cholesterol and triacylglycerol (TG) were lower in the 1.5% CLA group than in other groups. These results suggest that dietary CLA has antiatherosclerotic and antioxidant activity by increasing oxidative stability in plasma and hepatic membrane in the vitamin E-deficient rats.