EFFECTS OF DIETARY OXIDIZED CHOLESTEROL ON LIPID-METABOLISM IN DIFFERENTLY AGED RATS

Male Sprague-Dawley rats, 4 weeks (young) or 8 months (adult) of age, were fed one of three purified diets free of or containing either 0.5% cholesterol or 0.5% oxidized cholesterol (92% oxidized cholesterol) for 3 weeks. Feeding of oxidized cholesterol caused a significant reduction of food intake, body weight gain, and relative liver weight in rats of both ages. The activity of the HMG-CoA reductase and cholesterol 7 alpha-hydroxylase of liver microsomes, the key enzymes in cholesterol synthesis and catabolism, respectively, was lowered by oxidized cholesterol compared to the diet free of cholesterol in both ages, and the difference was significantly in the adult. On the other hand, the activity of Delta 6-desaturase of Liver microsomes, a key enzyme in linoleic acid metabolism to arachidonic acid, was significantly increased by oxidized cholesterol in adult rats, leading to the increase in linoleic acid desaturation index [(20:3n-6 + 20:4n-6)/18:2n-6] in liver phospholipids. Oxidized cholesterol reduced the concentration of cholesterol in serum and liver. Also, the fecal excretion of acidic steroids was lower in rats fed the oxidized cholesterol diet than in those fed the cholesterol-free diet. Thus, oxidized cholesterol significantly influenced cholesterol and fatty acid metabolism in particular in adult rats.