Supplementation of vitamins C and E increases the vitamin E status but does not prevent the formation of oxysterols in the liver of guinea pigs fed an oxidised fat

Background Dietary oxidised fats are a source of oxidative stress. They cause deleterious effects in animal organism by lowering the antioxidant status of tissues and enhancement of the formation of lipid oxidation products. The vitamins E and C might be useful to prevent the formation of oxidation products by dietary oxidised fats. Aim of the study The purpose of this study was to investigate whether or not supplementation of diets with vitamins E and C is able to prevent oxidative stress and the formation of lipid oxidation products caused by dietary oxidised fats. Among lipid oxidation products, oxysterols should be particularly considered because of their high pathophysiological effects. Methods Male guinea pigs were divided into five groups. Four groups were fed diets with an oxidised fat supplemented with 35 or 175 mg alpha-tocopherol equivalents/ kg and 300 or 1000 mg of vitamin C/kg for 29 days. One group, used as a control, was fed the same basal diet with fresh fat with 35 mg alpha-tocopherol equivalents/ kg and 300 mg of vitamin C/kg. Results The guinea pigs fed the oxidised fat diet with 35 mg alpha-tocopherol equivalents/ kg and 300 mg vitamin C/kg had significantly lower concentrations of tocopherols in various tissues, higher concentrations of various oxysterols and thiobarbituric acid-reactive substances in the liver, higher concentrations of glutathione in the liver and lower concentrations of glutathione in erythrocytes than the control animals fed the fresh fat. Increasing the dietary vitamin E concentration from 35 to 175 mg alpha-tocopherol equivalents/ kg and/or the dietary vitamin C concentration from 300 to 1000 mg/kg increased tissue tocopherol concentrations in guinea pigs fed the oxidised fat but did not influence concentrations of oxidation products in the liver and glutathione concentrations in liver and erythrocytes. Conclusions The results demonstrated that supplementation of vitamins E and C improves the vitamin E status but does not prevent the formation of lipid oxidation products in the liver of guinea pigs fed oxidised fats.