Influence of Dietary Vitamin E on Malondialdehyde Levels in Liver and Adipose Tissue and on Glutathione Peroxidase and Reductase Activities in Liver and Erythrocytes of Lean and Obese (Ob/Ob) Mice

Abstract

To determine the effect of obesity on the dietary requirement for vitamin E, genetically obese mice (OM) and their lean littermates (LM) were assigned to casein-based diets supplemented with 0, 40, 80, or 320 ppm vitamin E (E) for 6 weeks. At the end of this period, mice were decapitated, and erythrocytes, liver, and adipose tissue taken for analysis. Hepatic and adipose tissue fat soluble antioxidant (FSAO) concentration increased with increasing dietary E. Hepatic FSAO response was similar among OM and LM. However, adipose FSAO increased only slightly among OM in response to increasing E, while LM showed in excess of a fivefold increase between 0 and 80 ppm supplemental E. Hepatic and adipose malondialdehyde (MDA) concentration, an indicator of lipid peroxidation, declined with increasing E. The MDA concentration among OM, however, did not respond as sharply as LM to increasing E. Adipose fatty acid (FA) composition differed among LM and OM; OM had a lower proportion of linoleic acid than did LM. Further, as dietary E increased, the proportion of linoleic and palmitoleic acids increased, while palmitic, stearic, and oleic acids decreased in both LM and OM. On the basis of these responses in FSAO, MDA, and FA; OM appear to have a higher requirement for E than their lean counterparts. Hepatic glutathione peroxidase activity decreased as a function of increasing E among both LM and OM. Hepatic glutathione reductase and glucose-6-phosphate dehydrogenase activities tended to be higher among OM than LM, but at 320 ppm E, LM, and OM had similar activities for these enzymes and at 0 ppm E glutathione reductase activity was not different. Erythrocyte enzymes showed no effect of phenotype or diet.