title: Vitamin E protects guinea pig liver from lipid peroxidation without depressing levels of antioxidants.
abstract: Oxidative stress is considered a pathogenic factor in many disorders. The capacity of dietary vitamin E to increase global antioxidant capacity and to decrease lipid peroxidation was studied in the guinea pig, an animal that cannot synthesize ascorbate. Male guinea pigs were subjected for 5 weeks to three diets differing in vitamin E content in the presence of optimum levels of vitamin C: group 15 (15 mg vitamin E/kg diet), group 150 (150 mg/kg), and group 1500 (1500 mg/kg). Hepatic vitamin E increased in the three groups in relation to the level of vitamin E in the diet. The increase in vitamin E between groups 15 and 150 was accompanied by a reduction in sensitivity to enzymatic lipid peroxidation. This did not occur between groups 150 and 1500. The different liver vitamin E concentrations did not affect the antioxidant enzymes superoxide dismutase, catalase, GSH-peroxidase and GSH-reductase, nor the non-enzymatic antioxidants vitamin C, GSH and ascorbate. It is concluded that dietary supplementation with vitamin E, at a level 6 times higher than the minimum daily requirement for guinea pigs, increases protection against hepatic lipid peroxidation without depressing endogenous antioxidant defences. Further increases in vitamin E to megadose levels did not provide additional protection from oxidative stress. The results also suggest that optimum levels of both vitamin C and vitamin E, simultaneously needed for protection against oxidative stress, are much higher than the minimum daily requirements.
authors.affiliation: Department of Animal Biology-II (Animal Physiology), Faculty of Biology, Complutense University, Madrid, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Cadenas
authors.forename: C
authors.initials: C
authors.lastname: Rojas
authors.forename: R
authors.initials: R
authors.lastname: Pérez-Campo
authors.forename: M
authors.initials: M
authors.lastname: López-Torres
authors.forename: G
authors.initials: G
authors.lastname: Barja
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000032:analysis; D004032:Diet; D005978:Glutathione / Q000032:analysis; D006168:Guinea Pigs; D015227:Lipid Peroxidation / Q000187:drug effects*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress / Q000502:physiology*; D014527:Uric Acid / Q000032:analysis; D014810:Vitamin E / Q000032:analysis / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D014527:Uric Acid; D005978:Glutathione; D001205:Ascorbic Acid