Dietary polyunsaturated fatty acids, and tissue oxidative stress: the effect of d,l-Ó-tocopherol

ABSTRACT

The effects of feeding young and aged rats with high doses of polyunsaturated fatty acids from marine oil on the susceptibility of erythrocyte membranes to the induction of oxidative stress, on the level of reduced glutathione of different tissues, and on the antioxidant capacity of blood plasma were studied. The protective effect of the supplementation of the oil with d,l-alpha-tocopherol was also assayed. d,l-alpha-Tocopherol supplementation protects erythrocyte membranes from young rats against the induction of oxidative stress, being unable to protect the membranes from the aged ones. The tripeptide glutathione shows a different behavior depending on the tissue. Blood glutathione is not affected by fish oil ingestion and by the d,l- alpha-tocopherol supplementation either in the young or in the aged animals. Liver glutathione is reduced by fish oil feeding in the aged animals only. Brain glutathione is not affected by the fish oil feeding. The supplementation with d,l-alpha-tocopherol restores the hepatic levels of glutathione and increases the brain level of the tripeptide over the controls, this effect being observed for young and the aged rats. The antioxidant capacity of blood plasma in response to the fish oil feeding increases in the young rats only. This capacity is not affected by the suplementation with d,l-alpha-tocopherol. These metabolic changes are ascribed to possible adaptative responses from the animals to the potential risk of oxidative stress induced by fish oil ingestion. We suggest that metabolic risks may be associated with the consumption of high doses of polyunsaturated fatty acids.