DIETARY FISH OIL AND VITAMIN E INFLUENCES TISSUE GLUTATHIONE SYSTEM589

Abstract

Polyunsaturated fatty acid rich fish oil (FO) diet enhances the susceptibility of certain tissues to oxidative lipid damage. Vitamin E (VE) is a major chain breaking lipophilic antioxidant that functions to protect against lipid peroxidation. In biological systems, aqueous and lipid phase antioxidants work in synergy in the form of a antioxidant chain reaction. The key physiological antioxidant reduced glutathione (GSH) plays a critical role in regenerating other critical antioxidants e.g., VE and ascorbate. We investigated the effect of 8 wk intragastric FO (1 g/kg b.w; equivalent amount of soya oil, SO, was fed to placebo treated controls) and VE(750 IU/kg b.w) supplementation on the tissue glutathione system of rats(n=12-14/group) at rest or subjected to exhaustive treadmill run induced oxidative stress. VE supplementation increased VE contents in skeletal muscles, heart, lung and liver. In liver, VE incorporation was higher(P<0.001) in FO and VE co-supplemented group (FOVE) compared to SOVE. At rest, red gastrocnemius muscle (RG) total glutathione (TGSH) content and glutathione-S-transferase (GST) activity were higher (P<0.05) in FOVE compared to SOVE. Also, hepatic GST and glutathione reductase activities were higher (P<0.001) in FOVE compared to SOVE. Exercise lowered (P<0.01) muscle and liver TGSH level˙s, this effect was less pronounced (P<0.05) in FOVE vs. SOVE. Exercise increased GST activity in liver and RG only in SOVE group(P<0.01). Dietary FO and VE results in tissue specific alterations in glutathione system. Compared to VE alone, FOVE enhanced VE availability in liver and enhanced RG TGSH content perhaps by sparing the consumption of GSH.