EFFECTS OF OMEGA-3-FATTY-ACID AND VITAMIN-E SUPPLEMENTATION ON ERYTHROCYTE-MEMBRANE FLUIDITY, TOCOPHEROLS, INSULIN BINDING, AND LIPID-COMPOSITION IN ADULT MEN

Dietary supplementation with an omega-3 fatty acid preparation (fish oil) together with pharmacologic doses of vitamin E increased both insulin binding and membrane fluidity in erythrocytes from human adult males. Supplementation with fish oil alone induced significant increases in the alpha- and gamma-tocopherol contents of the red blood cell membranes. Forty healthy men were given controlled diets and supplements, which together provided 40% of energy from fat (polyunsaturated:monosaturated:saturated ratio of 0.8:1:1), 360 mg cholesterol/day, and a minimum of 22 mg alpha-tocopherol (alpha-T)/day for three successive experimental periods of 10, 10, and 8 weeks, during which they were given capsules containing 15 g of a placebo oil/day, 15 g fish oil concentrate (FOC)/day, and 15 g fish oil + 200 IU alpha-T (FOC + alpha-T)/day, respectively. Erythrocyte ghost insulin binding (IB) and 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence-determined fluidity were significantly increased following the FOC + alpha-T period, however FOC alone had no effect. At the end of each experimental period, IB values, as percentage bound/100-mu-g ghost protein at 4-degrees-C, were 0.96, 0.91, and 1.35, and DPH steady state fluorescence anisotropies were 0.311, 0.303, and 0.296, at 4-degrees-C, respectively. Small but statistically significant decreases in fluorescence lifetimes further indicated increased fluidity. FOC supplementation resulted in significantly lower membrane cholesterol:phospholipid ratios and increased membrane tocopherols despite daily vitamin E consumption of only 22 mg as in the placebo period. Membrane incorporation of n-3 fatty acids was, however, limited. Thus, dietary polyunsaturated fatty acids exerted substantial effects on erythrocyte membranes by affecting membrane contents of lipid molecules other than the fatty acids.