Dietary Menhaden and Corn Oils and the Red Blood Cell Membrane Lipid Composition and Fluidity in Hyper- and Normocholesterolemic Miniature Swine

Manuscript received 18 August 1997. Initial reviews completed 23 October 1997. Revision accepted 15 May 1998.

Elliott Berlin, Sam J. Bhathena^*, , Dennis McClure, and Renee C. Peters^*

Metabolism and Nutrient Interactions and ^* Phytonutrients Laboratories, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705 and  Center for Food Safety and Applied Nutrition, Division of Toxicological Studies, Beltsville Research Facility, Food and Drug Administration, U.S. Department of Health and Human Services, Laurel, MD 20708 

Fatty acids in the diet are readily incorporated into lipids in various tissues. However, it is not clear whether all tissues have the same level of incorporation. Second, (n-6) unsaturated fatty acids increase the fluidity of membranes, but this has not been shown for (n-3) fatty acids. In this study, we measured the incorporation of (n-6) and (n-3) fatty acids into erythrocyte membrane lipids and studied their effects on the fluidity of erythrocyte membranes. One group of female miniature swine was made hypercholesterolemic by feeding the swine cholesterol and lard for 2 mo; the other group served as controls and was fed a stock diet. Both groups were then fed either corn oil or menhaden oil or a mixture of the two for 23 additional weeks. Blood was collected at 0, 2, 4, 12 and 23 wk after initialization of the experimental diets, and fatty acid composition of phospholipids was assessed. Membrane phospholipids of pigs fed menhaden oil had elevated (n-3) fatty acids (20:5 and 22:6), and lower 18:2 than those fed corn oil. There was no difference in 20:4 content. The fatty acid changes occurred as early as 2 wk after consumption of the corn oil or menhaden oil in pigs previously fed a stock diet, but it took longer in pigs previously fed lard + cholesterol, indicating residual effects of pretreatment. Menhaden oil increased anisotropy (indicating decreased fluidity) more than corn oil for the nonpolar probe diphenylhexatriene (DPH) at earlier time points, but not at 23 wk. Erythrocyte membrane fluidity was significantly related to membrane polyunsaturate content, with (n-6) fatty acids having a greater influence than (n-3) fatty acids. A comparison of the present red blood cell fatty acid compositions with brain synaptosome fatty acid compositions for the same animals showed poor correlations for some of the fatty acids. There was no significant direct relationship between docosahexaenoate (DHA) concentrations in erythrocyte membranes with DHA concentrations in brain synaptosomes from cerebellum, forebrain and caudate nucleus.

The Journal of Nutrition Vol. 128 No. 9 September 1998, pp. 1421-1428
Copyright ©1998 by the American Society for Nutritional Sciences