Effect of dietary corn, coconut, and menhaden oils on lipoprotein, liver, and heart membrane composition in the hypercholesterolemic rabbit

Abstract

The relative capacities of n-3 and n-6 polyunsaturated fatty acid-containing diets (PUFA) to modify chemical composition in plasma lipoproteins, liver membrane, and heart phospholipids and to thereby modulate lipoprotein and membrane fluidity were studied in the rabbit. Stock diet-fed New Zealand rabbits were made hypercholesterolemic by feeding a casein-based, semi-purified diet containing coconut oil. Subsequent replacement of the coconut oil with corn or menhaden oil caused reduction or elevation, respectively, of blood cholesterol levels. Very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) became progressively less fluid following transfer from the PUFA containing low fat stock diet to the coconut oil diet. Subsequent corn oil feeding induced significant increases in VLDL and LDL, but not HDL, fluidities. Menhaden oil feeding did not affect lipoprotein fluidity. Liver membranes were less fluid in corn oil-fed and menhaden oil-fed than in coconut oil-fed rabbits. Despite these differences in lipoprotein and membrane fluidity the amount of rabbit 125I-LDL capable of binding to liver membranes from the animals was not affected by the dietary fat modifications. Fatty acyl compositions were affected by the diets. Heart and liver phospholipids showed extensive incorporation of n-3 fatty acids and deletion of linoleate in the menhaden oil-fed animals. Dietary effects on lipoprotein phospholipid fatty acids were statistically significant but not as pronounced as in these tissues.