Serum lipoprotein alterations of rabbits fed high fat soy protein-dextrose diets

Abstract

Male New Zealand white rabbits were pair-fed high fat, soy protein-dextrose diets containing either hydrogenated coconut oil (HCO) or safflower oil (SAF) for 100 days. A third group was fed a low fat, soy protein dextrose-corn oil diet (SD) previously shown to be normocholesterolemic in this model. All animals gained similar amounts of weight during the feeding period. The HCO group was significantly hyperlipidemic with elevations of total cholesterol (TC), esterified cholesterol (EC), and phospholipid (PL) fractions. Significant increases of all serum lipoproteins were observed with the HCO diet. The greatest lipoprotein mass increase was in the intermediate density (IDL) fraction. Elevations of EC, PL, and protein contents of all lipoprotein classes were also observed with the HCO diet. Free cholesterol (FC) and triglyceride (TG) were increased to a lesser extent resulting in a net EC enrichment relative to TG among core components. Fatty acid analyses of lipoprotein lipid fractions (TG, EC, PL) reflected the dietary fat type fed except in the IDL fraction of the SAF group. In this instance, significant amounts of oleic acid relative to linoleic acid were observed. This alteration may be the result of the previously reported positional specificity of lipoprotein lipase (LPL) especially when very low density lipoprotein substrates are enriched in linoleate as in the SAF diet fed case. That this change did not occur in the LDL fraction suggests that additional mechanisms other than LPL catalyzed hydrolysis also contribute to LDL composition in the steady state. Such mechanisms may include EC transfer protein mediated exchange, membrane receptor activities, and direct tissue synthesis. The extent to which IDL also participates in such mechanisms also remains to be elucidated.