Dietary saturated fatty acid composition has differential effects on HDL binding to Guinea Pig hepatic membranes

Abstract

The effects of dietary saturated fatty acid composition on high density lipoprotein (HDL) metabolism in guinea pigs were investigated. Animals were fed semi-purified diets containing 15% (w/w) fat, either palm kernel oil (PK), high in lauric + myristic acids; palm oil (PO), high in palmitic acid; or beef tallow (BT), high in stearic acid. Intake of the PK diet resulted in the highest plasma total cholesterol level (P<0.001) whereas plasma HDL levels were lowest with the BT diet (P<0.01). Values were 10.3±2.4, 9.1±1.5 and 7.3±1.0 mg/dL (n=9) for animals fed PK, PO and BT respectively. While there were no differences in hepatic cholesteryl ester concentrations, hepatic free cholesterol levels were significantly decreased in animals fed the PO diet (P<0.01). In contrast, cholesterol levels of muscle and adipose were highest in animals fed the PO diet (P<0.05). Adipose tissue fatty acid composition reflected dietary fatty acids. Apolipoprotein E-free HDL binding to hepatic membranes was determined using 125I-HDL. While no differences in receptor affinity (K d) due to dietary fat composition were found, HDL binding protein number (B max) was highest in animals fed the BT diet (2.39±0.05 μg/mg), intermediate in the PK (1.98±0.07 μg/mg) and lowest in the PO group (1.69±0.07 μg/mg) (P<0.01). A significant negative correlation was found between plasma HDL levels and hepatic membrane HDL binding protein number (B max) (r=−0.59, n=18, P<0.01) for the three dietary fat groups. These data demonstrate that changes in dietary saturated fatty acid composition have differential effects on plasma HDL levels which appear related to changes in the capacity of hepatic membranes to bind HDL.