High density lipoprotein metabolism in a rabbit model of hyperalphalipoproteinemia.

The potential utility of an animal model of hyperalphalipoproteinemia for examining the role of high density lipoprotein (HDL) in atherogenesis prompted the current studies. Preliminary data indicated that in rabbits high-coconut oil feeding for 30 days doubled plasma HDL-cholesterol levels, but did not affect lower density lipoproteins (LDL) (d less than 1.063 g/ml). Experiments were performed to examine the composition of these HDL and to determine the mechanism for the diet-induced increase in plasma HDL. Rabbits were fed commercial chow or chow plus 14% (w/w) coconut oil and blood samples were collected 18 h after feeding. Compared to chow-fed rabbits, peak levels of HDL-cholesterol were attained within 2 weeks, and coconut oil feeding doubled the plasma levels of HDL-cholesterol, phospholipids and protein for up to 4 months without affecting HDL lipid and apoprotein composition. After 3 months the diet also increased VLDL- (107%) and LDL-cholesterol (40%) levels, but the absolute increases in each of these lipoprotein fractions was less than half of that of HDL. Isotope kinetic studies of 125I-HDL protein indicated a doubled rate of production of HDL and no change in the efficiency of removal of HDL from plasma. These studies demonstrate that in the rabbit high-coconut oil feeding doubles the rate of production and turnover of apparently normal HDL particles. It is proposed that such an animal model could be utilized to examine directly the role of HDL in atherogenesis.