Hepatic perfusate very low density lipoproteins obtained from fat-fed nonhuman primates stimulate cholesterol esterification in macrophages.

Abstract

The livers of both baboons and rhesus monkeys fed a high fat, high cholesterol diet secreted very low density lipoproteins (VLDL) that were enriched in cholesteryl ester and apoe as compared to VLDL secreted by the livers of chow-fed animals. Stimulation of macrophage cholesterol esterification by the experimental VLDL was compared to that produced by the standard beta-VLDL obtained from the plasma of a rhesus monkey fed 25% coconut oil plus 2% cholesterol. This standard beta-VLDL stimulated 7- to 10-fold more esterification than did the bovine albumin control. Hepatic VLDL from fat-fed animals stimulated esterification in J774 macrophages 50 to 150% as well as did the standard beta-VLDL, even though hepatic VLDL did not display beta electrophoretic mobility on agarose gel electrophoresis. Plasma VLDL from lard-fed baboons did not exhibit beta electrophoretic mobility but did stimulate esterification in macrophages. Baboons were divided into high and low responders based on the change in plasma cholesterol levels in response to a high fat, high cholesterol diet. Both plasma and hepatic VLDL from high responders stimulated cholesterol esterification, whereas hepatic VLDL obtained from low responders or chow-fed baboons did not stimulate cholesterol esterification in macrophages. There was a strong positive correlation (r = 0.866) between the number of apoE molecules per VLDL particle in VLDL obtained from chow-fed, lard-fed, or coconut oil-fed primates and the rate of cholesterol esterification in macrophages. Our results show that hepatic perfusate VLDL obtained from fat- and cholesterol-fed primates have compositional and functional properties usually ascribed to circulating beta-VLDL, without displaying beta mobility, and indicate that the liver may be an important source of atherogenic lipoproteins.