Lipid metabolism: recent progress in defining the contributions of cholesterol transporters to cholesterol efflux in vitro and in vivo.

Cholesterol efflux from peripheral cells is the first step in reverse cholesterol transport – the process in which excess cholesterol is removed from tissues and delivered to the liver for secretion into bile and/or conversion into bile acids. In atherosclerosis, a large excess of cholesterol accumulates in lipid-engorged macrophages (foam cells). These cholesterol-loaded cells are believed to play an important role in fatty streak formation and in the formation of complex plaques and plaque rupture. The development of foam cells in vivo implies that the cholesterol efflux mechanisms in these cells have failed to keep pace with cholesterol accumulation. An understanding of how cholesterol efflux functions in macrophages and how it can be stimulated may provide opportunities to increase reverse cholesterol transport in the vessel wall and thus prevent or reverse the process of atherosclerosis.