Role of hepatic and lipoprotein lipase in lipoprotein metabolism and atherosclerosis: studies in transgenic and knockout animal models and somatic gene transfer.

Hepatic lipase (HL) and lipoprotein lipase (LPL) are the two major lipolytic enzymes responsible for the hydrolysis of triglycerides and phospholipids present in circulating plasma lipoproteins. Both lipases are attached to the vascular endothelium via cell surface proteoglycans. HL is primarily involved in the metabolism of chylomicron remnants, intermediate density lipoproteins and high-density lipoproteins whereas LPL catalyzes the hydrolysis of triglycerides from chylomicrons and very low-density lipoproteins. In addition to their traditional function as lipolytic enzymes, HL and LPL appear to serve as ligands that mediate the interaction of lipoproteins to cell surface receptors and/or proteoglycans. Over the past several years significant advances have been made in our understanding of new, alternative mechanisms by which HL and LPL modulate lipoprotein metabolism and the development of atherosclerosis in vivo. This review will summarize some of the new insights generated from the study of transgenic and knockout HL and LPL animal models as well as somatic gene transfer of these two lipases.