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 lipolyti c enzymes responsible for the hydrolysis of triglycerides and phospholipids present in circulating plasma lipoproteins. Both lipases are attached to t he vascular endothelium via cell surface proteoglycans. HL is primarily inv olved in the metabolism of chylomicron remnants, intermediate density lipop roteins and high-density lipoproteins whereas IPL catalyzes the hydrolysis of triglycerides from chylomicrons and very low-density lipoproteins. In ad dition to their traditional function as lipolytic enzymes, HL and LPL appea r to serve as ligands that mediate the interaction of lipoproteins to cell surface receptors and/or proteoglycans. Over the past several years signifi cant advances have been made in our understanding of new alternative mechan isms by which HL and LPL modulate lipoprotein metabolism and the developmen t of atherosclerosis in vivo. This review will summarize some of the new in sights generated from the study of transgenic and knockout HL and LPL anima l models as well as somatic gene transfer of these two lipases.