Coronary artery disease (CAD) is a major cause of

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1 Brief Review Hepatic Lipase, Lipoprotein Metabolism, and Atherogenesis Silvia Santamarina-Fojo, Herminia González-Navarro, Lita Freeman, Elke Wagner, Zengxuan Nong Abstract The role of hepatic lipase as a multifunctional protein that modulates lipoprotein metabolism and atherosclerosis has been extensively documented over the last decade. Hepatic lipase functions as a lipolytic enzyme that hydrolyzes triglycerides and phospholipids present in circulating plasma lipoproteins. Hepatic lipase also serves as a ligand that facilitates lipoprotein uptake by cell surface receptors and proteoglycans, thereby directly affecting cellular lipid delivery. Recently, another process by which hepatic lipase modulates atherogenic risk has been identified. Bone marrow transplantation studies demonstrate that hepatic lipase present in aortic lesions markedly alters aortic lesion formation even in the absence of changes in plasma lipids. These multiple functions of hepatic lipase, which facilitate not only plasma lipid metabolism but also cellular lipid uptake, can be anticipated to have a major and complex impact on atherogenesis. Consistently, human and animal studies support proatherogenic and antiatherogenic roles for hepatic lipase. The concept of hepatic lipase as mainly a lipolytic enzyme that reduces atherogenic risk has evolved into that of a complex protein with multiple functions that, depending on genetic background and sites of expression, can have a variable effect on atherosclerosis. (Arterioscler Thromb Vasc Biol. 2004;24: ) Key Words: transgenic mouse models lipolytic enzyme ligand-binding function macrophages bone marrow transplantation aortic atherosclerosis Coronary artery disease (CAD) is a major cause of mortality in advanced societies. 1 3 Multiple factors contribute to the formation of lesions that ultimately lead to CAD. One of the initial events in the development of atherosclerosis is the accumulation of cells containing excess lipids within the arterial wall. 4 Plasma lipoproteins play a major role in the deposition and removal of lipids that accumulate in atherosclerotic lesions. Apolipoprotein B (apob) containing lipoproteins and high-density lipoprotein (HDL) have opposite effects on CAD and are independent risk factors for this disease. 5 7 Both classes of lipoproteins have been major targets for the development of new therapeutic approaches for treatment of CAD. During the last decade, a great deal of interest has focused on hepatic lipase and its impact on lipoprotein metabolism, including intermediate-density lipoproteins (IDLs), chylomicron remnants and HDLs, and atherogenesis. Hepatic lipase has been shown in several studies to modulate atherogenic risk; however, its role as either a protective or proatherogenic agent remains unclear. Published human and animal studies support proatherogenic and antiatherogenic functions for hepatic lipase In humans, low hepatic lipase activity has been associated with increased risk of CAD Furthermore, premature CAD has been reported in patients with complete hepatic lipase deficiency, 19 although the manner in which these very few individuals have been identified raises the issue of ascertainment bias. Other studies have concluded that decreased hepatic lipase activity does not influence susceptibility to CAD. 20 Finally, increased hepatic lipase activity has been reported in patients with CAD. 21,22 A proatherogenic role for hepatic lipase has been suggested from the inverse correlation between increased hepatic lipase activity and the plasma levels of the antiatherogenic HDL and the positive correlation with small dense proatherogenic low-density lipoprotein (LDL). 11,22,23 Analyses of transgenic (Tg) and knockout (KO) animal models have also provided conflicting data regarding the role of hepatic lipase in atherosclerosis. Hepatic lipase overexpression beneficially alters the plasma lipid profile in mice and rabbits by reducing the amount of cholesterol present in apob-containing lipoproteins In addition, overexpression of human hepatic lipase reduced the aortic cholesterol content in cholesterolfed mice. 27 However, hepatic lipase deficiency in lecithin: cholesterol acyltransferase (LCAT) Tg and apoe KO mice significantly reduced aortic atherosclerosis despite the increase in cholesterol content in the apob-containing lipoproteins. 28,29 In the latter mouse model, cholesterol accumulated in distinct phospholipid-rich lamellar apob-containing particles. 30 In addition, although the atherogenicity of dense LDL has not been investigated in animals, hepatic lipase activity has been shown to enhance the formation of small, dense LDL particles in mice and rabbits Recent work elucidating the multifunctional roles of hepatic lipase may help to resolve these discrepant observations. Hepatic lipase plays a major role in lipoprotein metabolism as a lipolytic enzyme that hydrolyzes triglycerides and Original received April 27, 2004; final version accepted July 19, From the Molecular Disease Branch, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH), Bethesda, Md. This article is a written summary of the 2002 George Lyman Duff Memorial Lecture, which was presented at the 2002 Scientific Sessions in Chicago, Ill. Correspondence to Silvia Santamarina-Fojo, NHLBI, NIH, 10 Center Dr, Bethesda, MD silvia@mdb.nhlbi.nih.gov 2004 American Heart Association, Inc. Arterioscler Thromb Vasc Biol. is available at DOI: /01.ATV d 1750

2 Santamarina-Fojo et al Hepatic Lipase, Lipoprotein Metabolism, and Atherogenesis 1751 Figure 1. Schematic illustration of the classic function of hepatic lipase as a lipolytic enzyme. Hepatic lipase hydrolyzes triglycerides and phospholipids present in circulating plasma lipoproteins releasing diglycerides, lysophospholipids, and FFAs. phospholipids in chylomicron remnants, IDL, and HDL (Figure 1). Patients with hepatic lipase deficiency present with hypercholesterolemia or hypertriglyceridemia and accumulate -very low density lipoproteins (VLDLs), chylomicron remnants, IDLs, triglyceride-rich LDLs, and HDLs. 12,34 39 However, not all patients with hepatic lipase deficiency present with these lipoprotein abnormalities, and in a subset of patients, the lipoprotein phenotype may have been confounded by the presence of other metabolic and genetic defects. 40 Like human patients, hepatic lipase deficient mice 41 have increased plasma concentrations of HDL cholesterol and phospholipids. In humans, hepatic lipase plays a major role in determining LDL subclass distribution, which, in turn, modulates atherogenic risk. 11,42 45 Hepatic lipase is also an important determinant of HDL concentration, converting the phospholipid-rich HDL 2 to HDL 3. 11,20,39,42,43,46 52 Because hepatic lipase lowers plasma concentrations of the proatherogenic apob-containing lipoproteins as well as the antiatherogenic HDL, the net effect of these hepatic lipase induced alterations in plasma lipoproteins on CAD is not easily predictable. In addition to its function as a lipolytic enzyme, hepatic lipase has a separate role in lipoprotein metabolism as a ligand that facilitates the uptake of lipoproteins and lipoprotein lipids by cell surface receptors or proteoglycans (Figure 2). In vitro studies have demonstrated that hepatic lipase enhances the binding or uptake of chylomicrons, chylomicron remnants, VLDL, LDL, and HDL cholesterol (HDL-C) 56,59 61 into a variety of cell types. Cell surface receptors, including the LDL receptor (LDLr), 55 LDLr-related protein (LRP), 53,60 and scavenger receptor B1 (SR-B1), 59,61 as well as cell surface proteoglycans, 54,60 have been implicated in these processes. Initial evidence supporting a role of the ligand-binding function of hepatic lipase, independent of the lipolytic function of the lipase, in cellular lipid uptake and lipoprotein metabolism was provided by studies using heat-inactivated hepatic lipase 56 and antihepatic lipase antibodies. 55,58 These data were subsequently confirmed by in vivo experiments that demonstrated that expression of the catalytically inactive form of hepatic lipase, HL-145G, reduced the plasma levels of apob-containing lipoprotein cholesterol and HDL-C in different mouse models. Using recombinant adenovirus, Dugi et al 62 and Amar et al 63 showed that transient expression of the catalytically inactive HL-145G in mice with no endogenous expression of hepatic lipase (HL-KO mice) or of apoe (apoe-ko mice) decreased the plasma concentrations of HDL-C as well as remnant lipoproteins by mechanisms independent of lipolysis. Similar findings were observed in apoe-ko and LDLr-KO Tg mice with long-term expression of the catalytically inactive hepatic lipase. 24,26 In these latter studies, the effect of the catalytically inactive hepatic lipase on plasma lipoprotein metabolism was confounded by expression of the endogenous, fully active mouse hepatic lipase. Recently, Dichek et al 64 reported that overexpression of the catalytically inactive hepatic lipase in LDLr-KO, LDLr-KO apob-100 and LDLr- KO apob-48 mice lacking endogenous HL facilitates the clearance of apob-48 containing and apob-100 containing lipoproteins. In humans, the presence or absence of hepatic lipase protein in patients with functional deficiency of hepatic lipase also leads to significant differences in the cholesterol content of the apob-containing lipoproteins. 65 These combined animal and human studies support an important physiological role for the ligand-binding function of hepatic lipase in vivo. Despite these recent advances in elucidating the role of hepatic lipase in lipoprotein metabolism, little is known about the independent contributions of the ligand-binding function versus the lipolytic function of hepatic lipase to the development of atherosclerosis. Current studies have begun to address these questions. Recently, González-Navarro et al 66 showed that hepatic expression of catalytically inactive HL- 145G in mice deficient in apoe and hepatic lipase (apoe- KO HL-KO mice) markedly lowers the plasma concentrations of cholesterol-rich remnants and significantly reduces proximal aortic atherosclerosis. Thus, in this animal model, the ligand-binding function of hepatic lipase protects against lesion development. The involvement of hepatic lipase in a novel proatherogenic pathway was first inferred from the unexpected finding that despite increased levels of the proatherogenic apobcontaining lipoproteins, hepatic lipase deficiency reduces aortic lesion formation in apoe-ko mice 28 and LCAT Tg mice. 29 These findings suggested the possibility that this Figure 2. Schematic illustration of hepatic lipase (HL) as a ligand that facilitates the interaction between circulating plasma lipoproteins and cell surface receptors and proteoglycans.

3 1752 Arterioscler Thromb Vasc Biol. October 2004 lipase might have a localized effect on the arterial wall that could overwhelm the hepatic lipase mediated effects on the plasma lipoproteins. We thus evaluated hepatic lipase expression in the various cell types that comprise aortic lesions. 67 Hepatic lipase mrna was detected in peritoneal macrophages and in 2 immortalized mouse macrophage cell lines (RAW and IC-21). Moreover, Western analysis of partially purified cell lysates from mouse peritoneal macrophages and RAW cells, as well as human monocyte derived macrophages and THP cells, revealed a 62-kDa protein immunoreactive to the antihepatic lipase antibody. As a functional test to determine whether macrophage expression of hepatic lipase was proatherogenic, bone marrow from HL-KO donor mice was transplanted into irradiated HL wild-type mice and vice versa, in apoe-ko and LCAT-Tg backgrounds. Interestingly, macrophage hepatic lipase expression in the arterial wall enhanced early lesion formation in apoe-ko and LCAT-Tg mice without modification of plasma lipoprotein lipids or hepatic lipase activities. 29 These findings identify a new pathway by which hepatic lipase modulates atherogenic risk in vivo. 29,67 Localized production of hepatic lipase within the vessel wall has many implications. Like lipoprotein lipase, hepatic lipase expression in the arterial wall may result in localized increased production of free fatty acids (FFAs), increased cholesterol uptake, retention of LDL in the subendothelial wall, and macrophage recruitment, all of which would enhance lesion formation Aviram et al 72 reported that hepatic lipase enhances the uptake and accumulation of LDL-C by macrophages, and Nong et al 29 have shown that the uptake of oxidized LDL-C differed significantly in peritoneal macrophages isolated from hepatic lipase KO mice compared with control mice. Accumulation of cholesterol by macrophages has been demonstrated to alter macrophage gene expression and promote atherosclerosis. Thus, in addition to its classical role as a lipolytic enzyme and to its ligand-binding function, our data provide evidence that hepatic lipase may modulate atherogenic risk, independent of changes in the plasma lipid profile, by altering macrophage cholesterol accumulation (Figure 3). Hepatic lipase present in the arterial wall may significantly alter lesion formation. Future studies will be required to further elucidate the mechanism by which hepatic lipase may exert this effect. Summary The role of hepatic lipase in CAD has long been controversial, with evidence supporting a proatherogenic and antiatherogenic role for hepatic lipase. Recent studies have revealed that in addition to its role as a lipolytic enzyme that remodels LDL and HDL, hepatic lipase also has a ligand-binding function that enhances lipid and lipoprotein uptake by cell surface receptors and proteoglycans. In addition, the recent finding that hepatic lipase is present in the vessel wall 67 and that its presence is atherogenic 29 provides a partial explanation for the conflicting data on the role of hepatic lipase in CAD. The last decade has yielded a great deal of insight into the role of hepatic lipase in lipoprotein metabolism and atherogenesis. The concept of hepatic lipase as mainly a lipolytic enzyme that reduces Figure 3. Schematic illustration of the multiple roles of hepatic lipase (HL) in lipoprotein metabolism and cellular lipid uptake in liver as well as macrophages present in the vessel wall. HL, present in the basolateral surface of hepatocytes 76,77 and the luminal and subluminal surfaces of endothelial cells 77,78 or freely circulating in the bloodstream, hydrolyzes triglycerides and phospholipids present in circulating plasma lipoproteins, including IDL, chylomicron remnants (not shown), and HDL. During lipolysis, a small fraction of HL may dissociate, attach to circulating lipoproteins, and bind proteoglycans (Figure 2) present on the cell surface. Alternatively, circulating plasma lipoproteins can interact with HL already attached to cell surface proteoglycans (Figure 2). The lipase lipoprotein complex can then undergo internalization, a process that is independent of lipolysis and can be mediated by proteoglycans, the LDLr, and LRP, as well as SR-B1, which facilitates selective lipid uptake. Within the atheromatous plaque, HL facilitates cholesterol accumulation in macrophages, 29,72 altering macrophage gene expression and enhancing the atherosclerotic process. atherogenic risk has evolved into that of a complex protein with multiple functions with variable effects on atherosclerosis. The future challenge will be to use these insights to achieve new treatments for CAD. References 1. Anderson KM, Castelli WP, Levy D. Cholesterol and mortality: 30 years of follow-up from the Framingham Study. J Am Med Assoc. 1987;257: Schaefer EJ, Lamon-Fava S, Cohn SD, Schaefer MM, Ordovas JM, Castelli WP, Wilson PWF. Effects of age, gender, and menopausal status on plasma low-density lipoprotein cholesterol and apolipoprotein B levels in the Framingham Offspring Study. J Lipid Res. 1994;35: Kreger BE, Odell PM, D Agostino RD, Wilson P. Long-term intraindividual cholesterol variability: natural course and adverse impact on morbidity and mortality: the Framingham Study. Am Heart J. 1994;127: Smith EB. The relationship between plasma and tissue lipids in human atherosclerosis. Adv Lipid Res. 1974;12: Castelli WP, Anderson K, Wilson PW, Levy D. Lipids and risk of coronary heart disease: the Framingham Study. Ann Epidemiol. 1992;2: Gordon DJ, Rifkind BM. High-density lipoprotein: the clinical implications of recent studies. N Engl J Med. 1989;321: Miller NE. Associations of high-density lipoprotein subclasses and apolipoproteins with ischemic heart disease and coronary atherosclerosis. Am Heart J. 1987;113: Santamarina-Fojo S, Haudenschild C, Amar M. The role of hepatic lipase in lipoprotein metabolism and atherosclerosis. Curr Opin Lipidol. 1998; 9: Zambon AA, Deeb SSD, Pauletto PB, Crepaldi GA, Brunzell JD. Hepatic lipase: a marker for cardiovascular disease risk and response to therapy. Curr Opin Lipidol. 2003;14: Jansen H, Verhoeven AJM, Sijbrands EJG. Hepatic lipase: a pro- or anti-atherogenic protein. J Lipid Res. 2002;43:

4 Santamarina-Fojo et al Hepatic Lipase, Lipoprotein Metabolism, and Atherogenesis Zambon A, Deeb SS, Hokanson JE, Brown BG, Brunzell JD. Common variants in the promoter of the hepatic lipase gene are associated with lower levels of hepatic lipase activity, buoyant LDL, and higher HDL 2 cholesterol. Arterioscler Thromb Vasc Biol. 1998;18: Jansen H, Verhoeven AJ, Weeks L, Kastelein JJ, Halley DJ, van den Ouweland A, Jukema JW, Seidell JC, Birkenhaer JC. Common C-to-T substitution at position -480 of the hepatic lipase promoter associated with a lowered lipase activity in coronary artery disease patients. Arterioscler Thromb Vasc Biol. 1997;17: Beisiegel U. New aspects on the role of plasma lipases in lipoprotein catabolism and atherosclerosis. Atherosclerosis. 1996;124: Santamarina-Fojo S, Haudenschild C. Role of hepatic and lipoprotein lipase in lipoproten metabolism and atherosclerosis: studies in transgenic and knockout animal models and somatic gene transfers. Int J Tissue React. 2000;22: Klaus DA, Brandauer K, Schmidt N, Nau B, Schneider JG, Mentz S, Keiper T, Schaefer JR, Meissner C, Kather H. Low hepatic lipase activity is a novel risk factor for coronary artery disease. Circulation. 2001;104: Hokanson JE, Cheng S, Snell-Bergeon JK, Fijal BA, Grow MA, Hung C, Erlich HA, Ehrlich J, Eckel RH, Rewers M. A common promoter polymorphism in the hepatic lipase gene (LIPC-480C T) is associated with an increase in coronary calcification in type 1 diabetes. Diabetes. 2002;51: Groot PHE, Van Stiphout WAHJ, Krauss XH, Jansen H, van Tol A, Van Ramshorst E, Chin-On S, Hofman A, Cresswell SR, Havekes L. Postprandial lipoprotein metabolism in normolipidemic men with and without coronary artery disease. Arteriosclerosis. 1991;11: Hirano K-I, Yamashita S, Kuga Y, Sakai N, Nozaki S, Kihara S, Arai T, Yanagi K, Takami S, Menju M, et al. Atherosclerotic disease in marked hyperalphalipoproteinemia: combined reduction of cholesteryl ester transfer protein and hepatic triglyceride lipase. Arterioscler Thromb Vasc Biol. 1995;15: Connelly PW, Hegele RA. Hepatic lipase deficiency. Crit Rev Clin Lab Sci. 1998;35: Shohet RV, Vega GL, Anwar A, Cigarroa JE, Grundy SM, Cohen JC Hepatic lipase (LIPC) promoter polymorphism in men with coronary artery disease. Arterioscler Thromb Vasc Biol. 1999;19: Katzel LI, Coon PJ, Busby MJ, Gottlieb SO, Krauss RM, Goldberg AP. Reduced HDL 2 cholesterol subspecies and elevated postheparin hepatic lipase activity in older men with abdominal obesity and asymptomatic myocardial ischemia. Arterioscler Thromb. 1992;12: Zambon A, Deeb SS, Brown BG, Hokanson JE, Brunzell JD. Common hepatic lipase gene promoter variant determines clinical response to intensive lipid-lowering treatment. Circulation. 2001;103: Lamarche B, Tchernoff A, Moorjani S, Cantin B, Dagenais GR, Lupien PJ, Despres JP. Small, dense low-density lipoprotein particles as a predictor of the risk of ischemic heart disease in men. Prospective results from the Quebec Cardiovascular Study. Circulation. 1997;95: Dichek HL, Johnson SM, Akeefe H, Lo GT, Sage E, Yap CE, Mahley RW. Hepatic lipase overexpression lowers remnant and LDL levels by a noncatalytic mechanism in LDL receptor-deficient mice. J Lipid Res. 2001;42: Fan J, Wang J, Bensadoun A, Lauer SJ, Dang Q, Mahley RW, Taylor JM. Overexpression of hepatic lipase in transgenic rabbits leads to a marked reduction of plasma high density lipoproteins and intermediate density lipoproteins. Proc Natl Acad Sci USA. 1994;91: Dichek HL, Brecht W, Fan J, Ji Z-S, McCormick SPA, Akeefe H, Conzo LA, Sanan DA, Weisgraber KH, Young SG, Taylor JM, Mahley RW. Overexpression of hepatic lipase in transgenic mice decreases apolipoprotein B-containing and high-density lipoproteins. J Biol Chem. 1998; 273: Busch SJ, Barnhart RL, Martin GA, Fitzgerald MC, Yates MT, Mao SJT, Thomas CE, Jackson RL. Human hepatic triglyceride lipase expression reduces high density lipoprotein and aortic cholesterol in cholesterol-fed transgenic mice. J Biol Chem. 1994;269: Mezdour H, Jones R, Dengremont C, Castro G, Maeda N. Hepatic lipase deficiency increases plasma cholesterol but reduces susceptibility to atherosclerosis in apolipoprotein E-deficient mice. J Bio. Chem. 1997;272: Nong Z, Gonzalez-Navarro H, Amar M, Freeman L, Knapper C, Neufeld EB, Paigen BJ, Hoyt RF, Fruchart-Najib J, Santamarina-Fojo S. Hepatic lipase expression in macrophages contributes to atherosclerosis in apoedeficient and LCAT-transgenic mice. J Clin Invest. 2003;112: Bergeron N, Kotite L, Verges M, Blanche P, Hamilton RL, Krauss RM, Bensadoun A, Havel RJ. Lamellar lipoproteins uniquely contribute to hyperlipidemia in mice doubly deficient in apolipoprotein E and hepatic lipase. Proc Natl Acad Sci USA. 1998;95: Barbagallo CM, Fan J, Blanche PJ, Rizzo M, Taylor JM, Krauss RM. Overexpression of human hepatic lipase and apoe in transgenic rabbits attenuates response to dietary cholesterol and alters lipoprotein subclass distributions. Arterioscler Thromb Vasc Biol. 1999;19: Rizzo M, Taylor JM, Barbagallo CM, Berneis K, Blanche PJ, Krauss RM. Effects on lipoprotein subclasses of combined expression of human hepatic lipase and human apob in transgenic rabbits. Arterioscler Thromb Vasc Biol. 2004;24: Qiu S, Bergeron N, Kotite L, Krauss RM, Bensadoun A, Havel RJ. Metabolism of lipoproteins containing apolipoprotein B in hepatic lipasedeficient mice. J Lipid Res. 1998;39: Breckenridge WC, Little JA, Alaupovic P, Wang CS, Kuksis A, Kakis G, Lindgren F, Gardiner G. Lipoprotein abnormalities associated with a familial deficiency of hepatic lipase. Atherosclerosis. 1982;45: Hegele RA, Little JA, Vezina C, Maguire GF, Tu L, Wolever TS, Jenkins DJA, Connelly PW. Hepatic lipase deficiency: Clinical, biochemical, and molecular genetic characteristics. Arterioscler Thromb. 1993;13: Carlson LA, Holmquist L, Nilsson-Ehle P. Deficiency of hepatic lipase activity in post-heparin plasma in familial hyper-[alpha]-triglyceridemia. Acta Med Scand. 1986;219: Brand K, Dugi KA, Brunzell JD, Nevin DN, Brewer HBJ, Santamarina-Fojo S. A novel A-G mutation in intron I of the hepatic lipase gene leads to alternative splicing resulting in enzyme deficiency. J Lipid Res. 1996;37: Knudsen P, Antikainen M, Ehnholm S, Uusi-Oukari M, Tenkanen H, Lahdenpera S, Kahri J, Tilly-Kiesi M, Bensadoun A, Taskinen MR, Ehnholm C. A compound heterozygote for hepatic lipase gene mutations Leu334 Phe and Thr383 Met: correlation between hepatic lipase activity and phenotypic expression. J Lipid Res. 1996;37: Brunzell JD, Deeb SS. Familial lipoprotein lipase deficiency, apoc-ii deficiency, and hepatic lipase deficiency. In: Scriver CR, Beaudet AL, Sly WS, Valle D, Childs B, Kinzler KW, Vogelstein B, eds. The Metabolic and Molecular Bases of Inherited Disease. New York, NY: McGraw-Hill; 2001: Ruel IL, Couture P, Gagne C, Deshaies Y, Simard J, Hegele RA, Lamarche B. Characterization of a novel mutation causing hepatic lipase deficiency among French Canadians. J Lipid Res. 2003;44: Homanics GE, De Silva HV, Osada J, Zhang SH, Wong H, Borensztajn J, Maeda N. Mild dyslipidemia in mice following targeted inactivation of the hepatic lipase gene. J Biol Chem. 1995;270: Couture P, Otvos JD, Cupples LA, Lahoz C, Wilson PW, Schaefer EJ, Ordovas JM. Association of the C-514T polymorphism in the hepatic lipase gene with variations in lipoprotein subclass profiles: The Framingham Offspring Study. Arterioscler Thromb Vasc Biol. 2000;20: Cohen JC, Vega GL, Grundy SM. Hepatic lipase: new insights from genetic and metabolic studies. Curr Opin Lipidol. 1999;10: Campos H, Dreon DM, Krauss RM. Associations of hepatic and lipoprotein lipase activities with changes in dietary composition and low-density lipoprotein subclasses. J Lipid Res. 1995;36: Deeb SS, Zambon A, Carr MC, Ayyobi AF, Brunzell JD. Hepatic lipase and dyslipidemia: interactions among genetic variants, obesity, gender, and diet. J Lipid Res. 2003;44: Jansen H, Chu G, Ehnholm C, Dallongeville J, Nicaud V, Talmud PJ. The T allele of the hepatic lipase promoter variant C-480T is associated with increased fasting lipids and HDL and increased preprandial and postprandial LpCIII:B: European Atherosclerosis Research Study (EARS) II. Arterioscler Thromb Vasc Biol. 1999;19: Thuren T. Hepatic lipase and HDL metabolism. Curr Opin Lipidol. 2000;11: Perret B, Mabile L, Martinez L, Terce F, Barbaras R, Collet X Hepatic lipase: structure/function relationship, synthesis, and regulation. J Lipid Res. 2002;43: Connelly PW. The role of hepatic lipase in lipoprotein metabolism. Clin Chim Acta. 1999;286: Olivecrona G, Olivecrona T. Triglyceride lipases and atherosclerosis. Curr Opin Lipidol. 1995;6: Patsch JR, Prasad S, Gotto AMJ, Patsch W. High-density lipoprotein 2. Relationship of the plasma levels of this lipoprotein species to its com-

5 1754 Arterioscler Thromb Vasc Biol. October 2004 position, to the magnitude of postprandial lipemia, and to the activities of lipoprotein lipase and hepatic lipase. J Clin Invest. 1987;80: Guerra R, Wang J, Grundy SM, Cohen JC. A hepatic lipase (LIPC) allele associated with high plasma concentrations of high density lipoprotein cholesterol. Proc Natl Acad Sci USA. 1997;94: Krapp A, Ahle S, Kersting S, Hua Y, Kneser K, Nielsen M, Gliemann J, Beisiegel U. Hepatic lipase mediates the uptake of chylomicrons and -VLDL into cells via the LDL receptor-related protein (LRP). J Lipid Res. 1996;37: Ji Z-S, Lauer SJ, Fazio S, Bensadoun A, Taylor JM, Mahley RW. Enhanced binding and uptake of remnant lipoproteins by hepatic lipasesecreting hepatoma cells in culture. J Biol Chem. 1994;269: Komaromy M, Azhar S, Cooper AD. Chinese hamster ovary cells expressing a cell surface-anchored form of hepatic lipase. J Biol Chem. 1996;271: Diard P, Malewiak M-I, Lagrange D, Griglio S. Hepatic lipase may act as a ligand in the uptake of artificial chylomicron remnant-like particles by isolated rat hepatocytes. Biochem J. 1994;299: Choi SY, Komaromy MC, Chen J, Fong LG, Cooper AD. Acceleration of uptake of LDL but not chylomicrons or chylomicron remnants by cells that secrete apoe and hepatic lipase. J Lipid Res. 1994;35: Shafi S, Brady SE, Bensadoun A, Havel RJ. Role of hepatic lipase in the uptake and processing of chylomicron remnants in rat liver. J Lipid Res. 1994;35: Marques-Vidal P, Azéma C, Collet X, Vieu C, Chap H, Perret B. Hepatic lipase promotes the uptake of HDL esterified cholesterol by the perfused rat liver: A study using reconstituted HDL particles of defined phospholipid composition. J Lipid Res. 1994;35: Ji Z-S, Dichek HL, Miranda RD, Mahley RW. Heparan sulfate proteoglycans participate in hepatic lipase and apolipoprotein E-mediated binding and uptake of plasma lipoproteins, including high density lipoproteins. J Biol Chem. 1997;272: Lambert G, Chase MB, Dugi K, Bensadoun A, Brewer HBJ, Santamarina-Fojo S. Hepatic lipase promotes the selective uptake of high density lipoprotein-cholesteryl esters via the scavenger receptor B1. J Lipid Res. 1999;40: Dugi KA, Amar MJA, Haudenschild CC, Shamburek RD, Bensadoun A, Hoyt RF Jr, Fruchart-Najib J, Madj Z, Brewer HBJ, Santamarina-Fojo S. In vivo evidence for both lipolytic and nonlipolytic function of hepatic lipase in the metabolism of high density lipoproteins. Arterioscler Thromb Vasc Biol. 2000;20: Amar MJA, Dugi KA, Haudenschild CC, Shamburek RD, Foeger B, Chase M, Bensadoun A, Hoyt RF Jr, Brewer HBJ, Santamarina-Fojo S. Hepatic lipase facilitates the selective uptake of cholesteryl esters from remnant lipoproteins in apoe deficient mice. J Lipid Res. 1998;39: Dichek HL, Qian K, Agrawal N. The bridging function of hepatic lipase clears plasma cholesterol in LDL receptor-deficient apob-48-only and apob-100-only mice. J Lipid Res. 2004;45: Zambon A, Deeb SS, Bensadoun A, Foster KE, Brunzell JD. In vivo evidence of a role for hepatic lipase in human apob-containing lipoprotein metabolism, independent of its lipolytic activity. J Lipid Res. 2000;41: Gonzalez-Navarro H, Nong Z, Amar MJA, Freeman L, Knapper C, Shamburek R, Paigen BJ, Brewer HB Jr, Santamarina-Fojo S. In vivo evidence the HL modulates development of atherosclerosis in transgenic mice that express catalytically inactive hepatic lipase. Circulation. 2003; 108:IV Gonzalez-Navarro H, Nong Z, Freeman L, Bensadoun A, Peterson K, Santamarina-Fojo S. Identification of mouse and human macrophages as a site of synthesis of hepatic lipase. J Lipid Res. 2002;43: Babaev VR, Patel MB, Semenkovich CF, Fazio S, Linton MF. Macrophage lipoprotein lipase promotes foam cell formation and atherosclerosis in low density lipoprotein receptor-deficient mice. J Biol Chem. 2000; 34: van Eck M, Zimmermann R, Groot PHE, Zechner R, Van Berkel TJC. Role of macrophage-derived lipoprotein lipase in lipoprotein metabolism and atherosclerosis. Arterioscler Thromb Vasc Biol. 2000;20:e53 e Saxena U, Klein MG, Vanni TM, Goldberg IJ. Lipoprotein lipase increases low density lipoprotein retention by subendothelial cell matrix. J Clin Invest. 1992;89: Saxena U, Kulkarni NM, Ferguson E, Newton RS. Lipoprotein lipasemediated lipolysis of very low density lipoproteins increases monocyte adhesion to aortic endothelial cells. Biochem Biophys Res Commun. 1992;189: Aviram M, Bierman EL, Chait A. Modification of low-density lipoprotein by lipoprotein lipase or hepatic lipase induces enhanced uptake and cholesterol accumulation in cells. J Biol Chem. 1988;263: Shiffman D, Mikita T, Tai JTN, Wade DP, Porter JG, Seilhamer JJ, Somogyi R, Liang S, Lawn RM Large-scale gene expression analysis of cholesterol-loaded macrophages. J Biol Chem. 2000;275: Mikita T, Porter G, Lawn RM, Shiffman D Oxidized low-density lipoprotein exposure alters the transcriptional response of macrophages to inflammatory stimulus. J Biol Chem. 2001;276: Andersson T, Unneberg P, Nilsson P, Odeberg J, Quackenbush J, Lundeberg J. Monitoring of representational difference analysis subtraction procedures by global microarrays. Biotechniques. 2002;32: Breedveld B, Schoonderwoerd K, Verhoeven AJM, Willemsen R, Jansen H. Hepatic lipase is localized at the parenchymal cell microvilli in rat liver. Biochem J. 1997;321: Sanan DA, Fan J, Bensadoun A, Taylor JM. Hepatic lipase is abundant on both hepatocyte and endothelial cell surfaces in the liver. J Lipid Res. 1997;38: Yu KC-W, David C, Kadambi SJ, Stahl A, Hirata K-I, Ishida T, Quertermous T, Cooper AD, Choi SY Endothelial lipase is synthesized by hepatic and aorta endothelial cells and its expression is altered in apoe-deficient mice. J Lipid Res. 2004;Epub ahead of print; June 8, 2004.