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Abstract
Plasma levels of high-density lipoprotein (HDL) cholesterol and its major protein, apolipoprotein A-I, are inversely correlated with the incidence of atherosclerotic cardiovascular disease. Low HDL cholesterol and apolipoprotein A-I levels often are found in association with other cardiovascular risk factors, including the metabolic syndrome, insulin resistance, and type 2 diabetes mellitus. However, overexpression of apolipoprotein A-I in animals has been shown to reduce progression and even induce regression of atherosclerosis, indicating that apolipoprotein A-I is directly protective against atherosclerosis. A major mechanism by which apolipoprotein A-I inhibits atherosclerosis may be by promoting cholesterol efflux from macrophages and returning it to the liver for excretion, a process termed reverse cholesterol transport. This article focuses on new developments in the regulation of reverse cholesterol transport and the clinical implications of those developments.
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Affiliation(s)
- Daniel J Rader
- Preventive Cardiology/Lipid Research Center, University of Pennsylvania Health System, Philadelphia, Pennsylvania 19104, USA.
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52
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Mahaney MC, Almasy L, Rainwater DL, VandeBerg JL, Cole SA, Hixson JE, Blangero J, MacCluer JW. A quantitative trait locus on chromosome 16q influences variation in plasma HDL-C levels in Mexican Americans. Arterioscler Thromb Vasc Biol 2003; 23:339-45. [PMID: 12588781 DOI: 10.1161/01.atv.0000051406.14162.6a] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE We conducted a whole-genome, multipoint linkage screen to localize a previously reported major locus accounting for 56% to 67% of the additive genetic effects on covariate-adjusted plasma HDL cholesterol (HDL-C) levels in Mexican Americans from the San Antonio Family Heart Study (SAFHS). METHODS AND RESULTS After using complex segregation analysis to recover the major locus in 472 SAFHS participants from 10 genotyped families, we incorporated covariates required to detect that major locus, including plasma levels of triglycerides and apolipoprotein A-I, in a maximum-likelihood-based variance-components linkage screen. Only chromosome 16 exhibited convincing evidence for a quantitative trait locus (QTL), with a peak multipoint log of the odds (LOD)=3.73 (P=0.000034). Subsequent penetrance model-based linkage analysis, incorporating genotypes at the marker locus nearest the multipoint peak (D16S518) into the segregation model, detected linkage with the previously detected major locus (LOD=2.73, P=0.000642). Initial estimates place this QTL within a 15-cM region of chromosome 16q near the structural loci for lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP). CONCLUSIONS A QTL influencing plasma levels of HDL-C in Mexican Americans from San Antonio maps to a region of human chromosome 16q near LCAT and CETP.
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Affiliation(s)
- M C Mahaney
- Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, TX 78245-0549, USA.
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53
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Hannuksela ML, Brousseau ME, Meyn SM, Nazih H, Bader G, Shamburek RD, Alaupovic P, Brewer HB. In vivo metabolism of apolipoprotein E within the HDL subpopulations LpE, LpE:A-I, LpE:A-II and LpE:A-I:A-II. Atherosclerosis 2002; 165:205-20. [PMID: 12417271 DOI: 10.1016/s0021-9150(02)00200-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-density lipoproteins can be separated into distinct particles based on their apolipoprotein content. In the present study, the in vivo metabolism of apoE within the apoE-containing HDL particles LpE, LpE:A-I, LpE:A-II and LpE:A-I:A-II was assessed in control subjects and in patients with abetalipoproteinemia (ABL), in whom HDL are the sole plasma lipoproteins. The metabolism of apoE within these HDL subspecies was investigated in three separate studies which differed by donor or recipient status: (1) particles purified from normolipidemic plasma and reassociated with 125I or 131I-labeled apoE injected into normolipidemic subjects (study 1); (2) particles purified from ABL plasma injected into normolipidemic subjects (study 2); and (3) particles purified from ABL plasma injected into ABL subjects (study 3). The plasma residence times (RT, hours) in study 1 were 14.3+/-2.9, 11.3+/-3.4, and 9.1+/-1.2 for apoE within LpE:A-I:A-II, LpE:A-II and LpE:A-I, respectively, while those in study 2 were 10.1+/-2.2, 9.7+/-2.4, 7.9+/-1.0 and 7.3+/-0.8 for apoE within LpE:A-I:A-II, LpE:A-II, LpE:A-I and LpE, respectively. In study 3, RTs for apoE within LpE:A-I:A-II and LpE were 8.7+/-0.9 and 6.8+/-0.9, respectively. In comparison, RT for apoA-I on LpA-I:A-II has been reported to be 124.1+/-5.5 h and that for apoA-I on LpA-I 105.8+/-6.2 h. Thus, apoE within the different apoE-containing HDL particles was metabolized rapidly and at a similar rate in control and ABL subjects. The plasma RT of apoE was longest when injected on LpE:A-I:A-II particles and shortest when injected on LpE. In summary, our data show that: (1) the plasma RT of apoE within HDL is approximately ten times shorter than that of apoA-I within HDL, and (2) apoE within HDL is metabolized at a slower rate when apoproteins A-I and A-II are present (LpE:A-I:A-II RT>LpE:A-II>LpE:A-I>LpE). These differences were related to the lipid and apolipoprotein composition of the HDL subspecies, and, in control subjects, to the transfer of apoE from HDL subspecies to apoB-containing lipoproteins as well.
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Affiliation(s)
- Minna L Hannuksela
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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54
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Choi SY, Hirata KI, Ishida T, Quertermous T, Cooper AD. Endothelial lipase: a new lipase on the block. J Lipid Res 2002; 43:1763-9. [PMID: 12401876 DOI: 10.1194/jlr.r200011-jlr200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Endothelial lipase (EL) is a newly described member of the triglyceride lipase gene family. It has a considerable molecular homology with lipoprotein lipase (LPL) (44%) and hepatic lipase (HL) (41%). Unlike LPL and HL, this enzyme is synthesized by endothelial cells and functions at the site where it is synthesized. Furthermore, its tissue distribution is different from that of LPL and HL. As a lipase, EL has primarily phospholipase A1 activity. Animals that overexpress EL showed reduced HDL cholesterol levels. Conversely, animals that are deficient in EL showed a marked elevation in HDL cholesterol levels, suggesting that it plays a physiologic role in HDL metabolism. Unlike LPL and HL, EL is located in the vascular endothelial cells and its expression is highly regulated by cytokines and physical forces, suggesting that it may play a role in the development of atherosclerosis. However, there is only a limited amount of information available about this enzyme. Some of our unpublished data in addition to previously published data support the possibility that the enzyme plays a role in the formation of atherosclerotic lesion.
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Affiliation(s)
- Sungshin Y Choi
- Palo Alto Medical Foundation, Research Institute, Palo Alto, CA 94301, USA.
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55
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Webb NR, Cai L, Ziemba KS, Yu J, Kindy MS, van der Westhuyzen DR, de Beer FC. The fate of HDL particles in vivo after SR-BI-mediated selective lipid uptake. J Lipid Res 2002; 43:1890-8. [PMID: 12401888 DOI: 10.1194/jlr.m200173-jlr200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Scavenger receptor class B type I (SR-BI) delivers cholesterol ester from HDL to cells via a selective uptake mechanism, whereby lipid is transferred from the core of the particle without concomitant degradation of the protein moiety. The precise metabolic fate of HDL particles after selective lipid uptake is not known. To characterize SR-BI-mediated HDL processing in vivo, we expressed high levels of this receptor in livers of apoA-I(-/-) mice by adenoviral vector gene transfer, and then injected the mice with a bolus of human HDL(2) traced with (125)I-dilactitol tyramine. HDL recovered from apoA-I(-/-) mice over-expressing SR-BI was significantly smaller than HDL recovered from control mice as measured by non-denaturing gel electrophoresis. When injected into C57BL/6 mice, these HDL "remnants" were rapidly converted to HDL(2)-sized lipoprotein particles, and were cleared from the plasma at a rate similar to HDL(2). In assays in cultured cells, HDL remnants did not stimulate ATP-binding cassette transporter A1-dependent cholesterol efflux. When mixed with mouse plasma ex vivo, HDL remnants rapidly converted to larger HDL particles. These studies identify a previously ill-defined pathway in HDL metabolism, whereby SR-BI generates small, dense HDL particles that are rapidly remodeled in plasma. This remodeling pathway may represent a process that is important in determining the rate of apoA-I catabolism and HDL-mediated reverse cholesterol transport.
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Affiliation(s)
- Nancy R Webb
- Department of Internal Medicine, University of Kentucky Medical Center, Lexington, Kentucky 40536, USA.
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56
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Abstract
Apolipoprotein (Apo) A-I and apo A-II are the major apolipoproteins of HDL. It is clearly demonstrated that there are inverse relationships between HDL-cholesterol and apo A-I plasma levels and the risk of coronary heart disease (CHD) in the general population. On the other hand, it is still not clearly demonstrated whether apo A-II plasma levels are associated with CHD risk. A recent prospective epidemiological (PRIME) study suggests that Lp A-I (HDL containing apo A-I but not apo A-II) and Lp A-I:A-II (HDL containing apo A-I and apo A-II) were both reduced in survivors of myocardial infarction, suggesting that both particles are risk markers of CHD. Apo A-II and Lp A-I:A-II plasma levels should be rather related to apo A-II production rate than to apo A-II catabolism. Mice transgenic for both human apo A-I and apo A-II are less protected against atherosclerosis development than mice transgenic for human apo A-I only, but the results of the effects of trangenesis of human apo A-II (in the absence of a co-transgenesis of human apo A-I) are controversial. It is highly suggested that HDL reduce CHD risk by promoting the transfer of peripherical free cholesterol to the liver through the so-called 'reverse cholesterol transfer'. Apo A-II modulates different steps of HDL metabolism and therefore probably alters reverse cholesterol transport. Nevertheless, some effects of apo A-II on intermediate HDL metabolism might improve reverse cholesterol transport and might reduce atherosclerosis development while some other effects might be deleterious. In different in vitro models of cell cultures, Lp A-I:A-II induce either a lower or a similar cellular cholesterol efflux (the first step of reverse cholesterol transport) than Lp A-I. Results depend on numerous factors such as cultured cell types and experimental conditions. Furthermore, the effects of apo A-II on HDL metabolism, beyond cellular cholesterol efflux, are also complex and controversial: apo A-II may inhibit lecithin-cholesterol acyltransferase (LCAT) (potential deleterious effect) and cholesteryl-ester-transfer protein (CETP) (potential beneficial effect) activities, but may increase the hepatic lipase (HL) activity (potential beneficial effect). Apo A-II may also inhibit the hepatic cholesteryl uptake from HDL (potential deleterious effect) probably through the SR-BI depending pathway. Therefore, in terms of atherogenesis, apo A-II alters the intermediate HDL metabolism in opposing ways by increasing (LCAT, SR-BI) or decreasing (HL, CETP) the atherogenicity of lipid metabolism. Effects of apo A-II on atherogenesis are controversial in humans and in transgenic animals and probably depend on the complex effects of apo A-II on these different intermediate metabolic steps which are in weak equilibrium with each other and which can be modified by both endogenous and environmental factors. It can be suggested that apo A-II is not a strong determinant of lipid metabolism, but is rather a modulator of reverse cholesterol transport.
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Affiliation(s)
- Anne Tailleux
- Faculté de Pharmacie, Département d'athérosclérose et INSERM U 545, Institut Pasteur, Université Lille 2, 1, rue du Professeur Calmette, 59019 Cedex, Lille, France.
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57
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Oka T, Yamashita S, Kujiraoka T, Ito M, Nagano M, Sagehashi Y, Egashira T, Nanjee MN, Hirano KI, Miller NE, Matsuzawa Y, Hattori H. Distribution of human plasma PLTP mass and activity in hypo- and hyperalphalipoproteinemia. J Lipid Res 2002. [DOI: 10.1194/jlr.m100349-jlr200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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58
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Abstract
Plasma levels of high-density lipoprotein (HDL) cholesterol are strongly inversely associated with atherosclerotic cardiovascular disease, and overexpression of HDL proteins, such as apolipoprotein A-I in animals, reduces progression and even induces regression of atherosclerosis. Therefore, HDL metabolism is recognized as a potential target for therapeutic intervention of atherosclerotic vascular diseases. The antiatherogenic properties of HDL include promotion of cellular cholesterol efflux and reverse cholesterol transport, as well as antioxidant, anti-inflammatory and anticoagulant properties. The molecular regulation of HDL metabolism is not fully understood, but it is influenced by several extracellular lipases. Here, we focus on new developments and insights into the role of secreted lipases on HDL metabolism and their relationship to atherosclerosis.
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Affiliation(s)
- Weijun Jin
- University of Pennsylvania School of Medicine, 654 BRB II/III, 421 Curie Blvd, Philadelphia, PA 19104, USA
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59
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Bérard AM, Clerc M, Brewer B, Santamarina-Fojo S. A normal rate of cellular cholesterol removal can be mediated by plasma from a patient with familial lecithin-cholesterol acyltransferase (LCAT) deficiency. Clin Chim Acta 2001; 314:131-9. [PMID: 11718688 DOI: 10.1016/s0009-8981(01)00689-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Lecithin-cholesterol acyltransferase (LCAT) is the major enzyme involved in the esterification of cholesterol in circulating plasma lipoproteins. In the present study, we describe the molecular defects in the LCAT gene and in lipoprotein metabolism of a 34-year-old patient presenting with features of classic familial LCAT deficiency. DNA sequencing revealed two separate point mutations in exon 3 of the patient's LCAT gene: a C to A substitution converting Tyr(83) to a Stop and a C to T transition converting an Arg(99) to a Cys. Digestion of patient PCR-amplified DNA with the restriction enzymes AccI and AciI established that the patient was a compound heterozygote for both mutations. In vitro expression of LCAT (Arg(99)-->Cys) in human embryonic kidney-293 cells demonstrated reduced expression, as well as reduced secretion and/or increased intracellular degradation of the mutant enzyme with significantly decreased alpha-LCAT specific activity, thus, establishing the functional significance of the LCAT (Arg(99)-->Cys) mutation. The plasma cholesterol esterification rate (CER, 2+/-0.3 nmol/ml/h), alpha-LCAT activity (2.9+/-0.1 nmol/ml/h) and LCAT concentration (0.3+/-0.1 microg/ml) were 2.9%, 2.3% and 6.1% that of normal subjects, respectively. Analysis of the patient's plasma lipid profile revealed reduced plasma concentrations of total cholesterol (111+/-0.5 mg/dl), HDL cholesterol (1.6+/-0.2 mg/dl), apolipoprotein (apo) A-I (52+/-4 mg/dl) and apo A-II (11+/-0.5 mg/dl). Nevertheless, for the first time, we demonstrate that the LCAT-deficient plasma is as efficient as control plasma in cholesterol efflux experiments performed with [(3)H]-cholesterol loaded fibroblasts. This result could explain the absence of premature atherosclerosis in this LCAT-deficient patient.
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Affiliation(s)
- A M Bérard
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1666, USA.
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60
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Rosset J, Wang J, Wolfe BM, Dolphin PJ, Hegele RA. Lecithin:cholesterol acyl transferase G30S: association with atherosclerosis, hypoalphalipoproteinemia and reduced in vivo enzyme activity. Clin Biochem 2001; 34:381-6. [PMID: 11522275 DOI: 10.1016/s0009-9120(01)00231-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES A 69 yr old male was referred for assessment of a very low plasma HDL cholesterol and apolipoprotein AI concentration. At age 65, he had undergone triple vessel coronary bypass graft surgery. He had a strong family history of early coronary heart disease. We analyzed the molecular basis of his clinical and biochemical abnormalities. DESIGN AND METHODS We used DNA sequencing to determine whether mutations in LCAT were present. We also evaluated plasma biochemistry and LCAT activity. RESULTS DNA sequencing revealed that the patient was a heterozygote for the G30S mutation in the gene encoding lecithin:cholesteol acyl transferase (LCAT). His plasma was found to have half-normal LCAT activity. CONCLUSIONS The findings in this patient suggest that rare dysfunctional mutations in candidate genes, such as LCAT, can contribute to the spectrum of patients ascertained because of low HDL cholesterol.
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Affiliation(s)
- J Rosset
- The John P. Robarts Research Institute and Department of Medicine, University of Western Ontario, London, Ontario, Canada
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61
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HDL modification by secretory phospholipase A2 promotes scavenger receptor class B type I interaction and accelerates HDL catabolism. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31979-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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62
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Santamarina-Fojo S, Lambert G, Hoeg JM, Brewer HB. Lecithin-cholesterol acyltransferase: role in lipoprotein metabolism, reverse cholesterol transport and atherosclerosis. Curr Opin Lipidol 2000; 11:267-75. [PMID: 10882342 DOI: 10.1097/00041433-200006000-00007] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the past several years significant advances have been made in our understanding of lecithin-cholesterol acyltransferase (LCAT) function. LCAT beneficially alters the plasma concentrations of apolipoprotein B-containing lipoproteins, as well as HDL. In addition, its proposed role in facilitating reverse cholesterol transport and modulating atherosclerosis has been demonstrated in vivo. Analysis of LCAT transgenic animals has established the importance of evaluating HDL function, as well as HDL plasma levels, to predict atherogenic risk.
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Affiliation(s)
- S Santamarina-Fojo
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institute of Health, Bethesda, Maryland, USA.
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63
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Rader DJ, Maugeais C. Genes influencing HDL metabolism: new perspectives and implications for atherosclerosis prevention. MOLECULAR MEDICINE TODAY 2000; 6:170-5. [PMID: 10740256 DOI: 10.1016/s1357-4310(00)01673-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Atherosclerotic cardiovascular disease (ASCVD) is the most common cause of morbidity and mortality in Western societies. Current therapies, such as reduction of plasma cholesterol, significantly reduce, but do not come close to eliminating, the complications of ASCVD. Therefore, novel therapeutic approaches to the prevention of acute coronary events and progression of atherosclerosis are still needed. The complex metabolism of high density lipoproteins represents an attractive potential target for therapeutic intervention. Here, we will discuss those components of the high density lipoprotein metabolism and lipid transport pathways that are potential preventative or therapeutic targets for ASCVD.
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Affiliation(s)
- D J Rader
- University of Pennsylvania Medical Center, 614 BRBII/III 421 Curie Blvd., Philadelphia, PA 19104, USA.
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64
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Clay MA, Pyle DH, Rye KA, Barter PJ. Formation of spherical, reconstituted high density lipoproteins containing both apolipoproteins A-I and A-II is mediated by lecithin:cholesterol acyltransferase. J Biol Chem 2000; 275:9019-25. [PMID: 10722751 DOI: 10.1074/jbc.275.12.9019] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have provided detailed information on the formation of spherical high density lipoproteins (HDL) containing apolipoprotein (apo) A-I but no apoA-II (A-I HDL) by an lecithin:cholesterol acyltransferase (LCAT)-mediated process. In this study we have investigated the formation of spherical HDL containing both apoA-I and apoA-II (A-I/A-II HDL). Incubations were carried out containing discoidal A-I reconstituted HDL (rHDL), discoidal A-II rHDL, and low density lipoproteins in the absence or presence of LCAT. After the incubation, the rHDL were reisolated and subjected to immunoaffinity chromatography to determine whether A-I/A-II rHDL were formed. In the absence of LCAT, the majority of the rHDL remained as either A-I rHDL or A-II rHDL, with only a small amount of A-I/A-II rHDL present. By contrast, when LCAT was present, a substantial proportion of the reisolated rHDL were A-I/A-II rHDL. The identity of the particles was confirmed using apoA-I rocket electrophoresis. The formation of the A-I/A-II rHDL was influenced by the relative concentrations of the precursor discoidal A-I and A-II rHDL. The A-I/A-II rHDL included several populations of HDL-sized particles; the predominant population having a Stokes' diameter of 9.9 nm. The particles were spherical in shape and had an electrophoretic mobility slightly slower than that of the alpha-migrating HDL in human plasma. The apoA-I:apoA-II molar ratio of the A-I/A-II rHDL was 0.7:1. Their major lipid constituents were phospholipids, unesterified cholesterol, and cholesteryl esters. The results presented are consistent with LCAT promoting fusion of the A-I rHDL and A-II rHDL to form spherical A-I/A-II rHDL. We suggest that this process may be an important source of A-I/A-II HDL in human plasma.
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Affiliation(s)
- M A Clay
- The University of Adelaide, Department of Medicine, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000, Australia.
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65
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Dobiásová M, Frohlich JJ. Advances in understanding of the role of lecithin cholesterol acyltransferase (LCAT) in cholesterol transport. Clin Chim Acta 1999; 286:257-71. [PMID: 10511297 DOI: 10.1016/s0009-8981(99)00106-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We review the structure and function of lecithin cholesterol acyl transferase (LCAT), the advances in the studies of molecular genetics of LCAT and its deficiency states as well as the developments in assessment of LCAT activity particularly the concept of measurement of fractional esterification rate of plasma cholesterol in the absence of apoB lipoproteins (FER(HDL)) as an indication of atherogenic risk. We discuss LCAT reaction from two points of view: one that is consistent with the general belief in LCAT antiatherogenic potential and another, namely, a proposed concept of potentially opposing roles of LCAT in normal and dyslipidemic plasmas. While other plasma lipoproteins can (in addition to HDL) provide unesterified cholesterol (UC) for LCAT reaction, HDL may play an unique role in trafficking of newly formed cholesteryl esters (CE) rather than as a primary acceptor of cellular cholesterol. Thus, the plasma HDL, specifically the larger (HDL2b) particles, direct the efflux of most of (LCAT produced) CE to its specific catabolic sites rather than to potentially atherogenic VLDLs and back to LDLs.
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Affiliation(s)
- M Dobiásová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague
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66
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Targeted disruption of the murine lecithin:cholesterol acyltransferase gene is associated with reductions in plasma paraoxonase and platelet-activating factor acetylhydrolase activities but not in apolipoprotein J concentration. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33489-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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67
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Davit-Spraul A, Atger V, Pourci M, Hadchouel M, Legrand A, Moatti N. Cholesterol efflux from Fu5AH cells to the serum of patients with Alagille syndrome: importance of the HDL-phospholipids/free cholesterol ratio and of the HDL size distribution. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33373-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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68
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Navab M, Hama SY, Hough GP, Hedrick CC, Sorenson R, La Du BN, Kobashigawa JA, Fonarow GC, Berliner JA, Laks H, Fogelman AM. High density associated enzymes: their role in vascular biology. Curr Opin Lipidol 1998; 9:449-56. [PMID: 9812199 DOI: 10.1097/00041433-199810000-00009] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Enzymes associated with circulating HDL include lecithin: cholesterol acyl transferase, phospholipid transfer protein, cholesterol ester transfer protein, paraoxonase 1 and platelet activating factor acetylhydrolase. Together with lipoprotein lipase and hepatic lipase these enzymes produce important lipoprotein remodeling and modulate their structure and function and therefore their role in artery wall metabolism.
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Affiliation(s)
- M Navab
- Cardiology and Cardio-thoracic Surgery, University of California, Los Angeles 90095-1679, USA
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69
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Affiliation(s)
- A Jonas
- Department of Biochemistry, College of Medicine at Urban-Champaign, University of Illinois 61801, USA
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70
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Correction of hypoalphalipoproteinemia in LDL receptor-deficient rabbits by lecithin:cholesterol acyltransferase. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32184-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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71
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Cirera S, Julve J, Ferrer I, Mainou C, Bonet R, Martin-Campos JM, González-Sastre F, Blanco-Vaca F. Molecular diagnosis of lecithin: cholesterol acyltransferase deficiency in a presymptomatic proband. Clin Chem Lab Med 1998; 36:443-8. [PMID: 9746267 DOI: 10.1515/cclm.1998.074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We report the molecular diagnosis of a lecithin : cholesterol acyltransferase deficiency in a 12-year old proband with a high-density lipoprotein deficiency. The increased percentage of free cholesterol in plasma and high-density lipoprotein indicated an inherited lecithin : cholesterol acyltransferase deficiency as the underlying cause. This diagnosis was confirmed by a low plasma lecithin : cholesterol acyltransferase activity and a combination of genetic analyses which demonstrated compound heterozygosity for two mutations in the lecithin : cholesterol acyltransferase gene of the proband. One was a previously unreported 2 bp deletion leading to a stop signal in codon 77 and the other a point mutation causing Arg 135-->Gln transition. To our knowledge, this is the first diagnosis of lecithin : cholesterol acyltransferase deficiency in a pre-symptomatic patient. Whether the proband will develop signs of complete lecithin : cholesterol acyltransferase deficiency or the milder form (Fish Eye Disease) is uncertain, although the former possibility is more likely. The risk of premature atherosclerosis conferred by lecithin : cholesterol acyltransferase deficiency is not well established. The proband will need to be carefully monitored in the future.
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Affiliation(s)
- S Cirera
- Servei de Bioquímica, Institut de Recerca, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
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72
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de Beer FC, de Beer MC, van der Westhuyzen DR, Castellani LW, Lusis AJ, Swanson ME, Grass DS. Secretory non-pancreatic phospholipase A2: influence on lipoprotein metabolism. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)34937-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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73
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74
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Pont F, Duvillard L, Maugeais C, Athias A, Perségol L, Gambert P, Vergès B. Isotope ratio mass spectrometry, compared with conventional mass spectrometry in kinetic studies at low and high enrichment levels: application to lipoprotein kinetics. Anal Biochem 1997; 248:277-87. [PMID: 9177755 DOI: 10.1006/abio.1997.2130] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The aim of the present study was to compare the performances of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) in stable isotope kinetic studies. In the analysis of cholesterol and leucine, GC/C/IRMS gave precise and linear results over a large scale of 13C enrichment (-22 to +760 delta/1000 for cholesterol, -26 to +600 delta/1000 for leucine). Compared with GC/MS, GC/C/IRMS was much more accurate and reproducible, especially at low [13C]-cholesterol enrichment (-12 delta/1000), with cholesterol samples ranging from 0.11 to 17 ng. Cholesterol ester kinetics in rabbit plasma low-density lipoproteins was studied after injection of 3 mg [3,4-(13)C]cholesterol. A smooth and regular kinetic curve was obtained with GC/C/IRMS; results were much less reproducible with GC/MS. Finally, the performances of GC/C/IRMS were demonstrated in the simultaneous kinetic study of three human plasma apolipoproteins during a primed constant infusion of 0.7 mg.kg-1.h-1 L-[l-13C]leucine. Kinetic curves were obtained in very-low-density lipoproteins and low-density lipoproteins for apolipoprotein B100, and in high-density lipoproteins for apolipoproteins AI and AIL.
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Affiliation(s)
- F Pont
- Laboratoire de Biochimie des Lipoprotéines, INSERM CJF 93-10, Faculté de Médecine, Dijon, France
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75
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Elkhalil L, Majd Z, Bakir R, Perez-Mendez O, Castro G, Poulain P, Lacroix B, Duhal N, Fruchart JC, Luc G. Fish-eye disease: structural and in vivo metabolic abnormalities of high-density lipoproteins. Metabolism 1997; 46:474-83. [PMID: 9160810 DOI: 10.1016/s0026-0495(97)90180-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Fish-eye disease (FED) in humans is characterized by corneal opacities and markedly decreased plasma concentrations of high-density lipoprotein (HDL) cholesterol, apolipoprotein (apo) AI, and apo All, but no tendency to precocious atherosclerosis is present. To elucidate this paradox, the structure of HDL, the potential of serum to promote cholesterol efflux from cultured cells, and the in vivo metabolism of HDL were examined in a 53-year-old woman with a FED syndrome in association with a markedly decreased lecithin:cholesterol acyltransferase (LCAT) activity in HDL due to a mutation of the LCAT gene (Arg158 --> Cys). HDLs isolated by ultracentrifugation were small and enriched in unesterified cholesterol and phospholipids at the expense of cholesteryl esters and proteins. The apolipoprotein content showed an enrichment in apo E and apo AIV, whereas apo AI and apo All were dramatically reduced. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using specific antibodies showed that the apo E was free or covalently bound to apo All. These particles analyzed by electron microscopy were small and round lipoproteins with a size similar to the smallest fraction of normal HDL3. The potential capacity of the serum to promote efflux from the cells was approximately 40% of control serum levels, but FED HDLs were as efficient as control HDLs in promoting cholesterol efflux from cells. To assess the metabolism of HDL apolipoproteins, in vivo apolipoprotein kinetic studies were performed using endogenous labeling techniques in the patient with FED and three control subjects. All subjects were administered D3-labeled leucine by primed constant infusion for up to 10 hours. The fractional synthetic rates (FSRs) of apo AI and apo All in the patient were 0.674 and 0.594 per day, clearly higher than in controls, 0.210 +/- 0.053 and 0.148 +/- 0.014 per day for apo AI and apo All, respectively. Apo AI and apo All production rates in the patient with FED were normal, 11.32 and 2.62 mg/kg x d, respectively, as compared with those in normal subjects, 11.45 +/- 1.23 and 2.68 +/- 0.17 mg/kg x d. These data established that hypoalphalipoproteinemia in FED was caused by marked hypercatabolism of apo AI and apo All. This hypercatabolism could be the consequence of structural abnormalities due to the selective LCAT deficiency. In conclusion, two steps of reverse cholesterol transport, cholesterol efflux and apo-HDL metabolism, appeared particularly efficient. This efficiency could participate in the absence of premature atherosclerosis in FED patients as regards the low HDL level.
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Affiliation(s)
- L Elkhalil
- Departement de Recherches sur l'Atherosclerose, Institute National de la Sante et de la Recherche Medical (INSERM) U325, Institut Pasteur de Lille, France
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76
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Tilly-Kiesi M, Packard CJ, Kahri J, Ehnholm C, Shepherd J, Taskinen MR. In vivo metabolism of apo A-I and apo A-II in subjects with apo A-I(Lys107-->0) associated with reduced HDL cholesterol and Lp(AI w AII) deficiency. Atherosclerosis 1997; 128:213-22. [PMID: 9050778 DOI: 10.1016/s0021-9150(96)05992-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Apolipoprotein A-I (apo A-I) and apolipoprotein A-II (apo A-II) represent 80 90% of the protein content of high density lipoproteins (HDL). Previously we have identified a Finnish family with an apo A-I variant (Lys107-->0) associated with reduced plasma HDL cholesterol level and decreased lipoprotein (Lp)(AI w AII) concentration compared to unaffected family members. To determine the in vivo metabolism of apo A-I and apo A-II in the carriers of apo A-I (Lys107-->0) variant we radioiodinated normal apo A-I with 125I and apo A-II with 131I and compared the kinetic data of two heterozygous apo A-I(Lysl07-->0) patients (HDL cholesterol leves 0.31 and 0.69 mmol/l) to that of eight normolipidemic, healthy control subjects. Plasma radioactivity curves of 125I-labelled normal apo A-I of the patients demonstrated accelerated clearance of apo A-I compared to control subjects. In the two patients the fractional catabolic rates (FCR) of apo A-I were 0.347/day and 0.213/day, respectively, while the mean FCR of apo A-I of the control subjects was 0.151 +/- 0.041/day. Similarly, the plasma decay curves of the 131I-labelled apo A-II showed more rapid clearance of apo A-II in the two patients than in control subjects. The FCR of apo A-II in the two patients were 0.470/day and 0.234/day, while the mean FCR of apo A-II in control subjects was 0.154 +/- 0.029/day. The calculated production rates of apo A-I were similar in patients and in control subjects, and the production rates of apo A-II were significantly higher in patients than in control subjects. Our results show that the Lp(AI w AII) deficiency in patients with the apo A-I(Lys107-->0) is associated with increased fractional catabolic rates of normal apo A-I and apo A-II, while the production rates of these apolipoproteins are normal (apo A-I) or slightly increased (apo A-II).
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Affiliation(s)
- M Tilly-Kiesi
- Department of Medicine, Helsinki University Central Hospital, Finland
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77
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Kuivenhoven JA, Pritchard H, Hill J, Frohlich J, Assmann G, Kastelein J. The molecular pathology of lecithin:cholesterol acyltransferase (LCAT) deficiency syndromes. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)37433-2] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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78
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Leren TP, Bakken KS, Daum U, Ose L, Berg K, Assmann G, von Eckardstein A. Heterozygosity for apolipoprotein A-I(R160L)Oslo is associated with low levels of high density lipoprotein cholesterol and HDL-subclass LpA-I/A-II but normal levels of HDL-subclass LpA-I. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)37281-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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79
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Séguret-Macé S, Latta-Mahieu M, Castro G, Luc G, Fruchart JC, Rubin E, Denèfle P, Duverger N. Potential gene therapy for lecithin-cholesterol acyltransferase (LCAT)-deficient and hypoalphalipoproteinemic patients with adenovirus-mediated transfer of human LCAT gene. Circulation 1996; 94:2177-84. [PMID: 8901669 DOI: 10.1161/01.cir.94.9.2177] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Overexpression of human lecithin-cholesterol acyltransferase (LCAT) in transgenic mice results in an increase of the antiatherogenic HDLs. METHODS AND RESULTS To investigate the potential use of LCAT for gene therapy, a recombinant adenovirus was constructed in which the human LCAT cDNA was expressed under the control of the human cytomegalovirus immediate/early promoter followed by a chimeric intron (AdCMV human LCAT). Human apolipoprotein (apo) A-I transgenic mice infected with AdCMV human LCAT by intravenous injection accumulated reactive LCAT in the plasma. LCAT activity was increased 201-fold in the plasma of mice infected with 1 x 10(6) pfu AdCMV human LCAT, from 45 +/- 2 to 9068 +/- 812 nmol.mL-1.h-1, in comparison with basal LCAT activity measured in control mice, 5 days after injection. Plasma HDL cholesterol levels rose from 117 +/- 12 to 797 +/- 48 mg/dL, and plasma human apo A-I concentrations increased from 247 +/- 14 to 616 +/- 17 mg/dL, in AdCMV human LCAT infected mice compared with control mice. HDL particles were larger and had a different electrophoretic mobility. Studies of cholesterol efflux by incubation of serum with cholesterol-loaded Fu5AH cells showed that serum from AdCMV human LCAT-infected mice promoted a significantly higher efflux than did that of the controls. CONCLUSIONS These data establish the potential of this approach for treatment of subjects with LCAT gene defects as well as patients with low plasma levels of apo A-I and HDL cholesterol.
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Affiliation(s)
- S Séguret-Macé
- Rhône-Poulenc Rorer, Gencell Division, Centre de recherche de Vitry-Alfortville, Vitry sur Seine, France
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80
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Miccoli R, Bertolotto A, Navalesi R, Odoguardi L, Boni A, Wessling J, Funke H, Wiebusch H, Eckardstein A, Assmann G. Compound heterozygosity for a structural apolipoprotein A-I variant, apo A-I(L141R)Pisa, and an apolipoprotein A-I null allele in patients with absence of HDL cholesterol, corneal opacifications, and coronary heart disease. Circulation 1996; 94:1622-8. [PMID: 8840853 DOI: 10.1161/01.cir.94.7.1622] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND The concentration of HDL cholesterol is inversely correlated with the risk of coronary heart disease (CHD). Some rare mutations in the apolipoprotein (apo) A-I gene are associated with low levels of HDL cholesterol. Their association with cardiovascular risk is controversial. METHODS AND RESULTS We studied the molecular defects underlying corneal opacities and absence of HDL cholesterol in three brothers and a sister. In a family study, the importance of these defects for lipid metabolism and manifestation of coronary heart disease was investigated. The frequency of these apo A-I defects was assessed by genotype and phenotype analysis of 477 DNA- and plasma samples, respectively, from the population. The four patients were compound heterozygotes for a null allele and a missense mutation in the apo A-I gene that leads to a leucine-->arginine substitution at residue 141 [apo A-I(L141R)Pisa]. Heterozygotes for either the null allele or the structural variant had half-normal concentrations of HDL cholesterol and apo A-I compared with unaffected family members. Apo A-I(L141R)Pisa was detected in one more unrelated subject. Coronary angiography of the four compound heterozygotes revealed the presence of CHD in all male patients, whose ages ranged between 45 and 52 years. They presented with additional risk factors, including elevated LDL cholesterol levels, obesity, and arterial hypertension. Despite complete HDL deficiency and hypercholesterolemia, CHD was absent in the 51-year-old premenopausal sister. CONCLUSIONS Apo A-I deficiency may lead to premature atherosclerosis if present in conjunction with additional cardiovascular risk factors.
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Affiliation(s)
- R Miccoli
- Cattedra di Malattie del Metabolismo, Università degli Studi di Pisa, Italy
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81
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Mowri HO, Patsch JR, Gotto AM, Patsch W. Apolipoprotein A-II influences the substrate properties of human HDL2 and HDL3 for hepatic lipase. Arterioscler Thromb Vasc Biol 1996; 16:755-62. [PMID: 8640403 DOI: 10.1161/01.atv.16.6.755] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hepatic lipase has a demonstrated dual role in plasma lipid transport in that it participates in the removal of remnants of triglyceride-rich lipoproteins from the circulation and in the metabolism of plasma HDL. The study presented here investigated the substrate properties for hepatic lipase of HDL differing in density and apolipoprotein (apo) composition. Rates of fatty acid liberation were twofold higher in HDL2 compared with the respective HDL3 subspecies. Within each density class, enzyme-catalyzed fatty acid release was nearly twofold higher from HDL containing apoA-II compared with HDL devoid of apoA-II. When native HDL3 devoid of apoA-II was reconstituted with dimeric apoA-II in vitro, rates of fatty acid liberation in reconstituted particles were similar to those in native HDL3 containing apoA-II. HDL containing apoA-II competed more effectively with small VLDL for binding of hepatic lipase than HDL devoid of apoA-II. HDL3, particularly apoA-II-containing HDL3, reduced lipolysis of triglyceride and total fatty acid liberation in small VLDL. We conclude that the substrate properties of HDLs for hepatic lipase are influenced by both their size and apoA-II content. Moreover, size as well as apoA-II content may indirectly affect remnant clearance.
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Affiliation(s)
- H O Mowri
- Department of Medicine, Baylor College of Medicine, Houston, Tex, USA
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82
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Brousseau ME, Santamarina-Fojo S, Zech LA, Bérard AM, Vaisman BL, Meyn SM, Powell D, Brewer HB, Hoeg JM. Hyperalphalipoproteinemia in human lecithin cholesterol acyltransferase transgenic rabbits. In vivo apolipoprotein A-I catabolism is delayed in a gene dose-dependent manner. J Clin Invest 1996; 97:1844-51. [PMID: 8621767 PMCID: PMC507252 DOI: 10.1172/jci118614] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Lecithin cholesterol acyltransferase (LCAT) is an enzyme involved in the intravascular metabolism of high density lipoproteins (HDLs). Overexpression of human LCAT (hLCAT) in transgenic rabbits leads to gene dose-dependent increases of total and HDL cholesterol concentrations. To elucidate the mechanisms responsible for this effect, 131I-HDL apoA-I kinetics were assessed in age- and sex-matched groups of rabbits (n=3 each) with high, low, or no hLCAT expression. Mean total and HDL cholesterol concentrations (mg/dl), respectively, were 162+/-18 and 121+/-12 for high expressors (HE), 55+/-6 and 55+/-10 for low expressors (LE), and 29+/-2 and 28+/-4 for controls. Fast protein liquid chromatography analysis of plasma revealed that the HDL of both HE and LE were cholesteryl ester and phospholipid enriched, as compared with controls, with the greatest differences noted between HE and controls. These compositional changes resulted in an incremental shift in apparent HDL particle size which correlated directly with the level of hLCAT expression, such that HE had the largest HDL particles and controls the smallest. In vivo kinetic experiments demonstrated that the fractional catabolic rate(FCR, d(-1)) of apoA-I was slowest in HE (0.328+/-0.03) followed by LE (0.408+/-0.01) and, lastly, by controls (0.528+/-0.04). ApoA-I FCR was inversely associated with HDL cholesterol level (r=-0.851,P<0.01) and hLCAT activity (r=-0.816, P<0.01). These data indicate that fractional catabolic rate is the predominant mechanism by which hLCAT overexpression differentially modulates HDL concentrations in this animal model. We hypothesize that LCAT-induced changes in HDL composition and size ultimately reduce apoA-I catabolism by altering apoA-I conformation and/or HDL particle regeneration.
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Affiliation(s)
- M E Brousseau
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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83
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Abstract
An inverse relationship between the concentration of high density lipoprotein (HDL) cholesterol and the development of coronary heart disease (CHD) is well established. It is unclear from the human studies whether this relationship reflects an ability of HDLs to protect against coronary disease or whether a low HDL in coronary patients is simply an epiphenomenon. Recent studies of transgenic mice, however, indicate that HDLs are directly antiatherogenic. The mechanism of the protection is unknown but may relate both to an involvement of HDLs in plasma cholesterol transport and to a range of non-lipid transport functions of HDLs. It is also unclear from human studies whether specific HDL subpopulations have differing abilities to protect against CHD, although such specificity is suggested from studies of transgenic mice. There is circumstantial evidence that elevating the concentration of HDL cholesterol in human subjects translates into a reduced coronary risk, although it should be stressed that there are still no reports of studies designed specifically to address this issue.
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Affiliation(s)
- P J Barter
- Department of Medicine, Royal Adelaide Hospital, Australia
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84
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Kuivenhoven JA, Stalenhoef AF, Hill JS, Demacker PN, Errami A, Kastelein JJ, Pritchard PH. Two novel molecular defects in the LCAT gene are associated with fish eye disease. Arterioscler Thromb Vasc Biol 1996; 16:294-303. [PMID: 8620346 DOI: 10.1161/01.atv.16.2.294] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A 53-year-old man with a severely reduced HDL cholesterol level, dense corneal opacities, normal renal function, and premature coronary artery disease was investigated together with 16 members of his family. The proband was diagnosed with fish eye disease. As in previously reported patients with fish eye disease, the endogenous plasma cholesterol esterification rate was near normal, yet lecithin:cholesterol acyltransferase (LCAT) activity was almost absent when measured with exogenous HDL analogues used as substrate. Direct sequencing of the LCAT gene revealed two novel missense mutations in exon 1 and exon 4, resulting in the substitution of Pro10 with Gln (P10Q) and Arg135 with Gln (R135Q), respectively. Both missense mutations were located on different alleles. Genetic analysis by polymerase chain reaction revealed 4 carriers of the P10Q and 3 carriers of the R135Q defect. Functional assessment of both missense mutations revealed that when exogenous HDL analogues were used as substrate, the specific activity of rLCAT p10Q was 18% of wild type (WT); however, when LDL was used as substrate, the activity was 146% of WT. By contrast, rLCATR135Q was inactive against both substrates. Thus, we conclude that the LCATR135D mutation is causative for complete LCAT deficiency and that the clinical phenotype of fish eye disease seen in this patient is due to the Pro10 mutation. The presence of premature coronary artery disease in the absence of other risk factors in this new case of fish eye disease raises questions regarding the risk of atherosclerosis, which has previously been reported to be nonexistent.
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Affiliation(s)
- J A Kuivenhoven
- Department of Hemostasis, Thrombosis, Atherosclerosis and Inflammation Research, University of Amsterdam, The Netherlands
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85
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Ikewaki K, Zech LA, Brewer H, Rader DJ. ApoA-II kinetics in humans using endogenous labeling with stable isotopes: slower turnover of apoA-II compared with the exogenous radiotracer method. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37626-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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86
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Kuivenhoven JA, van Voorst tot Voorst EJ, Wiebusch H, Marcovina SM, Funke H, Assmann G, Pritchard PH, Kastelein JJ. A unique genetic and biochemical presentation of fish-eye disease. J Clin Invest 1995; 96:2783-91. [PMID: 8675648 PMCID: PMC185988 DOI: 10.1172/jci118348] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
This paper describes a novel genetic defect which causes fish-eye disease in four homozygous probands and its biochemical presentation in 34 heterozygous siblings. The male index patient presented with premature coronary artery disease, corneal opacification, HDL deficiency, and a near total loss of plasma lecithin:cholesterol acyltransferase (LCAT) activity. Sequencing of the LCAT gene revealed homozygosity for a novel missense mutation resulting in an Asp131 - Asn (N131D) substitution. Heterozygotes showed a highly significant reduction of HDL-cholesterol and apolipoprotein A-I levels as compared with controls which was associated with a specific decrease of LpA-I:A-II particles. Functional assessment of this mutation revealed loss of specific activity of recombinant LCAT(N131D) against proteoliposomes. Unlike other mutations causing fish-eye disease, recombinant LCAT(N131D) also showed a 75% reduction in specific activity against LDL. These unique biochemical characteristics reveal the heterogeneity of phenotypic expression of LCAT gene defects within a range specified by complete loss of LCAT activity and the specific loss of activity against HDL. The impact of this mutation on HDL levels and HDL subclass distribution may be related to the premature coronary artery disease observed in the male probands.
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Affiliation(s)
- J A Kuivenhoven
- Department of Haemostasis, Thrombosis, Atherosclerosis and Inflammation Research, Academic Medical Centre, University of Amsterdam, The Netherlands
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87
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Packard CJ. The role of stable isotopes in the investigation of plasma lipoprotein metabolism. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1995; 9:755-72. [PMID: 8593124 DOI: 10.1016/s0950-351x(95)80129-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The last 5 years have seen promising beginnings of the application of stable-isotope-based methods to the study of lipoprotein metabolism. Many aspects of plasma lipid transport make it an attractive system for investigating by this means. While early efforts borrowed from standard techniques of generating and interpreting kinetic parameters (FSRs), the shortcomings of these procedures as applied to lipoproteins are now appreciated. Lipoprotein heterogeneity requires that multicompartmental analysis and relatively long-term studies be employed if the information obtained is going to be a useful adjunct to that produced by radio-iodinated lipoprotein tracers. Both approaches-stable-isotope-labeled endogenous tracer and ex vivo radio-iodinated lipoprotein experiments--must be considered complementary. The first provides direct information on lipoprotein synthesis pathways while the latter is superior at following interconversions and catabolic events. Excellent agreement has been demonstrated where the methods have been used simultaneously to estimate the same kinetic parameter. Many of the questions that have arisen from decades of radioactive tracer studies relate to the nature and rate of lipoprotein synthesis, e.g. what kinds of particles are produced by the liver when different diets are taken, and how are the synthetic pathways altered in dyslipidaemic states? Endogenous tracers can address these issues, and methods are presently available which provide the means for measuring the production of all apolipoproteins and for estimating cholesterol and fatty acid biosynthesis. When techniques are developed to examine triglyceride, cholesteryl ester and phospholipid production then a much clearer picture of how lipoproteins are assembled in vivo will emerge. This kind of information will be essential to an understanding of regulation of plasma lipid transport and the subtle changes that occur in those at risk for coronary heart disease.
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Affiliation(s)
- C J Packard
- Institute of Biochemistry, Glasgow Royal Infirmary, UK
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88
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Watts GF, Mitropoulos KA, al-Bahrani A, Reeves BE, Owen JS. Lecithin-cholesterol acyltransferase deficiency presenting with acute pancreatitis: effect of infusion of normal plasma on triglyceride-rich lipoproteins. J Intern Med 1995; 238:137-41. [PMID: 7629481 DOI: 10.1111/j.1365-2796.1995.tb00911.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A 38-year-old Asian man presented with acute pancreatitis, marked hypertriglyceridaemia and macroproteinuria, 20 years after the diagnosis of lecithin-cholesterol acyltransferase (LCAT) deficiency. After recovery, he exhibited macroproteinuria and chylomicronaemia despite treatment with a very-low-fat diet. Infusion of normal plasma significantly increased the proportion of cholesterol esters in the patient's plasma and significantly lowered chylomicron-triglyceride levels, but not proteinuria. We conclude that renal dysfunction may be a late manifestation of LCAT deficiency and that it may lead to severe chylomicronaemia and acute pancreatitis. Infusion of normal plasma corrects the dyslipidaemia in LCAT deficiency, but in the short term does not improve renal function.
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Affiliation(s)
- G F Watts
- University Department of Medicine, University of Western Australia, Royal Perth Hospital
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89
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Vaisman BL, Klein HG, Rouis M, Bérard AM, Kindt MR, Talley GD, Meyn SM, Hoyt RF, Marcovina SM, Albers JJ. Overexpression of human lecithin cholesterol acyltransferase leads to hyperalphalipoproteinemia in transgenic mice. J Biol Chem 1995; 270:12269-75. [PMID: 7744879 DOI: 10.1074/jbc.270.20.12269] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Lecithin cholesterol acyltransferase (LCAT) is a key enzyme which catalyzes the esterification of free cholesterol present in plasma lipoproteins. In order to evaluate the role of LCAT in HDL metabolism, a 6.2-kilobase (kb) fragment consisting of 0.851 and 1.134 kb of the 5'- and 3'-flanking regions, as well as the entire human LCAT gene, was utilized to develop transgenic mice. Three different transgenic mouse lines overexpressing human LCAT at plasma levels 11-, 14-, and 109-fold higher than non-transgenic mice were established. Northern blot hybridization analysis demonstrated that the injected 6.2-kb fragment contained the necessary DNA sequences to direct tissue specific expression of the human LCAT gene in mouse liver. Compared to age- and sex-matched controls, total cholesterol and HDL cholesterol levels were increased in all 3 transgenic mice lines by 124-218 and 123-194%, respectively, while plasma triglyceride concentrations remained similar to that of control animals. Fast protein liquid chromatography analysis of transgenic mouse plasma revealed marked increases in high density liposportin (HDL)-cholesteryl ester and phospholipid as well as the formation of larger size HDL. Thus, the majority of the increase in transgenic plasma cholesterol concentrations was due to accumulation of cholesteryl ester in HDL consistent with enhanced esterification of free cholesterol in mouse HDL by human LCAT. Plasma concentrations of apoA-I, apoA-II, and apoE were increased in high expressor homozygote mice who also demonstrated an accumulation of an apoE-rich HDL1. Like the mouse enzyme, human LCAT was found to be primarily associated with mouse HDL. Our studies demonstrate a high correlation between plasma LCAT activity and total as well as HDL cholesterol levels establishing that in mice LCAT modulates plasma HDL concentrations. Overexpression of LCAT in mice leads to HDL elevation as well as increased heterogeneity of the HDL lipoprotein particles, indicating that high levels of plasma LCAT activity may be associated with hyperalphalipoproteinemia and enhanced reverse cholesterol transport.
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Affiliation(s)
- B L Vaisman
- Molecular Disease Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Ikewaki K, Zech LA, Kindt M, Brewer HB, Rader DJ. Apolipoprotein A-II production rate is a major factor regulating the distribution of apolipoprotein A-I among HDL subclasses LpA-I and LpA-I:A-II in normolipidemic humans. Arterioscler Thromb Vasc Biol 1995; 15:306-12. [PMID: 7749839 DOI: 10.1161/01.atv.15.3.306] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
HDLs are heterogeneous in their apolipoprotein composition. Apolipoprotein (apo) A-I and apoA-II are the major proteins found in HDL and form the two major HDL subclasses: those that contain only apoA-I (LpA-I) and those that contain both apoA-I and apoA-II (LpA-I:A-II). Substantial evidence indicates that these two subclasses differ in their in vivo metabolism and effect on atherosclerosis, with LpA-I the more specifically protective subfraction against atherosclerosis. The purpose of this study was to investigate the effect of apoA-I and apoA-II production and catabolism on plasma LpA-I and LpA-I:A-II levels. Fifty normolipidemic subjects (those with HDL cholesterol levels in the top and bottom tenth percentiles were excluded) underwent kinetic studies with radiolabeled apoA-I and apoA-II, and the kinetic parameters of apoA-I and apoA-II were correlated with LpA-I and LpA-I:A-II levels. ApoA-I levels were strongly correlated with apoA-I residence times and less strongly correlated with apoA-I production rates. In contrast, apoA-II levels were correlated only with apoA-II production rates and not with apoA-II residence times. Levels of apoA-I in LpA-I were correlated with apoA-I residence times, whereas levels of apoA-I in LpA-I:A-II were correlated primarily with apoA-II production rates. The fraction of apoA-I in LpA-I was highly inversely correlated with apoA-II production rate (r = -.67, P < .001). In multiple regression analysis, apoA-II production rate was the most significant independent variable determining percent apoA-I in LpA-I among all the kinetic parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K Ikewaki
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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Ikewaki K, Rader DJ, Zech LA, Brewer HB. In vivo metabolism of apolipoproteins A-I and E in patients with abetalipoproteinemia: implications for the roles of apolipoproteins B and E in HDL metabolism. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)39776-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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