51
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Mezdour H, Larigauderie G, Castro G, Torpier G, Fruchart J, Nowak M, Fruchart JC, Rouis M, Maeda N. Characterization of a new mouse model for human apolipoprotein A-I/C-III/A-IV deficiency. J Lipid Res 2006; 47:912-20. [PMID: 16497661 DOI: 10.1194/jlr.m500414-jlr200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human data raised the possibility that coronary heart disease is associated with mutations in the apolipoprotein gene cluster APOA1/C3/A4 that result in multideficiency of cluster-encoded apolipoproteins and hypoalphalipoproteinemia. To test this hypothesis, we generated a mouse model for human apolipoprotein A-I (apoA-I)/C-III/A-IV deficiency. Homozygous mutants (Apoa1/c3/a4(-/-)) lacking the three cluster-encoded apolipoproteins were viable and fertile. In addition, feeding behavior and growth were apparently normal. Total cholesterol (TC), high density lipoprotein cholesterol (HDLc), and triglyceride levels in the plasma of fasted mutants fed a regular chow were 32% (P < 0.001), 17% (P < 0.001), and 70% (P < 0.01), respectively, those of wild-type mice. When fed a high-fat Western-type (HFW) diet, Apoa1/c3/a4(-/-) mice showed a further decrease in HDLc concentration and a moderate increase in TC, essentially in non-HDL fraction. The capacity of Apoa1/c3/a4(-/-) plasma to promote cholesterol efflux in vitro was decreased to 75% (P < 0.001), and LCAT activity was decreased by 38% (P < 0.01). Despite the very low total plasma cholesterol, the imbalance in lipoprotein distribution caused small but detectable aortic lesions in one-third of Apoa1/c3/a4(-/-) mice fed a HFW diet. In contrast, none of the wild-type mice had lesions. These results demonstrate that Apoa1/c3/a4(-/-) mice display clinical features similar to human apoA-I/C-III/A-IV deficiency (i.e., marked hypoalphalipoproteinemia) and provide further support for the apoa1/c3/a4 gene cluster as a minor susceptibility locus for atherosclerosis in mice.
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Affiliation(s)
- Hafid Mezdour
- Laboratoire de Génétique Expérimentale, Institut Pasteur de Lille, France
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52
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Lee RG, Shah R, Sawyer JK, Hamilton RL, Parks JS, Rudel LL. ACAT2 contributes cholesteryl esters to newly secreted VLDL, whereas LCAT adds cholesteryl ester to LDL in mice. J Lipid Res 2005; 46:1205-12. [PMID: 15805543 DOI: 10.1194/jlr.m500018-jlr200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The relative contributions of ACAT2 and LCAT to the cholesteryl ester (CE) content of VLDL and LDL were measured. ACAT2 deficiency led to a significant decrease in the percentage of CE (37.2 +/- 2.1% vs. 3.9 +/- 0.8%) in plasma VLDL, with a concomitant increase in the percentage of triglyceride (33.0 +/- 3.2% vs. 66.7 +/- 2.5%). Interestingly, the absence of ACAT2 had no apparent effect on the percentage CE in LDL, whereas LCAT deficiency significantly decreased the CE percentage (38.6 +/- 4.0% vs. 54.6 +/- 1.9%) and significantly increased the phospholipid percentage (11.2 +/- 0.9% vs. 19.3 +/- 0.1%) of LDL. When both LCAT and ACAT2 were deficient, VLDL composition was similar to VLDL of the ACAT2-deficient mouse, whereas LDL was depleted in core lipids and enriched in surface lipids, appearing discoidal when observed by electron microscopy. We conclude that ACAT2 is important in the synthesis of VLDL CE, whereas LCAT is important in remodeling VLDL to LDL. Liver perfusions were performed, and perfusate apolipoprotein B accumulation rates in ACAT2-deficient mice were not significantly different from those of controls; perfusate VLDL CE decreased from 8.0 +/- 0.8% in controls to 0 +/- 0.7% in ACAT2-deficient mice. In conclusion, our data establish that ACAT2 provides core CE of newly secreted VLDL, whereas LCAT adds CE during LDL particle formation.
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Affiliation(s)
- Richard G Lee
- Arteriosclerosis Research Program, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
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53
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Timmins JM, Lee JY, Boudyguina E, Kluckman KD, Brunham LR, Mulya A, Gebre AK, Coutinho JM, Colvin PL, Smith TL, Hayden MR, Maeda N, Parks JS. Targeted inactivation of hepatic Abca1 causes profound hypoalphalipoproteinemia and kidney hypercatabolism of apoA-I. J Clin Invest 2005; 115:1333-42. [PMID: 15841208 PMCID: PMC1074680 DOI: 10.1172/jci23915] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Accepted: 02/15/2005] [Indexed: 01/08/2023] Open
Abstract
Patients with Tangier disease exhibit extremely low plasma HDL concentrations resulting from mutations in the ATP-binding cassette, sub-family A, member 1 (ABCA1) protein. ABCA1 controls the rate-limiting step in HDL particle assembly by mediating efflux of cholesterol and phospholipid from cells to lipid-free apoA-I, which forms nascent HDL particles. ABCA1 is widely expressed; however, the specific tissues involved in HDL biogenesis are unknown. To determine the role of the liver in HDL biogenesis, we generated mice with targeted deletion of the second nucleotide-binding domain of Abca1 in liver only (Abca1(-L/-L)). Abca1(-L/-L) mice had total plasma and HDL cholesterol concentrations that were 19% and 17% those of wild-type littermates, respectively. In vivo catabolism of HDL apoA-I from wild-type mice or human lipid-free apoA-I was 2-fold higher in Abca1(-L/-L) mice compared with controls due to a 2-fold increase in the catabolism of apoA-I by the kidney, with no change in liver catabolism. We conclude that in chow-fed mice, the liver is the single most important source of plasma HDL. Furthermore, hepatic, but not extrahepatic, Abca1 is critical in maintaining the circulation of mature HDL particles by direct lipidation of hepatic lipid-poor apoA-I, slowing its catabolism by the kidney and prolonging its plasma residence time.
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Affiliation(s)
- Jenelle M Timmins
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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54
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Timmins JM, Lee JY, Boudyguina E, Kluckman KD, Brunham LR, Mulya A, Gebre AK, Coutinho JM, Colvin PL, Smith TL, Hayden MR, Maeda N, Parks JS. Targeted inactivation of hepatic Abca1 causes profound hypoalphalipoproteinemia and kidney hypercatabolism of apoA-I. J Clin Invest 2005. [DOI: 10.1172/jci200523915] [Citation(s) in RCA: 378] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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55
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Stein O, Stein Y. Lipid transfer proteins (LTP) and atherosclerosis. Atherosclerosis 2005; 178:217-30. [PMID: 15694928 DOI: 10.1016/j.atherosclerosis.2004.10.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Revised: 09/07/2004] [Accepted: 10/05/2004] [Indexed: 10/26/2022]
Abstract
This review deals with four lipid transfer proteins (LTP): three are involved in cholesteryl ester (CE) synthesis or transport, the fourth deals with plasma phospholipid (PL) transfer. Experimental models of atherosclerosis, clinical and epidemiological studies provided information as to the relationship of these LTP(s) to atherosclerosis, which is the main focus of this review. Thus, inhibition of acyl-CoA:cholesterol acyltransferase (ACAT) 1 and 2 decreases cholesterol absorption, plasma cholesterol and aortic cholesterol esterification in the aorta. The discovery that tamoxifen is a potent ACAT inhibitor explained the plasma cholesterol lowering of the drug. The use of ACAT inhibition in humans is under current investigation. As low cholesteryl ester transfer protein (CETP) activity is connected with high HDL-C, several CETP inhibitors were tried in rabbits, with variable results. A new CETP inhibitor, Torcetrapib, was tested in humans and there was a 50-100% increase in HDL-C. Lecithin cholesterol acyl-transferase (LCAT) influences oxidative stress, which can be lowered by transient LCAT gene transfer in LCAT-/- mice. Phospholipid transfer protein (PLTP) deficiency reduced apo B production in apo E-/- mice, as well as oxidative stress in four models of mouse atherosclerosis. In conclusion, the ability to increase HDL-C so markedly by inhibitors of CETP introduces us into a new era in prevention and treatment of coronary heart disease (CHD).
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Affiliation(s)
- O Stein
- Department of Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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56
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Lee RG, Kelley KL, Sawyer JK, Farese RV, Parks JS, Rudel LL. Plasma cholesteryl esters provided by lecithin:cholesterol acyltransferase and acyl-coenzyme a:cholesterol acyltransferase 2 have opposite atherosclerotic potential. Circ Res 2004; 95:998-1004. [PMID: 15486318 DOI: 10.1161/01.res.0000147558.15554.67] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Evidence suggests that ACAT2 is a proatherogenic enzyme that contributes cholesteryl esters (CEs) to apoB-containing lipoproteins, whereas LCAT is an antiatherogenic enzyme that facilitates reverse cholesterol transport by esterifying free cholesterol on HDL particles. We hypothesized that deletion of LCAT and ACAT2 would lead to absence of plasma CEs and reduced atherosclerosis. To test this hypothesis, ACAT2-/- LCAT-/- LDLr-/-, ACAT2-/- LDLr-/-, and LCAT-/- LDLr-/- mice were fed a 0.15% cholesterol diet for 20 weeks. In comparison to LDLr-/- mice, the total plasma cholesterol (TPC) of ACAT2-/- LCAT-/- LDLr-/- mice was 67% lower because of the complete absence of plasma CEs, leading to 94% less CE accumulation in the aorta. In the LCAT-/- LDLr-/- mice, TPC and atherosclerosis were significantly higher because of increased accumulations of ACAT2-derived CE. In ACAT2-/- LDLr-/- mice, again compared with LDLr-/- mice, TPC was 19% lower, whereas atherosclerosis was 88% lower. Therefore, the absence of ACAT2 led to a significant reduction in TPC although benefits in reduction of atherosclerosis were much more pronounced. Overall, the data suggest that ACAT2-derived CE is the predominant atherogenic lipid in blood, and that an important goal for prevention of atherosclerosis is to limit ACAT2-derived CE accumulation in lipoproteins.
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MESH Headings
- Animals
- Aorta/metabolism
- Aorta/pathology
- Aortic Diseases/blood
- Aortic Diseases/enzymology
- Aortic Diseases/etiology
- Aortic Diseases/genetics
- Aortic Diseases/pathology
- Apolipoproteins B/blood
- Arteriosclerosis/blood
- Arteriosclerosis/enzymology
- Arteriosclerosis/etiology
- Arteriosclerosis/genetics
- Arteriosclerosis/pathology
- Cholesterol/blood
- Cholesterol Esters/analysis
- Cholesterol Esters/blood
- Cholesterol, Dietary/pharmacokinetics
- Cholesterol, Dietary/toxicity
- Cholesterol, HDL/blood
- Cholesterol, LDL/blood
- Cholesterol, VLDL/blood
- Diet, Atherogenic
- Fatty Acids, Unsaturated/blood
- Intestinal Absorption
- Lecithin Cholesterol Acyltransferase Deficiency/blood
- Lecithin Cholesterol Acyltransferase Deficiency/genetics
- Liver/chemistry
- Liver/enzymology
- Male
- Mice
- Mice, Knockout
- Particle Size
- Phosphatidylcholine-Sterol O-Acyltransferase/genetics
- Phosphatidylcholine-Sterol O-Acyltransferase/physiology
- Receptors, LDL/deficiency
- Receptors, LDL/genetics
- Sterol O-Acyltransferase/deficiency
- Sterol O-Acyltransferase/genetics
- Sterol O-Acyltransferase/physiology
- Trans Fatty Acids/toxicity
- Triglycerides/analysis
- Sterol O-Acyltransferase 2
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Affiliation(s)
- Richard G Lee
- Arteriosclerosis Research Program, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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57
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Zhang AH, Gao S, Fan JL, Huang W, Zhao TQ, Liu G. Increased plasma HDL cholesterol levels and biliary cholesterol excretion in hamster by LCAT overexpression. FEBS Lett 2004; 570:25-9. [PMID: 15251433 DOI: 10.1016/j.febslet.2004.06.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2004] [Revised: 05/21/2004] [Accepted: 06/02/2004] [Indexed: 11/30/2022]
Abstract
Lecithin cholesterol acyltransferase (LCAT) is a key enzyme in the metabolism of high density lipoprotein (HDL), which has been found inversely correlated with atherosclerosis. Adenovirus mediated overexpression of human LCAT (hLCAT) in hamsters resulted in increased levels of plasma total cholesterol, HDL cholesterol, phospholipids and enlarged particle size of HDL. It also increased cholesterol and total bile acid concentrations in bile. Hepatic mRNA level of cholesterol 7alpha-hydroxylase increased 2.7-fold in hamsters. However, such effects were not observed in mice in a parallel experiment. This study suggests that overexpression of hLCAT in hamsters facilitated reverse cholesterol transport. Similar metabolic changes in humans might modify atherogenic risk.
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Affiliation(s)
- Ai-Hong Zhang
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiology, Ministry of Education, Peking University, 38 Xue Yuan Road, Beijing 100083, PR China
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58
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Ng DS. Treating low HDL—From bench to bedside. Clin Biochem 2004; 37:649-59. [PMID: 15302606 DOI: 10.1016/j.clinbiochem.2004.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 04/05/2004] [Accepted: 04/05/2004] [Indexed: 01/21/2023]
Abstract
The inverse relationship between the plasma high-density lipoprotein cholesterol (HDL-C) and the risk of coronary heart disease (CHD) is well recognized in the general population. However, the development of effective therapeutics targeting HDL continues to be challenging, which is due in part to the heterogeneity of its structure and composition and the complexity of its metabolism. In this paper, we review a number of recent advances in our understanding of HDL metabolism and its role in atherogenesis. We discuss the HDL-C raising effect of a selected number of currently available lipid-modifying drugs and on a selected number of novel HDL-targeted therapeutic strategies under development.
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Affiliation(s)
- Dominic S Ng
- Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada.
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59
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Siahanidou T, Mandyla H, Papassotiriou I, Anagnostakis D. Serum lipids in preterm infants fed a formula supplemented with nucleotides. J Pediatr Gastroenterol Nutr 2004; 38:56-60. [PMID: 14676595 DOI: 10.1097/00005176-200401000-00013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND The effect of dietary nucleotides on lipid metabolism has been the subject of clinical studies with conflicting results. We measured serum triglycerides, total cholesterol (total-C), and lipoprotein cholesterol levels (HDL-C, LDL-C, and VLDL-C) in preterm neonates fed formula with and without nucleotide supplements. METHODS This prospective, randomized, controlled study included 150 healthy preterm neonates (gestational age, 33.0 +/- 1.9 weeks) matched for gestational age, birth weight, and gender. Subjects were assigned at birth to receive either a standard milk formula supplemented with nucleotides (group F-NT) or the same formula without nucleotides (group F). Serum was obtained before discharge (29.1 +/- 10.0 days of life) and triglycerides, total-C, and HDL-C were determined enzymatically. LDL-C and VLDL-C were estimated by the Friedewald formula. For statistical analysis t test, Mann Whitney-U test, two-way ANOVA, and chi2 test were used, as appropriate. The influence of several factors on serum lipid levels was evaluated by linear regression analysis. RESULTS Serum triglycerides, total-C, and VLDL-C levels did not differ between groups. HDL-C levels (median; 25th-75th percentiles) were significantly higher (P < 0.001) in group F-NT (48.0 mg/dL; 40.5-57.0 mg/dL) than in group F (34.5 mg/dL; 27.2-44.0 mg/dL). On the contrary, LDL-C levels (median; 25th-75th percentiles) were significantly lower (P < 0.001) in group F-NT (39.0 mg/dL; 26.0-54.0 mg/dL) than in group F (65.0 mg/dL; 41.0-73.0 mg/dL). In the multiple regression analysis, nucleotide supplementation was identified as one of the controlled independent factors influencing serum HDL-C and LDL-C levels. CONCLUSIONS Preterm neonates fed from birth with formula supplemented with nucleotides have significantly higher HDL-C and lower LDL-C serum levels than do neonates fed unsupplemented formula. The clinical relevance of these results remains to be elucidated.
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Affiliation(s)
- Tania Siahanidou
- Neonatal Unit, A' Department of Pediatrics, Athens University, Greece.
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60
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Zabalawi M, Bhat S, Loughlin T, Thomas MJ, Alexander E, Cline M, Bullock B, Willingham M, Sorci-Thomas MG. Induction of fatal inflammation in LDL receptor and ApoA-I double-knockout mice fed dietary fat and cholesterol. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:1201-13. [PMID: 12937162 PMCID: PMC1868257 DOI: 10.1016/s0002-9440(10)63480-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Atherogenic response to dietary fat and cholesterol challenge was evaluated in mice lacking both the LDL receptor (LDLr(-/-)) and apoA-I (apoA-I(-/-)) gene, LDLr(-/-)/apoA-I(-/-) or double-knockout mice. Gender- and age-matched LDLr(-/-)/apoA-I(-/-) mice were fed a diet consisting of 0.1% cholesterol and 10% palm oil for 16 weeks and compared to LDLr(-/-) mice or single-knockout mice. The LDLr(-/-) mice showed a 6- to 7-fold increase in total plasma cholesterol (TPC) compared to their chow-fed mice counterparts, while LDLr(-/-)/apoA-I(-/-) mice showed only a 2- to 3-fold increase in TPC compared to their chow-fed controls. This differential response to the atherogenic diet was unanticipated, since chow-fed LDLr(-/-) and LDLr(-/-)/apoA-I(-/-) mice began the study with similar LDL levels and differed primarily in their HDL concentration. The 6-fold diet-induced increase in TPC observed in the LDLr(-/-) mice occurred mainly in VLDL/LDL and not in HDL. Mid-study plasma samples taken after 8 weeks of diet feeding showed that LDLr(-/-) mice had TPC concentrations approximately 60% of their 16-week level, while the LDLr(-/-)/apoA-I(-/-) mice had reached 100% of their 16-week TPC concentration after only 8 weeks of diet. Male LDLr(-/-) mice showed similar aortic cholesterol levels to male LDLr(-/-)/apoA-I(-/-) mice despite a 4-fold higher VLDL/LDL concentration in the LDLr(-/-) mice. A direct comparison of the severity of aortic atherosclerosis between female LDLr(-/-) and LDLr(-/-)/apoA-I(-/-) mice was compromised due to the loss of female LDLr(-/-)/apoA-I(-/-) mice between 10 and 14 weeks into the study. Diet-fed female and, with time, male LDLr(-/-)/apoA-I(-/-) mice suffered from severe ulcerated cutaneous xanthomatosis. This condition, combined with a complete depletion of adrenal cholesterol, manifested in fatal wasting of the affected mice. In conclusion, LDLr(-/-) and LDLr(-/-)/apoA-I(-/-) mice showed dramatic TPC differences in response to dietary fat and cholesterol challenge, while despite these differences both genotypes accumulated similar levels of aortic cholesterol.
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Affiliation(s)
- Manal Zabalawi
- Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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61
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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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62
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Goto A, Sasai K, Suzuki S, Fukutomi T, Ito S, Matsushita T, Okamoto M, Suzuki T, Itoh M, Okumura-Noji K, Yokoyama S. Plasma concentrations of LPL and LCAT are in putative association with females and alcohol use which are independent negative risk factors for coronary atherosclerosis among Japanese. Clin Chim Acta 2003; 329:69-76. [PMID: 12589967 DOI: 10.1016/s0009-8981(03)00021-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Coronary heart disease (CHD) prevalence appears low among Japanese. Analysis of their negative risk factors is therefore important for public health strategy. METHODS We analyzed the impact on coronary atherosclerosis of sex, alcohol intake, plasma lipoproteins and enzymes to regulate cholesterol transport, lipoprotein lipase (LPL) and lecithin:cholesterol acyltransferase (LCAT) for the 110 patients who underwent coronary angiography, consecutively enrolled by excluding those >70 years or under hypolipidemic-drug treatment. Subgroup combinations compared were males vs. females in non-drinkers, and drinkers vs. non-drinkers in males. RESULTS Coronary stenosis was less in females and in drinkers, accompanied by high-density lipoprotein (HDL) in the respective comparison. LPL associated with sex (females>males) and LCAT with alcohol intake (drinkers>non-drinkers) although neither enzyme demonstrated direct correlation with coronary stenosis. LPL positively associated only with HDL in most of subgroups and LCAT correlated with low-density lipoprotein (LDL) in all subgroups but with HDL only in males. CONCLUSIONS Among non-drinkers, females are at lower risk for coronary atherosclerosis than males mainly due to higher HDL in potential association with high LPL, and that drinkers are protected among males also by high HDL that is in apparent association with LCAT.
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Affiliation(s)
- Akitomo Goto
- Internal Medicine and Bioregulation, Nagoya City University Graduate School of Medical Sciences, Aichi, Japan
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63
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Hoang A, Huang W, Sasaki J, Sviridov D. Natural mutations of apolipoprotein A-I impairing activation of lecithin:cholesterol acyltransferase. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1631:72-6. [PMID: 12573451 DOI: 10.1016/s1388-1981(02)00357-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Five natural mutations of apolipoprotein A-I (apoA-I), apoA-I(A95D), apoA-I(Y100H), apoA-I(E110K), apoA-I(V156E) and apoA-I(H162Q), were studied for their ability to activate lecithin:cholesterol acyltransferase (LCAT). Mutants apoA-I(E110K), apoA-I(V156E) and apoA-I(H162Q) had an impaired ability to activate LCAT. Combined with data on other apoA-I mutants this finding is consistent with the idea that the central region between amino acids 110 and 160 is likely to be the "active site" of apoA-I involved in the interaction with LCAT and that a specific sequence of apoA-I is required for activation of the enzyme.
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Affiliation(s)
- Anh Hoang
- Wynn Domain, Baker Medical Research Institute, PO Box 6492 St Kilda Rd Central, Melbourne Vic 8008, Australia
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64
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Abstract
High-density lipoproteins (HDLs) are strongly related to risk of atherosclerotic cardiovascular disease. Low levels of HDL cholesterol are a major cardiovascular risk factor, and overexpression of the major HDL protein, apolipoprotein (apo) A-I, markedly inhibits progression and even induces regression of atherosclerosis in animal models. Clinical data regarding the effect of increasing HDL cholesterol on vascular events are limited. HDL remains an important potential target for therapeutic intervention. A variety of gene products are involved in the regulation of HDL metabolism. Yet, the mechanisms by which HDL inhibits atherosclerosis are not yet fully understood. There remains much to be learned about HDL metabolism and its relation to atherosclerosis and other cardiovascular risk factors.
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Affiliation(s)
- Daniel J Rader
- University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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65
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Rudel LL, Davis M, Sawyer J, Shah R, Wallace J. Primates highly responsive to dietary cholesterol up-regulate hepatic ACAT2, and less responsive primates do not. J Biol Chem 2002; 277:31401-6. [PMID: 12080065 DOI: 10.1074/jbc.m204106200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of liver acyl-CoA:cholesterol acyltransferase 2 (ACAT2), earlier shown to be the principal ACAT enzyme within primate hepatocytes, as a regulator of the hypercholesterolemia induced by dietary cholesterol was studied. At the end of low and high cholesterol diet periods, liver biopsies were taken from cynomolgus monkeys, a species highly responsive to dietary cholesterol, and less responsive African green monkeys. Liver cholesterol and cholesteryl ester concentrations were highest in cynomolgus monkeys fed cholesterol, despite the fact that in order to induce equivalent hypercholesterolemia, dietary cholesterol levels were 50% lower than was fed to green monkeys. Hepatic cholesteryl oleate secretion rate, measured during liver perfusion as an indicator of ACAT activity, was significantly higher in cynomolgus monkeys. Liver microsomal ACAT activity was 2-3-fold higher in cynomolgus monkeys than in green monkeys. The responses of ACAT2 were compared with those of ACAT1 that is found primarily in Kupffer cells. ACAT2 protein mass was significantly correlated to microsomal total ACAT activity in both species; ACAT1 mass was less well correlated. Dietary cholesterol induced a significant 3-fold increase of ACAT2 protein mass in cynomolgus monkeys, a much greater increase than was found for mRNA abundance; neither ACAT2 mRNA nor protein was diet-responsive in green monkeys. In cynomolgus monkeys but not in green monkeys, liver free cholesterol concentrations were elevated when cholesterol was fed and were correlated with ACAT2 protein levels. The data suggest a mechanism whereby the elevation of hepatic free cholesterol concentrations by dietary cholesterol, seen only in cynomolgus monkeys, resulted in higher ACAT2 protein levels in hepatocytes, either through increased production or stabilization of the protein. Regulation of ACAT2 gene transcription was not a factor.
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Affiliation(s)
- Lawrence L Rudel
- Arteriosclerosis Research Program, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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66
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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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