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Barbosa-Gouveia S, Fernández-Crespo S, Lazaré-Iglesias H, González-Quintela A, Vázquez-Agra N, Hermida-Ameijeiras Á. Association of a Novel Homozygous Variant in ABCA1 Gene with Tangier Disease. J Clin Med 2023; 12:jcm12072596. [PMID: 37048678 PMCID: PMC10094818 DOI: 10.3390/jcm12072596] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 03/21/2023] [Accepted: 03/28/2023] [Indexed: 03/31/2023] Open
Abstract
Tangier disease (TD) is a rare autosomal recessive disorder caused by a variant in the ABCA1 gene, characterized by significantly reduced levels of plasma high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-1 (ApoA-I). TD typically leads to accumulation of cholesterol in the peripheral tissues and early coronary disease but with highly variable clinical expression. Herein, we describe a case study of a 59-year-old male patient with features typical of TD, in whom a likely pathogenic variant in the ABCA1 gene was identified by whole-exome sequencing (WES), identified for the first time as homozygous (NM_005502.4: c.4799A>G (p. His1600Arg)). In silico analysis including MutationTaster and DANN score were used to predict the pathogenicity of the variant and a protein model generated by SWISS-MODEL was built to determine how the homozygous variant detected in our patient may change the protein structure and impact on its function. This case study describes a homozygous variant of the ABCA1 gene, which is responsible for a severe form of TD and underlines the importance of using bioinformatics and genomics for linking genotype to phenotype and better understanding and accounting for the functional impact of genetic variations.
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2
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Dong W, Wong KHY, Liu Y, Levy-Sakin M, Hung WC, Li M, Li B, Jin SC, Choi J, Lopez-Giraldez F, Vaka D, Poon A, Chu C, Lao R, Balamir M, Movsesyan I, Malloy MJ, Zhao H, Kwok PY, Kane JP, Lifton RP, Pullinger CR. Whole-exome sequencing reveals damaging gene variants associated with hypoalphalipoproteinemia. J Lipid Res 2022; 63:100209. [PMID: 35460704 PMCID: PMC9126845 DOI: 10.1016/j.jlr.2022.100209] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 04/12/2022] [Accepted: 04/13/2022] [Indexed: 12/02/2022] Open
Abstract
Low levels of high density lipoprotein-cholesterol (HDL-C) are associated with an elevated risk of arteriosclerotic coronary heart disease. Heritability of HDL-C levels is high. In this research discovery study, we used whole-exome sequencing to identify damaging gene variants that may play significant roles in determining HDL-C levels. We studied 204 individuals with a mean HDL-C level of 27.8 ± 6.4 mg/dl (range: 4-36 mg/dl). Data were analyzed by statistical gene burden testing and by filtering against candidate gene lists. We found 120 occurrences of probably damaging variants (116 heterozygous; four homozygous) among 45 of 104 recognized HDL candidate genes. Those with the highest prevalence of damaging variants were ABCA1 (n = 20), STAB1 (n = 9), OSBPL1A (n = 8), CPS1 (n = 8), CD36 (n = 7), LRP1 (n = 6), ABCA8 (n = 6), GOT2 (n = 5), AMPD3 (n = 5), WWOX (n = 4), and IRS1 (n = 4). Binomial analysis for damaging missense or loss-of-function variants identified the ABCA1 and LDLR genes at genome-wide significance. In conclusion, whole-exome sequencing of individuals with low HDL-C showed the burden of damaging rare variants in the ABCA1 and LDLR genes is particularly high and revealed numerous occurrences in HDL candidate genes, including many genes identified in genome-wide association study reports. Many of these genes are involved in cancer biology, which accords with epidemiologic findings of the association of HDL deficiency with increased risk of cancer, thus presenting a new area of interest in HDL genomics.
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Affiliation(s)
- Weilai Dong
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Karen H Y Wong
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Youbin Liu
- Department of Cardiology, The Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, China
| | - Michal Levy-Sakin
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Wei-Chien Hung
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Mo Li
- Department of Biostatistics, Yale School of Public Health, New Haven, CT, USA
| | - Boyang Li
- Department of Biostatistics, Yale School of Public Health, New Haven, CT, USA
| | - Sheng Chih Jin
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA; Department of Genetics, Washington University School of Medicine, St. Louis, MO, USA
| | - Jungmin Choi
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA; Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Korea
| | | | - Dedeepya Vaka
- Institute for Human Genetics, University of California, San Francisco, CA, USA
| | - Annie Poon
- Institute for Human Genetics, University of California, San Francisco, CA, USA
| | - Catherine Chu
- Institute for Human Genetics, University of California, San Francisco, CA, USA
| | - Richard Lao
- Institute for Human Genetics, University of California, San Francisco, CA, USA
| | - Melek Balamir
- Department of Internal Medicine, Istanbul University, Istanbul, Turkey
| | - Irina Movsesyan
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Mary J Malloy
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA; Department of Medicine, University of California, San Francisco, CA, USA; Department of Pediatrics, University of California, San Francisco, CA, USA
| | - Hongyu Zhao
- Department of Biostatistics, Yale School of Public Health, New Haven, CT, USA
| | - Pui-Yan Kwok
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA; Department of Medicine, University of California, San Francisco, CA, USA; Department of Dermatology, University of California, San Francisco, CA, USA
| | - John P Kane
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA; Department of Medicine, University of California, San Francisco, CA, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Richard P Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Clive R Pullinger
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA; Physiological Nursing, University of California, San Francisco, CA, USA.
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Jacobo-Albavera L, Domínguez-Pérez M, Medina-Leyte DJ, González-Garrido A, Villarreal-Molina T. The Role of the ATP-Binding Cassette A1 (ABCA1) in Human Disease. Int J Mol Sci 2021; 22:ijms22041593. [PMID: 33562440 PMCID: PMC7915494 DOI: 10.3390/ijms22041593] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 01/25/2021] [Accepted: 01/27/2021] [Indexed: 02/06/2023] Open
Abstract
Cholesterol homeostasis is essential in normal physiology of all cells. One of several proteins involved in cholesterol homeostasis is the ATP-binding cassette transporter A1 (ABCA1), a transmembrane protein widely expressed in many tissues. One of its main functions is the efflux of intracellular free cholesterol and phospholipids across the plasma membrane to combine with apolipoproteins, mainly apolipoprotein A-I (Apo A-I), forming nascent high-density lipoprotein-cholesterol (HDL-C) particles, the first step of reverse cholesterol transport (RCT). In addition, ABCA1 regulates cholesterol and phospholipid content in the plasma membrane affecting lipid rafts, microparticle (MP) formation and cell signaling. Thus, it is not surprising that impaired ABCA1 function and altered cholesterol homeostasis may affect many different organs and is involved in the pathophysiology of a broad array of diseases. This review describes evidence obtained from animal models, human studies and genetic variation explaining how ABCA1 is involved in dyslipidemia, coronary heart disease (CHD), type 2 diabetes (T2D), thrombosis, neurological disorders, age-related macular degeneration (AMD), glaucoma, viral infections and in cancer progression.
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Affiliation(s)
- Leonor Jacobo-Albavera
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Dirección de Investigación, Instituto Nacional de Medicina Genómica (INMEGEN), Mexico City CP14610, Mexico; (L.J.-A.); (M.D.-P.); (D.J.M.-L.); (A.G.-G.)
| | - Mayra Domínguez-Pérez
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Dirección de Investigación, Instituto Nacional de Medicina Genómica (INMEGEN), Mexico City CP14610, Mexico; (L.J.-A.); (M.D.-P.); (D.J.M.-L.); (A.G.-G.)
| | - Diana Jhoseline Medina-Leyte
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Dirección de Investigación, Instituto Nacional de Medicina Genómica (INMEGEN), Mexico City CP14610, Mexico; (L.J.-A.); (M.D.-P.); (D.J.M.-L.); (A.G.-G.)
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México (UNAM), Coyoacán, Mexico City CP04510, Mexico
| | - Antonia González-Garrido
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Dirección de Investigación, Instituto Nacional de Medicina Genómica (INMEGEN), Mexico City CP14610, Mexico; (L.J.-A.); (M.D.-P.); (D.J.M.-L.); (A.G.-G.)
| | - Teresa Villarreal-Molina
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Dirección de Investigación, Instituto Nacional de Medicina Genómica (INMEGEN), Mexico City CP14610, Mexico; (L.J.-A.); (M.D.-P.); (D.J.M.-L.); (A.G.-G.)
- Correspondence:
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4
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Geller AS, Polisecki EY, Diffenderfer MR, Asztalos BF, Karathanasis SK, Hegele RA, Schaefer EJ. Genetic and secondary causes of severe HDL deficiency and cardiovascular disease. J Lipid Res 2018; 59:2421-2435. [PMID: 30333156 DOI: 10.1194/jlr.m088203] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 10/13/2018] [Indexed: 02/07/2023] Open
Abstract
We assessed secondary and genetic causes of severe HDL deficiency in 258,252 subjects, of whom 370 men (0.33%) and 144 women (0.099%) had HDL cholesterol levels <20 mg/dl. We excluded 206 subjects (40.1%) with significant elevations of triglycerides, C-reactive protein, glycosylated hemoglobin, myeloperoxidase, or liver enzymes and men receiving testosterone. We sequenced 23 lipid-related genes in 201 (65.3%) of 308 eligible subjects. Mutations (23 novel) and selected variants were found at the following gene loci: 1) ABCA1 (26.9%): 2 homozygotes, 7 compound or double heterozygotes, 30 heterozygotes, and 2 homozygotes and 13 heterozygotes with variants rs9282541/p.R230C or rs111292742/c.-279C>G; 2) LCAT (12.4%): 1 homozygote, 3 compound heterozygotes, 13 heterozygotes, and 8 heterozygotes with variant rs4986970/p.S232T; 3) APOA1 (5.0%): 1 homozygote and 9 heterozygotes; and 4) LPL (4.5%): 1 heterozygote and 8 heterozygotes with variant rs268/p.N318S. In addition, 4.5% had other mutations, and 46.8% had no mutations. Atherosclerotic cardiovascular disease (ASCVD) prevalence rates in the ABCA1, LCAT, APOA1, LPL, and mutation-negative groups were 37.0%, 4.0%, 40.0%, 11.1%, and 6.4%, respectively. Severe HDL deficiency is uncommon, with 40.1% having secondary causes and 48.8% of the subjects sequenced having ABCA1, LCAT, APOA1, or LPL mutations or variants, with the highest ASCVD prevalence rates being observed in the ABCA1 and APOA1 groups.
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Affiliation(s)
- Andrew S Geller
- Boston Heart Diagnostics, Framingham, MA 01702.,Cardiovascular Nutrition Laboratory, Human Nutrition Research Center on Aging at Tufts University and Tufts University School of Medicine, Boston, MA 02111
| | | | | | - Bela F Asztalos
- Cardiovascular Nutrition Laboratory, Human Nutrition Research Center on Aging at Tufts University and Tufts University School of Medicine, Boston, MA 02111
| | | | - Robert A Hegele
- Cardiovascular Nutrition Laboratory, Human Nutrition Research Center on Aging at Tufts University and Tufts University School of Medicine, Boston, MA 02111
| | - Ernst J Schaefer
- Boston Heart Diagnostics, Framingham, MA 01702 .,Cardiovascular Nutrition Laboratory, Human Nutrition Research Center on Aging at Tufts University and Tufts University School of Medicine, Boston, MA 02111
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Muratsu J, Koseki M, Masuda D, Yasuga Y, Tomoyama S, Ataka K, Yagi Y, Nakagawa A, Hamada H, Fujita S, Hattori H, Ohama T, Nishida M, Hiraoka H, Matsuzawa Y, Yamashita S. Accelerated Atherogenicity in Tangier Disease. J Atheroscler Thromb 2018; 25:1076-1085. [PMID: 29563393 PMCID: PMC6193190 DOI: 10.5551/jat.43257] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We report a case of Tangier disease with Leriche syndrome and bleeding tendency. In this male patient, nasal hemorrhage had been observed frequently throughout childhood. At 46 years old, he experienced effort angina, and coronary angiography demonstrated 75% stenosis in the right coronary artery. Orange-colored tonsils, mild hepatosplenomegaly and very low levels of serum high-density lipoprotein cholesterol (HDL-C) were observed, and the patient was diagnosed with Tangier disease. At 52 years old, effort angina recurred. Coronary angiography revealed 75% stenosis of the left main trunk, left anterior descending, and right coronary arteries. Stenosis of the brachiocephalic and right common iliac arteries was also recorded. Stents were implanted, and coronary artery bypass surgery was performed. At 53 years old, 15 months after surgery, the patient reported intermittent claudication, coldness of feet, and impotence. Aortic angiography showed progression of the stenosis at the bifurcation of the common iliac artery. The patient was diagnosed with Leriche syndrome, and aorta–left external iliac artery graft bypass surgery was performed. After surgery, oozing from subcutaneous tissue and leaking from the anastomotic region were observed. Additional analysis revealed two single-nucleotide polymorphisms (V825I and N935T) in the ATP-binding cassette transporter A1 (ABCA1) gene, and accumulation of small dense low-density lipoprotein together with low levels of HDL-C. In Tangier disease, HDL-C is markedly decreased because of ABCA1 deficiency. However, this is the first reported case to exhibit extensive atherosclerosis and bleeding tendency. This patient had atypical extensive and multiple atherosclerotic lesions, accompanied by Leriche syndrome and uncontrollable bleeding.
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Affiliation(s)
- Jun Muratsu
- Department of Cardiovascular Medicine, Sumitomo Hospital
| | - Masahiro Koseki
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine.,Department of Health Care Center, Osaka University
| | - Daisaku Masuda
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine
| | - Yuji Yasuga
- Department of Cardiovascular Medicine, Sumitomo Hospital
| | | | - Keiji Ataka
- Department of Cardiovascular Surgery, Sumitomo Hospital
| | - Yoshiki Yagi
- Department of Cardiovascular Medicine, Nissay Hospital
| | | | | | | | | | - Tohru Ohama
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine
| | - Makoto Nishida
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine.,Department of Health Care Center, Osaka University
| | | | - Yuji Matsuzawa
- Department of Cardiovascular Medicine, Sumitomo Hospital
| | - Shizuya Yamashita
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine.,Department of Cardiovascular Medicine, Rinku General Medical Center
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Abstract
High-density lipoprotein cholesterol (HDL-C) levels are inversely related to risk of atherosclerotic cardiovascular disease (ASCVD). However, the simplistic assumption that HDL-C levels directly and causally impact atherogenesis has been challenged in recent years. The purpose of this article is to review the current state of knowledge regarding genetically determined HDL-C levels and ASCVD risk and determine what insight these studies provide into the causal relationship between HDL and atherosclerosis.
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Affiliation(s)
- Liam R Brunham
- Department of Medicine, University of British Columbia, Vancouver, Canada. .,Centre for Heart Lung Innovation, Providence Health Care Research Institute, University of British Columbia, St. Paul's Hospital, Room 166-1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada. .,Translational Laboratory in Genetic Medicine (TLGM), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
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7
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Subfraction analysis of circulating lipoproteins in a patient with Tangier disease due to a novel ABCA1 mutation. Clin Chim Acta 2015; 452:167-72. [PMID: 26616730 DOI: 10.1016/j.cca.2015.11.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 11/22/2015] [Indexed: 12/30/2022]
Abstract
Tangier disease, characterized by low or absent high-density lipoprotein (HDL), is a rare hereditary lipid storage disorder associated with frequent, but not obligatory, severe premature atherosclerosis due to disturbed reverse cholesterol transport from tissues. The reasons for the heterogeneity in atherogenicity in certain dyslipidemias have not been fully elucidated. Here, using high-performance liquid chromatography with a gel filtration column (HPLC-GFC), we have studied the lipoprotein profile of a 17-year old male patient with Tangier disease who to date has not developed manifest coronary atherosclerosis. The patient was shown to be homozygous for a novel mutation (Leu1097Pro) in the central cytoplasmic region of ATP-binding cassette transporter A1 (ABCA1). Serum total and HDL-cholesterol levels were 59mg/dl and 2mg/dl, respectively. Lipoprotein electrophoretic analyses on agarose and polyacrylamide gels showed the presence of massively abnormal lipoproteins. Further analysis by HPLC-GFC identified significant amounts of lipoproteins in low-density lipoprotein (LDL) subfractions. The lipoprotein particles found in the peak subfraction were smaller than normal LDL, were rich in triglycerides, but poor in cholesterol and phospholipids. These findings in an adolescent Tangier patient suggest that patients in whom these triglyceride-rich, cholesterol- and phospholipid-poor LDL-type particles accumulate over time, would experience an increased propensity for developing atherosclerosis.
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8
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Bi X, Zhu X, Duong M, Boudyguina EY, Wilson MD, Gebre AK, Parks JS. Liver ABCA1 deletion in LDLrKO mice does not impair macrophage reverse cholesterol transport or exacerbate atherogenesis. Arterioscler Thromb Vasc Biol 2013; 33:2288-96. [PMID: 23814116 DOI: 10.1161/atvbaha.112.301110] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Hepatic ATP binding cassette transporter A1 (ABCA1) expression is critical for maintaining plasma high-density lipoprotein (HDL) concentrations, but its role in macrophage reverse cholesterol transport and atherosclerosis is not fully understood. We investigated atherosclerosis development and reverse cholesterol transport in hepatocyte-specific ABCA1 knockout (HSKO) mice in the low-density lipoprotein (LDL) receptor KO (LDLrKO) C57BL/6 background. APPROACH AND RESULTS Male and female LDLrKO and HSKO/LDLrKO mice were switched from chow at 8 weeks of age to an atherogenic diet (10% palm oil, 0.2% cholesterol) for 16 weeks. Chow-fed HSKO/LDLrKO mice had HDL concentrations 10% to 20% of LDLrKO mice, but similar very low-density lipoprotein and LDL concentrations. Surprisingly, HSKO/LDLrKO mice fed the atherogenic diet had significantly lower (40% to 60%) very low-density lipoprotein, LDL, and HDL concentrations (50%) compared with LDLrKO mice. Aortic surface lesion area and cholesterol content were similar for both genotypes of mice, but aortic root intimal area was significantly lower (20% to 40%) in HSKO/LDLrKO mice. Although macrophage (3)H-cholesterol efflux to apoB lipoprotein-depleted plasma was 24% lower for atherogenic diet-fed HSKO/LDLrKO versus LDLrKO mice, variation in percentage efflux among individual mice was <2-fold compared with a 10-fold variation in plasma HDL concentrations, suggesting that HDL levels, per se, were not the primary determinant of plasma efflux capacity. In vivo reverse cholesterol transport, resident peritoneal macrophage sterol content, biliary lipid composition, and fecal cholesterol mass were similar between both genotypes of mice. CONCLUSIONS The markedly reduced plasma HDL pool in HSKO/LDLrKO mice is sufficient to maintain macrophage reverse cholesterol transport, which, along with reduced plasma very low-density lipoprotein and LDL concentrations, prevented the expected increase in atherosclerosis.
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Affiliation(s)
- Xin Bi
- From the Section on Lipid Sciences, Department of Pathology (X.B., X.Z., M.D., E.Y.B., M.D.W., A.K.G., J.S.P.), and Department of Biochemistry (J.S.P.), Wake Forest School of Medicine, Winston-Salem, NC
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Hypercholesterolemia and reduced HDL-C promote hematopoietic stem cell proliferation and monocytosis: studies in mice and FH children. Atherosclerosis 2013; 229:79-85. [PMID: 23684512 DOI: 10.1016/j.atherosclerosis.2013.03.031] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 03/26/2013] [Accepted: 03/27/2013] [Indexed: 12/20/2022]
Abstract
Previous studies have shown that mice with defects in cellular cholesterol efflux show hematopoietic stem cell (HSPC) and myeloid proliferation, contributing to atherogenesis. We hypothesized that the combination of hypercholesterolemia and defective cholesterol efflux would promote HSPC expansion and leukocytosis more prominently than either alone. We crossed Ldlr(-/-) with Apoa1(-/-) mice and found that compared to Ldlr(-/-) mice, Ldlr(-/-)/Apoa1(+/-) mice, with similar LDL-cholesterol levels but reduced HDL-cholesterol (HDL-C) levels, had expansion of HSPCs, monocytosis and neutrophilia. Ex vivo studies showed that HSPCs expressed high levels of Ldlr, Scarb1 (Srb1), and Lrp1 and were able to take up both native and oxidized LDL. Native LDL directly stimulated HSPC proliferation, while co-incubation with reconstituted HDL attenuated this effect. We also assessed the impact of HDL-C levels on monocytes in children with familial hypercholesterolemia (FH) (n = 49) and found that subjects with the lowest level of HDL-C, had increased monocyte counts compared to the mid and higher HDL-C levels. Overall, HDL-C was inversely correlated with the monocyte count. These data suggest that in mice, a balance of cholesterol uptake and efflux mechanisms may be one factor in driving HSPC proliferation and monocytosis. Higher monocyte counts in children with FH and low HDL-cholesterol suggest a similar pattern in humans.
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Feng W, Sidorov E, Smith K, Selim M. Recurrent Lobar Intracerebral Hemorrhage in Tangier Disease. J Stroke Cerebrovasc Dis 2012; 21:909.e5-6. [DOI: 10.1016/j.jstrokecerebrovasdis.2011.10.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 10/25/2011] [Indexed: 11/29/2022] Open
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A novel mutation in the ABCA1 gene causing an atypical phenotype of Tangier disease. J Clin Lipidol 2012; 7:82-7. [PMID: 23351586 DOI: 10.1016/j.jacl.2012.09.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 09/09/2012] [Accepted: 09/16/2012] [Indexed: 11/23/2022]
Abstract
Tangier disease is a rare autosomal-recessive disorder caused by mutation in the ATP binding cassette transporter 1 (ABCA1) gene. Typically, Tangier disease manifests with symptoms and signs resulting from the deposition of cholesteryl esters in nonadipose tissues; chiefly, in peripheral nerves leading to neuropathy and in reticulo-endothelial organs, such as liver, spleen, lymph nodes, and tonsils, causing their enlargement and discoloration. An association with early cardiovascular disease can be variable. We describe a patient with a unique phenotype of Tangier disease from a novel splice site mutation in the ABCA1 gene that is associated with a central nervous system presentation resembling multiple sclerosis, and the presence of premature atherosclerosis.
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Chan DC, Hoang A, Barrett PHR, Wong ATY, Nestel PJ, Sviridov D, Watts GF. Apolipoprotein B-100 and apoA-II kinetics as determinants of cellular cholesterol efflux. J Clin Endocrinol Metab 2012; 97:E1658-66. [PMID: 22745238 DOI: 10.1210/jc.2012-1522] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Cellular cholesterol efflux is a key step in reverse cholesterol transport and may depend on the metabolism of apolipoprotein (apo) B-100, apoA-I, and apoA-II. OBJECTIVE We examined the associations between cholesterol efflux and plasma concentrations and kinetics of very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL)-apoB-100, high-density lipoprotein (HDL)-apoA-I, and HDL-apoA-II in men. DESIGN, SUBJECTS, AND METHODS: Thirty men were recruited from the community with a wide range of body mass index. The capacity of plasma and HDL to efflux cholesterol was measured ex vivo. Apolipoprotein kinetics were measured using stable isotope techniques and multicompartmental modeling. RESULTS Cholesterol efflux to whole plasma was correlated with plasma levels of cholesterol, triglyceride, apoB-100, insulin, cholesteryl ester transfer protein, and lecithin-cholesterol acyltransferase, body mass index and waist circumference (P < 0.05 in all). Cholesterol efflux was inversely correlated with the fractional catabolic rate (FCR) of VLDL (r = -0.728), IDL (r = -0.662), and LDL-apoB-100 (r = -0.479) but positively correlated with the FCR (r = 0.438) and production rate (r = 0.468) of HDL-apoA-II. In multiple regression analysis, the concentration and FCR of VLDL-apoB-100 (β-coefficient = 0.708 and -0.518, respectively) and IDL-apoB-100 (β-coefficient = 0.354 and -0.447, respectively) were independent predictors of cholesterol efflux. The association of cholesterol efflux with apoB-100 metabolism was diminished after removal of apoB-100-containing lipoproteins from plasma prior to efflux. All associations, except for cholesteryl ester transfer protein, were lost when cholesterol efflux to isolated HDL was tested. CONCLUSIONS The plasma concentration and kinetics of apoB-100-containing lipoproteins are significant predictors of the capacity of whole plasma to effect cellular cholesterol efflux.
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Affiliation(s)
- Dick C Chan
- School of Medicine and Pharmacology, University of Western Australia, Royal Perth Hospital, G.P.O. Box X2213, Perth, Western Australia 6847, Australia
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13
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Liu M, Chung S, Shelness GS, Parks JS. Hepatic ABCA1 and VLDL triglyceride production. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1821:770-7. [PMID: 22001232 PMCID: PMC3272310 DOI: 10.1016/j.bbalip.2011.09.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 09/23/2011] [Accepted: 09/26/2011] [Indexed: 02/04/2023]
Abstract
Elevated plasma triglyceride (TG) and reduced high density lipoprotein (HDL) concentrations are prominent features of metabolic syndrome (MS) and type 2 diabetes (T2D). Individuals with Tangier disease also have elevated plasma TG concentrations and a near absence of HDL, resulting from mutations in ATP binding cassette transporter A1 (ABCA1), which facilitates the efflux of cellular phospholipid and free cholesterol to assemble with apolipoprotein A-I (apoA-I), forming nascent HDL particles. In this review, we summarize studies focused on the regulation of hepatic very low density lipoprotein (VLDL) TG production, with particular attention on recent evidence connecting hepatic ABCA1 expression to VLDL, LDL, and HDL metabolism. Silencing ABCA1 in McArdle rat hepatoma cells results in diminished assembly of large (>10nm) nascent HDL particles, diminished PI3 kinase activation, and increased secretion of large, TG-enriched VLDL1 particles. Hepatocyte-specific ABCA1 knockout (HSKO) mice have a similar plasma lipid phenotype as Tangier disease subjects, with a two-fold elevation of plasma VLDL TG, 50% lower LDL, and 80% reduction in HDL concentrations. This lipid phenotype arises from increased hepatic secretion of VLDL1 particles, increased hepatic uptake of plasma LDL by the LDL receptor, elimination of nascent HDL particle assembly by the liver, and hypercatabolism of apoA-I by the kidney. These studies highlight a novel role for hepatic ABCA1 in the metabolism of all three major classes of plasma lipoproteins and provide a metabolic link between elevated TG and reduced HDL levels that are a common feature of Tangier disease, MS, and T2D. This article is part of a Special Issue entitled: Triglyceride Metabolism and Disease.
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Affiliation(s)
- Mingxia Liu
- Department of Pathology/Section on Lipid Sciences, Wake Forest School of Medicine, Winston-Salem, NC, USA
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14
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Basak JM, Kim J, Pyatkivskyy Y, Wildsmith KR, Jiang H, Parsadanian M, Patterson BW, Bateman RJ, Holtzman DM. Measurement of apolipoprotein E and amyloid β clearance rates in the mouse brain using bolus stable isotope labeling. Mol Neurodegener 2012; 7:14. [PMID: 22512932 PMCID: PMC3405485 DOI: 10.1186/1750-1326-7-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 04/18/2012] [Indexed: 11/13/2022] Open
Abstract
Background Abnormal proteostasis due to alterations in protein turnover has been postulated to play a central role in several neurodegenerative diseases. Therefore, the development of techniques to quantify protein turnover in the brain is critical for understanding the pathogenic mechanisms of these diseases. We have developed a bolus stable isotope-labeling kinetics (SILK) technique coupled with multiple reaction monitoring mass spectrometry to measure the clearance of proteins in the mouse brain. Results Cohorts of mice were pulse labeled with 13 C6-leucine and the brains were isolated after pre-determined time points. The extent of label incorporation was measured over time using mass spectrometry to measure the ratio of labeled to unlabeled apolipoprotein E (apoE) and amyloid β (Aβ). The fractional clearance rate (FCR) was then calculated by analyzing the time course of disappearance for the labeled protein species. To validate the technique, apoE clearance was measured in mice that overexpress the low-density lipoprotein receptor (LDLR). The FCR in these mice was 2.7-fold faster than wild-type mice. To demonstrate the potential of this technique for understanding the pathogenesis of neurodegenerative disease, we applied our SILK technique to determine the effect of ATP binding cassette A1 (ABCA1) on both apoE and Aβ clearance. ABCA1 had previously been shown to regulate both the amount of apoE in the brain, along with the extent of Aβ deposition, and represents a potential molecular target for lowering brain amyloid levels in Alzheimer's disease patients. The FCR of apoE was increased by 1.9- and 1.5-fold in mice that either lacked or overexpressed ABCA1, respectively. However, ABCA1 had no effect on the FCR of Aβ, suggesting that ABCA1 does not regulate Aβ metabolism in the brain. Conclusions Our SILK strategy represents a straightforward, cost-effective, and efficient method to measure the clearance of proteins in the mouse brain. We expect that this technique will be applicable to the study of protein dynamics in the pathogenesis of several neurodegenerative diseases, and could aid in the evaluation of novel therapeutic agents.
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Affiliation(s)
- Jacob M Basak
- Department of Neurology, Saint Louis, Missouri 63110, USA
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15
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16
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Chung S, Timmins JM, Duong M, Degirolamo C, Rong S, Sawyer JK, Singaraja RR, Hayden MR, Maeda N, Rudel LL, Shelness GS, Parks JS. Targeted deletion of hepatocyte ABCA1 leads to very low density lipoprotein triglyceride overproduction and low density lipoprotein hypercatabolism. J Biol Chem 2010; 285:12197-209. [PMID: 20178985 DOI: 10.1074/jbc.m109.096933] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of ABCA1 activity in Tangier disease (TD) is associated with abnormal apoB lipoprotein (Lp) metabolism in addition to the complete absence of high density lipoprotein (HDL). We used hepatocyte-specific ABCA1 knock-out (HSKO) mice to test the hypothesis that hepatic ABCA1 plays dual roles in regulating Lp metabolism and nascent HDL formation. HSKO mice recapitulated the TD lipid phenotype with postprandial hypertriglyceridemia, markedly decreased LDL, and near absence of HDL. Triglyceride (TG) secretion was 2-fold higher in HSKO compared with wild type mice, primarily due to secretion of larger TG-enriched VLDL secondary to reduced hepatic phosphatidylinositol 3-kinase signaling. HSKO mice also displayed delayed clearance of postprandial TG and reduced post-heparin plasma lipolytic activity. In addition, hepatic LDLr expression and plasma LDL catabolism were increased 2-fold in HSKO compared with wild type mice. Last, adenoviral repletion of hepatic ABCA1 in HSKO mice normalized plasma VLDL TG and hepatic phosphatidylinositol 3-kinase signaling, with a partial recovery of HDL cholesterol levels, providing evidence that hepatic ABCA1 is involved in the reciprocal regulation of apoB Lp production and HDL formation. These findings suggest that altered apoB Lp metabolism in TD subjects may result from hepatic VLDL TG overproduction and increased hepatic LDLr expression and highlight hepatic ABCA1 as an important regulatory factor for apoB-containing Lp metabolism.
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Affiliation(s)
- Soonkyu Chung
- Department of Pathology/Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA
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17
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Brunham LR, Kruit JK, Hayden MR, Verchere CB. Cholesterol in beta-cell dysfunction: the emerging connection between HDL cholesterol and type 2 diabetes. Curr Diab Rep 2010; 10:55-60. [PMID: 20425068 DOI: 10.1007/s11892-009-0090-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Beta-cell dysfunction is a critical step in the pathogenesis of type 2 diabetes. The mechanisms responsible for beta-cell death and dysfunction remain incompletely understood, but include glucolipotoxicity, the deleterious metabolic milieu created by high plasma concentrations of glucose and lipid species. Recently, an important role has emerged for cholesterol in this process. In this article, we review recent advances in our understanding of the role of ABCA1 and cholesterol metabolism in beta-cell function, with particular attention to insights gained from human studies.
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Affiliation(s)
- Liam R Brunham
- Child and Family Research Institute, 980 West 28th Avenue, Vancouver, BC, V5Z 4H4, Canada
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18
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Brunham LR, Singaraja RR, Duong M, Timmins JM, Fievet C, Bissada N, Kang MH, Samra A, Fruchart JC, McManus B, Staels B, Parks JS, Hayden MR. Tissue-specific roles of ABCA1 influence susceptibility to atherosclerosis. Arterioscler Thromb Vasc Biol 2009; 29:548-54. [PMID: 19201688 DOI: 10.1161/atvbaha.108.182303] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The ATP-binding cassette transporter, subfamily A, member 1 (ABCA1) plays a key role in HDL cholesterol metabolism. However, the role of ABCA1 in modulating susceptibility to atherosclerosis is controversial. METHODS AND RESULTS We investigated the role of ABCA1 in atherosclerosis using a combination of overexpression and selective deletion models. First, we examined the effect of transgenic overexpression of a full-length human ABCA1-containing bacterial artificial chromosome (BAC) in the presence or absence of the endogenous mouse Abca1 gene. ABCA1 overexpression in the atherosclerosis-susceptible Ldlr(-/-) background significantly reduced the development of atherosclerosis in both the presence and absence of mouse Abca1. Next, we used mice with tissue-specific inactivation of Abca1 to dissect the discrete roles of Abca1 in different tissues on susceptibility to atherosclerosis. On the Apoe(-/-) background, mice lacking hepatic Abca1 had significantly reduced HDL cholesterol and accelerated atherosclerosis, indicating that the liver is an important site at which Abca1 plays an antiatherogenic role. In contrast, mice with macrophage-specific inactivation of Abca1 on the Ldlr(-/-) background displayed no change in atherosclerotic lesion area. CONCLUSIONS These data indicate that physiological expression of Abca1 modulates the susceptibility to atherosclerosis and establish hepatic Abca1 expression as an important site of atheroprotection. In contrast, we show that selective deletion of macrophage Abca1 does not significantly modulate atherogenesis.
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Affiliation(s)
- Liam R Brunham
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada
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19
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Intestinally derived lipids: Metabolic regulation and consequences—An overview. ATHEROSCLEROSIS SUPP 2008; 9:63-8. [DOI: 10.1016/j.atherosclerosissup.2008.05.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 04/03/2008] [Accepted: 05/13/2008] [Indexed: 01/17/2023]
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20
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Santos RD, Asztalos BF, Martinez LRC, Miname MH, Polisecki E, Schaefer EJ. Clinical presentation, laboratory values, and coronary heart disease risk in marked high-density lipoprotein-deficiency states. J Clin Lipidol 2008; 2:237-47. [PMID: 21291740 DOI: 10.1016/j.jacl.2008.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 06/05/2008] [Accepted: 06/08/2008] [Indexed: 11/30/2022]
Abstract
Our purpose is to provide a framework for diagnosing the inherited causes of marked high-density lipoprotein (HDL) deficiency (HDL cholesterol levels <10 mg/dL in the absence of severe hypertriglyceridemia or liver disease) and to provide information about coronary heart disease (CHD) risk for such cases. Published articles in the literature on severe HDL deficiencies were used as sources. If apolipoprotein (Apo) A-I is not present in plasma, then three forms of ApoA-I deficiency, all with premature CHD,and normal low-density lipoprotein (LDL) cholesterol levels have been described: ApoA-I/C-III/A-IV deficiency with fat malabsorption, ApoA-I/C-III deficiency with planar xanthomas, and ApoA-I deficiency with planar and tubero-eruptive xanthomas (pictured in this review for the first time). If ApoA-I is present in plasma at a concentration <10 mg/dL, with LDL cholesterol that is about 50% of normal and mild hypertriglyceridemia, a possible diagnosis is Tangier disease due to mutations at the adenosine triphosphate binding cassette protein A1 (ABCA1) gene locus. These patients may develop premature CHD and peripheral neuropathy, and have evidence of cholesteryl ester-laden macrophages in their liver, spleen, tonsils, and Schwann cells, as well as other tissues. The third form of severe HDL deficiency is characterized by plasma ApoA-I levels <40 mg/dL, moderate hypertriglyceridemia, and decreased LDL cholesterol, and the finding that most of the cholesterol in plasma is in the free rather than the esterified form, due to a deficiency in lecithin:cholesterol acyltransferase activity. These patients have marked corneal opacification and splenomegaly, and are at increased risk of developing renal failure, but have no clear evidence of premature CHD. Marked HDL deficiency has different etiologies and is generally associated with early CHD risk.
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Affiliation(s)
- Raul D Santos
- Lipid Clinic, Heart Institute (InCor) University of Sao Paulo Medical School Hospital, Sao Paulo, Brazil
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21
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Brunham LR, Kruit JK, Verchere CB, Hayden MR. Cholesterol in islet dysfunction and type 2 diabetes. J Clin Invest 2008; 118:403-8. [PMID: 18246189 DOI: 10.1172/jci33296] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Type 2 diabetes (T2D) frequently occurs in the context of abnormalities of plasma lipoproteins. However, a role for elevated levels of plasma cholesterol in the pathogenesis of this disease is not well established. Recent evidence suggests that alterations of plasma and islet cholesterol levels may contribute to islet dysfunction and loss of insulin secretion. A number of genes involved in lipid metabolism have been implicated in T2D. Recently an important role for ABCA1, a cellular cholesterol transporter, has emerged in regulating cholesterol homeostasis and insulin secretion in pancreatic beta cells. Here we review the impact of cholesterol metabolism on islet function and its potential relationship to T2D.
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Affiliation(s)
- Liam R Brunham
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
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22
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Levy E, Spahis S, Sinnett D, Peretti N, Maupas-Schwalm F, Delvin E, Lambert M, Lavoie MA. Intestinal cholesterol transport proteins: an update and beyond. Curr Opin Lipidol 2007; 18:310-8. [PMID: 17495606 DOI: 10.1097/mol.0b013e32813fa2e2] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Various studies have delineated the causal role of dietary cholesterol in atherogenesis. Strategies have thus been developed to minimize cholesterol absorption, and cholesterol transport proteins found at the apical membrane of enterocytes have been extensively investigated. This review focuses on recent progress related to various brush-border proteins that are potentially involved in alimentary cholesterol transport. RECENT FINDINGS Molecular mechanisms responsible for dietary cholesterol and plant sterol uptake have not been completely defined. Growing evidence, however, supports the concept that several proteins are involved in mediating intestinal cholesterol transport, including SR-BI, NPC1L1, CD36, aminopeptidase N, P-glycoprotein, and the caveolin-1/annexin-2 heterocomplex. Other ABC family members (ABCA1 and ABCG5/ABCG8) act as efflux pumps favoring cholesterol export out of absorptive cells into the lumen or basolateral compartment. Several of these cholesterol carriers influence intracellular cholesterol homeostasis and are controlled by transcription factors, including RXR, LXR, SREBP-2 and PPARalpha. The lack of responsiveness of NPC1L1-deficient mice to ezetimibe suggests that NPC1L1 is likely to be the principal target of this cholesterol-lowering drug. SUMMARY The understanding of the role, genetic regulation and coordinated function of proteins mediating intestinal cholesterol transport may lead to novel ways of treating cardiovascular disease.
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Affiliation(s)
- Emile Levy
- Research Centre, CHU-Sainte-Justine, Québec, Canada.
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23
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Paglialunga S, Cianflone K. Regulation of postprandial lipemia: an update on current trends. Appl Physiol Nutr Metab 2007; 32:61-75. [PMID: 17332785 DOI: 10.1139/h06-100] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
People spend a large percentage of their waking hours in the postprandial state. Postprandial lipemia is associated with disruptions in lipoprotein metabolism and inflammatory factors, cardiovascular disease, MetS, and diabetes. Commonly, the dietary sources of fat exceed the actual needs and the tissues are faced with the excess, with accumulation of chylomicrons and remnant particles. This review will summarize recent findings in postprandial lipemia research with a focus on human studies. The effects of dietary factors and other meal components on postprandial lipemia leads to the following question: do we need a standardized oral lipid tolerance test (OLTT)? An overview of recent findings on FABP2, MTP, LPL, apoAV, and ASP and the effects of body habitus (sex influence and body size), as well as exercise and weight loss, on postprandial lipemia will be summarized.
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Affiliation(s)
- Sabina Paglialunga
- McGill University, Department of Biochemistry, Montreal, QC H3G 1Y6, Canada
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24
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Benton JL, Ding J, Tsai MY, Shea S, Rotter JI, Burke GL, Post W. Associations between two common polymorphisms in the ABCA1 gene and subclinical atherosclerosis: Multi-Ethnic Study of Atherosclerosis (MESA). Atherosclerosis 2006; 193:352-60. [PMID: 16879828 DOI: 10.1016/j.atherosclerosis.2006.06.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Revised: 05/09/2006] [Accepted: 06/09/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE ABCA1 controls the first step in reverse cholesterol transport. The potential associations between G1051A (R219K) and -565C/T genetic polymorphisms in the ABCA1 gene, high-density lipoprotein cholesterol (HDL-C) and subclinical cardiovascular disease in the general population remains unclear. We examined these associations in a sample of Multi-Ethnic Study of Atherosclerosis (MESA) participants. METHODS Nine hundred and sixty-nine MESA participants were genotyped and underwent CT examinations for coronary artery calcification (CAC) and carotid ultrasound examinations for intima media thickness. Genetic association analyses were performed. RESULTS The AA genotype was associated with a 2.4mg/dl higher HDL-C, adjusting for age, gender, race/ethnicity and clinic site (p=0.04). There was a 28% lower prevalence of CAC (p=0.002) in those with AA genotype that persisted after further adjustment for HDL-C. There were no significant associations between -565C/T genotype and HDL-C. There were trends towards a higher prevalence of CAC in those with CT (PR=1.13, p=0.08) and TT (PR=1.16, p=0.08) genotypes, compared with CC genotype. Neither G1051A nor -565C/T polymorphisms were associated with carotid intima media thickness. CONCLUSION The AA genotype of the G1051A polymorphism is associated with slightly higher HDL-C and lower prevalence of CAC and thus may protect against subclinical cardiovascular disease. The T allele of -565 C/T polymorphism may increase risk for subclinical cardiovascular disease.
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Affiliation(s)
- Jeana L Benton
- The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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25
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Plösch T, Kosters A, Groen AK, Kuipers F. The ABC of hepatic and intestinal cholesterol transport. Handb Exp Pharmacol 2006:465-82. [PMID: 16596811 DOI: 10.1007/3-540-27661-0_17] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The liver and (small) intestine are key organs in maintenance of cholesterol homeostasis: both organs show active de novo cholesterogenesis and are able to transport impressive amounts of newly synthesized and diet-derived cholesterol via a number of distinct pathways. Cholesterol trafficking involves the concerted action of a number of transporter proteins, some of which have been identified only recently. In particular, several ATP-binding cassette (ABC) transporters fulfil critical roles. For instance, the ABCG5/ABCG8 couple is crucial for hepatobiliary and intestinal cholesterol excretion, while ABCA1 is essential for high-density lipoprotein formation and, hence, for inter-organ trafficking of the highly water-insoluble cholesterol molecules. Very recently, the Niemann-Pick C1-like 1 protein has been identified as a key player in cholesterol absorption by the small intestine and may represent a target of the cholesterol absorption inhibitor ezetimibe. Alterations in hepatic and intestinal cholesterol transport affect circulating levels of atherogenic lipoproteins and thus the risk for cardiovascular disease. This review specifically deals with the processes of hepatobiliary cholesterol excretion and intestinal cholesterol absorption as well as the interactions between these important transport routes. During the last few years, insight into the mechanisms of hepatic and intestinal cholesterol transport has greatly increased not in the least by the identification of involved transporter proteins and the (partial) elucidation of their mode of action. In addition, information has become available on (transcription) factors regulating expression of the encoding genes. This knowledge is of great importance for the development of a tailored design of novel plasma cholesterol-lowering strategies.
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Affiliation(s)
- T Plösch
- Laboratory of Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, The Netherlands
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26
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Brunham LR, Kruit JK, Iqbal J, Fievet C, Timmins JM, Pape TD, Coburn BA, Bissada N, Staels B, Groen AK, Hussain MM, Parks JS, Kuipers F, Hayden MR. Intestinal ABCA1 directly contributes to HDL biogenesis in vivo. J Clin Invest 2006; 116:1052-62. [PMID: 16543947 PMCID: PMC1401485 DOI: 10.1172/jci27352] [Citation(s) in RCA: 379] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Accepted: 01/17/2006] [Indexed: 11/17/2022] Open
Abstract
Plasma HDL cholesterol levels are inversely related to risk for atherosclerosis. The ATP-binding cassette, subfamily A, member 1 (ABCA1) mediates the rate-controlling step in HDL particle formation, the assembly of free cholesterol and phospholipids with apoA-I. ABCA1 is expressed in many tissues; however, the physiological functions of ABCA1 in specific tissues and organs are still elusive. The liver is known to be the major source of plasma HDL, but it is likely that there are other important sites of HDL biogenesis. To assess the contribution of intestinal ABCA1 to plasma HDL levels in vivo, we generated mice that specifically lack ABCA1 in the intestine. Our results indicate that approximately 30% of the steady-state plasma HDL pool is contributed by intestinal ABCA1 in mice. In addition, our data suggest that HDL derived from intestinal ABCA1 is secreted directly into the circulation and that HDL in lymph is predominantly derived from the plasma compartment. These data establish a critical role for intestinal ABCA1 in plasma HDL biogenesis in vivo.
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Affiliation(s)
- Liam R. Brunham
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Janine K. Kruit
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Jahangir Iqbal
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Catherine Fievet
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Jenelle M. Timmins
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Terry D. Pape
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Bryan A. Coburn
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Nagat Bissada
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Bart Staels
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Albert K. Groen
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - M. Mahmood Hussain
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - John S. Parks
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Folkert Kuipers
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
| | - Michael R. Hayden
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.
Center for Liver, Digestive and Metabolic Diseases, Laboratory of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands.
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, New York, New York, USA.
Institut Pasteur de Lille and Faculté de Pharmacie, Université de Lille, Lille, France.
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
Department of Microbiology, University of British Columbia, Vancouver, British Columbia, Canada.
Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
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27
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Temel RE, Lee RG, Kelley KL, Davis MA, Shah R, Sawyer JK, Wilson MD, Rudel LL. Intestinal cholesterol absorption is substantially reduced in mice deficient in both ABCA1 and ACAT2. J Lipid Res 2005; 46:2423-31. [PMID: 16150828 DOI: 10.1194/jlr.m500232-jlr200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The process of cholesterol absorption has yet to be completely defined at the molecular level. Because of its ability to esterify cholesterol for packaging into nascent chylomicrons, ACAT2 plays an important role in cholesterol absorption. However, it has been found that cholesterol absorption is not completely inhibited in ACAT2-deficient (ACAT2 KO) mice. Because ABCA1 mRNA expression was increased 3-fold in the small intestine of ACAT2 KO mice, we hypothesized that ABCA1-dependent cholesterol efflux sustains cholesterol absorption in the absence of ACAT2. To test this hypothesis, cholesterol absorption was measured in mice deficient in both ABCA1 and ACAT2 (DKO). Compared with wild-type, ABCA1 KO, or ACAT2 KO mice, DKO mice displayed the lowest level of cholesterol absorption. The concentrations of hepatic free and esterified cholesterol and gallbladder bile cholesterol were significantly reduced in DKO compared with wild-type and ABCA1 KO mice, although these measures of hepatic cholesterol metabolism were very similar in DKO and ACAT2 KO mice. We conclude that ABCA1, especially in the absence of ACAT2, can have a significant effect on cholesterol absorption, although ACAT2 has a more substantial role in this process than ABCA1.
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Affiliation(s)
- Ryan E Temel
- Department of Pathology, Section on Lipid Sciences, Wake Forest University Health Sciences, Winston-Salem, NC, USA
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Abstract
PURPOSE OF REVIEW High-density lipoprotein cholesterol (HDL-C) has been well established as an inverse predictor of coronary heart disease (CHD), and in recent years, investigations have focused on the genetic regulation of high-density lipoprotein. Although numerous candidate genes contribute to the low HDL-C phenotype, their impact on CHD is heterogeneous, reflecting diverse gene-gene interactions and gene-environmental relationships. This review summarizes recent data involving HDL regulatory genes and their role in atherothrombosis. RECENT FINDINGS The primary genetic determinants associated with relative HDL-C deficiency states are the ATP binding cassette protein, ABCA1; apolipoprotein (APO) A1; and lecithin cholesteryl acyl transferase. Other potentially important candidates invoked in low HDL-C syndromes in humans include APOC3, lipoprotein lipase, sphingomyelin phosphodiesterase 1, and glucocerebrosidase. Molecular variation in ABCAI and APOAI and, in selected cases, lecithin cholesteryl acyl transferase deficiency have been associated with increased CHD, whereas two notable variants, APOAIMilano and APOAIParis, are associated with reduced risk. SUMMARY Low HDL-C syndromes have generally been correlated with an increased risk of CHD. However, single-gene abnormalities responsible for HDL-C deficiency states may have variable effects on atherothrombotic risk.
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Affiliation(s)
- Michael Miller
- Department of Medicine, University of Maryland Hospital and Veterans Affairs Medical Center, Baltimore, Maryland, USA.
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Abstract
Substantial evidence exists suggesting that small, dense LDL particles are associated with an increased risk of coronary heart disease. This disease-related risk factor is recognized to be under both genetic and environmental influences. Several studies have been conducted to elucidate the genetic architecture underlying this trait, and a review of this literature seems timely. The methods and strategies used to determine its genetic component and to identify the genes have greatly changed throughout the years owing to the progress made in genetic epidemiology and the influence of the Human Genome Project. Heritability studies, complex segregation analyses, candidate gene linkage and association studies, genome-wide linkage scans, and animal models are all part of the arsenal to determine the susceptibility genes. The compilation of these studies clearly revealed the complex genetic nature of LDL particles. This work is an attempt to summarize the growing evidence of genetic control on LDL particle heterogeneity with the aim of providing a concise overview in one read.
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Affiliation(s)
- Yohan Bossé
- Lipid Research Center, Laval University Medical Research Center, Laval University, Québec, Canada
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30
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Hong SH, Rhyne J, Miller M. Novel polypyrimidine variation (IVS46: del T -39...-46) in ABCA1 causes exon skipping and contributes to HDL cholesterol deficiency in a family with premature coronary disease. Circ Res 2003; 93:1006-12. [PMID: 14576201 DOI: 10.1161/01.res.0000102957.84247.8f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recent studies have implicated mutations in the ATP-binding cassette transporter A1, ABCA1, as a cause of Tangier disease (TD) and familial hypoalphalipoproteinemia (FHA). We investigated a proband with very low levels of high-density lipoprotein cholesterol (HDL-C, 6 mg/dL) and a history of premature coronary heart disease (CHD). Sequencing of the ABCA1 gene revealed 2 distinct variants. The first mutation was a G5947A substitution (R1851Q). The second mutation was a single-nucleotide deletion of thymidine in a polypyrimidine tract located 33 to 46 bps upstream to the start of exon 47. This mutation does not involve the 3' acceptor splice site and is outside the lariat branchpoint sequence (IVS46: del T -39...-46). Amplification of cDNA obtained in cultured fibroblasts of the proband and affected family member revealed an abnormally spliced cDNA sequence with skipping of exon 47. These variants were not identified in over 400 chromosomes of healthy whites. Compound heterozygotes (n=4) exhibited the lowest HDL-C (11+/-5 mg/dL) and ApoA-I (35+/-15 mg/dL) compared with wild-type (n=25) (HDL-C 51+/-14 mg/dL; ApoA-I 133+/-21 mg/dL) (P<0.0005) or subjects affected with either R1851Q (n=6) (HDL-C 36+/-8; ApoA-I 117+/-19) or IVS46: del T -39...-46 (n=5) (HDL-C 31+9; ApoA-I 115+28 (P<0.01). These data suggest that polypyrimidine tract variation may represent a novel mechanism for altered splicing and exon skipping that is independent of traditional intronic variants as previously identified in acceptor/donor splice regions or the lariat branchpoint domain.
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Affiliation(s)
- Seung Ho Hong
- Department of Medicine, University of Maryland and Veterans Administration Medical Center, Baltimore, Md, USA
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31
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Joyce C, Freeman L, Brewer HB, Santamarina-Fojo S. Study of ABCA1 function in transgenic mice. Arterioscler Thromb Vasc Biol 2003; 23:965-71. [PMID: 12615681 DOI: 10.1161/01.atv.0000055194.85073.ff] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ATP-binding cassette transporter A1 (ABCA1), identified in 1999 as the gene defective in Tangier disease, promotes efflux of cellular cholesterol from macrophages and other peripheral tissues to apolipoprotein acceptors. These ABCA1-mediated processes are anticipated to have antiatherogenic properties, prompting the development of pharmacological agents that increase ABCA1 gene expression as well as the establishment of ABCA1-transgenic mouse lines. Preliminary studies of ABCA1-Tg mice seem to validate the selection of this transporter as a therapeutic target for the treatment of low HDL syndromes and cardiovascular disease but have also raised new questions regarding the function of ABCA1. In particular, the relative contribution of hepatic and peripheral ABCA1 to plasma HDL levels and to reverse cholesterol transport, as well as the potential role of ABCA1 in modulating the plasma concentrations of the apolipoprotein B-containing lipoproteins and protecting against atherosclerosis, seem to be promising areas of investigation. The present review summarizes the most recent studies and discusses insights provided by these transgenic mouse models.
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Affiliation(s)
- Charles Joyce
- Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md 20892, USA.
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32
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Abstract
PURPOSE OF REVIEW A significant advance in our understanding of the reverse cholesterol transport pathway occurred in 1999 with the identification of defects in the ATP-binding cassette transporter A1 gene as the cause of Tangier disease. Since this discovery, an overwhelming number of experiments have been conducted to further define the function of this gene. Among the concepts emerging from such studies is a possible role for the gene in cholesterol absorption. The present review summarizes the most recent of these studies, as well as the only report to describe the effects of fatty acids on ATP-binding cassette transporter A1 gene activity. RECENT FINDINGS From the one study conducted thus far, it appears that unsaturated fatty acids can reduce ATP-binding cassette transporter A1 gene activity by enhancing its degradation. Among the primary modulators of the gene's transcription is the liver X receptor, with liver X receptor-selective agonists significantly increasing expression of the gene. While some studies indicate that upregulation of the gene inhibits cholesterol absorption, the results of other studies suggest that it facilitates cholesterol absorption and the transfer of cholesterol into the bile. Preliminary evidence from studies with transgenic and knockout mice supports the concept that increasing ATP-binding cassette transporter A1 gene expression may be beneficial in the prevention of diet-induced atherosclerosis. SUMMARY Although there is substantial evidence from and studies to suggest that the ATP-binding cassette transporter A1 gene regulates intestinal cholesterol absorption, perhaps by mediating cholesterol efflux from the basolateral surface of enterocytes, it remains unclear whether or not this gene is the primary ATP-binding cassette transporter involved in the process.
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Affiliation(s)
- Margaret E Brousseau
- Tufts University School of Medicine, and Lipid Metabolism Laboratory, Jean Mayer-USDA Human Nutrition Research Center on Aging, Boston, Massachusetts 02111, USA.
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Abstract
PURPOSE OF REVIEW Two hallmarks of cardiovascular disease are the presence of sterol-laden macrophages in the artery wall and reduced plasma HDL levels. A cell membrane protein named ATP-binding cassette transporter A1 (ABCA1) mediates secretion of excess cholesterol from cells into the HDL metabolic pathway. The discovery of ABCA1 in 1999 triggered a deluge of studies conducted to characterize the properties of this important transporter. The present review summarizes the more recent of those studies and evaluates their implications for the role of ABCA1 in cholesterol transport, HDL metabolism, and atherogenesis. RECENT FINDINGS Cell culture experiments have shown that ABCA1 transports cholesterol, phospholipids, and other lipophilic molecules across the plasma membrane, where they are picked up by apolipoproteins containing little or no lipids, but the mechanisms involved are still unclear. It is now apparent that factors in addition to sterols modulate ABCA1 expression by diverse transcriptional and post-transcriptional processes. Studies in humans and mice with ABCA1 mutations revealed that the relative activity of ABCA1 determines plasma HDL levels and influences susceptibility to cardiovascular disease. Mouse models are beginning to provide insights into the function of ABCA1 in vivo but are also raising new questions regarding the contribution of ABCA1 to total cholesterol flux. SUMMARY Recent studies underscore the critical role of ABCA1 in clearing excess cholesterol from macrophages and generating HDL particles, implicating ABCA1 as an attractive new therapeutic target for treating cardiovascular disease.
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Affiliation(s)
- John F Oram
- Department of Medicine, University of Washington, Seattle 98195-6426, USA.
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Burnett JR, Barrett PHR. Apolipoprotein B metabolism: tracer kinetics, models, and metabolic studies. Crit Rev Clin Lab Sci 2002; 39:89-137. [PMID: 12014529 DOI: 10.1080/10408360208951113] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The study of apolipoprotein (apo) B metabolism is central to our understanding of lipoprotein metabolism. However, the assembly and secretion of apoB-containing lipoproteins is a complex process. Specialized techniques, developed and applied to in vitro and in vivo studies of apoB metabolism, have provided insights into the mechanisms involved in the regulation of this process. Moreover, these studies have important implications for understanding both the pathophysiology as well as the therapeutic options for the dyslipidemias. The purpose of this review is to examine the role of apoB in lipoprotein metabolism and to explore the applications of kinetic analysis and multicompartmental modeling to the study of apoB metabolism. New developments and significant advances over the last decade are discussed.
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Affiliation(s)
- John R Burnett
- Department of Core Clinical Pathology and Biochemistry, Royal Perth Hospital, University of Western Australia, Australia.
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