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Giammanco A, Spina R, Fayer F, Barbagallo CM, Noto D, Cefalù AB, Averna MR. Lack of phenotypic additive effect of familial defective apolipoprotein B3531 in familial hypercholesterolaemia. Intern Med J 2021; 51:585-590. [PMID: 33890362 DOI: 10.1111/imj.15275] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/19/2020] [Accepted: 12/09/2020] [Indexed: 11/27/2022]
Abstract
Familial defective apolipoprotein (apo) B (FDB) and familial hypercholesterolaemia (FH) are the two common genetic conditions that cause hypercholesterolaemia. R3531C mutation of the APOB gene is a rare cause of FDB. Individuals with both FDB and FH are rare. A 51-year-old man with hypercholesterolaemia (11.4 mmol/L) and his family were studied. Low-density lipoprotein (LDL) receptor (LDLR) and APOB genes were analysed by direct sequencing. LDL of four subjects were studied in a fibroblast LDL receptor-binding displacement assay. We found a mutation of the LDLR gene (p.Y398X) in the proband and in four other family members: the p.R3531C APOB gene mutation was also found in the proband, his father and his children. The proband and his son were thus compound heterozygotes for both FH and FDB. Double heterozygotes did not show higher cholesterol levels compared to carriers of LDLR gene mutation alone. LDL from one of the carriers of the p.R3531C alone exhibited a binding ability, which was similar to a normal subject. This is the first report in Italy of the p.R3531C mutation, and our results show that this mutation has no effect in LDLR p.Y398X/APOB p.R3531C double heterozygotes.
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Affiliation(s)
- Antonina Giammanco
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Rossella Spina
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Francesca Fayer
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Carlo M Barbagallo
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Davide Noto
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Angelo B Cefalù
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
| | - Maurizio R Averna
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialities (ProMISE), University of Palermo, Palermo, Italy
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Calandra S, Tarugi P, Bertolini S. Impact of rare variants in autosomal dominant hypercholesterolemia causing genes. Curr Opin Lipidol 2017; 28:267-272. [PMID: 28323660 DOI: 10.1097/mol.0000000000000414] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE OF REVIEW The systematic analysis of the major candidate genes in autosomal dominant hypercholesterolemia (ADH) and the use of next-generation sequencing (NGS) technology have made possible the discovery of several rare gene variants whose pathogenic effect in most cases remains poorly defined. RECENT FINDINGS One major advance in the field has been the adoption of a set of international guidelines for the assignment of pathogenicity to low-density lipoprotein receptor (LDLR) gene variants based on the use of softwares, complemented with data available from literature and public databases. The clinical impact of several novel rare variants in LDLR, APOB, PCSK9, APOE genes have been reported in large studies describing patients with ADH found to be homozygotes/compound heterozygotes, double heterozygotes, or simple heterozygotes. In-vitro functional studies have been conducted to clarify the effect of some rare ApoB variants on LDL binding to LDLR and the impact of a rare ApoE variant on the uptake of VLDL and LDL by hepatocytes. SUMMARY The update of the ADH gene variants database and the classification of variants in categories of pathogenicity is a major advance in the understanding the pathophysiology of ADH and in the management of this disorder. The studies of molecularly characterized patients with ADH have emphasized the impact of a specific variant and the variable clinical expression of different genotypes. The functional studies of some variants have increased our understanding of the molecular bases of some forms of ADH.
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Affiliation(s)
- Sebastiano Calandra
- aDepartment of Biomedical, Metabolic and Neural Sciences bDepartment of Life Sciences, University of Modena and Reggio Emilia, Modena cDepartment of Internal Medicine, University of Genova, Genova, Italy
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Wintjens R, Bozon D, Belabbas K, MBou F, Girardet JP, Tounian P, Jolly M, Boccara F, Cohen A, Karsenty A, Dubern B, Carel JC, Azar-Kolakez A, Feillet F, Labarthe F, Gorsky AMC, Horovitz A, Tamarindi C, Kieffer P, Lienhardt A, Lascols O, Di Filippo M, Dufernez F. Global molecular analysis and APOE mutations in a cohort of autosomal dominant hypercholesterolemia patients in France. J Lipid Res 2016; 57:482-91. [PMID: 26802169 DOI: 10.1194/jlr.p055699] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Indexed: 11/20/2022] Open
Abstract
Autosomal dominant hypercholesterolemia (ADH) is a human disorder characterized phenotypically by isolated high-cholesterol levels. Mutations in the low density lipoprotein receptor (LDLR), APOB, and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes are well known to be associated with the disease. To characterize the genetic background associated with ADH in France, the three ADH-associated genes were sequenced in a cohort of 120 children and 109 adult patients. Fifty-one percent of the cohort had a possible deleterious variant in LDLR, 3.1% in APOB, and 1.7% in PCSK9. We identified 18 new variants in LDLR and 2 in PCSK9. Three LDLR variants, including two newly identified, were studied by minigene reporter assay confirming the predicted effects on splicing. Additionally, as recently an in-frame deletion in the APOE gene was found to be linked to ADH, the sequencing of this latter gene was performed in patients without a deleterious variant in the three former genes. An APOE variant was identified in three patients with isolated severe hypercholesterolemia giving a frequency of 1.3% in the cohort. Therefore, even though LDLR mutations are the major cause of ADH with a large mutation spectrum, APOE variants were found to be significantly associated with the disease. Furthermore, using structural analysis and modeling, the identified APOE sequence changes were predicted to impact protein function.
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Affiliation(s)
- René Wintjens
- Faculty of Pharmacy (CP206/04), Université Libre de Bruxelles, B-1050 Brussels, Belgium
| | | | - Khaldia Belabbas
- Laboratoire Commun de Biologie et Génétiques Moléculaires (LCBGM), AP-HP (Assistance Publique-Hopitaux de Paris), Hôpital Saint-Antoine, F-75012, Paris, France
| | - Félicien MBou
- Service d'Endocrinologie, CHU du Lamentin, F-97232 Le Lamentin, Martinique, France
| | - Jean-Philippe Girardet
- Service de Gastroentérologie et Nutrition Pédiatrique, AP-HP, Hôpital Trousseau, F-75012, Paris, France
| | - Patrick Tounian
- Service de Gastroentérologie et Nutrition Pédiatrique, AP-HP, Hôpital Trousseau, F-75012, Paris, France
| | - Mathilde Jolly
- Service d'Endocrinologie, Diabétologie et Nutrition, CH Angers, F-49933, Angers, France
| | - Franck Boccara
- Service d'Endocrinologie, Diabétologie et Nutrition, CH Angers, F-49933, Angers, France
| | - Ariel Cohen
- Service d'Endocrinologie, Diabétologie et Nutrition, CH Angers, F-49933, Angers, France
| | - Alexandra Karsenty
- Service de Gastroentérologie et Nutrition Pédiatrique, AP-HP, Hôpital Trousseau, F-75012, Paris, France
| | - Béatrice Dubern
- Service de Gastroentérologie et Nutrition Pédiatrique, AP-HP, Hôpital Trousseau, F-75012, Paris, France
| | - Jean-Claude Carel
- Université Paris Diderot, Sorbonne Paris Cité, F-75019, Paris, France Service d'Endocrinologie Diabétologie Pédiatrique et Centre de Référence des Maladies Endocriniennes Rares de la Croissance, AP-HP, Hôpital Robert Debré, F-75019, Paris, France
| | - Ahlam Azar-Kolakez
- Université Paris Diderot, Sorbonne Paris Cité, F-75019, Paris, France Service d'Endocrinologie Diabétologie Pédiatrique et Centre de Référence des Maladies Endocriniennes Rares de la Croissance, AP-HP, Hôpital Robert Debré, F-75019, Paris, France
| | - François Feillet
- Service de Médecine Infantile et de génétique clinique, CHU Nancy-Brabois, F-54511 Vandoeuvre les Nancy, France INSERM NGERE UMR 954, F-54500, Vandoeuvre les Nancy, France
| | - François Labarthe
- Service de médecine pédiatrique, Hopital Clocheville, CHU Tours, F-37044, Tours, France
| | | | - Alice Horovitz
- Service de Cardiologie, CHU Bordeaux-Haut Lévêque, F-33604, Pessac, France
| | | | - Pierre Kieffer
- Service de Médecine Interne, CH Mulhouse, Hôpital E. Muller, F-68070 Mulhouse, France
| | - Anne Lienhardt
- Service de Pédiatrie Médicale, CH Limoges, Hôpital mère/enfants, F-87042 Limoges, France
| | - Olivier Lascols
- Laboratoire Commun de Biologie et Génétiques Moléculaires (LCBGM), AP-HP (Assistance Publique-Hopitaux de Paris), Hôpital Saint-Antoine, F-75012, Paris, France
| | - Mathilde Di Filippo
- Centre de Biologie et de Pathologie Est, CHU Lyon, France Service de Pédiatrie Médicale, CH Limoges, Hôpital mère/enfants, F-87042 Limoges, France
| | - Fabienne Dufernez
- Laboratoire Commun de Biologie et Génétiques Moléculaires (LCBGM), AP-HP (Assistance Publique-Hopitaux de Paris), Hôpital Saint-Antoine, F-75012, Paris, France
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Structural analysis of APOB variants, p.(Arg3527Gln), p.(Arg1164Thr) and p.(Gln4494del), causing Familial Hypercholesterolaemia provides novel insights into variant pathogenicity. Sci Rep 2015; 5:18184. [PMID: 26643808 PMCID: PMC4672294 DOI: 10.1038/srep18184] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 11/13/2015] [Indexed: 12/27/2022] Open
Abstract
Familial hypercholesterolaemia (FH) is an inherited autosomal dominant disorder resulting from defects in the low-density lipoprotein receptor (LDLR), in the apolipoprotein B (APOB) or in the proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. In the majority of the cases FH is caused by mutations occurring within LDLR, while only few mutations in APOB and PCSK9 have been proved to cause disease. p.(Arg3527Gln) was the first mutation in APOB being identified and characterized. Recently two novel pathogenic APOB variants have been described: p.(Arg1164Thr) and p.(Gln4494del) showing impaired LDLR binding capacity, and diminished LDL uptake. The objective of this work was to analyse the structure of p.(Arg1164Thr) and p.(Gln4494del) variants to gain insight into their pathogenicity. Secondary structure of the human ApoB100 has been investigated by infrared spectroscopy (IR) and LDL particle size both by dynamic light scattering (DLS) and electron microscopy. The results show differences in secondary structure and/or in particle size of p.(Arg1164Thr) and p.(Gln4494del) variants compared with wild type. We conclude that these changes underlie the defective binding and uptake of p.(Arg1164Thr) and p.(Gln4494del) variants. Our study reveals that structural studies on pathogenic variants of APOB may provide very useful information to understand their role in FH disease.
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Alves AC, Etxebarria A, Soutar AK, Martin C, Bourbon M. Novel functional APOB mutations outside LDL-binding region causing familial hypercholesterolaemia. Hum Mol Genet 2013; 23:1817-28. [DOI: 10.1093/hmg/ddt573] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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Calandra S, Tarugi P, Speedy HE, Dean AF, Bertolini S, Shoulders CC. Mechanisms and genetic determinants regulating sterol absorption, circulating LDL levels, and sterol elimination: implications for classification and disease risk. J Lipid Res 2011; 52:1885-926. [PMID: 21862702 DOI: 10.1194/jlr.r017855] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This review integrates historical biochemical and modern genetic findings that underpin our understanding of the low-density lipoprotein (LDL) dyslipidemias that bear on human disease. These range from life-threatening conditions of infancy through severe coronary heart disease of young adulthood, to indolent disorders of middle- and old-age. We particularly focus on the biological aspects of those gene mutations and variants that impact on sterol absorption and hepatobiliary excretion via specific membrane transporter systems (NPC1L1, ABCG5/8); the incorporation of dietary sterols (MTP) and of de novo synthesized lipids (HMGCR, TRIB1) into apoB-containing lipoproteins (APOB) and their release into the circulation (ANGPTL3, SARA2, SORT1); and receptor-mediated uptake of LDL and of intestinal and hepatic-derived lipoprotein remnants (LDLR, APOB, APOE, LDLRAP1, PCSK9, IDOL). The insights gained from integrating the wealth of genetic data with biological processes have important implications for the classification of clinical and presymptomatic diagnoses of traditional LDL dyslipidemias, sitosterolemia, and newly emerging phenotypes, as well as their management through both nutritional and pharmaceutical means.
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Affiliation(s)
- Sebastiano Calandra
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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Benn M. Apolipoprotein B levels, APOB alleles, and risk of ischemic cardiovascular disease in the general population, a review. Atherosclerosis 2009; 206:17-30. [PMID: 19200547 DOI: 10.1016/j.atherosclerosis.2009.01.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 01/05/2009] [Accepted: 01/05/2009] [Indexed: 11/25/2022]
Abstract
Apolipoprotein B is a key component in lipid metabolism. Subendothelial retention of apolipoprotein B containing lipoproteins is a necessary initiating event in atherogenesis, and high plasma levels of apolipoprotein B is a risk factor for atherosclerosis, whereas low levels may provide protection. The present review examines, with focus on general population studies, apolipoprotein B levels as a predictor of ischemic cardiovascular disease, as well as the association of mutations and polymorphisms in APOB with plasma apolipoprotein B levels, and risk of ischemic cardiovascular disease. The studies can be summarized as follows: (1) apolipoprotein B predicts ischemic cardiovascular events in both genders, and is better than LDL cholesterol in this respect; (2) linkage disequilibrium structure in APOB is more complex than expected from HapMap data, because a minimal set of tag single nucleotide polymorphisms capturing the entire variation in APOB cannot be identified, and thus most polymorphisms must be evaluated separately in association studies; (3) APOB mutations and polymorphisms are associated with a range of apolipoprotein B and LDL cholesterol levels, although the magnitude of effect sizes of common polymorphisms are modest; (4) both mutations and polymorphisms are associated with LDL metabolism in vivo; (5) association of APOB mutations and polymorphisms with lipid and disease phenotype cannot be predicted in silico using evolutionary conservation or existing prediction programs; and finally, (6) except for the E4154K polymorphism that possibly predicts a reduction in risk of ischemic cerebrovascular disease and ischemic stroke, common APOB polymorphisms with modest effect sizes on lipid levels do not predict risk of ischemic heart disease, myocardial infarction, ischemic cerebrovascular disease, or ischemic stroke in the general population.
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Affiliation(s)
- Marianne Benn
- Department of Clinical Biochemistry KB3011, Section for Molecular Genetics, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, Copenhagen Ø, Denmark.
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Abstract
AbstractBackground: Plasma lipoproteins are important determinants of atherosclerosis. Apolipoprotein (apo) B is a large, amphipathic glycoprotein that plays a central role in human lipoprotein metabolism. Two forms of apoB are produced from the APOB gene by a unique posttranscriptional editing process: apoB-48, which is required for chylomicron production in the small intestine, and apoB-100, required for VLDL production in the liver. In addition to being the essential structural component of VLDL, apoB-100 is the ligand for LDL-receptor-mediated endocytosis of LDL particles.Content: The study of monogenic dyslipidemias has revealed important aspects of metabolic pathways. In this review, we discuss the regulation of apoB metabolism and examine how APOB gene defects can lead to both hypo- and hypercholesterolemia. The key clinical, metabolic, and genetic features of familial hypobetalipoproteinemia and familial ligand-defective apoB-100 are described.Summary: Missense mutations in the LDL-receptor-binding domain of apoB cause familial ligand-defective apoB-100, characterized by hypercholesterolemia and premature coronary artery disease. Other mutations in APOB can cause familial hypobetalipoproteinemia, characterized by hypocholesterolemia and resistance to atherosclerosis. These naturally occurring mutations reveal key domains in apoB and demonstrate how monogenic dyslipidemias can provide insight into biologically important mechanisms.
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Affiliation(s)
- Amanda J Whitfield
- School of Surgery and Pathology, University of Western Australia, Crawley
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Pullinger CR, Kane JP, Malloy MJ. Primary hypercholesterolemia: genetic causes and treatment of five monogenic disorders. Expert Rev Cardiovasc Ther 2004; 1:107-19. [PMID: 15030301 DOI: 10.1586/14779072.1.1.107] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Coronary heart disease is a major cause of death in Europe and the USA. Insudation of atherogenic lipoproteins, including low-density lipoprotein (LDL), into the artery wall is integral to atherosclerosis. It is clear that numerous genetic loci contribute to increased plasma levels of LDL. However, five specific monogenic disorders, three of which have been reported recently, are known to increase LDL. These are familial hypercholesterolemia (LDL receptor gene: LDLR); familial ligand-defective apoB- 100 (apoB gene: APOB); autosomal recessive hypercholesterolemia (ARH gene); sitosterolemia (ABCG5 or ABCG8 genes) and cholesterol 7alpha-hydroxylase deficiency (CYP7A1 gene). This review relates the mechanisms underlying these five disorders with specific therapeutic interventions.
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Affiliation(s)
- Clive R Pullinger
- Cardiovascular Research Institute, University of California, San Francisco, USA.
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Soufi M, Sattler AM, Maerz W, Starke A, Herzum M, Maisch B, Schaefer JR. A new but frequent mutation of apoB-100—apoB His3543Tyr. Atherosclerosis 2004; 174:11-6. [PMID: 15135245 DOI: 10.1016/j.atherosclerosis.2003.12.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Accepted: 12/19/2003] [Indexed: 11/21/2022]
Abstract
ApolipoproteinB 100 (apoB-100) is an important component of atherogenic lipoproteins such as LDL and serves as a ligand for the LDL-receptor. Familial defective apolipoproteinB 100 (FDB) is caused by a R3500Q mutation of the apoB gene and results in decreased binding of LDL to the LDL-receptor. So far FDB is the most frequent and best studied alteration of apoB-100. Apart from this, three other apoB mutations, R3500W, R3531C and R3480W, affecting binding to the LDL-receptor are known to date. We screened the apoB gene segment of codons 3448-3561 by denaturing gradient gel electrophoresis (DGGE) analysis in a total of 853 consecutively sampled German patients undergoing diagnostic coronary angiography for suspected CAD. By this, a new single base mutation was detected and confirmed by DNA sequencing. The mutation, CAC(3543)TAC results in a His3543Tyr substitution in apoB-100 (H3543Y). The prevalence of heterozygotes for H3543Y in the study population was 0.47% compared to 0.12% for the known Arg 3500 Gln (R3500Q) mutation. In conclusion, the new mutation is four times more frequent than "classical" FDB and thus appears to be the most common apoB mutation in Germany.
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Affiliation(s)
- Muhidien Soufi
- Department of Internal Medicine-Cardiology, Philipps-University, Marburg, Germany
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Robles-Osorio L, Ordoñez ML, Aguilar-Salinas CA, Aurón-Gómez M, Tusié-Luna MT, Gómez-Pérez FJ, Rull-Rodrigo JA. Familial hypercholesterolemia due to ligand-defective apolipoprotein B100: first case report in a Mexican family. Arch Med Res 2003; 34:70-5. [PMID: 12604379 DOI: 10.1016/s0188-4409(02)00452-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Familial defective apolipoprotein B100 (FDB) is one of the known causes of familial hypercholesterolemia (FH). Its frequency among subjects with FH varies among ethnic groups; information on FH is insufficient for populations from Latin America. We proposed to describe prevalence of FDB in a cohort of Mexican FH probands (n = 30). METHODS We searched for the known FDB mutations using polymerase chain reaction assays. In this set of patients, mean lipid values were representative of FH (cholesterol 351 mg/dL, LDL cholesterol 274 mg/dL, HDL cholesterol 51 mg/dL, and triglycerides 132 mg/dL). RESULTS One subject with Arg3500Gln mutation was found: a 44-year-old male with a history of coronary heart disease (CHD) among paternal relatives. His lipid profile was cholesterol 370 mg/dL, LDL-cholesterol 300 mg/dL, HDL-cholesterol 32 mg/dL, and triglycerides 189 mg/dL. Tendinous xanthomata were detected. Three of four siblings, one of three sons, and one of nine nieces and nephews carried the mutation. The mutation was confirmed by automated sequencing. Tendinous xanthomata were absent in affected subjects younger than age 20 years; additionally, the subjects had borderline cholesterol levels. CONCLUSIONS Our data suggest that FDB explains the small number of FH cases in Mexico. Inclusion of molecular biology assays to the clinical laboratory makes it possible to diagnose affected individuals with borderline cholesterol levels or without tendinous xanthomata.
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Affiliation(s)
- Ludivina Robles-Osorio
- Departamento de Endocrinologi;a y Metabolismo, Instituto Nacional de Ciencias Médicas y de Nutrición Salvador Zubirán, Mexico City, Mexico
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Pullinger CR, Eng C, Salen G, Shefer S, Batta AK, Erickson SK, Verhagen A, Rivera CR, Mulvihill SJ, Malloy MJ, Kane JP. Human cholesterol 7alpha-hydroxylase (CYP7A1) deficiency has a hypercholesterolemic phenotype. J Clin Invest 2002. [PMID: 12093894 DOI: 10.1172/jci0215387] [Citation(s) in RCA: 346] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Bile acid synthesis plays a critical role in the maintenance of mammalian cholesterol homeostasis. The CYP7A1 gene encodes the enzyme cholesterol 7alpha-hydroxylase, which catalyzes the initial step in cholesterol catabolism and bile acid synthesis. We report here a new metabolic disorder presenting with hyperlipidemia caused by a homozygous deletion mutation in CYP7A1. The mutation leads to a frameshift (L413fsX414) that results in loss of the active site and enzyme function. High levels of LDL cholesterol were seen in three homozygous subjects. Analysis of a liver biopsy and stool from one of these subjects revealed double the normal hepatic cholesterol content, a markedly deficient rate of bile acid excretion, and evidence for upregulation of the alternative bile acid pathway. Two male subjects studied had hypertriglyceridemia and premature gallstone disease, and their LDL cholesterol levels were noticeably resistant to 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors. One subject also had premature coronary and peripheral vascular disease. Study of the kindred, which is of English and Celtic background, revealed that individuals heterozygous for the mutation are also hyperlipidemic, indicating that this is a codominant disorder.
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Affiliation(s)
- Clive R Pullinger
- Cardiovascular Research Institute, University of California-San Francisco, San Francisco, CA 94143-0130, USA.
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Gaffney D, Pullinger CR, O'Reilly DSJ, Hoffs MS, Cameron I, Vass JK, Kulkarni MV, Kane JP, Schumaker VN, Watts GF, Packard CJ. Influence of an asparagine to lysine mutation at amino acid 3516 of apolipoprotein B on low-density lipoprotein receptor binding. Clin Chim Acta 2002; 321:113-21. [PMID: 12031600 DOI: 10.1016/s0009-8981(02)00106-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Three mutations in the apolipoprotein B (apoB) gene have previously been established as important causes of impaired receptor binding of LDL and, hence, Familial Defective Apolipoprotein B 100 (FDB). Previously, undescribed mutations were sought. METHODS Using denaturing gradient gel electrophoresis for mutation detection, DNA from 1852 new patients was examined. RESULTS A previously undiscovered mutation was found in codon 3516, located between known FDB mutations at codons 3500 and 3531. The new mutation introduces a positively charged amino acid-lysine-while other FDB mutations remove a positively charged residue, arginine. The phenotype was intriguing, LDL derived from N3516K heterozygotes allowed only poor growth of an LDL cholesterol-dependent cell line. ApoB-100-specific antibody MB47 bound to LDL from N3516K heterozygotes with increased affinity indicating a probable conformational change caused by the substitution. In contrast to these results, a competitive displacement assay in fibroblasts showed normal (or better) binding affinity to LDL receptors and using dynamic laser scattering no preferential accumulation of 3516K LDL particles in plasma was found. CONCLUSION Discovery of the mutation and characterisation of N3516K LDL reveals another naturally occurring apoB mutation that influences conformation of LDL apoB and its interaction with the LDL receptor.
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Affiliation(s)
- Dairena Gaffney
- Department of Pathological Biochemistry, Glasgow Royal Infirmary, North Glasgow Hospital University NHS Trust, Fourth floor, Queen Elizabeth Building, Alexandra Parade, Glasgow G31 2ER, Scotland, UK.
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14
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Gaffney D, Forster L, Caslake MJ, Bedford D, Stewart JP, Stewart G, Wieringa G, Dominiczak M, Miller JP, Packard CJ. Comparison of apolipoprotein B metabolism in familial defective apolipoprotein B and heterogeneous familial hypercholesterolemia. Atherosclerosis 2002; 162:33-43. [PMID: 11947895 DOI: 10.1016/s0021-9150(01)00679-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Both defective LDL receptors (familial hypercholesterolaemia, FH) and mutations in apolipoprotein B (apoB) on LDL (familial defective apoB, FDB) give rise to a phenotype of elevated LDL cholesterol. We sought to compare the metabolic basis of the two conditions by examining apoB turnover in FDB and FH subjects. A group comprising three heterozygous and one homozygous FDB subjects were compared with five FH heterozygotes and 17 control subjects using a deuterated leucine tracer. Kinetic parameters were derived by multicompartmental modelling. FH heterozygotes had a reduced delipidation rate for VLDL, which led to a moderate increase in plasma triglyceride. Compared with controls and FH, the FDB subjects converted 44% less IDL to LDL. The LDL FCR was reduced to a similar extent in FDB and FH. In all subjects LDL plasma levels appeared to be regulated by the LDL FCR and the rate of production of small VLDL. We conclude that disturbances in IDL metabolism provide the basis for understanding why FDB is less severe than FH. Our findings suggest that an apoB-LDL receptor interaction is important in the IDL to LDL conversion.
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Affiliation(s)
- Dairena Gaffney
- Department of Pathological Biochemistry, Glasgow Royal Infirmary, North Glasgow Hospitals University NHS trust, 4th floor, Queen Elizabeth Building, Alexandra Parade, Glasgow G31 2ER, Scotland, UK.
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15
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A synthetic low density lipoprotein particle capable of supporting U937 proliferation in vitro. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)30188-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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16
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Viola S, Benlian P, Morali A, Dobbelaere D, Lacaille F, Rieu D, Ginies JL, Maurage C, Meyer M, Lachaux A, Larchet M, Lenearts C, Goulet O, Sarles J, Mouterde O, Girardet JP. Apolipoprotein B Arg3500Gln mutation prevalence in children with hypercholesterolemia: a French multicenter study. J Pediatr Gastroenterol Nutr 2001; 33:122-6. [PMID: 11568510 DOI: 10.1097/00005176-200108000-00005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND Familial defective apolipoprotein B-100, a dominantly inherited form of hypercholesterolemia caused by a single Arg3500Gln mutation, is silent in childhood but may confer a high risk of cardiovascular disease in adulthood. The objective was to determine the prevalence of familial defective apolipoprotein B-100 in hypercholesterolemic French children and to provide a basis for targeting screening efforts in this population. METHODS One hundred ninety children attending 13 pediatric clinics distributed throughout France were included based on the presence of type IIa hypercholesterolemia with a plasma low-density lipoprotein-cholesterol level of more than 130 mg/dL. The Arg3500Gln mutation was detected in dried blood spots using a polymerase chain reaction assay combined with enzymatic restriction. RESULTS Three hyperlipidemia phenotypes were found: monogenic dominant pure hypercholesterolemia (n = 117), polygenic hypercholesterolemia (n = 43), and combined hyperlipidemia (n = 11). Three unrelated children were heterozygous for the Arg3500Gln mutation; all three had monogenic dominant pure hypercholesterolemia (3/94 families; 3.2%), yielding a prevalence of 1.83% (3/164) in hypercholesterolemic children, which is similar to prevalences reported in European adults. CONCLUSIONS The familial defective apolipoprotein B-100 mutation was common (1/31) in children with a phenotype of familial hypercholesterolemia, supporting screening in this population with the goal of preventing premature cardiovascular events.
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Affiliation(s)
- S Viola
- Department of Pediatric Gastroenterology and Nutrition, Armand-Trousseau Children's Teaching Hospital, Paris, France
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Rabès JP, Varret M, Devillers M, Aegerter P, Villéger L, Krempf M, Junien C, Boileau C. R3531C mutation in the apolipoprotein B gene is not sufficient to cause hypercholesterolemia. Arterioscler Thromb Vasc Biol 2000; 20:E76-82. [PMID: 11031227 DOI: 10.1161/01.atv.20.10.e76] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Familial hypercholesterolemia and familial ligand-defective apolipoprotein B-100 (FDB) are dominantly inherited disorders leading to impaired low-density lipoprotein receptor (LDLR) and apolipoprotein B-100 (APOB) interaction, plasma LDL elevation, and hypercholesterolemia. We previously identified the first French FDB-R3531C proband, a woman with very high total cholesterol, in a group of type IIa hypercholesterolemic families. We report here the investigation of her family at large that revealed the total absence of cosegregation with hypercholesterolemia. Six of the 10 subjects heterozygous for the R3531C mutation had plasma cholesterol lower than the 97.5th percentile for their age and gender, and mean cholesterol levels were not significantly different between affected and unaffected persons. Furthermore, 2 family members with similar high LDL-cholesterol levels were not carriers of the R3531C substitution, suggesting the implication of another mutation. Segregation analysis of the LDLR gene revealed statistically significant genetic linkage with hypercholesterolemia, and analysis of the proband LDLR gene led to the identification of the 664 proline to leucine defective mutation and its detection in all 6 hypercholesterolemic-related members of this family. Therefore, our results show that the family presents with familial hypercholesterolemia and give evidence that the R3531C substitution in the APOB gene is not an allelic variant leading to FDB. Furthermore, thorough analysis of our data suggests that the APOB-R3531C mutation enhances the hypercholesterolemic effect of the LDLR-P664L defect, suggesting that it is a susceptibility mutation.
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Affiliation(s)
- J P Rabès
- INSERM U383, the Hôpital Necker-Enfants Malades, Paris, France
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18
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Raungaard B, Heath F, Hansen PS, Brorholt-Petersen JU, Jensen HK, Færgeman O. Flow Cytometric Assessment of LDL Ligand Function for Detection of Heterozygous Familial Defective Apolipoprotein B-100. Clin Chem 2000. [DOI: 10.1093/clinchem/46.2.224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AbstractBackground: Familial defective apolipoprotein (apo) B-100 (FDB) is caused by a mutation in the apoB gene and characterized by decreased binding of LDL to LDL receptors because of reduced function of the apoB-100 ligand. FDB may be associated with severe hypercholesterolemia and cannot always be distinguished from familial hypercholesterolemia phenotypically.Methods: We used a fluorescence flow cytometry assay with Epstein-Barr virus-transformed lymphocytes to detect reduced LDL ligand function by competitive binding with fluorescently conjugated LDL (DiI-LDL). The assay was tested and validated using LDL from patients heterozygous for the Arg3500-Gln mutation and their first-degree relatives. Knowing the actual apoB genotype of patients and relatives allowed us to assess the ability of the assay to predict the results of DNA analysis. The results were compared to measurements of LDL ligand function in unrelated healthy control subjects to characterize functionally the Arg3500-Gln mutation.Results: Fluorescence was significantly increased in cells incubated with DiI-LDL in competition with unlabeled LDL from FDBR3500Q heterozygotes compared with cells incubated with DiI-LDL in competition with unlabeled LDL from relatives or unrelated healthy control subjects. Thus, patients heterozygous for the Arg3500-Gln mutation had significantly reduced LDL ligand function. The binding affinity of LDL from FDBR3500Q heterozygotes was 32% of that in non-FDB relatives and healthy controls. The assay had a diagnostic sensitivity of 0.95 and diagnostic specificity of 0.89.Conclusions: The diagnostic accuracy of the assay was too low to allow reliable diagnosis of individual cases of heterozygous FDBR3500Q. However, fluorescence flow cytometry may supplement genetic identification of FDB and functionally characterize gene mutations associated with major reductions in LDL ligand function.
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Affiliation(s)
- Bent Raungaard
- Department of Internal Medicine and Cardiology, Aarhus Amtssygehus University Hospital, Tage Hansens Gade 2, DK-8000 Aarhus C, Denmark
| | - Finn Heath
- Department of Cardiology, Skejby Sygehus University Hospital, DK-8200 Aarhus N, Denmark
| | - Peter Steen Hansen
- Department of Cardiology, Skejby Sygehus University Hospital, DK-8200 Aarhus N, Denmark
| | - Jens Uffe Brorholt-Petersen
- Department of Internal Medicine and Cardiology, Aarhus Amtssygehus University Hospital, Tage Hansens Gade 2, DK-8000 Aarhus C, Denmark
| | - Henrik Kjærulf Jensen
- Department of Cardiology, Skejby Sygehus University Hospital, DK-8200 Aarhus N, Denmark
| | - Ole Færgeman
- Department of Internal Medicine and Cardiology, Aarhus Amtssygehus University Hospital, Tage Hansens Gade 2, DK-8000 Aarhus C, Denmark
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Abstract
In The Copenhagen City Heart Study, apolipoprotein B Arg3500Gln and Arg3531Cys increased plasma cholesterol 41% and 0%, lipoprotein lipase Gly188Glu, Asn291Ser, and Asp9Asn increased plasma triglycerides 42%, 13% (women only), and 13% (men only), and angiotensin converting enzyme DD increased plasma ACE activity 57%. Risk of ischemic heart disease for these mutations was sevenfold, unchanged, fivefold, twofold (women only), twofold (men only), and unchanged, respectively, compared with threefold for diabetes mellitus. The fraction of ischemic heart disease in the population at large attributed to these mutations was 0.5%, 0%, 0.3%, 5% (women only), 3% (men only), and 0%, respectively, compared with 7% for diabetes mellitus.
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Affiliation(s)
- B G Nordestgaard
- Herlev University Hospitals and The Copenhagen City Heart Study, Copenhagen, Denmark
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Orlova EV, Sherman MB, Chiu W, Mowri H, Smith LC, Gotto AM. Three-dimensional structure of low density lipoproteins by electron cryomicroscopy. Proc Natl Acad Sci U S A 1999; 96:8420-5. [PMID: 10411890 PMCID: PMC17531 DOI: 10.1073/pnas.96.15.8420] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human low density lipoproteins (LDL) are the major cholesterol carriers in the blood. Elevated concentration of LDL is a major risk factor for atherosclerotic disease. Purified LDL particles appear heterogeneous in images obtained with a 400-kV electron cryomicroscope. Using multivariate statistical and cluster analyses, an ensemble of randomly oriented particle images has been subdivided into homogeneous subpopulations, and the largest subset was used for three-dimensional reconstruction. In contrast to the general belief that below the lipid phase-transition temperature (30 degrees C) LDL are quasi-spherical microemulsion particles with a radially layered core-shell organization, our three-dimensional map shows that LDL have a well-defined and stable organization. Particles consist of a higher-density outer shell and lower-density inner lamellae-like layers that divide the core into compartments. The outer shell consists of apolipoprotein B-100, phospholipids, and some free cholesterol.
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Affiliation(s)
- E V Orlova
- Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
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