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Hartz J. Low LDL-C: Is It all Good News? Curr Atheroscler Rep 2024; 26:673-681. [PMID: 39254830 DOI: 10.1007/s11883-024-01238-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2024] [Indexed: 09/11/2024]
Abstract
PURPOSE OF REVIEW This review presents the risks and benefits of very low LDL cholesterol and the safety of using lipid-lowering therapy to achieve these levels. RECENT FINDINGS A growing body of literature suggests that lower LDL cholesterol levels are associated with a reduced risk of cardiovascular disease. Further, achieving these levels with pharmaceuticals is remarkably safe. Although statins may slightly increase the risk of diabetes mellitus and hemorrhagic stroke, the benefits outweigh the risks. While recommendations from professional societies are increasingly aggressive, additional risk reduction could be achieved by setting more even ambitious LDL cholesterol goals.
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Affiliation(s)
- Jacob Hartz
- Boston Children's Hospital, 300 Longwood Ave, Boston, MA, 02115, USA.
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2
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Tada H, Kojima N, Nomura A, Takamura M. A Family with Familial Hypobetalipoproteinemia Caused by a c.1468C>T in APOB. Intern Med 2024; 63:2637-2640. [PMID: 38369355 PMCID: PMC11518604 DOI: 10.2169/internalmedicine.3033-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 12/27/2023] [Indexed: 02/20/2024] Open
Abstract
We herein report the first family of Japanese individuals with familial hypobetalipoproteinemia caused by the c.1468C>T mutation in apolipoprotein B (APOB). A 13-year-old boy with extremely low levels of low-density lipoprotein (LDL) cholesterol (24 mg/dL) was referred to our hospital. The patient had no secondary causes of hypobetalipoproteinemia. His father and grandmother also exhibited low LDL cholesterol levels. A genetic analysis confirmed that they all had this variant in APOB (c.1468C>T). None of the patients exhibited atherosclerotic cardiovascular diseases or any other complications associated with low LDL cholesterol levels, including fatty liver, neurocognitive disorders, and cerebral hemorrhaging.
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Affiliation(s)
- Hayato Tada
- Department of Cardiology, Kanazawa University Graduate School of Medicine, Japan
| | - Nobuko Kojima
- Department of Cardiology, Kanazawa University Graduate School of Medicine, Japan
| | - Akihiro Nomura
- Department of Cardiology, Kanazawa University Graduate School of Medicine, Japan
| | - Masayuki Takamura
- Department of Cardiology, Kanazawa University Graduate School of Medicine, Japan
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3
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Strøm TB, Asprusten E, Laerdahl JK, Øygard I, Hussain MM, Bogsrud MP, Leren TP. Missense mutation Q384K in the APOB gene affecting the large lipid transfer module of apoB reduces the secretion of apoB-100 in the liver without reducing the secretion of apoB-48 in the intestine. J Clin Lipidol 2023; 17:800-807. [PMID: 37718180 DOI: 10.1016/j.jacl.2023.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 08/10/2023] [Accepted: 08/26/2023] [Indexed: 09/19/2023]
Abstract
BACKGROUND Molecular genetic testing of patients with hypobetalipoproteinemia may identify a genetic cause that can form the basis for starting proper therapy. Identifying a genetic cause may also provide novel data on the structure-function relationship of the mutant protein. OBJECTIVE To identify a genetic cause of hypobetalipoproteinemia in a patient with levels of low density lipoprotein cholesterol at the detection limit of 0.1 mmol/l. METHODS DNA sequencing of the translated exons with flanking intron sequences of the genes adenosine triphosphate-binding cassette transporter 1, angiopoietin-like protein 3, apolipoprotein B, apolipoprotein A1, lecithin-cholesterol acyltransferase, microsomal triglyceride transfer protein and proprotein convertase subtilisin/kexin type 9. RESULTS The patient was homozygous for mutation Q384K (c.1150C>A) in the apolipoprotein B gene, and this mutation segregated with hypobetalipoproteinemia in the family. Residue Gln384 is located in the large lipid transfer module of apoB that has been suggested to be important for lipidation of apolipoprotein B through interaction with microsomal triglyceride transfer protein. Based on measurements of serum levels of triglycerides and apolipoprotein B-48 after an oral fat load, we conclude that the patient was able to synthesize apolipoprotein B-48 in the intestine in a seemingly normal fashion. CONCLUSION Our data indicate that mutation Q384K severely reduces the secretion of apolipoprotein B-100 in the liver without reducing the secretion of apolipoprotein B-48 in the intestine. Possible mechanisms for the different effects of this and other missense mutations affecting the large lipid transfer module on the two forms of apoB are discussed.
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Affiliation(s)
- Thea Bismo Strøm
- Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital, Oslo, Norway (Drs Strøm, Bogsrud and Leren).
| | - Emil Asprusten
- Lipid Clinic, Oslo University Hospital, Oslo, Norway (Dr Asprusten)
| | - Jon K Laerdahl
- Department of Microbiology, Oslo University Hospital, Oslo, Norway (Dr Laerdahl); ELIXIR Norway, Department of Informatics, University of Oslo, Oslo, Norway (Dr Laerdahl)
| | - Irene Øygard
- Fagernes Medical Center, Fagernes, Norway (Dr Øygard)
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY 11501, USA (Dr. Hussain)
| | - Martin Prøven Bogsrud
- Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital, Oslo, Norway (Drs Strøm, Bogsrud and Leren)
| | - Trond P Leren
- Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital, Oslo, Norway (Drs Strøm, Bogsrud and Leren)
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4
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Guidance for the diagnosis and treatment of hypolipidemia disorders. J Clin Lipidol 2022; 16:797-812. [DOI: 10.1016/j.jacl.2022.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 08/31/2022] [Indexed: 11/15/2022]
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5
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Vanhoye X, Janin A, Caillaud A, Rimbert A, Venet F, Gossez M, Dijk W, Marmontel O, Nony S, Chatelain C, Durand C, Lindenbaum P, Rieusset J, Cariou B, Moulin P, Di Filippo M. APOB CRISPR-Cas9 Engineering in Hypobetalipoproteinemia: A Promising Tool for Functional Studies of Novel Variants. Int J Mol Sci 2022; 23:4281. [PMID: 35457099 PMCID: PMC9030618 DOI: 10.3390/ijms23084281] [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: 02/13/2022] [Revised: 04/04/2022] [Accepted: 04/11/2022] [Indexed: 02/01/2023] Open
Abstract
Hypobetalipoproteinemia is characterized by LDL-cholesterol and apolipoprotein B (apoB) plasma levels below the fifth percentile for age and sex. Familial hypobetalipoproteinemia (FHBL) is mostly caused by premature termination codons in the APOB gene, a condition associated with fatty liver and steatohepatitis. Nevertheless, many families with a FHBL phenotype carry APOB missense variants of uncertain significance (VUS). We here aimed to develop a proof-of-principle experiment to assess the pathogenicity of VUS using the genome editing of human liver cells. We identified a novel heterozygous APOB-VUS (p.Leu351Arg), in a FHBL family. We generated APOB knock-out (KO) and APOB-p.Leu351Arg knock-in Huh7 cells using CRISPR-Cas9 technology and studied the APOB expression, synthesis and secretion by digital droplet PCR and ELISA quantification. The APOB expression was decreased by 70% in the heterozygous APOB-KO cells and almost abolished in the homozygous-KO cells, with a consistent decrease in apoB production and secretion. The APOB-p.Leu351Arg homozygous cells presented with a 40% decreased APOB expression and undetectable apoB levels in cellular extracts and supernatant. Thus, the p.Leu351Arg affected the apoB secretion, which led us to classify this new variant as likely pathogenic and to set up a hepatic follow-up in this family. Therefore, the functional assessment of APOB-missense variants, using gene-editing technologies, will lead to improvements in the molecular diagnosis of FHBL and the personalized follow-up of these patients.
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Affiliation(s)
- Xavier Vanhoye
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
| | - Alexandre Janin
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
- Institut NeuroMyoGène, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon 1, Université de Lyon, F-69008 Lyon, France
| | - Amandine Caillaud
- Institut du Thorax, Nantes Université, CHU Nantes, CNRS, INSERM, F-44000 Nantes, France; (A.C.); (B.C.)
| | - Antoine Rimbert
- Institut du Thorax, Nantes Université, CNRS, INSERM, F-44000 Nantes, France; (A.R.); (W.D.); (P.L.)
| | - Fabienne Venet
- Laboratoire d’Immunologie, Edouard Herriot Hospital, Hospices Civils de Lyon, F-69437 Lyon, France; (F.V.); (M.G.)
- Centre International de Recherche en Infectiologie (CIRI), INSERM U1111, CNRS, UMR5308, Ecole Normale Supérieure de Lyon, Université Claude Bernard-Lyon 1, F-69364 Lyon, France
| | - Morgane Gossez
- Laboratoire d’Immunologie, Edouard Herriot Hospital, Hospices Civils de Lyon, F-69437 Lyon, France; (F.V.); (M.G.)
- Centre International de Recherche en Infectiologie (CIRI), INSERM U1111, CNRS, UMR5308, Ecole Normale Supérieure de Lyon, Université Claude Bernard-Lyon 1, F-69364 Lyon, France
| | - Wieneke Dijk
- Institut du Thorax, Nantes Université, CNRS, INSERM, F-44000 Nantes, France; (A.R.); (W.D.); (P.L.)
| | - Oriane Marmontel
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, F-69364 Lyon, France; (C.D.); (J.R.); (P.M.)
| | - Séverine Nony
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
| | - Charlotte Chatelain
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
| | - Christine Durand
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, F-69364 Lyon, France; (C.D.); (J.R.); (P.M.)
| | - Pierre Lindenbaum
- Institut du Thorax, Nantes Université, CNRS, INSERM, F-44000 Nantes, France; (A.R.); (W.D.); (P.L.)
| | - Jennifer Rieusset
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, F-69364 Lyon, France; (C.D.); (J.R.); (P.M.)
| | - Bertrand Cariou
- Institut du Thorax, Nantes Université, CHU Nantes, CNRS, INSERM, F-44000 Nantes, France; (A.C.); (B.C.)
| | - Philippe Moulin
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, F-69364 Lyon, France; (C.D.); (J.R.); (P.M.)
- Fédération d’Endocrinologie, Maladies Métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, F-69677 Bron, France
| | - Mathilde Di Filippo
- Service de Biochimie et de Biologie Moléculaire, Laboratoire de Biologie Médicale MultiSites, Hospices Civils de Lyon, F-69677 Bron, France; (X.V.); (A.J.); (O.M.); (S.N.); (C.C.)
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, F-69364 Lyon, France; (C.D.); (J.R.); (P.M.)
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6
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Domenech M, Llano-Rivas I, Arroyo V, Ortega E. Novel APOB mutation in familial hypobetalipoproteinemia. J Clin Lipidol 2021; 16:28-32. [PMID: 34852964 DOI: 10.1016/j.jacl.2021.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 10/19/2022]
Affiliation(s)
- M Domenech
- Lipid and Vascular Risk Unit, Endocrinology and Nutrition Department, Hospital Clinic of Barcelona, Spain; Faculty of Medicine and Health Sciences. University of Barcelona. Spain; Biomedical Research Networking Center for Physiopathology of Obesity and Nutrition (CIBEROBN). Institute of Health Carlos III, ISCIII. Spain
| | - Isabel Llano-Rivas
- Clinical Genetics, Genetic Service. Hospital Universitario Cruces, Basque Country, Spain
| | - Vicente Arroyo
- EF Clif, EASL-CLIF Consortium and Grifols Chair, Barcelona, Spain
| | - Emilio Ortega
- Lipid and Vascular Risk Unit, Endocrinology and Nutrition Department, Hospital Clinic of Barcelona, Spain; Faculty of Medicine and Health Sciences. University of Barcelona. Spain; Biomedical Research Networking Center for Physiopathology of Obesity and Nutrition (CIBEROBN). Institute of Health Carlos III, ISCIII. Spain.
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7
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Martínez-Hervás S, Real-Collado JT, Ascaso-Gimilio JF. Hypotriglyceridemias/hypolipidemias. CLINICA E INVESTIGACION EN ARTERIOSCLEROSIS : PUBLICACION OFICIAL DE LA SOCIEDAD ESPANOLA DE ARTERIOSCLEROSIS 2021; 33 Suppl 2:63-68. [PMID: 34006356 DOI: 10.1016/j.arteri.2020.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 12/31/2020] [Indexed: 06/12/2023]
Abstract
Hypolipoproteinemias are characterized by a decrease in the plasma concentration of lipoproteins. Within them, we find two groups: hypobetalipoproteinemias (HBL), due to a decrease in the plasma concentration of lipoproteins containing apolipoprotein B, and hypoalphalipoproteinemias. Hypolipoproteinemias can be classified according to their origin, into primary and secondary. Primary HBLs are rare entities produced by mutations in different genes. So far, more than 140 mutations have been identified in the APOB, PCSK9, ANGPTL3, MTTP, and SAR1 genes. Early diagnosis and treatment are essential to avoid the development of serious complications. In this review we address the diagnosis and treatment of HBL, especially those in which there is hypotriglyceridemia.
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Affiliation(s)
- Sergio Martínez-Hervás
- Servicio de Endocrinología y Nutrición, Hospital Clínico Universitario de Valencia-INCLIVA, Valencia, España; Departamento de Medicina, Universitat de Valencia, Valencia, España; CIBER de Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Valencia, España.
| | - José Tomás Real-Collado
- Servicio de Endocrinología y Nutrición, Hospital Clínico Universitario de Valencia-INCLIVA, Valencia, España; Departamento de Medicina, Universitat de Valencia, Valencia, España; CIBER de Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Valencia, España
| | - Juan Francisco Ascaso-Gimilio
- Departamento de Medicina, Universitat de Valencia, Valencia, España; CIBER de Diabetes y Enfermedades Metabólicas asociadas (CIBERDEM), Valencia, España
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8
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Rimbert A, Vanhoye X, Coulibaly D, Marrec M, Pichelin M, Charrière S, Peretti N, Valéro R, Wargny M, Carrié A, Lindenbaum P, Deleuze JF, Genin E, Redon R, Rollat-Farnier PA, Goxe D, Degraef G, Marmontel O, Divry E, Bigot-Corbel E, Moulin P, Cariou B, Di Filippo M. Phenotypic Differences Between Polygenic and Monogenic Hypobetalipoproteinemia. Arterioscler Thromb Vasc Biol 2020; 41:e63-e71. [PMID: 33207932 DOI: 10.1161/atvbaha.120.315491] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
OBJECTIVE Primary hypobetalipoproteinemia is characterized by LDL-C (low-density lipoprotein cholesterol) concentrations below the fifth percentile. Primary hypobetalipoproteinemia mostly results from heterozygous mutations in the APOB (apolipoprotein B) and PCSK9 genes, and a polygenic origin is hypothesized in the remaining cases. Hypobetalipoproteinemia patients present an increased risk of nonalcoholic fatty liver disease and steatohepatitis. Here, we compared hepatic alterations between monogenic, polygenic, and primary hypobetalipoproteinemia of unknown cause. Approach and Results: Targeted next-generation sequencing was performed in a cohort of 111 patients with hypobetalipoproteinemia to assess monogenic and polygenic origins using an LDL-C-dedicated polygenic risk score. Forty patients (36%) had monogenic hypobetalipoproteinemia, 38 (34%) had polygenic hypobetalipoproteinemia, and 33 subjects (30%) had hypobetalipoproteinemia from an unknown cause. Patients with monogenic hypobetalipoproteinemia had lower LDL-C and apolipoprotein B plasma levels compared with those with polygenic hypobetalipoproteinemia. Liver function was assessed by hepatic ultrasonography and liver enzymes levels. Fifty-nine percent of patients with primary hypobetalipoproteinemia presented with liver steatosis, whereas 21% had increased alanine aminotransferase suggestive of liver injury. Monogenic hypobetalipoproteinemia was also associated with an increased prevalence of liver steatosis (81% versus 29%, P<0.001) and liver injury (47% versus 0%) compared with polygenic hypobetalipoproteinemia. CONCLUSIONS This study highlights the importance of genetic diagnosis in the clinical care of primary hypobetalipoproteinemia patients. It shows for the first time that a polygenic origin of hypobetalipoproteinemia is associated with a lower risk of liver steatosis and liver injury versus monogenic hypobetalipoproteinemia. Thus, polygenic risk score is a useful tool to establish a more personalized follow-up of primary hypobetalipoproteinemia patients.
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Affiliation(s)
- Antoine Rimbert
- Université de Nantes, CNRS, INSERM, l'institut du thorax, France (A.R., M.P., M.W., P.L., R.R., B.C.)
| | - Xavier Vanhoye
- Hospices Civils de Lyon, UF Dyslipidémies Service de Biochimie et de Biologie Moléculaire Grand Est, Bron, France (X.V., D.C., O.M., E.D., M.D.F.)
| | - Dramane Coulibaly
- Hospices Civils de Lyon, UF Dyslipidémies Service de Biochimie et de Biologie Moléculaire Grand Est, Bron, France (X.V., D.C., O.M., E.D., M.D.F.)
| | - Marie Marrec
- L'institut du thorax, CHU NANTES, CIC INSERM 1413, France (M.M., M.P., M.W., B.C.)
| | - Matthieu Pichelin
- L'institut du thorax, CHU NANTES, CIC INSERM 1413, France (M.M., M.P., M.W., B.C.)
| | - Sybil Charrière
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, France (S.C., N.P., O.M., P.M., M.D.F.).,Hospices Civils de Lyon, Fédération d'endocrinologie, maladies métaboliques, diabète et nutrition, Hôpital Louis Pradel, Bron, France (S.C., P.M.)
| | - Noël Peretti
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, France (S.C., N.P., O.M., P.M., M.D.F.).,Hospices Civils de Lyon, Service de Gastroentérologie Hépatologie et Nutrition Pédiatrique, HFME, Bron, France (N.P.)
| | - René Valéro
- Aix Marseille Univ, APHM, INSERM, INRAE, C2VN, University Hospital La Conception, Department of Nutrition, Metabolic Diseases and Endocrinology, Marseille, France (R.V.)
| | - Matthieu Wargny
- Université de Nantes, CNRS, INSERM, l'institut du thorax, France (A.R., M.P., M.W., P.L., R.R., B.C.).,L'institut du thorax, CHU NANTES, CIC INSERM 1413, France (M.M., M.P., M.W., B.C.)
| | - Alain Carrié
- Sorbonne Universite, Inserm UMR_S116, Institute of Cardiometabolism and Nutrition (ICAN), Hopital Pitie-Salpetriere 75651 Paris, France (A.C.).,UF de génétique de l'Obésité et des Dyslipidémies, Laboratoire de Biochimie Endocrinienne et Oncologique, APHP, Sorbonne Université, Hôpital de la Pitié-salpêtrière, Paris, France (A.C.)
| | - Pierre Lindenbaum
- Université de Nantes, CNRS, INSERM, l'institut du thorax, France (A.R., M.P., M.W., P.L., R.R., B.C.)
| | - Jean-François Deleuze
- Centre National de Recherche en Génomique Humaine, Institut de Génomique, CEA, Evry, France (J.-F.D.)
| | - Emmanuelle Genin
- Inserm, Univ Brest, EFS, CHU Brest, UMR 1078, GGB, France (E.G.)
| | - Richard Redon
- Université de Nantes, CNRS, INSERM, l'institut du thorax, France (A.R., M.P., M.W., P.L., R.R., B.C.)
| | | | - Didier Goxe
- CPAM, Centre d'examens de santé de la CPAM de la Vendée, La Roche-sur-Yon, France (D.G.)
| | | | - Oriane Marmontel
- Hospices Civils de Lyon, UF Dyslipidémies Service de Biochimie et de Biologie Moléculaire Grand Est, Bron, France (X.V., D.C., O.M., E.D., M.D.F.).,CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, France (S.C., N.P., O.M., P.M., M.D.F.)
| | - Eléonore Divry
- Hospices Civils de Lyon, UF Dyslipidémies Service de Biochimie et de Biologie Moléculaire Grand Est, Bron, France (X.V., D.C., O.M., E.D., M.D.F.)
| | - Edith Bigot-Corbel
- Laboratoire de Biochimie, CHU de Nantes, Hôpital G et R Laënnec, Bd Jacques Monod, Saint-Herblain (E.B.-C.)
| | - Philippe Moulin
- CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, France (S.C., N.P., O.M., P.M., M.D.F.).,Hospices Civils de Lyon, Fédération d'endocrinologie, maladies métaboliques, diabète et nutrition, Hôpital Louis Pradel, Bron, France (S.C., P.M.)
| | - Bertrand Cariou
- Université de Nantes, CNRS, INSERM, l'institut du thorax, France (A.R., M.P., M.W., P.L., R.R., B.C.).,L'institut du thorax, CHU NANTES, CIC INSERM 1413, France (M.M., M.P., M.W., B.C.)
| | - Mathilde Di Filippo
- Hospices Civils de Lyon, UF Dyslipidémies Service de Biochimie et de Biologie Moléculaire Grand Est, Bron, France (X.V., D.C., O.M., E.D., M.D.F.).,CarMen Laboratory, INSERM, INRA, INSA Lyon, Université Claude Bernard Lyon 1, Pierre-Bénite, France (S.C., N.P., O.M., P.M., M.D.F.)
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9
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Koerner CM, Roberts BS, Neher SB. Endoplasmic reticulum quality control in lipoprotein metabolism. Mol Cell Endocrinol 2019; 498:110547. [PMID: 31442546 PMCID: PMC6814580 DOI: 10.1016/j.mce.2019.110547] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 08/16/2019] [Accepted: 08/17/2019] [Indexed: 12/26/2022]
Abstract
Lipids play a critical role in energy metabolism, and a suite of proteins is required to deliver lipids to tissues. Several of these proteins require an intricate endoplasmic reticulum (ER) quality control (QC) system and unique secondary chaperones for folding. Key examples include apolipoprotein B (apoB), which is the primary scaffold for many lipoproteins, dimeric lipases, which hydrolyze triglycerides from circulating lipoproteins, and the low-density lipoprotein receptor (LDLR), which clears cholesterol-rich lipoproteins from the circulation. ApoB requires specialized proteins for lipidation, dimeric lipases lipoprotein lipase (LPL) and hepatic lipase (HL) require a transmembrane maturation factor for secretion, and the LDLR requires several specialized, domain-specific chaperones. Deleterious mutations in these proteins or their chaperones may result in dyslipidemias, which are detrimental to human health. Here, we review the ER quality control systems that ensure secretion of apoB, LPL, HL, and LDLR with a focus on the specialized chaperones required by each protein.
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Affiliation(s)
- Cari M Koerner
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA
| | - Benjamin S Roberts
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA
| | - Saskia B Neher
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, USA.
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10
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Noto D, Giammanco A, Barbagallo CM, Cefalù AB, Averna MR. Anti-PCSK9 treatment: is ultra-low low-density lipoprotein cholesterol always good? Cardiovasc Res 2019; 114:1595-1604. [PMID: 29931148 DOI: 10.1093/cvr/cvy144] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 06/08/2018] [Indexed: 12/29/2022] Open
Abstract
Anti-PCSK9 (proprotein convertase subtilisin kexin 9) monoclonal antibodies (Mab) are novel, potent lipid-lowering drugs. They demonstrated to improve the lipid profile in high cardiovascular risk patients. Anti-PCSK9 Mab inhibit the targeted low-density lipoprotein (LDL)-receptor degradation induced by PCSK9 protein and are able to reduce LDL cholesterol (LDL-C) levels on top of conventional lipid-lowering therapy. Though these drugs proved to be very safe in the short-term, little is known about the possible long-term effects, due to the short period of their marketing. The genetic low cholesterol syndromes (LCS) represent the natural models of the lipid-lowering anti-PCSK9 therapy, and a valuable opportunity to predict the long-term effects of these drugs. By looking at the clinical features of such models, we could be able to foresee possible drug-induced side effects. In the present review, the correspondences and discordances between the side effects of anti-PCSK9 therapy and the corresponding LCS models will be examined in the attempt to forecast possible long-term consequences of these novel lipid-lowering agents.
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Affiliation(s)
- Davide Noto
- Department of Bioscience Internal Medicine and Specialties, University of Palermo, Palermo, Italy
| | - Antonina Giammanco
- Department of Bioscience Internal Medicine and Specialties, University of Palermo, Palermo, Italy
| | - Carlo M Barbagallo
- Department of Bioscience Internal Medicine and Specialties, University of Palermo, Palermo, Italy
| | - Angelo B Cefalù
- Department of Bioscience Internal Medicine and Specialties, University of Palermo, Palermo, Italy
| | - Maurizio R Averna
- Department of Bioscience Internal Medicine and Specialties, University of Palermo, Palermo, Italy
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11
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In vitro functional characterization of splicing variants of the APOB gene found in familial hypobetalipoproteinemia. J Clin Lipidol 2019; 13:960-969. [PMID: 31629702 DOI: 10.1016/j.jacl.2019.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 08/22/2019] [Accepted: 09/06/2019] [Indexed: 11/23/2022]
Abstract
BACKGROUND Familial hypobetalipoproteinemia type 1 (FHBL-1) is a codominant disorder characterized by greatly reduced plasma levels of total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B. Rare exonic pathogenic variants of APOB gene (nonsense variants, minute deletions/insertions and nonsynonymous variants) have been frequently reported in subjects with FHBL-1. Also, rare intronic variants of APOB located at intron/exon junctions and assumed to affect splicing have been reported. However, the pathogenicity of most of these intronic variants remains to be established. OBJECTIVE The objective of this study was the in vitro functional characterization of six splicing variants of APOB gene identified in seven putative FHBL-1 heterozygotes. METHODS ApoB minigenes harboring each variant were expressed in COS-1 cells and their transcripts were sequenced. RESULTS Four novel variants (c.237+1G>A, c.818+5G>A, c.3000-1G>T, and c.3842+1G>A), predicted in silico to obliterate splice site activity, were found to generate abnormal transcripts. The abnormal transcripts were generated by the activation of cryptic splice sites or exon skipping. All these transcripts harbored a premature termination codon and were predicted to encode truncated apoBs devoid of function. The predicted translation products were: i) p.(Lys41Serfs*2) and p.(Val80Ilefs*10) for c.237+1G>A; ii) p.(Asn274*) for c.818+5G>A; iii) p.(Leu1001Alafs*10) for c.3000-1G>T, and iv) p.(Ser1281Argfs*2) for c.3842+1G>A. Two previously annotated rare variants (c.905-15C>G and c.1618-4G>A) with uncertain effect in silico were found to generate only wild-type transcripts. CONCLUSIONS These in vitro minigene expression studies support the assignment of pathogenicity to four novel splice site variants of APOB gene found in FHBL-1.
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12
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Needham PG, Guerriero CJ, Brodsky JL. Chaperoning Endoplasmic Reticulum-Associated Degradation (ERAD) and Protein Conformational Diseases. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033928. [PMID: 30670468 DOI: 10.1101/cshperspect.a033928] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases. In this review, we discuss the factors that constitute the ERAD machinery and detail how each step in the pathway occurs. We then highlight the underlying pathophysiology of protein conformational diseases associated with ERAD.
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Affiliation(s)
- Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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13
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Hartz J, Hegele RA, Wilson DP. Low LDL cholesterol—Friend or foe? J Clin Lipidol 2019; 13:367-373. [DOI: 10.1016/j.jacl.2019.05.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 01/19/2023]
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14
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Callea F, Giovannoni I, Sari S, Guldal E, Dalgic B, Akyol G, Sogo T, Al-Hussaini A, Maggiore G, Bartuli A, Boldrini R, Francalanci P, Bellacchio E. Fibrinogen Gamma Chain Mutations Provoke Fibrinogen and Apolipoprotein B Plasma Deficiency and Liver Storage. Int J Mol Sci 2017; 18:ijms18122717. [PMID: 29244742 PMCID: PMC5751318 DOI: 10.3390/ijms18122717] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/07/2017] [Accepted: 12/13/2017] [Indexed: 01/12/2023] Open
Abstract
p.R375W (Fibrinogen Aguadilla) is one out of seven identified mutations (Brescia, Aguadilla, Angers, Al du Pont, Pisa, Beograd, and Ankara) causing hepatic storage of the mutant fibrinogen γ. The Aguadilla mutation has been reported in children from the Caribbean, Europe, Japan, Saudi Arabia, Turkey, and China. All reported children presented with a variable degree of histologically proven chronic liver disease and low plasma fibrinogen levels. In addition, one Japanese and one Turkish child had concomitant hypo-APOB-lipoproteinemia of unknown origin. We report here on an additional child from Turkey with hypofibrinogenemia due to the Aguadilla mutation, massive hepatic storage of the mutant protein, and severe hypo-APOB-lipoproteinemia. The liver biopsy of the patient was studied by light microscopy, electron microscopy (EM), and immunohistochemistry. The investigation included the DNA sequencing of the three fibrinogen and APOB-lipoprotein regulatory genes and the analysis of the encoded protein structures. Six additional Fibrinogen Storage Disease (FSD) patients with either the Aguadilla, Ankara, or Brescia mutations were investigated with the same methodology. A molecular analysis revealed the fibrinogen gamma p.R375W mutation (Aguadilla) but no changes in the APOB and MTTP genes. APOB and MTTP genes showed no abnormalities in the other study cases. Light microscopy and EM studies of liver tissue samples from the child led to the demonstration of the simultaneous accumulation of both fibrinogen and APOB in the same inclusions. Interestingly enough, APOB-containing lipid droplets were entrapped within the fibrinogen inclusions in the hepatocytic Endoplasmic Reticulum (ER). Similar histological, immunohistochemical, EM, and molecular genetics findings were found in the other six FSD cases associated with the Aguadilla, as well as with the Ankara and Brescia mutations. The simultaneous retention of fibrinogen and APOB-lipoproteins in FSD can be detected in routinely stained histological sections. The analysis of protein structures unraveled the pathomorphogenesis of this unexpected phenomenon. Fibrinogen gamma chain mutations provoke conformational changes in the region of the globular domain involved in the "end-to-end" interaction, thus impairing the D-dimer formation. Each monomeric fibrinogen gamma chain is left with an abnormal exposure of hydrophobic patches that become available for interactions with APOB and lipids, causing their intracellular retention and impairment of export as a secondary unavoidable phenomenon.
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Affiliation(s)
- Francesco Callea
- Department Pathology and Molecular Histopathology, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
| | - Isabella Giovannoni
- Department Pathology and Molecular Histopathology, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
| | - Sinan Sari
- Department Pediatric Gastroenterology, Gazi University Ankara, 06560 Ankara, Turkey.
| | - Esendagli Guldal
- Department Pathology, Gazi University Ankara, 06560 Ankara, Turkey.
| | - Buket Dalgic
- Department Pediatric Gastroenterology, Gazi University Ankara, 06560 Ankara, Turkey.
| | - Gulen Akyol
- Department Pathology, Gazi University Ankara, 06560 Ankara, Turkey.
| | - Tsuyoshi Sogo
- Department of Pediatric Hepatology and Gastroenterology, Saiseikai Yokohama City Tobu Hospital 3-6-1, Shimosueyoshi, Tsurumi Ward, Yokohama City, Kanagawa, Japan.
| | - Abdulrahman Al-Hussaini
- Division of Pediatric Gastroenterology, Children's Specialized Hospital, King Fahad Medical City, College of Medicine, Alfaisal University Riyadh 11525, Saudi Arabia.
| | - Giuseppe Maggiore
- Section of Pediatrics, Department of Medical Sciences, University of Ferrara, University Hospital Arcispedale Sant'Anna, 44100 Ferrara, Italy.
| | - Andrea Bartuli
- Rare Disease and Medical Genetics, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
| | - Renata Boldrini
- Department Pathology and Molecular Histopathology, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
| | - Paola Francalanci
- Department Pathology and Molecular Histopathology, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
| | - Emanuele Bellacchio
- Genetics and Rare Diseases, Research Division, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
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15
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Buonuomo PS, Rabacchi C, Macchiaiolo M, Trenti C, Fasano T, Tarugi P, Bartuli A, Bertolini S, Calandra S. Incidental finding of severe hypertriglyceridemia in children. Role of multiple rare variants in genes affecting plasma triglyceride. J Clin Lipidol 2017; 11:1329-1337.e3. [PMID: 28951076 DOI: 10.1016/j.jacl.2017.08.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 08/18/2017] [Accepted: 08/25/2017] [Indexed: 12/20/2022]
Abstract
BACKGROUND The incidental finding of severe hypertriglyceridemia (HyperTG) in a child may suggest the diagnosis of familial chylomicronemia syndrome (FCS), a recessive disorder of the intravascular hydrolysis of triglyceride (TG)-rich lipoproteins. FCS may be due to pathogenic variants in lipoprotein lipase (LPL), as well as in other proteins, such as apolipoprotein C-II and apolipoprotein A-V (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface) and LMF1 (a factor required for intracellular formation of active LPL). OBJECTIVE Molecular characterization of 5 subjects in whom HyperTG was an incidental finding during infancy/childhood. METHODS We performed the parallel sequencing of 20 plasma TG-related genes. RESULTS Three children with severe HyperTG were found to be compound heterozygous for rare pathogenic LPL variants (2 nonsense, 3 missense, and 1 splicing variant). Another child was found to be homozygous for a nonsense variant of APOA5, which was also found in homozygous state in his father with longstanding HyperTG. The fifth patient with a less severe HyperTG was found to be heterozygous for a frameshift variant in LIPC resulting in a truncated Hepatic Lipase. In addition, 1 of the patients with LPL deficiency and the patient with APOA-V deficiency were also heterozygous carriers of a pathogenic variant in LIPC and LPL gene, respectively, whereas the patient with LIPC variant was also a carrier of a rare APOB missense variant. CONCLUSIONS Targeted parallel sequencing of TG-related genes is recommended to define the molecular defect in children presenting with an incidental finding of HyperTG.
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Affiliation(s)
| | - Claudio Rabacchi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - Marina Macchiaiolo
- Rare Diseases and Medical Genetics, Bambino Gesù Children Hospital, Rome, Italy
| | - Chiara Trenti
- Department of Internal Medicine, Lipid Clinic, IRCCS-Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Tommaso Fasano
- Clinical Chemistry and Endocrinology Laboratory, IRCCS-Arcispedale Santa Maria Nuova, Reggio Emilia, Italy
| | - Patrizia Tarugi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - Andrea Bartuli
- Rare Diseases and Medical Genetics, Bambino Gesù Children Hospital, Rome, Italy
| | - Stefano Bertolini
- Department of Internal Medicine, University of Genova, Genova, Italy.
| | - Sebastiano Calandra
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena & Reggio Emilia, Modena, Italy.
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16
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Yan X, Mai L, Lin C, He W, Yin G, Yu J, Huang L, Pan S. CSF-Based Analysis for Identification of Potential Serum Biomarkers of Neural Tube Defects. Neurosci Bull 2017; 33:436-444. [PMID: 28695418 DOI: 10.1007/s12264-017-0154-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 04/10/2017] [Indexed: 01/14/2023] Open
Abstract
The protein composition of cerebrospinal fluid (CSF) in neural tube defects (NTDs) remains unknown. We investigated the protein composition of CSF from 9 infants with NTDs using isobaric tags for relative and absolute quantitation (iTRAQ). We identified 568 proteins in the CSF of infants with spina bifida, which is the most common type of NTD. Among these, 18 proteins were associated with neural tube closure in the CSF during human embryonic neurulation and 5 were involved in NTDs. Based on these results, an animal model was further utilized to investigate early serum biomarkers for NTDs. We found that the myristoylated alanine-rich C-kinase substrate, Kunitz-type protease inhibitor 2, and apolipoprotein B-100 protein levels were decreased in both embryos and the sera of pregnant Sprague-Dawley rats carrying embryos with NTDs. CSF proteins may be useful in the discovery of potential serum biomarkers for NTDs.
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Affiliation(s)
- Xinyu Yan
- Department of Anatomy, Medical College of Jinan University, Guangzhou, 510632, China
| | - Lixin Mai
- Department of Anatomy, Medical College of Jinan University, Guangzhou, 510632, China
| | - Changchun Lin
- Department of Anatomy, Medical College of Jinan University, Guangzhou, 510632, China
| | - Wenji He
- Department of Anatomy, Medical College of Jinan University, Guangzhou, 510632, China.,Department of Anatomy, Gannan Medical University, Ganzhou, 341000, China
| | - Gengsheng Yin
- Department of Clinical Laboratory, The First Affiliated Hospital of Jinan University, Guangzhou, 510630, China
| | - Jiakang Yu
- Department of Pediatric Surgery, Guangzhou Children's Hospital, Guangzhou, 510623, China
| | - Lian Huang
- Department of Neurology, The First Affiliated Hospital of Jinan University, Guangzhou, 510630, China.
| | - Sanqiang Pan
- Department of Anatomy, Medical College of Jinan University, Guangzhou, 510632, China.
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17
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Noto D, Arca M, Tarugi P, Cefalù AB, Barbagallo CM, Averna MR. Association between familial hypobetalipoproteinemia and the risk of diabetes. Is this the other side of the cholesterol-diabetes connection? A systematic review of literature. Acta Diabetol 2017; 54:111-122. [PMID: 27804036 DOI: 10.1007/s00592-016-0931-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 10/09/2016] [Indexed: 02/03/2023]
Abstract
Statin therapy is beneficial in reducing LDL cholesterol (LDL-C) levels and cardiovascular events, but it is associated with the risk of incident diabetes mellitus (DM). Familial hypercholesterolemia (FH) is characterized by genetically determined high levels of plasma LDL-C and a low prevalence of DM. LDL-C levels seem then inversely correlated with prevalence of DM. Familial hypobetalipoproteinemia (FHBL) represents the genetic mirror of FH in terms of LDL-C levels, very low in subjects carrying mutations of APOB, PCSK9 (FHBL1) or ANGPTL3 (FHBL2). This review explores the hypothesis that FHBL might represent also the genetic mirror of FH in terms of prevalence of DM and that it is expected to be increased in FHBL in comparison with the general population. A systematic review of published literature on FHBL was made by searching PubMed (1980-2016) for articles presenting clinical data on FHBL probands and relatives. The standardized prevalence rates of DM in FHBL1 were similar to those of the reference population, with a prevalence rate of 8.2 and 9.2%, respectively, while FHBL2 showed a 4.9% prevalence of DM. In conclusion, low LDL-C levels of FHBL do not seem connected to DM as it happens in subjects undergoing statin therapy and the diabetogenic effect of statins has to be explained by mechanisms that do not rely exclusively on the reduced levels of LDL-C. The review also summarizes the published data on the effects of FHBL on insulin sensitivity and the relationships between FH, statin therapy, FHBL1 and intracellular cholesterol metabolism, evaluating possible diabetogenic pathways.
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Affiliation(s)
- Davide Noto
- Department of Biomedicine, Internal Medicine and Medical Specialties (DIBIMIS), University of Palermo, Palermo, Italy.
- Department of Internal Medicine, Policlinico "Paolo Giaccone", Via del Vespro 141, 90127, Palermo, Italy.
| | - Marcello Arca
- Department of Internal Medicine and Allied Sciences, Unit of Atherosclerosis and Lipid Disorders, Sapienza University of Rome, Rome, Italy
| | - Patrizia Tarugi
- Department of Biomedical Sciences, University of Modena-Reggio, Modena, Italy
| | - Angelo B Cefalù
- Department of Biomedicine, Internal Medicine and Medical Specialties (DIBIMIS), University of Palermo, Palermo, Italy
| | - Carlo M Barbagallo
- Department of Biomedicine, Internal Medicine and Medical Specialties (DIBIMIS), University of Palermo, Palermo, Italy
| | - Maurizio R Averna
- Department of Biomedicine, Internal Medicine and Medical Specialties (DIBIMIS), University of Palermo, Palermo, Italy.
- Department of Internal Medicine, Policlinico "Paolo Giaccone", Via del Vespro 141, 90127, Palermo, Italy.
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18
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Rabacchi C, Bigazzi F, Puntoni M, Sbrana F, Sampietro T, Tarugi P, Bertolini S, Calandra S. Phenotypic variability in 4 homozygous familial hypercholesterolemia siblings compound heterozygous for LDLR mutations. J Clin Lipidol 2016; 10:944-952.e1. [DOI: 10.1016/j.jacl.2016.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 12/31/2022]
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19
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Magnolo L, Noto D, Cefalù AB, Averna M, Calandra S, Yao Z, Tarugi P. Characterization of a mutant form of human apolipoprotein B (Thr26_Tyr27del) associated with familial hypobetalipoproteinemia. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:371-9. [DOI: 10.1016/j.bbalip.2016.01.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 12/14/2015] [Accepted: 01/24/2016] [Indexed: 10/22/2022]
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20
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Miller SA, Hooper AJ, Mantiri GA, Marais D, Tanyanyiwa DM, McKnight J, Burnett JR. Novel APOB missense variants, A224T and V925L, in a black South African woman with marked hypocholesterolemia. J Clin Lipidol 2016; 10:604-9. [PMID: 27206948 DOI: 10.1016/j.jacl.2016.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 01/06/2016] [Accepted: 01/25/2016] [Indexed: 11/27/2022]
Abstract
BACKGROUND One genetic cause of markedly low plasma concentrations of apolipoprotein (apo) B and low density lipoprotein (LDL)-cholesterol is familial hypobetalipoproteinemia. OBJECTIVE We aimed to determine the molecular basis for the marked hypocholesterolemia consistent with heterozygous familial hypobetalipoproteinemia in a black female subject of Xhosa lineage. METHODS Coding regions of APOB, MTTP, PCSK9,ANGPTL3, SAR1B and APOC3 were sequenced, and APOE was genotyped. COS-7 cells were transfected with plasmids containing apoB variants. Western blotting was used to detect cellular and secreted apoB, and co-immunoprecipitation performed to assess binding with the microsomal triglyceride transfer protein (MTP). RESULTS Sequence analysis of the APOB gene revealed her to be heterozygous for two novel variants, c.751G>A (A224T) and c.2854G>C (V925L). She was also homozygous for the APOEε2 allele, and did not carry a PCSK9 loss-of-function mutation. Although Ala(224) is within the postulated MTP binding region in apoB, it is not conserved among mammalian species. Subsequent genotyping showed that Ala224Thr is found in a southern African population (n=654) with an allele frequency of 1.15% and is not associated with plasma lipid levels. Val(925), like Ala(224), is within the N-terminal 1000 amino acids required for lipoprotein assembly, but was not found in the population screen. However, in vitro studies showed that apoB V925L did not affect apoB48 production or secretion nor have a deleterious effect on MTP interaction with apoB. CONCLUSION Taken together, this suggests that the hypocholesterolemia in our case may be a result of being homozygous for APOEε2 with a low baseline cholesterol.
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Affiliation(s)
- Sharon A Miller
- School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia
| | - Amanda J Hooper
- School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia; School of Medicine and Pharmacology, University of Western Australia, Perth, Australia; Department of Clinical Biochemistry, PathWest Laboratory Medicine WA, Royal Perth Hospital and Fiona Stanley Hospital, Perth, Western Australia, Australia
| | - George A Mantiri
- School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia
| | - David Marais
- Division of Chemical Pathology, University of Cape Town, National Health Laboratory Service and MRC Cape Heart Group, Cape Town, South Africa
| | - Donald M Tanyanyiwa
- University of Witwatersrand and National Health Laboratory Service and Division of Human Genetics, University of Cape Town, Cape Town, South Africa
| | - James McKnight
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - John R Burnett
- School of Medicine and Pharmacology, University of Western Australia, Perth, Australia; Department of Clinical Biochemistry, PathWest Laboratory Medicine WA, Royal Perth Hospital and Fiona Stanley Hospital, Perth, Western Australia, Australia.
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Update on the molecular biology of dyslipidemias. Clin Chim Acta 2016; 454:143-85. [DOI: 10.1016/j.cca.2015.10.033] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/24/2015] [Accepted: 10/30/2015] [Indexed: 12/20/2022]
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22
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Yilmaz BS, Mungan NO, Di Leo E, Magnolo L, Artuso L, Bernardis I, Tumgor G, Kor D, Tarugi P. Homozygous familial hypobetalipoproteinemia: A Turkish case carrying a missense mutation in apolipoprotein B. Clin Chim Acta 2016; 452:185-90. [DOI: 10.1016/j.cca.2015.11.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 11/15/2022]
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23
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Hooper AJ, Heeks L, Robertson K, Champain D, Hua J, Song S, Parhofer KG, Barrett PHR, van Bockxmeer FM, Burnett JR. Lipoprotein Metabolism in APOB L343V Familial Hypobetalipoproteinemia. J Clin Endocrinol Metab 2015; 100:E1484-90. [PMID: 26323024 DOI: 10.1210/jc.2015-2731] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
CONTEXT Familial hypobetalipoproteinemia (FHBL) is a codominant disorder of lipoprotein metabolism characterized by decreased plasma concentrations of low-density lipoprotein (LDL)-cholesterol and apolipoprotein B (apoB). OBJECTIVE The objective was to examine the effect of heterozygous APOB L343V FHBL on postprandial triglyceride-rich lipoprotein (TRL) and fasting lipoprotein metabolism. METHODS Plasma incremental area under the curve apoB-48 and apoB-48 kinetics were determined after ingestion of a standardized oral fat load using compartmental modeling. Very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein (IDL)-, and LDL-apoB kinetics were determined in the fasting state using stable isotope methods and compartmental modeling. RESULTS The postprandial incremental area under the curve (0-10 h) in FHBL subjects (n = 3) was lower for large TRL-triglyceride (-77%; P < .0001), small TRL-cholesterol (-83%; P < .001), small TRL-triglyceride (-88%; P < .001), and for plasma triglyceride (-70%; P < .01) and apoB (-63%; P < .0001) compared with controls. Compartmental analysis showed that apoB-48 production was lower (-91%; P < .05) compared with controls. VLDL-apoB concentrations in FHBL subjects (n = 2) were lower by more than 75% compared with healthy, normolipidemic control subjects (P < .01). The VLDL-apoB fractional catabolic rate (FCR) was more than 5-fold higher in the FHBL subjects (P = .07). ApoB production rates and IDL- and LDL-apoB FCRs were not different between FHBL subjects and controls. CONCLUSIONS We conclude that when compared to controls, APOB L343V FHBL heterozygotes show lower TRL production with normal postprandial TRL particle clearance. In contrast, VLDL-apoB production was normal, whereas the FCR was higher in heterozygotes compared with lean control subjects. These mechanisms account for the marked hypolipidemic state observed in these FHBL subjects.
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MESH Headings
- Adult
- Amino Acid Substitution
- Apolipoprotein B-48/blood
- Apolipoprotein B-48/metabolism
- Apolipoproteins B/blood
- Apolipoproteins B/genetics
- Apolipoproteins B/metabolism
- Diet, High-Fat/adverse effects
- Down-Regulation
- Female
- Heterozygote
- Humans
- Hypobetalipoproteinemia, Familial, Apolipoprotein B/blood
- Hypobetalipoproteinemia, Familial, Apolipoprotein B/genetics
- Hypobetalipoproteinemia, Familial, Apolipoprotein B/metabolism
- Lipoproteins/blood
- Lipoproteins/metabolism
- Lipoproteins, IDL/blood
- Lipoproteins, IDL/metabolism
- Lipoproteins, VLDL/blood
- Lipoproteins, VLDL/metabolism
- Male
- Meals
- Middle Aged
- Models, Biological
- Mutation
- Postprandial Period
- Triglycerides/blood
- Triglycerides/metabolism
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Affiliation(s)
- Amanda J Hooper
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Liesl Heeks
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Ken Robertson
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Danie Champain
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Jianmin Hua
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Swithin Song
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Klaus G Parhofer
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - P Hugh R Barrett
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - Frank M van Bockxmeer
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
| | - John R Burnett
- Department of Clinical Biochemistry (A.J.H., L.H., K.R., F.M.v.B., J.R.B.), PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth WA 6000, Australia; School of Medicine and Pharmacology (A.J.H., D.C., P.H.R.B., J.R.B.), and School of Pathology and Laboratory Medicine (A.J.H., K.R.), University of Western Australia, Crawley WA 6009, Australia; Department of Radiology (J.H., S.S.), Royal Perth Hospital, Perth WA 6000, Australia; Medical Department II (K.G.P.), Grosshadern, University of Munich, 81377 Munich, Germany; and School of Surgery (F.M.v.B.), University of Western Australia, Crawley WA 6009, Australia
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Burnett JR, Hooper AJ. Vitamin E and oxidative stress in abetalipoproteinemia and familial hypobetalipoproteinemia. Free Radic Biol Med 2015; 88:59-62. [PMID: 26086616 DOI: 10.1016/j.freeradbiomed.2015.05.044] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 05/07/2015] [Accepted: 05/26/2015] [Indexed: 01/13/2023]
Abstract
Abetalipoproteinemia (ABL) and familial hypobetalipoproteinemia (FHBL) are genetic diseases characterized by low density lipoprotein deficiency. ABL presents early in life with the gastroenterological manifestations of fat malabsorption, steatorrhea, and failure to thrive, and later in life, with progressive ophthalmopathy and neuropathy as a result of deficiency of the fat-soluble vitamins A and E. Heterozygous FHBL subjects are usually asymptomatic, but may develop fatty liver disease. In homozygous (compound heterozygous) FHBL, the clinical and biochemical features are indistinguishable from those of ABL and treatment recommendations are the same: dietary fat restriction to prevent steatorrhea, and long-term high-dose vitamin E and A supplementation to prevent or at least slow the progression of neuromuscular and retinal degenerative disease. Despite their low plasma vitamin E levels, individuals with heterozygous FHBL do not require vitamin E supplementation. There are conflicting reports on whether increased oxidative stress is seen in ABL; these differences may relate to the small size of patient groups as well as differences in patient age and dose of vitamin E supplementation, or the contribution from dietary sources of vitamin E. High density lipoproteins in ABL appear to be severely oxidized yet able to inhibit platelet aggregation by binding to scavenger receptor B1. We review the role of vitamin E and oxidative stress in ABL and FHBL.
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Affiliation(s)
- John R Burnett
- Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, Australia; School of Medicine & Pharmacology, University of Western Australia, Perth, Australia.
| | - Amanda J Hooper
- Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, Australia; School of Medicine & Pharmacology, University of Western Australia, Perth, Australia; School of Pathology & Laboratory Medicine, University of Western Australia, Perth, Australia
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Identification of Novel Mutations in Spatacsin and Apolipoprotein B Genes in a Patient with Spastic Paraplegia and Hypobetalipoproteinemia. Case Rep Genet 2015; 2015:219691. [PMID: 26064709 PMCID: PMC4439468 DOI: 10.1155/2015/219691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/14/2015] [Indexed: 11/30/2022] Open
Abstract
Complicated hereditary spastic paraplegia (HSP) presents with complex neurological and nonneurological manifestations. We report a patient with autosomal recessive (AR) HSP in whom laboratory investigations revealed hypobetalipoproteinemia raising the possibility of a shared pathophysiology of these clinical features. A lipid profile of his parents disclosed a normal maternal lipid profile. However, the paternal lipid profile was similar to that of the patient suggesting autosomal dominant transmission of this trait. Whole exome sequence analysis was performed and novel mutations were detected in both the SPG11 and the APOB genes. Genetic testing of the parents showed that both APOB variants were inherited from the father while the SPG11 variants were inherited one from each parent. Our results indicate that, in this patient, the hypobetalipoproteinemia and spastic paraplegia are unrelated resulting from mutations in two independent genes. This clinical study provides support for the use of whole exome sequencing as a diagnostic tool for identification of mutations in conditions with complex presentations.
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The Janus-faced manifestations of homozygous familial hypobetalipoproteinemia due to apolipoprotein B truncations. J Clin Lipidol 2015; 9:400-5. [PMID: 26073401 DOI: 10.1016/j.jacl.2015.01.005] [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: 09/28/2014] [Revised: 12/05/2014] [Accepted: 01/18/2015] [Indexed: 11/23/2022]
Abstract
Familial hypobetalipoproteinemia is a codominant disorder characterized by low plasma levels of low-density lipoprotein cholesterol and apolipoprotein B (apoB), which in ∼50% of the cases is due to mutations in APOB gene. In most cases, these mutations cause the formation of truncated apoBs of various sizes, which have a reduced capacity to bind lipids and form lipoprotein particles. Here, we describe 2 children with severe hypobetalipoproteinemia found to be homozygous for novel APOB gene mutations. The first case (HBL-201) was an asymptomatic 13-year-old boy incidentally found to have slightly elevated serum transaminases associated with hepatic steatosis. He was homozygous for a truncated apoB (2211 amino acids, apoB-48.74) whose size is similar to that of wild-type apoB-48 (2152 amino acids) produced by the intestine. ApoB-48.74 is expected to be incorporated into chylomicrons in the intestine but might have a reduced capacity to form secretion-competent very low-density lipoprotein in the liver. The second patient (HBL-96) was a 6-month-old girl suspected to have abetalipoproteinemia, for the presence of chronic diarrhea, failure to thrive, extremely severe hypobetalipoproteinemia, and low plasma levels of vitamin E and vitamin A. She was homozygous for a nonsense mutation (Gln513*) resulting in a short truncated apoB (apoB-11.30), which is not secreted into the plasma. In this patient, the impaired chylomicron formation is responsible for the severe clinical manifestations and growth retardation. In homozygous familial hypobetalipoproteinemia, the capacity of truncated apoBs to form chylomicrons is the major factor, which affects the severity of the clinical manifestations.
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Cefalù AB, Norata GD, Ghiglioni DG, Noto D, Uboldi P, Garlaschelli K, Baragetti A, Spina R, Valenti V, Pederiva C, Riva E, Terracciano L, Zoja A, Grigore L, Averna MR, Catapano AL. Homozygous familial hypobetalipoproteinemia: two novel mutations in the splicing sites of apolipoprotein B gene and review of the literature. Atherosclerosis 2015; 239:209-17. [PMID: 25618028 DOI: 10.1016/j.atherosclerosis.2015.01.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 12/21/2014] [Accepted: 01/13/2015] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Familial hypobetalipoproteinemia (FHBL) is autosomal codominant disorder of lipoprotein metabolism characterized by low plasma levels of total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (apoB) below the 5(th) percentile of the distribution in the population. Patients with the clinical diagnosis of homozygous FHBL (Ho-FHBL) are extremely rare and few patients have been characterized at the molecular level. Here we report the medical history and the molecular characterization of one paediatric patient with clinical features of Ho-FHBL. METHODS A one month old infant with failure to thrive, severe hypocholesterolemia and acanthocytosis was clinically and genetically characterized. Molecular characterization of the proband and her parents was performed by direct sequencing of the APOB gene and functional role of the identified mutations was assessed by the minigene methodology. RESULTS The proband was found carrying two novel splicing mutations of the APOB gene (c.3696+1G > C and c.3697-1G > A). CHOK1H8 cells expressing minigenes harbouring the mutations showed that these two mutations were associated with the retention of intron 23 and skipping of exon 24, resulting in two truncated apoB fragments of approximate size of 26-28 % of ApoB-100 and the total absence of apoB. CONCLUSION We describe the first case of Ho-FHBL due to two splicing mutations affecting both the donor and the acceptor splice sites of the same intron of the APOB gene occurring in the same patient. The clinical management of the proband is discussed and a review of the clinical and genetic features of the published Ho-FHBL cases is reported.
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Affiliation(s)
- Angelo B Cefalù
- Dipartimento Biomedico di Medicina Interna e Specialistica (DIBIMIS), Università degli Studi di Palermo, Italy
| | - Giuseppe D Norata
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | | | - Davide Noto
- Dipartimento Biomedico di Medicina Interna e Specialistica (DIBIMIS), Università degli Studi di Palermo, Italy
| | - Patrizia Uboldi
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | - Katia Garlaschelli
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | - Andrea Baragetti
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy
| | - Rossella Spina
- Dipartimento Biomedico di Medicina Interna e Specialistica (DIBIMIS), Università degli Studi di Palermo, Italy
| | - Vincenza Valenti
- Dipartimento Biomedico di Medicina Interna e Specialistica (DIBIMIS), Università degli Studi di Palermo, Italy
| | - Cristina Pederiva
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Italy
| | - Enrica Riva
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Italy
| | | | - Alexa Zoja
- Department of Paediatrics, Melloni Hospital, Milano, Italy
| | - Liliana Grigore
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy; IRCCS Multimedica, Milano, Italy
| | - Maurizio R Averna
- Dipartimento Biomedico di Medicina Interna e Specialistica (DIBIMIS), Università degli Studi di Palermo, Italy.
| | - Alberico L Catapano
- Department of Pharmacology and Biomolecular Sciences, Università degli Studi di Milano, Milano, Italy; IRCCS Multimedica, Milano, Italy.
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Abstract
"Primary hypobetalipoproteinemia" refers to an eclectic group of inherited lipoprotein disorders characterized by low concentrations of or absence of low-density lipoprotein cholesterol and apolipoprotein B in plasma. Abetalipoproteinemia and homozygous familial hypobetalipoproteinemia, although caused by mutations in different genes, are clinically indistinguishable. A framework for the clinical follow-up and management of these two disorders has been proposed recently, focusing on monitoring of growth in children and preventing complications by providing specialized dietary advice and fat-soluble vitamin therapeutic regimens. Other recent publications on familial combined hypolipidemia suggest that although a reduction of angiopoietin-like 3 activity may improve insulin sensitivity, complete deficiency also reduces serum cholesterol efflux capacity and increases the risk of early vascular atherosclerotic changes, despite low low-density lipoprotein cholesterol levels. Specialist laboratories offer exon-by-exon sequence analysis for the molecular diagnosis of primary hypobetalipoproteinemia. In the future, massively parallel sequencing of panels of genes involved in dyslipidemia may play a greater role in the diagnosis of these conditions.
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Levy E. Insights from human congenital disorders of intestinal lipid metabolism. J Lipid Res 2014; 56:945-62. [PMID: 25387865 DOI: 10.1194/jlr.r052415] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Indexed: 12/24/2022] Open
Abstract
The intestine must challenge the profuse daily flux of dietary fat that serves as a vital source of energy and as an essential component of cell membranes. The fat absorption process takes place in a series of orderly and interrelated steps, including the uptake and translocation of lipolytic products from the brush border membrane to the endoplasmic reticulum, lipid esterification, Apo synthesis, and ultimately the packaging of lipid and Apo components into chylomicrons (CMs). Deciphering inherited disorders of intracellular CM elaboration afforded new insight into the key functions of crucial intracellular proteins, such as Apo B, microsomal TG transfer protein, and Sar1b GTPase, the defects of which lead to hypobetalipoproteinemia, abetalipoproteinemia, and CM retention disease, respectively. These "experiments of nature" are characterized by fat malabsorption, steatorrhea, failure to thrive, low plasma levels of TGs and cholesterol, and deficiency of liposoluble vitamins and essential FAs. After summarizing and discussing the functions and regulation of these proteins for reader's comprehension, the current review focuses on their specific roles in malabsorptions and dyslipidemia-related intestinal fat hyperabsorption while dissecting the spectrum of clinical manifestations and managements. The influence of newly discovered proteins (proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 protein) on fat absorption has also been provided. Finally, it is stressed how the overexpression or polymorphism status of the critical intracellular proteins promotes dyslipidemia and cardiometabolic disorders.
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Affiliation(s)
- Emile Levy
- Research Centre, CHU Sainte-Justine and Department of Nutrition, Université de Montréal, Montreal, Quebec H3T 1C5, Canada
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Burnett JR, Bell DA, Hooper AJ, Hegele RA. Clinical utility gene card for: Familial hypobetalipoproteinaemia (APOB)--Update 2014. Eur J Hum Genet 2014; 23:ejhg2014225. [PMID: 25335495 DOI: 10.1038/ejhg.2014.225] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 09/08/2014] [Accepted: 09/19/2014] [Indexed: 01/08/2023] Open
Affiliation(s)
- John R Burnett
- 1] Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, Western Australia, Australia [2] School of Medicine & Pharmacology, University of Western Australia, Perth, Western Australia, Australia
| | - Damon A Bell
- 1] Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, Western Australia, Australia [2] School of Medicine & Pharmacology, University of Western Australia, Perth, Western Australia, Australia
| | - Amanda J Hooper
- 1] Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, Western Australia, Australia [2] School of Medicine & Pharmacology, University of Western Australia, Perth, Western Australia, Australia [3] School of Pathology & Laboratory Medicine, University of Western Australia, Perth, Western Australia, Australia
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Fisher E, Lake E, McLeod RS. Apolipoprotein B100 quality control and the regulation of hepatic very low density lipoprotein secretion. J Biomed Res 2014; 28:178-93. [PMID: 25013401 PMCID: PMC4085555 DOI: 10.7555/jbr.28.20140019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 02/15/2014] [Indexed: 12/19/2022] Open
Abstract
Apolipoprotein B (apoB) is the main protein component of very low density lipoprotein (VLDL) and is necessary for the assembly and secretion of these triglyceride (TG)-rich particles. Following release from the liver, VLDL is converted to low density lipoprotein (LDL) in the plasma and increased production of VLDL can therefore play a detrimental role in cardiovascular disease. Increasing evidence has helped to establish VLDL assembly as a target for the treatment of dyslipidemias. Multiple factors are involved in the folding of the apoB protein and the formation of a secretion-competent VLDL particle. Failed VLDL assembly can initiate quality control mechanisms in the hepatocyte that target apoB for degradation. ApoB is a substrate for endoplasmic reticulum associated degradation (ERAD) by the ubiquitin proteasome system and for autophagy. Efficient targeting and disposal of apoB is a regulated process that modulates VLDL secretion and partitioning of TG. Emerging evidence suggests that significant overlap exists between these degradative pathways. For example, the insulin-mediated targeting of apoB to autophagy and postprandial activation of the unfolded protein response (UPR) may employ the same cellular machinery and regulatory cues. Changes in the quality control mechanisms for apoB impact hepatic physiology and pathology states, including insulin resistance and fatty liver. Insulin signaling, lipid metabolism and the hepatic UPR may impact VLDL production, particularly during the postprandial state. In this review we summarize our current understanding of VLDL assembly, apoB degradation, quality control mechanisms and the role of these processes in liver physiology and in pathologic states.
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Affiliation(s)
- Eric Fisher
- Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Elizabeth Lake
- Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Roger S McLeod
- Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, NS B3H 4R2, Canada
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Lambert G, Petrides F, Chatelais M, Blom DJ, Choque B, Tabet F, Wong G, Rye KA, Hooper AJ, Burnett JR, Barter PJ, Marais AD. Elevated plasma PCSK9 level is equally detrimental for patients with nonfamilial hypercholesterolemia and heterozygous familial hypercholesterolemia, irrespective of low-density lipoprotein receptor defects. J Am Coll Cardiol 2014; 63:2365-73. [PMID: 24632287 DOI: 10.1016/j.jacc.2014.02.538] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 01/09/2014] [Accepted: 02/11/2014] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Do elevated proprotein convertase subtilisin/kexin type 9 (PCSK9) levels constitute an even greater risk for patients who already have reduced low-density lipoprotein receptor (LDLR) levels, such as those with heterozygous familial hypercholesterolemia (HeFH)? BACKGROUND As a circulating inhibitor of LDLR, PCSK9 is an attractive target for lowering LDL-cholesterol (LDL-C) levels. METHODS Circulating PCSK9 levels were measured by enzyme-linked immunosorbent assay in nontreated patients with HeFH carrying a D206E (n = 237), V408M (n = 117), or D154N (n = 38) LDLR missense mutation and in normolipidemic controls (n = 152). Skin fibroblasts and lymphocytes were isolated from a subset of patients and grown in 0.5% serum and mevastatin with increasing amounts of recombinant PCSK9. LDLR abundance at the cell surface was determined by flow cytometry. RESULTS PCSK9 reduced LDLR expression in a dose-dependent manner in control and FH fibroblasts to similar extents, by up to 77 ± 8% and 82 ± 7%, respectively. Likewise, PCSK9 reduced LDLR abundance by 39 ± 8% in nonfamilial hypercholesterolemia (non-FH) and by 45 ± 10% in HeFH lymphocytes, irrespective of their LDLR mutation status. We found positive correlations of the same magnitude between PCSK9 and LDL-C levels in controls (beta = 0.22; p = 0.0003), D206E (beta = 0.20; p = 0.0002), V408M (beta = 0.24; p = 0.0002), and D154N (beta = 0.25; p = 0.048) patients with HeFH. The strengths of these associations were all similar. CONCLUSIONS Elevated PCSK9 levels are equally detrimental for patients with HeFH or non-FH: a 100-ng/ml increase in PCSK9 will lead to an increase in LDL-C of 0.20 to 0.25 mmol/l in controls and HeFH alike, irrespective of their LDLR mutation. This explains why patients with non-FH or HeFH respond equally well to monoclonal antibodies targeting PCSK9.
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Affiliation(s)
- Gilles Lambert
- Faculté de Médecine, Université de Nantes, UMR PhAN 1280, Nantes, France; Lipid Research Group, Heart Research Institute, Sydney, Australia.
| | - Francine Petrides
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Mathias Chatelais
- Faculté de Médecine, Université de Nantes, UMR PhAN 1280, Nantes, France
| | - Dirk J Blom
- Lipidology Division of Internal Medicine, MRC Cape Heart Group, University of Cape Town Health Science Faculty, Cape Town, South Africa
| | - Benjamin Choque
- Lipid Research Group, Heart Research Institute, Sydney, Australia
| | - Fatiha Tabet
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Gida Wong
- Lipid Research Group, Heart Research Institute, Sydney, Australia
| | - Kerry-Anne Rye
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Amanda J Hooper
- Royal Perth Hospital, Department of Clinical Biochemistry, PathWest Laboratory of Medicine WA, Perth, Australia; School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia; School of Medicine and Pharmacology, University of Western Australia, Perth, Australia
| | - John R Burnett
- Royal Perth Hospital, Department of Clinical Biochemistry, PathWest Laboratory of Medicine WA, Perth, Australia; School of Medicine and Pharmacology, University of Western Australia, Perth, Australia
| | - Philip J Barter
- Lipid Research Group, Heart Research Institute, Sydney, Australia; Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - A David Marais
- Chemical Pathology Division of Clinical Laboratory Sciences, MRC Cape Heart Group, University of Cape Town Health Science Faculty, Cape Town, South Africa
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Jiang ZG, Mukamal K, Tapper E, Robson SC, Tsugawa Y. Low LDL-C and high HDL-C levels are associated with elevated serum transaminases amongst adults in the United States: a cross-sectional study. PLoS One 2014; 9:e85366. [PMID: 24454851 PMCID: PMC3893181 DOI: 10.1371/journal.pone.0085366] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 11/25/2013] [Indexed: 01/14/2023] Open
Abstract
Background Dyslipidemia, typically recognized as high serum triglyceride, high low-density lipoprotein cholesterol (LDL-C) or low high-density lipoprotein cholesterol (HDL-C) levels, are associated with nonalcoholic fatty liver disease (NAFLD). However, low LDL-C levels could result from defects in lipoprotein metabolism or impaired liver synthetic function, and may serve as ab initio markers for unrecognized liver diseases. Whether such relationships exist in the general population has not been investigated. We hypothesized that despite common conception that low LDL-C is desirable, it might be associated with elevated liver enzymes due to metabolic liver diseases. Methods and Findings We examined the associations between alanine aminotransferase (ALT), aspartate aminotransferase (AST) and major components of serum lipid profiles in a nationally representative sample of 23,073 individuals, who had no chronic viral hepatitis and were not taking lipid-lowering medications, from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2010. ALT and AST exhibited non-linear U-shaped associations with LDL-C and HDL-C, but not with triglyceride. After adjusting for potential confounders, individuals with LDL-C less than 40 and 41–70 mg/dL were associated with 4.2 (95% CI 1.5–11.7, p = 0.007) and 1.6 (95% CI 1.1–2.5, p = 0.03) times higher odds of abnormal liver enzymes respectively, when compared with those with LDL-C values 71–100 mg/dL (reference group). Surprisingly, those with HDL-C levels above 100 mg/dL was associated with 3.2 (95% CI 2.1–5.0, p<0.001) times higher odds of abnormal liver enzymes, compared with HDL-C values of 61–80 mg/dL. Conclusions Both low LDL-C and high HDL-C, often viewed as desirable, were associated with significantly higher odds of elevated transaminases in the general U.S. adult population. Our findings underscore an underestimated biological link between lipoprotein metabolism and liver diseases, and raise a potential need for liver evaluation among over 10 million people with particularly low LDL-C or high HDL-C in the United States.
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Affiliation(s)
- Zhenghui Gordon Jiang
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kenneth Mukamal
- Division of General Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Elliot Tapper
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Simon C Robson
- Division of Gastroenterology and Hepatology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yusuke Tsugawa
- Division of General Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America ; Harvard University Interfaculty Initiative in Health Policy, Harvard University, Cambridge, Massachusetts, United States of America
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Non-alcoholic steatohepatitis-related cirrhosis in a patient with APOB L343V familial hypobetalipoproteinaemia. Clin Chim Acta 2013; 421:121-5. [DOI: 10.1016/j.cca.2013.03.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/01/2013] [Accepted: 03/01/2013] [Indexed: 01/01/2023]
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Cefalù AB, Pirruccello JP, Noto D, Gabriel S, Valenti V, Gupta N, Spina R, Tarugi P, Kathiresan S, Averna MR. A novel APOB mutation identified by exome sequencing cosegregates with steatosis, liver cancer, and hypocholesterolemia. Arterioscler Thromb Vasc Biol 2013; 33:2021-5. [PMID: 23723369 DOI: 10.1161/atvbaha.112.301101] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE In familial hypobetalipoproteinemia, fatty liver is a characteristic feature, and there are several reports of associated cirrhosis and hepatocarcinoma. We investigated a large kindred in which low-density lipoprotein cholesterol, fatty liver, and hepatocarcinoma displayed an autosomal dominant pattern of inheritance. APPROACH AND RESULTS The proband was a 25-year-old female with low plasma cholesterol and hepatic steatosis. Low plasma levels of total cholesterol and fatty liver were observed in 10 more family members; 1 member was affected by liver cirrhosis, and 4 more subjects died of either hepatocarcinoma or carcinoma on cirrhosis. To identify the causal mutation in this family, we performed exome sequencing in 2 participants with hypocholesterolemia and fatty liver. Approximately 22 400 single nucleotide variants were identified in each sample. After variant filtering, 300 novel shared variants remained. A nonsense variant, p.K2240X, attributable to an A>T mutation in exon 26 of APOB (c.6718A>T) was identified, and this variant was confirmed by Sanger sequencing. The gentotypic analysis of 16 family members in total showed that this mutation segregated with the low cholesterol trait. In addition, genotyping of the PNPLA3 p.I148M did not show significant frequency differences between carriers and noncarriers of the c.6718A>T APOB gene mutation. CONCLUSIONS We used exome sequencing to discover a novel nonsense mutation in exon 26 of APOB (p.K2240X) responsible for low cholesterol and fatty liver in a large kindred. This mutation may also be responsible for cirrhosis and liver cancer in this family.
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Affiliation(s)
- Angelo B Cefalù
- Dipartimento Biomedico di Medicina Interna e Specialistica, Università degli Studi di Palermo, Palermo, Italy
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Magnolo L, Najah M, Fancello T, Di Leo E, Pinotti E, Brini I, Gueddiche NM, Calandra S, Slimene NM, Tarugi P. Novel mutations in SAR1B and MTTP genes in Tunisian children with chylomicron retention disease and abetalipoproteinemia. Gene 2013; 512:28-34. [DOI: 10.1016/j.gene.2012.09.117] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 09/29/2012] [Indexed: 10/27/2022]
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Jiang ZG, Robson SC, Yao Z. Lipoprotein metabolism in nonalcoholic fatty liver disease. J Biomed Res 2012; 27:1-13. [PMID: 23554788 PMCID: PMC3596749 DOI: 10.7555/jbr.27.20120077] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 08/23/2012] [Accepted: 08/29/2012] [Indexed: 12/18/2022] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD), an escalating health problem worldwide, covers a spectrum of pathologies characterized by fatty accumulation in hepatocytes in early stages, with potential progression to liver inflammation, fibrosis, and failure. A close, yet poorly understood link exists between NAFLD and dyslipidemia, a constellation of abnormalities in plasma lipoproteins including triglyceride-rich very low density lipoproteins. Apolipoproteins are a group of primarily liver-derived proteins found in serum lipoproteins; they not only play an extracellular role in lipid transport between vital organs through circulation, but also play an important intracellular role in hepatic lipoprotein assembly and secretion. The liver functions as the central hub for lipoprotein metabolism, as it dictates lipoprotein production and to a significant extent modulates lipoprotein clearance. Lipoprotein metabolism is an integral component of hepatocellular lipid homeostasis and is implicated in the pathogenesis, potential diagnosis, and treatment of NAFLD.
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Affiliation(s)
- Zhenghui Gordon Jiang
- Department of Medicine, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, USA
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Guerriero CJ, Brodsky JL. The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology. Physiol Rev 2012; 92:537-76. [PMID: 22535891 DOI: 10.1152/physrev.00027.2011] [Citation(s) in RCA: 314] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.
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Affiliation(s)
- Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, PA 15260, USA
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Sun H, Samarghandi A, Zhang N, Yao Z, Xiong M, Teng BB. Proprotein Convertase Subtilisin/Kexin Type 9 Interacts With Apolipoprotein B and Prevents Its Intracellular Degradation, Irrespective of the Low-Density Lipoprotein Receptor. Arterioscler Thromb Vasc Biol 2012; 32:1585-95. [DOI: 10.1161/atvbaha.112.250043] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective—
proprotein convertase subtilisin/kexin type 9 (PCSK9) negatively regulates the low-density lipoprotein (LDL) receptor (LDLR) in hepatocytes and therefore plays an important role in controlling circulating levels of LDL-cholesterol. To date, the relationship between PCSK9 and metabolism of apolipoprotein B (apoB), the structural protein of LDL, has been controversial and remains to be clarified.
Methods and Results—
We assessed the impact of PCSK9 overexpression (≈400-fold above baseline) on apoB synthesis and secretion in 3 mouse models: wild-type C57BL/6 mice and LDLR-null mice (
Ldlr
−/−
and
Ldlr
−/−
Apobec1
−/−
). Irrespective of LDLR expression, mice transduced with the
PCSK9
gene invariably exhibited increased levels of plasma cholesterol, triacylglycerol, and apoB. Consistent with these findings, the levels of very-low-density lipoprotein and LDL were also increased whereas high-density lipoprotein levels were unchanged. Importantly, we demonstrated that endogenous PCSK9 interacted with apoB in hepatocytes. The PCSK9/apoB interaction resulted in increased production of apoB, possibly through the inhibition of intracellular apoB degradation via the autophagosome/lysosome pathway.
Conclusion—
We propose a new role for PCSK9 that involves shuttling between apoB and LDLR. The present study thus provides new insights into the action of PCSK9 in regulating apoB metabolism. Furthermore, our results indicate that targeting PCSK9 expression represents a new paradigm in therapeutic intervention against hyperlipidemia.
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Affiliation(s)
- Hua Sun
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
| | - Amin Samarghandi
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
| | - Ningyan Zhang
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
| | - Zemin Yao
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
| | - Momiao Xiong
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
| | - Ba-Bie Teng
- From the University of Texas Graduate School of Biomedical Sciences at Houston (H.S., B-B.T.); Center for Human Genetics (H.S., A.S., B-B.T.) and the Texas Therapeutics Institute (N.Z.), The Brown Foundation Institute of Molecular Medicine, the University of Texas Health Science Center at Houston, Houston, TX; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada (Z.Y.); and Human Genetics Center, School of Public Health, the University of Texas Health
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Clinical utility gene card for: Familial Hypobetalipoproteinaemia (APOB). Eur J Hum Genet 2012; 20:ejhg201285. [PMID: 22588666 DOI: 10.1038/ejhg.2012.85] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Pisciotta L, Favari E, Magnolo L, Simonelli S, Adorni MP, Sallo R, Fancello T, Zavaroni I, Ardigò D, Bernini F, Calabresi L, Franceschini G, Tarugi P, Calandra S, Bertolini S. Characterization of Three Kindreds With Familial Combined Hypolipidemia Caused by Loss-of-Function Mutations of ANGPTL3. ACTA ACUST UNITED AC 2012; 5:42-50. [DOI: 10.1161/circgenetics.111.960674] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
Angiopoietin-like protein 3 (ANGPTL3) affects lipid metabolism by inhibiting the activity of lipoprotein and endothelial lipases.
Angptl3
knockout mice have marked hypolipidemia, and heterozygous carriers of
ANGPLT3
, loss-of-function mutations were found among individuals in the lowest quartile of plasma triglycerides in population studies. Recently, 4 related individuals with primary hypolipidemia were found to be compound heterozygotes for
ANGPTL3
loss-of-function mutations.
Methods and Results—
We resequenced
ANGPTL3
in 4 members of 3 kindreds originally identified for very low levels of low-density lipoprotein cholesterol and high-density lipoprotein cholesterol (0.97±0.16 and 0.56±0.20 mmol/L, respectively) in whom no mutations of known candidate genes for monogenic hypobetalipoproteinemia and hypoalphalipoproteinemia had been detected. These subjects were found to be homozygous or compound heterozygous for
ANGPTL3
loss-of-function mutations (p.G400VfsX5, p.I19LfsX22/p.N147X) associated with the absence of ANGPTL3 in plasma. They had reduced plasma levels of triglyceride-containing lipoproteins and of HDL particles that contained only apolipoprotein A-I and pre-β–high-density lipoprotein. In addition, their apolipoprotein B–depleted sera had a reduced capacity to promote cell cholesterol efflux through the various pathways (ABCA1-, SR-BI–, and ABCG1-mediated efflux); however, these subjects had no clinical evidence of accelerated atherosclerosis. Heterozygous carriers of the
ANGPTL3
mutations had low plasma ANGPTL3 and moderately reduced low-density lipoprotein cholesterol (2.52±0.38 mmol/L) but normal plasma high-density lipoprotein cholesterol.
Conclusions—
Complete ANGPTL3 deficiency caused by loss-of-function mutations of
ANGPTL3
is associated with a recessive hypolipidemia characterized by a reduction of apolipoprotein B and apolipoprotein A-I–containing lipoproteins, changes in subclasses of high-density lipoprotein, and reduced cholesterol efflux potential of serum. Partial ANGPTL3 deficiency is associated only with a moderate reduction of low-density lipoprotein.
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Affiliation(s)
- Livia Pisciotta
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Elda Favari
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Lucia Magnolo
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Sara Simonelli
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Maria Pia Adorni
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Raffaella Sallo
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Tatiana Fancello
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Ivana Zavaroni
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Diego Ardigò
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Franco Bernini
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Laura Calabresi
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Guido Franceschini
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Patrizia Tarugi
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Sebastiano Calandra
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
| | - Stefano Bertolini
- From the Department of Internal Medicine (L.P., R.S., S.B.), University of Genoa, Genoa, Italy; Department of Pharmacological and Biological Sciences and Applied Chemistries (E.F., M.P.A., F.B.) and Department of Internal Medicine and Biomedical Sciences (I.Z., D.A.), University of Parma, Parma, Italy; Department of Biomedical Sciences (L.M., T.F., P.T., S.C.), University of Modena and Reggio Emilia, Modena, Italy; and Center E. Grossi Paoletti (S.S., L.C., G.F.), Department of Pharmacological
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Conca P, Pileggi S, Simonelli S, Boer E, Boscutti G, Magnolo L, Tarugi P, Penco S, Franceschini G, Calabresi L, Gomaraschi M. Novel missense variants in LCAT and APOB genes in an Italian kindred with familial lecithin:cholesterol acyltransferase deficiency and hypobetalipoproteinemia. J Clin Lipidol 2012; 6:244-50. [PMID: 22658148 PMCID: PMC3361081 DOI: 10.1016/j.jacl.2012.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 10/13/2011] [Accepted: 01/24/2012] [Indexed: 10/26/2022]
Abstract
BACKGROUND Lecithin:cholesterol acyltransferase (LCAT) is responsible for cholesterol esterification in plasma. Mutations of LCAT gene cause familial LCAT deficiency, a metabolic disorder characterized by hypoalphalipoproteinemia. Apolipoprotein B (apoB) is the main protein component of very-low-density lipoproteins and low-density lipoprotein (LDL). Mutations of APOB gene cause familial hypobetalipoproteinemia, a codominant disorder characterized by low plasma levels of LDL cholesterol and apoB. OBJECTIVE This was a genetic and biochemical analysis of an Italian kindred with hypobetalipoproteinemia whose proband presented with hypoalphalipoproteinemia and severe chronic kidney disease. METHODS Plasma lipids and apolipoproteins, cholesterol esterification, and high-density lipoprotein (HDL) subclass distribution were analyzed. LCAT and APOB genes were sequenced. RESULTS The proband had severe impairment of plasma cholesterol esterification and high preβ-HDL content. He was heterozygote for the novel LCAT P406L variant, as were two other family members. The proband's wife and children presented with familial hypobetalipoproteinemia and were heterozygotes for the novel apoB H1401R variant. Cholesterol esterification rate of apoB H1401R carriers was reduced, likely attributable to the low amount of circulating LDL. After renal transplantation, proband's lipid profile, HDL subclass distribution, and plasma cholesterol esterification were almost at normal levels, suggesting a mild contribution of the LCAT P406L variant to his pretransplantation severe hypoalphalipoproteinemia and impairment of plasma cholesterol esterification. CONCLUSION LCAT P406L variant had a mild effect on lipid profile, HDL subclass distribution, and plasma cholesterol esterification. ApoB H1401R variant was identified as possible cause of familial hypobetalipoproteinemia and resulted in a reduction of cholesterol esterification rate.
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Affiliation(s)
- Paola Conca
- Center E. Grossi Paoletti, Department of Pharmacological Sciences, Università degli Studi di Milano, via Balzaretti 9, 20133 Milano, Italy
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Hooper AJ, Adams LA, Burnett JR. Genetic determinants of hepatic steatosis in man. J Lipid Res 2011; 52:593-617. [PMID: 21245030 DOI: 10.1194/jlr.r008896] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hepatic steatosis is one of the most common liver disorders in the general population. The main cause of hepatic steatosis is nonalcoholic fatty liver disease (NAFLD), representing the hepatic component of the metabolic syndrome, which is characterized by type 2 diabetes, obesity, and dyslipidemia. Insulin resistance and excess adiposity are considered to play key roles in the pathogenesis of NAFLD. Although the risk factors for NAFLD are well established, the genetic basis of hepatic steatosis is largely unknown. Here we review recent progress on genomic variants and their association with hepatic steatosis and discuss the potential impact of these genetic studies on clinical practice. Identifying the genetic determinants of hepatic steatosis will lead to a better understanding of the pathogenesis and progression of NAFLD.
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Affiliation(s)
- Amanda J Hooper
- Department of Core Clinical Pathology and Biochemistry, Royal Perth Hospital, Perth, Australia
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New mutations in APOB100 involved in familial hypobetalipoproteinemia. J Clin Lipidol 2010; 4:181-4. [DOI: 10.1016/j.jacl.2010.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 02/16/2010] [Accepted: 02/16/2010] [Indexed: 11/15/2022]
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Sundaram M, Yao Z. Recent progress in understanding protein and lipid factors affecting hepatic VLDL assembly and secretion. Nutr Metab (Lond) 2010; 7:35. [PMID: 20423497 PMCID: PMC2873297 DOI: 10.1186/1743-7075-7-35] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 04/27/2010] [Indexed: 02/06/2023] Open
Abstract
Excess lipid induced metabolic disorders are one of the major existing challenges for the society. Among many different causes of lipid disorders, overproduction and compromised catabolism of triacylglycerol-rich very low density lipoproteins (VLDL) have become increasingly prevalent leading to hyperlipidemia worldwide. This review provides the latest understanding in different aspects of VLDL assembly process, including structure-function relationships within apoB, mutations in APOB causing hypobetalipoproteinemia, significance of modulating microsomal triglyceride-transfer protein activity in VLDL assembly, alterations of VLDL assembly by different fatty acid species, and hepatic proteins involved in vesicular trafficking, and cytosolic lipid droplet metabolism that contribute to VLDL assembly. The role of lipoprotein receptors and exchangeable apolipoproteins that promote or diminish VLDL assembly and secretion is discussed. New understanding on dysregulated insulin signaling as a consequence of excessive triacylglycerol-rich VLDL in the plasma is also presented. It is hoped that a comprehensive view of protein and lipid factors that contribute to molecular and cellular events associated with VLDL assembly and secretion will assist in the identification of pharmaceutical targets to reduce disease complications related to hyperlipidemia.
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Affiliation(s)
- Meenakshi Sundaram
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
| | - Zemin Yao
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
- Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
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Zhong S, Magnolo AL, Sundaram M, Zhou H, Yao EF, Di Leo E, Loria P, Wang S, Bamji-Mirza M, Wang L, McKnight CJ, Figeys D, Wang Y, Tarugi P, Yao Z. Nonsynonymous mutations within APOB in human familial hypobetalipoproteinemia: evidence for feedback inhibition of lipogenesis and postendoplasmic reticulum degradation of apolipoprotein B. J Biol Chem 2009; 285:6453-64. [PMID: 20032471 DOI: 10.1074/jbc.m109.060467] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Five nontruncating missense APOB mutations, namely A31P, G275S, L324M, G912D, and G945S, were identified in heterozygous carriers of familial hypobetalipoproteinemia (FHBL) in the Italian population. To test that the FHBL phenotype was a result of impaired hepatic secretion of mutant apoB proteins, we performed transfection studies using McA-RH7777 cells stably expressing wild type or mutant forms of human apolipoprotein B-48 (apoB-48). All mutant proteins displayed varied impairment in secretion, with G912D the least affected and A31P barely secreted. Although some A31P was degraded by proteasomes, a significant proportion of it (although inappropriately glycosylated) escaped endoplasmic reticulum (ER) quality control and presented in the Golgi compartment. Degradation of the post-ER A31P was achieved by autophagy. Expression of A31P also decreased secretion of endogenous apoB and triglycerides, yet the impaired lipoprotein secretion did not lead to lipid accumulation in the cells or ER stress. Rather, expression of genes involved in lipogenesis was down-regulated, including liver X receptor alpha, sterol regulator element-binding protein 1c, fatty acid synthase, acetyl-CoA carboxylase 1, stearoyl-CoA desaturase 1, and lipin-1. These results suggest that feedback inhibition of hepatic lipogenesis in conjunction with post-ER degradation of misfolded apoB proteins can contribute to reduce fat accumulation in the FHBL liver.
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Affiliation(s)
- Shumei Zhong
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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Pocovi M, Civeira F. Heterogeneidad clínica y genética de la hipobetalipoproteinemia. Med Clin (Barc) 2009; 133:61-2. [DOI: 10.1016/j.medcli.2009.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 10/20/2022]
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Najah M, Di Leo E, Awatef J, Magnolo L, Imene J, Pinotti E, Bahri M, Barsaoui S, Brini I, Fekih M, Slimane MN, Tarugi P. Identification of patients with abetalipoproteinemia and homozygous familial hypobetalipoproteinemia in Tunisia. Clin Chim Acta 2009; 401:51-6. [DOI: 10.1016/j.cca.2008.11.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 11/06/2008] [Indexed: 11/30/2022]
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Contois JH, McConnell JP, Sethi AA, Csako G, Devaraj S, Hoefner DM, Warnick GR. Apolipoprotein B and Cardiovascular Disease Risk: Position Statement from the AACC Lipoproteins and Vascular Diseases Division Working Group on Best Practices. Clin Chem 2009; 55:407-19. [DOI: 10.1373/clinchem.2008.118356] [Citation(s) in RCA: 231] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background: Low-density lipoprotein cholesterol (LDL-C) has been the cornerstone measurement for assessing cardiovascular risk for nearly 20 years.
Content: Recent data demonstrate that apolipoprotein B (apo B) is a better measure of circulating LDL particle number (LDL-P) concentration and is a more reliable indicator of risk than LDL-C, and there is growing support for the idea that addition of apo B measurement to the routine lipid panel for assessing and monitoring patients at risk for cardiovascular disease (CVD) would enhance patient management. In this report, we review the studies of apo B and LDL-P reported to date, discuss potential advantages of their measurement over that of LDL-C, and present information related to standardization.
Conclusions: In line with recently adopted Canadian guidelines, the addition of apo B represents a logical next step to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATPIII) and other guidelines in the US. Considering that it has taken years to educate physicians and patients regarding the use of LDL-C, changing perceptions and practices will not be easy. Thus, it appears prudent to consider using apo B along with LDL-C to assess LDL-related risk for an interim period until the superiority of apo B is generally recognized.
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