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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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Impact of IL10, MTP, SOD2, and APOE Gene Polymorphisms on the Severity of Liver Fibrosis Induced by HCV Genotype 4. Viruses 2021; 13:v13040714. [PMID: 33924242 PMCID: PMC8074775 DOI: 10.3390/v13040714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/11/2021] [Accepted: 04/14/2021] [Indexed: 12/13/2022] Open
Abstract
Complications of hepatitis C virus (HCV) chronic infection cause ~400,000 deaths worldwide annually. One complication, liver fibrosis, is influenced by host genetic factors. Genes influencing fibrosis include immune, metabolic, oxidative stress, and viral entry genes, such as interleukin 10 (IL10), microsomal triglyceride-transfer protein (MTP), superoxide dismutase-2 (SOD2), and apolipoprotein E (APOE)-encoding genes, respectively. Thus, correlating variations in these genes with HCV-induced fibrosis represents an attractive biomarker for the prognosis of fibrosis severity in chronically infected patients. Here, we aimed to test whether polymorphisms in IL10, MTP, SOD2, and APOE genes correlated with the severity of fibrosis induced by HCV genotype 4 (HCV-gt4) in a cohort of chronically infected Egyptian patients. Our results demonstrate a significant association between the severity of fibrosis and specific SNPs in IL-10, SOD2, and ApoE-encoding genes. Haplotype-combination analysis for IL10, MTP, SOD2, and APOE showed statistically significant associations between specific haplotype combinations and fibrosis severity. Identifying biomarkers correlating with the severity of HCV-gt4-induced fibrosis would significantly impact precision prophylaxis and treatment of patients at risk.
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Rodríguez Gutiérrez PG, González García JR, Castillo De León YA, Zárate Guerrero JR, Magaña Torres MT. A novel p.Gly417Valfs*12 mutation in the MTTP gene causing abetalipoproteinemia: Presentation of the first patient in Mexico and analysis of the previously reported cases. J Clin Lab Anal 2021; 35:e23672. [PMID: 33258201 PMCID: PMC7957982 DOI: 10.1002/jcla.23672] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/10/2020] [Accepted: 11/12/2020] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Our aims were to describe the first Mexican patient with abetalipoproteinemia and to perform a comparative analysis of biochemical, clinical, and genetic characteristics of 100 cases reported in the literature. METHODS We performed biochemical and molecular screenings in a Mexican girl with extremely low lipid levels and in her family. Further, we integrated and evaluated the characteristics of the cases with abetalipoproteinemia described in the literature. RESULTS Our patient is a six-year-old girl who presented vomiting, chronic diarrhea, failure to thrive, malabsorption, acanthocytosis, anemia, transaminases elevation, and extremely low lipid levels. MTTP gene sequencing revealed homozygosity for a novel mutation p.Gly417Valfs*12 (G deletion c.1250). With the analysis of the reported cases, 60 clinical features (14 classical and 46 non-classical) were observed, being the most common acanthocytosis (57.5%), malabsorption (43.7%), and diarrhea (42.5%); 48.8% of the patients presented only classic clinical features, while the remaining 51.2% developed secondary effects due to a fat-soluble vitamin deficiency. An odds ratio analysis disclosed that patients diagnosed after 10 years of age have an increased risk for presenting clinical complications (OR = 18.0; 95% CI 6.0-54.1, p < 0.0001). A great diversity of mutations in MTTP has been observed (n = 76, being the most common p.G865X and p.N139_E140) and some of them with possible residual activity. CONCLUSION The first Mexican patient with abetalipoproteinemia presents a novel MTTP mutation p.Gly417Valfs*12. Three factors that could modulate the phenotype in abetalipoproteinemia were identified: age at diagnosis, treatment, and the causal mutation.
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Affiliation(s)
- Perla Graciela Rodríguez Gutiérrez
- División de GenéticaCentro de Investigación Biomédica de OccidenteInstituto Mexicano del Seguro SocialGuadalajaraMéxico
- Doctorado en Genética HumanaCentro Universitario de Ciencias de la SaludUniversidad de GuadalajaraGuadalajaraMéxico
| | - Juan Ramón González García
- División de GenéticaCentro de Investigación Biomédica de OccidenteInstituto Mexicano del Seguro SocialGuadalajaraMéxico
| | | | | | - María Teresa Magaña Torres
- División de GenéticaCentro de Investigación Biomédica de OccidenteInstituto Mexicano del Seguro SocialGuadalajaraMéxico
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Wilson MH, Rajan S, Danoff A, White RJ, Hensley MR, Quinlivan VH, Recacha R, Thierer JH, Tan FJ, Busch-Nentwich EM, Ruddock L, Hussain MM, Farber SA. A point mutation decouples the lipid transfer activities of microsomal triglyceride transfer protein. PLoS Genet 2020; 16:e1008941. [PMID: 32760060 PMCID: PMC7444587 DOI: 10.1371/journal.pgen.1008941] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 08/18/2020] [Accepted: 06/17/2020] [Indexed: 01/08/2023] Open
Abstract
Apolipoprotein B-containing lipoproteins (B-lps) are essential for the transport of hydrophobic dietary and endogenous lipids through the circulation in vertebrates. Zebrafish embryos produce large numbers of B-lps in the yolk syncytial layer (YSL) to move lipids from yolk to growing tissues. Disruptions in B-lp production perturb yolk morphology, readily allowing for visual identification of mutants with altered B-lp metabolism. Here we report the discovery of a missense mutation in microsomal triglyceride transfer protein (Mtp), a protein that is essential for B-lp production. This mutation of a conserved glycine residue to valine (zebrafish G863V, human G865V) reduces B-lp production and results in yolk opacity due to aberrant accumulation of cytoplasmic lipid droplets in the YSL. However, this phenotype is milder than that of the previously reported L475P stalactite (stl) mutation. MTP transfers lipids, including triglycerides and phospholipids, to apolipoprotein B in the ER for B-lp assembly. In vitro lipid transfer assays reveal that while both MTP mutations eliminate triglyceride transfer activity, the G863V mutant protein unexpectedly retains ~80% of phospholipid transfer activity. This residual phospholipid transfer activity of the G863V mttp mutant protein is sufficient to support the secretion of small B-lps, which prevents intestinal fat malabsorption and growth defects observed in the mttpstl/stl mutant zebrafish. Modeling based on the recent crystal structure of the heterodimeric human MTP complex suggests the G865V mutation may block triglyceride entry into the lipid-binding cavity. Together, these data argue that selective inhibition of MTP triglyceride transfer activity may be a feasible therapeutic approach to treat dyslipidemia and provide structural insight for drug design. These data also highlight the power of yolk transport studies to identify proteins critical for B-lp biology.
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Affiliation(s)
- Meredith H. Wilson
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Sujith Rajan
- New York University Long Island School of Medicine, Mineola, New York, United States of America
| | - Aidan Danoff
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Richard J. White
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Monica R. Hensley
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Vanessa H. Quinlivan
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Rosario Recacha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - James H. Thierer
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Frederick J. Tan
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
| | - Elisabeth M. Busch-Nentwich
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom
- Cambridge Institute of Therapeutic Immunology & Infectious Disease, Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Lloyd Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - M. Mahmood Hussain
- New York University Long Island School of Medicine, Mineola, New York, United States of America
| | - Steven A. Farber
- Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland, United States of America
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
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Iqbal J, Jahangir Z, Al-Qarni AA. Microsomal Triglyceride Transfer Protein: From Lipid Metabolism to Metabolic Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1276:37-52. [DOI: 10.1007/978-981-15-6082-8_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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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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Chen L, Chen XW, Huang X, Song BL, Wang Y, Wang Y. Regulation of glucose and lipid metabolism in health and disease. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1420-1458. [PMID: 31686320 DOI: 10.1007/s11427-019-1563-3] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 10/15/2019] [Indexed: 02/08/2023]
Abstract
Glucose and fatty acids are the major sources of energy for human body. Cholesterol, the most abundant sterol in mammals, is a key component of cell membranes although it does not generate ATP. The metabolisms of glucose, fatty acids and cholesterol are often intertwined and regulated. For example, glucose can be converted to fatty acids and cholesterol through de novo lipid biosynthesis pathways. Excessive lipids are secreted in lipoproteins or stored in lipid droplets. The metabolites of glucose and lipids are dynamically transported intercellularly and intracellularly, and then converted to other molecules in specific compartments. The disorders of glucose and lipid metabolism result in severe diseases including cardiovascular disease, diabetes and fatty liver. This review summarizes the major metabolic aspects of glucose and lipid, and their regulations in the context of physiology and diseases.
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Affiliation(s)
- Ligong Chen
- School of Pharmaceutical Sciences, Beijing Advanced Innovation Center for Structural Biology, Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Tsinghua University, Beijing, 100084, China.
| | - Xiao-Wei Chen
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Bao-Liang Song
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| | - Yan Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| | - Yiguo Wang
- MOE Key Laboratory of Bioinformatics, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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Abstract
This study provides a structure for microsomal triglyceride transfer protein, a key protein in lipid metabolism and transport. Microsomal triglyceride transfer protein is linked to a human disease state, abetalipoproteinemia. The structure helps us to understand how this protein functions and gives a rationale for how previously reported mutations result in loss of function of the protein and hence, cause disease. The structure also provides a means for rational drug design to treat cardiovascular disease, hypercholesterolemia, and obesity. Microsomal triglyceride transfer protein is composed of 2 subunits. The β-subunit, protein disulfide isomerase (PDI), also acts independently as a protein folding catalyst. The structure that we present here gives insights into how PDI functions in protein folding. Microsomal triglyceride transfer protein (MTP) plays an essential role in lipid metabolism, especially in the biogenesis of very low-density lipoproteins and chylomicrons via the transfer of neutral lipids and the assembly of apoB-containing lipoproteins. Our understanding of the molecular mechanisms of MTP has been hindered by a lack of structural information of this heterodimeric complex comprising an MTPα subunit and a protein disulfide isomerase (PDI) β-subunit. The structure of MTP presented here gives important insights into the potential mechanisms of action of this essential lipid transfer molecule, structure-based rationale for previously reported disease-causing mutations, and a means for rational drug design against cardiovascular disease and obesity. In contrast to the previously reported structure of lipovitellin, which has a funnel-like lipid-binding cavity, the lipid-binding site is encompassed in a β-sandwich formed by 2 β-sheets from the C-terminal domain of MTPα. The lipid-binding cavity of MTPα is large enough to accommodate a single lipid. PDI independently has a major role in oxidative protein folding in the endoplasmic reticulum. Comparison of the mechanism of MTPα binding by PDI with previously published structures gives insights into large protein substrate binding by PDI and suggests that the previous structures of human PDI represent the “substrate-bound” and “free” states rather than differences arising from redox state.
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Di Filippo M, Collardeau Frachon S, Janin A, Rajan S, Marmontel O, Decourt C, Rubio A, Nony S, Dumont S, Cuerq C, Charrière S, Moulin P, Lachaux A, Hussain MM, Bozon D, Peretti N. Normal serum ApoB48 and red cells vitamin E concentrations after supplementation in a novel compound heterozygous case of abetalipoproteinemia. Atherosclerosis 2019; 284:75-82. [PMID: 30875496 DOI: 10.1016/j.atherosclerosis.2019.02.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 02/16/2019] [Accepted: 02/19/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND AIMS Abetalipoproteinemia (ABL) is a rare recessive monogenic disease due to MTTP (microsomal triglyceride transfer protein) mutations leading to the absence of plasma apoB-containing lipoproteins. Here we characterize a new ABL case with usual clinical phenotype, hypocholesterolemia, hypotriglyceridemia but normal serum apolipoprotein B48 (apoB48) and red blood cell vitamin E concentrations. METHODS Histology and MTP activity measurements were performed on intestinal biopsies. Mutations in MTTP were identified by Sanger sequencing, quantitative digital droplet and long-range PCR. Functional consequences of the variants were studied in vitro using a minigene splicing assay, measurement of MTP activity and apoB48 secretion. RESULTS Intestinal steatosis and the absence of measurable lipid transfer activity in intestinal protein extract supported the diagnosis of ABL. A novel MTTP c.1868G>T variant inherited from the patient's father was identified. This variant gives rise to three mRNA transcripts: one normally spliced, found at a low frequency in intestinal biopsy, carrying the p.(Arg623Leu) missense variant, producing in vitro 65% of normal MTP activity and apoB48 secretion, and two abnormally spliced transcripts resulting in a non-functional MTP protein. Digital droplet PCR and long-range sequencing revealed a previously described c.1067+1217_1141del allele inherited from the mother, removing exon 10. Thus, the patient is compound heterozygous for two dysfunctional MTTP alleles. The p.(Arg623Leu) variant may maintain residual secretion of apoB48. CONCLUSIONS Complex cases of primary dyslipidemia require the use of a cascade of different methodologies to establish the diagnosis in patients with non-classical biological phenotypes and provide better knowledge on the regulation of lipid metabolism.
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Affiliation(s)
- Mathilde Di Filippo
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France; INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France.
| | - Sophie Collardeau Frachon
- INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France; Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Institut de Pathologie, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Alexandre Janin
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France; Université de Lyon, Université Claude Bernard Lyon 1, Institut NeuroMyoGène, CNRS UMR5310, INSERM U1217, Lyon, F-69622, France.
| | - Sujith Rajan
- NYU Winthrop Hospital, 101 Mineola Blvd, Mineola, USA.
| | - Oriane Marmontel
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France; INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France.
| | - Charlotte Decourt
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Amandine Rubio
- Gastroentérologie et Nutrition Pédiatrique Hôpital Couple Enfant, CHU de Grenoble Alpes, Grenoble, F-38043, France; Laboratoire de Bioénergétique Fondamentale et Appliquée, INSERM U1055, Univ. Grenoble Alpes, F-38000, France.
| | - Séverine Nony
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Sabrina Dumont
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Charlotte Cuerq
- INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France; Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Sud, Service de Biochimie et Biologie Moléculaire, Hospices Civils de Lyon, Pierre, Benite cedex, F-69495, France.
| | - Sybil Charrière
- INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France; Fédération d'endocrinologie, maladies métaboliques, diabète et nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Philippe Moulin
- INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France; Fédération d'endocrinologie, maladies métaboliques, diabète et nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Alain Lachaux
- Service de Nutrition Pediatrique, Gastroenterologie and Hepatologie, Hôpital Femme Mère Enfants, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | | | - Dominique Bozon
- Laboratoire de Biologie Médicale Multi Sites, Centre de Biologie et de Pathologie Est, Service de Biochimie et Biologie Moléculaire Grand Est, Hospices Civils de Lyon, Bron cedex, F-69677, France.
| | - Noël Peretti
- INSERM U1060, Laboratoire Carmen, Université Lyon 1, INRA U1235, INSA de Lyon, CENS, Centre de Recherche en Nutrition Humaine Rhône Alpes, Villeurbanne F-69621, Oullins cedex, F-69921, France; Service de Nutrition Pediatrique, Gastroenterologie and Hepatologie, Hôpital Femme Mère Enfants, Hospices Civils de Lyon, Bron cedex, F-69677, France.
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Di Filippo M, Varret M, Boehm V, Rabès JP, Ferkdadji L, Abramowitz L, Dumont S, Lenaerts C, Boileau C, Joly F, Schmitz J, Samson-Bouma ME, Bonnefont-Rousselot D. Postprandial lipid absorption in seven heterozygous carriers of deleterious variants of MTTP in two abetalipoproteinemic families. J Clin Lipidol 2018; 13:201-212. [PMID: 30522860 DOI: 10.1016/j.jacl.2018.10.003] [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: 06/25/2018] [Revised: 09/25/2018] [Accepted: 10/12/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND Abetalipoproteinemia, a recessive disease resulting from deleterious variants in MTTP (microsomal triglyceride transfer protein), is characterized by undetectable concentrations of apolipoprotein B, extremely low levels of low-density lipoprotein cholesterol in the plasma, and a total inability to export apolipoprotein B-containing lipoproteins from both the intestine and the liver. OBJECTIVE To study lipid absorption after a fat load and liver function in 7 heterozygous relatives from 2 abetalipoproteinemic families, 1 previously unreported. RESULTS Both patients are compound heterozygotes for p.(Arg540His) and either c.708_709del p.(His236Glnfs*11) or c.1344+3_1344+6del on the MTTP gene. The previously undescribed patient has been followed for 22 years with ultrastructure analyses of both the intestine and the liver. In these 2 families, 5 relatives were heterozygous for p.(Arg540His), 1 for p.(His236Glnfs*11) and 1 for c.1344+3_1344+6del. In 4 heterozygous relatives, the lipid absorption was normal independent of the MTTP variant. In contrast, in 3 of them, the increase in triglyceride levels after fat load was abnormal. These subjects were additionally heterozygous carriers of Asp2213 APOB in-frame deletion, near the cytidine mRNA editing site, which is essential for intestinal apoB48 production. Liver function appeared to be normal in all the heterozygotes except for one who exhibited liver steatosis for unexplained reasons. CONCLUSION Our study suggests that a single copy of the MTTP gene may be sufficient for human normal lipid absorption, except when associated with an additional APOB gene alteration. The hepatic steatosis reported in 1 patient emphasizes the need for liver function tests in all heterozygotes until the level of risk is established.
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Affiliation(s)
- Mathilde Di Filippo
- UF Dyslipidemies, Service de Biochimie et Biologie moléculaire Grand Est, GHE, Hospices Civils de Lyon, Bron Cedex, France; Univ-Lyon, CarMeN laboratory, Inserm U1060, INRA U1397, Université Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France.
| | - Mathilde Varret
- INSERM U1148, Université Paris Diderot, Hôpital Bichat-Claude Bernard, Paris Cedex 18, France
| | - Vanessa Boehm
- Service de gastroentérologie, MICI et Assistance Nutritive, Hopital Beaujon, Hopital Beaujon (AP-HP), Université Paris VII, Paris, France. INSERM UMR1149, Centre de Recherche sur l'Inflammation Paris Montmartre (CRI), Paris, France
| | - Jean-Pierre Rabès
- INSERM U1148, Université Paris Diderot, Hôpital Bichat-Claude Bernard, Paris Cedex 18, France; AP-HP, HUPIFO, Hôpital Ambroise Paré, Laboratoire de Biochimie et Génétique Moléculaire & UVSQ, UFR des Sciences de la Santé Simone Veil, Montigny-Le-Bretonneux, France
| | - Latifa Ferkdadji
- Service d'anatomie et de cytologie pathologiques, Hôpital Robert Debré, Université Paris 7, Paris, France
| | - Laurent Abramowitz
- Service d'Hépato-Gastroentérologie, Hôpital Bichat-Claude Bernard, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris Cedex 18, France
| | - Sabrina Dumont
- UF Dyslipidemies, Service de Biochimie et Biologie moléculaire Grand Est, GHE, Hospices Civils de Lyon, Bron Cedex, France
| | | | - Catherine Boileau
- INSERM U1148, Université Paris Diderot, Hôpital Bichat-Claude Bernard, Paris Cedex 18, France
| | - Francisca Joly
- Service de gastroentérologie, MICI et Assistance Nutritive, Hopital Beaujon, Hopital Beaujon (AP-HP), Université Paris VII, Paris, France. INSERM UMR1149, Centre de Recherche sur l'Inflammation Paris Montmartre (CRI), Paris, France
| | - Jacques Schmitz
- Département de Gastroentérologie pédiatrique, Hopital Necker-Enfants Malades, Paris, France
| | | | - Dominique Bonnefont-Rousselot
- Service de Biochimie métabolique, Hôpitaux universitaires Pitié-Salpêtrière-Charles Foix (AP-HP), Paris, France; Faculté de Pharmacie de Paris, Université Paris Descartes, Sorbonne Paris Cité, Unité de Technologies Chimiques et Biologiques pour la Santé, U 1022 INSERM, UMR 8258 CNRS, Paris, France
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Walsh MT, Hussain MM. Targeting microsomal triglyceride transfer protein and lipoprotein assembly to treat homozygous familial hypercholesterolemia. Crit Rev Clin Lab Sci 2016; 54:26-48. [PMID: 27690713 DOI: 10.1080/10408363.2016.1221883] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Homozygous familial hypercholesterolemia (HoFH) is a polygenic disease arising from defects in the clearance of plasma low-density lipoprotein (LDL), which results in extremely elevated plasma LDL cholesterol (LDL-C) and increased risk of atherosclerosis, coronary heart disease, and premature death. Conventional lipid-lowering therapies, such as statins and ezetimibe, are ineffective at lowering plasma cholesterol to safe levels in these patients. Other therapeutic options, such as LDL apheresis and liver transplantation, are inconvenient, costly, and not readily available. Recently, lomitapide was approved by the Federal Drug Administration as an adjunct therapy for the treatment of HoFH. Lomitapide inhibits microsomal triglyceride transfer protein (MTP), reduces lipoprotein assembly and secretion, and lowers plasma cholesterol levels by over 50%. Here, we explain the steps involved in lipoprotein assembly, summarize the role of MTP in lipoprotein assembly, explore the clinical and molecular basis of HoFH, and review pre-clinical studies and clinical trials with lomitapide and other MTP inhibitors for the treatment of HoFH. In addition, ongoing research and new approaches underway for better treatment modalities are discussed.
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Affiliation(s)
- Meghan T Walsh
- a School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center , Brooklyn , NY , USA.,b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA
| | - M Mahmood Hussain
- b Department of Cell Biology , State University of New York Downstate Medical Center , Brooklyn , NY , USA.,c Department of Pediatrics , SUNY Downstate Medical Center , Brooklyn , NY , USA.,d VA New York Harbor Healthcare System , Brooklyn , NY , USA , and.,e Winthrop University Hospital , Mineola , NY , USA
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Walsh MT, Di Leo E, Okur I, Tarugi P, Hussain MM. Structure-function analyses of microsomal triglyceride transfer protein missense mutations in abetalipoproteinemia and hypobetalipoproteinemia subjects. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1623-1633. [PMID: 27487388 DOI: 10.1016/j.bbalip.2016.07.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 07/27/2016] [Accepted: 07/28/2016] [Indexed: 10/21/2022]
Abstract
We describe two new hypolipidemic patients with very low plasma triglyceride and apolipoprotein B (apoB) levels with plasma lipid profiles similar to abetalipoproteinemia (ABL) patients. In these patients, we identified two previously uncharacterized missense mutations in the microsomal triglyceride transfer protein (MTP) gene, R46G and D361Y, and studied their functional effects. We also characterized three missense mutations (H297Q, D384A, and G661A) reported earlier in a familial hypobetalipoproteinemia patient. R46G had no effect on MTP expression or function and supported apoB secretion. H297Q, D384A, and G661A mutants also supported apoB secretion similarly to WT MTP. Contrary to these four missense mutations, D361Y was unable to support apoB secretion. Functional analysis revealed that this mutant was unable to bind protein disulfide isomerase (PDI) or transfer lipids. The negative charge at residue 361 was critical for MTP function as D361E was able to support apoB secretion and transfer lipids. D361Y most likely disrupts the tightly packed middle α-helical region of MTP, mitigates PDI binding, abolishes lipid transfer activity, and causes ABL. On the other hand, the hypolipidemia in the other two patients was not due to MTP dysfunction. Thus, in this study of five missense mutations spread throughout MTP's three structural domains found in three hypolipidemic patients, we found that four of the mutations did not affect MTP function. Thus, novel mutations that cause severe hypolipidemia probably exist in other genes in these patients, and their recognition may identify novel proteins involved in the synthesis and/or catabolism of plasma lipoproteins.
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Affiliation(s)
- Meghan T Walsh
- School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center, Brooklyn, NY 11203, United States; Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, United States
| | - Enza Di Leo
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Ilyas Okur
- Department of Pediatric Metabolism and Nutrition, Gazi University School of Medicine, Ankara, Turkey
| | - Patrizia Tarugi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - M Mahmood Hussain
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, United States; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, United States; VA New York Harbor Healthcare System, Brooklyn, NY 11209, United States; Winthrop University Hospital, Mineola, NY 11501, United States.
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13
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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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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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Walsh MT, Iqbal J, Josekutty J, Soh J, Di Leo E, Özaydin E, Gündüz M, Tarugi P, Hussain MM. Novel Abetalipoproteinemia Missense Mutation Highlights the Importance of the N-Terminal β-Barrel in Microsomal Triglyceride Transfer Protein Function. ACTA ACUST UNITED AC 2015. [PMID: 26224785 DOI: 10.1161/circgenetics.115.001106] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The use of microsomal triglyceride transfer protein (MTP) inhibitors is limited to severe hyperlipidemias because of associated hepatosteatosis and gastrointestinal adverse effects. Comprehensive knowledge about the structure-function of MTP might help design new molecules that avoid steatosis. Characterization of mutations in MTP causing abetalipoproteinemia has revealed that the central α-helical and C-terminal β-sheet domains are important for protein disulfide isomerase binding and lipid transfer activity. Our aim was to identify and characterize mutations in the N-terminal domain to understand its function. METHODS AND RESULTS We identified a novel missense mutation (D169V) in a 4-month-old Turkish male child with severe signs of abetalipoproteinemia. To study the effect of this mutation on MTP function, we created mutants via site-directed mutagenesis. Although D169V was expressed in the endoplasmic reticulum and interacted with apolipoprotein B (apoB) 17, it was unable to bind protein disulfide isomerase, transfer lipids, and support apoB secretion. Computational modeling suggested that D169 could form an internal salt bridge with K187 and K189. Mutagenesis of these lysines to leucines abolished protein disulfide isomerase heterodimerization, lipid transfer, and apoB secretion, without affecting apoB17 binding. Furthermore, mutants with preserved charges (D169E, K187R, and K189R) rescued these activities. CONCLUSIONS D169V is detrimental because it disrupts an internal salt bridge leading to loss of protein disulfide isomerase binding and lipid transfer activities; however, it does not affect apoB binding. Thus, the N-terminal domain of MTP is also important for its lipid transfer activity.
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Affiliation(s)
- Meghan T Walsh
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Jahangir Iqbal
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Joby Josekutty
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - James Soh
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Enza Di Leo
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Eda Özaydin
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Mehmet Gündüz
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - Patrizia Tarugi
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.)
| | - M Mahmood Hussain
- From the School of Graduate Studies, Molecular and Cell Biology Program (M.T.W., J.J., J.S.), Department of Cell Biology (M.T.W., J.I., J.J., J.S., M.M.H.), Department of Pediatrics (M.M.H.), State University of New York Downstate Medical Center, Brooklyn, NY; Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy (E.D.L., P.T.); Infancy Services, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (E.O); Department of Nutrition and Metabolism, Ankara Children's Health and Diseases Hematology-Oncology Training and Research Hospital, Ankara, Turkey (M.G.); and Department of Research, VA New York Harbor Healthcare System, Brooklyn, NY (M.M.H.).
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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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Hooper AJ, Burnett JR, Watts GF. Contemporary Aspects of the Biology and Therapeutic Regulation of the Microsomal Triglyceride Transfer Protein. Circ Res 2015; 116:193-205. [DOI: 10.1161/circresaha.116.304637] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Amanda J. Hooper
- Department of Clinical Biochemistry, PathWest Laboratory Medicine WA (A.J.H., J.R.B.), School of Medicine and Pharmacology (A.J.H., J.R.B., G.F.W.), School of Pathology and Laboratory Medicine (A.J.H), and Lipid Disorders Clinic, Cardiovascular Medicine (J.R.B., G.F.W), Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia
| | - John R. Burnett
- Department of Clinical Biochemistry, PathWest Laboratory Medicine WA (A.J.H., J.R.B.), School of Medicine and Pharmacology (A.J.H., J.R.B., G.F.W.), School of Pathology and Laboratory Medicine (A.J.H), and Lipid Disorders Clinic, Cardiovascular Medicine (J.R.B., G.F.W), Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia
| | - Gerald F. Watts
- Department of Clinical Biochemistry, PathWest Laboratory Medicine WA (A.J.H., J.R.B.), School of Medicine and Pharmacology (A.J.H., J.R.B., G.F.W.), School of Pathology and Laboratory Medicine (A.J.H), and Lipid Disorders Clinic, Cardiovascular Medicine (J.R.B., G.F.W), Royal Perth Hospital, University of Western Australia, Perth, Western Australia, Australia
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18
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Di Filippo M, Moulin P, Roy P, Samson-Bouma ME, Collardeau-Frachon S, Chebel-Dumont S, Peretti N, Dumortier J, Zoulim F, Fontanges T, Parini R, Rigoldi M, Furlan F, Mancini G, Bonnefont-Rousselot D, Bruckert E, Schmitz J, Scoazec JY, Charrière S, Villar-Fimbel S, Gottrand F, Dubern B, Doummar D, Joly F, Liard-Meillon ME, Lachaux A, Sassolas A. Homozygous MTTP and APOB mutations may lead to hepatic steatosis and fibrosis despite metabolic differences in congenital hypocholesterolemia. J Hepatol 2014; 61:891-902. [PMID: 24842304 DOI: 10.1016/j.jhep.2014.05.023] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 04/16/2014] [Accepted: 05/06/2014] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Non-alcoholic steatohepatitis leading to fibrosis occurs in patients with abetalipoproteinemia (ABL) and homozygous or compound heterozygous familial hypobetalipoproteinemia (Ho-FHBL). We wanted to establish if liver alterations were more frequent in one of both diseases and were influenced by comorbidities. METHODS We report genetic, clinical, histological and biological characteristics of new cases of ABL (n =7) and Ho-FHBL (n = 7), and compare them with all published ABL (51) and Ho-FHBL (22) probands. RESULTS ABL patients, diagnosed during infancy, presented mainly with diarrhea, neurological and ophthalmological impairments and remained lean, whereas Ho-FHBL were diagnosed later, with milder symptoms often becoming overweight in adulthood. Despite subtle differences in lipid phenotype, liver steatosis was observed in both groups with a high prevalence of severe fibrosis (5/27 for Ho-FHBL vs. 4/58 for ABL (n.s.)). Serum triglycerides concentration was higher in Ho-FHBL whereas total and HDL-cholesterol were similar in both groups. In Ho-FHBL liver alterations were found to be independent from the apoB truncation size and apoB concentrations. CONCLUSIONS Our findings provide evidence for major liver abnormalities in both diseases. While ABL and Ho-FHBL patients have subtle differences in lipid phenotype, carriers of APOB mutations are more frequently obese. These results raise the question of a complex causal link between apoB metabolism and obesity. They suggest that the genetic defect in VLDL assembly is critical for the occurrence of liver steatosis leading to fibrosis and shows that obesity and insulin resistance might contribute by increasing lipogenesis.
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Affiliation(s)
- Mathilde Di Filippo
- UF Dyslipidémies Cardiobiologie, Département de Biochimie et de Biologie Moléculaire du GHE, Laboratoire de Biologie Médicale Multi Sites, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INSA de Lyon, INRA U1235, Univ Lyon-1, Université de Lyon, Villeurbanne, Oullins, France.
| | - Philippe Moulin
- INSERM U1060, INSA de Lyon, INRA U1235, Univ Lyon-1, Université de Lyon, Villeurbanne, Oullins, France; Fédération d'Endocrinologie, Maladies métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Bron, France
| | - Pascal Roy
- Service de Biostatistique, Hospices Civils de Lyon, Lyon, France; Centre National de la Recherche Scientifique UMR5558, Univ Lyon-1, Villeurbanne, France
| | | | | | - Sabrina Chebel-Dumont
- UF Dyslipidémies Cardiobiologie, Département de Biochimie et de Biologie Moléculaire du GHE, Laboratoire de Biologie Médicale Multi Sites, Hospices Civils de Lyon, Lyon, France
| | - Noël Peretti
- Service de Gastroentérologie Hépatologie et Nutrition Pédiatrique, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Bron, France
| | - Jérôme Dumortier
- Fédération des Spécialités Digestives, Hôpital Edouard Herriot, Hospices Civils, Lyon, France
| | - Fabien Zoulim
- Service d'Hépato-Gastro-Entérologie, Hôpital de la Croix Rousse, Hospices Civils, Lyon, France
| | - Thierry Fontanges
- Service d'Hépato-Gastro-Entérologie, Centre Hospitalier Pierre Oudot, Bourgoin Jallieu, France
| | - Rossella Parini
- Rare Metabolic Disease Unit, Department of Pediatrics, Fondazione MBBM, San Gerardo Hospital, Monza, Italy
| | - Miriam Rigoldi
- Rare Metabolic Disease Unit, Department of Pediatrics, Fondazione MBBM, San Gerardo Hospital, Monza, Italy
| | - Francesca Furlan
- Rare Metabolic Disease Unit, Department of Pediatrics, Fondazione MBBM, San Gerardo Hospital, Monza, Italy
| | - Grazia Mancini
- Department of Clinical Genetics, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Dominique Bonnefont-Rousselot
- Unité pédagogique de Biochimie, Faculté des Sciences Pharmaceutiques et Biologiques, Paris, France; UPMC University Paris 6, UMR_S1166 Inserm ICAN, Paris, France; Service de Biochimie métabolique, Groupe hospitalier Pitié-Salpêtrière-Charles Foix, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
| | - Eric Bruckert
- Service d'Endocrinologie, Hôpital Pitié-Salpêtrière, AP-HP, Paris, France
| | - Jacques Schmitz
- Service de Gastroentérologie Pédiatrique, Hôpital Necker-Enfants Malades, AP-HP, Paris, France
| | - Jean Yves Scoazec
- Service d'anatomie pathologique, Hôpital Edouard Herriot, Hospices Civils, Lyon, France
| | - Sybil Charrière
- INSERM U1060, INSA de Lyon, INRA U1235, Univ Lyon-1, Université de Lyon, Villeurbanne, Oullins, France; Fédération d'Endocrinologie, Maladies métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Bron, France
| | - Sylvie Villar-Fimbel
- Fédération d'Endocrinologie, Maladies métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Bron, France
| | - Frederic Gottrand
- Department of Pediatric Gastroenterology Hepatology and Nutrition, Jeanne de Flandre university hospital, Lille, France
| | - Béatrice Dubern
- Nutrition et Gastroentérologie Pédiatriques, Hôpital Trousseau, AP-HP, Paris, France; Institut de Cardiométabolisme et Nutrition (ICAN), INSERM UMRS U872 (Eq7) Nutriomique, Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Diane Doummar
- Service de Neuropédiatrie, Hôpital Trousseau, Paris, France
| | - Francesca Joly
- Service de Gastroentérologie et d'Assistance Nutritive, Hôpital Beaujon, Clichy, France
| | | | - Alain Lachaux
- Service de Gastroentérologie Hépatologie et Nutrition Pédiatrique, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Bron, France; INSERM U 1111, Faculté de médecine Lyon Est, Université Lyon 1, Lyon, France
| | - Agnès Sassolas
- UF Dyslipidémies Cardiobiologie, Département de Biochimie et de Biologie Moléculaire du GHE, Laboratoire de Biologie Médicale Multi Sites, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INSA de Lyon, INRA U1235, Univ Lyon-1, Université de Lyon, Villeurbanne, Oullins, France
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Miller SA, Burnett JR, Leonis MA, McKnight CJ, van Bockxmeer FM, Hooper AJ. Novel missense MTTP gene mutations causing abetalipoproteinemia. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1842:1548-54. [PMID: 25108285 DOI: 10.1016/j.bbalip.2014.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 07/28/2014] [Accepted: 08/01/2014] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The microsomal triglyceride transfer protein (MTTP) plays a critical role in the formation of hepatic very low density lipoprotein. Abetalipoproteinemia (ABL) is a rare, naturally occurring extreme form of MTTP inhibition, which is characterized by the virtual absence of apolipoprotein (apo) B-containing lipoproteins in blood. The goal of this study was to examine the effect that four novel MTTP missense mutations had on protein interactions, expression and lipid-transfer activity, and to determine which mutations were responsible for the ABL phenotype observed in two patients. APPROACH AND RESULTS In two patients with ABL, we identified in MTTP a novel frameshift mutation (K35Ffs*37), and four novel missense mutations, namely, G264R, Y528H, R540C, and N649S. When transiently expressed in COS-7 cells, all missense MTTP mutations interacted with apoB17, apoB48, and protein disulfide isomerase. Mutations Y528H and R540C, however, displayed negligible levels of MTTP activity and N649S displayed a partial reduction relative to the wild-type MTTP. In contrast, G264R retained full lipid-transfer activity. CONCLUSIONS These studies indicate that missense mutations Y528H, R540C, and N649S appear to cause ABL by reducing MTTP activity rather than by reducing binding of MTTP with protein disulfide isomerase or apoB. The region of MTTP containing amino acids 528 and 540 constitutes a critical domain for its lipid-transfer activity.
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Affiliation(s)
- Sharon A Miller
- School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia.
| | - 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, Perth, Australia.
| | - Mike A Leonis
- Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children's Hospital Medical Center and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
| | - C James McKnight
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA.
| | - Frank M van Bockxmeer
- Department of Clinical Biochemistry, PathWest Laboratory Medicine WA, Royal Perth Hospital, Perth, Australia; School of Surgery, 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, Perth, Australia.
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Stefanutti C. Targeting MTP for the treatment of homozygous familial hypercholesterolemia. ACTA ACUST UNITED AC 2014. [DOI: 10.2217/clp.14.17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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21
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Molecular cloning, expression, and hormonal regulation of the chicken microsomal triglyceride transfer protein. Gene 2013; 523:1-9. [DOI: 10.1016/j.gene.2013.03.102] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 03/03/2013] [Accepted: 03/25/2013] [Indexed: 11/18/2022]
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22
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Najah M, Youssef SM, Yahia HM, Afef S, Awatef J, Saber H, Fadhel NM, Sassolas A, Naceur SM. Molecular characterization of Tunisian families with abetalipoproteinemia and identification of a novel mutation in MTTP gene. Diagn Pathol 2013; 8:54. [PMID: 23556456 PMCID: PMC3632489 DOI: 10.1186/1746-1596-8-54] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 01/10/2013] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Abetalipoproteinemia (ABL; OMIM 200100) is a rare monogenic disorder of lipid metabolism characterized by reduced plasma levels of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and almost complete absence of apolipoprotein B (apoB). ABL results from genetic deficiency in microsomal triglyceride transfer protein (MTP; OMIM 157147). In the present study we investigated two unrelated Tunisian patients, born from consanguineous marriages, with severe deficiency of plasma low-density lipoprotein (LDL) and apo B. METHODS Intestinal biopsies were performed and The MTTP gene was amplified by Polymerase chain reaction then directly sequenced in patients presenting chronic diarrhea and retarded growth. RESULTS First proband was homozygous for a novel nucleotide deletion (c. 2611delC) involving the exon 18 of MTTP gene predicted to cause a non functional protein of 898 amino acids (p.H871I fsX29). Second proband was homozygous for a nonsense mutation in exon 8 (c.923 G > A) predicted to cause a truncated protein of 307 amino acids (p.W308X), previously reported in ABL patients. CONCLUSIONS We discovered a novel mutation in MTTP gene and we confirmed the diagnosis of abetalipoproteinemia in new Tunisian families. VIRTUAL SLIDES The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8134027928652779.
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Khatun I, Walsh MT, Hussain MM. Loss of both phospholipid and triglyceride transfer activities of microsomal triglyceride transfer protein in abetalipoproteinemia. J Lipid Res 2013; 54:1541-1549. [PMID: 23475612 DOI: 10.1194/jlr.m031658] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in microsomal triglyceride transfer protein (MTP) cause abetalipoproteinemia (ABL), characterized by the absence of plasma apoB-containing lipoproteins. In this study, we characterized the effects of various MTP missense mutations found in ABL patients with respect to their expression, subcellular location, and interaction with protein disulfide isomerase (PDI). In addition, we characterized functional properties by analyzing phospholipid and triglyceride transfer activities and studied their ability to support apoB secretion. All the mutants colocalized with calnexin and interacted with PDI. We found that R540H and N780Y, known to be deficient in triglyceride transfer activity, also lacked phospholipid transfer activity. Novel mutants S590I and G746E did not transfer triglycerides and phospholipids and did not assist in apoB secretion. In contrast, D384A displayed both triglyceride and phospholipid transfer activities and supported apoB secretion. These studies point out that ABL is associated with the absence of both triglyceride and phospholipid transfer activities in MTP.
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Affiliation(s)
- Irani Khatun
- Molecular and Cellular Biology Program, SUNY Downstate Medical Center, Brooklyn, NY; School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - Meghan T Walsh
- Molecular and Cellular Biology Program, SUNY Downstate Medical Center, Brooklyn, NY; School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - M Mahmood Hussain
- School of Graduate Studies, Department of Cell Biology, and SUNY Downstate Medical Center, Brooklyn, NY; Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY.
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24
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Abstract
SIGNIFICANCE Protein disulfide isomerase (PDI) and its homologs have essential roles in the oxidative folding and chaperone-mediated quality control of proteins in the secretory pathway. In this review, the importance of PDI in health and disease will be examined, using examples from the fields of lipid homeostasis, hemostasis, infectious disease, cancer, neurodegeneration, and infertility. RECENT ADVANCES Recent structural studies, coupled with cell biological, biochemical, and clinical approaches, have demonstrated that PDI family proteins are involved in a wide range of physiological and disease processes. CRITICAL ISSUES Critical issues in the field include understanding how and why a PDI family member is involved in a given disease, and defining the physiological client specificity of the various PDI proteins when they are expressed in different tissues. FUTURE DIRECTIONS Future directions are likely to include the development of new and more specific reagents to study and manipulate PDI family function. The development of conditional mouse models in concert with clinical data will help us to understand the in vivo function of the different PDIs at the organism level. Taken together with advances in structural biology and biochemical studies, this should help us to further understand and modify PDIs' functional interactions.
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Affiliation(s)
- Adam M Benham
- School of Biological and Biomedical Sciences, Science Site, Durham University, Durham, England.
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25
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Di Filippo M, Créhalet H, Samson-Bouma ME, Bonnet V, Aggerbeck LP, Rabès JP, Gottrand F, Luc G, Bozon D, Sassolas A. Molecular and functional analysis of two new MTTP gene mutations in an atypical case of abetalipoproteinemia. J Lipid Res 2012; 53:548-555. [PMID: 22236406 PMCID: PMC3276478 DOI: 10.1194/jlr.m020024] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 01/10/2012] [Indexed: 02/05/2023] Open
Abstract
Abetalipoproteinemia (ABL) is an inherited disease characterized by the defective assembly and secretion of apolipoprotein B-containing lipoproteins caused by mutations in the microsomal triglyceride transfer protein large subunit (MTP) gene (MTTP). We report here a female patient with an unusual clinical and biochemical ABL phenotype. She presented with severe liver injury, low levels of LDL-cholesterol, and subnormal levels of vitamin E, but only mild fat malabsorption and no retinitis pigmentosa or acanthocytosis. Our objective was to search for MTTP mutations and to determine the relationship between the genotype and this particular phenotype. The subject exhibited compound heterozygosity for two novel MTTP mutations: one missense mutation (p.Leu435His) and an intronic deletion (c.619-5_619-2del). COS-1 cells expressing the missense mutant protein exhibited negligible levels of MTP activity. In contrast, the minigene splicing reporter assay showed an incomplete splicing defect of the intronic deletion, with 26% of the normal splicing being maintained in the transfected HeLa cells. The small amount of MTP activity resulting from the residual normal splicing in the patient explains the atypical phenotype observed. Our investigation provides an example of a functional analysis of unclassified variations, which is an absolute necessity for the molecular diagnosis of atypical ABL cases.
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Affiliation(s)
- Mathilde Di Filippo
- Hospices Civils de Lyon, Centre de Biologie et de Pathologie Est, Département de biochimie et biologie moléculaire, Bron F-69677, France; Université de Lyon, INSERM U1060, INSA de Lyon, INRA U1235, Université Lyon-1, Villeurbanne F-69621, Oullins F-69600, France.
| | - Hervé Créhalet
- Hospices Civils de Lyon, Centre de Biologie et de Pathologie Est, Département de biochimie et biologie moléculaire, Bron F-69677, France
| | | | - Véronique Bonnet
- Hospices Civils de Lyon, Centre de Biologie et de Pathologie Est, Département de biochimie et biologie moléculaire, Bron F-69677, France
| | | | - Jean-Pierre Rabès
- INSERM U698, Université Diderot, CHU X. Bichat Secteur C. Bernard, Paris 75877, France; Université Versailles Saint-Quentin-en-Yvelines, UFR de Médecine Paris Ile-de-France Ouest, Guyancourt 78280, France; AP-HP, GH Hôpitaux Universitaires Paris Ile-de-France Ouest, Hôpital Ambroise Paré, Service de Biochimie et Génétique Moléculaire, Boulogne 92104, France
| | - Frederic Gottrand
- CHRU Lille, Hôpital Jeanne de Flandre, Département de Pédiatrie, Université Lille Nord de France, Faculté de médecine, INSERM U995, IFR114, Lille 59000, France
| | - Gérald Luc
- Hôpital Universitaire de Lille, Service de Médecine Interne, Université Lille Nord de France, Lille 59000, France
| | - Dominique Bozon
- Hospices Civils de Lyon, Centre de Biologie et de Pathologie Est, Département de biochimie et biologie moléculaire, Bron F-69677, France
| | - Agnès Sassolas
- Hospices Civils de Lyon, Centre de Biologie et de Pathologie Est, Département de biochimie et biologie moléculaire, Bron F-69677, France; Université de Lyon, INSERM U1060, INSA de Lyon, INRA U1235, Université Lyon-1, Villeurbanne F-69621, Oullins F-69600, France
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26
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Hussain MM, Rava P, Walsh M, Rana M, Iqbal J. Multiple functions of microsomal triglyceride transfer protein. Nutr Metab (Lond) 2012; 9:14. [PMID: 22353470 PMCID: PMC3337244 DOI: 10.1186/1743-7075-9-14] [Citation(s) in RCA: 182] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 02/21/2012] [Indexed: 02/08/2023] Open
Abstract
Microsomal triglyceride transfer protein (MTP) was first identified as a major cellular protein capable of transferring neutral lipids between membrane vesicles. Its role as an essential chaperone for the biosynthesis of apolipoprotein B (apoB)-containing triglyceride-rich lipoproteins was established after the realization that abetalipoproteinemia patients carry mutations in the MTTP gene resulting in the loss of its lipid transfer activity. Now it is known that it also plays a role in the biosynthesis of CD1, glycolipid presenting molecules, as well as in the regulation of cholesterol ester biosynthesis. In this review, we will provide a historical perspective about the identification, purification and characterization of MTP, describe methods used to measure its lipid transfer activity, and discuss tissue expression and function. Finally, we will review the role MTP plays in the assembly of apoB-lipoprotein, the regulation of cholesterol ester synthesis, biosynthesis of CD1 proteins and propagation of hepatitis C virus. We will also provide a brief overview about the clinical potentials of MTP inhibition.
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Affiliation(s)
- M Mahmood Hussain
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Paul Rava
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Meghan Walsh
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Muhammad Rana
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Jahangir Iqbal
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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27
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Pons V, Rolland C, Nauze M, Danjoux M, Gaibelet G, Durandy A, Sassolas A, Lévy E, Tercé F, Collet X, Mas E. A severe form of abetalipoproteinemia caused by new splicing mutations of microsomal triglyceride transfer protein (MTTP). Hum Mutat 2011; 32:751-9. [DOI: 10.1002/humu.21494] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2010] [Accepted: 02/17/2011] [Indexed: 11/09/2022]
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28
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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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29
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Hooper AJ, van Bockxmeer FM, Burnett JR. Monogenic Hypocholesterolaemic Lipid Disorders and Apolipoprotein B Metabolism. Crit Rev Clin Lab Sci 2008; 42:515-45. [PMID: 16390683 DOI: 10.1080/10408360500295113] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The study of apolipoprotein (apo) B metabolism is central to our understanding of human lipoprotein metabolism. Moreover, the assembly and secretion of apoB-containing lipoproteins is a complex process. Increased plasma concentrations of apoB-containing lipoproteins are an important risk factor for the development of atherosclerotic coronary heart disease. In contrast, decreased levels of, but not the absence of, these apoB-containing lipoproteins is associated with resistance to atherosclerosis and potential long life. The study of inherited monogenic dyslipidaemias has been an effective means to elucidate key metabolic steps and biologically relevant mechanisms. Naturally occurring gene mutations in affected families have been useful in identifying important domains of apoB and microsomal triglyceride transfer protein (MTP) governing the metabolism of apoB-containing lipoproteins. Truncation-causing mutations in the APOB gene cause familial hypobetalipoproteinaemia, whereas mutations in MTP result in abetalipoproteinaemia; both rare conditions are characterised by marked hypocholesterolaemia. The purpose of this review is to examine the role of apoB in lipoprotein metabolism and to explore the key biochemical, clinical, metabolic and genetic features of the monogenic hypocholesterolaemic lipid disorders affecting apoB metabolism.
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Affiliation(s)
- Amanda J Hooper
- School of Surgery and Pathology, University of Western Australia, Crawley, Australia
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30
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HIV replication enhances production of free fatty acids, low density lipoproteins and many key proteins involved in lipid metabolism: a proteomics study. PLoS One 2008; 3:e3003. [PMID: 18714345 PMCID: PMC2500163 DOI: 10.1371/journal.pone.0003003] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Accepted: 07/22/2008] [Indexed: 12/30/2022] Open
Abstract
Background HIV-infected patients develop multiple metabolic abnormalities including insulin resistance, lipodystrophy and dyslipidemia. Although progression of these disorders has been associated with the use of various protease inhibitors and other antiretroviral drugs, HIV-infected individuals who have not received these treatments also develop lipid abnormalities albeit to a lesser extent. How HIV alters lipid metabolism in an infected cell and what molecular changes are affected through protein interaction pathways are not well-understood. Results Since many genetic, epigenetic, dietary and other factors influence lipid metabolism in vivo, we have chosen to study genome-wide changes in the proteomes of a human T-cell line before and after HIV infection in order to circumvent computational problems associated with multiple variables. Four separate experiments were conducted including one that compared 14 different time points over a period of >3 months. By subtractive analyses of protein profiles overtime, several hundred differentially expressed proteins were identified in HIV-infected cells by mass spectrometry and each protein was scrutinized for its biological functions by using various bioinformatics programs. Herein, we report 18 HIV-modulated proteins and their interaction pathways that enhance fatty acid synthesis, increase low density lipoproteins (triglycerides), dysregulate lipid transport, oxidize lipids, and alter cellular lipid metabolism. Conclusions We conclude that HIV replication alone (i.e. without any influence of antiviral drugs, or other human genetic factors), can induce novel cellular enzymes and proteins that are significantly associated with biologically relevant processes involved in lipid synthesis, transport and metabolism (p = <0.0002–0.01). Translational and clinical studies on the newly discovered proteins may now shed light on how some of these proteins may be useful for early diagnosis of individuals who might be at high risk for developing lipid-related disorders. The target proteins could then be used for future studies in the development of inhibitors for preventing lipid-metabolic anomalies. This is the first direct evidence that HIV-modulates production of proteins that are significantly involved in disrupting the normal lipid-metabolic pathways.
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31
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Zamel R, Khan R, Pollex RL, Hegele RA. Abetalipoproteinemia: two case reports and literature review. Orphanet J Rare Dis 2008; 3:19. [PMID: 18611256 PMCID: PMC2467409 DOI: 10.1186/1750-1172-3-19] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Accepted: 07/08/2008] [Indexed: 01/23/2023] Open
Abstract
Abetalipoproteinemia (ABL, OMIM 200100) is a rare, autosomal recessive disorder, characterized by fat malabsorption, acanthocytosis and hypocholesterolemia in infancy. Later in life, deficiency of fat-soluble vitamins is associated with development of atypical retinitis pigmentosa, coagulopathy, posterior column neuropathy and myopathy. ABL results from mutations in the gene encoding the large subunit of microsomal triglyceride transfer protein (MTP; OMIM 157147). To date at least 33 MTP mutations have been identified in 43 ABL patients. We describe the clinical progress of two patients, both currently in the fifth decade of life, who were diagnosed with ABL as children and were treated with high oral doses of fat soluble vitamins, including vitamin E over the last three decades. Treatment appears to have been associated with arrest of the neuropathy and other complications in both patients. Because pharmacologic inhibition of MTP is being developed as a novel approach to reduce plasma cholesterol for prevention of cardiovascular disease, defining the long-term clinical features of patients with a natural deficiency in MTP might provide some insight into the possible effects of such treatments. We review the range of clinical, biochemical and molecular perturbations in ABL.
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Affiliation(s)
- Rola Zamel
- Department of Medicine and Biochemistry, University of Western Ontario, London, Ontario, Canada.
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32
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Banaszak LJ, Ranatunga WK. The assembly of apoB-containing lipoproteins: a structural biology point of view. Ann Med 2008; 40:253-67. [PMID: 18428019 DOI: 10.1080/07853890701813070] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Atherosclerosis is a widespread disease caused by the deposition of lipids on arterial walls. Such lipid plaques in coronary arteries can be fatal. Although many factors related to diet, life-style, etc. contribute to the worsening of the ailment, the primary cause, the lipids in the circulatory system, come from a series of low-density lipoproteins. These lipoproteins are necessary for the transport of lipids to and from different organs. It would be valuable to medicine and the field of drug design if a more detailed understanding of the organization of lipid and protein in these molecules were available. Unfortunately because of heterogeneity in their size and lipid composition, all classes of the low-density serum lipoproteins appear to be not amenable to the most widely used method for obtaining detailed atomic data - X-ray crystallography. However there appears to be a recently identified homolog that is relatively homogeneous, and crystal structures have been obtained. Used as a molecular model, the homolog serves as a source of conformational information that might help to unravel the processes involved in the lipid loading of the low-density lipoproteins. The review attempts to give a brief summary of the structural biology of the serum low-density lipoproteins relative to the molecular model of lipovitellin.
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Affiliation(s)
- Leonard J Banaszak
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA.
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33
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Guilmeau S, Niot I, Laigneau JP, Devaud H, Petit V, Brousse N, Bouvier R, Ferkdadji L, Besmond C, Aggerbeck LP, Bado A, Samson-Bouma ME. Decreased expression of Intestinal I- and L-FABP levels in rare human genetic lipid malabsorption syndromes. Histochem Cell Biol 2007; 128:115-23. [PMID: 17605029 DOI: 10.1007/s00418-007-0302-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2007] [Indexed: 11/26/2022]
Abstract
We investigated, for the first time, the expression of I- and L-FABP in two very rare hereditary lipid malabsorption syndromes as compared with normal subjects. Abetalipoproteinemia (ABL) and Anderson's disease (AD) are characterized by an inability to export alimentary lipids as chylomicrons that result in fat loading of enterocytes. Duodeno-jejunal biopsies were obtained from 14 fasted normal subjects, and from four patients with ABL and from six with AD. Intestinal FABP expression was investigated by immuno-histochemistry, western blot, ELISA and Northern blot analysis. In contrast to normal subjects, the cellular immunostaining for both FABPs was clearly decreased in patients, as the enterocytes became fat-laden. In patients with ABL, the intestinal contents of I- (60.7 +/- 13.38 ng/mg protein) and L-FABP (750.3 +/- 121.3 ng/mg protein) are significantly reduced (50 and 35%, P < 0.05, respectively) as compared to normal subjects (I-135.3 +/- 11.1 ng, L-1211 +/- 110 ng/mg protein). In AD, the patients also exhibited decreased expression (50%, P < 0.05; I-59 +/- 11.88 ng, L-618.2 +/- 104.6 ng/mg protein). Decreased FABP expression was not associated with decreased mRNA levels. The results suggest that enterocytes might regulate intracellular FABP content in response to intracellular fatty acids, which we speculate may act as lipid sensors to prevent their intracellular transport.
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Affiliation(s)
- S Guilmeau
- Institut National de la Santé et de la Recherche Médicale (INSERM), U773, Centre de Recherche Bichat Beaujon CRB3, Université Paris 7 Denis Diderot, site Bichat, BP 416, 75018, Paris, France
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Benayoun L, Granot E, Rizel L, Allon-Shalev S, Behar DM, Ben-Yosef T. Abetalipoproteinemia in Israel: evidence for a founder mutation in the Ashkenazi Jewish population and a contiguous gene deletion in an Arab patient. Mol Genet Metab 2007; 90:453-7. [PMID: 17275380 DOI: 10.1016/j.ymgme.2006.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Revised: 12/26/2006] [Accepted: 12/26/2006] [Indexed: 11/26/2022]
Abstract
Abetalipoproteinemia (ABL) is a rare autosomal recessive metabolic disorder, characterized by the absence of plasma apolipoprotein B-containing lipoproteins and very low levels of plasma triglycerides and cholesterol. ABL is caused by mutations of the MTP gene. We investigated the genetic basis for ABL in a cohort of Israeli families. In Ashkenazi Jewish patients we identified a conserved haplotype and a common MTP mutation, p.G865X, with a carrier frequency of 1:131 in this population. We also report the first case of ABL and additional abnormalities in a Muslim Arab patient, due to a homozygous contiguous gene deletion of approximately 481 kb, including MTP and eight other genes.
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Affiliation(s)
- Liat Benayoun
- Department of Genetics and The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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35
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The assembly of triacylglycerol-rich lipoproteins: an essential role for the microsomal triacylglycerol transfer protein. Br J Nutr 2007. [DOI: 10.1017/s0007114598001263] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Raised plasma triacylglycerol is an independent risk factor for cardiovascular disease, and an understanding of factors which regulate the synthesis and degradation of lipoproteins which carry triacylglycerol in the blood may lead to novel approaches to the treatment of hypertriacylglycerolaemia. An active microsomal triacylglycerol transfer protein (MTP) is essential for the assembly of particles which transport triacylglycerol through the circulation. After absorption in the intestine, dietary fat and fat-soluble vitamins are incorporated into chylomicrons in the intestinal epithelial cells, and these lipoproteins reach the bloodstream via the lymphatic system. Patients with the rare genetic disorder, abetalipoproteinaemia, in which MTP activity is absent, present clinically with fat-soluble vitamin and essential fatty acid deficiency, indicating a key role for MTP in the movement of fat into the body. The triacylglycerol-rich lipoprotein found in fasting blood, VLDL, is assembled in the liver by an MTP-dependent process similar to chylomicron assembly, and transports triacylglycerol to extra-hepatic tissues such as adipose tissue and heart. In the absence of MTP activity, VLDL are not synthesized and only extremely low levels of triacylglycerol are present in the blood. Dietary components, including fat, cholesterol and ethanol, can modify the expression of the MTP gene and, hence, MTP activity. The present review summarizes current knowledge of the role of MTP in the assembly and secretion of triacylglycerol-rich lipoproteins, and the regulation of its activity in both animal and cell systems.
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36
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Rava P, Ojakian GK, Shelness GS, Hussain MM. Phospholipid Transfer Activity of Microsomal Triacylglycerol Transfer Protein Is Sufficient for the Assembly and Secretion of Apolipoprotein B Lipoproteins. J Biol Chem 2006; 281:11019-27. [PMID: 16478722 DOI: 10.1074/jbc.m512823200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human microsomal triacylglycerol transfer protein (hMTP) is essential for apolipoprotein B (apoB)-lipoprotein assembly and secretion and is known to transfer triacylglycerols, cholesterol esters, and phospholipids. To understand the relative importance of each lipid transfer activity, we compared the ability of hMTP and its Drosophila ortholog (dMTP) to assemble apoB lipoproteins and to transfer various lipids. apoB48 secretion was induced when co-expressed with either hMTP or dMTP in COS cells, and oleic acid supplementation further augmented secretion without altering particle density. C-terminal epitope-tagged dMTP (dMTP-FLAG) facilitated the secretion of apoB polypeptides in the range of apoB48 to apoB72 but was approximately 50% as efficient as hMTP-FLAG. Comparison of lipid transfer activities revealed that although phospholipid transfer was similar in both orthologs, dMTP was unable to transfer neutral lipids. We conclude that the phospholipid transfer activity of MTP is sufficient for the assembly and secretion of primordial apoB lipoproteins and may represent its earliest function evolved for the mobilization of lipid in invertebrates. Identification of MTP inhibitors, which selectively affect transfer of a specific lipid class, may have therapeutic potential.
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Affiliation(s)
- Paul Rava
- Department of Anatomy and Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
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37
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Marza E, Barthe C, André M, Villeneuve L, Hélou C, Babin PJ. Developmental expression and nutritional regulation of a zebrafish gene homologous to mammalian microsomal triglyceride transfer protein large subunit. Dev Dyn 2005; 232:506-18. [PMID: 15614773 DOI: 10.1002/dvdy.20251] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The microsomal triglyceride transfer protein (MTP) large subunit is required for the assembly and secretion of apolipoprotein B-containing lipoproteins. We have found a zebrafish mtp homologous gene coding a protein with 54% identity with human MTP large subunit with the most conserved regions distributed in the corresponding predicted alpha-helical and C- and A-sheet domains. In situ hybridizations showed that zebrafish mtp transcripts were distributed in the yolk syncytial layer during early embryogenesis and in anterior intestine and liver from 48 hr postfertilization onward. Real-time quantitative RT-PCR confirmed the developmental regulation and tissue-specificity of mtp expression. A significant pretranslational up-regulation of mtp expression was observed in the anterior intestine after feeding. The nutritional regulation of zebrafish mtp expression observed in the anterior intestine supports the notion that this protein, similar to mammalian MTP large subunit, could be a factor implicated directly or indirectly in large lipid droplets accumulation observed in the fish enterocyte after feeding.
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Affiliation(s)
- Esther Marza
- Laboratoire Génomique et Physiologie des Poissons, UMR 1067 NUAGE INRA-IFREMER, Université Bordeaux 1, 33405 Talence Cedex, France
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Di Leo E, Lancellotti S, Penacchioni JY, Cefalù AB, Averna M, Pisciotta L, Bertolini S, Calandra S, Gabelli C, Tarugi P. Mutations in MTP gene in abeta- and hypobeta-lipoproteinemia. Atherosclerosis 2005; 180:311-8. [PMID: 15910857 DOI: 10.1016/j.atherosclerosis.2004.12.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2004] [Revised: 12/07/2004] [Accepted: 12/15/2004] [Indexed: 10/25/2022]
Abstract
Familial hypobetalipoproteinemia (FHBL) and abetalipoproteinemia (ABL) are inherited disorders of apolipoprotein B (apo B)-containing lipoproteins that result from mutations in apo B and microsomal triglyceride transfer protein (MTP) genes, respectively. Here we report three patients with severe deficiency of plasma low-density lipoprotein (LDL) and apo B. Two of them (probands F.A. and P.E.) had clinical and biochemical phenotype consistent with ABL. Proband F.A. was homozygous for a minute deletion/insertion (c.1228delCCCinsT) in exon 9 of MTP gene predicted to cause a truncated MTP protein of 412 amino acids. Proband P. E. was heterozygous for a mutation in intron 9 (IVS9-1G>A), previously reported in an ABL patient. We failed to find the second pathogenic mutation in MTP gene of this patient. No mutations were found in apo B gene. The third proband (D.F.) had a less severe lipoprotein phenotype which was similar to that of heterozygous FHBL and appeared to be inherited as a co-dominant trait. However, he had no mutations in apo B gene. He was found to be a compound heterozygote for two missense mutations (D384A and G661A), involving highly conserved regions of MTP. Since this proband was also homozygous for varepsilon2 allele of apolipoprotein E (apo E), it is likely that his hypobetalipoproteinemia derives from a combined effect of a mild MTP deficiency and homozygosity for apo E2 isoform.
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Affiliation(s)
- Enza Di Leo
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, I-41100 Modena, Italy
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Slight I, Bendayan M, Malo C, Delvin E, Lambert M, Levy E. Identification of microsomal triglyceride transfer protein in intestinal brush-border membrane. Exp Cell Res 2004; 300:11-22. [PMID: 15383310 DOI: 10.1016/j.yexcr.2004.05.038] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 05/26/2004] [Indexed: 12/01/2022]
Abstract
Microsomal triglyceride transfer protein (MTP) is a heterodimeric complex consisting of a unique large 97-kDa protein and the multifunctional 58-kDa protein disulfide isomerase (PDI). It plays an essential role in the assembly of lipoproteins by shuttling lipids between phospholipid membranes. Based on cell fractionation, early studies have suggested the endoplasmic reticulum (ER) as the exclusive site of MTP. Focusing on the plasma membrane in this study, our attempts with immunoelectron microscopy and specific antibodies surprisingly revealed that labeling was not exclusively confined to the microsomes of rat absorptive cells. Immunogold labeling was also detected over the microvillus membrane of enterocytes. Western blot analysis and biochemical activity measurement confirmed MTP protein expression in brush-border membrane vesicles (BBMV) isolated from the intestinal epithelial cells of various species. Furthermore, MTP was coexpressed in microvilli membrane with PDI that is crucial to maintain the structure and activity of the MTP complex. The treatment of Caco-2 cells with nocodazole and colchicine blocked the appearance of MTP in the apical membrane. Similarly, the addition of BMS-197636, a known inhibitor of MTP transfer activity, suppressed the latter. In conclusion, the present studies suggest that MTP is present in the brush-border membrane of the enterocyte. Understanding the possible physiological role of MTP in this location may reveal additional functions.
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Affiliation(s)
- Isabelle Slight
- Department of Nutrition, Université de Montréal, Montréal, Québec, Canada H3T 1C5
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40
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Berthier MT, Houde A, Paradis AM, Couture P, Gaudet D, Després JP, Vohl MC. Molecular screening of the microsomal triglyceride transfer protein: association between polymorphisms and both abdominal obesity and plasma apolipoprotein B concentration. J Hum Genet 2004; 49:684-690. [PMID: 15635487 DOI: 10.1007/s10038-004-0207-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Accepted: 09/22/2004] [Indexed: 11/29/2022]
Abstract
Microsomal triglyceride transfer protein (MTP) plays a critical role in the assembly of lipoproteins. The aim of this study was first to seek new MTP gene variants and then to verify whether MTP gene polymorphisms were associated with plasma lipoprotein/lipid levels in men with visceral obesity. Molecular screening of the MTP gene revealed 11 polymorphisms. The carriers of the c.933A allele and c.1151C allele or -400A/A homozygotes were characterized by increased levels of abdominal visceral adipose tissue (AT) measured by computed tomography (P=0.02, P=0.04, P=0.03, respectively). After dividing each genotype group into subgroups using 130 cm(2) as a cutoff point for visceral AT, significantly higher low-density lipoprotein (LDL)-apolipoprotein B (apoB) concentrations were found in obese men bearing the c.891G allele, the -400 T allele, as well as for 282G/G homozygotes, 933C/C homozygotes, and 1151A/A homozygotes when compared to their lean counterparts. Haplotypes were not associated with phenotypes under study. In conclusion, some MTP gene polymorphisms in the French Canadian population are associated with the amount of abdominal visceral AT and plasma LDL-apoB concentrations.
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Affiliation(s)
- Marie-Thérèse Berthier
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada
- Department of Food Science and Nutrition, Laval University, Sainte-Foy, QC, Canada
| | - Alain Houde
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada
| | - Ann-Marie Paradis
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada
- Department of Food Science and Nutrition, Laval University, Sainte-Foy, QC, Canada
| | - Patrick Couture
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada
| | - Daniel Gaudet
- Montreal University Community Genomic Medicine Center and Chicoutimi Hospital Lipid Clinic, Chicoutimi Hospital, QC, Canada
| | - Jean-Pierre Després
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada
- Quebec Heart Institute, QC, Canada
| | - Marie-Claude Vohl
- Lipid Research Center, TR93, CHUQ Pavilion CHUL, 2705 Laurier Blvd, TR93, Sainte-Foy, QC, G1V 4G2, Canada.
- Department of Food Science and Nutrition, Laval University, Sainte-Foy, QC, Canada.
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Berthier MT, Couture P, Houde A, Paradis AM, Sammak A, Verner A, Deprés JP, Gagné C, Gaudet D, Vohl MC. The c.419-420insA in the MTP gene is associated with abetalipoproteinemia among French-Canadians. Mol Genet Metab 2004; 81:140-3. [PMID: 14741197 DOI: 10.1016/j.ymgme.2003.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Abetalipoproteinemia (ABL) is a rare autosomal recessive disease characterised by the absence of apolipoprotein B (apoB) containing lipoproteins and, in consequence, very low triglyceride and cholesterol levels. Microsomal triglyceride transfer protein (MTP) has been associated with ABL. A search for sequence variants in the large subunit of MTP in a kindred of 10 individuals from Saguenay-Lac-St Jean area with a propositus exhibiting ABL as well as in four independent patients from the greater Quebec city area and exhibiting very low apoB and LDL-cholesterol levels identified 12 variations. Only one sequence variation, the c.419-420insA, was observed, in the homozygous form, in the abetalipoproteinemic patient. The -493G/-400A/-164T/282G/383T/419-420insA/453T/891C/969T/1151A/2884G haplotype carries the insertion and was found in all members of the family studied. In conclusion, the present study showed that the c.419-420insA alone, in the homozygous form, is a cause of classical recessive inherited ABL in the French-Canadian population.
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Lancellotti S, Di Leo E, Penacchioni JY, Balli F, Viola L, Bertolini S, Calandra S, Tarugi P. Hypobetalipoproteinemia with an apparently recessive inheritance due to a “de novo” mutation of apolipoprotein B. Biochim Biophys Acta Mol Basis Dis 2004; 1688:61-7. [PMID: 14732481 DOI: 10.1016/j.bbadis.2003.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Familial hypobetalipoproteinemia (FHBL) is a co-dominant disorder either linked or not linked to apolipoprotein (apo) B gene. Abetalipoproteinemia (ABL) is a recessive disorder due to mutations of microsomal triglyceride transfer protein (MTP) gene. We investigated a patient with apparently recessive hypobetalipoproteinemia consistent with symptomatic heterozygous FHBL or a "mild" form of ABL. The proband had fatty liver associated with LDL-cholesterol (LDL-C) and apo B levels <5th percentile but no truncated apo B forms detectable in plasma. MTP gene sequence revealed that he was a carrier of the I128T polymorphism and an unreported amino acid substitution (V168I) unlikely to be the cause of hypobetalipoproteinemia. Apo B gene sequence showed that he was heterozygous for two single base substitutions in exon 9 and 22 resulting in a nonsense (Q294X) and a missense (R1101H) mutation, respectively. Neither of his parents carried the Q294X; his father and paternal grandmother carried the R1101H mutation. Analysis of polymorphic genetic markers excluded non-paternity. In conclusion, the proband has a "de novo" mutation of apo B gene resulting in a short truncated apo B form (apo B-6.46). Sporadic cases of FHBL with an apparently recessive transmission may be caused by "de novo" mutations of apo B gene.
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Affiliation(s)
- Sandra Lancellotti
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, I-41100 Modena, Italy
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43
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Koishi R, Ando Y, Ono M, Shimamura M, Yasumo H, Fujiwara T, Horikoshi H, Furukawa H. Angptl3 regulates lipid metabolism in mice. Nat Genet 2002; 30:151-7. [PMID: 11788823 DOI: 10.1038/ng814] [Citation(s) in RCA: 320] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The KK obese mouse is moderately obese and has abnormally high levels of plasma insulin (hyperinsulinemia), glucose (hyperglycemia) and lipids (hyperlipidemia). In one strain (KK/San), we observed abnormally low plasma lipid levels (hypolipidemia). This mutant phenotype is inherited recessively as a mendelian trait. Here we report the mapping of the hypolipidemia (hypl) locus to the middle of chromosome 4 and positional cloning of the autosomal recessive mutation responsible for the hypolipidemia. The hypl locus encodes a unique angiopoietin-like lipoprotein modulator, which we named Allm1. It is identical to angiopoietin-like protein 3, encoded by Angptl3, and has a highly conserved counterpart in humans. Overexpression of Angptl3 or intravenous injection of the purified protein in KK/San mice elicited an increase in circulating plasma lipid levels. This increase was also observed in C57BL/6J normal mice. Taken together, these data suggest that Angptl3 regulates lipid metabolism in animals.
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Affiliation(s)
- Ryuta Koishi
- Biomedical Research Laboratories, Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
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44
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Berriot-Varoqueaux N, Dannoura AH, Moreau A, Verthier N, Sassolas A, Cadiot G, Lachaux A, Munck A, Schmitz J, Aggerbeck LP, Samson-Bouma ME. Apolipoprotein B48 glycosylation in abetalipoproteinemia and Anderson's disease. Gastroenterology 2001; 121:1101-8. [PMID: 11677202 DOI: 10.1053/gast.2001.29331] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS Abetalipoproteinemia and Anderson's disease are hereditary lipid malabsorption syndromes. In abetalipoproteinemia, lipoprotein assembly is defective because of mutations in the microsomal triglyceride transfer protein. Here, we evaluated the intracellular transport of apolipoprotein B48 to localize the defect in Anderson's disease. METHODS Asparagine-linked oligosaccharide processing of apolipoprotein B48 in normal and affected individuals was determined by the endoglycosidase H and F sensitivities of the protein after metabolic labeling of intestinal explants in organ culture. Cell ultrastructure was evaluated with electron microscopy. RESULTS In Anderson's disease as in normal individuals, there was a time-dependent transformation of high mannose endoglycosidase H-sensitive oligosaccharides, of endoplasmic reticulum origin, to complex endoglycosidase H-resistant oligosaccharides, added in the Golgi network. In contrast, despite the translocation of apolipoprotein B48 into the endoplasmic reticulum in patients with abetalipoproteinemia and in biopsies treated with Brefeldin A, which blocks anterograde transport between the endoplasmic reticulum and the Golgi network, there was no transformation of endoglycosidase H-sensitive oligosaccharides. CONCLUSIONS In abetalipoproteinemia and Anderson's disease, apolipoprotein B48 is completely translocated into the endoplasmic reticulum, but only in Anderson's disease is the protein transported to the Golgi apparatus. This suggests that Anderson's disease is caused by a post-Golgi cargo-specific secretion defect.
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45
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Berriot-Varoqueaux N, Aggerbeck LP, Samson-Bouma M, Wetterau JR. The role of the microsomal triglygeride transfer protein in abetalipoproteinemia. Annu Rev Nutr 2001; 20:663-97. [PMID: 10940349 DOI: 10.1146/annurev.nutr.20.1.663] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The microsomal triglyceride transfer protein (MTP) is a dimeric lipid transfer protein consisting of protein disulfide isomerase and a unique 97-kDa subunit. In vitro, MTP accelerates the transport of triglyceride, cholesteryl ester, and phospholipid between membranes. It was recently demonstrated that abetalipoproteinemia, a hereditary disease characterized as an inability to produce chylomicrons and very low-density lipoproteins in the intestine and liver, respectively, results from mutations in the gene encoding the 97-kDa subunit of the microsomal triglyceride transfer protein. Downstream effects resulting from this defect include malnutrition, very low plasma cholesterol and triglyceride levels, altered lipid and protein compositions of membranes and lipoprotein particles, and vitamin deficiencies. Unless treated, abetalipoproteinemic subjects develop gastrointestinal, neurological, ophthalmological, and hematological abnormalities.
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Affiliation(s)
- N Berriot-Varoqueaux
- U327 Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine Xavier Bichat, Université de Paris 7-Denis Diderot, 75870 Paris, France.
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46
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Novel mutations in the microsomal triglyceride transfer protein gene causing abetalipoproteinemia. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)33426-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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47
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Gordon DA, Jamil H. Progress towards understanding the role of microsomal triglyceride transfer protein in apolipoprotein-B lipoprotein assembly. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1486:72-83. [PMID: 10856714 DOI: 10.1016/s1388-1981(00)00049-4] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The microsomal triglyceride transfer protein (MTP) is necessary for the proper assembly of the apolipoprotein B containing lipoproteins, very low density lipoprotein and chylomicrons. Recent research has significantly advanced our understanding of the role of MTP in these pathways at the molecular and cellular level. Biochemical studies suggest that initiation of lipidation of the nascent apolipoprotein B polypeptide may occur through a direct association with MTP. This early lipidation may be required to allow the nascent polypeptide to fold properly and therefore avoid ubiquitination and degradation. Concerning the addition of core neutral lipids in the later stages of lipoprotein assembly, cell culture studies show that MTP lipid transfer activity is not required for this to occur for apolipoprotein B-100 containing lipoproteins. Likewise, MTP does not appear to directly mediate addition of core neutral lipid to nascent apoB-48 particles. However, new data indicate that MTP is required to produce triglyceride rich droplets in the smooth endoplasmic reticulum which may supply the core lipids for conversion of nascent, dense apoB-48 particles to mature VLDL. In addition, assembly of dense apolipoprotein B-48 containing lipoproteins has been observed in mouse liver in the absence of MTP. As a result of these new data, an updated model for the role of MTP in lipoprotein assembly is proposed.
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Affiliation(s)
- D A Gordon
- Division of Metabolic and Cardiovascular Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543, USA.
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48
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Burch WL, Herscovitz H. Disulfide bonds are required for folding and secretion of apolipoprotein B regardless of its lipidation state. J Biol Chem 2000; 275:16267-74. [PMID: 10747912 DOI: 10.1074/jbc.m000446200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein (apo) B-100, an essential protein for the assembly and secretion of very low density lipoproteins depends on lipid binding (lipidation) for its secretion. Seven of its 8 disulfides are clustered within the N-terminal 21%. The role of these disulfides in the secretion of lipidated or unlipidated truncated forms of apoB was studied in C127 cells expressing apoB-17, apoB-29, or apoB-41. These cells do not express microsomal triglyceride transfer protein yet secrete apoB-41 on triacylglycerol-rich lipoproteins while apoB-29 and apoB-17 are secreted with little or no lipid, respectively. Dithiothreitol utilized in pulse-chase studies prevented the cotranslational formation of disulfides and when added posttranslationally reduced native disulfides. As a result, the secretion of reduced apoB forms was blocked and they were retained in the cells. Reduced apoB polypeptides were rescued following removal of dithiothreitol, as they underwent post-translational disulfide bonding, attained their mature form, and were subsequently secreted. Together the data suggest that in C127 cells the formation of native disulfides is critical for the folding and secretion of apoB independent of its length, its requirement for lipidation or microsomal triglyceride transfer protein expression. Therefore, these cells provide an appropriate model to study the folding of apoB in great detail.
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Affiliation(s)
- W L Burch
- Department of Biophysics, Center for Advanced Biomedical Research, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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49
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Couture P, Otvos JD, Cupples LA, Wilson PW, Schaefer EJ, Ordovas JM. Absence of association between genetic variation in the promoter of the microsomal triglyceride transfer protein gene and plasma lipoproteins in the Framingham Offspring Study. Atherosclerosis 2000; 148:337-43. [PMID: 10657570 DOI: 10.1016/s0021-9150(99)00281-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Microsomal triglyceride transfer protein (MTP) is a lipid transfer protein that is required for the assembly and secretion of very low density lipoproteins (VLDL) by the liver and chylomicrons by the intestine. The common G-493T polymorphism of the MTP promoter has been shown to be associated with decreased plasma LDL-cholesterol and ApoB content of VLDL. The purpose of the present study was, therefore, to investigate the association of this mutation with variations in lipid and apoprotein levels, lipoprotein subclass profiles and coronary heart disease (CHD) risk in a population-based sample of 1226 male and 1284 female Framingham Offspring participants. In men and women, no significant association was found between the G-493T MTP polymorphism and variations of plasma levels of total cholesterol, LDL-cholesterol, apoprotein B, HDL-cholesterol, apoprotein AI and triglycerides. In order to further investigate potential relationships with variations of lipoprotein phenotypes, lipoprotein subclass profiles were measured using automated nuclear magnetic resonance (NMR) spectroscopy. Each NMR profile yielded information on lipid mass of VLDL, LDL, and HDL subclasses. In both genders, there was no significant association between the G-493T polymorphism and variability of lipoprotein subclass distributions or lipoprotein particle size. Furthermore, no significant association was found between the polymorphism of the MTP promoter and prevalence or the age of onset of CHD. Thus, our results suggest that the G-493T mutation in the MTP promoter is unlikely to have significant implications for cardiovascular disease in men and women.
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Affiliation(s)
- P Couture
- Lipid Metabolism Laboratory, Jean Mayer-USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA
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50
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Wu J, Zhu YH, Patel SB. Cyclosporin-induced dyslipoproteinemia is associated with selective activation of SREBP-2. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E1087-94. [PMID: 10600799 DOI: 10.1152/ajpendo.1999.277.6.e1087] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of cyclosporin A has contributed greatly to the success of organ transplantation. However, cyclosporin-associated side effects of hypertension, nephrotoxicity, and dyslipoproteinemia have tempered these benefits. Cyclosporin-induced dyslipoproteinemia may be an important risk factor for the accelerated atherosclerosis observed posttransplantation. Using a mouse model, we treated Swiss-Webster mice for 6 days with a daily dose of 20 microg/g body wt of cyclosporin and observed significant elevations of plasma cholesterol, triglyceride, and apolipoprotein B (apoB) levels relative to vehicle-alone treated control animals. Measurement of the rate of secretion of very low-density lipoprotein (VLDL) by the liver in vivo showed that cyclosporin treatment led to a significant increase in the rate of hepatic VLDL triglyceride secretion. Total apoB secretion was unaffected. Northern analysis showed that cyclosporin A treatment increased the abundance of hepatic mRNA levels for a number of key genes involved in cholesterol biosynthesis relative to vehicle-alone treated animals. Two key transcriptional factors, sterol regulatory element-binding protein (SREBP)-1 and SREBP-2, also showed differential expression; SREBP-2 expression was increased at the mRNA level, and there was an increase in the active nuclear form, whereas the mRNA and the nuclear form of SREBP-1 were reduced. These results show that the molecular mechanisms by which cyclosporin causes dyslipoproteinemia may, in part, be mediated by selective activation of SREBP-2, leading to enhanced expression of lipid metabolism genes and hepatic secretion of VLDL triglyceride.
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Affiliation(s)
- J Wu
- Division of Endocrinology, Diabetes, and Medical Genetics, Medical University of South Carolina, Charleston, South Carolina 29425-2222, USA
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