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Thierer JH, Foresti O, Yadav PK, Wilson MH, Moll TOC, Shen MC, Busch-Nentwich EM, Morash M, Mohlke KL, Rawls JF, Malhotra V, Hussain MM, Farber SA. Pla2g12b drives expansion of triglyceride-rich lipoproteins. Nat Commun 2024; 15:2095. [PMID: 38453914 PMCID: PMC10920679 DOI: 10.1038/s41467-024-46102-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 02/14/2024] [Indexed: 03/09/2024] Open
Abstract
Vertebrates transport hydrophobic triglycerides through the circulatory system by packaging them within amphipathic particles called Triglyceride-Rich Lipoproteins. Yet, it remains largely unknown how triglycerides are loaded onto these particles. Mutations in Phospholipase A2 group 12B (PLA2G12B) are known to disrupt lipoprotein homeostasis, but its mechanistic role in this process remains unclear. Here we report that PLA2G12B channels lipids within the lumen of the endoplasmic reticulum into nascent lipoproteins. This activity promotes efficient lipid secretion while preventing excess accumulation of intracellular lipids. We characterize the functional domains, subcellular localization, and interacting partners of PLA2G12B, demonstrating that PLA2G12B is calcium-dependent and tightly associated with the membrane of the endoplasmic reticulum. We also detect profound resistance to atherosclerosis in PLA2G12B mutant mice, suggesting an evolutionary tradeoff between triglyceride transport and cardiovascular disease risk. Here we identify PLA2G12B as a key driver of triglyceride incorporation into vertebrate lipoproteins.
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Affiliation(s)
- James H Thierer
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Ombretta Foresti
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Barcelona, 08003, ES, Spain
| | - Pradeep Kumar Yadav
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, 11501, USA
- Department of Botany, Faculty of Science, University of Allahabad, Prayagraj, India
| | - Meredith H Wilson
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Tabea O C Moll
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA
| | - Meng-Chieh Shen
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA
| | | | - Margaret Morash
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, 27708, USA
| | - Karen L Mohlke
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - John F Rawls
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, 27708, USA
| | - Vivek Malhotra
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Barcelona, 08003, ES, Spain
- Universitat Pompeu Fabra, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, 11501, USA
| | - Steven A Farber
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, 21218, USA.
- Johns Hopkins University in Baltimore, Maryland Department of biology, Baltimore, MD, 21218, USA.
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2
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Anaganti N, Valmiki S, Recacha R, Islam S, Farber S, Ruddock L, Hussain MM. Bulky hydrophobic side chains in the β1-sandwich of microsomal triglyceride transfer protein are critical for the transfer of both triglycerides and phospholipids. J Biol Chem 2024; 300:105726. [PMID: 38325741 PMCID: PMC10907164 DOI: 10.1016/j.jbc.2024.105726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/19/2024] [Accepted: 01/25/2024] [Indexed: 02/09/2024] Open
Abstract
Hyperlipidemia predisposes individuals to cardiometabolic diseases, the most common cause of global mortality. Microsomal triglyceride transfer protein (MTP) transfers multiple lipids and is essential for the assembly of apolipoprotein B-containing lipoproteins. MTP inhibition lowers plasma lipids but causes lipid retention in the liver and intestine. Previous studies suggested two lipid transfer domains in MTP and that specific inhibition of triglyceride (TG) and not phospholipid (PL) transfer can lower plasma lipids without significant tissue lipid accumulation. However, how MTP transfers different lipids and the domains involved in these activities are unknown. Here, we tested a hypothesis that two different β-sandwich domains in MTP transfer TG and PL. Mutagenesis of charged amino acids in β2-sandwich had no effect on PL transfer activity indicating that they are not critical. In contrast, amino acids with bulky hydrophobic side chains in β1-sandwich were critical for both TG and PL transfer activities. Substitutions of these residues with smaller hydrophobic side chains or positive charges reduced, whereas negatively charged side chains severely attenuated MTP lipid transfer activities. These studies point to a common lipid transfer domain for TG and PL in MTP that is enriched with bulky hydrophobic amino acids. Furthermore, we observed a strong correlation in different MTP mutants with respect to loss of both the lipid transfer activities, again implicating a common binding site for TG and PL in MTP. We propose that targeting of areas other than the identified common lipid transfer domain might reduce plasma lipids without causing cellular lipid retention.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Swati Valmiki
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Rosario Recacha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Shahidul Islam
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA
| | - Steven Farber
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Lloyd Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Grossman Long Island School of Medicine, Mineola, New York, USA.
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3
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Grove JI, Lo PC, Shrine N, Barwell J, Wain LV, Tobin MD, Salter AM, Borkar AN, Cuevas-Ocaña S, Bennett N, John C, Ntalla I, Jones GE, Neal CP, Thomas MG, Kuht H, Gupta P, Vemala VM, Grant A, Adewoye AB, Shenoy KT, Balakumaran LK, Hollox EJ, Hannan NR, Aithal GP. Identification and characterisation of a rare MTTP variant underlying hereditary non-alcoholic fatty liver disease. JHEP Rep 2023; 5:100764. [PMID: 37484212 PMCID: PMC10362796 DOI: 10.1016/j.jhepr.2023.100764] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/28/2023] [Accepted: 04/11/2023] [Indexed: 07/25/2023] Open
Abstract
Background & Aims Non-alcoholic fatty liver disease (NAFLD) is a complex trait with an estimated prevalence of 25% globally. We aimed to identify the genetic variant underlying a four-generation family with progressive NAFLD leading to cirrhosis, decompensation, and development of hepatocellular carcinoma in the absence of common risk factors such as obesity and type 2 diabetes. Methods Exome sequencing and genome comparisons were used to identify the likely causal variant. We extensively characterised the clinical phenotype and post-prandial metabolic responses of family members with the identified novel variant in comparison with healthy non-carriers and wild-type patients with NAFLD. Variant-expressing hepatocyte-like cells (HLCs) were derived from human-induced pluripotent stem cells generated from homozygous donor skin fibroblasts and restored to wild-type using CRISPR-Cas9. The phenotype was assessed using imaging, targeted RNA analysis, and molecular expression arrays. Results We identified a rare causal variant c.1691T>C p.I564T (rs745447480) in MTTP, encoding microsomal triglyceride transfer protein (MTP), associated with progressive NAFLD, unrelated to metabolic syndrome and without characteristic features of abetalipoproteinaemia. HLCs derived from a homozygote donor had significantly lower MTP activity and lower lipoprotein ApoB secretion than wild-type cells, while having similar levels of MTP mRNA and protein. Cytoplasmic triglyceride accumulation in HLCs triggered endoplasmic reticulum stress, secretion of pro-inflammatory mediators, and production of reactive oxygen species. Conclusions We have identified and characterised a rare causal variant in MTTP, and homozygosity for MTTP p.I564T is associated with progressive NAFLD without any other manifestations of abetalipoproteinaemia. Our findings provide insights into mechanisms driving progressive NAFLD. Impact and Implications A rare genetic variant in the gene MTTP has been identified as responsible for the development of severe non-alcoholic fatty liver disease in a four-generation family with no typical disease risk factors. A cell line culture created harbouring this variant gene was characterised to understand how this genetic variation leads to a defect in liver cells, which results in accumulation of fat and processes that promote disease. This is now a useful model for studying the disease pathways and to discover new ways to treat common types of fatty liver disease.
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Affiliation(s)
- Jane I. Grove
- National Institute of Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & University of Nottingham, Nottingham, UK
- Nottingham Digestive Diseases Centre, Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
| | - Peggy C.K. Lo
- Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
- University of Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - Nick Shrine
- Genetic Epidemiology Group, Department of Population Health Sciences, University of Leicester, Leicester, UK
| | - Julian Barwell
- Clinical Genetics Department, University Hospitals Leicester NHS Trust, Leicester, UK
| | - Louise V. Wain
- Genetic Epidemiology Group, Department of Population Health Sciences, University of Leicester, Leicester, UK
- NIHR Leicester Respiratory Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Martin D. Tobin
- Genetic Epidemiology Group, Department of Population Health Sciences, University of Leicester, Leicester, UK
- NIHR Leicester Respiratory Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | | | - Aditi N. Borkar
- School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
| | - Sara Cuevas-Ocaña
- Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
- University of Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - Neil Bennett
- Genetic Epidemiology Group, Department of Population Health Sciences, University of Leicester, Leicester, UK
| | - Catherine John
- Genetic Epidemiology Group, Department of Population Health Sciences, University of Leicester, Leicester, UK
| | - Ioanna Ntalla
- Clinical Genetics Department, University Hospitals Leicester NHS Trust, Leicester, UK
| | - Gabriela E. Jones
- Clinical Genetics Department, University Hospitals Leicester NHS Trust, Leicester, UK
| | | | - Mervyn G. Thomas
- Ulverscroft Eye Unit, Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Helen Kuht
- Ulverscroft Eye Unit, Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Pankaj Gupta
- Department of Chemical Pathology and Metabolic Diseases, University Hospitals of Leicester NHS Trust, Leicester, UK
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Vishwaraj M. Vemala
- Department of Gastroenterology, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Allister Grant
- Department of Gastroenterology, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Adeolu B. Adewoye
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | | | | | - Edward J. Hollox
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Nicholas R.F. Hannan
- Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
- University of Nottingham Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - Guruprasad P. Aithal
- National Institute of Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & University of Nottingham, Nottingham, UK
- Nottingham Digestive Diseases Centre, Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
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4
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Mollet IG, Macedo MP. Pre-Diabetes-Linked miRNA miR-193b-3p Targets PPARGC1A, Disrupts Metabolic Gene Expression Profile and Increases Lipid Accumulation in Hepatocytes: Relevance for MAFLD. Int J Mol Sci 2023; 24:ijms24043875. [PMID: 36835287 PMCID: PMC9965679 DOI: 10.3390/ijms24043875] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 02/06/2023] [Accepted: 02/11/2023] [Indexed: 02/17/2023] Open
Abstract
Distinct plasma microRNA profiles associate with different disease features and could be used to personalize diagnostics. Elevated plasma microRNA hsa-miR-193b-3p has been reported in patients with pre-diabetes where early asymptomatic liver dysmetabolism plays a crucial role. In this study, we propose the hypothesis that elevated plasma hsa-miR-193b-3p conditions hepatocyte metabolic functions contributing to fatty liver disease. We show that hsa-miR-193b-3p specifically targets the mRNA of its predicted target PPARGC1A/PGC1α and consistently reduces its expression in both normal and hyperglycemic conditions. PPARGC1A/PGC1α is a central co-activator of transcriptional cascades that regulate several interconnected pathways, including mitochondrial function together with glucose and lipid metabolism. Profiling gene expression of a metabolic panel in response to overexpression of microRNA hsa-miR-193b-3p revealed significant changes in the cellular metabolic gene expression profile, including lower expression of MTTP, MLXIPL/ChREBP, CD36, YWHAZ and GPT, and higher expression of LDLR, ACOX1, TRIB1 and PC. Overexpression of hsa-miR-193b-3p under hyperglycemia also resulted in excess accumulation of intracellular lipid droplets in HepG2 cells. This study supports further research into potential use of microRNA hsa-miR-193b-3p as a possible clinically relevant plasma biomarker for metabolic-associated fatty liver disease (MAFLD) in dysglycemic context.
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Affiliation(s)
- Inês Guerra Mollet
- iNOVA4Health, NOVA Medical School (NMS), Faculdade de Ciências Médicas (FCM), Universidade NOVA de Lisboa, 1150-082 Lisboa, Portugal
- UCIBIO-Requimte, Faculdade de Ciências e Tecnologia (FCT), Universidade NOVA de Lisboa, 2825-149 Caparica, Portugal
- Correspondence: (I.G.M.); (M.P.M.)
| | - Maria Paula Macedo
- iNOVA4Health, NOVA Medical School (NMS), Faculdade de Ciências Médicas (FCM), Universidade NOVA de Lisboa, 1150-082 Lisboa, Portugal
- Associação Protectora dos Diabéticos de Portugal, Education Research Center (APDP-ERC), 1250-203 Lisbon, Portugal
- Correspondence: (I.G.M.); (M.P.M.)
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5
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Rajan S, Hofer P, Christiano A, Stevenson M, Ragolia L, Villa-Cuesta E, Fried SK, Lau R, Braithwaite C, Zechner R, Schwartz GJ, Hussain MM. Microsomal triglyceride transfer protein regulates intracellular lipolysis in adipocytes independent of its lipid transfer activity. Metabolism 2022; 137:155331. [PMID: 36228741 DOI: 10.1016/j.metabol.2022.155331] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/21/2022] [Accepted: 10/06/2022] [Indexed: 11/22/2022]
Abstract
BACKGROUND The triglyceride (TG) transfer activity of microsomal triglyceride transfer protein (MTP) is essential for lipoprotein assembly in the liver and intestine; however, its function in adipose tissue, which does not assemble lipoproteins, is unknown. Here we have elucidated the function of MTP in adipocytes. APPROACH AND RESULTS We demonstrated that MTP is present on lipid droplets in human adipocytes. Adipose-specific MTP deficient (A-Mttp-/-) male and female mice fed an obesogenic diet gained less weight than Mttpf/f mice, had less fat mass, smaller adipocytes and were insulin sensitive. A-Mttp-/- mice showed higher energy expenditure than Mttpf/f mice. During a cold challenge, A-Mttp-/- mice maintained higher body temperature by mobilizing more fatty acids. Biochemical studies indicated that MTP deficiency de-repressed adipose triglyceride lipase (ATGL) activity and increased TG lipolysis. Both wild type MTP and mutant MTP deficient in TG transfer activity interacted with and inhibited ATGL activity. Thus, the TG transfer activity of MTP is not required for ATGL inhibition. C-terminally truncated ATGL that retains its lipase activity interacted less efficiently than full-length ATGL. CONCLUSION Our findings demonstrate that adipose-specific MTP deficiency increases ATGL-mediated TG lipolysis and enhances energy expenditure, thereby resisting diet-induced obesity. We speculate that the regulatory function of MTP involving protein-protein interactions might have evolved before the acquisition of TG transfer activity in vertebrates. Adipose-specific inhibition of MTP-ATGL interactions may ameliorate obesity while avoiding the adverse effects associated with inhibition of the lipid transfer activity of MTP.
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Affiliation(s)
- Sujith Rajan
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Amanda Christiano
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Matthew Stevenson
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Louis Ragolia
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Eugenia Villa-Cuesta
- Department of Biology, College of Arts and Science, Adelphi University, Garden City, NY 11530, United States of America
| | - Susan K Fried
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - Raymond Lau
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Collin Braithwaite
- Department of Surgery, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Graz, Austria; BioTechMed-Graz, Austria; BioHealth Field of Excellence, University of Graz, Graz, Austria
| | - Gary J Schwartz
- Department of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, United States of America.
| | - M Mahmood Hussain
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, United States of America; Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY, United States of America.
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6
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Anaganti N, Chattopadhyay A, Poirier JT, Hussain MM. Generation of hepatoma cell lines deficient in microsomal triglyceride transfer protein. J Lipid Res 2022; 63:100257. [PMID: 35931202 PMCID: PMC9405095 DOI: 10.1016/j.jlr.2022.100257] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/03/2022] [Accepted: 07/08/2022] [Indexed: 01/05/2023] Open
Abstract
The microsomal triglyceride transfer protein (MTP) is essential for the secretion of apolipoprotein B (apoB)48- and apoB100-containing lipoproteins in the intestine and liver, respectively. Loss of function mutations in MTP cause abetalipoproteinemia. Heterologous cells are used to evaluate the function of MTP in apoB secretion to avoid background MTP activity in liver and intestine-derived cells. However, these systems are not suitable to study the role of MTP in the secretion of apoB100-containing lipoproteins, as expression of a large apoB100 peptide using plasmids is difficult. Here, we report a new cell culture model amenable for studying the role of different MTP mutations on apoB100 secretion. The endogenous MTTP gene was ablated in human hepatoma Huh-7 cells using single guide RNA and RNA-guided clustered regularly interspaced short palindromic repeats-associated sequence 9 ribonucleoprotein complexes. We successfully established three different clones that did not express any detectable MTTP mRNA or MTP protein or activity. These cells were defective in secreting apoB-containing lipoproteins and accumulated lipids. Furthermore, we show that transfection of these cells with plasmids expressing human MTTP cDNA resulted in the expression of MTP protein, restoration of triglyceride transfer activity, and secretion of apoB100. Thus, these new cells can be valuable tools for studying structure-function of MTP, roles of different missense mutations in various lipid transfer activities of MTP, and their ability to support apoB100 secretion, compensatory changes associated with loss of MTP, and in the identification of novel proteins that may require MTP for their synthesis and secretion.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - Atrayee Chattopadhyay
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA
| | - John T Poirier
- Perlmutter Cancer Center, New York University Langone Health, New York, NY, USA
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, Mineola, NY, USA; VA New York Harbor Healthcare System, Brooklyn, NY, USA.
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7
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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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8
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Xue M, Yao T, Xue M, Francis F, Qin Y, Jia M, Li J, Gu X. Mechanism Analysis of Metabolic Fatty Liver on Largemouth bass (Micropterus salmoides) Based on Integrated Lipidomics and Proteomics. Metabolites 2022; 12:metabo12080759. [PMID: 36005631 PMCID: PMC9415018 DOI: 10.3390/metabo12080759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/12/2022] [Accepted: 08/14/2022] [Indexed: 11/26/2022] Open
Abstract
Metabolic fatty liver disease caused by high-starch diet restricted the intensive and sustainable development of carnivorous fish such as largemouth bass. In this study, the combination liver proteomic and lipidomic approach was employed to investigate the key signaling pathways and identify the critical biomarkers of fatty liver in largemouth bass. Joint analysis of the correlated differential proteins and lipids revealed nine common metabolic pathways; it was determined that FABP1 were significantly up-regulated in terms of transporting more triglycerides into the liver, while ABCA1 and VDAC1 proteins were significantly down-regulated in terms of preventing the transport of lipids and cholesterol out of the liver, leading to triglyceride accumulation in hepatocyte, eventually resulting in metabolic fatty liver disease. The results indicate that FABP1, ABCA1 and VDAC1 could be potential biomarkers for treating metabolic fatty liver disease of largemouth bass.
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Affiliation(s)
- Moyong Xue
- Feed Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China
- Functional & Evolutionary Entomology, Agro-Bio-Tech Gembloux, University of Liege, 5030 Gembloux, Belgium
- Institute of Animal Science, Chinese Academy of Agriculture Sciences, Beijing 100193, China
| | - Ting Yao
- Beijing Institute of Feed Control, Beijing 110108, China
| | - Min Xue
- Feed Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China
| | - Frédéric Francis
- Functional & Evolutionary Entomology, Agro-Bio-Tech Gembloux, University of Liege, 5030 Gembloux, Belgium
| | - Yuchang Qin
- Institute of Animal Science, Chinese Academy of Agriculture Sciences, Beijing 100193, China
| | - Ming Jia
- Feed Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China
| | - Junguo Li
- Feed Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China
| | - Xu Gu
- Feed Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China
- Correspondence:
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9
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Anaganti N, Rajan S, Hussain MM. An improved assay to measure the phospholipid transfer activity of microsomal triglyceride transport protein. J Lipid Res 2021; 62:100136. [PMID: 34673018 PMCID: PMC8569553 DOI: 10.1016/j.jlr.2021.100136] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/27/2021] [Accepted: 10/07/2021] [Indexed: 12/02/2022] Open
Abstract
Microsomal triglyceride transfer protein (MTP) is essential for the assembly and secretion of apolipoprotein B-containing lipoproteins. MTP transfers diverse lipids such as triacylglycerol (TAG) and phospholipids (PLs) between vesicles in vitro. Previously, we described methods to measure these transfer activities using N-7-nitro-2-1,3-benzoxadiazol-4-yl (NBD)-labeled lipids. The NBD-TAG transfer assay is sensitive and can measure MTP activity in cell and tissue homogenates. In contrast, the NBD-PL transfer assay shows high background and is less sensitive; therefore, purified MTP is required to measure its PL transfer activity. Here, we optimized the assay to measure also the PL transfer activity of MTP in cell and tissue homogenates. We found that donor vesicles containing dioleoylphosphoethanolamine and palmitoyloleoylphosphoethanolamine result in a low background signal and are suitable to assay the PL transfer activity of MTP. This assay was capable of measuring protein-dependent and substrate-dependent saturation kinetics. Furthermore, the MTP inhibitor lomitapide blocked this transfer activity. One drawback of the PL transfer assay is that it is less sensitive at physiological temperature than at room temperature, and it requires longer incubation times than the TAG transfer assay. Nevertheless, this significantly improved sensitive assay is simple and easy to perform, involves few steps, can be conducted at room temperature, and is suitable for high-throughput screening to identify inhibitors. This assay can be adapted to measure other PL transfer proteins and to address biological and physiological importance of these activities.
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Affiliation(s)
- Narasimha Anaganti
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, USA
| | - Sujith Rajan
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, USA
| | - M Mahmood Hussain
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY 11501, USA; VA New York Harbor Healthcare System, Brooklyn, NY 11209, USA.
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10
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Rajan S, de Guzman HC, Palaia T, Goldberg IJ, Hussain MM. A simple, rapid, and sensitive fluorescence-based method to assess triacylglycerol hydrolase activity. J Lipid Res 2021; 62:100115. [PMID: 34508728 PMCID: PMC8488599 DOI: 10.1016/j.jlr.2021.100115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 08/26/2021] [Accepted: 08/30/2021] [Indexed: 01/22/2023] Open
Abstract
Lipases constitute an important class of water-soluble enzymes that catalyze the hydrolysis of hydrophobic triacylglycerol (TAG). Their enzymatic activity is typically measured using multistep procedures involving isolation and quantification of the hydrolyzed products. We report here a new fluorescence method to measure lipase activity in real time that does not require the separation of substrates from products. We developed this method using adipose triglyceride lipase (ATGL) and lipoprotein lipase (LpL) as model lipases. We first incubated a source of ATGL or LpL with substrate vesicles containing nitrobenzoxadiazole (NBD)-labeled TAG, then measured increases in NBD fluorescence, and calculated enzyme activities. Incorporation of NBD-TAG into phosphatidylcholine (PC) vesicles resulted in some hydrolysis; however, incorporation of phosphatidylinositol into these NBD-TAG/PC vesicles and increasing the ratio of NBD-TAG to PC greatly enhanced substrate hydrolysis. This assay was also useful in measuring the activity of pancreatic lipase and hormone-sensitive lipase. Next, we tested several small-molecule lipase inhibitors and found that orlistat inhibits all lipases, indicating that it is a pan-lipase inhibitor. In short, we describe a simple, rapid, fluorescence-based triacylglycerol hydrolysis assay to assess four major TAG hydrolases: intracellular ATGL and hormone-sensitive lipase, LpL localized at the extracellular endothelium, and pancreatic lipase present in the intestinal lumen. The major advantages of this method are its speed, simplicity, and elimination of product isolation. This assay is potentially applicable to a wide range of lipases, is amenable to high-throughput screening to discover novel modulators of triacylglycerol hydrolases, and can be used for diagnostic purposes.
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Affiliation(s)
- Sujith Rajan
- Department of Foundations of Medicine, NYU Long Island School of Medicine, and Diabetes and Obesity Research Center, NYU Langone Hospitals - Long Island, Mineola, NY, USA
| | - Hazel C de Guzman
- Department of Foundations of Medicine, NYU Long Island School of Medicine, and Diabetes and Obesity Research Center, NYU Langone Hospitals - Long Island, Mineola, NY, USA; Department of Environmental Medicine, NYU Grossman School of Medicine, New York, NY, USA
| | - Thomas Palaia
- Department of Foundations of Medicine, NYU Long Island School of Medicine, and Diabetes and Obesity Research Center, NYU Langone Hospitals - Long Island, Mineola, NY, USA
| | - Ira J Goldberg
- Division of Endocrinology, Department of Medicine, NYU Grossman School of Medicine, New York, NY, USA
| | - M Mahmood Hussain
- Department of Foundations of Medicine, NYU Long Island School of Medicine, and Diabetes and Obesity Research Center, NYU Langone Hospitals - Long Island, Mineola, NY, USA; VA New York Harbor Healthcare System, Brooklyn, NY, USA.
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11
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Takahashi M, Ozaki N, Nagashima S, Wakabayashi T, Iwamoto S, Ishibashi S. Normal plasma apoB48 despite the virtual absence of apoB100 in a compound heterozygote with novel mutations in the MTTP gene. J Clin Lipidol 2021; 15:569-573. [PMID: 34052173 DOI: 10.1016/j.jacl.2021.04.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/23/2021] [Accepted: 04/28/2021] [Indexed: 11/27/2022]
Abstract
"Normotriglyceridemic abetalipoproteinemia (ABL)" was originally described as a clinical entity distinct from either ABL or hypobetalipoproteinemia. Subsequent studies identified mutations in APOB gene which encoded truncated apoB longer than apoB48. Therefore, "Normotriglyceridemic ABL" can be a subtype of homozygous familial hypobetalipoproteinemia 1. Here, we report an atypical female case of ABL who was initially diagnosed with "normotriglyceridemic ABL", because she had normal plasma apoB48 despite the virtual absence of apoB100 and low plasma TG level. Next generation sequencing revealed that she was a compound heterozygote of two novel MTTP mutations: nonsense (p.Q272X) and missense (p.G709R). We speculate that p.G709R might confer residual triglyceride transfer activity of MTTP preferentially in the intestinal epithelium to the hepatocytes, allowing production of apoB48. Together, "normotriglyceridemic ABL" may be a heterogenous disorder which is caused by specific mutations in either APOB or MTTP gene.
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Affiliation(s)
- Manabu Takahashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
| | - Nobuaki Ozaki
- Division of Endocrinology, Japanese Red Cross Nagoya Daiichi Hospital, Nagoya 453-8511, Japan
| | - Shuichi Nagashima
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Tetsuji Wakabayashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Sadahiko Iwamoto
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
| | - Shun Ishibashi
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan.
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12
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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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13
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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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14
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Walsh MT, Celestin OM, Thierer JH, Rajan S, Farber SA, Hussain MM. Model systems for studying the assembly, trafficking, and secretion of apoB lipoproteins using fluorescent fusion proteins. J Lipid Res 2020; 61:316-327. [PMID: 31888978 DOI: 10.1194/jlr.ra119000259] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 12/24/2019] [Indexed: 11/20/2022] Open
Abstract
apoB exists as apoB100 and apoB48, which are mainly found in hepatic VLDLs and intestinal chylomicrons, respectively. Elevated plasma levels of apoB-containing lipoproteins (Blps) contribute to coronary artery disease, diabetes, and other cardiometabolic conditions. Studying the mechanisms that drive the assembly, intracellular trafficking, secretion, and function of Blps remains challenging. Our understanding of the intracellular and intraorganism trafficking of Blps can be greatly enhanced, however, with the availability of fusion proteins that can help visualize Blp transport within cells and between tissues. We designed three plasmids expressing human apoB fluorescent fusion proteins: apoB48-GFP, apoB100-GFP, and apoB48-mCherry. In Cos-7 cells, transiently expressed fluorescent apoB proteins colocalized with calnexin and were only secreted if cells were cotransfected with microsomal triglyceride transfer protein. The secreted apoB-fusion proteins retained the fluorescent protein and were secreted as lipoproteins with flotation densities similar to plasma HDL and LDL. In a rat hepatoma McA-RH7777 cell line, the human apoB100 fusion protein was secreted as VLDL- and LDL-sized particles, and the apoB48 fusion proteins were secreted as LDL- and HDL-sized particles. To monitor lipoprotein trafficking in vivo, the apoB48-mCherry construct was transiently expressed in zebrafish larvae and was detected throughout the liver. These experiments show that the addition of fluorescent proteins to the C terminus of apoB does not disrupt their assembly, localization, secretion, or endocytosis. The availability of fluorescently labeled apoB proteins will facilitate the exploration of the assembly, degradation, and transport of Blps and help to identify novel compounds that interfere with these processes via high-throughput screening.
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Affiliation(s)
- Meghan T Walsh
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York
| | - Oni M Celestin
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD
| | - James H Thierer
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD
| | - Sujith Rajan
- Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY.,Diabetes and Obesity Research Center, New York University Winthrop Hospital, Mineola, NY
| | - Steven A Farber
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD
| | - M Mahmood Hussain
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York .,Department of Foundations of Medicine, New York University Long Island School of Medicine, Mineola, NY.,Diabetes and Obesity Research Center, New York University Winthrop Hospital, Mineola, NY.,Department of Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY
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15
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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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16
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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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17
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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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18
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Abstract
BACKGROUND Abetalipoproteinemia and homozygous hypobetalipoproteinemia are classical Mendelian autosomal recessive and co-dominant conditions, respectively, which are phenotypically similar and are usually caused by bi-allelic mutations in MTTP and APOB genes, respectively. Instances of more complex patterns of genomic variants resulting in this distinct phenotype have not been reported. METHODS A 43 year-old male had a longstanding severe deficiency of apolipoprotein (apo) B-containing lipoproteins and circulating fat soluble vitamins consistent with either abetalipoproteinemia or homozygous familial hypobetalipoproteinemia (FHBL). He also had acanthocytosis, a long term history of fat malabsorption, and mild retinopathy, but was free from coagulopathy, myopathy and neuropathy. He had taken high dose oral fat soluble vitamins since childhood. RESULTS Targeted next generation DNA sequencing revealed several rare heterozygous missense variants in both MTTP and APOB genes known or predicted to be deleterious, in addition to a novel heterozygous missense variant in SAR1B, which encodes the gene causing chylomicron retention disease. Evaluation of first degree relatives with mild FHBL clarified the segregation of variants. CONCLUSIONS The proband's characteristic phenotype likely resulted from an oligogenic interaction involving multiple rare variants in MTTP and APOB, and related genes, each of which individually was associated with a milder or minimal clinical and biochemical phenotype.
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Affiliation(s)
- Linda R Wang
- Department of Medicine and Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 4288A - 1151 Richmond Street North, London, ON, N6A 5B7, Canada
| | - Adam D McIntyre
- Department of Medicine and Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 4288A - 1151 Richmond Street North, London, ON, N6A 5B7, Canada
| | - Robert A Hegele
- Department of Medicine and Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 4288A - 1151 Richmond Street North, London, ON, N6A 5B7, Canada.
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Ensari A, Kelsen J, Russo P. Newcomers in paediatric GI pathology: childhood enteropathies including very early onset monogenic IBD. Virchows Arch 2017; 472:111-123. [PMID: 28718031 DOI: 10.1007/s00428-017-2197-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 07/02/2017] [Accepted: 07/06/2017] [Indexed: 12/16/2022]
Abstract
Childhood enteropathies are a group of diseases causing severe chronic (>2-3 weeks) diarrhoea often starting in the first week of life with the potential for fatal complications for the affected infant. Early identification and accurate classification of childhood enteropathies are, therefore, crucial for making treatment decisions to prevent life-threatening complications. Childhood enteropathies are classified into four groups based on the underlying pathology: (i) conditions related to defective digestion, absorption and transport of nutrients and electrolytes; (ii) disorders related to enterocyte differentiation and polarization; (iii) defects of enteroendocrine cell differentiation; and (iv) disorders associated with defective modulation of intestinal immune response. While the intestinal mucosa is usually normal in enteropathies related to congenital transport or enzyme deficiencies, the intestinal biopsy in other disorders may reveal a wide range of abnormalities varying from normal villous architecture to villous atrophy and/or inflammation, or features specific to the underlying disorder including epithelial abnormalities, lipid vacuolization in the enterocytes, absence of plasma cells, lymphangiectasia, microorganisms, and mucosal eosinophilic or histiocytic infiltration. This review intends to provide an update on small intestinal biopsy findings in childhood enteropathies, the "newcomers", including very early onset monogenic inflammatory bowel disease (IBD), in particular, for the practicing pathologist.
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Affiliation(s)
- Arzu Ensari
- Department of Pathology, Ankara University Medical School, Sihhiye, 06100, Ankara, Turkey.
| | - Judith Kelsen
- Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, Perelman School at the University of Pennsylvania, 3401 Civic Center Boulevard, 5 NW26, Philadelphia, PA, 19104, USA
| | - Pierre Russo
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Perelman School of Medicine at The University of Pennsylvania, 3401 Civic Center Boulevard, 5 NW26, Philadelphia, PA, 19104, USA
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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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22
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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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Bakillah A, Hussain MM. Mice subjected to aP2-Cre mediated ablation of microsomal triglyceride transfer protein are resistant to high fat diet induced obesity. Nutr Metab (Lond) 2016; 13:1. [PMID: 26752997 PMCID: PMC4706691 DOI: 10.1186/s12986-016-0061-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/03/2016] [Indexed: 02/06/2023] Open
Abstract
Background Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP has been shown on the surface of lipid droplets of adipocytes; however its function in adipose tissue is not well defined. We hypothesized that MTP may play critical role in adipose lipid droplet formation and expansion. Methods Plasmids mediated overexpression and siRNA mediated knockdown of Mttp gene were performed in 3T3-L1 pre-adipocytes to evaluate the effects of MTP on cell differentiation and triglyceride accumulation. Adipose-specific knockdown of MTP was achieved in mice bybreeding MTP floxed (Mttpfl/fl) mice with aP2-Cre recombinase transgenic mice. Adipose-specific MTP deficient (A-Mttp-/-) mice were fed 60 % high-fat diet (HFD), and the effects of MTP knockdown on body weight, body fat composition, plasma and tissues lipid composition, glucose metabolism, lipogenesis and intestinal absorption was studied. Lipids were measured in total fasting plasma and size fractionated plasma using colorimetric assays. Gene expression was investigated by Real-Time quantitative PCR. All data was assessed using t-test, ANOVA. Results MTP expression increased during early differentiation in 3T3-L1 cells, and declined later. The increases in MTP expression preceded PPARγ expression. MTP overexpression enhanced lipid droplets formation, and knockdown attenuated cellular lipid accumulation. These studies indicated that MTP positively affects adipogenesis. The ablation of the Mttp gene using aP2-Cre (A-Mttp-/-) in mice resulted in a lean phenotype when fed a HFD. These mice had reduced white adipose tissue compared with wild-type Mttpfl/fl mice. The adipose tissue of A-Mttp-/- mice had increased number of smaller size adipocytes and less macrophage infiltration. Further, these mice were protected from HFD-induced fatty liver. The A-Mttp-/- mice had moderate increase in plasma triglyceride, but normal cholesterol, glucose and insulin levels. Gene expression analysis showed that the adipose tissue of the A-Mttp-/- mice had significantly lower mRNA levels of PPARγ and its downstream targets. Conclusion These data suggest that MTP might modulate adipogenesis by influencing PPARγ expression, and play a role in the accretion of lipids to form larger lipid droplets. Thus, agents that inactivate adipose MTP may be useful anti-obesity drugs.
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Affiliation(s)
- Ahmed Bakillah
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203 USA ; Department of Pediatrics, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203 USA
| | - M Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203 USA ; Department of Pediatrics, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203 USA ; VA New York Harbor Healthcare System, Brooklyn, NY 11209 USA
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Hsiao PJ, Lee MY, Wang YT, Jiang HJ, Lin PC, Yang YHC, Kuo KK. MTTP-297H polymorphism reduced serum cholesterol but increased risk of non-alcoholic fatty liver disease-a cross-sectional study. BMC MEDICAL GENETICS 2015; 16:93. [PMID: 26458397 PMCID: PMC4603340 DOI: 10.1186/s12881-015-0242-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 10/05/2015] [Indexed: 12/20/2022]
Abstract
Background Microsomal triglyceride transfer protein (MTP) works to lipidate and assemble the apoB-containing lipoproteins in liver. It closely links up the hepatic secretion of lipid to regulate serum lipid and atherosclerosis. Cases of MTTP gene mutation is characterized by abetalipoproteinemia and remarkable hepatic steatosis or cirrhosis. Several MTTP polymorphisms have been reported relating to metabolic syndrome, hyperlipidemia and steatohepatitis. We supposed the regulation of serum lipids and risk of non-alcoholic fatty liver disease (NAFLD) formation may be modified by individual susceptibility related to the MTTP polymorphisms. Methods and results A cross-sectional population of 1193 subjects, 1087 males and 106 females mean aged 45.9 ± 8.9 years, were enrolled without recognized secondary hyperlipidemia. Fasting serum lipid, insulin, and non-esterified fatty acid were assessed and transformed to insulin resistance index, HOMA-IR and Adipo-IR. After ruling out alcohol abuser, non-alcoholic fatty liver disease (NAFLD) was diagnosed by abdominal ultrasound. Five common MTTP polymorphisms (promoter -493G/T, E98D, I128T, N166S, and Q297H) were conducted by TaqMan assay. Multivariate regression analysis was used to estimate their impact on serum lipid and NAFLD risk. Assessment revealed a differential impact on LDL-C and non-HDL-C, which were sequentially determined by the Q297H polymorphism, insulin resistance, body mass index and age. Carriers of homozygous minor allele (297H) had significantly lower LDL-C and non-HDL-C but higher risk for NAFLD. Molecular modeling of the 297H variant demonstrated higher free energy, potentially referring to an unstable structure and functional sequence. Conclusion These results evidenced the MTTP polymorphisms could modulate the lipid homeostasis to determine the serum lipids and risk of NAFLD. The MTTP 297H polymorphism interacted with age, insulin resistance and BMI to decrease serum apoB containing lipoproteins (LDL-C and non-HDL-C) but increase the risk of NAFLD formation. Electronic supplementary material The online version of this article (doi:10.1186/s12881-015-0242-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Pi-Jung Hsiao
- Division of Endocrinology and Metabolism, Department of Internal Medicine; Kaohsiung Municipal Siaogang Hospital, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. .,School of Medicine, College of Medicine, Kaohsiung Medical University, 100 Tzyou 1st Rd, Kaohsiung, 807, Taiwan.
| | - Mei-Yueh Lee
- Division of Endocrinology and Metabolism, Department of Internal Medicine; Kaohsiung Municipal Siaogang Hospital, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
| | - Yeng-Tseng Wang
- Department of Biochemistry, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
| | - He-Jiun Jiang
- Division of Endocrinology and Metabolism, Department of Internal Medicine; Kaohsiung Municipal Siaogang Hospital, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
| | - Pi-Chen Lin
- Division of Endocrinology and Metabolism, Department of Internal Medicine; Kaohsiung Municipal Siaogang Hospital, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
| | - Yi-Hsin Connie Yang
- School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan.
| | - Kung-Kai Kuo
- School of Medicine, College of Medicine, Kaohsiung Medical University, 100 Tzyou 1st Rd, Kaohsiung, 807, Taiwan. .,Division of Hepatobiliopancreatic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
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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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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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27
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Levy E. Insights from human congenital disorders of intestinal lipid metabolism. J Lipid Res 2014; 56:945-62. [PMID: 25387865 DOI: 10.1194/jlr.r052415] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Indexed: 12/24/2022] Open
Abstract
The intestine must challenge the profuse daily flux of dietary fat that serves as a vital source of energy and as an essential component of cell membranes. The fat absorption process takes place in a series of orderly and interrelated steps, including the uptake and translocation of lipolytic products from the brush border membrane to the endoplasmic reticulum, lipid esterification, Apo synthesis, and ultimately the packaging of lipid and Apo components into chylomicrons (CMs). Deciphering inherited disorders of intracellular CM elaboration afforded new insight into the key functions of crucial intracellular proteins, such as Apo B, microsomal TG transfer protein, and Sar1b GTPase, the defects of which lead to hypobetalipoproteinemia, abetalipoproteinemia, and CM retention disease, respectively. These "experiments of nature" are characterized by fat malabsorption, steatorrhea, failure to thrive, low plasma levels of TGs and cholesterol, and deficiency of liposoluble vitamins and essential FAs. After summarizing and discussing the functions and regulation of these proteins for reader's comprehension, the current review focuses on their specific roles in malabsorptions and dyslipidemia-related intestinal fat hyperabsorption while dissecting the spectrum of clinical manifestations and managements. The influence of newly discovered proteins (proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 protein) on fat absorption has also been provided. Finally, it is stressed how the overexpression or polymorphism status of the critical intracellular proteins promotes dyslipidemia and cardiometabolic disorders.
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Affiliation(s)
- Emile Levy
- Research Centre, CHU Sainte-Justine and Department of Nutrition, Université de Montréal, Montreal, Quebec H3T 1C5, Canada
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Sirtori CR, Pavanello C, Bertolini S. Microsomal transfer protein (MTP) inhibition-a novel approach to the treatment of homozygous hypercholesterolemia. Ann Med 2014; 46:464-74. [PMID: 24987866 DOI: 10.3109/07853890.2014.931100] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Homozygous familial hypercholesterolemia (HoFH) represents the most severe lipoprotein disorder, generally attributable to mutation(s) of the low-density lipoprotein receptor (LDL-R), i.e. autosomal dominant hypercholesterolemia type 1 (ADH1). Much lower percentages are due to alterations of apolipoprotein B (ADH2), or gain-of-function mutations of proprotein convertase subtilisin/kexin type 9 (PCSK9) (ADH3). In certain geographical areas a significant number of patients may be affected by an autosomal recessive hypercholesterolemia (ARH). Mutations may be also combined (two mutations of the same gene, compound heterozygosity), or two in different genes (double heterozygosity). Among the most innovative therapeutic approaches made available recently, inhibitors of the microsomal transfer protein (MTP) system have shown a high clinical potential. MTP plays a critical role in the assembly/secretion of very-low-density lipoproteins (VLDL), and its absence leads to apo B deficiency. MTP antagonists dramatically lower LDL-cholesterol (LDL-C) in animals, although a reported increase of liver fat delayed their clinical development. Lomitapide, the best-studied MTP inhibitor, reduces LDL-C by 50% or more in HoFH patients, with modest, reversible, liver steatosis. Recent US approval has confirmed an acceptable tolerability, provided patients adhere to a strictly low-fat regimen. There are no clinical data on atherosclerosis reduction/regression, but animal models provide encouraging results.
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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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Abstract
OPINION STATEMENT Ataxia can originate from many genetic defects, but also from nongenetic causes. To be able to provide treatment, the first step is to establish the right diagnosis. Once the cause of the ataxia is defined, some specific treatments may be available. For example, the nongenetic ataxias that arise from vitamin deficiencies can improve following treatment. In most cases, however, therapies do not cure the disease and are purely symptomatic. Physiotherapy and occupational therapy are effective in all type of ataxias and often remain the most efficient treatment option for these patients to maximize their quality of life.
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Abstract
The indication for a small intestinal biopsy is usually the work-up of malabsorption, a clinicopathologic picture caused by a number of infectious and noninfectious inflammatory conditions. The biopsy is generally taken through an endoscope, by either forceps or suction, from the duodenum or proximal jejunum. Depending upon the underlying condition, morphological abnormalities are seen in malabsorption range from normal mucosa with increased intraepithelial lymphocytes (gluten-sensitive enteropathy, viral gastroenteritis, food allergies, etc.), villous shortening with crypt hyperplasia (celiac disease (CD), treated CD, tropical sprue, and bacterial overgrowth), to completely flat mucosa (CD, refractory sprue, enteropathy-induced T-cell lymphoma, and autoimmune enteropathy). Infectious agents that affect gastrointestinal tract can be grouped as food-borne and water-borne bacteria, opportunistic infections (bacterial, fungal, and viral), viral infections (extremely rarely biopsied), and parasitic and helminthic infections. The majority of these infections are, however, self-limited. Although biopsy is more invasive, the use of this procedure allows detection of other causes, including Whipple's disease, other protozoan forms of diarrhea (e.g., cryptosporidiosis, isosporiasis, or cyclosporiasis), Crohn's disease, or lymphoma that may also present as diarrhea and malabsorption.
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