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Aziz F, Sam R, Lew SQ, Massie L, Misra M, Roumelioti ME, Argyropoulos CP, Ing TS, Tzamaloukas AH. Pseudohyponatremia: Mechanism, Diagnosis, Clinical Associations and Management. J Clin Med 2023; 12:4076. [PMID: 37373769 DOI: 10.3390/jcm12124076] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 06/08/2023] [Accepted: 06/13/2023] [Indexed: 06/29/2023] Open
Abstract
Pseudohyponatremia remains a problem for clinical laboratories. In this study, we analyzed the mechanisms, diagnosis, clinical consequences, and conditions associated with pseudohyponatremia, and future developments for its elimination. The two methods involved assess the serum sodium concentration ([Na]S) using sodium ion-specific electrodes: (a) a direct ion-specific electrode (ISE), and (b) an indirect ISE. A direct ISE does not require dilution of a sample prior to its measurement, whereas an indirect ISE needs pre-measurement sample dilution. [Na]S measurements using an indirect ISE are influenced by abnormal concentrations of serum proteins or lipids. Pseudohyponatremia occurs when the [Na]S is measured with an indirect ISE and the serum solid content concentrations are elevated, resulting in reciprocal depressions in serum water and [Na]S values. Pseudonormonatremia or pseudohypernatremia are encountered in hypoproteinemic patients who have a decreased plasma solids content. Three mechanisms are responsible for pseudohyponatremia: (a) a reduction in the [Na]S due to lower serum water and sodium concentrations, the electrolyte exclusion effect; (b) an increase in the measured sample's water concentration post-dilution to a greater extent when compared to normal serum, lowering the [Na] in this sample; (c) when serum hyperviscosity reduces serum delivery to the device that apportions serum and diluent. Patients with pseudohyponatremia and a normal [Na]S do not develop water movement across cell membranes and clinical manifestations of hypotonic hyponatremia. Pseudohyponatremia does not require treatment to address the [Na]S, making any inadvertent correction treatment potentially detrimental.
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Affiliation(s)
- Fahad Aziz
- Department of Medicine, Division of Nephrology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Ramin Sam
- Department of Medicine, Zuckerberg San Francisco General Hospital, School of Medicine, University of California in San Francisco, San Francisco, CA 94110, USA
| | - Susie Q Lew
- Department of Medicine, School of Medicine and Health Sciences, George Washington University, Washington, DC 20052, USA
| | - Larry Massie
- Department of Pathology, Raymond G. Murphy Veterans Affairs Medical Center, University of New Mexico School of Medicine, Albuquerque, NM 87108, USA
| | - Madhukar Misra
- Department of Medicine, Division of Nephrology, University of Missouri, Columbia, MO 65211, USA
| | - Maria-Eleni Roumelioti
- Department of Medicine, Division of Nephrology, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Christos P Argyropoulos
- Department of Medicine, Division of Nephrology, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Todd S Ing
- Department of Medicine, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - Antonios H Tzamaloukas
- Research Service, Department of Medicine, Raymond G. Murphy Veterans Affairs Medical Center, University of New Mexico School of Medicine, Albuquerque, NM 87108, USA
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2
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Meroni M, Longo M, Paolini E, Tria G, Ripolone M, Napoli L, Moggio M, Fracanzani AL, Dongiovanni P. Expanding the phenotypic spectrum of non-alcoholic fatty liver disease and hypertriglyceridemia. Front Nutr 2022; 9:967899. [PMID: 36185699 PMCID: PMC9521372 DOI: 10.3389/fnut.2022.967899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 07/27/2022] [Indexed: 11/26/2022] Open
Abstract
Background and aims Hypertriglyceridemia is a common feature of metabolic syndrome (MetS), as well as of non-alcoholic fatty liver disease (NAFLD), which is considered the hepatic manifestation of MetS. Fat accumulation in hepatocytes may alter mitochondrial homeostasis predisposing to advanced liver disease. Here, we report a case of a 40-year-old woman with early aggressive NAFLD due to severe hypertriglyceridemia that ensued from a combination of genetic variants and additional metabolic risk factors. Methods Genetic screening was performed by using whole-exome sequencing (WES), and mitochondrial structures were evaluated by TEM. Results At presentation, the patient is reported to have hepatomegaly, hypertriglyceridemia, and raised transaminases. Genetic analysis revealed that the patient beard heritable alterations in genes implicated in lipid handling, among which APOB, APOE, CETP, and HSPG2, accompanied by missense mutations in genes involved in mitochondrial function, i.e., AK2, ALG6, ASPA, NDUFAF1, POLG, and TMEM70. Abdominal ultrasound (US) and transient elastography were suggestive of severe hepatic steatosis and fibrosis. A liver biopsy confirmed the diagnosis of non-alcoholic steatohepatitis (NASH)-related fibrosis. Thus, to better outline whether mutations involved in lipid remodeling and mitochondrial function may also affect organelles’ morphology, we exploited TEM. Along with multifaceted abnormalities of mitochondrial architecture that have been already observed in patients with NAFLD, astonishing ultrastructural defects, such as mitochondrial vacuolization, sub-compartmentalization, and onion-like mitochondria, were identified. Conclusion The anomalies reported may expand the phenotypic spectrum of mitochondrial abnormalities observed in patients with NAFLD, which may contribute to the switching toward a progressive disease.
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Affiliation(s)
- Marica Meroni
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Miriam Longo
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
- Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy
| | - Erika Paolini
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Milan, Italy
| | - Giada Tria
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Michela Ripolone
- Neuromuscular and Rare Diseases Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Laura Napoli
- Neuromuscular and Rare Diseases Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Maurizio Moggio
- Neuromuscular and Rare Diseases Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Anna Ludovica Fracanzani
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Paola Dongiovanni
- General Medicine and Metabolic Diseases, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
- *Correspondence: Paola Dongiovanni,
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3
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Kassner U, Hollstein T, Grenkowitz T, Wühle-Demuth M, Salewsky B, Demuth I, Dippel M, Steinhagen-Thiessen E. Gene Therapy in Lipoprotein Lipase Deficiency: Case Report on the First Patient Treated with Alipogene Tiparvovec Under Daily Practice Conditions. Hum Gene Ther 2019; 29:520-527. [PMID: 29641318 DOI: 10.1089/hum.2018.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
One-year results are reported of the first lipoprotein lipase deficiency (LPLD) patient treated with alipogene tiparvovec, which is indicated for the treatment of patients with genetically confirmed LPLD suffering from acute and recurrent pancreatitis attacks (PAs) despite dietary restrictions and expressing >5% of lipoprotein lipase (LPL) mass compared to a healthy control. During clinical development, alipogene tiparvovec has shown improvement of chylomicron metabolism and reduction of pancreatitis incidence up to 5.8 years post treatment. A 43-year-old female presented with severe hypertriglyceridemia (median triglyceride [TG] value of 3,465 mg/dL) and a history of 37 PAs within the last 25 years, despite treatment with fibrates, omega 3 fatty acids, and-since 2012-twice-weekly lipid apheresis. LPLD was confirmed by identification of two different pathogenic variants in the LPL gene located on separate alleles and therefore constituting a compound heterozygous state. With a detectable LPL mass level of 55.1 ng/mL, the patient was eligible for alipogene tiparvovec treatment, and in September 2015, she receved 40 injections (1 × 1012 genome copies/kg) in the muscles of her upper legs under epidural anesthesia and immunosuppressive therapy. Alipogene tiparvovec was well tolerated: no injection site or systemic reactions were observed. Median TG values decreased by 52%, dropping to 997 mg/dL at month 3 and increasing thereafter. Within the first 18 months post treatment, the patient discontinued plasmapheresis and had no abdominal pain or PAs. In March 2017, the patient suffered from a PA due to diet violation. Within the first 12 months post treatment, overall quality of life improved, and no change in humoral or cellular immune response against LPL or AAV-1 was observed. In conclusion, alipogene tiparvovec was well tolerated, with a satisfactory response to treatment. Long-term effects on the recurrence of pancreatitis continue to be monitored.
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Affiliation(s)
- Ursula Kassner
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
| | - Tim Hollstein
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
| | - Thomas Grenkowitz
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
| | - Marion Wühle-Demuth
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
| | - Bastian Salewsky
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
| | - Ilja Demuth
- 1 Lipid Clinic at the Interdisciplinary Metabolism Center, Charité-Universitätsmedizin Berlin , Berlin, Germany
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4
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Koopal C, Bemelmans R, Marais AD, Visseren FL. Severe hypertriglyceridaemia and pancreatitis in a patient with lipoprotein lipase deficiency based on mutations in lipoprotein lipase (LPL) and apolipoprotein A5 (APOA5) genes. BMJ Case Rep 2019; 12:12/4/e228199. [PMID: 30948399 DOI: 10.1136/bcr-2018-228199] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
A 44-year-old woman was admitted with pancreatitis caused by hypertriglyceridaemia (fasting triglycerides 28 mmol/L). She used oral contraceptives and ezetimibe 10 mg. She was overweight (body mass index 29.7 kg/m2). Diabetes mellitus was ruled out, as were nephrotic syndrome, alcohol abuse, hypothyroidism and dysbetalipoproteinaemia. Genetic analysis revealed mutations in two genes involved in triglyceride metabolism (apolipoprotein A5 and lipoprotein lipase [LPL]). The LPL activity was 45% compared with pooled healthy controls. The post-heparin triglyceride reduction was 6%, compared with a normal reduction of >20%. The patient was initially treated with gemfibrozil, but this was discontinued due to side effects. Dietary triglyceride restriction and discontinuation of the oral contraceptives lowered the plasma triglycerides within 2 weeks to 3.4 mmol/L. Hypertriglyceridaemia is a risk factor for pancreatitis and cardiovascular disease, and has a broad differential diagnosis including genetic causes. Patients can achieve near-normal triglyceride values with a low-fat diet only.
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Affiliation(s)
| | | | - A David Marais
- Division of Chemical Pathology, University of Cape Town Health Science Faculty, Cape Town, South Africa
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5
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Qin YY, Wei AQ, Shan QW, Xian XY, Wu YY, Liao L, Yan J, Lai ZF, Lin FQ. Rare LPL gene missense mutation in an infant with hypertriglyceridemia. J Clin Lab Anal 2018; 32:e22414. [PMID: 29479812 DOI: 10.1002/jcla.22414] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 01/27/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Severe hypertriglyceridemia usually results from a combination of genetic and environmental factors and is most often attributable to mutations in the lipoprotein lipase (LPL) gene. OBJECTIVES The aim of this study was to identify rare mutations in the LPL gene causing severe hypertriglyceridemia. METHODS A Chinese infant who presented classical features of severe hypertriglyceridemia recruited for DNA sequencing of the LPL gene. The pathogenicity grade of the variants was defined based on the prediction of pathogenicity using in silico prediction tools. Review some studies to understand the molecular mechanisms underlying the severe hypertriglyceridemia. RESULTS We identified a rare mutation in the LPL gene causing severe hypertriglyceridemia: a nucleotide substitution (c.836T>G) resulting in a leucine to arginine substitution at position 279 of the protein (p.Leu279Arg).The pathogenicity of the variant was predicted by in silico analysis using PolyPhen2 and SIFT prediction programs, which indicated that mutation p.Leu279Arg is probably harmful. We have also reviewed published studies concerning the molecular mechanisms underlying severe hypertriglyceridemia. A missense mutation in the 6 exon of the LPL gene is reportedly associated with LPL deficiency. CONCLUSIONS We have here identified a rare pathogenic mutation in the LPL gene in a Chinese infant with severe hypertriglyceridemia.
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Affiliation(s)
- Yuan-Yuan Qin
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Ai-Qiu Wei
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Qing-Wen Shan
- Department of pediatric, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Xiao-Ying Xian
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Yang-Yang Wu
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Lin Liao
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Jie Yan
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Zhan-Feng Lai
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Fa-Quan Lin
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, China
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6
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Li JJ, Chen YQ, Fan LL, Jin JY, Guo S, Xiang R. Microduplication of 10q26.3 in a Chinese hypertriglyceridemia patient. Mol Cell Probes 2017; 37:28-31. [PMID: 29129660 DOI: 10.1016/j.mcp.2017.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 11/06/2017] [Accepted: 11/06/2017] [Indexed: 10/18/2022]
Abstract
Hypertriglyceridemia (HTG) plays an important role in the development and progression of atherosclerosis. It is inherited in an autosomal dominant pattern with a frequency of approximately 1:1,000,000 worldwide. Previous study has demonstrated that more than six genes underlie this disorder. In addition, copy number variants (CNVs) including disease-causing genes also play a crucial role in it. In this study, we have employed SNP-ARRAY chip technology to detect the pathogenic CNVs in a HTG patient who carried no meaningful mutations in HTG candidate genes. And we identified a de novo CNV interstitial 134.7 kb duplication of chromosome region 10q26.3 containing CYP2E1. And this CNV also has been confirmed by Real-time PCR. CYP2E1 is a member of cytochrome P450 superfamily of enzymes which play an important role in fatty acid metabolism. Our study is consistent with previous research and further claimes that CNVs containing CYP2E1 may be related to HTG and obesity. Our study not only further confirmes the hypothesis that the CYP2E1 is a plausible candidate gene for HTG, but also may contribute to the diagnosis and treatment of these genomic diseases.
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Affiliation(s)
- Jing-Jing Li
- The State Key Laboratory of Medical Genetics & School of Life Sciences, Central South University, Changsha 410013, China
| | - Ya-Qin Chen
- The Second Xiangya Hospital of Central South University, Changsha 410013, China
| | - Liang-Liang Fan
- The State Key Laboratory of Medical Genetics & School of Life Sciences, Central South University, Changsha 410013, China
| | - Jie-Yuan Jin
- The State Key Laboratory of Medical Genetics & School of Life Sciences, Central South University, Changsha 410013, China
| | - Shuai Guo
- The State Key Laboratory of Medical Genetics & School of Life Sciences, Central South University, Changsha 410013, China
| | - Rong Xiang
- The State Key Laboratory of Medical Genetics & School of Life Sciences, Central South University, Changsha 410013, China; The Second Xiangya Hospital of Central South University, Changsha 410013, China.
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7
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Lun Y, Sun X, Wang P, Chi J, Hou X, Wang Y. Severe hypertriglyceridemia due to two novel loss-of-function lipoprotein lipase gene mutations (C310R/E396V) in a Chinese family associated with recurrent acute pancreatitis. Oncotarget 2017; 8:47741-47754. [PMID: 28548960 PMCID: PMC5564601 DOI: 10.18632/oncotarget.17762] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 04/11/2017] [Indexed: 11/25/2022] Open
Abstract
Lipoprotein lipase (LPL) is widely expressed in skeletal muscles, cardiac muscles as well as adipose tissue and involved in the catabolism of triglyceride. Herein we have systematically characterized two novel loss-of-function mutations in LPL from a Chinese family in which afflicted members were manifested by severe hypertriglyceridemia and recurrent pancreatitis. DNA sequencing revealed that the proband was a heterozygote carrying a novel c.T928C (p.C310R) mutation in exon 6 of the LPL gene. Another member of the family was detected to be a compound heterozygote who along with the c.T928C mutation also carried a novel missense mutation c.A1187T (p.E396V) in exon 8 of the LPL gene. Furthermore, COS-1 cells were transfected with lentiviruses containing the mutant LPL genes. While C310R markedly reduced the overall LPL protein level, COS-1 cells carrying E396V or double mutations contained similar overall LPL protein levels to the wild-type. The specific activity of the LPL mutants remained at comparable magnitude to the wild-type. However, few LPL were detected in the culture medium for the mutants, suggesting that both mutations caused aberrant triglyceride catabolism. More specifically, E396V and double mutations dampened the transport of LPL to the cell surface, while for the C310R mutation, reducing LPL protein level might be involved. By characterizing these two novel LPL mutations, this study has expanded our understanding on the pathogenesis of familial hypertriglyceridemia (FHTG).
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Affiliation(s)
- Yu Lun
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Xiaofang Sun
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Ping Wang
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Jingwei Chi
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Xu Hou
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Yangang Wang
- Department of Endocrinology and Metabolic Diseases, The Affiliated Hospital of Qingdao University, Qingdao, China
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8
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Mysling S, Kristensen KK, Larsson M, Beigneux AP, Gårdsvoll H, Fong LG, Bensadouen A, Jørgensen TJ, Young SG, Ploug M. The acidic domain of the endothelial membrane protein GPIHBP1 stabilizes lipoprotein lipase activity by preventing unfolding of its catalytic domain. eLife 2016; 5:e12095. [PMID: 26725083 PMCID: PMC4755760 DOI: 10.7554/elife.12095] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/02/2016] [Indexed: 12/19/2022] Open
Abstract
GPIHBP1 is a glycolipid-anchored membrane protein of capillary endothelial cells that binds lipoprotein lipase (LPL) within the interstitial space and shuttles it to the capillary lumen. The LPL•GPIHBP1 complex is responsible for margination of triglyceride-rich lipoproteins along capillaries and their lipolytic processing. The current work conceptualizes a model for the GPIHBP1•LPL interaction based on biophysical measurements with hydrogen-deuterium exchange/mass spectrometry, surface plasmon resonance, and zero-length cross-linking. According to this model, GPIHBP1 comprises two functionally distinct domains: (1) an intrinsically disordered acidic N-terminal domain; and (2) a folded C-terminal domain that tethers GPIHBP1 to the cell membrane by glycosylphosphatidylinositol. We demonstrate that these domains serve different roles in regulating the kinetics of LPL binding. Importantly, the acidic domain stabilizes LPL catalytic activity by mitigating the global unfolding of LPL's catalytic domain. This study provides a conceptual framework for understanding intravascular lipolysis and GPIHBP1 and LPL mutations causing familial chylomicronemia. DOI:http://dx.doi.org/10.7554/eLife.12095.001 Fat is an important part of our diet. The intestines absorb fats and package them into particles called lipoproteins. After reaching the bloodstream, the fat molecules (lipids) in the lipoproteins are broken down by an enzyme called lipoprotein lipase (LPL), which is located along the surface of small blood vessels. This releases nutrients that can be used by vital tissues – mainly the heart, skeletal muscle, and adipose tissues. LPL is produced by muscle and adipose tissue, but it is quickly swept up by a protein called GPIHBP1 and shuttled to its site of action inside the blood vessels. Mutations that alter the structure of LPL or GPIHBP1 can prevent the breakdown of lipids, resulting in high levels of lipids in the blood. This can lead to inflammation in the pancreas and also increases the risk of heart attacks and strokes. Many earlier studies have examined the properties of LPL, but our understanding of GPIHBP1 has been limited, mainly because it has been difficult to purify GPIHBP1 for analysis. Using genetically altered insect cells, Mysling et al. were able to purify two different forms of GPIHBP1 – a full-length version and a shorter version that lacked a small section at the end of the molecule known as the acidic domain. This revealed that the opposite end of the molecule – called the carboxyl-terminal domain – is primarily responsible for binding LPL and anchoring it inside blood vessels. Once LPL is bound to GPIHBP1, the acidic domain of GPIHBP1 helps to stabilize LPL. If GPIHBP1’s acidic domain is missing then LPL is more susceptible to losing its structure, rendering it incapable of breaking down the lipids in the blood. Mysling et al. describe a new model for how LPL and GPIHBP1 interact that explains how specific mutations in the genes that encode these proteins interfere with the delivery of LPL to small blood vessels. In the future, this could help researchers to develop new strategies to treat people with high levels of lipids in their blood. DOI:http://dx.doi.org/10.7554/eLife.12095.002
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Affiliation(s)
- Simon Mysling
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.,Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Kristian Kølby Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Mikael Larsson
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Anne P Beigneux
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Henrik Gårdsvoll
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - André Bensadouen
- Division of Nutritional Science, Cornell University, Ithaca, United States
| | - Thomas Jd Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States.,Department of Human Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
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9
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Ariza MJ, Martínez-Hernández PL, Ibarretxe D, Rabacchi C, Rioja J, Grande-Aragón C, Plana N, Tarugi P, Olivecrona G, Calandra S, Valdivielso P. Novel mutations in the GPIHBP1 gene identified in 2 patients with recurrent acute pancreatitis. J Clin Lipidol 2015; 10:92-100.e1. [PMID: 26892125 DOI: 10.1016/j.jacl.2015.09.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 09/09/2015] [Accepted: 09/16/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) has been demonstrated to be essential for the in vivo function of lipoprotein lipase (LPL), the major triglyceride (TG)-hydrolyzing enzyme involved in the intravascular lipolysis of TG-rich lipoproteins. Recently, loss-of-function mutations of GPIHBP1 have been reported as the cause of type I hyperlipoproteinemia in several patients. METHODS Two unrelated patients were referred to our Lipid Units because of a severe hypertriglyceridemia and recurrent pancreatitis. We measured LPL activity in postheparin plasma and serum ApoCII and sequenced LPL, APOC2, and GPIHBP1. RESULTS The 2 patients exhibited very low LPL activity not associated with mutations in LPL gene or with ApoCII deficiency. The sequence of GPIHBP1 revealed 2 novel point mutations. One patient (proband 1) was found to be homozygous for a C>A transversion in exon 3 resulting in the conversion of threonine to lysine at position 80 (p.Thr80Lys). The other patient (proband 2) was found to be homozygous for a G>T transversion in the third base of the ATG translation initiation codon in exon 1, resulting in the conversion of methionine to isoleucine (p.Met1Ile). CONCLUSION In conclusion, we have identified 2 novel GPIHBP1 missense mutations in 2 unrelated patients as the cause of their severe hypertriglyceridemia.
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Affiliation(s)
- María José Ariza
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain.
| | | | - Daiana Ibarretxe
- Vascular Medicine and Metabolism Unit, Research Unit on Lipids and Atherosclerosis, Sant Joan University Hospital, Universitat Rovira i Virgili, IISPV, Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus, Spain
| | - Claudio Rabacchi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - José Rioja
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain
| | | | - Nuria Plana
- Vascular Medicine and Metabolism Unit, Research Unit on Lipids and Atherosclerosis, Sant Joan University Hospital, Universitat Rovira i Virgili, IISPV, Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus, Spain
| | - Patrizia Tarugi
- Department of Life Sciences, University of Modena & Reggio Emilia, Modena, Italy
| | - Gunilla Olivecrona
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Sebastiano Calandra
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena & Reggio Emilia Modena, Italy
| | - Pedro Valdivielso
- Department of Medicine and Dermatology, Lipids and Atherosclerosis Laboratory, CIMES, University of Málaga, Málaga, Spain; Internal Medicine Unit, Virgen de la Victoria University Hospital, Málaga, Spain
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