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Auclair N, Sané AT, Ahmarani L, Ould-Chikh NEH, Patey N, Beaulieu JF, Delvin E, Spahis S, Levy E. High-fat diet reveals the impact of Sar1b defects on lipid and lipoprotein profile and cholesterol metabolism. J Lipid Res 2023; 64:100423. [PMID: 37558128 PMCID: PMC10518719 DOI: 10.1016/j.jlr.2023.100423] [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: 05/05/2023] [Revised: 07/26/2023] [Accepted: 07/28/2023] [Indexed: 08/11/2023] Open
Abstract
Biallelic pathogenic variants of the Sar1b gene cause chylomicron retention disease (CRD) whose central phenotype is the inability to secrete chylomicrons. Patients with CRD experience numerous clinical symptoms such as gastrointestinal, hepatic, neuromuscular, ophthalmic, and cardiological abnormalities. Recently, the production of mice expressing either a targeted deletion or mutation of Sar1b recapitulated biochemical and gastrointestinal defects associated with CRD. The present study was conducted to better understand little-known aspects of Sar1b mutations, including mouse embryonic development, lipid profile, and lipoprotein composition in response to high-fat diet, gut and liver cholesterol metabolism, sex-specific effects, and genotype-phenotype differences. Sar1b deletion and mutation produce a lethal phenotype in homozygous mice, which display intestinal lipid accumulation without any gross morphological abnormalities. On high-fat diet, mutant mice exhibit more marked abnormalities in body composition, adipose tissue and liver weight, plasma cholesterol, non-HDL cholesterol and polyunsaturated fatty acids than those on the regular Chow diet. Divergences were also noted in lipoprotein lipid composition, lipid ratios (serving as indices of particle size) and lipoprotein-apolipoprotein distribution. Sar1b defects significantly reduce gut cholesterol accumulation while altering key players in cholesterol metabolism. Noteworthy, variations were observed between males and females, and between Sar1b deletion and mutation phenotypes. Overall, mutant animal findings reveal the importance of Sar1b in several biochemical, metabolic and developmental processes.
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Affiliation(s)
- Nickolas Auclair
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Pharmacology & Physiology, Université de Montréal, Montreal, Quebec, Canada
| | - Alain T Sané
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Léna Ahmarani
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | | | - Nathalie Patey
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-François Beaulieu
- Laboratory of Intestinal Physiopathology, Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Edgard Delvin
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Schohraya Spahis
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Emile Levy
- Research Center, CHU Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Pharmacology & Physiology, Université de Montréal, Montreal, Quebec, Canada; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada.
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2
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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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Abstract
PURPOSE OF REVIEW Nonalcoholic fatty liver disease (NAFLD) is defined as the abnormal accumulation of lipids in the liver, called hepatic steatosis, which occurs most often as a concomitant of the metabolic syndrome. Its incidence has surged significantly in recent decades concomitant with the obesity pandemic and increasing consumption of refined carbohydrates and saturated fats. This makes a review of the origins of NAFLD timely and relevant. RECENT FINDINGS This disorder, which shares histologic markers found in alcoholic fatty liver disease, was named NAFLD to distinguish it from the latter. Recently, however, the term metabolic-associated fatty liver disease (MAFLD) has been suggested as a refinement of NAFLD that should highlight the central, etiologic role of insulin resistance, obesity, and diabetes mellitus. The complexity of the pathways involved in the regulation of hepatic triglyceride synthesis and utilization have become obvious over the past 10 years, including the recent identification of monogenic causes of metabolic-associated fatty liver disease. These include PNPLA3, transmembrane 6 superfamily member 2, GCKR, membrane-bound O-acyltransferase 7 suggest targets for new therapies for hepatic steatosis. SUMMARY The current review can serve as a guide to the complex pathways involved in the maintenance of hepatic triglyceride levels as well as an introduction to the most recent discoveries, including those of key genes that have provided opportunities for new and novel therapeutics.
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Affiliation(s)
- Leinys S Santos-Baez
- Division of Preventive Medicine and Nutrition, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York, USA
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Auclair N, Sané AT, Ahmarani L, Patey N, Beaulieu JF, Peretti N, Spahis S, Levy E. Sar1b mutant mice recapitulate gastrointestinal abnormalities associated with chylomicron retention disease. J Lipid Res 2021; 62:100085. [PMID: 33964306 PMCID: PMC8175419 DOI: 10.1016/j.jlr.2021.100085] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/15/2021] [Accepted: 04/17/2021] [Indexed: 11/17/2022] Open
Abstract
Chylomicron retention disease (CRD) is an autosomal recessive disorder associated with biallelic Sar1b mutations leading to defects in intracellular chylomicron (CM) trafficking and secretion. To date, a direct cause-effect relationship between CRD and Sar1b mutation has not been established, but genetically modified animal models provide an opportunity to elucidate unrecognized aspects of these mutations. To examine the physiological role and molecular mechanisms of Sar1b function, we generated mice expressing either a targeted deletion or mutation of human Sar1b using the CRISPR-Cas9 system. We found that deletion or mutation of Sar1b in mice resulted in late-gestation lethality of homozygous embryos. Moreover, compared with WT mice, heterozygotes carrying a single disrupted Sar1b allele displayed lower plasma levels of triglycerides, total cholesterol, and HDL-cholesterol, along with reduced CM secretion following gastric lipid gavage. Similarly, decreased expression of apolipoprotein B and microsomal triglyceride transfer protein was observed in correlation with the accumulation of mucosal lipids. Inefficient fat absorption in heterozygotes was confirmed via an increase in fecal lipid excretion. Furthermore, genetically modified Sar1b affected intestinal lipid homeostasis as demonstrated by enhanced fatty acid β-oxidation and diminished lipogenesis through the modulation of transcription factors. This is the first reported mammalian animal model with human Sar1b genetic defects, which reproduces some of the characteristic CRD features and provides a direct cause-effect demonstration.
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Affiliation(s)
- Nickolas Auclair
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Pharmacology & Physiology, Université de Montréal, Montreal, Quebec, Canada
| | - Alain T Sané
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Lena Ahmarani
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Nathalie Patey
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Pathology, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-François Beaulieu
- Laboratory of Intestinal Physiopathology, Department of Immunology and Cell Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Noel Peretti
- Department of Pediatric Gastroenterology-Hepatology and Nutrition, Laboratory INSERM 1060 Cardiovascular Metabolism Endocrinology and Nutrition CarMEN, Lyon, France
| | - Schohraya Spahis
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Emile Levy
- Research Center, CHU Ste-Justine, Université de Montréal, Montreal, Quebec, Canada; Department of Pharmacology & Physiology, Université de Montréal, Montreal, Quebec, Canada; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada.
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Bredefeld C, Peretti N, Hussain MM. New Classification and Management of Abetalipoproteinemia and Related Disorders. Gastroenterology 2021; 160:1912-1916. [PMID: 33275938 DOI: 10.1053/j.gastro.2020.11.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 02/03/2023]
Affiliation(s)
- Cindy Bredefeld
- Department of Medicine, New York University Long Island School of Medicine, NYU Langone Hospital - Long Island, Mineola, New York
| | - Noel Peretti
- Department of Pediatric Gastroenterology-Hepatology and Nutrition, Laboratory INSERM 1060 Cardiovascular Metabolism Endocrinology and Nutrition CarMEN, Lyon, France
| | - M Mahmood Hussain
- Department of Medicine, New York University Long Island School of Medicine, NYU Langone Hospital - Long Island, Mineola, New York
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Efficacy of Polyphenols in the Management of Dyslipidemia: A Focus on Clinical Studies. Nutrients 2021; 13:nu13020672. [PMID: 33669729 PMCID: PMC7922034 DOI: 10.3390/nu13020672] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 02/06/2023] Open
Abstract
Polyphenols (PLPs), phytochemicals found in a wide range of plant-based foods, have gained extensive attention in view of their antioxidant, anti-inflammatory, immunomodulatory and several additional beneficial activities. The health-promoting effects noted in animal models of various non-communicable diseases explain the growing interest in these molecules. In particular, in vitro and animal studies reported an attenuation of lipid disorders in response to PLPs. However, despite promising preclinical investigations, the effectiveness of PLPs in human dyslipidemia (DLP) is less clear and necessitates revision of available literature. Therefore, the present review analyzes the role of PLPs in managing clinical DLP, notably by dissecting their potential in ameliorating lipid/lipoprotein metabolism and alleviating hyperlipidemia, both postprandially and in long-term interventions. To this end, PubMed was used for article search. The search terms included polyphenols, lipids, triglycerides, cholesterol, LDL-cholesterol and /or HDL-cholesterol. The critical examination of the trials published to date illustrates certain benefits on blood lipids along with co-morbidities in participant’s health status. However, inconsistent results document significant research gaps, potentially owing to study heterogeneity and lack of rigor in establishing PLP bioavailability during supplementation. This underlines the need for further efforts in order to elucidate and support a potential role of PLPs in fighting DLP.
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Levy E, Beaulieu JF, Spahis S. From Congenital Disorders of Fat Malabsorption to Understanding Intra-Enterocyte Mechanisms Behind Chylomicron Assembly and Secretion. Front Physiol 2021; 12:629222. [PMID: 33584351 PMCID: PMC7873531 DOI: 10.3389/fphys.2021.629222] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/06/2021] [Indexed: 11/13/2022] Open
Abstract
During the last two decades, a large body of information on the events responsible for intestinal fat digestion and absorption has been accumulated. In particular, many groups have extensively focused on the absorptive phase in order to highlight the critical "players" and the main mechanisms orchestrating the assembly and secretion of chylomicrons (CM) as essential vehicles of alimentary lipids. The major aim of this article is to review understanding derived from basic science and clinical conditions associated with impaired packaging and export of CM. We have particularly insisted on inborn metabolic pathways in humans as well as on genetically modified animal models (recapitulating pathological features). The ultimate goal of this approach is that "experiments of nature" and in vivo model strategy collectively allow gaining novel mechanistic insight and filling the gap between the underlying genetic defect and the apparent clinical phenotype. Thus, uncovering the cause of disease contributes not only to understanding normal physiologic pathway, but also to capturing disorder onset, progression, treatment and prognosis.
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Affiliation(s)
- Emile Levy
- Research Centre, CHU Ste-Justine, Université de Montréal, Montreal, QC, Canada
- Department of Nutrition, Université de Montréal, Montreal, QC, Canada
- Department of Pediatrics, Université de Montréal, Montreal, QC, Canada
| | - Jean François Beaulieu
- Laboratory of Intestinal Physiopathology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Schohraya Spahis
- Research Centre, CHU Ste-Justine, Université de Montréal, Montreal, QC, Canada
- Department of Nutrition, Université de Montréal, Montreal, QC, Canada
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Yarwood R, Hellicar J, Woodman PG, Lowe M. Membrane trafficking in health and disease. Dis Model Mech 2020; 13:13/4/dmm043448. [PMID: 32433026 PMCID: PMC7197876 DOI: 10.1242/dmm.043448] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Membrane trafficking pathways are essential for the viability and growth of cells, and play a major role in the interaction of cells with their environment. In this At a Glance article and accompanying poster, we outline the major cellular trafficking pathways and discuss how defects in the function of the molecular machinery that mediates this transport lead to various diseases in humans. We also briefly discuss possible therapeutic approaches that may be used in the future treatment of trafficking-based disorders. Summary: This At a Glance article and poster summarise the major intracellular membrane trafficking pathways and associated molecular machineries, and describe how defects in these give rise to disease in humans.
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Affiliation(s)
- Rebecca Yarwood
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - John Hellicar
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Philip G Woodman
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Martin Lowe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
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Sané A, Ahmarani L, Delvin E, Auclair N, Spahis S, Levy E. SAR1B GTPase is necessary to protect intestinal cells from disorders of lipid homeostasis, oxidative stress, and inflammation. J Lipid Res 2019; 60:1755-1764. [PMID: 31409740 PMCID: PMC6795079 DOI: 10.1194/jlr.ra119000119] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/29/2019] [Indexed: 12/12/2022] Open
Abstract
Genetic defects in SAR1B GTPase inhibit chylomicron (CM) trafficking to the Golgi and result in a huge intraenterocyte lipid accumulation with a failure to release CMs and liposoluble vitamins into the blood circulation. The central aim of this study is to test the hypothesis that SAR1B deletion (SAR1B−/−) disturbs enterocyte lipid homeostasis (e.g., FA β-oxidation and lipogenesis) while promoting oxidative stress and inflammation. Another issue is to compare the impact of SAR1B−/− to that of its paralogue SAR1A−/− and combined SAR1A−/−/B−/−. To address these critical issues, we have generated Caco-2/15 cells with a knockout of SAR1A, SAR1B, or SAR1A/B genes. SAR1B−/− results in lipid homeostasis disruption, reflected by enhanced mitochondrial FA β-oxidation and diminished lipogenesis in intestinal absorptive cells via the implication of PPARα and PGC1α transcription factors. Additionally, SAR1B−/−cells, which mimicked enterocytes of CM retention disease, spontaneously disclosed inflammatory and oxidative characteristics via the implication of NF-κB and NRF2. In most conditions, SAR1A−/− cells showed a similar trend, albeit less dramatic, but synergetic effects were observed with the combined defects of the two SAR1 paralogues. In conclusion, SAR1B and its paralogue are needed not only for CM trafficking but also for lipid homeostasis, prooxidant/antioxidant balance, and protection against inflammatory processes.
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Affiliation(s)
- Alain Sané
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Lena Ahmarani
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Edgard Delvin
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Nikolas Auclair
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada.,Departments of Pharmacology, Université de Montréal, Montreal, Quebec, Canada
| | - Schohraya Spahis
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada.,Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Emile Levy
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada .,Departments of Pharmacology, Université de Montréal, Montreal, Quebec, Canada.,Nutrition, Université de Montréal, Montreal, Quebec, Canada
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Abstract
PURPOSE OF REVIEW Chylomicron retention disease (CRD) is an autosomic recessive disorder, in which intestinal fat malabsorption is the main cause of diverse severe manifestations. The specific molecular defect was identified in 2003 and consists of mutations in the SAR1B or SARA2 gene encoding for intracellular SAR1B GTPase protein. The aim of this review is first to provide an update of the recent biochemical, genetic and clinical findings, and second to discuss novel mechanisms related to hallmark symptoms. RECENT FINDINGS CRD patients present with SAR1B mutations, which disable the formation of coat protein complex II and thus blocks the transport of chylomicron cargo from the endoplasmic reticulum to the Golgi. Consequently, there is a total absence of chylomicron and apolipoprotein B-48 in the blood circulation following a fat meal, accompanied by a deficiency in liposoluble vitamins and essential fatty acids. The recent discovery of Transport and Golgi organization and Transport and Golgi organization-like proteins may explain the intriguing export of large chylomicron, exceeding coat protein complex II size. Hypocholesterolemia could be accounted for by a decrease in HDL cholesterol, likely a reflection of limited production of intestinal HDL in view of reduced ATP-binding cassette family A protein 1 and apolipoprotein A-I protein. In experimental studies, the paralog SAR1A compensates for the lack of the SAR1B GTPase protein. SUMMARY Molecular testing for CRD is recommended to distinguish the disease from other congenital fat malabsorptions, and to early define molecular aberrations, accelerate treatment, and prevent complications.
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Affiliation(s)
- Emile Levy
- Research Centre
- Gastroenterology, Hepatology and Nutrition Unit, CHU Ste-Justine
- Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Pierre Poinsot
- Gastroenterology, Hepatology and Nutrition Unit, CHU Ste-Justine
| | - Schohraya Spahis
- Research Centre
- Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
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Cuerq C, Henin E, Restier L, Blond E, Drai J, Marçais C, Di Filippo M, Laveille C, Michalski MC, Poinsot P, Caussy C, Sassolas A, Moulin P, Reboul E, Charriere S, Levy E, Lachaux A, Peretti N. Efficacy of two vitamin E formulations in patients with abetalipoproteinemia and chylomicron retention disease. J Lipid Res 2018; 59:1640-1648. [PMID: 30021760 DOI: 10.1194/jlr.m085043] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 07/17/2018] [Indexed: 02/07/2023] Open
Abstract
Abetalipoproteinemia (ABL) and chylomicron retention disease (CMRD) are extremely rare recessive forms of hypobetalipoproteinemia characterized by intestinal lipid malabsorption and severe vitamin E deficiency. Vitamin E is often supplemented in the form of fat-soluble vitamin E acetate, but fat malabsorption considerably limits correction of the deficiency. In this crossover study, we administered two different forms of vitamin E, tocofersolan (a water-soluble derivative of RRR-α-tocopherol) and α-tocopherol acetate, to three patients with ABL and four patients with CMRD. The aims of this study were to evaluate the intestinal absorption characteristics of tocofersolan versus α-tocopherol acetate by measuring the plasma concentrations of α-tocopherol over time after a single oral load and to compare efficacy by evaluating the ability of each formulation to restore vitamin E storage after 4 months of treatment. In patients with ABL, tocofersolan and α-tocopherol acetate bioavailabilities were extremely low (2.8% and 3.1%, respectively). In contrast, bioavailabilities were higher in patients with CMRD (tocofersolan, 24.7%; α-tocopherol acetate, 11.4%). Plasma concentrations of α-tocopherol at 4 months were not significantly different by formulation type in ABL or CMRD. This study provides new insights about vitamin E status in ABL and CMRD and suggests the potential of different formulations as treatment options.
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Affiliation(s)
- Charlotte Cuerq
- Biochemistry Department, Lyon Sud Hospital, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France
| | | | - Lioara Restier
- Pediatric Hepato-Gastroenterology and Nutrition Unit, Hôpital Femme Mère Enfant de Lyon, Dyslipidemia Unity Hospices Civils de Lyon, Lyon, Bron, France
| | - Emilie Blond
- Biochemistry Department, Lyon Sud Hospital, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France
| | - Jocelyne Drai
- Biochemistry Department, Lyon Sud Hospital, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France
| | - Christophe Marçais
- Biochemistry Department, Lyon Sud Hospital, Hospices Civils de Lyon, Lyon, France; INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France
| | - Mathilde Di Filippo
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Department of Biochemistry and Molecular Biology, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, Lyon, Bron, France
| | | | | | - Pierre Poinsot
- Pediatric Hepato-Gastroenterology and Nutrition Unit, Hôpital Femme Mère Enfant de Lyon, Dyslipidemia Unity Hospices Civils de Lyon, Lyon, Bron, France
| | - Cyrielle Caussy
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France
| | - Agnès Sassolas
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Department of Biochemistry and Molecular Biology, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, Lyon, Bron, France
| | - Philippe Moulin
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Fédération d'Endocrinologie, Maladies Métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Lyon, Bron, France
| | | | - Sybil Charriere
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Fédération d'Endocrinologie, Maladies Métaboliques, Diabète et Nutrition, Hôpital Louis Pradel, Hospices Civils de Lyon, Lyon, Bron, France
| | - Emile Levy
- Research Centre, CHU Sainte-Justine, and Department of Nutrition, Université de Montréal, Montréal, Québec, Canada
| | - Alain Lachaux
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Pediatric Hepato-Gastroenterology and Nutrition Unit, Hôpital Femme Mère Enfant de Lyon, Dyslipidemia Unity Hospices Civils de Lyon, Lyon, Bron, France
| | - Noël Peretti
- INSERM U1060, INRA UMR 1397, INSA-Lyon, CarMeN Laboratory, Université Lyon 1, Lyon, France; Pediatric Hepato-Gastroenterology and Nutrition Unit, Hôpital Femme Mère Enfant de Lyon, Dyslipidemia Unity Hospices Civils de Lyon, Lyon, Bron, France.
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Sané AT, Seidman E, Peretti N, Kleme ML, Delvin E, Deslandres C, Garofalo C, Spahis S, Levy E. Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene Disruption: Insight From Cell Culture. Arterioscler Thromb Vasc Biol 2017; 37:2243-2251. [PMID: 28982670 DOI: 10.1161/atvbaha.117.310121] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 09/21/2017] [Indexed: 01/28/2023]
Abstract
BACKGROUND Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the critical proteins governing chylomicron secretion by the small intestine, and its mutations lead to chylomicron retention disease, despite the presence of Sar1A paralog. OBJECTIVE The central aim of this work is to examine the cause-effect relationship between Sar1B expression and chylomicron output and to determine whether Sar1B is obligatory for normal high-density lipoprotein biogenesis. APPROACH AND RESULTS The SAR1B gene was totally silenced in Caco-2/15 cells using the zinc finger nuclease technique. SAR1B deletion resulted in significantly decreased secretion of triglycerides (≈40%), apolipoprotein B-48 (≈57%), and chylomicron (≈34.5%). The absence of expected chylomicron production collapse may be because of the compensatory SAR1A elevation observed in our experiments. Therefore, a double knockout of SAR1A and SAR1B was engineered in Caco-2/15 cells, which led to almost complete inhibition of triglycerides, apolipoprotein B-48, and chylomicron output. Further experiments with labeled cholesterol revealed the downregulation of high-density lipoprotein biogenesis in cells deficient in SAR1B or with the double knockout of the 2 SAR1 paralogs. Similarly, there was a fall in the movement of labeled cholesterol from cells to basolateral medium containing apolipoprotein A-I, thereby limiting newly synthesized high-density lipoprotein in genetically modified cells. The decreased cholesterol efflux was associated with impaired expression of ABCA1 (ATP-binding cassette subfamily A member 1). CONCLUSIONS These findings demonstrate that the deletion of the 2 SAR1 isoforms is required to fully eliminate the secretion of chylomicron in vitro. They also underscore the limited high-density lipoprotein production by the intestinal cells in response to SAR1 knockout.
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Affiliation(s)
- Alain Théophile Sané
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Ernest Seidman
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Noel Peretti
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Marie Laure Kleme
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Edgard Delvin
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Colette Deslandres
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Carole Garofalo
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Schohraya Spahis
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.)
| | - Emile Levy
- From the CHU Sainte-Justine Research Centre (A.T.S., M.L.K., E.D., C.D., C.G., S.S., E.L.), Department of Nutrition (M.L.K., S.S., E.L.), and Department of Pediatrics (C.D.), Université de Montréal, Quebec, Canada; Division of Gastroenterology, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada (E.S.); and Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Université de Lyon 1, France (N.P.).
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13
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Sané A, Seidman E, Spahis S, Lamantia V, Garofalo C, Montoudis A, Marcil V, Levy E. New Insights In Intestinal Sar1B GTPase Regulation and Role in Cholesterol Homeostasis. J Cell Biochem 2016; 116:2270-82. [PMID: 25826777 DOI: 10.1002/jcb.25177] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 03/25/2015] [Indexed: 12/12/2022]
Abstract
Sar1B GTPase is a key component of Coat protein complex II (COPII)-coated vesicles that bud from the endoplasmic reticulum to export newly synthesized proteins. The aims of this study were to determine whether Sar1B responds to lipid regulation and to evaluate its role in cholesterol (CHOL) homeostasis. The influence of lipids on Sar1B protein expression was analyzed in Caco-2/15 cells by Western blot. Our results showed that the presence of CHOL (200 μM) and oleic acid (0.5 mM), bound to albumin, increases Sar1B protein expression. Similarly, supplementation of the medium with micelles composed of taurocholate with monooleylglycerol or oleic acid also stimulated Sar1B expression, but the addition of CHOL (200 μM) to micelle content did not modify its regulation. On the other hand, overexpression of Sar1B impacted on CHOL transport and metabolism in view of the reduced cellular CHOL content along with elevated secretion when incubated with oleic acid-containing micelles for 24 h, thereby disclosing induced CHOL transport. This was accompanied with higher secretion of free- and esterified-CHOL within chylomicrons, which was not the case when oleic acid was replaced with monooleylglycerol or when albumin-bound CHOL was given alone. The aforementioned cellular CHOL depletion was accompanied with a low phosphorylated/non phosphorylated HMG-CoA reductase ratio, indicating elevated enzymatic activity. Combination of Sar1B overexpression with micelle incubation led to reduction in intestinal CHOL transporters (NPC1L1, SR-BI) and metabolic regulators (PCSK9 and LDLR). The present work showed that Sar1B is regulated in a time- and concentration-dependent manner by dietary lipids, suggesting an adaptation to alimentary lipid flux. Our data also suggest that Sar1B overexpression contributes to regulation of CHOL transport and metabolism by facilitating rapid uptake and transport of CHOL.
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Affiliation(s)
- Alain Sané
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5
| | - Ernest Seidman
- Research Institute, McGill University, Campus MGH, C10.148.6, Montreal, Quebec, Canada, H3G 1A4
| | - Schohraya Spahis
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada, H3T 1A8
| | - Valérie Lamantia
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5
| | - Carole Garofalo
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5
| | - Alain Montoudis
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5
| | - Valérie Marcil
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5.,Research Institute, McGill University, Campus MGH, C10.148.6, Montreal, Quebec, Canada, H3G 1A4
| | - Emile Levy
- Research Centre, CHU-Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada, H3T 1A8
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14
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Morita SY. Metabolism and Modification of Apolipoprotein B-Containing Lipoproteins Involved in Dyslipidemia and Atherosclerosis. Biol Pharm Bull 2016; 39:1-24. [DOI: 10.1248/bpb.b15-00716] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Shin-ya Morita
- Department of Pharmacy, Shiga University of Medical Science Hospital
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15
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Animal model of Sar1b deficiency presents lipid absorption deficits similar to Anderson disease. J Mol Med (Berl) 2015; 93:165-76. [PMID: 25559265 DOI: 10.1007/s00109-014-1247-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 11/19/2014] [Accepted: 12/18/2014] [Indexed: 01/25/2023]
Abstract
Anderson disease (ANDD) or chylomicron retention disease (CMRD) is a rare, hereditary lipid malabsorption syndrome associated with mutations in the SAR1B gene that is characterized by failure to thrive and hypocholesterolemia. Although the SAR1B structure has been resolved and its role in formation of coat protein II (COPII)-coated carriers is well established, little is known about the requirement for SAR1B during embryogenesis. To address this question, we have developed a zebrafish model of Sar1b deficiency based on antisense oligonucleotide knockdown. We show that zebrafish sar1b is highly conserved among vertebrates; broadly expressed during development; and enriched in the digestive tract organs, brain, and craniofacial skeleton. Consistent with ANDD symptoms of chylomicron retention, we found that dietary lipids in Sar1b-deficient embryos accumulate in enterocytes. Transgenic expression analysis revealed that Sar1b is required for growth of exocrine pancreas and liver. Furthermore, we found abnormal differentiation and maturation of craniofacial cartilage associated with defects in procollagen II secretion and absence of select, neuroD-positive neurons of the midbrain and hindbrain. The model presented here will help to systematically dissect developmental roles of Sar1b and to discover molecular and cellular mechanisms leading to organ-specific ANDD pathology. Key messages: Sar1b depletion phenotype in zebrafish resembles Anderson disease deficits. Sar1b deficiency results in multi-organ developmental deficits. Sar1b is required for dietary cholesterol uptake into enterocytes.
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16
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Mouzaki M, Vresk L, Gonska T. An infant with vomiting, diarrhea, and failure to thrive. Chylomicron retention disease. Gastroenterology 2014; 146:912, 1137-8. [PMID: 24560855 DOI: 10.1053/j.gastro.2013.11.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 11/25/2013] [Indexed: 12/02/2022]
Affiliation(s)
- Marialena Mouzaki
- Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Laura Vresk
- Department of Dietetics, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Tanja Gonska
- Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
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17
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Levy E, Spahis S, Garofalo C, Marcil V, Montoudis A, Sinnet D, Sanchez R, Peretti N, Beaulieu JF, Sane A. Sar1b transgenic male mice are more susceptible to high-fat diet-induced obesity, insulin insensitivity and intestinal chylomicron overproduction. J Nutr Biochem 2014; 25:540-8. [PMID: 24657056 DOI: 10.1016/j.jnutbio.2014.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 12/28/2013] [Accepted: 01/08/2014] [Indexed: 12/13/2022]
Abstract
In the intracellular secretory network, nascent proteins are shuttled from the endoplasmic reticulum to the Golgi by transport vesicles requiring Sar1b, a small GTPase. Mutations in this key enzyme impair intestinal lipid transport and cause chylomicron retention disease. The main aim of this study was to assess whether Sar1b overexpression under a hypercaloric diet accelerated lipid production and chylomicron (CM) secretion, thereby inducing cardiometabolic abnormalities. To this end, we generated transgenic mice overexpressing human Sar1b (Sar1b(+/+)) using pBROAD3-mcs that features the ubiquitous mouse ROSA26 promoter. In response to a high-fat diet (HFD), Sar1b(+/+) mice displayed significantly increased body weight and adiposity compared with Sar1b(+/+) mice under the same regimen or with wild-type (WT) mice exposed to chow diet or HFD. Furthermore, Sar1b(+/+) mice were prone to liver steatosis as revealed by significantly elevated hepatic triglycerides (TG) and cholesterol in comparison with WT animals. They also exhibited augmented levels of plasma TG along with alterations in fatty acid composition. Concomitantly, they showed susceptibility to develop insulin insensitivity and they responded abnormally to oral glucose tolerance test. Finally, Sar1b(+/+) mice that have been treated with Triton WR-1330 (to inhibit TG catabolism) and orotic acid (to block secretion of very low-density lipoprotein by the liver) responded more efficiently to fat meal tests as reflected by the rise in plasma TG and CM concentrations, indicating exaggerated intestinal fat absorption. These results suggest that Sar1b(+/+) under HFD can elicit cardiometabolic traits as revealed by incremental weight gain, fat deposition, dyslipidemia, hepatic steatosis, insulin insensitivity and intestinal fat absorption.
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Affiliation(s)
- Emile Levy
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada, H3T 1J4; Canadian Institutes for Health Research Team on the Digestive Epithelium, Department of Anatomy and Cellular Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada, J1H 5N4.
| | - Schohraya Spahis
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5; Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada, H3T 1J4
| | - Carole Garofalo
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5
| | - Valérie Marcil
- Research Institute, McGill University, Montreal, Quebec, Canada, H3G 1A4
| | - Alain Montoudis
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5
| | - Daniel Sinnet
- Department of Pediatrics, Université de Montréal, Montreal, Quebec, Canada, H3T 1C5
| | - Rocio Sanchez
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5
| | - Noel Peretti
- Centre de recherche Rhône-Alpes en nutrition humaine, Hôpital Edouard-Herriot, Faculté de Médicine, Université de Lyon-1, France
| | - Jean-François Beaulieu
- Canadian Institutes for Health Research Team on the Digestive Epithelium, Department of Anatomy and Cellular Biology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada, J1H 5N4
| | - Alain Sane
- Research Center, Sainte-Justine UHC, Montreal, Quebec, Canada, H3T 1C5
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Seixas E, Barros M, Seabra MC, Barral DC. Rab and Arf proteins in genetic diseases. Traffic 2013; 14:871-85. [PMID: 23565987 DOI: 10.1111/tra.12072] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 04/03/2013] [Accepted: 04/08/2013] [Indexed: 01/29/2023]
Abstract
Rab and ADP-ribosylation factor (Arf) family proteins are master regulators of membrane trafficking and are involved in all steps of vesicular transport. These families of small guanine-nucleotide-binding (G) proteins are well suited to regulate membrane trafficking processes since their nucleotide state determines their conformation and the capacity to bind to a multitude of effectors, which mediate their functions. In recent years, several inherited diseases have been associated with mutations in genes encoding proteins belonging to these two families or in proteins that regulate their GTP-binding cycle. The genetic diseases that are caused by defects in Rabs, Arfs or their regulatory proteins are heterogeneous and display diverse symptoms. However, these diseases mainly affect two types of subcellular compartments, namely lysosome-related organelles and cilia. Also, several of these diseases affect the nervous system. Thus, the study of these diseases represents an opportunity to understand their etiology and the molecular mechanisms involved, as well as to develop novel therapeutic strategies.
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Affiliation(s)
- Elsa Seixas
- CEDOC, Faculdade de Ciências Médicas, FCM, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
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Russo R, Esposito MR, Iolascon A. Inherited hematological disorders due to defects in coat protein (COP)II complex. Am J Hematol 2013; 88:135-40. [PMID: 22764119 DOI: 10.1002/ajh.23292] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 05/28/2012] [Accepted: 06/07/2012] [Indexed: 11/10/2022]
Abstract
Many diseases attributed to trafficking defects are primary disorders of protein folding and assembly. However, an increasing number of disease states are directly attributable to defects in trafficking machinery. In this context, the cytoplasmic coat protein (COP)II complex plays a pivotal role: it mediates the anterograde transport of correctly folded secretory cargo from the endoplasmic reticulum towards the Golgi apparatus. This review attempts to describe the involvement of COPII complex alteration in the pathogenesis of human genetic disorders; particularly, we will focus on two disorders, the Congenital Dyserythropoietic Anemia type II and the Combined Deficiency of Factor V and VIII.
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Affiliation(s)
- Roberta Russo
- CEINGE Biotecnologie Avanzate; University Federico II of Naples; Naples; Italy
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20
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Ouguerram K, Zaïr Y, Kasbi-Chadli F, Nazih H, Bligny D, Schmitz J, Aparicio T, Chétiveaux M, Magot T, Aggerbeck LP, Samson-Bouma ME, Krempf M. Low rate of production of apolipoproteins B100 and AI in 2 patients with Anderson disease (chylomicron retention disease). Arterioscler Thromb Vasc Biol 2012; 32:1520-5. [PMID: 22441101 DOI: 10.1161/atvbaha.112.245076] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Anderson disease is a rare inherited lipid malabsorption syndrome associated with hypocholesterolemia and linked to SAR1B mutations. The aim of this article was to analyze the mechanisms responsible for the low plasma apolipoprotein Apo-B100 and Apo-AI in 2 patients with Anderson disease. METHODS AND RESULTS A primed constant infusion of (13)C-leucine was administered for 14 hours to determine the kinetics of lipoproteins. In the 2 patients, total cholesterol (77 and 85 mg/dL versus 155±32 mg/dL), triglycerides (36 and 59 versus 82±24 mg/dL), Apo-B100 (48 and 43 versus 71±5 mg/dL), and Apo-AI (47 and 62 versus 130±7 mg/dL) were lower compared with 6 healthy individuals. Very-low-density lipoprotein-B100 production rate of the patients was lower (4.08 and 5.52 mg/kg/day versus 12.96±2.88 mg/kg/day) as was the fractional catabolic rate (5.04 and 4.32 day(-1) versus 12.24±3.84 day(-1)). No difference was observed in intermediate-density lipoprotein-B100 and LDL-B100 kinetic data. The production rate of high-density lipoprotein Apo-AI was lower in the patients (7.92 and 8.64 versus 11.96±1.92 mg/kg/day) and the fractional catabolic rate was higher (0.38 and 0.29 versus 0.22±0.01 day(-1)). CONCLUSIONS The low plasma Apo-B100 and Apo-AI concentrations in the patients with Anderson disease were mainly related to low rates of production.
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Affiliation(s)
- Khadija Ouguerram
- INSERM UMR 1087/CNRS UMR 6291 and CRNH Nantes, IRT-UN, Nantes, France
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Siddiqi S, Mansbach CM. Phosphorylation of Sar1b protein releases liver fatty acid-binding protein from multiprotein complex in intestinal cytosol enabling it to bind to endoplasmic reticulum (ER) and bud the pre-chylomicron transport vesicle. J Biol Chem 2012; 287:10178-10188. [PMID: 22303004 DOI: 10.1074/jbc.m111.327247] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Native cytosol requires ATP to initiate the budding of the pre-chylomicron transport vesicle from intestinal endoplasmic reticulum (ER). When FABP1 alone is used, no ATP is needed. Here, we test the hypothesis that in native cytosol FABP1 is present in a multiprotein complex that prevents FABP1 binding to the ER unless the complex is phosphorylated. We found on chromatography of native intestinal cytosol over a Sephacryl S-100 HR column that FABP1 (14 kDa) eluted in a volume suggesting a 75-kDa protein complex that contained four proteins on an anti-FABP1 antibody pulldown. The FABP1-containing column fractions were chromatographed over an anti-FABP1 antibody adsorption column. Proteins co-eluted from the column were identified as FABP1, Sar1b, Sec13, and small VCP/p97-interactive protein by immunoblot, LC-MS/MS, and MALDI-TOF. The four proteins of the complex had a total mass of 77 kDa and migrated on native PAGE at 75 kDa. When the complex was incubated with intestinal ER, there was no increase in FABP1-ER binding. However, when the complex member Sar1b was phosphorylated by PKCζ and ATP, the complex completely disassembled into its component proteins that migrated at their monomer molecular weight on native PAGE. FABP1, freed from the complex, was now able to bind to intestinal ER and generate the pre-chylomicron transport vesicle (PCTV). No increase in ER binding or PCTV generation was observed in the absence of PKCζ or ATP. We conclude that phosphorylation of Sar1b disrupts the FABP1-containing four-membered 75-kDa protein complex in cytosol enabling it to bind to the ER and generate PCTV.
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Affiliation(s)
- Shahzad Siddiqi
- Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163 and
| | - Charles M Mansbach
- Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163 and; Veterans Affairs Medical Center, Memphis, Tennessee 38104.
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22
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Levy E, Harmel E, Laville M, Sanchez R, Emonnot L, Sinnett D, Ziv E, Delvin E, Couture P, Marcil V, Sane AT. Expression of Sar1b enhances chylomicron assembly and key components of the coat protein complex II system driving vesicle budding. Arterioscler Thromb Vasc Biol 2012; 31:2692-9. [PMID: 21836065 DOI: 10.1161/atvbaha.111.233908] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE SAR1b plays a significant role in the assembly, organization, and function of the coat protein complex II, a critical complex for the transport of proteins from the endoplasmic reticulum to the Golgi. Recently, mutations in SARA2 have been associated with lipid absorption disorders. However, functional studies on Sar1b-mediated lipid synthesis pathways and lipoprotein packaging have not been performed. METHODS AND RESULTS Sar1b was overexpressed in Caco-2/15 cells and resulted in significantly augmented triacylglycerol, cholesteryl ester, and phospholipid esterification and secretion and markedly enhanced chylomicron production. It also stimulated monoacylglycerol acyltransferase/diacylglycerol acyltransferase activity and enhanced apolipoprotein B-48 protein synthesis, as well as elevated microsomal triglyceride transfer protein activity. Along with the enhanced chylomicrons, microsomes were characterized by abundant Sec12, the guanine exchange factor that promotes the localization of Sar1b in the endoplasmic reticulum. Furthermore, coimmunoprecipitation experiments revealed high levels of the complex components Sec23/Sec24 and p125, the Sec23-interacting protein. Finally, a pronounced interaction of Sec23/Sec24 with sterol regulatory element binding protein (SREBP) cleavage-activating protein and SREBP-1c was noted, thereby permitting the transfer of the transcription factor SREBP-1c to the nucleus for the activation of genes involved in lipid metabolism. CONCLUSION Our data suggest that Sar1b expression may promote intestinal lipid transport with the involvement of the coat protein complex II network and the processing of SREBP-1c.
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Affiliation(s)
- Emile Levy
- Research Centre, Mother and Child University Hospital Center, Sainte-Justine, Montreal, Quebec, Canada.
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Yáñez JA, Wang SW, Knemeyer IW, Wirth MA, Alton KB. Intestinal lymphatic transport for drug delivery. Adv Drug Deliv Rev 2011; 63:923-42. [PMID: 21689702 PMCID: PMC7126116 DOI: 10.1016/j.addr.2011.05.019] [Citation(s) in RCA: 167] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 10/15/2010] [Accepted: 01/26/2011] [Indexed: 12/16/2022]
Abstract
Intestinal lymphatic transport has been shown to be an absorptive pathway following oral administration of lipids and an increasing number of lipophilic drugs, which once absorbed, diffuse across the intestinal enterocyte and while in transit associate with secretable enterocyte lipoproteins. The chylomicron-associated drug is then secreted from the enterocyte into the lymphatic circulation, rather than the portal circulation, thus avoiding the metabolically-active liver, but still ultimately returning to the systemic circulation. Because of this parallel and potentially alternative absorptive pathway, first-pass metabolism can be reduced while increasing lymphatic drug exposure, which opens the potential for novel therapeutic modalities and allows the implementation of lipid-based drug delivery systems. This review discusses the physiological features of the lymphatics, enterocyte uptake and metabolism, links between drug transport and lipid digestion/re-acylation, experimental model (in vivo, in vitro, and in silico) of lymphatic transport, and the design of lipid- or prodrug-based drug delivery systems for enhancing lymphatic drug transport.
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Calandra S, Tarugi P, Speedy HE, Dean AF, Bertolini S, Shoulders CC. Mechanisms and genetic determinants regulating sterol absorption, circulating LDL levels, and sterol elimination: implications for classification and disease risk. J Lipid Res 2011; 52:1885-926. [PMID: 21862702 DOI: 10.1194/jlr.r017855] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
This review integrates historical biochemical and modern genetic findings that underpin our understanding of the low-density lipoprotein (LDL) dyslipidemias that bear on human disease. These range from life-threatening conditions of infancy through severe coronary heart disease of young adulthood, to indolent disorders of middle- and old-age. We particularly focus on the biological aspects of those gene mutations and variants that impact on sterol absorption and hepatobiliary excretion via specific membrane transporter systems (NPC1L1, ABCG5/8); the incorporation of dietary sterols (MTP) and of de novo synthesized lipids (HMGCR, TRIB1) into apoB-containing lipoproteins (APOB) and their release into the circulation (ANGPTL3, SARA2, SORT1); and receptor-mediated uptake of LDL and of intestinal and hepatic-derived lipoprotein remnants (LDLR, APOB, APOE, LDLRAP1, PCSK9, IDOL). The insights gained from integrating the wealth of genetic data with biological processes have important implications for the classification of clinical and presymptomatic diagnoses of traditional LDL dyslipidemias, sitosterolemia, and newly emerging phenotypes, as well as their management through both nutritional and pharmaceutical means.
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Affiliation(s)
- Sebastiano Calandra
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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Kindel T, Lee DM, Tso P. The mechanism of the formation and secretion of chylomicrons. ATHEROSCLEROSIS SUPP 2011; 11:11-6. [PMID: 20493784 DOI: 10.1016/j.atherosclerosissup.2010.03.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 03/22/2010] [Indexed: 12/17/2022]
Abstract
The purpose of this review is to update the reader on our current understanding of the uptake and secretion of dietary lipid by the enterocyte to the periphery. This is a multi-stage process that first involves luminal digestion, followed by cellular uptake and processing, and subsequent extracellular transport of chylomicrons. We discuss the importance of acid and pancreatic lipase in lipid digestion. Micellar solubilization of fatty acids and 2-mono-acyl glycerol is critical to uptake by enhancing enterocyte exposure. There is controversy regarding the mechanism of fatty acid uptake by the enterocyte and whether this is mediated by a carrier-dependent process. The mechanism of fatty acid transport to the endoplasmic reticulum is discussed including the role of fatty acid binding proteins. Intracellularly, 2-monoacylglycerol and fatty acid are reconstituted to form triacylglycerol by the action of MGAT and DGAT. We focus on the mechanisms of intracellular chylomicron formation and secretion into lymph. Chylomicron and VLDL particles differ not only by an operational definition but likely represent two distinct pathways of intestinal lipoprotein formation. The physiologic role of apo B-48 in the intestine is presented as well as clinical disease of chylomicron metabolism, specifically abetalipoproteinemia and Anderson's disease.
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Affiliation(s)
- Tammy Kindel
- University of Cincinnati College of Medicine, United States
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Georges A, Bonneau J, Bonnefont-Rousselot D, Champigneulle J, Rabès JP, Abifadel M, Aparicio T, Guenedet JC, Bruckert E, Boileau C, Morali A, Varret M, Aggerbeck LP, Samson-Bouma ME. Molecular analysis and intestinal expression of SAR1 genes and proteins in Anderson's disease (Chylomicron retention disease). Orphanet J Rare Dis 2011; 6:1. [PMID: 21235735 PMCID: PMC3029219 DOI: 10.1186/1750-1172-6-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 01/14/2011] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Anderson's disease (AD) or chylomicron retention disease (CMRD) is a very rare hereditary lipid malabsorption syndrome. In order to discover novel mutations in the SAR1B gene and to evaluate the expression, as compared to healthy subjects, of the Sar1 gene and protein paralogues in the intestine, we investigated three previously undescribed individuals with the disease. METHODS The SAR1B, SAR1A and PCSK9 genes were sequenced. The expression of the SAR1B and SAR1A genes in intestinal biopsies of both normal individuals and patients was measured by RTqPCR. Immunohistochemistry using antibodies to recombinant Sar1 protein was used to evaluate the expression and localization of the Sar1 paralogues in the duodenal biopsies. RESULTS Two patients had a novel SAR1B mutation (p.Asp48ThrfsX17). The third patient, who had a previously described SAR1B mutation (p.Leu28ArgfsX7), also had a p.Leu21dup variant of the PCSK9 gene. The expression of the SAR1B gene in duodenal biopsies from an AD/CMRD patient was significantly decreased whereas the expression of the SAR1A gene was significantly increased, as compared to healthy individuals. The Sar1 proteins were present in decreased amounts in enterocytes in duodenal biopsies from the patients as compared to those from healthy subjects. CONCLUSIONS Although the proteins encoded by the SAR1A and SAR1B genes are 90% identical, the increased expression of the SAR1A gene in AD/CMRD does not appear to compensate for the lack of the SAR1B protein. The PCSK9 variant, although reported to be associated with low levels of cholesterol, does not appear to exert any additional effect in this patient. The results provide further insight into the tissue-specific nature of AD/CMRD.
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Affiliation(s)
- Amandine Georges
- Service de Médecine Infantile 3 et Génétique Clinique, INSERM U954, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Jessica Bonneau
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | - Dominique Bonnefont-Rousselot
- UF de Biochimie des Maladies Métaboliques, Service de Biochimie Métabolique, Groupe Hospitalier Pitié-Salpêtrière (AP-HP), and Département de Biologie Expérimentale, Métabolique et Clinique, EA 4466, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, 75013, France
| | - Jacqueline Champigneulle
- Laboratoire d'Anatomie et de Cytologie Pathologiques, Hôpital de Brabois, Université Paris 13, Bobigny, 93000, France
| | - Jean P Rabès
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
- Service de Biochimie et Génétique Moléculaire, CHU A Paré, AP-HP et Faculté de Médecine (PIFO-UVSQ), Boulogne, 92104, France
| | - Marianne Abifadel
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | - Thomas Aparicio
- Service de Gastroentérologie, Hôpital Avicenne, 125 rue de Stalingrad, Université Paris 13, Bobigny, 93000, France
| | - Jean C Guenedet
- Laboratoire d'Anatomie et de Cytologie Pathologiques, Hôpital de Brabois, Université Paris 13, Bobigny, 93000, France
- Service de Microscopie Electronique, Hôpital de Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Eric Bruckert
- Service d'Endocrinologie-Métabolisme, Hôpital Pitié Salpêtrière, (AP-HP), Paris, 75013, France
| | - Catherine Boileau
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
- Service de Biochimie et Génétique Moléculaire, CHU A Paré, AP-HP et Faculté de Médecine (PIFO-UVSQ), Boulogne, 92104, France
| | - Alain Morali
- Service de Médecine Infantile 3 et Génétique Clinique, INSERM U954, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Mathilde Varret
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | | | - Marie E Samson-Bouma
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
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Peretti N, Sassolas A, Roy CC, Deslandres C, Charcosset M, Castagnetti J, Pugnet-Chardon L, Moulin P, Labarge S, Bouthillier L, Lachaux A, Levy E. Guidelines for the diagnosis and management of chylomicron retention disease based on a review of the literature and the experience of two centers. Orphanet J Rare Dis 2010; 5:24. [PMID: 20920215 PMCID: PMC2956717 DOI: 10.1186/1750-1172-5-24] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 09/29/2010] [Indexed: 02/06/2023] Open
Abstract
Familial hypocholesterolemia, namely abetalipoproteinemia, hypobetalipoproteinemia and chylomicron retention disease (CRD), are rare genetic diseases that cause malnutrition, failure to thrive, growth failure and vitamin E deficiency, as well as other complications. Recently, the gene implicated in CRD was identified. The diagnosis is often delayed because symptoms are nonspecific. Treatment and follow-up remain poorly defined. The aim of this paper is to provide guidelines for the diagnosis, treatment and follow-up of children with CRD based on a literature overview and two pediatric centers 'experience. The diagnosis is based on a history of chronic diarrhea with fat malabsorption and abnormal lipid profile. Upper endoscopy and histology reveal fat-laden enterocytes whereas vitamin E deficiency is invariably present. Creatine kinase (CK) is usually elevated and hepatic steatosis is common. Genotyping identifies the Sar1b gene mutation. Treatment should be aimed at preventing potential complications. Vomiting, diarrhea and abdominal distension improve on a low-long chain fat diet. Failure to thrive is one of the most common initial clinical findings. Neurological and ophthalmologic complications in CRD are less severe than in other types of familial hypocholesterolemia. However, the vitamin E deficiency status plays a pivotal role in preventing neurological complications. Essential fatty acid (EFA) deficiency is especially severe early in life. Recently, increased CK levels and cardiomyopathy have been described in addition to muscular manifestations. Poor mineralization and delayed bone maturation do occur. A moderate degree of macrovesicular steatosis is common, but no cases of steatohepatitis cirrhosis. Besides a low-long chain fat diet made up uniquely of polyunsaturated fatty acids, treatment includes fat-soluble vitamin supplements and large amounts of vitamin E. Despite fat malabsorption and the absence of postprandial chylomicrons, the oral route can prevent neurological complications even though serum levels of vitamin E remain chronically low. Dietary counseling is needed not only to monitor fat intake and improve symptoms, but also to maintain sufficient caloric and EFA intake. Despite a better understanding of the pathogenesis of CRD, the diagnosis and management of the disease remain a challenge for clinicians. The clinical guidelines proposed will helpfully lead to an earlier diagnosis and the prevention of complications.
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Affiliation(s)
- Noel Peretti
- Department of Nutrition, CHU Sainte-Justine Research Center, Université de Montréal, 3175, Ste-Catherine Road, Montreal, Quebec, H3T 1C5, Canada
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Cefalù AB, Calvo PL, Noto D, Baldi M, Valenti V, Lerro P, Tramuto F, Lezo A, Morra I, Cenacchi G, Barbera C, Averna MR. Variable phenotypic expression of chylomicron retention disease in a kindred carrying a mutation of the Sara2 gene. Metabolism 2010; 59:463-7. [PMID: 19846172 DOI: 10.1016/j.metabol.2009.07.042] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 07/08/2009] [Indexed: 11/29/2022]
Abstract
Chylomicron retention disease is a recessive inherited disorder characterized by fat malabsorption and steatorrhea and is associated with failure to thrive in infancy. We describe a kindred carrying a mutation of Sara2 gene causing a chylomicron retention phenotype. The proband was a 5-month-old baby, born of consanguineous, apparently healthy parents from Morocco, with failure to thrive. There was a large quantity of fats in feces and malabsorption of fat-soluble vitamins. Intestinal biopsies showed a diffused enterocyte vacuolization with large cytosolic lipid droplets. Chylomicron retention disease or Anderson disease was hypothesized, and the Sara2 gene was analyzed by direct sequencing. Analysis of the Sara2 gene in the proband identified a 2-nucleotide homozygous deletion in exon 3 leading to a premature stop codon (c.75-76 del TG-L28fsX34). The father was heterozygous for the same mutation, whereas the proband's mother was homozygous, suggesting a variable phenotypic expression of the molecular defect. More studies are needed to understand the reasons of the phenotypic variability of the same molecular defect in the same family.
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Affiliation(s)
- Angelo B Cefalù
- Departmet of Clinical Medicine and Emerging Diseases, University of Palermo, I-90127 Palermo, Italy
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Peretti N, Roy CC, Sassolas A, Deslandres C, Drouin E, Rasquin A, Seidman E, Brochu P, Vohl MC, Labarge S, Bouvier R, Samson-Bouma ME, Charcosset M, Lachaux A, Levy E. Chylomicron retention disease: a long term study of two cohorts. Mol Genet Metab 2009; 97:136-42. [PMID: 19285442 DOI: 10.1016/j.ymgme.2009.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 02/09/2009] [Indexed: 10/21/2022]
Abstract
Lipoprotein assembly is critical for the intestinal absorption of dietary lipids and of fat-soluble vitamins. Through their inhibition of chylomicron secretion, mutations of the Sar1B gene coding for Sar1 GTPase are associated with chylomicron retention disease (CRD). The aim of this study was to describe the phenotypic expression of CRD in two clinically and genetically well characterized cohorts, and to compare their long term evolution. The study in 7 children from France (X age 11.3+/-1.7 years) and 9 from Quebec, Canada (X age 12+/-2.5 years) involved data collection from medical records for growth evaluation, neurological and ophthalmological status as well as bone density over an average follow-up period of 4.9 years for the French cohort and of 10.6 years for the Canadian one. All CRD patients presented within the first few months of life with diarrhea and failure to thrive. Severe hypocholesterolemia coupled with normal triglycerides was associated with low LDL and HDL-cholesterol, as well as with low apolipoproteins A-I and B. Varying degrees of essential fatty acid and of vitamin E deficiency were observed. The earlier diagnosis in the Canadian cohort (1.3+/-0.04 years) than in the French one (6.3+/-1.3 years) was unrelated with the severity of presenting symptoms. The fact that the disease had more impact on growth and bone density in the latter group may be related to delayed diagnosis of the disease. Vitamin E deficiency led to functional neurological and ophthalmic changes in a small number of patients but only one developed areflexia. Finally, genotype-phenotype correlation is not obvious in our cohort with CRD; even if, the Canadian subjects with the allele 409G>A had a more severe degree (P<0.001) of hypocholesterolemia than the other patients, many clinical data are inconsistent with a hypothetical genotype-phenotype correlation. This study provides new insights on the phenotypic expression of CRD over time and emphasizes the need to screen the lipid profile of infants with chronic diarrhea and failure to thrive.
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Affiliation(s)
- Noel Peretti
- Department of Nutrition, CHU Sainte-Justine, Université de Montréal, GI-Nutrition Unit, 3175 Ste-Catherine Road, Montreal, Que., Canada
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Novel missense mutations of SAR1B gene in an infant with chylomicron retention disease. J Pediatr Gastroenterol Nutr 2009; 48:370-3. [PMID: 19274794 DOI: 10.1097/mpg.0b013e318183188f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Erickson RP, Larson-Thomé K, Valenzuela RK, Whitaker SE, Shub MD. Navajo microvillous inclusion disease is due to a mutation in MYO5B. Am J Med Genet A 2009; 146A:3117-9. [PMID: 19006234 DOI: 10.1002/ajmg.a.32605] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Microvillous Inclusion Disease (MID) is a rare, autosomal recessive gastrointestinal disease of increased frequency among the Navajos. Previous work has shown a deficiency of RAB8 in one Japanese patient, while homozygous mutations in MYO5B were found in 7 of 10 mostly Middle Eastern families. We have identified a shared homozygous mutation in MYO5B in seven affected Navajos with the expected heterozygosity in five parents. We have developed a simple restriction enzyme based assay that allows for rapid screening for this mutation.
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Affiliation(s)
- Robert P Erickson
- Department of Pediatrics, University of Arizona, Tucson, Arizona 85724-5073, USA.
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Silvain M, Bligny D, Aparicio T, Laforêt P, Grodet A, Peretti N, Ménard D, Djouadi F, Jardel C, Bégué JM, Walker F, Schmitz J, Lachaux A, Aggerbeck LP, Samson-Bouma ME. Anderson’s disease (chylomicron retention disease): a new mutation in the SARA2 gene associated with muscular and cardiac abnormalities. Clin Genet 2008; 74:546-52. [DOI: 10.1111/j.1399-0004.2008.01069.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Charcosset M, Sassolas A, Peretti N, Roy CC, Deslandres C, Sinnett D, Levy E, Lachaux A. Anderson or chylomicron retention disease: molecular impact of five mutations in the SAR1B gene on the structure and the functionality of Sar1b protein. Mol Genet Metab 2008; 93:74-84. [PMID: 17945526 DOI: 10.1016/j.ymgme.2007.08.120] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 08/13/2007] [Indexed: 10/22/2022]
Abstract
Anderson disease (and/or chylomicron retention disease-CMRD) is a rare, autosomic recessive disorder characterized by chronic diarrhea, failure to thrive, and hypocholesterolemia in childhood. The specific molecular defect was identified in 2003 and consists of mutations in the SAR1B gene which encodes for intracellular Sar1b protein. To date, only 8 mutations in six families have been described. We report here 15 new cases of CMRD among 8 families from France and Canada. We identified three unique homozygous mutations of SAR1B gene in French families originated from Turkey, Algeria and Portugal: a stop codon in exon 6 (c.364G>T, p.Glu122X), a whole deletion of exon 2 (c. 1-4482_58+1406 del 5946 ins15bp) and a missense mutation in exon 7 (c.554G>T, p.Gly185Val). The 2 missense mutations found in the 5 French-Canadian families had already been described in the eight previously published mutations: c.409G>A (p.Asp137Asn) and c.537T>A (p.Ser179Arg). In an attempt to explain the functional impairment of mutated proteins, computational analysis and sequence alignment were performed. The nonsense mutation and the whole deletion of exon 2 produced truncated proteins, the missense mutations probably non-functional proteins. All the affected children presented with similar phenotype at onset; the absence of phenotype-genotype correlation was discussed. A determination of the specific mutation in Anderson disease or CMRD is required to ensure diagnosis and allow prompt therapeutic intervention in these children.
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Affiliation(s)
- Mathilde Charcosset
- UF Lipides-Dyslipidémies, Laboratoire de Biochimie, CBE, 59 boulevard Pinel, Bron Cedex, France
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Levy E, Lavoie MA, Delvin E, Seidman E, Lambert M, Sinnett D, Sané AT, Leblond F, Spahis S, Roy CC. Avancées dans la dissection fonctionnelle du transport intestinal des lipides. Med Sci (Paris) 2007; 23:1014-9. [DOI: 10.1051/medsci/200723111014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Wopereis S, Lefeber DJ, Morava E, Wevers RA. Mechanisms in protein O-glycan biosynthesis and clinical and molecular aspects of protein O-glycan biosynthesis defects: a review. Clin Chem 2006; 52:574-600. [PMID: 16497938 DOI: 10.1373/clinchem.2005.063040] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND Genetic diseases that affect the biosynthesis of protein O-glycans are a rapidly growing group of disorders. Because this group of disorders does not have a collective name, it is difficult to get an overview of O-glycosylation in relation to human health and disease. Many patients with an unsolved defect in N-glycosylation are found to have an abnormal O-glycosylation as well. It is becoming increasingly evident that the primary defect of these disorders is not necessarily localized in one of the glycan-specific transferases, but can likewise be found in the biosynthesis of nucleotide sugars, their transport to the endoplasmic reticulum (ER)/Golgi, and in Golgi trafficking. Already, disorders in O-glycan biosynthesis form a substantial group of genetic diseases. In view of the number of genes involved in O-glycosylation processes and the increasing scientific interest in congenital disorders of glycosylation, it is expected that the number of identified diseases in this group will grow rapidly over the coming years. CONTENT We first discuss the biosynthesis of protein O-glycans from their building blocks to their secretion from the Golgi. Subsequently, we review 24 different genetic disorders in O-glycosylation and 10 different genetic disorders that affect both N- and O-glycosylation. The key clinical, metabolic, chemical, diagnostic, and genetic features are described. Additionally, we describe methods that can be used in clinical laboratory screening for protein O-glycosylation biosynthesis defects and their pitfalls. Finally, we introduce existing methods that might be useful for unraveling O-glycosylation defects in the future.
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Affiliation(s)
- Suzan Wopereis
- Laboratory of Pediatrics and Neurology and Department of Pediatrics, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
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Abstract
PURPOSE OF REVIEW The transport of lipoproteins through the secretory pathways of enterocytes and hepatocytes is pivotal for whole-body lipid homeostasis. This review focuses on the assembly and structural evolution of COPII (coat protein) transport carriers that are essential for the transport of chylomicrons from the endoplasmic reticulum to the Golgi apparatus. RECENT FINDINGS The assembly of endoplasmic reticulum to Golgi transport carriers commences with the coating of specific areas of the endoplasmic reticulum membrane with Sar1-GTP and the Sec23/24 heterodimer. An important advance has been the crystallographic analysis of the Sar1-Sec23/24 complex. The proteins form a bow-tie shaped structure, with a concave face that seems to match the curvature of transport carriers. Mammalian cells produce two isoforms of Sar1, designated Sar1a and Sar1b, both of which are expressed in enterocytes. Sar1b is defective in chylomicron retention disease and Anderson disease, two rare recessive disorders characterized by severe fat malabsorption and a failure to thrive in infancy. Patients with chylomicron retention disease and Anderson disease selectively retain chylomicron-like particles within membrane-bound compartments. By analogy with procollagen, chylomicrons may drive the formation of endoplasmic reticulum to Golgi transport carriers from endoplasmic reticulum sites close to, but separate from, domains of the endoplasmic reticulum coated with Sar1-Sec23/24. The COPII machinery also mediates the transport of VLDL to the Golgi. SUMMARY New insights into the role of the COPII machinery in the intracellular transport of cargo, including chylomicrons and VLDL, may suggest new drug targets for ameliorating the lipid abnormalities of the metabolic syndrome.
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Affiliation(s)
- Carol C Shoulders
- Medical Research Council Clinical Sciences Centre, Hammersmith Hospital, London, UK.
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Bankaitis VA, Cortese J, Phillips SE, Alb JG. Phosphatidylinositol transfer protein function in the mouse. ACTA ACUST UNITED AC 2004; 44:201-18. [PMID: 15581491 DOI: 10.1016/j.advenzreg.2003.11.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Vytas A Bankaitis
- Department of Cell and Developmental Biology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
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Alb JG, Cortese JD, Phillips SE, Albin RL, Nagy TR, Hamilton BA, Bankaitis VA. Mice lacking phosphatidylinositol transfer protein-alpha exhibit spinocerebellar degeneration, intestinal and hepatic steatosis, and hypoglycemia. J Biol Chem 2003; 278:33501-18. [PMID: 12788952 PMCID: PMC7798478 DOI: 10.1074/jbc.m303591200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Phosphatidylinositol transfer proteins (PITPs) regulate the interface between lipid metabolism and cellular functions. We now report that ablation of PITP alpha function leads to aponecrotic spinocerebellar disease, hypoglycemia, and intestinal and hepatic steatosis in mice. The data indicate that hypoglycemia is in part associated with reduced proglucagon gene expression and glycogenolysis that result from pancreatic islet cell defects. The intestinal and hepatic steatosis results from the intracellular accumulation of neutral lipid and free fatty acid mass in these organs and suggests defective trafficking of triglycerides and diacylglycerols from the endoplasmic reticulum. We propose that deranged intestinal and hepatic lipid metabolism and defective proglucagon gene expression contribute to hypoglycemia in PITP alpha-/- mice, and that hypoglycemia is a significant contributing factor in the onset of spinocerebellar disease. Taken together, the data suggest an unanticipated role for PITP alpha in with glucose homeostasis and in mammalian endoplasmic reticulum functions that interface with transport of specific luminal lipid cargoes.
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Affiliation(s)
- James G. Alb
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7090
| | - Jorge D. Cortese
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7090
| | - Scott E. Phillips
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7090
| | - Roger L. Albin
- Department of Neurology, University of Michigan School of Medicine, Ann Arbor Veterans Affairs Medical Center GRECC, Ann Arbor, Michigan 48104-0520
| | - Tim R. Nagy
- Department of Nutrition, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Bruce A. Hamilton
- University of California School of Medicine, San Diego, La Jolla, California 92093-0644
| | - Vytas A. Bankaitis
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7090
- To whom correspondence should be addressed. Tel.: 919-962-9870; Fax: 919-966-1856;
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Jones B, Jones EL, Bonney SA, Patel HN, Mensenkamp AR, Eichenbaum-Voline S, Rudling M, Myrdal U, Annesi G, Naik S, Meadows N, Quattrone A, Islam SA, Naoumova RP, Angelin B, Infante R, Levy E, Roy CC, Freemont PS, Scott J, Shoulders CC. Mutations in a Sar1 GTPase of COPII vesicles are associated with lipid absorption disorders. Nat Genet 2003; 34:29-31. [PMID: 12692552 DOI: 10.1038/ng1145] [Citation(s) in RCA: 303] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2002] [Accepted: 03/27/2003] [Indexed: 01/05/2023]
Abstract
Dietary fat is an important source of nutrition. Here we identify eight mutations in SARA2 that are associated with three severe disorders of fat malabsorption. The Sar1 family of proteins initiates the intracellular transport of proteins in COPII (coat protein)-coated vesicles. Our data suggest that chylomicrons, which vastly exceed the size of typical COPII vesicles, are selectively recruited by the COPII machinery for transport through the secretory pathways of the cell.
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Affiliation(s)
- Bethan Jones
- Genomic & Molecular Medicine Group, MRC Clinical Sciences Centre, Imperial College, London, England, UK
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Stormon MO, Mitchell JD, Smoleniec JS, Tobias V, Day AS. Congenital intestinal lymphatic hypoplasia presenting as non-immune hydrops in utero, and subsequent neonatal protein-losing enteropathy. J Pediatr Gastroenterol Nutr 2002; 35:691-4. [PMID: 12454588 DOI: 10.1097/00005176-200211000-00020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Affiliation(s)
- M O Stormon
- Department of Gastroenterology, Sydney Children's Hospital, Randwick, NSW, Australia
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Hartman C, Tamary H, Tamir A, Shabad E, Levine C, Koren A, Shamir R. Hypocholesterolemia in children and adolescents with beta-thalassemia intermedia. J Pediatr 2002; 141:543-7. [PMID: 12378195 DOI: 10.1067/mpd.2002.127498] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVES To conduct a prospective study to evaluate the lipid profile in children and adolescents with beta-thalassemia intermedia and major, and to examine the contribution of different factors to hypocholesterolemia observed in these patients. STUDY DESIGN Demographic, clinical, and laboratory data were prospectively obtained from patients with beta-thalassemia intermedia (n = 9) and major (n = 47). Lipid profiles were also determined in a control group of healthy children (n = 18). Lipid values of beta-thalassemics and controls were compared and the relationships between lipid levels and different covariates were determined. RESULTS beta-thalassemia intermedia patients had significantly lower total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) compared with beta-thalassemia major and controls (P <.001). With regression analysis, serum lipid levels (TC, HDL-C, and triglycerides) correlated with diagnosis (beta-thalassemia major or intermedia) but not with age, sex, hemoglobin, or ferritin. LDL-C was influenced by both diagnosis and ferritin levels. CONCLUSIONS Children and adolescents with beta-thalassemia intermedia have significantly lower cholesterol levels than patients with beta-thalassemia major. This is related to their disorder and not influenced by age, sex, hemoglobin, or ferritin levels. In these patients, needless investigations for hypolipidemia should be avoided.
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Affiliation(s)
- Corina Hartman
- Division of Pediatric Gastroenterology and Nutrition, Department of Pediatrics, Rambam Medical Center, Haifa, Israel
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Boldrini R, Biselli R, Bosman C. Chylomicron retention disease--the role of ultrastructural examination in differential diagnosis. Pathol Res Pract 2002; 197:753-7. [PMID: 11770019 DOI: 10.1078/0344-0338-00154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Three children with malabsorption presumably caused by celiac disease had undergone jejunal biopsy. While a histological examination revealed microvacuolization of enterocytes in the absence of celiac lesions, an ultrastructural investigation disclosed numerous chylomicrons and larger lipid vacuoles inside the cytoplasm of enterocytes, mostly in the supranuclear region. No chylomicrons were evident in the interstitium between adjacent enterocytes, as observed in normal subjects. These ultrastructural findings allowed for the diagnosis of "Chylomicron retention disease" (CRD). CRD was described for the first time by Anderson in 1961, and it is included in the group of disorders of biosynthesis and secretion of B apolipoproteins (apoB). This disease, in particular, appears to result from a specific defect involving the secretion of lipoproteins containing apoB-48 from the gut, with the complete absence of post prandial chylomicrons in the sera. CRD needs to be recognized early because of its adverse effects on growth and its potential for neurological and ocular complications, and the ultrastructural identification of chylomicron-size lipid droplets clustered in the enterocytes, with the absence of fat outside the cells, represents the gold standard to identify CRD. together with clinical aspects and laboratory measurements. In this study, we describe the histological and ultrastructural aspects observed in three pediatric cases of CRD.
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Affiliation(s)
- R Boldrini
- Dipartimento di Anatomia Patologia, Ospedale Pediatrico Bambino Gesù, IRCCS, Roma, Italy
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Cartwright IJ, Higgins JA. Direct evidence for a two-step assembly of ApoB48-containing lipoproteins in the lumen of the smooth endoplasmic reticulum of rabbit enterocytes. J Biol Chem 2001; 276:48048-57. [PMID: 11675380 DOI: 10.1074/jbc.m104229200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aim of this study was to investigate the types and characteristics of chylomicron precursors in the lumen of the secretory compartment of rabbit enterocytes. Luminal contents were separated into density subfractions in two continuous self-generating gradients of different density profiles. In enterocytes from rabbits fed a low fat diet, newly synthesized and immunodetectable apoB48 was only in the subfraction of density similar to high density lipoprotein (dense particles); the luminal triacylglycerol (TAG) content was low and only in the subfraction of density similar to that of chylomicrons/very low density lipoproteins (light particles). After feeding fat, newly synthesized, and immunodetectable apoB48 was in both dense (phospholipid-rich) and light (TAG-rich) particles. Luminal TAG mass and synthesis increased after fat feeding and was only in light particles. Pulse-chase experiments showed that the luminal-radiolabeled apoB48 lost from the dense particles was recovered in the light particles and the secreted chylomicrons. All of the light particle lipids (mass and newly synthesized) co-immunoprecipitated with apoB48. However, in the dense particles, there was a preferential co-precipitation of the preexisting rather than newly synthesized phospholipid. Assembly of apoB48-containing TAG-enriched lipoproteins is therefore a two-step process. The first step produces dense apoB48 phospholipid-rich particles, which accumulate in the smooth endoplasmic reticulum lumen. In the second step, these dense particles rapidly acquire the bulk of the TAG and additional phospholipid in a single and rapid step.
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Affiliation(s)
- I J Cartwright
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
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Berriot-Varoqueaux N, Dannoura AH, Moreau A, Verthier N, Sassolas A, Cadiot G, Lachaux A, Munck A, Schmitz J, Aggerbeck LP, Samson-Bouma ME. Apolipoprotein B48 glycosylation in abetalipoproteinemia and Anderson's disease. Gastroenterology 2001; 121:1101-8. [PMID: 11677202 DOI: 10.1053/gast.2001.29331] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS Abetalipoproteinemia and Anderson's disease are hereditary lipid malabsorption syndromes. In abetalipoproteinemia, lipoprotein assembly is defective because of mutations in the microsomal triglyceride transfer protein. Here, we evaluated the intracellular transport of apolipoprotein B48 to localize the defect in Anderson's disease. METHODS Asparagine-linked oligosaccharide processing of apolipoprotein B48 in normal and affected individuals was determined by the endoglycosidase H and F sensitivities of the protein after metabolic labeling of intestinal explants in organ culture. Cell ultrastructure was evaluated with electron microscopy. RESULTS In Anderson's disease as in normal individuals, there was a time-dependent transformation of high mannose endoglycosidase H-sensitive oligosaccharides, of endoplasmic reticulum origin, to complex endoglycosidase H-resistant oligosaccharides, added in the Golgi network. In contrast, despite the translocation of apolipoprotein B48 into the endoplasmic reticulum in patients with abetalipoproteinemia and in biopsies treated with Brefeldin A, which blocks anterograde transport between the endoplasmic reticulum and the Golgi network, there was no transformation of endoglycosidase H-sensitive oligosaccharides. CONCLUSIONS In abetalipoproteinemia and Anderson's disease, apolipoprotein B48 is completely translocated into the endoplasmic reticulum, but only in Anderson's disease is the protein transported to the Golgi apparatus. This suggests that Anderson's disease is caused by a post-Golgi cargo-specific secretion defect.
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Abstract
In this article, disease of the small intestine will be discussed, with particular reference to those conditions leading to malabsorption and malnutrition. The work up of these entities will be emphasized, with focus on bacterial overgrowth, celiac sprue and nonsteroidal-induced enteropathy.
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Affiliation(s)
- S Tabrez
- Section of Gastroenterology, Department of Medicine, Bridgeport Hospital, Bridgeport, Connecticut 06610, USA
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47
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48
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Aguglia U, Annesi G, Pasquinelli G, Spadafora P, Gambardella A, Annesi F, Pasqua AA, Cavalcanti F, Crescibene L, Bagal� A, Bono F, Oliveri RL, Valentino P, Zappia M, Quattrone A. Vitamin E deficiency due to chylomicron retention disease in Marinesco-Sj�gren syndrome. Ann Neurol 2001. [DOI: 10.1002/1531-8249(200002)47:2<260::aid-ana21>3.0.co;2-v] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Cartwright IJ, Plonné D, Higgins JA. Intracellular events in the assembly of chylomicrons in rabbit enterocytes. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31966-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Elias N, Patterson BW, Schonfeld G. In vivo metabolism of ApoB, ApoA-I, and VLDL triglycerides in a form of hypobetalipoproteinemia not linked to the ApoB gene. Arterioscler Thromb Vasc Biol 2000; 20:1309-15. [PMID: 10807747 DOI: 10.1161/01.atv.20.5.1309] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Familial hypobetalipoproteinemia (FHBL) is an autosomal codominant disorder that may result from different mutations in the apolipoprotein B (apoB) gene or chromosome 2. However, linkage of FHBL to the apoB gene was ruled out in 2 kindreds reported to date, and the genetic and metabolic bases for FHBL remain unknown. One of the reported kindreds is our 40-member F kindred, in which we found linkage of FHBL to a novel susceptibility region on chromosome 3p21. 1-2. In addition to having low apoB levels, some, but not all, of the affected subjects in the F kindred also had low levels of high density lipoprotein (HDL) cholesterol and apoA-I. Our aim was to define the metabolic bases of the disorder in the F kindred. Therefore, we studied the in vivo kinetics of apoB and apoA-I and very low density lipoprotein (VLDL) triglycerides in 4 affected subjects and 5 normolipidemic relatives. Deuterated leucine and deuterated glycerol were used to label the apolipoproteins and triglycerides, respectively. Compartmental modeling was used to obtain the kinetic parameters. Affected subjects had (1) normal fractional catabolic rates (FCRs) for VLDL apoB, (2) increased FCRs for low density lipoprotein (LDL) apoB (0.050+/-0.009 versus 0. 030+/-0.006 pools per hour for normal subjects, P=0.005), and (3) decreased production rates of VLDL apoB (11.4+/-1.7 versus 25.6+/-4. 9 mg. kg(-1). d(-1), P=0.003), LDL apoB (7.8+/-1.3 versus 12.7+/-3.7 mg. kg(-1). d(-1), P=0.04), and VLDL triglycerides (8.2+/-4.5 versus 19.6+/-10.8 58 micromol. kg(-1). h(-1), P=0.09). These data differ from those obtained in previously studied FHBL heterozygotes bearing apoB-2 and apoB-9, 2 very short truncations of apoB. Low HDL cholesterol and apoA-I levels were caused by higher apoA-I FCRs (0. 035+/-0.005 versus 0.018+/-0.005 pools per hour in controls, P<0.01) without significant decrease in apoA-I production rates (18.7+/-2.7 versus 22.8+/-5.6 mg. kg(-1). d(-1)). In conclusion, decreased secretion of apoB-containing lipoproteins and hypercatabolism of LDL account for low apoB and cholesterol levels in this novel form of FHBL.
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Affiliation(s)
- N Elias
- Division of Atherosclerosis, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO, USA
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