1
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Clifford BL, Sedgeman LR, Williams KJ, Morand P, Cheng A, Jarrett KE, Chan AP, Brearley-Sholto MC, Wahlström A, Ashby JW, Barshop W, Wohlschlegel J, Calkin AC, Liu Y, Thorell A, Meikle PJ, Drew BG, Mack JJ, Marschall HU, Tarling EJ, Edwards PA, de Aguiar Vallim TQ. FXR activation protects against NAFLD via bile-acid-dependent reductions in lipid absorption. Cell Metab 2021; 33:1671-1684.e4. [PMID: 34270928 PMCID: PMC8353952 DOI: 10.1016/j.cmet.2021.06.012] [Citation(s) in RCA: 155] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/12/2021] [Accepted: 06/21/2021] [Indexed: 12/24/2022]
Abstract
FXR agonists are used to treat non-alcoholic fatty liver disease (NAFLD), in part because they reduce hepatic lipids. Here, we show that FXR activation with the FXR agonist GSK2324 controls hepatic lipids via reduced absorption and selective decreases in fatty acid synthesis. Using comprehensive lipidomic analyses, we show that FXR activation in mice or humans specifically reduces hepatic levels of mono- and polyunsaturated fatty acids (MUFA and PUFA). Decreases in MUFA are due to FXR-dependent repression of Scd1, Dgat2, and Lpin1 expression, which is independent of SHP and SREBP1c. FXR-dependent decreases in PUFAs are mediated by decreases in lipid absorption. Replenishing bile acids in the diet prevented decreased lipid absorption in GSK2324-treated mice, suggesting that FXR reduces absorption via decreased bile acids. We used tissue-specific FXR KO mice to show that hepatic FXR controls lipogenic genes, whereas intestinal FXR controls lipid absorption. Together, our studies establish two distinct pathways by which FXR regulates hepatic lipids.
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Affiliation(s)
- Bethan L Clifford
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Leslie R Sedgeman
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Kevin J Williams
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Lipidomics Core Facility, Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Pauline Morand
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Angela Cheng
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Kelsey E Jarrett
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Alvin P Chan
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Madelaine C Brearley-Sholto
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Annika Wahlström
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Julianne W Ashby
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - William Barshop
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - James Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Anna C Calkin
- Lipid Metabolism & Cardiometabolic Disease Laboratory, Baker Heart & Diabetes Institute, Melbourne, VIC, Australia; Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Yingying Liu
- Lipid Metabolism & Cardiometabolic Disease Laboratory, Baker Heart & Diabetes Institute, Melbourne, VIC, Australia; Molecular Metabolism & Ageing Laboratory, Baker Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Anders Thorell
- Karolinska Institutet, Department of Clinical Science, Danderyd Hospital and Department of Surgery, Ersta Hospital, Stockholm, Sweden
| | - Peter J Meikle
- Metabolomics Laboratory, Baker Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Brian G Drew
- Central Clinical School, Monash University, Melbourne, VIC, Australia; Molecular Metabolism & Ageing Laboratory, Baker Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Julia J Mack
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Hanns-Ulrich Marschall
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Elizabeth J Tarling
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Jonsson Comprehensive Cancer Center (JCCC), UCLA, Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Peter A Edwards
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Thomas Q de Aguiar Vallim
- Department of Medicine, Division of Cardiology, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA; Jonsson Comprehensive Cancer Center (JCCC), UCLA, Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
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2
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von Scheidt M, Zhao Y, de Aguiar Vallim TQ, Che N, Wierer M, Seldin MM, Franzén O, Kurt Z, Pang S, Bongiovanni D, Yamamoto M, Edwards PA, Ruusalepp A, Kovacic JC, Mann M, Björkegren JLM, Lusis AJ, Yang X, Schunkert H. Transcription Factor MAFF (MAF Basic Leucine Zipper Transcription Factor F) Regulates an Atherosclerosis Relevant Network Connecting Inflammation and Cholesterol Metabolism. Circulation 2021; 143:1809-1823. [PMID: 33626882 DOI: 10.1161/circulationaha.120.050186] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Coronary artery disease (CAD) is a multifactorial condition with both genetic and exogenous causes. The contribution of tissue-specific functional networks to the development of atherosclerosis remains largely unclear. The aim of this study was to identify and characterize central regulators and networks leading to atherosclerosis. METHODS Based on several hundred genes known to affect atherosclerosis risk in mouse (as demonstrated in knockout models) and human (as shown by genome-wide association studies), liver gene regulatory networks were modeled. The hierarchical order and regulatory directions of genes within the network were based on Bayesian prediction models, as well as experimental studies including chromatin immunoprecipitation DNA-sequencing, chromatin immunoprecipitation mass spectrometry, overexpression, small interfering RNA knockdown in mouse and human liver cells, and knockout mouse experiments. Bioinformatics and correlation analyses were used to clarify associations between central genes and CAD phenotypes in both human and mouse. RESULTS The transcription factor MAFF (MAF basic leucine zipper transcription factor F) interacted as a key driver of a liver network with 3 human genes at CAD genome-wide association studies loci and 11 atherosclerotic murine genes. Most importantly, expression levels of the low-density lipoprotein receptor (LDLR) gene correlated with MAFF in 600 CAD patients undergoing bypass surgery (STARNET [Stockholm-Tartu Atherosclerosis Reverse Network Engineering Task]) and a hybrid mouse diversity panel involving 105 different inbred mouse strains. Molecular mechanisms of MAFF were tested in noninflammatory conditions and showed positive correlation between MAFF and LDLR in vitro and in vivo. Interestingly, after lipopolysaccharide stimulation (inflammatory conditions), an inverse correlation between MAFF and LDLR in vitro and in vivo was observed. Chromatin immunoprecipitation mass spectrometry revealed that the human CAD genome-wide association studies candidate BACH1 (BTB domain and CNC homolog 1) assists MAFF in the presence of lipopolysaccharide stimulation with respective heterodimers binding at the MAF recognition element of the LDLR promoter to transcriptionally downregulate LDLR expression. CONCLUSIONS The transcription factor MAFF was identified as a novel central regulator of an atherosclerosis/CAD-relevant liver network. MAFF triggered context-specific expression of LDLR and other genes known to affect CAD risk. Our results suggest that MAFF is a missing link between inflammation, lipid and lipoprotein metabolism, and a possible treatment target.
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Affiliation(s)
- Moritz von Scheidt
- Department of Cardiology, Deutsches Herzzentrum München, Technische Universität München, Munich, Germany (M.v.S., S.P., H.S.).,Deutsches Zentrum für Herz- und Kreislauferkrankungen, Partner Site Munich Heart Alliance, Germany (M.v.S., D.B., H.S.)
| | | | - Thomas Q de Aguiar Vallim
- Departments of Medicine (T.Q.d.A.V., N.C., P.A.E., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Biological Chemistry (T.Q.d.A.V., P.A.E.), David Geffen School of Medicine, University of California, Los Angeles
| | - Nam Che
- Departments of Medicine (T.Q.d.A.V., N.C., P.A.E., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Microbiology, Immunology and Molecular Genetics (N.C., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Human Genetics (N.C., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles
| | - Michael Wierer
- Department of Proteomics and Signal Transduction, Max-Planck Institute of Biochemistry, Martinsried, Germany (M.W., M.M.)
| | - Marcus M Seldin
- Department of Biological Chemistry and Center for Epigenetics and Metabolism, University of California, Irvine (M.M.S.)
| | - Oscar Franzén
- Integrated Cardio Metabolic Centre, Karolinska Institutet, Novum, Huddinge, Sweden (O.F., J.L.M.B.)
| | - Zeyneb Kurt
- Department of Computer and Information Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom (Z.K.)
| | - Shichao Pang
- Department of Cardiology, Deutsches Herzzentrum München, Technische Universität München, Munich, Germany (M.v.S., S.P., H.S.)
| | - Dario Bongiovanni
- Deutsches Zentrum für Herz- und Kreislauferkrankungen, Partner Site Munich Heart Alliance, Germany (M.v.S., D.B., H.S.).,Department of Internal Medicine, School of Medicine, University Hospital Rechts der Isar, Technical University of Munich, Germany (D.B.)
| | - Masayuki Yamamoto
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan (M.Y.)
| | - Peter A Edwards
- Departments of Medicine (T.Q.d.A.V., N.C., P.A.E., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Biological Chemistry (T.Q.d.A.V., P.A.E.), David Geffen School of Medicine, University of California, Los Angeles
| | - Arno Ruusalepp
- Department of Cardiac Surgery, Tartu University Hospital, Estonia (A.R.).,Clinical Gene Networks AB, Stockholm, Sweden (A.R., J.L.M.B.)
| | - Jason C Kovacic
- Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, New York (J.C.K., J.L.M.B.)
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max-Planck Institute of Biochemistry, Martinsried, Germany (M.W., M.M.)
| | - Johan L M Björkegren
- Integrated Cardio Metabolic Centre, Karolinska Institutet, Novum, Huddinge, Sweden (O.F., J.L.M.B.).,Clinical Gene Networks AB, Stockholm, Sweden (A.R., J.L.M.B.).,Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, New York (J.C.K., J.L.M.B.)
| | - Aldons J Lusis
- Departments of Medicine (T.Q.d.A.V., N.C., P.A.E., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Microbiology, Immunology and Molecular Genetics (N.C., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles.,Human Genetics (N.C., A.J.L.), David Geffen School of Medicine, University of California, Los Angeles
| | - Xia Yang
- Department of Integrative Biology and Physiology, Institute for Quantitative and Computational Biosciences (Y.Z., X.Y.), David Geffen School of Medicine, University of California, Los Angeles
| | - Heribert Schunkert
- Department of Cardiology, Deutsches Herzzentrum München, Technische Universität München, Munich, Germany (M.v.S., S.P., H.S.).,Deutsches Zentrum für Herz- und Kreislauferkrankungen, Partner Site Munich Heart Alliance, Germany (M.v.S., D.B., H.S.)
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3
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Pradas-Juni M, Hansmeier NR, Link JC, Schmidt E, Larsen BD, Klemm P, Meola N, Topel H, Loureiro R, Dhaouadi I, Kiefer CA, Schwarzer R, Khani S, Oliverio M, Awazawa M, Frommolt P, Heeren J, Scheja L, Heine M, Dieterich C, Büning H, Yang L, Cao H, Jesus DFD, Kulkarni RN, Zevnik B, Tröder SE, Knippschild U, Edwards PA, Lee RG, Yamamoto M, Ulitsky I, Fernandez-Rebollo E, Vallim TQDA, Kornfeld JW. A MAFG-lncRNA axis links systemic nutrient abundance to hepatic glucose metabolism. Nat Commun 2020; 11:644. [PMID: 32005828 PMCID: PMC6994702 DOI: 10.1038/s41467-020-14323-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 12/27/2019] [Indexed: 02/07/2023] Open
Abstract
Obesity and type 2 diabetes mellitus are global emergencies and long noncoding RNAs (lncRNAs) are regulatory transcripts with elusive functions in metabolism. Here we show that a high fraction of lncRNAs, but not protein-coding mRNAs, are repressed during diet-induced obesity (DIO) and refeeding, whilst nutrient deprivation induced lncRNAs in mouse liver. Similarly, lncRNAs are lost in diabetic humans. LncRNA promoter analyses, global cistrome and gain-of-function analyses confirm that increased MAFG signaling during DIO curbs lncRNA expression. Silencing Mafg in mouse hepatocytes and obese mice elicits a fasting-like gene expression profile, improves glucose metabolism, de-represses lncRNAs and impairs mammalian target of rapamycin (mTOR) activation. We find that obesity-repressed LincIRS2 is controlled by MAFG and observe that genetic and RNAi-mediated LincIRS2 loss causes elevated blood glucose, insulin resistance and aberrant glucose output in lean mice. Taken together, we identify a MAFG-lncRNA axis controlling hepatic glucose metabolism in health and metabolic disease. Despite widespread transcription of LncRNA in mammalian systems, their contribution to metabolic homeostasis at the cellular and tissue level remains elusive. Here Pradas-Juni et al. describe a transcription factor–LncRNA pathway that couples hepatocyte nutrient sensing to regulation of glucose metabolism in mice.
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Affiliation(s)
- Marta Pradas-Juni
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.,Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Nils R Hansmeier
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Jenny C Link
- Department of Biological Chemistry, University of California, Los Angeles (UCLA), 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.,Department of Medicine, Division of Cardiology, UCLA, 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Elena Schmidt
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Bjørk Ditlev Larsen
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Paul Klemm
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Nicola Meola
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Hande Topel
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.,Izmir Biomedicine and Genome Center (IBG), Mithatpasa Ave. 58/5, 35340, Izmir, Turkey.,Department of Medical Biology and Genetics, Graduate School of Health Sciences, Dokuz Eylul University, Mithatpasa Ave. 1606, 35330, Izmir, Turkey
| | - Rute Loureiro
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.,Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Ines Dhaouadi
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Christoph A Kiefer
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Robin Schwarzer
- Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Sajjad Khani
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Matteo Oliverio
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Motoharu Awazawa
- Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany.,Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Peter Frommolt
- Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, Martinistraße 52, 20246, Hamburg, Germany
| | - Ludger Scheja
- Department of Biochemistry and Molecular Cell Biology, Martinistraße 52, 20246, Hamburg, Germany
| | - Markus Heine
- Department of Biochemistry and Molecular Cell Biology, Martinistraße 52, 20246, Hamburg, Germany
| | - Christoph Dieterich
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology, University Hospital Heidelberg, Im Neuenheimer Feld 669, 69120, Heidelberg, Germany
| | - Hildegard Büning
- Institute of Experimental Hematology, Hanover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Ling Yang
- Cardiovascular Branch, National Heart Lung and Blood Institute, Bethesda, MD, 20892, USA.,Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 19140, USA
| | - Haiming Cao
- Cardiovascular Branch, National Heart Lung and Blood Institute, Bethesda, MD, 20892, USA
| | - Dario F De Jesus
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, 02215, MA, USA
| | - Rohit N Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, 02215, MA, USA
| | - Branko Zevnik
- CECAD in vivo Research Facility, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Simon E Tröder
- CECAD in vivo Research Facility, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany
| | - Uwe Knippschild
- Department of General and Visceral Surgery, University Hospital Ulm, Albert-Einstein Allee 93, 89081, Ulm, Germany
| | - Peter A Edwards
- Department of Biological Chemistry, University of California, Los Angeles (UCLA), 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.,Department of Medicine, Division of Cardiology, UCLA, 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | | | - Masayuki Yamamoto
- Department of Medical Biochemistry, Tohoku Medical Megabank Organization, Sendai, 980-8573, Japan
| | - Igor Ulitsky
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Eduardo Fernandez-Rebollo
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Thomas Q de Aguiar Vallim
- Department of Biological Chemistry, University of California, Los Angeles (UCLA), 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA. .,Department of Medicine, Division of Cardiology, UCLA, 650 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
| | - Jan-Wilhelm Kornfeld
- Functional Genomics and Metabolism Unit, Department for Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark. .,Max Planck Institute for Metabolism Research, Gleueler Strasse 50, 50931, Cologne, Germany. .,Cologne Cluster of Excellence-Cellular Stress Responses in Ageing-associated Diseases (CECAD), Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931, Cologne, Germany.
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4
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Von Scheidt M, Zhao Y, De Aguiar Vallim TQ, Che N, Franzen O, Kurt Z, Yamamoto M, Edwards PA, Ruusalepp A, Kovacic J, Bjorkegren JLM, Lusis AJ, Yang X, Schunkert H. P1844The transcription factor MAFF regulates an atherosclerosis relevant gene network. Eur Heart J 2018. [DOI: 10.1093/eurheartj/ehy565.p1844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M Von Scheidt
- German Heart Center of Munich, Cardiology, Munich, Germany
| | - Y Zhao
- University of California Los Angeles, Integrative Biology and Physiology, Institute for Quantitative and Computational Biosciences (QCBio), Los Angeles, United States of America
| | - T Q De Aguiar Vallim
- University of California Los Angeles, Medicine and Biological Chemistry, David Geffen School of Medicine, Los Angeles, United States of America
| | - N Che
- University of California Los Angeles, Medicine, Microbiology, Immunology, and Molecular Genetics, and Human Genetics, Los Angeles, United States of America
| | - O Franzen
- Karolinska Institute, Integrated Cardio Metabolic Centre, Stockholm, Sweden
| | - Z Kurt
- University of California Los Angeles, Integrative Biology and Physiology, Institute for Quantitative and Computational Biosciences (QCBio), Los Angeles, United States of America
| | - M Yamamoto
- Tohoku University, Integrative Genomics, Sendai, Japan
| | - P A Edwards
- University of California Los Angeles, Biological Chemistry, David Geffen School of Medicine, Los Angeles, United States of America
| | - A Ruusalepp
- Tartu University Hospital, Cardiac Surgery, Tartu, Estonia
| | - J Kovacic
- Icahn School of Medicine at Mount Sinai, Cardiovascular Research Center, New York, United States of America
| | - J L M Bjorkegren
- Icahn School of Medicine at Mount Sinai, Genetics and Genomic Sciences, New York, United States of America
| | - A J Lusis
- University of California Los Angeles, Medicine, Microbiology, Immunology, and Molecular Genetics, and Human Genetics, Los Angeles, United States of America
| | - X Yang
- University of California Los Angeles, Integrative Biology and Physiology, Institute for Quantitative and Computational Biosciences (QCBio), Los Angeles, United States of America
| | - H Schunkert
- German Heart Center of Munich, Cardiology, Munich, Germany
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5
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Tarling EJ, Edwards PA. Intracellular Localization of Endogenous Mouse ABCG1 Is Mimicked by Both ABCG1-L550 and ABCG1-P550-Brief Report. Arterioscler Thromb Vasc Biol 2016; 36:1323-7. [PMID: 27230131 DOI: 10.1161/atvbaha.116.307414] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 05/10/2016] [Indexed: 12/18/2022]
Abstract
OBJECTIVE In a recent article in Arteriosclerosis, Thrombosis, and Vascular Biology, it was reported that ATP-binding cassette transporter G1 (ABCG1) containing leucine at position 550 (ABCG1-L550) was localized to the plasma membrane, whereas ABCG1-P550 (proline at position 550) was intracellular. Because the published data on the subcellular localization of ABCG1 are controversial, we performed additional experiments to determine the importance of leucine or proline at amino acid 550. APPROACH AND RESULTS We transfected multiple cell lines (CHO-K1, Cos-7, and HEK293 [human embryonic kidney]) with untagged or FLAG-tagged ABCG1 containing either leucine or proline at position 550. Immunofluorescence studies demonstrated that in all cases, ABCG1 localized to intracellular endosomal vesicles. We also show that both ABCG1-L550 and ABCG1-P550 are equally active in both promoting the efflux of cellular cholesterol to exogenous high-density lipoprotein and in inducing the activity of sterol regulatory element-binding protein-2, presumably as a result of redistributing intracellular sterols away from the endoplasmic reticulum. Importantly, we treated nontransfected primary peritoneal macrophages with a liver X receptor agonist and demonstrate, using immunofluorescence, that although endogenous ABCG1 localizes to intracellular endosomes, none was detectable at the cell surface/plasma membrane. CONCLUSIONS ABCG1, irrespective of either a leucine or proline at position 550, is an intracellular protein that localizes to vesicles of the endosomal pathway where it functions to mobilize sterols away from the endoplasmic reticulum and out of the cell.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily G, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily G, Member 1/deficiency
- ATP Binding Cassette Transporter, Subfamily G, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily G, Member 1/metabolism
- Amino Acid Sequence
- Animals
- Biological Transport
- CHO Cells
- COS Cells
- Chlorocebus aethiops
- Cholesterol/metabolism
- Cholesterol, HDL/metabolism
- Cricetulus
- Endosomes/metabolism
- Genotype
- HEK293 Cells
- Humans
- Leucine
- Liver X Receptors/agonists
- Liver X Receptors/metabolism
- Macrophages, Peritoneal/drug effects
- Macrophages, Peritoneal/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Phenotype
- Primary Cell Culture
- Proline
- Sterol Regulatory Element Binding Protein 2/metabolism
- Transfection
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Affiliation(s)
- Elizabeth J Tarling
- From the Departments of Biological Chemistry (P.A.E.) and Medicine (E.J.T.), David Geffen School of Medicine at the University of California, Los Angeles.
| | - Peter A Edwards
- From the Departments of Biological Chemistry (P.A.E.) and Medicine (E.J.T.), David Geffen School of Medicine at the University of California, Los Angeles
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6
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Divani AA, Chow R, Sadeghi-Bazargani H, Murphy AJ, Nordberg JA, Tokarev JV, Hevesi M, Wang X, Zhu XH, Acompanado T, Edwards PA, Zhang Y, Chen W. Focal middle cerebral artery ischemia in rats via a transfemoral approach using a custom designed microwire. J Neurointerv Surg 2015; 8:608-14. [PMID: 25935923 DOI: 10.1136/neurintsurg-2014-011607] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/15/2015] [Indexed: 11/03/2022]
Abstract
OBJECTIVES The aim of this study was to develop a reliable and repeatable method of inducing focal middle cerebral artery occlusion (MCAo) in rats without ligation of the external carotid artery (ECA), while reducing the risk of subarachnoid hemorrhage. METHODS We prototyped microwires with different diameters (0.0120 inch, 0.0115 inch, 0.0110 inch), materials, and construction methods (coil-on-core, extruded polymer jacket-on-core). Under fluoroscopic guidance and using femoral artery access, the microwires were navigated into the internal carotid artery of male Wistar rats (n=50, weight 376±64 g) to induce MCAo for 1 or 2 h. We performed neurological assessments at baseline, and at 3, 24, 72, and 168 h after MCAo. MRI measurements were performed on a 9.4 T scanner at 1 and 7 days post-injury. RESULTS The 0.0115 inch microwire with polymer jacket-on-core provided the most successful outcome. At 1 and 7 days post-injury, we observed similar infarction volumes for 1 and 2 h MCAo in the MRI study. Infarcted lesion volumes in both MCAo groups were significantly reduced at 7 days compared with 1 day post-injury. The trend in longitudinal changes for the scores of different neurological assessments was confirmed to be significant after the injury, but both groups showed a similar trend of neurological deficits over the course of the study. CONCLUSIONS We have developed a reliable and repeatable MCAo method in rats, allowing for precise occlusion of the MCA under direct fluoroscopic visualization without alteration of the cerebral hemodynamics associated with ECA ligation. The custom designed microwire can also be sized for targeted focal ischemia in larger animals.
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Affiliation(s)
- Afshin A Divani
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA Department of Neurological Surgery, University of Minnesota, Minneapolis, Minnesota, USA Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA
| | - Ricky Chow
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA Lake Region Medical, Chaska, Minnesota, USA
| | - Homayoun Sadeghi-Bazargani
- Neurosciences Research Center, Tabriz University of Medical Sciences, Iran Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden
| | - Amanda J Murphy
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Jessica A Nordberg
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Julian V Tokarev
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Mario Hevesi
- Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Xiao Wang
- Department of Radiology, Center for Magnetic Imaging Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Xiao-Hong Zhu
- Department of Radiology, Center for Magnetic Imaging Research, University of Minnesota, Minneapolis, Minnesota, USA
| | | | | | - Yi Zhang
- Department of Radiology, Center for Magnetic Imaging Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Wei Chen
- Department of Radiology, Center for Magnetic Imaging Research, University of Minnesota, Minneapolis, Minnesota, USA
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7
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de Aguiar Vallim TQ, Tarling EJ, Ahn H, Hagey LR, Romanoski CE, Lee RG, Graham MJ, Motohashi H, Yamamoto M, Edwards PA. Abstract 49: The Transcriptional Repressor MafG Regulates Cholesterol Catabolism. Arterioscler Thromb Vasc Biol 2015. [DOI: 10.1161/atvb.35.suppl_1.49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Elevated circulating cholesterol levels is a major risk factor for cardiovascular diseases (CVD), and therefore understanding pathways that affect cholesterol metabolism are important for potential treatment of CVD. The major route for cholesterol excretion is through its catabolism to bile acids. Specific bile acids are also potent signaling molecules that modulate metabolic pathways affecting lipid, glucose and bile acid homeostasis. Bile acids are synthesized from cholesterol in the liver, and the key enzymes involved in bile acid synthesis (
Cyp7a1
,
Cyp8b1
) are regulated transcriptionally by the nuclear receptor FXR. We have identified an FXR-regulated pathway upstream of a transcriptional repressor that controls multiple bile acid metabolism genes. We identify
MafG
as an FXR target gene and show that hepatic MAFG overexpression represses genes of the bile acid synthetic pathway, and modifies the biliary bile acid composition. In contrast, MafG loss-of-function studies cause de-repression of the bile acid genes with concordant changes in biliary bile acid levels. Finally, we identify functional MafG response elements in bile acid metabolism genes using ChIP-Seq analysis. Our studies identify a molecular mechanism for the complex feedback regulation of bile acid synthesis controlled by FXR. The identification of this pathway will likely have important implications in metabolic diseases.
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Affiliation(s)
| | | | - Hannah Ahn
- Sch of Medicine, Div of Cardiology, UCLA, Los Angeles, CA
| | | | | | | | | | - Hozumi Motohashi
- Dept of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku Med Megabank Organization, Sendai, Japan
| | - Masayuki Yamamoto
- Dept of Med Biochemistry, Tohoku Med Megabank Organization, Sendai, Japan
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8
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de Aguiar Vallim TQ, Tarling EJ, Ahn H, Hagey LR, Romanoski CE, Lee RG, Graham MJ, Motohashi H, Yamamoto M, Edwards PA. MAFG is a transcriptional repressor of bile acid synthesis and metabolism. Cell Metab 2015; 21:298-311. [PMID: 25651182 PMCID: PMC4317590 DOI: 10.1016/j.cmet.2015.01.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 11/20/2014] [Accepted: 01/13/2015] [Indexed: 12/12/2022]
Abstract
Specific bile acids are potent signaling molecules that modulate metabolic pathways affecting lipid, glucose and bile acid homeostasis, and the microbiota. Bile acids are synthesized from cholesterol in the liver, and the key enzymes involved in bile acid synthesis (Cyp7a1, Cyp8b1) are regulated transcriptionally by the nuclear receptor FXR. We have identified an FXR-regulated pathway upstream of a transcriptional repressor that controls multiple bile acid metabolism genes. We identify MafG as an FXR target gene and show that hepatic MAFG overexpression represses genes of the bile acid synthetic pathway and modifies the biliary bile acid composition. In contrast, loss-of-function studies using MafG(+/-) mice causes de-repression of the same genes with concordant changes in biliary bile acid levels. Finally, we identify functional MafG response elements in bile acid metabolism genes using ChIP-seq analysis. Our studies identify a molecular mechanism for the complex feedback regulation of bile acid synthesis controlled by FXR.
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Affiliation(s)
- Thomas Q de Aguiar Vallim
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Elizabeth J Tarling
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Hannah Ahn
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Lee R Hagey
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Casey E Romanoski
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | | | | | - Hozumi Motohashi
- Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku Medical Megabank Organization, Sendai 980-8573, Japan
| | - Masayuki Yamamoto
- Department of Medical Biochemistry, Tohoku Medical Megabank Organization, Sendai 980-8573, Japan
| | - Peter A Edwards
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Biological Chemistry, University of California, Los Angeles, CA 90095, USA.
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9
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Miller SL, Richardson K, Edwards PA. The effect of suspended sediment on fertilization success in the urchin Evechinus chloroticus: analysis of experimental data using hierarchical Bayesian methods. Mar Pollut Bull 2014; 88:28-33. [PMID: 25287223 DOI: 10.1016/j.marpolbul.2014.09.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 09/15/2014] [Accepted: 09/17/2014] [Indexed: 06/03/2023]
Abstract
Terrestrial sediments are a significant stressor on coastal ecosystems, with both suspended and deposited sediment having adverse effects on aquatic organisms. However, information on the effect of suspended sediments on fertilization success for urchin species is lacking. Using sediment levels similar to those encountered in situ, a controlled experiment was conducted to test whether suspended sediment affects fertilization success in the urchin Evechinus chloroticus. Analyses used generalized linear mixed models (GLMMs) and hierarchical Bayesian (HB) regression. Both approaches showed a significant decrease in fertilization success with increased suspended sediment levels. Uncertainties in estimates were narrower for HB models, suggesting that this approach has advantages over GLMMs for sparse data problems sometimes encountered in laboratory experiments. Given future global change scenarios, this work is important for predicting the effects of stressors such as sedimentation that may ultimately impact marine populations.
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Affiliation(s)
- S L Miller
- Āwhina VUCEL Incubator, Victoria University of Wellington Coastal Ecology Laboratory (VUCEL), Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Āwhina Research Team, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
| | - K Richardson
- Āwhina Research Team, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - P A Edwards
- Āwhina VUCEL Incubator, Victoria University of Wellington Coastal Ecology Laboratory (VUCEL), Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
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10
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Das S, Edwards PA, Crockett JC, Rogers MJ. Upregulation of endogenous farnesyl diphosphate synthase overcomes the inhibitory effect of bisphosphonate on protein prenylation in Hela cells. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:569-73. [DOI: 10.1016/j.bbalip.2013.12.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 12/12/2013] [Accepted: 12/17/2013] [Indexed: 11/29/2022]
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11
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Rong X, Albert CJ, Hong C, Duerr MA, Chamberlain BT, Tarling EJ, Ito A, Gao J, Wang B, Edwards PA, Jung ME, Ford DA, Tontonoz P. LXRs regulate ER stress and inflammation through dynamic modulation of membrane phospholipid composition. Cell Metab 2013; 18:685-97. [PMID: 24206663 PMCID: PMC3889491 DOI: 10.1016/j.cmet.2013.10.002] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 08/27/2013] [Accepted: 09/26/2013] [Indexed: 12/11/2022]
Abstract
The fatty acyl composition of phospholipids determines the biophysical character of membranes and impacts the function of membrane proteins. Here, we define a nuclear receptor pathway for the dynamic modulation of membrane composition in response to changes in cellular lipid metabolism. Ligand activation of liver X receptors (LXRs) preferentially drives the incorporation of polyunsaturated fatty acids into phospholipids through induction of the remodeling enzyme Lpcat3. Promotion of Lpcat3 activity ameliorates endoplasmic reticulum (ER) stress induced by saturated free fatty acids in vitro or by hepatic lipid accumulation in vivo. Conversely, Lpcat3 knockdown in liver exacerbates ER stress and inflammation. Mechanistically, Lpcat3 modulates inflammation both by regulating inflammatory kinase activation through changes in membrane composition and by affecting substrate availability for inflammatory mediator production. These results outline an endogenous mechanism for the preservation of membrane homeostasis during lipid stress and identify Lpcat3 as an important mediator of LXR effects on metabolism.
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Affiliation(s)
- Xin Rong
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
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12
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Tarling EJ, de Aguiar Vallim TQ, Edwards PA. Role of ABC transporters in lipid transport and human disease. Trends Endocrinol Metab 2013; 24:342-50. [PMID: 23415156 PMCID: PMC3659191 DOI: 10.1016/j.tem.2013.01.006] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 01/16/2013] [Accepted: 01/18/2013] [Indexed: 12/28/2022]
Abstract
Almost half of the 48 human ATP-binding cassette (ABC) transporter proteins are thought to facilitate the ATP-dependent translocation of lipids or lipid-related compounds. Such substrates include cholesterol, plant sterols, bile acids, phospholipids, and sphingolipids. Mutations in a substantial number of the 48 human ABC transporters have been linked to human disease. Indeed the finding that 12 diseases have been associated with abnormal lipid transport and/or homeostasis demonstrates the importance of this family of transporters in cell physiology. This review highlights the role of ABC transporters in lipid transport and movement, in addition to discussing their roles in cellular homeostasis and inherited disorders.
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Affiliation(s)
- Elizabeth J Tarling
- Department of Biological Chemistry, David Geffen School of Medicine at the University of California Los Angeles (UCLA), Los Angeles, CA 90095, USA.
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13
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Abstract
Enzymatic oxidation of cholesterol generates numerous distinct bile acids that function both as detergents that facilitate digestion and absorption of dietary lipids, and as hormones that activate four distinct receptors. Activation of these receptors alters gene expression in multiple tissues, leading to changes not only in bile acid metabolism but also in glucose homeostasis, lipid and lipoprotein metabolism, energy expenditure, intestinal motility and bacterial growth, inflammation, liver regeneration, and hepatocarcinogenesis. This review covers the roles of specific bile acids, synthetic agonists, and their cognate receptors in controlling these diverse functions, as well as their current use in treating human diseases.
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Affiliation(s)
- Thomas Q de Aguiar Vallim
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
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14
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Vallim T, Tarling E, Kim T, Civelek M, Baldan A, Esau C, Edwards PA. Abstract 76: MicroRNA-144 Regulates Hepatic ABCA1 and Plasma HDL Following Activation of the Nuclear Receptor FXR. Arterioscler Thromb Vasc Biol 2013. [DOI: 10.1161/atvb.33.suppl_1.a76] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale
The bile acid receptor Farnesoid-X-Receptor (FXR) regulates many aspects of lipid metabolism by various complex and not fully understood molecular mechanisms. We set out to investigate the molecular mechanisms for FXR-dependent regulation of lipid and lipoprotein metabolism.
Objective
To identify FXR-regulated microRNAs that were subsequently involved in regulating lipid metabolism.
Methods and Results
ATP binding cassette transporter A1 (ABCA1) is a major determinant of plasma High Density Lipoprotein (HDL)-cholesterol levels. Here we show that activation of the nuclear receptor FXR in vivo increases hepatic levels of miR-144, which in turn lower hepatic ABCA1 and plasma HDL levels. We identified two complementary sequences to miR-144 in the 3’ untranslated region (UTR) of ABCA1 mRNA that are necessary for miR-144-dependent regulation. Overexpression of miR-144 in vitro decreased both cellular ABCA1 protein and cholesterol efflux to lipid-poor apolipoprotein A-I (ApoA-I) protein, whilst overexpression in vivo reduced hepatic ABCA1 protein and plasma HDL- cholesterol. Conversely, silencing miR-144 in mice increased hepatic ABCA1 protein and HDL- cholesterol. In addition, we utilized tissue-specific FXR deficient mice to show that induction of miR-144 and FXR-dependent hypolipidemia requires hepatic, but not intestinal FXR. Finally, we identified functional FXR response elements (FXREs) upstream of the miR-144 locus, consistent with direct FXR regulation.
Conclusion
In conclusion, we have identified a pathway involving FXR, miR-144 and ABCA1 that together regulate plasma HDL cholesterol. This pathway may be therapeutically targeted in the future in order to increase HDL levels.
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Affiliation(s)
| | | | - Tammy Kim
- David Geffen Sch of Medicine, UCLA, Los Angeles, CA
| | - Mete Civelek
- David Geffen Sch of Medicine, UCLA, Los Angeles, CA
| | - Angel Baldan
- Edward A. Doisy Dept of Biochemistry and Molecular Biology, Saint Louis Univ, Saint Louis, MO
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15
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Tarling EJ, Gonen A, Que X, Diehl C, Witztum JL, Baldan A, Edwards PA. Abstract 21: Loss of Abcg1 Drives the Site-selective Expansion of B-1 B Cells and Secretion of Atheroprotective Natural Antibodies, in Response to Local Accumulation of Specific Oxidized Lipids. Arterioscler Thromb Vasc Biol 2013. [DOI: 10.1161/atvb.33.suppl_1.a21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The oxidation of LDL, a key event in the pathogenesis of atherosclerosis, generates multiple oxidation-specific neo-epitopes (OSE). These epitopes are recognized by natural germ line IgM antibodies that are secreted by B-1 B cells. Mice lacking the ATP binding cassette (ABC) transporter, ABCG1, develop chronic inflammation in the lungs, associated with the accumulation of lipid (cholesterol, cholesterol ester, phospholipid)-filled cells and cholesterol crystal deposition, which are also characteristic of atherosclerotic lesions. However, hyperlipidemic mice lacking ABCG1 develop smaller atherosclerotic lesions compared to controls. We previously attributed this decrease to increased apoptosis of macrophages within the atherosclerotic lesions of mice lacking ABCG1. We now demonstrate that the lungs of Abcg1-/- mice have increased levels of specific oxidized phospholipids species. Here we show that there is a significant increase in B cell number in the lungs, but not the spleens, of Abcg1-/- mice. Subsequent comparison of B cell subtypes revealed that B-1 B cells, which secrete natural antibodies (NAbs), are significantly expanded in the pleural cavity of Abcg1-/- mice, compared to wild type mice. In addition, we show that the lungs and plasma of Abcg1-/- mice have increased titers of NAbs to OSE, and increased mRNA transcript levels for the known hypervariable (VH) CDR3 region of the atheroprotective EO6/T15 NAb. These data are consistent with an antigen-specific enhanced local production of NAbs in the pleural cavity. These findings suggest that the accumulation of lipids resulting from loss of ABCG1 induces the specific expansion of B-1 B cells, which secrete NAbs that may help protect against the development of atherosclerosis. These data also suggest that Abcg1-/- mice may represent a new model in which to study the protective functions of B-1 B cells/NAbs, and may provide novel targets for pharmacologic intervention and treatment of disease.
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Affiliation(s)
| | - Ayelet Gonen
- Medicine, Univ of California, San Diego, San Diego, CA
| | - Xuchu Que
- Medicine, Univ of California, San Diego, San Diego, CA
| | - Cody Diehl
- Medicine, Univ of California, San Diego, San Diego, CA
| | | | - Angel Baldan
- Biochemistry and Molecular Biology, Saint Louis Univ, Saint Louis, MO
| | - Peter A Edwards
- Medicine-Cardiology, Univ of California, Los Angeles, Los Angeles, CA
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16
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de Aguiar Vallim TQ, Tarling EJ, Kim T, Civelek M, Baldán Á, Esau C, Edwards PA. MicroRNA-144 regulates hepatic ATP binding cassette transporter A1 and plasma high-density lipoprotein after activation of the nuclear receptor farnesoid X receptor. Circ Res 2013; 112:1602-12. [PMID: 23519696 DOI: 10.1161/circresaha.112.300648] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
RATIONALE The bile acid receptor farnesoid X receptor (FXR) regulates many aspects of lipid metabolism by variouscomplex and incompletely understood molecular mechanisms. We set out to investigate the molecular mechanisms for FXR-dependent regulation of lipid and lipoprotein metabolism. OBJECTIVE To identify FXR-regulated microRNAs that were subsequently involved in regulating lipid metabolism. METHODS AND RESULTS ATP binding cassette transporter A1 (ABCA1) is a major determinant of plasma high-density lipoprotein (HDL)-cholesterol levels. Here, we show that activation of the nuclear receptor FXR in vivo increases hepatic levels of miR-144, which in turn lowers hepatic ABCA1 and plasma HDL levels. We identified 2 complementary sequences to miR-144 in the 3' untranslated region of ABCA1 mRNA that are necessary for miR-144-dependent regulation. Overexpression of miR-144 in vitro decreased both cellular ABCA1 protein and cholesterol efflux to lipid-poor apolipoprotein A-I protein, whereas overexpression in vivo reduced hepatic ABCA1 protein and plasma HDL-cholesterol. Conversely, silencing miR-144 in mice increased hepatic ABCA1 protein and HDL-cholesterol. In addition, we used tissue-specific FXR-deficient mice to show that induction of miR-144 and FXR-dependent hypolipidemia requires hepatic, but not intestinal, FXR. Finally, we identified functional FXR response elements upstream of the miR-144 locus, consistent with direct FXR regulation. CONCLUSIONS We have identified a novel pathway involving FXR, miR-144, and ABCA1 that together regulate plasma HDL-cholesterol.
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17
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Bennett BJ, de Aguiar Vallim TQ, Wang Z, Shih DM, Meng Y, Gregory J, Allayee H, Lee R, Graham M, Crooke R, Edwards PA, Hazen SL, Lusis AJ. Trimethylamine-N-oxide, a metabolite associated with atherosclerosis, exhibits complex genetic and dietary regulation. Cell Metab 2013; 17:49-60. [PMID: 23312283 PMCID: PMC3771112 DOI: 10.1016/j.cmet.2012.12.011] [Citation(s) in RCA: 700] [Impact Index Per Article: 63.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 10/25/2012] [Accepted: 12/17/2012] [Indexed: 12/17/2022]
Abstract
Circulating trimethylamine-N-oxide (TMAO) levels are strongly associated with atherosclerosis. We now examine genetic, dietary, and hormonal factors regulating TMAO levels. We demonstrate that two flavin mono-oxygenase family members, FMO1 and FMO3, oxidize trimethylamine (TMA), derived from gut flora metabolism of choline, to TMAO. Further, we show that FMO3 exhibits 10-fold higher specific activity than FMO1. FMO3 overexpression in mice significantly increases plasma TMAO levels while silencing FMO3 decreases TMAO levels. In both humans and mice, hepatic FMO3 expression is reduced in males compared to females. In mice, this reduction in FMO3 expression is due primarily to downregulation by androgens. FMO3 expression is induced by dietary bile acids by a mechanism that involves the farnesoid X receptor (FXR), a bile acid-activated nuclear receptor. Analysis of natural genetic variation among inbred strains of mice indicates that FMO3 and TMAO are significantly correlated, and TMAO levels explain 11% of the variation in atherosclerosis.
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Affiliation(s)
- Brian J Bennett
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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18
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Zhang Y, Ge X, Heemstra LA, Chen WD, Xu J, Smith JL, Ma H, Kasim N, Edwards PA, Novak CM. Loss of FXR protects against diet-induced obesity and accelerates liver carcinogenesis in ob/ob mice. Mol Endocrinol 2012; 26:272-80. [PMID: 22261820 DOI: 10.1210/me.2011-1157] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Farnesoid X receptor (FXR) is known to play important regulatory roles in bile acid, lipid, and carbohydrate metabolism. Aged (>12 months old) Fxr(-/-) mice also develop spontaneous liver carcinomas. In this report, we used three mouse models to investigate the role of FXR deficiency in obesity. As compared with low-density lipoprotein receptor (Ldlr) knockout (Ldlr(-/-)) mice, the Ldlr(-/-)Fxr(-/-) double-knockout mice were highly resistant to diet-induced obesity, which was associated with increased expression of genes involved in energy metabolism in the skeletal muscle and brown adipose tissue. Such a striking effect of FXR deficiency on obesity on an Ldlr(-/-) background led us to investigate whether FXR deficiency alone is sufficient to affect obesity. As compared with wild-type mice, Fxr(-/-) mice showed resistance to diet-induced weight gain. Interestingly, only female Fxr(-/-) mice showed significant resistance to diet-induced obesity, which was accompanied by increased energy expenditure in these mice. Finally, we determined the effect of FXR deficiency on obesity in a genetically obese and diabetic mouse model. We generated ob(-/-)Fxr(-/-) mice that were deficient in both Leptin and Fxr. On a chow diet, ob(-/-)Fxr(-/-) mice gained less body weight and had reduced body fat mass as compared with ob/ob mice. In addition, we observed liver carcinomas in 43% of young (<11 months old) Ob(-/-)Fxr(-/-) mice. Together these data indicate that loss of FXR prevents diet-induced or genetic obesity and accelerates liver carcinogenesis under diabetic conditions.
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Affiliation(s)
- Yanqiao Zhang
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, Ohio 44272, USA.
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19
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Tarling EJ, Edwards PA. Dancing with the sterols: critical roles for ABCG1, ABCA1, miRNAs, and nuclear and cell surface receptors in controlling cellular sterol homeostasis. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:386-95. [PMID: 21824529 DOI: 10.1016/j.bbalip.2011.07.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 07/13/2011] [Accepted: 07/15/2011] [Indexed: 12/29/2022]
Abstract
ATP binding cassette (ABC) transporters represent a large and diverse family of proteins that transport specific substrates across a membrane. The importance of these transporters is illustrated by the finding that inactivating mutations within 17 different family members are known to lead to specific human diseases. Clinical data from humans and/or studies with mice lacking functional transporters indicate that ABCA1, ABCG1, ABCG4, ABCG5 and ABCG8 are involved in cholesterol and/or phospholipid transport. This review discusses the multiple mechanisms that control cellular sterol homeostasis, including the roles of microRNAs, nuclear and cell surface receptors and ABC transporters, with particular emphasis on recent findings that have provided insights into the role(s) of ABCG1. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Affiliation(s)
- Elizabeth J Tarling
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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20
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Yin L, Ma H, Ge X, Edwards PA, Zhang Y. Hepatic hepatocyte nuclear factor 4α is essential for maintaining triglyceride and cholesterol homeostasis. Arterioscler Thromb Vasc Biol 2010; 31:328-36. [PMID: 21071704 DOI: 10.1161/atvbaha.110.217828] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Loss-of-function mutations in human hepatocyte nuclear factor 4α (HNF4α) are associated with maturity-onset diabetes of the young and lipid disorders. However, the mechanisms underlying the lipid disorders are poorly understood. In this study, we determined the effect of acute loss or augmentation of hepatic HNF4α function on lipid homeostasis. METHODS AND RESULTS We generated an adenovirus expressing LacZ (Ad-shLacZ) or short hairpin RNA of Hnf4α (Ad-shHnf4α). Tail vain injection of C57BL/6J mice with Ad-shHnf4α reduced hepatic Hnf4α expression and resulted in striking phenotypes, including the development of fatty liver and a >80% decrease in plasma levels of triglycerides, total cholesterol, and high-density lipoprotein cholesterol. These latter changes were associated with reduced hepatic lipogenesis and impaired very-low-density lipoprotein secretion. Deficiency in hepatic Hnf4α did not affect intestinal cholesterol absorption despite decreased expression of genes involved in bile acid synthesis. Consistent with the loss-of-function data, overexpression of Hnf4α induced numerous genes involved in lipid metabolism in isolated primary hepatocytes. Interestingly, many of these HNF4α-regulated genes were not induced in wild-type mice that overexpressed hepatic Hnf4α. Because of selective gene regulation, mice overexpressing hepatic Hnf4α had unchanged plasma triglyceride levels and decreased plasma cholesterol levels. CONCLUSIONS Loss of hepatic HNF4α results in severe lipid disorder as a result of dysregulation of multiple genes involved in lipid metabolism. In contrast, augmentation of hepatic HNF4α activity lowers plasma cholesterol levels but has no effect on plasma triglyceride levels because of selective gene regulation. Our data indicate that hepatic HNF4α is essential for controlling the basal expression of numerous genes involved in lipid metabolism and is indispensable for maintaining normal lipid homeostasis.
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Affiliation(s)
- Liya Yin
- Department of Integrative Medical Sciences, Northeastern Ohio Universities College of Medicine, 4209 State Rte. 44, Rootstown, OH 44272, USA
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21
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Jiang YJ, Lu B, Tarling EJ, Kim P, Man MQ, Crumrine D, Edwards PA, Elias PM, Feingold KR. Regulation of ABCG1 expression in human keratinocytes and murine epidermis. J Lipid Res 2010; 51:3185-95. [PMID: 20675829 DOI: 10.1194/jlr.m006445] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
ABCG1, a member of the ATP binding cassette superfamily, facilitates the efflux of cholesterol from cells to HDL. In this study, we demonstrate that ABCG1 is expressed in cultured human keratinocytes and murine epidermis, and induced during keratinocyte differentiation, with increased levels in the outer epidermis. ABCG1 is regulated by liver X receptor (LXR) and peroxisome proliferator-activated receptor-δ (PPAR-δ) activators, cellular sterol levels, and acute barrier disruption. Both LXR and PPAR-δ activators markedly stimulate ABCG1 expression in a dose- and time-dependent fashion. PPAR-γ activators also increase ABCG1 expression, but to a lesser degree. In contrast, activators of PPAR-α, retinoic acid receptor, retinoid X receptor, and vitamin D receptor do not alter ABCG1 expression. In response to increased intracellular sterol levels, ABCG1 expression increases, whereas inhibition of cholesterol biosynthesis decreases ABCG1 expression. In vivo, ABCG1 is stimulated 3-6 h after acute barrier disruption by either tape stripping or acetone treatment, an increase that can be inhibited by occlusion, suggesting a potential role of ABCG1 in permeability barrier homeostasis. Although Abcg1-null mice display normal epidermal permeability barrier function and gross morphology, abnormal lamellar body (LB) contents and secretion leading to impaired lamellar bilayer formation could be demonstrated by electron microscopy, indicating a potential role of ABCG1 in normal LB formation and secretion.
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Affiliation(s)
- Yan J Jiang
- Metabolism Section, Veterans Affairs Medical Center, Northern California Institute for Research and Education, University of California at San Francisco, San Francisco, CA 94121, USA.
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22
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Lee FY, de Aguiar Vallim TQ, Chong HK, Zhang Y, Liu Y, Jones SA, Osborne TF, Edwards PA. Activation of the farnesoid X receptor provides protection against acetaminophen-induced hepatic toxicity. Mol Endocrinol 2010; 24:1626-36. [PMID: 20573685 DOI: 10.1210/me.2010-0117] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The nuclear receptor, farnesoid X receptor (FXR, NR1H4), is known to regulate cholesterol, bile acid, lipoprotein, and glucose metabolism. In the current study, we provide evidence to support a role for FXR in hepatoprotection from acetaminophen (APAP)-induced toxicity. Pharmacological activation of FXR induces the expression of several genes involved in phase II and phase III xenobiotic metabolism in wild-type, but not Fxr(-/-) mice. We used chromatin immunoprecipitation-based genome-wide response element analyses coupled with luciferase reporter assays to identify functional FXR response elements within promoters, introns, or intragenic regions of these genes. Consistent with the observed transcriptional changes, FXR gene dosage is positively correlated with the degree of protection from APAP-induced hepatotoxicity in vivo. Further, we demonstrate that pretreatment of wild-type mice with an FXR-specific agonist provides significant protection from APAP-induced hepatotoxicity. Based on these findings, we propose that FXR plays a role in hepatic xenobiotic metabolism and, when activated, provides hepatoprotection against toxins such as APAP.
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Affiliation(s)
- Florence Ying Lee
- Department of Biological Chemistry, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, California 90095, USA
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23
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Chong HK, Infante AM, Seo YK, Jeon TI, Zhang Y, Edwards PA, Xie X, Osborne TF. Genome-wide interrogation of hepatic FXR reveals an asymmetric IR-1 motif and synergy with LRH-1. Nucleic Acids Res 2010; 38:6007-17. [PMID: 20483916 PMCID: PMC2952856 DOI: 10.1093/nar/gkq397] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We used mouse hepatic chromatin enriched with an FXR antibody and chromatin immunoprecipitation-sequencing (ChIP-seq) to evaluate FXR binding on a genome-wide scale. This identified 1656 FXR-binding sites and 10% were located within 2 kb of a transcription start site which is much higher than predicted by random occurrence. A motif search uncovered a canonical nuclear receptor IR-1 site, consistent with in vitro DNA-binding studies reported previously. A separate nuclear receptor half-site for monomeric receptors such as LRH-1 was co-enriched and FXR activation of four newly identified promoters was significantly augmented by an LRH-1 expression vector in a co-transfection assay. There were 1038 genes located within 20 kb of a peak and a gene set enrichment analysis showed that genes identified by our ChIP-seq analysis are highly correlated with genes activated by an FXR-VP16 adenovirus in primary mouse hepatocytes providing functional relevance to the genome-wide binding study. Gene Ontology analysis showed FXR-binding sites close to many genes in lipid, fatty acid and steroid metabolism. Other broad gene clusters related to metabolism, transport, signaling and glycolysis were also significantly enriched. Thus, FXR may have a much wider role in cellular metabolism than previously appreciated.
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Affiliation(s)
- Hansook Kim Chong
- Department of Molecular Biology and Biochemistry, Institute for Genomics and Bioinformatics, University of California, Irvine, CA 92697, USA
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Tarling EJ, Bojanic DD, Tangirala RK, Wang X, Lovgren-Sandblom A, Lusis AJ, Bjorkhem I, Edwards PA. Impaired development of atherosclerosis in Abcg1-/- Apoe-/- mice: identification of specific oxysterols that both accumulate in Abcg1-/- Apoe-/- tissues and induce apoptosis. Arterioscler Thromb Vasc Biol 2010; 30:1174-80. [PMID: 20299684 DOI: 10.1161/atvbaha.110.205617] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
OBJECTIVE To generate Abcg1(-/-) Apoe(-/-) mice to understand the mechanism and cell types involved in changes in atherosclerosis after loss of ABCG1. METHODS AND RESULTS ABCG1 is highly expressed in macrophages and endothelial cells, 2 cell types that play important roles in the development of atherosclerosis. Abcg1(-/-) Apoe(-/-) and Apoe(-/-) mice and recipient Apoe(-/-) mice that had undergone transplantation with bone marrow from Apoe(-/-) or Abcg1(-/-) Apoe(-/-) mice were fed a Western diet for 12 or 16 weeks before quantification of atherosclerotic lesions. These studies demonstrated that loss of ABCG1 from all tissues, or from only hematopoietic cells, was associated with significantly smaller lesions that contained increased numbers of TUNEL- and cleaved caspase 3-positive apoptotic Abcg1(-/-) macrophages. We also identified specific oxysterols that accumulate in the brains and macrophages of the Abcg1(-/-) Apoe(-/-) mice. These oxysterols promoted apoptosis and altered the expression of proapoptotic genes when added to macrophages in vitro. CONCLUSIONS Loss of ABCG1 from all tissues or from only hematopoietic cells results in smaller atherosclerotic lesions populated with increased apoptotic macrophages, by processes independent of ApoE. Specific oxysterols identified in tissues of Abcg1(-/-) Apoe(-/-) mice may be critical because they induce macrophage apoptosis and the expression of proapoptotic genes.
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Affiliation(s)
- Elizabeth J Tarling
- Department of Biological Chemistry, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, CA 90095-1737, USA
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25
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Bojanic DD, Tarr PT, Gale GD, Smith DJ, Bok D, Chen B, Nusinowitz S, Lövgren-Sandblom A, Björkhem I, Edwards PA. Differential expression and function of ABCG1 and ABCG4 during development and aging. J Lipid Res 2010. [PMID: 19633360 DOI: 10.1194/jlr.m900250-jlr200] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ABCG1 and ABCG4 are highly homologous members of the ATP binding cassette (ABC) transporter family that regulate cellular cholesterol homeostasis. In adult mice, ABCG1 is known to be expressed in numerous cell types and tissues, whereas ABCG4 expression is limited to the central nervous system (CNS). Here, we show significant differences in expression of these two transporters during development. Examination of beta-galactosidase-stained tissue sections from Abcg1(-/-)LacZ and Abcg4(-/-)LacZ knockin mice shows that ABCG4 is highly but transiently expressed both in hematopoietic cells and in enterocytes during development. In contrast, ABCG1 is expressed in macrophages and in endothelial cells of both embryonic and adult liver. We also show that ABCG1 and ABCG4 are both expressed as early as E12.5 in the embryonic eye and developing CNS. Loss of both ABCG1 and ABCG4 results in accumulation in the retina and/or brain of oxysterols, in altered expression of liver X receptor and sterol-regulatory element binding protein-2 target genes, and in a stress response gene. Finally, behavioral tests show that Abcg4(-/-) mice have a general deficit in associative fear memory. Together, these data indicate that loss of ABCG1 and/or ABCG4 from the CNS results in changes in metabolic pathways and in behavior.
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Affiliation(s)
- Dragana D Bojanic
- Department of Biological Chemistry at UCLA Los Angeles, CA 90095, USA
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Zhang Y, Yin L, Anderson J, Ma H, Gonzalez FJ, Willson TM, Edwards PA. Identification of novel pathways that control farnesoid X receptor-mediated hypocholesterolemia. J Biol Chem 2009; 285:3035-43. [PMID: 19996107 DOI: 10.1074/jbc.m109.083899] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Farnesoid X receptor (FXR) plays important regulatory roles in bile acid, lipoprotein, and glucose homeostasis. Here, we have utilized Fxr(-/-) mice and mice deficient in scavenger receptor class B type I (SR-BI), together with an FXR-specific agonist and adenovirus expressing hepatocyte nuclear factor 4alpha or constitutively active FXR, to identify the mechanisms by which activation of FXR results in hypocholesterolemia. We identify a novel pathway linking FXR to changes in hepatic p-JNK, hepatocyte nuclear factor 4alpha, and finally SR-BI. Importantly, we demonstrate that the FXR-dependent increase in SR-BI results in both hypocholesterolemia and an increase in reverse cholesterol transport, a process involving the transport of cholesterol from peripheral macrophages to the liver for excretion into the feces. In addition, we demonstrate that FXR activation also induces an SR-BI-independent increase in reverse cholesterol transport and reduces intestinal cholesterol absorption. Together, these data indicate that FXR is a promising therapeutic target for treatment of hypercholesterolemia and coronary heart disease.
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Affiliation(s)
- Yanqiao Zhang
- Department of Integrative Medical Sciences, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio 44272, USA.
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Abstract
In this issue of Cell Metabolism, Thomas et al. (2009) show that specific activation of the bile-acid-activated G protein-coupled receptor TGR5 improves pancreatic and hepatic function and impairs the development of obesity following administration of a high-fat diet.
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Affiliation(s)
- Thomas Quad de Aguiar Vallim
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, BSRB Room 310, Los Angeles, CA 90095, USA
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Tarr PT, Tarling EJ, Bojanic DD, Edwards PA, Baldán Á. Emerging new paradigms for ABCG transporters. Biochim Biophys Acta 2009; 1791:584-93. [PMID: 19416657 PMCID: PMC2698934 DOI: 10.1016/j.bbalip.2009.01.007] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 01/13/2009] [Accepted: 01/13/2009] [Indexed: 12/14/2022]
Abstract
Every cell is separated from its external environment by a lipid membrane. Survival depends on the regulated and selective transport of nutrients, waste products and regulatory molecules across these membranes, a process that is often mediated by integral membrane proteins. The largest and most diverse of these membrane transport systems is the ATP binding cassette (ABC) family of membrane transport proteins. The ABC family is a large evolutionary conserved family of transmembrane proteins (>250 members) present in all phyla, from bacteria to Homo sapiens, which require energy in the form of ATP hydrolysis to transport substrates against concentration gradients. In prokaryotes the majority of ABC transporters are involved in the transport of nutrients and other macromolecules into the cell. In eukaryotes, with the exception of the cystic fibrosis transmembrane conductance regulator (CFTR/ABCC7), ABC transporters mobilize substrates from the cytoplasm out of the cell or into specific intracellular organelles. This review focuses on the members of the ABCG subfamily of transporters, which are conserved through evolution in multiple taxa. As discussed below, these proteins participate in multiple cellular homeostatic processes, and functional mutations in some of them have clinical relevance in humans.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily G
- ATP Binding Cassette Transporter, Subfamily G, Member 1
- ATP Binding Cassette Transporter, Subfamily G, Member 2
- ATP Binding Cassette Transporter, Subfamily G, Member 5
- ATP Binding Cassette Transporter, Subfamily G, Member 8
- ATP-Binding Cassette Transporters/classification
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- ATP-Binding Cassette Transporters/physiology
- Animals
- Biological Transport
- Lipoproteins/genetics
- Lipoproteins/metabolism
- Lipoproteins/physiology
- Mice
- Mice, Knockout
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Affiliation(s)
- Paul T. Tarr
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
| | - Elizabeth J. Tarling
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Dragana D. Bojanic
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Peter A. Edwards
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Molecular Biology Institute, UCLA, Los Angeles, CA 90095, USA
| | - Ángel Baldán
- Edward A. Doisy Department of Biochemistry and Molecular Biology, DRC 321, Saint Louis University School of Medicine, 1100 S. Grand Blvd., St. Louis, MO 63104, USA
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Anisfeld AM, Kast-Woelbern HR, Meyer ME, Jones SA, Zhang Y, Williams KJ, Willson T, Edwards PA. Syndecan-1 expression is regulated in an isoform-specific manner by the farnesoid-X receptor. VOLUME 278 (2003) PAGES 20420-20428. J Biol Chem 2009. [DOI: 10.1016/s0021-9258(20)32622-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Howarth KD, Batty EM, Beavis JC, Blood KA, Newman S, Ng B, Pole JC, Chua Y, Ichimura K, Collins VP, Project CG, Chin S, Caldas C, Carter NP, Edwards PA. Chromosome translocations and fusion genes in breast cancer. Cancer Res 2009. [DOI: 10.1158/0008-5472.sabcs-2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Abstract #2021
Background: Little is known about chromosome translocations in the common epithelial cancers such as breast cancer, in spite of the central role played by translocations and consequent gene fusions in haematopoietic cancers.
 Methods: We present a comprehensive analysis by array painting of the chromosome translocations of four breast cancer cell lines, DU4475, HCC1806, HCC1187 and ZR-75-30. In array painting chromosomes are isolated by flow cytometry, amplified and hybridized to DNA microarrays. All breakpoints, totalling nearly 250, were mapped to at least 1Mb resolution and most balanced breakpoints were mapped to about 2kb resolution using custom oligonucleotide arrays. The remaining unbalanced breakpoints were mapped to around 20kb by identifying copy number steps in Affymetrix SNP6 array hybrizations obtained by the Sanger Institute's Cancer Genome Project. Breast tumours in parraffin section in tissue microarrays were screened by FISH to see whether selected breakpoints found in the cell lines are present in breast tumours.
 Results: We found at least 12 reciprocal translocations in the four cell lines, substantially more than expected, and many more rearrangements were balanced for at least one participating chromosome. Many of the breakpoints were within or adjacent to cancer-relevant genes, and three of the translocations have already been shown to form fusion transcripts, RIF1-PKD1L1, PUM1-TRERF1 and TAX1BP1-AHCY. For selected genes targetted by the translocations, about 100 breast tumours were screened for breaks. Breaks were found in two to six cases for several of the genes, confirming that some of them were broken in breast tumours. For example two cases of unbalanced breakage were identified in PKD1L1, and these were confirmed by array-CGH.
 Discussion: Our results suggest that breast cancers have fusion genes, and support the emerging view that chromosome rearrangements are likely to play a significant role in common epithelial cancers.
Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2021.
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Affiliation(s)
- KD Howarth
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - EM Batty
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - JC Beavis
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - KA Blood
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - S Newman
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - B Ng
- 2 Sanger Institute, Hinxton, United Kingdom
| | - JC Pole
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Y Chua
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - K Ichimura
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - VP Collins
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
| | - CG Project
- 2 Sanger Institute, Hinxton, United Kingdom
| | - S Chin
- 3 Cancer Research UK Cambridge Research Institute, Cambridge, United Kingdom
| | - C Caldas
- 3 Cancer Research UK Cambridge Research Institute, Cambridge, United Kingdom
| | - NP Carter
- 2 Sanger Institute, Hinxton, United Kingdom
| | - PA Edwards
- 1 Pathology, University of Cambridge, Cambridge, United Kingdom
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Attie AD, Witztum JL, Edwards PA, Lusis JA. In memoriam: Roger A. Davis (1945-2008). J Lipid Res 2009; 49:2279-80. [PMID: 19123270 DOI: 10.1194/jlr.e800017-jlr200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Abstract
Mammalian cells have developed various responses to minimize accumulation of unesterified cholesterol, as the latter can result in cell toxicity and death [reviewed in this edition by Björkhem (Björkhem, I. 2009. Are side-chain oxidized oxysterols regulators also in vivo? J. Lipid Res. In press)]. These responses include esterification to sequester excess sterol in intracellular lipid droplets, repression of both cholesterol synthesis and LDL receptor expression (thus reducing endocytosis of LDL), and induction of a panoply of genes that promote sterol efflux and affect lipid metabolism. The nuclear receptor liver-X-receptor (LXR) functions as a cellular "sterol sensor" and plays a critical role in these latter transcriptional changes [reviewed in this edition by Glass (Shibata, N., and Glass C, K. 2009. Regulation of macrophage function in inflammation and atherosclerosis. J. Lipid Res. In press)]. Activation of LXR by either endogenous oxysterols or synthetic agonists induces the expression of many genes, including those encoding ATP-binding cassette (ABC) transporters ABCA1, ABCG1, ABCG5, and ABCG8. As discussed below, these four proteins function to promote sterol efflux from cells.
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Affiliation(s)
- Angel Baldán
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
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Abstract
ABCG1, a member of the ATP-binding cassette transporter superfamily, is highly expressed in multiple cells of the lung. Loss of ABCG1 results in severe pulmonary lipidosis in mice, with massive deposition of cholesterol in both alveolar macrophages and type 2 cells and the accumulation of excessive surfactant phospholipids. These observations are consistent with ABCG1 controlling cellular sterol metabolism. Herein, we report on the progressive and chronic inflammatory process that accompanies the lipidosis in the lungs of Abcg1-/- mice. Compared with wild-type animals, the lungs of aged chow-fed mice deficient in ABCG1 show distinctive signs of inflammation that include macrophage accumulation, lymphocytic infiltration, hemorrhage, eosinophilic crystals, and elevated levels of numerous cytokines and cytokine receptors. Analysis of bronchoalveolar lavages obtained from Abcg1-/- mice revealed elevated numbers of foamy macrophages and leukocytes and the presence of multiple markers of inflammation including crystals of chitinase-3-like proteins. These data suggest that cholesterol and/or cholesterol metabolites that accumulate in Abcg1-/- lungs can trigger inflammatory signaling pathways. Consistent with this hypothesis, the expression of a number of cytokines was found to be significantly increased following increased cholesterol delivery to either primary peritoneal macrophages or Raw264.7 cells. Finally, cholesterol loading of primary mouse macrophages induced cytokine mRNAs to higher levels in Abcg1-/-, as compared with wild-type cells. These results demonstrate that ABCG1 plays critical roles in pulmonary homeostasis, balancing both lipid/cholesterol metabolism and inflammatory responses.
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Affiliation(s)
- Angel Baldán
- Department of Biological Chemistry, Center for Health Sciences, David Geffen School of Medicine, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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Bensinger SJ, Bradley MN, Joseph SB, Zelcer N, Janssen EM, Hausner MA, Shih R, Parks JS, Edwards PA, Jamieson BD, Tontonoz P. LXR signaling couples sterol metabolism to proliferation in the acquired immune response. Cell 2008; 134:97-111. [PMID: 18614014 PMCID: PMC2626438 DOI: 10.1016/j.cell.2008.04.052] [Citation(s) in RCA: 520] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 02/26/2008] [Accepted: 04/21/2008] [Indexed: 12/13/2022]
Abstract
Cholesterol is essential for membrane synthesis; however, the mechanisms that link cellular lipid metabolism to proliferation are incompletely understood. We demonstrate here that cellular cholesterol levels in dividing T cells are maintained in part through reciprocal regulation of the LXR and SREBP transcriptional programs. T cell activation triggers induction of the oxysterol-metabolizing enzyme SULT2B1, consequent suppression of the LXR pathway for cholesterol transport, and promotion of the SREBP pathway for cholesterol synthesis. Ligation of LXR during T cell activation inhibits mitogen-driven expansion, whereas loss of LXRbeta confers a proliferative advantage. Inactivation of the sterol transporter ABCG1 uncouples LXR signaling from proliferation, directly linking sterol homeostasis to the antiproliferative action of LXR. Mice lacking LXRbeta exhibit lymphoid hyperplasia and enhanced responses to antigenic challenge, indicating that proper regulation of LXR-dependent sterol metabolism is important for immune responses. These results implicate LXR signaling in a metabolic checkpoint that modulates cell proliferation and immunity.
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Affiliation(s)
- Steven J Bensinger
- Howard Hughes Medical Institute, Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90049, USA
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Abstract
Farnesoid X receptor (FXR), a member of the nuclear receptor superfamily, has been shown to be important in controlling numerous metabolic pathways; these include roles in maintaining bile acid, lipid and glucose homeostasis, in preventing intestinal bacterial infection and gallstone formation and in modulating liver regeneration and tumorigenesis. The accumulating data suggest that FXR may be a pharmaceutical target for the treatment of certain metabolic diseases.
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Affiliation(s)
- Yanqiao Zhang
- Department of Biological Chemistry, University of California at Los Angeles, 47-105 CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
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Tarr PT, Edwards PA. ABCG1 and ABCG4 are coexpressed in neurons and astrocytes of the CNS and regulate cholesterol homeostasis through SREBP-2. J Lipid Res 2007; 49:169-82. [PMID: 17916878 DOI: 10.1194/jlr.m700364-jlr200] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Here, we describe the initial characterization of Abcg4(-/-) mice and identify overlapping functions of ABCG4 and ABCG1 in the brain. Histological examination of tissues from Abcg4(+/-)/nlsLacZ and Abcg1(+/-)/nlsLacZ mice demonstrates that coexpression of Abcg4 and Abcg1 is restricted to neurons and astrocytes of the central nervous system (CNS). Interestingly, Abcg4 mRNA is undetectable outside the CNS, in contrast with the broad tissue and cellular expression of Abcg1. We also used primary astrocytes, microglia, neurons, and macrophages to demonstrate that the expression of Abcg1, but not Abcg4, is induced after the activation of liver X receptor. Cellular localization studies demonstrated that both proteins reside in RhoB-positive endocytic vesicle membranes. Furthermore, overexpression of either ABCG1 or ABCG4 increased the processing of sterol-regulatory element binding protein 2 (SREBP-2) to the transcriptionally active protein, thus accounting for the observed increase in the expression of SREBP-2 target genes and cholesterol synthesis. Consistent with these latter results, we show that the expression levels of the same SREBP-2 target genes are repressed in the brains of Abcg1(-/-) and, to a lesser extent, Abcg4(-/-) mice. Based on the results of the current study, we propose that ABCG1 and ABCG4 mediate the intracellular vesicular transport of cholesterol/sterols within both neurons and astrocytes to regulate cholesterol transport in the brain.
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Affiliation(s)
- Paul T Tarr
- Department of Biological Chemistry, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
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Lee H, Hubbert ML, Osborne TF, Woodford K, Zerangue N, Edwards PA. Regulation of the sodium/sulfate co-transporter by farnesoid X receptor alpha. J Biol Chem 2007; 282:21653-61. [PMID: 17545158 DOI: 10.1074/jbc.m700897200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fxralpha is known to regulate a variety of metabolic processes, including bile acid, cholesterol, and carbohydrate metabolism. In this study, we show direct evidence that Fxralpha is a key player in maintaining sulfate homeostasis. We identified and characterized the sodium/sulfate co-transporter (NaS-1; Slc13a1) as an Fxralpha target gene expressed in the kidney and intestine. Electromobility shift assays, chromatin immunoprecipitation, and promoter reporter studies identified a single functional Fxralpha response element in the second intron of the mouse Slc13a1 gene. Treatment of wild-type mice with GW4064, a synthetic Fxralpha agonist, induced Slc13a1 mRNA in the intestine and kidney. Slc13a1 mRNA was also induced in the kidney and intestine of wild-type, but not Fxralpha-/- mice, after treatment with the hepatotoxin alpha-naphthylisothiocyanate, which is known to result in elevated blood bile acid levels. Finally, we observed a decrease in Slc13a1 mRNA in the kidney and intestine of Fxralpha-/- mice and a corresponding increase in urinary excretion of free sulfates as compared with wild-type mice. These results demonstrate that mouse Slc13a1 is a novel Fxralpha target gene expressed in the kidney and intestine and that in the absence of Fxralpha, mice waste sulfate into the urine. Thus, Fxralpha is necessary for normal sulfate homeostasis in vivo.
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Affiliation(s)
- Hans Lee
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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38
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Abstract
Activation of the farnesoid X receptor (FXRalpha) affects genes controlling many pathways, including those involved in bile acid and glucose homeostasis. Here we report that a critical gene involved in cholesterol homeostasis, Insig-2, was induced when mice or cultured cells were treated with FXRalpha agonists or infected with constitutively active FXRalpha. No such induction was observed in agonist-treated FXRalpha-/- mice. Further analysis, which included EMSAs, reporter gene activation, and chromatin immunoprecipitation, identified two functional FXRalpha response elements within intron 2 of the mouse Insig-2 gene. In addition to increasing hepatic Insig-2 protein levels in wild-type mice, FXRalpha activation also reduced lanosterol 14alpha-demethylase mRNA levels and 3-hydroxy-3-methylglutaryl-coenzyme A reductase protein levels. Together, these changes likely account for the decrease in cholesterol synthesis observed after activation of FXR in primary hepatocytes. In conclusion, the current study links hepatic FXRalpha activation to regulation of genes involved in cholesterol synthesis.
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Affiliation(s)
- Melissa L Hubbert
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, California 90095, USA
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39
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Lee FY, Lee H, Hubbert ML, Edwards PA, Zhang Y. FXR, a multipurpose nuclear receptor. Trends Biochem Sci 2006; 31:572-80. [PMID: 16908160 DOI: 10.1016/j.tibs.2006.08.002] [Citation(s) in RCA: 259] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 07/14/2006] [Accepted: 08/03/2006] [Indexed: 12/20/2022]
Abstract
The farnesoid X receptor (FXR) is a ligand-activated transcription factor and a member of the nuclear receptor superfamily. In the past six years, remarkable inroads have been made into determining the functional importance of FXR. This receptor has been shown to have crucial roles in controlling bile acid homeostasis, lipoprotein and glucose metabolism, hepatic regeneration, intestinal bacterial growth and the response to hepatotoxins. Thus, the development of FXR agonists might prove useful for the treatment of diabetes, cholesterol gallstones, and hepatic and intestinal toxicity.
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Affiliation(s)
- Florence Y Lee
- Department of Biological Chemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
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Baldán A, Tarr P, Vales CS, Frank J, Shimotake TK, Hawgood S, Edwards PA. Deletion of the transmembrane transporter ABCG1 results in progressive pulmonary lipidosis. J Biol Chem 2006; 281:29401-10. [PMID: 16887795 DOI: 10.1074/jbc.m606597200] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We show that mice lacking the ATP-binding cassette transmembrane transporter ABCG1 show progressive and age-dependent severe pulmonary lipidosis that recapitulates the phenotypes of different respiratory syndromes in both humans and mice. The lungs of chow-fed Abcg1(-/-) mice, >6-months old, exhibit extensive subpleural cellular accumulation, macrophage, and pneumocyte type 2 hypertrophy, massive lipid deposition in both macrophages and pneumocytes and increased levels of surfactant. No such abnormalities are observed at 3 months of age. However, gene expression profiling reveals significant changes in the levels of mRNAs encoding key genes involved in lipid metabolism in both 3- and 8-month-old Abcg1(-/-) mice. These data suggest that the lungs of young Abcg1(-/-) mice maintain normal lipid levels by repressing lipid biosynthetic pathways and that such compensation is inadequate as the mice mature. Studies with A-549 cells, a model for pneumocytes type 2, demonstrate that overexpression of ABCG1 specifically stimulates the efflux of cellular cholesterol by a process that is dependent upon phospholipid secretion. In addition, we demonstrate that Abcg1(-/-), but not wild-type macrophages, accumulate cholesterol ester droplets when incubated with surfactant. Together, these data provide a mechanism to explain the lipid accumulation in the lungs of Abcg1(-/-)mice. In summary, our results demonstrate that ABCG1 plays essential roles in pulmonary lipid homeostasis.
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Affiliation(s)
- Angel Baldán
- Department of Biological Chemistry, University o California, Los Angeles 90095, USA
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Baldán A, Pei L, Lee R, Tarr P, Tangirala RK, Weinstein MM, Frank J, Li AC, Tontonoz P, Edwards PA. Impaired development of atherosclerosis in hyperlipidemic Ldlr-/- and ApoE-/- mice transplanted with Abcg1-/- bone marrow. Arterioscler Thromb Vasc Biol 2006; 26:2301-7. [PMID: 16888235 DOI: 10.1161/01.atv.0000240051.22944.dc] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE The lungs of Abcg1-/- mice accumulate macrophage foam cells that contain high levels of unesterified and esterified cholesterol, consistent with a role for ABCG1 in facilitating the efflux of cholesterol from macrophages to high-density lipoprotein (HDL) and other exogenous sterol acceptors. Based on these observations, we investigated whether loss of ABCG1 affects foam cell deposition in the artery wall and the development of atherosclerosis. METHODS AND RESULTS Bone marrow from wild-type or Abcg1-/- mice was transplanted into Ldlr-/- or ApoE-/- mice. After administration of a high-fat/high-cholesterol diet, plasma and tissue lipid levels and atherosclerotic lesion size were quantified and compared. Surprisingly, transplantation of Abcg1-/- bone marrow cells resulted in a significant reduction in lesion size in both mouse models, despite the fact that lipid levels increased in the lung, spleen, and kidney. Lesions of Ldlr-/- mice transplanted with Abcg1-/- cells contained increased numbers of apoptotic cells. Consistent with this observation, in vitro studies demonstrated that Abcg1-/- macrophages were more susceptible to oxidized low-density lipoprotein (ox-LDL)-dependent apoptosis than Abcg1+/+ cells. CONCLUSIONS Diet-induced atherosclerosis is impaired when atherosclerotic-susceptible mice are transplanted with Abcg1-/- bone marrow. The demonstration that Abcg1-/- macrophages undergo accelerated apoptosis provides a mechanism to explain the decrease in the atherosclerotic lesions.
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Affiliation(s)
- Angel Baldán
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, 10833 Le Conte Ave., Los Angeles, CA 90095, USA
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42
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Abstract
OBJECTIVE Based on the observation that Fxr-/- mice exhibit a proatherogenic lipoprotein profile, we investigated the role of FXR in the development of atherosclerosis. METHODS AND RESULTS Administration of a western diet to Fxr-/- mice or wild-type mice does not result in the development of significant atherosclerotic lesions. Consequently we generated Fxr-/- Ldlr-/- (DKO) mice and compared lesion development with Ldlr-/- mice. After 16 weeks on a Western diet, en face analysis of the aorta indicated that the male DKO mice had reduced atherosclerotic lesions as compared with Ldlr-/- mice. Plasma low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels were reduced by 40% to 50%, whereas triglyceride levels increased 4-fold in the male DKO mice. Finally, peritoneal macrophages freshly isolated from male DKO mice had reduced expression of CD36 mRNA and decreased neutral lipid accumulation, as compared with Ldlr-/- mice. CONCLUSIONS FXR deficiency in male, but not female, Ldlr-/- mice results in a reduction in the size of atherosclerotic lesions in the aorta. The reduction in atherosclerosis may result from a decrease in plasma low-density lipoprotein cholesterol, coupled with reduced expression of CD36 in macrophages of DKO mice.
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Affiliation(s)
- Yanqiao Zhang
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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43
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Abstract
PURPOSE OF REVIEW This review briefly discusses the ATP-binding cassette transporter G (ABCG) family members and emphasizes recent studies that identify ABCG1 as a key regulator of cellular lipid homeostasis. RECENT FINDINGS The in-vivo importance of ABCG1 has recently been demonstrated with both loss-of-function and gain-of-function studies in mice. Administration of a diet high in both fat and cholesterol to ABCG1 mice results in massive cholesterol accumulation in both the liver and lungs. In contrast, lipid accumulation is greatly attenuated in transgenic mice that express both the murine and human ABCG1 genes. Despite the observed tissue lipid accumulation, plasma lipid levels and lipoprotein cholesterol distribution are not significantly different between wild-type, ABCG1, and hABCG1 transgenic mice. Other studies show that ABCG1 expression is induced following activation of the nuclear receptor LXR and that over expression of ABCG1 results in increased efflux of cellular cholesterol to HDL or phospholipid vesicles. SUMMARY The ABCG1 transporter plays a key role in regulating cellular cholesterol and lipid homeostasis. Elucidation of the molecular mechanism by which ABCG1 controls sterol flux should provide critical information that may link ABCG1 to the reverse cholesterol transport pathway or diseases such as atherosclerosis.
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Affiliation(s)
- Angel Baldán
- Department of Biological Chemistry, David Geffen School of Medicine at the University of California, Los Angeles, USA
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Zhang Y, Lee FY, Barrera G, Lee H, Vales C, Gonzalez FJ, Willson TM, Edwards PA. Activation of the nuclear receptor FXR improves hyperglycemia and hyperlipidemia in diabetic mice. Proc Natl Acad Sci U S A 2006; 103:1006-11. [PMID: 16410358 PMCID: PMC1347977 DOI: 10.1073/pnas.0506982103] [Citation(s) in RCA: 711] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Indexed: 02/06/2023] Open
Abstract
Farnesoid X receptor (FXR) plays an important role in maintaining bile acid and cholesterol homeostasis. Here we demonstrate that FXR also regulates glucose metabolism. Activation of FXR by the synthetic agonist GW4064 or hepatic overexpression of constitutively active FXR by adenovirus-mediated gene transfer significantly lowered blood glucose levels in both diabetic db/db and wild-type mice. Consistent with these data, FXR null mice exhibited glucose intolerance and insulin insensitivity. We further demonstrate that activation of FXR in db/db mice repressed hepatic gluconeogenic genes and increased hepatic glycogen synthesis and glycogen content by a mechanism that involves enhanced insulin sensitivity. In view of its central roles in coordinating regulation of both glucose and lipid metabolism, we propose that FXR agonists are promising therapeutic agents for treatment of diabetes mellitus.
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Affiliation(s)
- Yanqiao Zhang
- Department of Biological Chemistry, University of California, Los Angeles, CA 90095, USA
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45
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Lee H, Zhang Y, Lee FY, Nelson SF, Gonzalez FJ, Edwards PA. FXR regulates organic solute transporters alpha and beta in the adrenal gland, kidney, and intestine. J Lipid Res 2006; 47:201-14. [PMID: 16251721 DOI: 10.1194/jlr.m500417-jlr200] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Expression of the farnesoid X receptor (FXR; NR1H4) is limited to the liver, intestine, kidney, and adrenal gland. However, the role of FXR in the latter two organs is unknown. In the current study, we performed microarray analysis using RNA from H295R cells infected with constitutively active FXR. Several putative FXR target genes were identified, including the organic solute transporters alpha and beta (OSTalpha and OSTbeta). Electromobility shift assays and promoter-reporter studies identified functional farnesoid X receptor response elements (FXREs) in the promoters of both human genes. These FXREs are conserved in both mouse genes. Treatment of wild-type mice with 3-(2,6-dichlorophenyl)-4-(3'-carboxy-2-chloro-stilben-4-yl)-oxymethyl-5-isopropyl-isoxazole (GW4064), a synthetic FXR agonist, induced OSTalpha and OSTbeta mRNAs in the intestine and kidney. Both mRNAs were also induced when wild-type, but not FXR-deficient (FXR-/-), adrenals were cultured in the presence of GW4064. OSTalpha and OSTbeta mRNA levels were also induced in the adrenals and kidneys of wild-type, but not FXR-/-, mice after the increase of plasma bile acids in response to the hepatotoxin alpha-naphthylisothiocyanate. Finally, overexpression of human OSTalpha and OSTbeta facilitated the uptake of conjugated chenodeoxycholate and the activation of FXR target genes. These results demonstrate that OSTalpha and OSTbeta are novel FXR target genes that are expressed in the adrenal gland, kidney, and intestine.
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Affiliation(s)
- Hans Lee
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
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46
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Shih DM, Kast-Woelbern HR, Wong J, Xia YR, Edwards PA, Lusis AJ. A role for FXR and human FGF-19 in the repression of paraoxonase-1 gene expression by bile acids. J Lipid Res 2005; 47:384-92. [PMID: 16269825 DOI: 10.1194/jlr.m500378-jlr200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Paraoxonase-1 (PON1), an enzyme that metabolizes organophosphate insecticides, is secreted by the liver and transported in the blood complexed to HDL. In humans and mice, low plasma levels of PON1 have also been linked to the development of atherosclerosis. We previously reported that hepatic Pon1 expression was decreased when C57BL/6J mice were fed a high-fat, high-cholesterol diet supplemented with cholic acid (CA). In the current study, we used wild-type and farnesoid X receptor (FXR) null mice to demonstrate that this repression is dependent upon CA and FXR. PON1 mRNA levels were also repressed when HepG2 cells, derived from a human hepatoma, were incubated with natural or highly specific synthetic FXR agonists. In contrast, fibroblast growth factor-19 (FGF-19) mRNA levels were greatly induced by these same FXR agonists. Furthermore, treatment of HepG2 cells with recombinant human FGF-19 significantly decreased PON1 mRNA levels. Finally, deletion studies revealed that the proximal -230 to -96 bp region of the PON1 promoter contains regulatory element(s) necessary for promoter activity and bile acid repression. These data demonstrate that human PON1 expression is repressed by bile acids through the actions of FXR and FGF-19.
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Affiliation(s)
- Diana M Shih
- Division of Cardiology, Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA.
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47
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Lee FY, Kast-Woelbern HR, Chang J, Luo G, Jones SA, Fishbein MC, Edwards PA. Alpha-crystallin is a target gene of the farnesoid X-activated receptor in human livers. J Biol Chem 2005; 280:31792-800. [PMID: 16012168 DOI: 10.1074/jbc.m503182200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Alpha-crystallins comprise 35% of soluble proteins in the ocular lens and possess chaperone-like functions. Furthermore, the alphaA subunit (alphaA-crystallin) of alpha crystallin is thought to be "lens-specific" as only very low levels of expression were detected in a few non-lenticular tissues. Here we report that human alphaA-crystallin is expressed in human livers and is regulated by farnesoid X-activated receptor (FXR) in response to FXR agonists. AlphaA-crystallin was identified in a microarray screen as one of the most highly induced genes after treatment of HepG2 cells with the synthetic FXR ligand GW4064. Northern blot and quantitative real-time PCR analyses confirmed that alphaA-crystallin expression was induced in HepG2-derived cell lines and human primary hepatocytes and hepatic stellate cells in response to either natural or synthetic FXR ligands. Transient transfection studies and electrophoretic mobility shift assays revealed a functional FXR response element located in intron 1 of the human alphaA-crystallin gene. Importantly, immunohistochemical staining of human liver sections showed increased alphaA-crystallin expression in cholangiocytes and hepatocytes. As a member of the small heat shock protein family possessing chaperone-like activity, alphaA-crystallin may be involved in protection of hepatocytes from the toxic effects of high concentrations of bile acids, as would occur in disease states such as cholestasis.
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Affiliation(s)
- Florence Y Lee
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA
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48
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Arai S, Shelton JM, Chen M, Bradley MN, Castrillo A, Bookout AL, Mak PA, Edwards PA, Mangelsdorf DJ, Tontonoz P, Miyazaki T. A role for the apoptosis inhibitory factor AIM/Spalpha/Api6 in atherosclerosis development. Cell Metab 2005; 1:201-13. [PMID: 16054063 DOI: 10.1016/j.cmet.2005.02.002] [Citation(s) in RCA: 224] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Revised: 02/15/2005] [Accepted: 02/25/2005] [Indexed: 11/19/2022]
Abstract
Macrophages play a central role in the development of atherosclerosis through the accumulation of oxidized LDL (oxLDL). AIM (Spalpha/Api6) has previously been shown to promote macrophage survival; however, its function in atherogenesis is unknown. Here we identify AIM as a critical factor that protects macrophages from the apoptotic effects of oxidized lipids. AIM protein is induced in response to oxLDL loading and is highly expressed in foam cells within atherosclerotic lesions. Interestingly, both expression of AIM in lesions and its induction by oxidized lipids require the action of LXR/RXR heterodimers. AIM-/- macrophages are highly susceptible to oxLDL-induced apoptosis in vitro and undergo accelerated apoptosis in atherosclerotic lesions in vivo. Moreover, early atherosclerotic lesions in AIM-/-LDLR-/- double knockout mice are dramatically reduced when compared to AIM+/+LDLR-/- controls. We conclude that AIM production facilitates macrophage survival within atherosclerotic lesions and that loss of AIM decreases early lesion development by increasing macrophage apoptosis.
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Affiliation(s)
- Satoko Arai
- Center for Immunology, The University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard NA7200, Dallas, Texas 75390, USA
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Anisfeld AM, Kast-Woelbern HR, Lee H, Zhang Y, Lee FY, Edwards PA. Activation of the nuclear receptor FXR induces fibrinogen expression: a new role for bile acid signaling. J Lipid Res 2005; 46:458-68. [PMID: 15604525 DOI: 10.1194/jlr.m400292-jlr200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Three genes, fibrinogen-alpha (FBGalpha), -beta, and -gamma, encode proteins that make up the mature FBG protein complex. This complex is secreted from the liver and plays a key role in coagulation in response to vascular disruption. We identified all three FBG genes in a screen designed to isolate genes that are regulated by the farnesoid X receptor (FXR; NR1H4). Treatment of human hepatoma cells with either naturally occurring or synthetic [3-(2,6-dichlorophenyl)-4-(3'-carboxy-2-chloro-stilben-4-yl)-oxymethyl-5-isopropyl-isoxazole] FXR ligands resulted in the induction of transcripts for all three genes. The induction of FBGbeta mRNA in response to activated FXR appears to be a primary transcriptional response, as it is blocked by actinomycin D but not by cycloheximide. Four FXR isoforms were recently identified that differ either at their N termini and/or by the presence of four amino acids in the hinge region. Interestingly, the activities of the human FBGbeta promoter-reporter constructs were highly induced by FXR isoforms that lack the four amino acid insert. The observation that all three FBG subunits are induced by specific FXR isoforms, in response to FXR ligands, suggests that bile acids and FXR modulate fibrinolytic activity.
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Affiliation(s)
- Andrew M Anisfeld
- Department of Biological Chemistry and Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
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50
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Kennedy MA, Barrera GC, Nakamura K, Baldán A, Tarr P, Fishbein MC, Frank J, Francone OL, Edwards PA. ABCG1 has a critical role in mediating cholesterol efflux to HDL and preventing cellular lipid accumulation. Cell Metab 2005; 1:121-31. [PMID: 16054053 DOI: 10.1016/j.cmet.2005.01.002] [Citation(s) in RCA: 644] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Revised: 11/19/2004] [Accepted: 01/11/2005] [Indexed: 01/19/2023]
Abstract
Here we demonstrate that the ABC transporter ABCG1 plays a critical role in lipid homeostasis by controlling both tissue lipid levels and the efflux of cellular cholesterol to HDL. Targeted disruption of Abcg1 in mice has no effect on plasma lipids but results in massive accumulation of both neutral lipids and phospholipids in hepatocytes and in macrophages within multiple tissues following administration of a high-fat and -cholesterol diet. In contrast, overexpression of human ABCG1 protects murine tissues from dietary fat-induced lipid accumulation. Finally, we show that cholesterol efflux to HDL specifically requires ABCG1, whereas efflux to apoA1 requires ABCA1. These studies identify Abcg1 as a key gene involved in both cholesterol efflux to HDL and in tissue lipid homeostasis.
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Affiliation(s)
- Matthew A Kennedy
- Department of Biological Chemistry, CHS 33-257, David Geffen School of Medicine, University of California Los Angeles, 10833 Le Conte Avenue, Los Angeles, California 90095, USA
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