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Chen WD, Wang YD, Meng Z, Zhang L, Huang W. Nuclear bile acid receptor FXR in the hepatic regeneration. Biochim Biophys Acta Mol Basis Dis 2010; 1812:888-92. [PMID: 21167938 DOI: 10.1016/j.bbadis.2010.12.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 12/06/2010] [Accepted: 12/08/2010] [Indexed: 01/05/2023]
Abstract
The liver can fully regenerate itself by a compensatory regrowth in response to partial hepatectomy or injury. This process consists of a variety of well-orchestrated phases and is mediated by many signals. Farnesoid X receptor (FXR) is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Bile acids are FXR physiological ligands. As a metabolic regulator, FXR plays key roles in regulating metabolism of bile acids, lipids and glucose. Recently, bile acid/FXR signaling pathway is shown to be required for normal liver regeneration. Furthermore, FXR promotes liver repair after injury and activation of FXR is able to alleviate age-related defective liver regeneration. These novel findings suggest that FXR-mediated bile acid signaling is an integrated component of normal liver regeneration machinery, and also highlight the potential use of FXR ligands to promote liver regeneration after segmental liver transplantation or resection of liver tumors. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.
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Affiliation(s)
- Wei-Dong Chen
- Division of Gene Regulation & Drug Discovery, Beckman Research Institute, City of Hope National Medical Center, 1500 E. Duarte Road, Duarte, CA 91010, USA
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52
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Chao F, Gong W, Zheng Y, Li Y, Huang G, Gao M, Li J, Kuruba R, Gao X, Li S, He F. Upregulation of scavenger receptor class B type I expression by activation of FXR in hepatocyte. Atherosclerosis 2010; 213:443-8. [DOI: 10.1016/j.atherosclerosis.2010.09.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 09/15/2010] [Accepted: 09/15/2010] [Indexed: 12/20/2022]
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53
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Yeang C, Qin S, Chen K, Wang DQH, Jiang XC. Diet-induced lipid accumulation in phospholipid transfer protein-deficient mice: its atherogenicity and potential mechanism. J Lipid Res 2010; 51:2993-3002. [PMID: 20543142 DOI: 10.1194/jlr.m007088] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A high saturated fat diet induces free cholesterol and phospholipid accumulation in the plasma of phospholipid transfer protein (Pltp)-deficient mice. In this study, we examined the atherogenic consequence of this phenomenon and investigated the possible mechanism(s). Pltp KO/Apoe KO mice that were fed a coconut oil-enriched high-fat diet (COD) for 7 weeks had higher plasma free cholesterol (149%), phospholipids (15%), and sphingomyelin (54%) than Apoe KO controls. In contrast to chow-fed animals, COD-fed Pltp KO/Apoe KO mice had the same atherosclerotic lesion size as that of Apoe KO mice. Similar to Pltp KO mice, plasma from COD-fed Pltp KO/Apoe KO mice contained VLDL/LDL-sized lamellar particles. Bile measurement indicated that COD-fed Pltp KO mice have 33% less hepatic cholesterol output than controls. In conclusion, COD-fed, Pltp-deficient mice are no longer protected from atherosclerosis and have impaired biliary lipid secretion, which is associated with free cholesterol and phospholipid accumulation.
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Affiliation(s)
- Calvin Yeang
- Department of Cell Biology, State University of New York (SUNY) Downstate Medical Center, Brooklyn, NY, USA
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54
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Han KC, Kim JH, Kim KH, Kim EE, Seo JH, Yang EG. Identification of farnesoid X receptor modulators by a fluorescence polarization-based interaction assay. Anal Biochem 2010; 398:185-90. [DOI: 10.1016/j.ab.2009.11.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 11/05/2009] [Accepted: 11/07/2009] [Indexed: 10/20/2022]
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55
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Jarvik GP, Rajagopalan R, Rosenthal EA, Wolfbauer G, McKinstry L, Vaze A, Brunzell J, Motulsky AG, Nickerson DA, Heagerty PJ, Wijsman EM, Albers JJ. Genetic and nongenetic sources of variation in phospholipid transfer protein activity. J Lipid Res 2009; 51:983-90. [PMID: 19965587 DOI: 10.1194/jlr.m000125] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phospholipid transfer protein (PLTP) belongs to the lipid transfer/lipopolysaccharide-binding protein gene family. Expression of PLTP has been implicated in the development of atherosclerosis. We evaluated the effects of PLTP region tagging single nucleotide polymorphisms (SNPs) on the prediction of both carotid artery disease (CAAD) and PLTP activity. CAAD effects were evaluated in 442 Caucasian male subjects with severe CAAD and 497 vascular disease-free controls. SNP prediction of PLTP transfer activity was evaluated in both a subsample of 87 subjects enriched for an allele of interest and in a confirmation sample of 210 Caucasian males and females. Hemoglobin A1c or insulin level predicted 11-14% of age- and sex-adjusted PLTP activity. PLTP SNPs that predicted approximately 11-30% of adjusted PLTP activity variance were identified in the two cohorts. For rs6065904, the allele that was associated with CAAD was also associated with elevated PLTP activity in both cohorts. SNPs associated with PLTP activity also predicted variation in LDL-cholesterol and LDL-B level only in the replication cohort. These results demonstrate that PLTP activity is strongly influenced by PLTP region polymorphisms and metabolic factors.
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Affiliation(s)
- Gail P Jarvik
- Department of Medicine (Division of Medical Genetics), University of Washington, Seattle, WA, USA.
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Staels B, Fonseca VA. Bile acids and metabolic regulation: mechanisms and clinical responses to bile acid sequestration. Diabetes Care 2009; 32 Suppl 2:S237-45. [PMID: 19875558 PMCID: PMC2811459 DOI: 10.2337/dc09-s355] [Citation(s) in RCA: 247] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Bart Staels
- Institut Pasteur de Lille, INSERM U545, Université Lille Nord de France, Lille, France.
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57
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Del Bas JM, Ricketts ML, Vaqué M, Sala E, Quesada H, Ardevol A, Salvadó MJ, Blay M, Arola L, Moore DD, Pujadas G, Fernandez-Larrea J, Bladé C. Dietary procyanidins enhance transcriptional activity of bile acid-activated FXR in vitro and reduce triglyceridemia in vivo in a FXR-dependent manner. Mol Nutr Food Res 2009; 53:805-14. [PMID: 19496086 DOI: 10.1002/mnfr.200800364] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Consumption of dietary flavonoids has been associated with reduced mortality and risk of cardiovascular disease, partially by reducing triglyceridemia. We have previously reported that a grape seed procyanidin extract (GSPE) reduces postprandial triglyceridemia in normolipidemic animals signaling through the orphan nuclear receptor small heterodimer partner (SHP) a target of the bile acid receptor farnesoid X receptor (FXR). Our aim was to elucidate whether FXR mediates the hypotriglyceridemic effect of procyanidins. In FXR-driven luciferase expression assays GSPE dose-dependently enhanced FXR activity in the presence of chenodeoxycholic acid. GSPE gavage reduced triglyceridemia in wild type mice but not in FXR-null mice, revealing FXR as an essential mediator of the hypotriglyceridemic actions of procyanidins in vivo. In the liver, GSPE downregulated, in an FXR-dependent manner, the expression of the transcription factor steroid response element binding protein 1 (SREBP1) and several SREBP1 target genes involved in lipogenesis, and upregulated ApoA5 expression. Altogether, our results indicate that procyanidins lower triglyceridemia following the same pathway as bile acids: activation of FXR, transient upregulation of SHP expression and subsequent downregulation of SREBP1 expression. This study adds dietary procyanidins to the arsenal of FXR ligands with potential therapeutic use to combat hypertriglyceridemia, type 2 diabetes and metabolic syndrome.
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Affiliation(s)
- Josep Maria Del Bas
- Departament de Bioquímica i Biotecnología, Universitat Rovira i Virgili, Campus Sescelades, Tarragona, Spain
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58
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Lefebvre P, Cariou B, Lien F, Kuipers F, Staels B. Role of bile acids and bile acid receptors in metabolic regulation. Physiol Rev 2009; 89:147-91. [PMID: 19126757 DOI: 10.1152/physrev.00010.2008] [Citation(s) in RCA: 1137] [Impact Index Per Article: 75.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The incidence of the metabolic syndrome has taken epidemic proportions in the past decades, contributing to an increased risk of cardiovascular disease and diabetes. The metabolic syndrome can be defined as a cluster of cardiovascular disease risk factors including visceral obesity, insulin resistance, dyslipidemia, increased blood pressure, and hypercoagulability. The farnesoid X receptor (FXR) belongs to the superfamily of ligand-activated nuclear receptor transcription factors. FXR is activated by bile acids, and FXR-deficient (FXR(-/-)) mice display elevated serum levels of triglycerides and high-density lipoprotein cholesterol, demonstrating a critical role of FXR in lipid metabolism. In an opposite manner, activation of FXR by bile acids (BAs) or nonsteroidal synthetic FXR agonists lowers plasma triglycerides by a mechanism that may involve the repression of hepatic SREBP-1c expression and/or the modulation of glucose-induced lipogenic genes. A cross-talk between BA and glucose metabolism was recently identified, implicating both FXR-dependent and FXR-independent pathways. The first indication for a potential role of FXR in diabetes came from the observation that hepatic FXR expression is reduced in animal models of diabetes. While FXR(-/-) mice display both impaired glucose tolerance and decreased insulin sensitivity, activation of FXR improves hyperglycemia and dyslipidemia in vivo in diabetic mice. Finally, a recent report also indicates that BA may regulate energy expenditure in a FXR-independent manner in mice, via activation of the G protein-coupled receptor TGR5. Taken together, these findings suggest that modulation of FXR activity and BA metabolism may open new attractive pharmacological approaches for the treatment of the metabolic syndrome and type 2 diabetes.
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Affiliation(s)
- Philippe Lefebvre
- Institut National de la Sante et de la Recherche Medicale, Lille, France
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59
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Kong B, Luyendyk JP, Tawfik O, Guo GL. Farnesoid X receptor deficiency induces nonalcoholic steatohepatitis in low-density lipoprotein receptor-knockout mice fed a high-fat diet. J Pharmacol Exp Ther 2009; 328:116-22. [PMID: 18948497 PMCID: PMC2685903 DOI: 10.1124/jpet.108.144600] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 10/22/2008] [Indexed: 12/23/2022] Open
Abstract
Nonalcoholic steatohepatitis (NASH) comprises dysregulation of lipid metabolism and inflammation. Identification of the various genetic and environmental susceptibility factors for NASH may provide novel treatments to limit inflammation and fibrosis in patients. This study utilized a mouse model of hypercholesterolemia, low-density lipoprotein receptor knockout (LDLr(-/-)) mice fed a high-fat diet for 5 months, to test the hypothesis that farnesoid X receptor (FXR) deficiency contributed to NASH development. Either the high-fat diet or FXR deficiency increased serum alanine aminotransferase activity, whereas only FXR deficiency increased bile acid and alkaline phosphatase levels. FXR deficiency and high-fat feeding increased serum cholesterol and triglycerides. Although high fat led to macrosteatosis and hepatocyte ballooning in livers of mice regardless of genotype, no inflammatory infiltrate was observed in the livers of LDLr(-/-) mice. In contrast, in the livers of LDLr(-/-)/FXR(-/-) mice, foci of inflammatory cells were observed occasionally when fed the control diet and were greatly increased when fed the high-fat diet. Consistent with enhanced inflammatory cells, hepatic levels of tumor necrosis factor alpha and intercellular adhesion molecule-1 mRNA were increased by the high-fat diet in LDLr(-/-)/FXR(-/-) mice. In agreement with elevated levels of procollagen 1 alpha 1 and TGF-beta mRNA, type 1 collagen protein levels were increased in livers of LDLr(-/-)/FXR(-/-) mice fed a high-fat diet. In conclusion, FXR deficiency induces pathologic manifestations required for NASH diagnosis in a mouse model of hypercholesterolemia, including macrosteatosis, hepatocyte ballooning, and inflammation, which suggest a combination of FXR deficiency and high-fat diet is a risk factor for NASH development, and activation of FXR may be a therapeutic intervention in the treatment of NASH.
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Affiliation(s)
- Bo Kong
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center. 3901 Rainbow Blvd., Kansas City, KS 66160, USA
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60
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Li H, Jiang Y, He FC. A potential role of GW4064 to inhibit gut bacterial overgrowth by activating FXR in suppression of ethanol-induced liver injury. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.bihy.2008.02.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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61
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Hoeke MO, Plass JRM, Heegsma J, Geuken M, van Rijsbergen D, Baller JFW, Kuipers F, Moshage H, Jansen PLM, Faber KN. Low retinol levels differentially modulate bile salt-induced expression of human and mouse hepatic bile salt transporters. Hepatology 2009; 49:151-9. [PMID: 19111018 DOI: 10.1002/hep.22661] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
UNLABELLED The farnesoid X receptor/retinoid X receptor-alpha (FXR/RXRalpha) complex regulates bile salt homeostasis, in part by modulating transcription of the bile salt export pump (BSEP/ABCB11) and small heterodimer partner (SHP/NR0B2). FXR is activated by bile salts, RXRalpha by the vitamin A derivative 9-cis retinoic acid (9cRA). Cholestasis is associated with vitamin A malabsorption. Therefore, we evaluated the role of vitamin A/9cRA in the expression of human and mouse bile salt export pump (hBSEP/mBsep), small heterodimer partner (hSHP/mShp), and mouse sodium-dependent taurocholate co-transporting polypeptide (mNtcp). HBSEP and hSHP transcription were analyzed in FXR/RXRalpha-transfected HepG2 cells exposed to chenodeoxycholic acid (CDCA) and/or 9cRA. BSEP promoter activity was determined by luciferase reporter assays, DNA-binding of FXR and RXRalpha by pull-down assays. Serum bile salt levels and hepatic expression of Bsep, Shp, and Ntcp were determined in vitamin A-deficient (VAD)/cholic acid (CA)-fed C57BL/6J mice. Results indicated that 9cRA strongly repressed the CDCA-induced BSEP transcription in HepG2 cells, whereas it super-induced SHP transcription; 9cRA reduced DNA-binding of FXR and RXRalpha. The 9cRA repressed the CDCA-induced BSEP promoter activity irrespective of the exact sequence of the FXR-binding site. In vivo, highest Bsep messenger RNA (mRNA), and protein expression was observed in CA-fed VAD mice. Shp transcription was highest in CA-fed vitamin A-sufficient mice. Ntcp protein expression was strongly reduced in CA-fed VAD mice, whereas mRNA levels were normal. CA-fed control and VAD mice had similarly increased serum bile salt levels. CONCLUSION We showed that 9cRA has opposite effects on bile salt-activated transcription of FXR/RXRalpha target genes. Vitamin A deficiency in CA-fed mice leads to high BSEP expression. Clearance of serum bile salts may, however, be limited because of post-transcriptional reduction of Ntcp. The molecular effects of vitamin A supplementation during cholestasis need further analysis to predict a therapeutic effect.
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Affiliation(s)
- Martijn O Hoeke
- Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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62
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Prawitt J, Caron S, Staels B. How to modulate FXR activity to treat the Metabolic Syndrome. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.ddmec.2010.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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63
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Abstract
Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily of ligand-activated transcription factors. As a metabolic regulator, FXR plays key roles in bile acid, cholesterol, lipid, and glucose metabolism. Therefore, FXR is a potential drug target for a number of metabolic disorders, especially those related to the metabolic syndrome. More recently, our group and others have extended the functions of FXR to more than metabolic regulation, which include anti-bacterial growth in intestine, liver regeneration, and hepatocarcinogenesis. These new findings suggest that FXR has much broader roles than previously thought, and also highlight FXR as a drug target for multiple diseases. This review summarizes the basic information of FXR but focuses on its new functions.
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64
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Samyn H, Moerland M, van Gent T, van Haperen R, Metso J, Grosveld F, Jauhiainen M, van Tol A, de Crom R. Plasma phospholipid transfer activity is essential for increased atherogenesis in PLTP transgenic mice: a mutation-inactivation study. J Lipid Res 2008; 49:2504-12. [DOI: 10.1194/jlr.m800080-jlr200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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65
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Abstract
Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.
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Affiliation(s)
- Norbert Stefan
- Department of Internal Medicine, Otfried-Müller-Strasse 10, D-72076 Tübingen, Germany
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66
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Engler MB, Pullinger CR, Malloy MJ, Natanzon Y, Kulkarni MV, Song J, Eng C, Huuskonen J, Rivera C, Poon A, Bensley M, Sehnert A, Zellner C, Kane J, Aouizerat BE. Genetic variation in phospholipid transfer protein modulates lipoprotein profiles in hyperalphalipoproteinemia. Metabolism 2008; 57:1719-24. [PMID: 19013296 PMCID: PMC2615231 DOI: 10.1016/j.metabol.2008.07.031] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Accepted: 07/17/2008] [Indexed: 02/07/2023]
Abstract
We previously demonstrated the role of a phospholipid transfer protein (PLTP) gene variation (rs2294213) in determining levels of high-density lipoprotein cholesterol (HDL-C) in hypoalphalipoproteinemia (HypoA). We have now explored the role of PLTP in hyperalphalipoproteinemia (HyperA). The human PLTP gene was screened for sequence anomalies by DNA melting in 107 subjects with HyperA. The association with plasma lipoprotein levels was evaluated. We detected 7 sequence variations: 1 previously reported variation (rs2294213) and 5 novel mutations including 1 missense mutation (L106F). The PLTP activity was unchanged in the p.L106F mutation. The frequency of the rs2294213 minor allele was markedly increased in the HyperA group (7.0%) in comparison with a control group (4.3%) and the hypoalphalipoproteinemia group (2.2%). Moreover, rs2294213 was strongly associated with HDL-C levels. Linear regression models predict that possession of the rs2294213 minor allele increases HDL-C independent of triglycerides. These findings extend the association of rs2294213 with HDL-C levels into the extremes of the HDL distribution.
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Affiliation(s)
- Mary B. Engler
- Department of Physiological Nursing, University of California San Francisco, San Francisco, CA 94143
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA 94143
| | - Clive R. Pullinger
- Department of Physiological Nursing, University of California San Francisco, San Francisco, CA 94143
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Mary J. Malloy
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Yanina Natanzon
- Department of Physiological Nursing, University of California San Francisco, San Francisco, CA 94143
| | - Medha V. Kulkarni
- Department of Physiological Nursing, University of California San Francisco, San Francisco, CA 94143
| | - James Song
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Celeste Eng
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Jaarko Huuskonen
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Christopher Rivera
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Annie Poon
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Matt Bensley
- Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143
| | - Amy Sehnert
- Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143
| | - Christian Zellner
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - John Kane
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA 94143
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143
| | - Bradley E. Aouizerat
- Department of Physiological Nursing, University of California San Francisco, San Francisco, CA 94143
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA 94143
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67
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Mencarelli A, Renga B, Distrutti E, Fiorucci S. Antiatherosclerotic effect of farnesoid X receptor. Am J Physiol Heart Circ Physiol 2008; 296:H272-81. [PMID: 19028791 DOI: 10.1152/ajpheart.01075.2008] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily that functions as an endogenous sensor for bile acids and regulates cholesterol and fatty acid metabolism. The effect of FXR activation on aortic plaque formation was assessed by feeding apolipoprotein E-deficient (ApoE-/-) mice with the synthetic FXR ligand INT-747, a cheno-deoxycholic acid derivative, at doses of 3 and 10 mg x kg(-1) x day(-1), or with rosiglitazone, a peroxisome proliferator-activated receptor-gamma ligand, at the dose of 10 mg x kg(-1) x day(-1) for 12 wk. Administration of INT-747 reduced formation of aortic plaque area by 95% (P < 0.01), and a similar antiplaque activity was exerted by administration of rosiglitazone. INT-747 administration to ApoE-/- mice reduced aortic expression of IL-1beta, IL-6, and CD11b mRNA, while it upregulated the expression of FXR and its target gene, the small heterodimer partner (SHP). FXR activation reduced the liver expression of sterol regulatory element binding protein 1c, resulting in reduced triglyceride and cholesterol content in the liver and amelioration of hyperlipidemia. FXR expression, mRNA and protein, was detected in human macrophages and macrophage cell lines. FXR activation by natural and synthetic ligands in these cell types attenuated IL-1beta, IL-6, and TNF-alpha gene induction in response to Toll-like receptor 4 activation by LPS. Using spleen monocytes from wild-type and FXR-/- mice, we demonstrated that FXR gene ablation exacerbates IL-6 and TNF-alpha generation by LPS-stimulated macrophages. FXR was also able to reduce cholesterol uptake on macrophages by regulation of CD36 and ABCA1 expression. We found that FXR and SHP are expressed in the aorta and macrophages and that FXR ligands might have utility in prevention and treatment of atherosclerotic lesions.
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Affiliation(s)
- Andrea Mencarelli
- Dipartimento di Medicina Clinica e Sperimentale, University of Perugia, Perugia, Italy
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68
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Wang YD, Chen WD, Wang M, Yu D, Forman BM, Huang W. Farnesoid X receptor antagonizes nuclear factor kappaB in hepatic inflammatory response. Hepatology 2008; 48:1632-43. [PMID: 18972444 PMCID: PMC3056574 DOI: 10.1002/hep.22519] [Citation(s) in RCA: 461] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The farnesoid X receptor (FXR) is a nuclear receptor that plays key roles in hepatoprotection by maintaining the homeostasis of liver metabolism. FXR null mice display strong hepatic inflammation and develop spontaneous liver tumors. In this report, we demonstrate that FXR is a negative modulator of nuclear factor kappaB (NF-kappaB)-mediated hepatic inflammation. Activation of FXR by its agonist ligands inhibited the expression of inflammatory mediators in response to NF-kappaB activation in both HepG2 cells and primary hepatocytes cultured in vitro. In vivo, compared with wild-type controls, FXR(-/-) mice displayed elevated messenger RNA (mRNA) levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interferon-inducible protein 10, and interferon-gamma in response to lipopolysaccharide (LPS). Examination of FXR(-/-) livers showed massive necroses and inflammation after treatment with LPS at a dose that does not induce significant liver damage or inflammation in wild-type mice. Moreover, transfection of a constitutively active FXR expression construct repressed the iNOS, COX-2, interferon-inducible protein 10 and interferon-gamma mRNA levels induced by LPS administration. FXR activation had no negative effects on NF-kappaB-activated antiapoptotic genes, suggesting that FXR selectively inhibits the NF-kappaB-mediated hepatic inflammatory response but maintains or even enhances the cell survival response. On the other hand, NF-kappaB activation suppressed FXR-mediated gene expression both in vitro and in vivo, indicating a negative crosstalk between the FXR and NF-kappaB signaling pathways. Our findings reveal that FXR is a negative mediator of hepatic inflammation, which may contribute to the critical roles of FXR in hepatoprotection and suppression of hepatocarcinogenesis.
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Affiliation(s)
- Yan-Dong Wang
- Department of Gene Regulation and Drug Discovery, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91010, USA
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69
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Gineste R, Sirvent A, Paumelle R, Helleboid S, Aquilina A, Darteil R, Hum DW, Fruchart JC, Staels B. Phosphorylation of farnesoid X receptor by protein kinase C promotes its transcriptional activity. Mol Endocrinol 2008; 22:2433-47. [PMID: 18755856 DOI: 10.1210/me.2008-0092] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The farnesoid X receptor (FXR, NR1H4) belongs to the nuclear receptor superfamily and is activated by bile acids such as chenodeoxycholic acid, or synthetic ligands such as GW4064. FXR is implicated in the regulation of bile acid, lipid, and carbohydrate metabolism. Posttranslational modifications regulating its activity have not been investigated yet. Here, we demonstrate that calcium-dependent protein kinase C (PKC) inhibition impairs ligand-mediated regulation of FXR target genes. Moreover, in a transactivation assay, we show that FXR transcriptional activity is modulated by PKC. Furthermore, phorbol 12-myristate 13-acetate , a PKC activator, induces the phosphorylation of endogenous FXR in HepG2 cells and PKCalpha phosphorylates in vitro FXR in its DNA-binding domain on S135 and S154. Mutation of S135 and S154 to alanine residues reduces in cell FXR phosphorylation. In contrast to wild-type FXR, mutant FXRS135AS154A displays an impaired PKCalpha-induced transactivation and a decreased ligand-dependent FXR transactivation. Finally, phosphorylation of FXR by PKC promotes the recruitment of peroxisomal proliferator-activated receptor gamma coactivator 1alpha. In conclusion, these findings show that the phosphorylation of FXR induced by PKCalpha directly modulates the ability of agonists to activate FXR.
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70
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Takahashi M, Kanayama T, Yashiro T, Kondo H, Murase T, Hase T, Tokimitsu I, Nishikawa JI, Sato R. Effects of coumestrol on lipid and glucose metabolism as a farnesoid X receptor ligand. Biochem Biophys Res Commun 2008; 372:395-9. [PMID: 18457666 DOI: 10.1016/j.bbrc.2008.04.136] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Accepted: 04/25/2008] [Indexed: 11/15/2022]
Abstract
In the course of an effort to identify novel agonists of the farnesoid X receptor (FXR), coumestrol was determined to be one such ligand. Reporter and in vitro coactivator interaction assays revealed that coumestrol bound and activated FXR. Treatment of Hep G2 cells with coumestrol stimulated the expression of FXR target genes, thereby regulating the expression of target genes of the liver X receptor and hepatocyte nuclear factor-4alpha. Through these actions, coumestrol is expected to exert beneficial effects on lipid and glucose metabolism.
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Affiliation(s)
- Miki Takahashi
- Biological Science Laboratories, Kao Corporation, 2606 Akabane, Ichikai-machi, Haga-gun, Tochigi 321-3497, Japan
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71
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OHNO M. Functional Analysis of Nuclear Receptor FXR Controlling Metabolism of Cholesterol. YAKUGAKU ZASSHI 2008; 128:343-55. [DOI: 10.1248/yakushi.128.343] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Masae OHNO
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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72
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Higashiyama H, Kinoshita M, Asano S. Immunolocalization of farnesoid X receptor (FXR) in mouse tissues using tissue microarray. Acta Histochem 2008; 110:86-93. [PMID: 17963822 DOI: 10.1016/j.acthis.2007.08.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 08/01/2007] [Accepted: 08/01/2007] [Indexed: 11/30/2022]
Abstract
Farnesoid X receptor (FXR) is a member of the nuclear receptor family and is known to play important roles in bile acid homeostasis, and lipid and glucose metabolism. In this study, to elucidate the systemic physiological functions of FXR, comprehensive immunohistochemical analysis of cell/subcellular localization of FXR and its heterodimer partner, retinoid X receptor (RXR)-alpha, in adult mice tissues was performed using tissue microarray (TMA)-based immunohistochemistry. FXR immunolabeling was observed in the enterohepatic system--including absorptive epithelium in the intestines, hepatocytes and gall bladder epithelium, several epithelial lineage cells including the basal cells of stratified epithelium in the tongue, esophagus, forestomach--skin, corneal epithelium and ciliary body epithelium in the eye and adrenocortical cells--including glandular cells in the zona reticularis/fasciculata. In these FXP-positive cells, FXR was preferentially localized to the nucleus. RXR-alpha was ubiquitously distributed in the nucleus of most cell types, including FXR-positive cell types in the examined tissues. These data suggest that FXR might have various physiological roles, not only in bile acid homeostasis, and lipid and glucose metabolism, but also in the epithelial cell barrier, visual and urinary function through multiple organ systems.
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Affiliation(s)
- Hiroyuki Higashiyama
- Tsukuba Research Laboratories, Pharmacology Department, GlaxoSmithKline, 43 Wadai, Tsukuba, Ibaraki 300-4247, Japan
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73
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Nam SJ, Ko H, Ju MK, Hwang H, Chin J, Ham J, Lee B, Lee J, Won DH, Choi H, Ko J, Shin K, Oh T, Kim S, Rho JR, Kang H. Scalarane sesterterpenes from a marine sponge of the genus Spongia and their FXR antagonistic activity. JOURNAL OF NATURAL PRODUCTS 2007; 70:1691-1695. [PMID: 17988093 DOI: 10.1021/np070024k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Three new scalarane-based sesterterpenes, 1- 3, were isolated from a marine sponge of the genus Spongia, and their chemical structures were elucidated by analysis of HRMS and 2-D NMR spectra. The isolated compounds 1 and 3 showed inhibition against the farnesoid X-activated receptor (FXR) with IC50 values of 2.4 and 24 microM, respectively. In particular, compound 3 directly inhibited the interaction between FXR and a coactivator peptide (SRC-1) as determined by surface plasmon resonance (SPR) spectroscopy.
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Affiliation(s)
- Sang-Jip Nam
- Center for Marine Natural Products and Drug Discovery, School of Earth and Environmental Sciences, Seoul National University, NS-80, Seoul, 151-747, Korea
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74
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Murakami T, Walczak R, Caron S, Duhem C, Vidal V, Darteil R, Staels B. The farnesoid X receptor induces fetuin-B gene expression in human hepatocytes. Biochem J 2007; 407:461-9. [PMID: 17655523 PMCID: PMC2275064 DOI: 10.1042/bj20070658] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
FXR (farnesoid X receptor), a nuclear receptor activated by BAs (bile acids), is a key factor in the regulation of BA, lipid and carbohydrate metabolism. The recent development of synthetic FXR agonists and knockout mouse models has accelerated the discovery of FXR target genes. In the present study, we identify human fetuin-B as a novel FXR target gene. Treatment with FXR agonists increased fetuin-B expression in human primary hepatocytes and in the human hepatoma HepG2 cell line. In contrast, fetuin-B expression was not responsive to FXR agonist treatment in murine primary hepatocytes. Fetuin-B induction by FXR agonist was abolished upon FXR knockdown by siRNA (small interfering RNA). In addition to the previously described P1 promoter, we show that the human fetuin-B gene is also transcribed from an alternative promoter, termed P2. Transcription via the P2 promoter was induced by FXR agonist treatment, whereas P1 promoter activity was not sensitive to FXR agonist treatment. Two putative FXR-response elements [IR-1 (inverted repeat-1)] were identified in the region -1.6 kb upstream of the predicted P2 transcriptional start site. Both motifs bound FXR-RXR (retinoid X receptor) complexes in vitro and were activated by FXR in transient transfection reporter assays. Mutations in the IR-1 sites abolished FXR-RXR binding and activation. Taken together, these results identify human fetuin-B as a new FXR target gene in human hepatocytes.
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Affiliation(s)
- Takeshi Murakami
- *Tokyo New Research Laboratories I, Pharmaceutical Division, Kowa Company Ltd, 2-17-43 Noguchicho, Higashimurayama, Tokyo, Japan
| | | | - Sandrine Caron
- ‡Institut Pasteur de Lille, Lille F-59019, France
- §Inserm, U545, Lille F-59019, France
- ¶Faculté de Pharmacie et Faculté de Médecine, Université de Lille 2, Lille F-59006, France
| | - Christian Duhem
- ‡Institut Pasteur de Lille, Lille F-59019, France
- §Inserm, U545, Lille F-59019, France
- ¶Faculté de Pharmacie et Faculté de Médecine, Université de Lille 2, Lille F-59006, France
| | | | | | - Bart Staels
- ‡Institut Pasteur de Lille, Lille F-59019, France
- §Inserm, U545, Lille F-59019, France
- ¶Faculté de Pharmacie et Faculté de Médecine, Université de Lille 2, Lille F-59006, France
- To whom correspondence should be addressed (email )
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75
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Kuipers F, Stroeve JHM, Caron S, Staels B. Bile acids, farnesoid X receptor, atherosclerosis and metabolic control. Curr Opin Lipidol 2007; 18:289-97. [PMID: 17495603 DOI: 10.1097/mol.0b013e3281338d08] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
PURPOSE OF REVIEW Bile acids are amphiphilic molecules synthesized from cholesterol exclusively in the liver that are essential for effective absorption of dietary fat. In addition to this 'classical role', bile acids act as signalling molecules that control their own metabolism by activating the nuclear receptor, farnesoid X receptor. RECENT FINDINGS Recent work demonstrates that farnesoid X receptor exerts metabolic control beyond bile acid homeostasis, notably effects on HDL, triglyceride and glucose metabolism. Farnesoid X receptor influences insulin sensitivity of tissues that are not part of the enterohepatic circulation, for example, adipose tissue. Certain metabolic effects in the liver appear to be mediated via farnesoid X receptor-stimulated release of an intestinal growth factor. In addition, novel signalling pathways independent of farnesoid X receptor have been identified that may contribute to bile acid-mediated metabolic regulation. SUMMARY Farnesoid X receptor represents a potentially attractive target for treatment of various aspects of the metabolic syndrome and for prevention of atherosclerosis. Yet, in view of its pleiotropic effects and apparent species-specificity, it is evident that successful interference of the farnesoid X receptor signalling system will require the development of gene-specific and/or organ-specific farnesoid X receptor modulators and extensive testing in human models of disease.
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Affiliation(s)
- Folkert Kuipers
- Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, The Netherlands.
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76
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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] [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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77
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Lou G, Li Y, Chen B, Chen M, Chen J, Liao R, Zhang Y, Wang Y, Zhou D. Functional analysis on the 5'-flanking region of human FXR gene in HepG2 cells. Gene 2007; 396:358-68. [PMID: 17507182 DOI: 10.1016/j.gene.2007.04.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2006] [Revised: 03/13/2007] [Accepted: 04/09/2007] [Indexed: 01/10/2023]
Abstract
The farnesoid X receptor (FXR) is a bile acid (BA)-activated nuclear receptor that plays a major role in the regulation of BA and lipid metabolism. Although modulation of FXR expression has been reported, the mechanisms underlying the regulation of human FXR are yet unclear. Functional assays showed that the -150/+29 nucleotides region from the first nucleotide at the Exon I is the minimal promoter of the human FXR gene by the technique of serial deletion and point mutants of the 5'-flanking region. Chromatin immunoprecipitation analysis and electrophoretic mobility shift assay revealed that hepatic nuclear factor 1alpha (HNF1alpha) interacted with the region. Co-transfection of the promoter with HNF1alpha expression vectors enhanced promoter activity of FXR gene. Over-expression of HNF1alpha up-regulated FXR expression in HepG2 cells. These data indicate that (a) the identified HNF1alpha binding site serves as a positive regulatory sequence, (b) the binding site is functionally active both in vivo and in vitro, and (c) the transcription factor HNF1alpha that binds to this site plays an important role in the regulation of human FXR promoter activity.
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Affiliation(s)
- Guiyu Lou
- Department of Biochemistry and Molecular Biology, Third Military Medical University, Chongqing 400038, China
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78
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Cariou B, Staels B. FXR: a promising target for the metabolic syndrome? Trends Pharmacol Sci 2007; 28:236-43. [PMID: 17412431 DOI: 10.1016/j.tips.2007.03.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2006] [Revised: 02/12/2007] [Accepted: 03/21/2007] [Indexed: 12/23/2022]
Abstract
The metabolic syndrome is an insulin-resistant state that is characterized by a cluster of cardiovascular risk factors, including abdominal obesity, hyperglycemia, elevated blood pressure and combined dyslipidemia. In this review, we discuss the role of the bile-acid-activated farnesoid X receptor (FXR) in the modulation of the metabolic syndrome. Owing to its regulatory actions in lipid and glucose homeostasis, FXR is a potential pharmacological target. Moreover, the observation that FXR also influences endothelial function and atherosclerosis indicates a regulatory role in the cardiovascular complications that are associated with the metabolic syndrome. The pharmacological activation of FXR leads to a complex response that integrates beneficial actions and potentially undesirable side-effects. Thus, the identification of selective FXR modulators (selective bile acid receptor modulators) is required for the development of compounds that can be used to treat the metabolic syndrome.
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Affiliation(s)
- Bertrand Cariou
- Centre Hospitalier Universitaire Hôtel-Dieu, Nantes 44093, France.
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79
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Abstract
Vitamin A signaling occurs through nuclear receptors recognizing diverse forms of retinoic acid (RA). The retinoic acid receptors (RARs) bind all-trans RA and its 9-cis isomer (9-cis RA). They convey most of the activity of RA, particularly during embryogenesis. The second subset of receptors, the rexinoid receptors (RXRs), binds 9-cis RA only. However, RXRs are obligatory DNA-binding partners for a number of nuclear receptors, broadening the spectrum of their biological activity to the corresponding nuclear receptor-signaling pathways. The present chapter more particularly focuses on RXR-containing transcriptional complexes for which RXR is not only a structural component necessary for DNA binding but also acts as a ligand-activated partner. After positioning RXR among the nuclear receptor superfamily in the first part, we will give an overview of three major signaling pathways involved in metabolism, which are sensitive to RXR activation: LXR:RXR, FXR:RXR, and PPAR:RXR. The third and last part is focused on RXR signaling and its potential role in metabolic regulation. Indeed, while the nature of the endogenous ligand for RXR is still in question, as we will discuss herein, a better understanding of RXR activities is necessary to envisage the potential therapeutic applications of synthetic RXR ligands.
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Affiliation(s)
- Béatrice Desvergne
- Center for Integrative Genomics, Building Génopode, University of Lausanne, CH-1015 Lausanne, Switzerland
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80
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Dullaart RPF, de Vries R, Dallinga-Thie GM, van Tol A, Sluiter WJ. Plasma cholesteryl ester transfer protein mass and phospholipid transfer protein activity are associated with leptin in type 2 diabetes mellitus. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:113-8. [PMID: 17185032 DOI: 10.1016/j.bbalip.2006.11.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 11/02/2006] [Accepted: 11/10/2006] [Indexed: 10/23/2022]
Abstract
Adipose tissue contributes to plasma levels of lipid transfer proteins and is also the major source of plasma adipokines. We hypothesized that plasma cholesteryl ester transfer protein (CETP) mass, phospholipid transfer protein (PLTP) activity and cholesteryl ester transfer (CET, a measure of CETP action) are determined by adipokine levels. In this study, relationships of plasma CETP mass, PLTP activity and CET with leptin, resistin and adiponectin were analyzed in type 2 diabetic patients and control subjects. Plasma PLTP activity (P<0.001), CET (P<0.001), leptin (P=0.003), resistin (P<0.001), high sensitive C-reactive protein (P=0.005), and insulin resistance (HOMA(ir)) (P<0.001) were higher, whereas HDL cholesterol (P<0.001) and plasma adiponectin (P<0.001) were lower in 83 type 2 diabetic patients (32 females) than in 83 sex-matched control subjects. Multiple linear regression analysis demonstrated that in diabetic patients plasma leptin levels were related to plasma CETP mass (P=0.018) and PLTP activity (P<0.001), but not to the other adipokines measured. Plasma CET was inversely correlated with adiponectin in univariate analysis, but this association disappeared in multivariate models that included plasma lipids and CETP. In conclusion, both plasma CETP mass and PLTP activity are associated with plasma leptin in type 2 diabetes. The elevated CET in these patients is not independently related to any of the measured plasma adipokines.
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Affiliation(s)
- R P F Dullaart
- Department of Endocrinology, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands
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81
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Ooi EMM, Watts GF, Ji J, Rye KA, Johnson AG, Chan DC, Barrett PHR. Plasma phospholipid transfer protein activity, a determinant of HDL kinetics in vivo. Clin Endocrinol (Oxf) 2006; 65:752-9. [PMID: 17121526 DOI: 10.1111/j.1365-2265.2006.02662.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Phospholipid transfer protein (PLTP) is an important regulator in the transport of surface components of triglyceride-rich lipoprotein (TRL) to high density lipoprotein (HDL) during lipolysis and may therefore play an important role in regulating HDL transport. In this study we investigated the relationship of plasma PLTP activity with HDL metabolism in men. DESIGN AND METHODS The kinetics of HDL LpA-I and LpA-I:A-II were measured using intravenous administration of [D3]-leucine, gas chromatography-mass spectrometry (GCMS) and a new multicompartmental model for HDL subpopulation kinetics (SAAM II) in 31 men with wide-ranging body mass index (BMI 18-46 kg/m2). Plasma PLTP activity was determined as the transfer of radiolabelled phosphatidylcholine from small unilamellar phosphatidylcholine vesicles to ultracentrifugally isolated HDL. RESULTS PLTP activity was inversely associated with LpA-I concentration and production rate (PR) after adjusting for insulin resistance (P < 0.05). No significant associations were observed between plasma PLTP activity and LpA-I fractional catabolic rate (FCR). In multivariate analysis, including homeostasis model assessment score (HOMA), triglyceride, cholesteryl ester transfer protein (CETP) activity and PLTP activity, PLTP activity was the only significant determinant of LpA-I concentration and PR (P = 0.020 and P = 0.016, respectively). CONCLUSIONS Plasma PLTP activity may be a significant, independent determinant of LpA-I kinetics in men, and may contribute to the maintenance of the plasma concentration of these lipoprotein particles in setting of hypercatabolism of HDL.
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Affiliation(s)
- Esther M M Ooi
- Metabolic Research Centre, School of Medicine and Pharmacology, Royal Perth Hospital, University of Western Australia, WA, Australia
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82
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Das A, Fernandez-Zapico ME, Cao S, Yao J, Fiorucci S, Hebbel RP, Urrutia R, Shah VH. Disruption of an SP2/KLF6 repression complex by SHP is required for farnesoid X receptor-induced endothelial cell migration. J Biol Chem 2006; 281:39105-13. [PMID: 17071613 DOI: 10.1074/jbc.m607720200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The farnesoid X receptor (FXR) signaling pathway regulates bile acid and cholesterol homeostasis. Here, we demonstrate, using a variety of gain- and loss-of-function approaches, a role of FXR in the process of cell motility, which involves the small heterodimeric partner (SHP)-dependent up-regulation of matrix metalloproteinase-9. We use this observation to reveal a transcriptional regulatory mechanism involving the SP/KLF transcription factors, SP2 and KLF6. Small interference RNA-based silencing studies in combination with promoter, gel shift, and chromatin immunoprecipitation assays indicate that SP2 and KLF6 bind to the matrix metalloproteinase-9 promoter and together function to maintain this gene in a silenced state. However, upon activation of FXR, SHP interacts with SP2 and KLF6, disrupting the SP2/KLF6 repressor complex. Thus, together, these studies identify a mechanism for antagonizing Sp/KLF protein repression function via SHP, with this process regulating endothelial cell motility.
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Affiliation(s)
- Amitava Das
- Gastroenterology Research Unit, Department of Physiology and Cancer Cell Biology Program, Mayo Clinic, Rochester, Minnesota 55905, USA.
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83
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Guo GL, Santamarina-Fojo S, Akiyama TE, Amar MJ, Paigen BJ, Brewer B, Gonzalez FJ. Effects of FXR in foam-cell formation and atherosclerosis development. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1401-9. [PMID: 17110163 PMCID: PMC1751860 DOI: 10.1016/j.bbalip.2006.09.018] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 09/06/2006] [Accepted: 09/25/2006] [Indexed: 01/31/2023]
Abstract
Farnesoid X receptor (FXR), a bile-acid-activated member of the nuclear receptor superfamily, is essential in regulating bile-acid, cholesterol, and triglyceride homeostasis. Disruption of the FXR gene in mice results in a proatherosclerotic lipid profile with increased serum cholesterols and triglycerides. However, the role of FXR in foam-cell formation and atherosclerosis development remains unclear. The current study showed that the peritoneal macrophages isolated from FXR-null mice took up less oxidized LDL-cholesterol (oxLDL-C), which was accompanied by a marked reduction in CD36 expression in these cells. This result appears to be FXR-independent, as FXR was not detected in the peritoneal macrophages. To assess to what extent FXR modulates atherosclerosis development, FXR/ApoE double-null mice were generated. Female mice were used for atherosclerosis analysis. Compared to ApoE-null mice, the FXR/ApoE double-null mice were found to have less atherosclerotic lesion area in the aorta, despite a further increase in the serum cholesterols and triglycerides. Our results indicate that disruption of the FXR gene could attenuate atherosclerosis development, most likely resulting from reduced oxLDL-C uptake by macrophages. Our study cautions the use of serum lipid levels as a surrogate marker to determine the efficiency of FXR modulators in treating hyperlipidemia.
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MESH Headings
- Animals
- Apolipoproteins E/deficiency
- Apolipoproteins E/genetics
- Atherosclerosis/etiology
- Atherosclerosis/genetics
- Atherosclerosis/metabolism
- Atherosclerosis/pathology
- Biological Transport, Active
- Cholesterol, LDL/metabolism
- Cytokines/biosynthesis
- DNA-Binding Proteins/deficiency
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Female
- Foam Cells/metabolism
- Foam Cells/pathology
- Gene Expression
- Homeostasis
- In Vitro Techniques
- Lipids/blood
- Lipoproteins, LDL/metabolism
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Receptors, Cytoplasmic and Nuclear/deficiency
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Transcription Factors/deficiency
- Transcription Factors/genetics
- Transcription Factors/metabolism
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Affiliation(s)
- Grace L. Guo
- Laboratory of Metabolism, NCI, NIH, 9000 Rockville Pike, Bethesda, MD 20892
| | | | - Taro E. Akiyama
- Laboratory of Metabolism, NCI, NIH, 9000 Rockville Pike, Bethesda, MD 20892
| | - Marcelo J.A. Amar
- Molecular Disease Branch, NHLBI, NIH, 9000 Rockville Pike, Bethesda, MD 20892
| | | | - Bryan Brewer
- Molecular Disease Branch, NHLBI, NIH, 9000 Rockville Pike, Bethesda, MD 20892
| | - Frank J. Gonzalez
- Laboratory of Metabolism, NCI, NIH, 9000 Rockville Pike, Bethesda, MD 20892
- Address correspondence to: Frank J. Gonzalez, Bldg. 37, Rm. 3106B, NCI, NIH, 9000 Rockville Pike, Bethesda, MD, (Tel) 301-496-9067, (Fax) 301-496-8419, (E-mail)
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84
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Nam SJ, Ko H, Shin M, Ham J, Chin J, Kim Y, Kim H, Shin K, Choi H, Kang H. Farnesoid X-activated receptor antagonists from a marine sponge Spongia sp. Bioorg Med Chem Lett 2006; 16:5398-402. [PMID: 16905319 DOI: 10.1016/j.bmcl.2006.07.079] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 07/18/2006] [Accepted: 07/20/2006] [Indexed: 10/24/2022]
Abstract
Three novel (1-3) and two known (4-5) scalarane sesterterpenes were isolated from a marine sponge of the genus Spongia. The isolated compounds showed potent inhibition of transactivation for the nuclear hormone receptor, FXR (farnesoid X-activated receptor), which is a promising drug target to treat hypercholesterolemia in humans.
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Affiliation(s)
- Sang-Jip Nam
- Center for Marine Natural Products and Drug Discovery, School of Earth and Environmental Sciences, Seoul National University, NS-80, Seoul, 151-747, Republic of Korea
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85
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Rizzo G, Disante M, Mencarelli A, Renga B, Gioiello A, Pellicciari R, Fiorucci S. The farnesoid X receptor promotes adipocyte differentiation and regulates adipose cell function in vivo. Mol Pharmacol 2006; 70:1164-73. [PMID: 16778009 DOI: 10.1124/mol.106.023820] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The differentiation of a preadipocyte into a mature adipocyte is a highly regulated process that requires a scripted program of transcriptional events leading to changes in gene expression. Several genes are associated with adipogenesis, including the CAAT/enhancer-binding protein (C/EBPs) and peroxisome proliferator-activated receptor (PPAR) families of transcription factors. In this study, we have investigated the role of the farnesoid X receptor (FXR), a bile acid-activated nuclear receptor, in regulating adipogenesis in a preadipocyte cell line (3T3-L1 cells). Our results show that FXR is expressed in the white adipose tissue of adult mice and in differentiated 3T3-L1 cells but not in undifferentiated preadipocytes. Exposure of 3T3-L1 cells to INT-747 (6-ethyl cheno-deoxycholic acid), a potent and selective FXR ligand, increases preadipocyte differentiation induced by a differentiating mixture containing insulin. Augmentation of differentiating mixture-induced differentiation of 3T3-L1 cells by INT-747 associated with induction of aP2, C/EBPalpha, and PPARgamma2 mRNAs along with other adipocyte-related genes. This effect was reversed by guggulsterone, an FXR antagonist, and partially reverted by GW9662 (2-chloro-5-nitro-N-phenylbenzamide), a selective PPARgamma antagonist, indicating that FXR modulates adipocyte-related genes by PPARgamma-dependent and -independent pathways. Regulation of adipocyte-related genes by INT-747 was lost in FXR-/- mice, indicating that modulation of these genes by INT-747 requires an intact FXR. In addition, INT-747 enhances both insulin-induced serine phosphorylation of Akt and glucose uptake by 3T3-L1 cells. Taken together, these results suggest that activation of FXR plays a critical role in regulating adipogenesis and insulin signaling.
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Affiliation(s)
- Giovanni Rizzo
- Dipartimento di Medicina Clinica e Sperimentale, University of Perugia, Via E dal Pozzo, 06122 Perugia, Italy
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86
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Suzuki T, Nishimaki-Mogami T, Kawai H, Kobayashi T, Shinozaki Y, Sato Y, Hashimoto T, Asakawa Y, Inoue K, Ohno Y, Hayakawa T, Kawanishi T. Screening of novel nuclear receptor agonists by a convenient reporter gene assay system using green fluorescent protein derivatives. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2006; 13:401-11. [PMID: 16716909 DOI: 10.1016/j.phymed.2005.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Accepted: 04/06/2005] [Indexed: 05/09/2023]
Abstract
Nuclear receptors represent a very good family of protein targets for the prevention and treatment of diverse diseases. In this study, we screened natural compounds and their derivatives, and discovered ligands for the retinoic acid receptors (RARs) and the farnesoid X receptor (FXR). In the reporter assay systems of nuclear receptors presented here, two fluorescent proteins, enhanced yellow fluorescent protein (EYFP) and enhanced cyan fluorescent protein (ECFP), were used for detection of a ligand-based induction and as an internal control, respectively. By optimizing the conditions (e.g., of hormone response elements and promoter genes for reporter plasmids), we established a battery of assay systems for ligands of RARs, retinoid X receptor (RXR) and FXR. The screening using the reporter assay system can be carried out without the addition of co-factors or substrates. As a result of screening of more than 140 compounds, several compounds were detected which activate RARs and/or FXR. Caffeic acid phenylethyl ester (CAPE), known as a component of propolis from honeybee hives, and other derivatives of caffeic acid up-regulated the expression of reporter gene for RARs. Grifolin and ginkgolic acids, which are non-steroidal skeleton compounds purified from mushroom or ginkgo leaves, up-regulated the expression of the reporter gene for FXR.
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Affiliation(s)
- T Suzuki
- National Institute of Health Sciences, Tokyo, Japan
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87
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Abstract
PURPOSE OF REVIEW Plasma cholesteryl ester transfer protein and phospholipid transfer protein are involved in lipoprotein metabolism. Conceivably, manipulation of either transfer protein could impact atherosclerosis and other lipid-driven diseases. RECENT FINDINGS Cholesteryl ester transfer protein mediates direct HDL cholesteryl ester delivery to the liver cells; adipose tissue-specific overexpression of cholesteryl ester transfer protein in mice reduces the plasma HDL cholesterol concentration and adipocyte size; cholesteryl ester transfer protein TaqIB polymorphism is associated with HDL cholesterol plasma levels and the risk of coronary heart disease. In apolipoprotein B transgenic mice, phospholipid transfer protein deficiency enhances reactive oxygen species-dependent degradation of newly synthesized apolipoprotein B via a post-endoplasmic reticulum process, as well as improving the antiinflammatory properties of HDL in mice. Activity of this transfer protein in cerebrospinal fluid of patients with Alzheimer's disease is profoundly decreased and exogenous phospholipid transfer protein induces apolipoprotein E secretion by primary human astrocytes in vitro. SUMMARY Understanding the relationship between lipid transfer proteins and lipoprotein metabolism is expected to be an important frontier in the search for a therapy for atherosclerosis.
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Affiliation(s)
- Xian-Cheng Jiang
- Department of Anatomy and Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York, USA.
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88
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Abstract
The nuclear farnesoid X receptor (FXR) plays a pivotal role in maintaining bile acid homeostasis by regulating key genes involved in bile acid synthesis, metabolism and transport, including CYP7A1, UGT2B4, BSEP, MDR3, MRP2, ASBT, I-BABP, NTCP and OSTalpha-OSTbeta in humans. Altered expression or malfunction of these genes has been described in patients with cholestatic liver diseases. This review examines the rationale for the use of FXR ligand therapy in various cholestatic liver disorders and includes potential concerns.
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Affiliation(s)
- Shi-Ying Cai
- Liver Center, Department of Medicine, Yale University School of Medicine, P.O. Box 208019, New Haven, CT 06520-8019, USA
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89
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Abstract
Our understanding of metabolism is undergoing a dramatic shift. Indeed, the efforts made towards elucidating the mechanisms controlling the major regulatory pathways are now being rewarded. At the molecular level, the crucial role of transcription factors is particularly well-illustrated by the link between alterations of their functions and the occurrence of major metabolic diseases. In addition, the possibility of manipulating the ligand-dependent activity of some of these transcription factors makes them attractive as therapeutic targets. The aim of this review is to summarize recent knowledge on the transcriptional control of metabolic homeostasis. We first review data on the transcriptional regulation of the intermediary metabolism, i.e., glucose, amino acid, lipid, and cholesterol metabolism. Then, we analyze how transcription factors integrate signals from various pathways to ensure homeostasis. One example of this coordination is the daily adaptation to the circadian fasting and feeding rhythm. This section also discusses the dysregulations causing the metabolic syndrome, which reveals the intricate nature of glucose and lipid metabolism and the role of the transcription factor PPARgamma in orchestrating this association. Finally, we discuss the molecular mechanisms underlying metabolic regulations, which provide new opportunities for treating complex metabolic disorders.
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Affiliation(s)
- Béatrice Desvergne
- Center for Integrative Genomics, National Centre of Competence in Research Frontiers in Genetics, University of Lausanne, Lausanne, Switzerland
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90
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Bilz S, Samuel V, Morino K, Savage D, Choi CS, Shulman GI. Activation of the farnesoid X receptor improves lipid metabolism in combined hyperlipidemic hamsters. Am J Physiol Endocrinol Metab 2006; 290:E716-22. [PMID: 16291572 DOI: 10.1152/ajpendo.00355.2005] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The transcription factor farnesoid X receptor (FXR) has recently been implicated in the control of hepatic triglyceride production. Activation of FXR may ameliorate hypertriglyceridemia, a cardinal feature of the metabolic syndrome. Because hamsters share many characteristic features of human lipid metabolism, we used a high-fructose-fed hamster model to study the impact of FXR activation with chenodeoxycholic acid (CDCA) on plasma lipoprotein metabolism. Male Syrian hamsters fed a diet containing 60% kcal from fructose for 2 wk developed hypertriglyceridemia and hypercholesterolemia (+120 and +60%, P = 0.005 and 0.0004 vs. controls) due to increased hepatic lipoprotein production. This could be largely attributed to enhanced hepatic de novo lipogenesis, as indicated by increased expression of sterol regulatory element-binding protein-1, fatty acid synthase, and steaoryl-CoA desaturase-1. Lipoprotein analysis demonstrated that the increase in plasma triglycerides occurred in the VLDL density range, whereas increases in VLDL, IDL/LDL, and HDL cholesterol accounted for the elevated plasma cholesterol concentrations. Addition of 0.1% CDCA to the high-fructose diet decreased hepatic de novo lipogenesis and consequently triglyceride production and prevented the increases in plasma triglycerides and cholesterol (-40 and -18%, P = 0.03 and 0.03 vs. high fructose-fed animals). CDCA-treated animals had lower VLDL triglycerides and decreased VLDL and IDL/LDL cholesterol plasma concentrations. These data demonstrate that activation of FXR with CDCA effectively lowers plasma triglyceride and cholesterol concentrations, mainly by decreasing de novo lipogenesis and hepatic secretion of triglyceride-rich lipoproteins. Our studies identify activators of FXR as promising new tools in the therapy of hypertriglyceridemic states, including the insulin resistance syndrome and type 2 diabetes.
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Affiliation(s)
- Stefan Bilz
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06536-8012, USA
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91
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Ma K, Saha PK, Chan L, Moore DD. Farnesoid X receptor is essential for normal glucose homeostasis. J Clin Invest 2006; 116:1102-9. [PMID: 16557297 PMCID: PMC1409738 DOI: 10.1172/jci25604] [Citation(s) in RCA: 655] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 01/31/2006] [Indexed: 12/13/2022] Open
Abstract
The bile acid receptor farnesoid X receptor (FXR; NR1H4) is a central regulator of bile acid and lipid metabolism. We show here that FXR plays a key regulatory role in glucose homeostasis. FXR-null mice developed severe fatty liver and elevated circulating FFAs, which was associated with elevated serum glucose and impaired glucose and insulin tolerance. Their insulin resistance was confirmed by the hyperinsulinemic euglycemic clamp, which showed attenuated inhibition of hepatic glucose production by insulin and reduced peripheral glucose disposal. In FXR-/- skeletal muscle and liver, multiple steps in the insulin signaling pathway were markedly blunted. In skeletal muscle, which does not express FXR, triglyceride and FFA levels were increased, and we propose that their inhibitory effects account for insulin resistance in that tissue. In contrast to the results in FXR-/- mice, bile acid activation of FXR in WT mice repressed expression of gluconeogenic genes and decreased serum glucose. The absence of this repression in both FXR-/- and small heterodimer partner-null (SHP-/-) mice demonstrated that the previously described FXR-SHP nuclear receptor cascade also targets glucose metabolism. Taken together, our results identify a link between lipid and glucose metabolism mediated by the FXR-SHP cascade.
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Affiliation(s)
- Ke Ma
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Pradip K. Saha
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Lawrence Chan
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - David D. Moore
- Department of Molecular and Cellular Biology and
Section of Endocrinology and Metabolism, Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine, Houston, Texas, USA
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92
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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] [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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93
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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: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [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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94
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Abstract
Liver X receptors (LXRs) and farnesoid X receptor (FXR) are nuclear receptors that function as intracellular sensors for sterols and bile acids, respectively. In response to their ligands, these receptors induce transcriptional responses that maintain a balanced, finely tuned regulation of cholesterol and bile acid metabolism. LXRs also permit the efficient storage of carbohydrate- and fat-derived energy, whereas FXR activation results in an overall decrease in triglyceride levels and modulation of glucose metabolism. The elegant, dual interplay between these two receptor systems suggests that they coevolved to constitute a highly sensitive and efficient system for the maintenance of total body fat and cholesterol homeostasis. Emerging evidence suggests that the tissue-specific action of these receptors is also crucial for the proper function of the cardiovascular, immune, reproductive, endocrine pancreas, renal, and central nervous systems. Together, LXRs and FXR represent potential therapeutic targets for the treatment and prevention of numerous metabolic and lipid-related diseases.
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Affiliation(s)
- Nada Y Kalaany
- Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
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95
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Pellicciari R, Costantino G, Fiorucci S. Farnesoid X receptor: from structure to potential clinical applications. J Med Chem 2005; 48:5383-403. [PMID: 16107136 DOI: 10.1021/jm0582221] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Roberto Pellicciari
- Dipartimento di Chimica e Tecnologia del Farmaco, Università di Perugia, Via del Liceo 1, I-06123 Perugia, Italy.
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96
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Meyer U, Costantino G, Macchiarulo A, Pellicciari R. Is Antagonism of E/Z-Guggulsterone at the Farnesoid X Receptor Mediated by a Noncanonical Binding Site? A Molecular Modeling Study. J Med Chem 2005; 48:6948-55. [PMID: 16250653 DOI: 10.1021/jm0505056] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Guggulsterone 1, the active principle of guggulipid, has been used in ethnic medicine for thousands of years for its antinflammatory and antilipidemic activities. The activities of 1 are apparently mediated by its interaction with an array of nuclear receptors, including endocrine steroid receptors and metabolic lipid receptors. Although relatively weak, the activity at the metabolic farnesoid X receptor (FXR) is particularly intriguing, as 1 is, so far, the only antagonist known for this receptor, with a peculiar ability of gene selective modulation. We report here a systematic study aimed at identifying the potential binding pocket of 1 at FXR. Although 1 could be docked into the canonical binding site, we identified a novel, so far undescribed binding pocket, localized near the loop region between helix 1 and helix 2. This novel binding pocket may explain some of the peculiar characteristics of 1 when acting at FXR.
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Affiliation(s)
- Udo Meyer
- Dipartimento di Chimica e Tecnologia del Farmaco, Università di Perugia, Via del Liceo 1, I-06123 Perugia, Italy
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97
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Kreeft AJ, Moen CJA, Porter G, Kasanmoentalib S, Sverdlov R, van Gorp PJ, Havekes LM, Frants RR, Hofker MH. Genomic analysis of the response of mouse models to high-fat feeding shows a major role of nuclear receptors in the simultaneous regulation of lipid and inflammatory genes. Atherosclerosis 2005; 182:249-57. [PMID: 16159597 DOI: 10.1016/j.atherosclerosis.2005.01.049] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Revised: 01/14/2005] [Accepted: 01/27/2005] [Indexed: 10/25/2022]
Abstract
The mechanisms of diet induced hyperlipidemia and atherosclerosis have been widely studied by delineating the role of candidate genes in transgenic and gene targeted mouse models. However, diet induced hyperlipidemia represents a complex process determined by many lipid genes that is only partly understood. This study is aimed at delineating the events induced by dietary intervention in different mouse models at the level of gene expression using microarray analysis. The focus is on the liver as the organ primarily responding to diet, and crucial in determining plasma lipid levels. Firstly, the effect of the genotype was studied. Expression profiles of liver genes were compared between APOE3Leiden (E3L), APOE knockout (E-/-) and C57BL/6JIco (B6) mice using the Incyte GEM 2.03 array carrying 9552 genes. Several hundred differentially expressed genes were identified indicating that the genotype alone effects gene expression. Secondly, the response of E3L mice to high-fat feeding was investigated using a mild and severe high-fat diet (diet W and N, respectively). Diet W caused differential regulation of 200 genes, while diet N affected the expression of 788 genes in B6 and 1010 genes in E3L mice. Annotation of these genes using the Gene Ontology (GO) database showed that two major processes were strongly affected by genotype and diet, namely lipid metabolism and inflammation, the latter as determined by "immune/defense response and detoxification" processes. Many nuclear receptor target genes were differentially regulated, with the largest effects modulated by the severe high-fat diet N, leading to the suppression of genes involved in bile acid, sterol, steroid, fatty acid, and detoxification metabolism. Strikingly, a substantial part of these nuclear receptor target genes were commonly regulated during the different experimental conditions. The common regulation of many nuclear receptor target genes underlying lipid and detoxification processes as found in this study, suggest a defense mechanism involving many nuclear receptors to protect against the accumulation of toxic endogenous lipids and bile acids. These results further strengthen the close link between hyperlipidemia and inflammatory processes.
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Affiliation(s)
- Arja J Kreeft
- Department of Human and Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
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98
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Bungard CI, McGivan JD. Identification of the promoter elements involved in the stimulation of ASCT2 expression by glutamine availability in HepG2 cells and the probable involvement of FXR/RXR dimers. Arch Biochem Biophys 2005; 443:53-9. [PMID: 16197915 DOI: 10.1016/j.abb.2005.08.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Revised: 08/22/2005] [Accepted: 08/26/2005] [Indexed: 11/26/2022]
Abstract
Expression of the glutamine transport protein ASCT2 in the human hepatoma cell line HepG2 is increased when cells are cultured in the presence of glutamine and this has been shown to be due to stimulation of the ASCT2 promoter. Analysis of a number of promoter constructs localised the activation site to be between bases -653 and -543. Gel shift assays identified an IR-1 repeat within a 24bp region of this sequence which bound at least two nuclear proteins. Protein binding to this site was significantly higher in cells grown in glutamine-containing medium than when glutamine was absent. The identity of the higher molecular weight species binding to this promoter element was likely to be FXR/RXR dimers. Simultaneous overexpression of FXR and RXR increased the promoter activity in cells grown without glutamine to the same extent as did glutamine addition; the effects of glutamine and FXR/RXR expression were not additive. Mutagenesis of the FXR/RXR binding site in the promoter construct abolished glutamine and FXR/RXR stimulation. Real-time PCR showed levels of FXR mRNA were significantly increased in response to glutamine. The activity of the FXR promoter was also increased in response to glutamine. These results show that the stimulation of ASCT2 expression in response to glutamine in part involves binding of FXR/RXR to the ASCT2 promoter.
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Affiliation(s)
- Claire I Bungard
- Department of Biochemistry, Medical School, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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99
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Chignard N, Mergey M, Barbu V, Finzi L, Tiret E, Paul A, Housset C. VPAC1 expression is regulated by FXR agonists in the human gallbladder epithelium. Hepatology 2005; 42:549-57. [PMID: 16037943 DOI: 10.1002/hep.20806] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Vasoactive intestinal peptide receptor-1 (VPAC1) is the high-affinity receptor of vasoactive intestinal peptide (VIP), a major regulator of bile secretion. To better define the level at which VPAC1 stimulates bile secretion, we examined its expression in the different cell types participating in bile formation (i.e., hepatocytes, bile duct, and gallbladder epithelial cells). Because VPAC1 expression was previously shown to be regulated by nuclear receptors, we tested the hypothesis that it may be regulated by the farnesoid X receptor (FXR). Quantitative RT-PCR and immunoblot analyses of cell isolates indicated that VPAC1 is expressed in all three cell types lining the human biliary tree, with predominant expression in the gallbladder. In primary cultures of human gallbladder epithelial cells, VIP induced cAMP production and chloride secretion. Analysis of the VPAC1 gene revealed the presence of potential FXR response element sequences, and both FXR and RXRalpha expressions were detected in gallbladder epithelial cells. In these cells, the FXR pharmacological agonist GW4064 upregulated VPAC1 expression in a dose-dependent manner, and this effect was antagonized by the RXRalpha ligand, 9-cis retinoic acid. Chenodeoxycholate activated endogenous FXR in gallbladder epithelial cells, as ascertained by electromobility shift assay and upregulation of the FXR target gene, small heterodimer partner. Chenodeoxycholate also provoked an increase in VPAC1 mRNA and protein content in these cells. In conclusion, FXR agonists may increase gallbladder fluid secretion through transcriptional activation of VPAC1, which may contribute to the regulation of bile secretion by bile salts and to a protective effect of FXR pharmacological agonists in gallstone disease.
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Affiliation(s)
- Nicolas Chignard
- Inserm, Paris, France, and Université Pierre et Marie Curie, Paris, France
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100
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Affiliation(s)
- Andrew I Shulman
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75390, USA
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