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Zhang J, Xu X, Kuang H, Xu C, Wu X. Potential health risk analysis of chlorantraniliprole in vivo. Sci Bull (Beijing) 2023; 68:2712-2716. [PMID: 37758618 DOI: 10.1016/j.scib.2023.08.061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 07/29/2023] [Accepted: 08/18/2023] [Indexed: 09/29/2023]
Affiliation(s)
- Jia Zhang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China; International Joint Research Laboratory for Biointerface and Biodetection and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China
| | - Xinxin Xu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China; International Joint Research Laboratory for Biointerface and Biodetection and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China.
| | - Hua Kuang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China; International Joint Research Laboratory for Biointerface and Biodetection and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China
| | - Chuanlai Xu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China; International Joint Research Laboratory for Biointerface and Biodetection and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China
| | - Xiaoling Wu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China; International Joint Research Laboratory for Biointerface and Biodetection and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China.
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Farooqui N, Elhence A, Shalimar. A Current Understanding of Bile Acids in Chronic Liver Disease. J Clin Exp Hepatol 2022; 12:155-173. [PMID: 35068796 PMCID: PMC8766695 DOI: 10.1016/j.jceh.2021.08.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 08/16/2021] [Indexed: 01/03/2023] Open
Abstract
Chronic liver disease (CLD) is one of the leading causes of disability-adjusted life years in many countries. A recent understanding of nuclear bile acid receptor pathways has increased focus on the impact of crosstalk between the gut, bile acids, and liver on liver pathology. While conventionally used in cholestatic disorders and to dissolve gallstones, the discovery of bile acids' influence on the gut microbiome and human metabolism offers a unique potential for their utility in early and advanced liver diseases because of diverse etiologies. Based on these findings, preclinical studies using bile acid-based molecules have shown encouraging results at addressing liver inflammation and fibrosis. Emerging data also suggest that bile acid profiles change distinctively across various causes of liver disease. We summarize the current knowledge and evidence related to bile acids in health and disease and discuss culminated and ongoing therapeutic trials of bile acid derivatives in CLD. In the near future, further evidence in this area might help clinicians better detect and manage liver diseases.
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Key Words
- AD, Acute decompensation
- ALP, Alkaline phosphatase
- AMACR, α-methylacyl-CoA racemase (AMACR)
- ASBT, Apical sodium dependent bile salt transporter
- BA, Bile acid
- BSEP, Bile salt export pump
- BSH, Bile salt hydrolase
- CA, Cholic acid
- CDCA, Chenodeoxycholic acid
- CLD
- CLD, Chronic Liver Disease
- CTP, Child-Turcotte-Pugh
- CYP7A1, Cholesterol 7 α hydroxylase
- DCA, Deoxycholic acid
- DR5, Death receptor 5
- ELF, Enhanced Liver Fibrosis
- FGF-19, Fibroblast growth factor-19
- FGFR4, FGF receptor 4
- FXR, Farnesoid X receptor
- GCA, Glycocholic acid
- GDCA, Glycodeoxycholic acid
- GLP-1, Glucagon-like peptide1
- HBV, Hepatitis B virus
- HCV, Hepatitis C virus
- HVPG, Hepatic Venous Pressure Gradient
- LCA, Lithocholic acid
- LPS, Lipopolysaccharide
- MELD, Model for End-Stage Liver Disease (MELD)
- MRI-PDFF, Magnetic resonance imaging derived proton density fat fraction
- NAFLD
- NAFLD, Non-alcoholic fatty liver disease
- NAS, NAFLD activity score
- NASH, Nonalcoholic steatohepatitis
- NTCP, Sodium taurocholate cotransporting polypeptide
- OCA, Obeticholic acid
- OST, Organic solute transporter
- PBC, Primary biliary cirrhosis
- PFIC, Progressive familial intrahepatic cholestasis
- PSC, Primary sclerosing cholangitis
- PXR, Pregnane X receptor
- SHP, Small heterodimer partner
- TBA, Total bile acids
- TGR5, Takeda G-protein coupled receptor 5
- TRAIL, TNF-related apoptosis-inducing ligand
- UDCA, Ursodeoxycholic acid
- UPLC-MS, Ultra-performance liquid chromatography with tandem mass spectrometry
- VDR, Vitamin D receptor
- bile acids
- cirrhosis
- microbiome
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Affiliation(s)
- Naba Farooqui
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
| | - Anshuman Elhence
- Department of Gastroenterology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India
| | - Shalimar
- Department of Gastroenterology and Human Nutrition, All India Institute of Medical Sciences, New Delhi, India
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Gaillard D, Masson D, Garo E, Souidi M, Pais de Barros JP, Schoonjans K, Grober J, Besnard P, Thomas C. Muricholic Acids Promote Resistance to Hypercholesterolemia in Cholesterol-Fed Mice. Int J Mol Sci 2021; 22:7163. [PMID: 34281217 PMCID: PMC8269105 DOI: 10.3390/ijms22137163] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/25/2021] [Accepted: 06/28/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND AIMS Hypercholesterolemia is a major risk factor for atherosclerosis and cardiovascular diseases. Although resistant to hypercholesterolemia, the mouse is a prominent model in cardiovascular research. To assess the contribution of bile acids to this protective phenotype, we explored the impact of a 2-week-long dietary cholesterol overload on cholesterol and bile acid metabolism in mice. METHODS Bile acid, oxysterol, and cholesterol metabolism and transport were assessed by quantitative real-time PCR, western blotting, GC-MS/MS, or enzymatic assays in the liver, the gut, the kidney, as well as in the feces, the blood, and the urine. RESULTS Plasma triglycerides and cholesterol levels were unchanged in mice fed a cholesterol-rich diet that contained 100-fold more cholesterol than the standard diet. In the liver, oxysterol-mediated LXR activation stimulated the synthesis of bile acids and in particular increased the levels of hydrophilic muricholic acids, which in turn reduced FXR signaling, as assessed in vivo with Fxr reporter mice. Consequently, biliary and basolateral excretions of bile acids and cholesterol were increased, whereas portal uptake was reduced. Furthermore, we observed a reduction in intestinal and renal bile acid absorption. CONCLUSIONS These coordinated events are mediated by increased muricholic acid levels which inhibit FXR signaling in favor of LXR and SREBP2 signaling to promote efficient fecal and urinary elimination of cholesterol and neo-synthesized bile acids. Therefore, our data suggest that enhancement of the hydrophilic bile acid pool following a cholesterol overload may contribute to the resistance to hypercholesterolemia in mice. This work paves the way for new therapeutic opportunities using hydrophilic bile acid supplementation to mitigate hypercholesterolemia.
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Affiliation(s)
- Dany Gaillard
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- Department of Cell & Developmental Biology, and The Rocky Mountain Taste & Smell Center, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - David Masson
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- LipSTIC LabEx, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France
- Biochemistry Department, University Hospital François Mitterrand, 21000 Dijon, France
| | - Erwan Garo
- IGBMC, CNRS UMR 7104, INSERM U 1258, 67400 Illkirch, France;
| | - Maamar Souidi
- Institut de Radioprotection et de Sûreté Nucléaire (IRSN), 92260 Fontenay-aux-Roses, France;
| | - Jean-Paul Pais de Barros
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- LipSTIC LabEx, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France
- Lipidomic Facility, Université de Bourgogne Franche-Comté (UBFC), 21078 Dijon, France
| | - Kristina Schoonjans
- Institute of Bioengineering, Life Science Faculty, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland;
| | - Jacques Grober
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- LipSTIC LabEx, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France
| | - Philippe Besnard
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- LipSTIC LabEx, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France
- Physiologie de la Nutrition, AgroSup Dijon, 21000 Dijon, France
| | - Charles Thomas
- Center for Translational Medicine, UMR1231 INSERM-uB-AgroSupDijon, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France; (D.G.); (D.M.); (J.-P.P.d.B.); (J.G.)
- LipSTIC LabEx, Université de Bourgogne Franche-Comté (UBFC), 21000 Dijon, France
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Meng F, Zong W, Wei X, Tao Y, Wang G, Liao Z, Chen M. Dolomiaea souliei ethyl acetate extract protected against α-naphthylisothiocyanate-induced acute intrahepatic cholestasis through regulation of farnesoid x receptor-mediated bile acid metabolism. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2021; 87:153588. [PMID: 34091148 DOI: 10.1016/j.phymed.2021.153588] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/25/2021] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Cholestasis is characterized by accumulation of bile components in liver and systemic circulation. Restoration of bile acid homeostasis via activating farnesoid x receptor (FXR) is a promising strategy for the treatment of cholestasis. FXR-SHP (small heterodimer partner) axis plays an important role in maintaining bile acid homeostasis. PURPOSE To investigate the anti-cholestasis effect of Dolomiaea souliei (Franch.) C.Shih (D. souliei) and clarify its underlying mechanism against α-naphthylisothiocyanate (ANIT) induced acute intrahepatic cholestasis. METHODS ANIT-induced Sprague-Dawley rats were employed to investigate the anti-cholestasis effect of D. souliei ethyl acetate extract (DSE). Ursodeoxycholic acid (UDCA) was used as positive control. Bile flow and blood biochemical parameters were measured. Liver histopathological examination was conducted via hematoxylin-eosin staining. Western blot analysis was carried out to evaluate the protein levels related to bile acids metabolism and inflammation. The interactions between FXR and costunolide or dehydrocostus lactone, were conducted by molecular docking experiments. The effect of costunolide and dehydrocostus lactone on aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels and FXR expression were also evaluated using guggulsterone-induced L02 cells. RESULTS DSE could promote bile excretions and protect against ANIT-induced liver damage in cholestasis rats. Protein levels of FXR, SHP, Na+/taurocholate cotransporter (NTCP), bile salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2) were increased and the expressions of cholesterol 7α-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) were decreased by DSE. Meanwhile, the anti-inflammatory factors, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) were also significantly increased, and the pro-inflammatory factor, interleukin-10 (IL-10), was significantly decreased in rats of DSE groups. Molecular docking revealed that costunolide and dehydrocostus lactone could be well docked into the FXR protein molecule, and hydrophobic interactions played the main function. Costunolide could reverse the increased AST and ALT levels and increase the FXR expression in guggulsterone-induced L02 cells. CONCLUSION DSE had an anti-cholestasis effect by activating FXR-SHP axis, inhibiting synthesis of bile acid, and increasing bile secretion, together with inflammatory response and improving liver injury. Costunolide may be the main active component. This study provided a potential therapeutic mechanism for D. souliei as an anti-cholestasis medicine in the treatment of cholestasis liver diseases.
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Affiliation(s)
- FanCheng Meng
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - Wei Zong
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - XiaoDong Wei
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - YunYi Tao
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - GuoWei Wang
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - ZhiHua Liao
- School of Life Sciences, Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China
| | - Min Chen
- College of Pharmaceutical Sciences, Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), Southwest University, No. 2 Tiansheng Road, Chongqing 400715, P.R. China.
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Chow MD, Lee YH, Guo GL. The role of bile acids in nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Mol Aspects Med 2017; 56:34-44. [PMID: 28442273 DOI: 10.1016/j.mam.2017.04.004] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 04/11/2017] [Accepted: 04/20/2017] [Indexed: 12/14/2022]
Abstract
Nonalcoholic fatty liver disease is growing in prevalence worldwide. It is marked by the presence of macrosteatosis on liver histology but is often clinically asymptomatic. However, it can progress into nonalcoholic steatohepatitis which is a more severe form of liver disease characterized by inflammation and fibrosis. Further progression leads to cirrhosis, which predisposes patients to hepatocellular carcinoma or liver failure. The mechanism by which simple steatosis progresses to steatohepatitis is not entirely clear. However, multiple pathways have been proposed. A common link amongst many of these pathways is disruption of the homeostasis of bile acids. Other than aiding in the absorption of lipids and lipid-soluble vitamins, bile acids act as ligands. For example, they bind to farnesoid X receptor, which is critically involved in many of the pathways responsible for maintaining bile acid, glucose, and lipid homeostasis. Alterations to these pathways can lead to dysregulation of energy balance and increased inflammation and fibrosis. Repeated insults over time may be the key to development of steatohepatitis. For this reason, current drug therapies target aspects of these pathways to try to reduce and halt inflammation and fibrosis. This review will focus on the role of bile acids in these various pathways and how changes in these pathways may result in steatohepatitis. While there is no approved pharmaceutical treatment for either hepatic steatosis or steatohepatitis, this review will also touch upon the multitude of potential therapies.
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Affiliation(s)
- Monica D Chow
- Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Yi-Horng Lee
- Division of Pediatric Surgery, Department of Surgery, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Grace L Guo
- Department of Pharmacy and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ, USA.
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Park J, Al-Hilal TA, Jeong JH, Choi JU, Byun Y. Design, Synthesis, and Therapeutic Evaluation of Poly(acrylic acid)-tetraDOCA Conjugate as a Bile Acid Transporter Inhibitor. Bioconjug Chem 2015; 26:1597-605. [PMID: 26086474 DOI: 10.1021/acs.bioconjchem.5b00230] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Regulation of cholesterol and bile acid homeostasis has been attracting attention as a pharmaceutical target for the treatment of diseases, such as hypercholesterolaemia and type 2 diabetes. In recent years, small bile acid analogues have been developed for the purpose of apical sodium-dependent bile acid transporter (ASBT) inhibition. Here, we designed a novel hydrophilic ASBT inhibitor using oligomeric bile acid with a high affinity with ASBT. Polyacrylic acid-tetraDOCA conjugates (PATD) have the ability to bind to ASBT in order to induce hypocholesterolemic effects. Both the viability and the functionality of PATD were evaluated in vitro, showing that PATDs were effective in inhibiting the increases of cholesterol in the blood and oil in the liver induced by high fat diet (HFD). The results indicated that the newly developed biomaterials with oligomeric bile acids and a hydrophilic polymer are potent therapeutic agents for hyperlipidemia.
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Affiliation(s)
| | - Taslim A Al-Hilal
- ‡Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology, Seoul 136-791, South Korea
| | - Jee-Heon Jeong
- §College of Pharmacy, Yeungnam University, Gyeongsan 712-749, South Korea
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Pereira-Fantini PM, Lapthorne S, Joyce SA, Dellios NL, Wilson G, Fouhy F, Thomas SL, Scurr M, Hill C, Gahan CGM, Cotter PD, Fuller PJ, Hardikar W, Bines JE. Altered FXR signalling is associated with bile acid dysmetabolism in short bowel syndrome-associated liver disease. J Hepatol 2014; 61:1115-25. [PMID: 24999016 DOI: 10.1016/j.jhep.2014.06.025] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Revised: 05/27/2014] [Accepted: 06/22/2014] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS Despite the mortality associated with liver disease observed in patients with short bowel syndrome (SBS), mechanisms underlying the development of SBS-associated liver disease (SBS-ALD) are poorly understood. This study examines the impact of bacterially-mediated bile acid (BA) dysmetabolism on farnesoid X receptor (FXR) signalling pathways and clinical outcome in a piglet model of SBS-ALD. METHODS 4-week old piglets underwent 75% small bowel resection (SBR) or sham operation. Liver histology and hepatic inflammatory gene expression were examined. Abundance of BA biotransforming bacteria was determined and metabolomic studies detailed the alterations in BA composition of stool, portal serum and bile samples. Gene expression of intestinal and hepatic FXR target genes and small heterodimer partner (SHP) transrepression targets were assessed. RESULTS Histological evidence of SBS-ALD included liver bile duct proliferation, hepatocyte ballooning and fibrosis. Inflammatory gene expression was increased. Microbiota changes included a 10-fold decrease in Clostridium and a two-fold decrease in Bacteroides in SBS-ALD piglets. BA composition was altered and reflected a primary BA dominant composition. Intestinal and hepatic regulation of BA synthesis was characterised by a blunted intestinal FXR activation response and a failure of SHP to repress key hepatic targets. CONCLUSIONS We propose a pathological scenario in which microbial dysbiosis following SBR results in significant BA dysmetabolism and consequent outcomes including steatorrhoea, persistent diarrhoea and liver damage. Furthermore alterations in BA composition may have contributed to the observed disturbance in FXR-mediated signalling pathways. These findings provide an insight into the complex mechanisms mediating the development of liver disease in patients with SBS.
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Affiliation(s)
- Prue M Pereira-Fantini
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia.
| | - Susan Lapthorne
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | | | - Nicole L Dellios
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | - Guineva Wilson
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia; Department of Surgery, Monash Medical Centre, Clayton, Victoria, Australia
| | - Fiona Fouhy
- School of Microbiology, University College Cork, Cork, Ireland; Teagasc Food Research Centre, Moorepark, Fermoy, County Cork, Ireland
| | - Sarah L Thomas
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | - Michelle Scurr
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | - Colin Hill
- Alimentary Pharmabiotic Centre, Cork, Ireland
| | | | - Paul D Cotter
- Alimentary Pharmabiotic Centre, Cork, Ireland; Teagasc Food Research Centre, Moorepark, Fermoy, County Cork, Ireland
| | - Peter J Fuller
- Prince Henry's Institute for Medical Research, Clayton, Victoria, Australia
| | - Winita Hardikar
- Department of Gastroenterology and Clinical Nutrition, Royal Children's Hospital, Parkville, Victoria, Australia; Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia; Gastro and Food Allergy Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia
| | - Julie E Bines
- Intestinal Failure and Clinical Nutrition Research Group, Murdoch Childrens Research Institute, Parkville, Victoria, Australia; Department of Gastroenterology and Clinical Nutrition, Royal Children's Hospital, Parkville, Victoria, Australia; Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
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Burke KT, Horn PS, Tso P, Heubi JE, Woollett LA. Hepatic bile acid metabolism in the neonatal hamster: expansion of the bile acid pool parallels increased Cyp7a1 expression levels. Am J Physiol Gastrointest Liver Physiol 2009; 297:G144-51. [PMID: 19389801 PMCID: PMC2711759 DOI: 10.1152/ajpgi.90515.2008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intraluminal concentrations of bile acids are low in newborn infants and increase rapidly after birth, at least partly owing to increased bile acid synthesis rates. The expansion of the bile acid pool is critical since bile acids are required to stimulate bile flow and absorb lipids, a major component of newborn diets. The purpose of the present studies was to determine the mechanism responsible for the increase in bile acid synthesis rates and the subsequent enlargement of bile acid pool sizes (BAPS) during the neonatal period, and how changes in circulating hormone levels might affect BAPS. In the hamster, pool size was low just after birth and increased modestly until 10.5 days postpartum (dpp). BAPS increased more significantly ( approximately 3-fold) between 10.5 and 15.5 dpp. An increase in mRNA and protein levels of cholesterol 7alpha-hydroxylase (Cyp7a1), the rate-limiting step in classical bile acid synthesis, immediately preceded an increase in BAPS. In contrast, levels of oxysterol 7alpha-hydroxylase (Cyp7b1), a key enzyme in bile acid synthesis by the alternative pathway, were relatively elevated by 1.5 dpp. farnesyl X receptor (FXR) and short heterodimeric partner (SHP) mRNA levels remained relatively constant at a time when Cyp7a1 levels increased. Finally, although simultaneous increases in circulating cortisol and Cyp7a1 levels occurred, precocious expression of Cyp7a1 could not be induced in neonatal hamsters with dexamethasone. Thus the significant increase in Cyp7a1 levels in neonatal hamsters is due to mechanisms independent of the FXR and SHP pathway and cortisol.
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Affiliation(s)
- Katie T. Burke
- Departments of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati Medical School, and Mathematical Sciences, University of Cincinnati; and Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology and Nutrition, General Clinical Research Center, Children's Hospital Medical Center, Cincinnati, Ohio
| | - Paul S. Horn
- Departments of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati Medical School, and Mathematical Sciences, University of Cincinnati; and Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology and Nutrition, General Clinical Research Center, Children's Hospital Medical Center, Cincinnati, Ohio
| | - Patrick Tso
- Departments of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati Medical School, and Mathematical Sciences, University of Cincinnati; and Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology and Nutrition, General Clinical Research Center, Children's Hospital Medical Center, Cincinnati, Ohio
| | - James E. Heubi
- Departments of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati Medical School, and Mathematical Sciences, University of Cincinnati; and Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology and Nutrition, General Clinical Research Center, Children's Hospital Medical Center, Cincinnati, Ohio
| | - Laura A. Woollett
- Departments of Pathology and Laboratory Medicine, Genome Research Institute, University of Cincinnati Medical School, and Mathematical Sciences, University of Cincinnati; and Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology and Nutrition, General Clinical Research Center, Children's Hospital Medical Center, Cincinnati, Ohio
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Mitro N, Godio C, De Fabiani E, Scotti E, Galmozzi A, Gilardi F, Caruso D, Vigil Chacon AB, Crestani M. Insights in the regulation of cholesterol 7alpha-hydroxylase gene reveal a target for modulating bile acid synthesis. Hepatology 2007; 46:885-97. [PMID: 17654698 DOI: 10.1002/hep.21819] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED The transcription of the gene (CYP7A1) encoding cholesterol 7alpha-hydroxylase, a key enzyme in cholesterol homeostasis, is repressed by bile acids via multiple mechanisms involving members of the nuclear receptor superfamily. Here, we describe a regulatory mechanism that can be exploited for modulating bile acid synthesis. By dissecting the mechanisms of CYP7A1 transcription, we found that bile acids stimulate the sequential recruitment of the histone deacetylases (HDACs) 7, 3, and 1, and of the corepressor SMRTalpha (silencing mediator of retinoid and thyroid receptors-alpha) and the nuclear corepressor. Bile acids, but not the farnesoid X receptor-selective agonist GW4064, increase the nuclear concentration of HDAC7, which promotes the assembly of a repressive complex that ultimately represses CYP7A1 transcription. Interestingly, despite its high basal expression level, small heterodimer partner (SHP) is associated with the CYP7A1 promoter only at a later stage of bile acid repression. Gene silencing with small interfering RNA confirms that HDAC7 is the key factor required for the repression of CYP7A1 transcription, whereas knockdown of SHP does not prevent the down-regulation of CYP7A1. Administration of the HDAC inhibitors valproic acid or trichostatin A to genetically hypercholesterolemic mice increases Cyp7a1 messenger RNA and bile acid synthesis and consequently markedly reduces total plasma and low-density lipoprotein cholesterol. CONCLUSION By using a combination of molecular, cellular, and animal models, our study highlights the importance of HDACs in the feedback regulation of CYP7A1 transcription and identifies these enzymes as potential targets to modulate bile acid synthesis and for the treatment of hypercholesterolemia.
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Affiliation(s)
- Nico Mitro
- Laboratorio Giovanni Galli di Biochimica e Biologia Molecolare dei Lipidi e di Spettrometria di Massa, Dipartimento di Scienze Farmacologiche, Facoltà di Farmacia, Università degli Studi di Milano, Milan, Italy
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10
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Hashimoto N, Ito Y, Han KH, Shimada KI, Sekikawa M, Topping DL, Bird AR, Noda T, Chiji H, Fukushima M. Potato pulps lowered the serum cholesterol and triglyceride levels in rats. J Nutr Sci Vitaminol (Tokyo) 2007; 52:445-50. [PMID: 17330508 DOI: 10.3177/jnsv.52.445] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In our previous study, we demonstrated that retrograded starch, a kind of resistant starch, of beans reduced serum lipid levels in rats. In this study, we examined whether retrograded starch in potato pulps could reduce serum lipid concentrations. Rats were given diets containing 15 g of retrograded starch in potato pulps from the Benimaru potato (BM) or Hokkaikogane potato (HK) in a 100 g diet for 4 wk. At the 4th week, the total cholesterol level in the serum in the BM group and serum triglyceride (TG) level in the HK group were significantly lower than those in the control group. In the BM group, the contents of fecal bile acids were significantly higher than those in the control group. On the other hand, in the HK group, the hepatic mRNA level of fatty acid synthase (FAS) was significantly lower than that in the control group. The FAS mRNA level correlated with the mRNA level of sterol regulatory element-binding protein-1c (SREBP-1c), a regulator of expression of FAS, positively. These results suggested that BM pulp promoted the excretion of bile acids, which resulted in a low concentration of serum cholesterol. On the other hand, HK pulp inhibited the synthesis of fatty acids at the mRNA levels of FAS and SREBP-1c, which might lead to a reduction of the serum TG level.
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Affiliation(s)
- Naoto Hashimoto
- Department of Animal Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
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11
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Alrefai WA, Gill RK. Bile acid transporters: structure, function, regulation and pathophysiological implications. Pharm Res 2007; 24:1803-23. [PMID: 17404808 DOI: 10.1007/s11095-007-9289-1] [Citation(s) in RCA: 323] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 02/28/2007] [Indexed: 12/11/2022]
Abstract
Specific transporters expressed in the liver and the intestine, play a critical role in driving the enterohepatic circulation of bile acids. By preserving a circulating pool of bile acids, an important factor influencing bile flow, these transporters are involved in maintaining bile acid and cholesterol homeostasis. Enterohepatic circulation of bile acids is fundamentally composed of two major processes: secretion from the liver and absorption from the intestine. In the hepatocytes, the vectorial transport of bile acids from blood to bile is ensured by Na+ taurocholate co-transporting peptide (NTCP) and organic anion transport polypeptides (OATPs). After binding to a cytosolic bile acid binding protein, bile acids are secreted into the canaliculus via ATP-dependent bile salt excretory pump (BSEP) and multi drug resistant proteins (MRPs). Bile acids are then delivered to the intestinal lumen through bile ducts where they emulsify dietary lipids and cholesterol to facilitate their absorption. Intestinal epithelial cells reabsorb the majority of the secreted bile acids through the apical sodium dependent bile acid transporter (ASBT) and sodium independent organic anion transporting peptide (OATPs). Cytosolic ileal bile acid binding protein (IBABP) mediates the transcellular movement of bile acids to the basolateral membrane across which they exit the cells via organic solute transporters (OST). An essential role of bile acid transporters is evident from the pathology associated with their genetic disruption or dysregulation of their function. Malfunctioning of hepatic and intestinal bile acid transporters is implicated in the pathophysiology of cholestatic liver disease and the depletion of circulating pool of bile acids, respectively. Extensive efforts have been recently made to enhance our understanding of the structure, function and regulation of the bile acid transporters and exploring new potential therapeutics to treat bile acid or cholesterol related diseases. This review will highlight current knowledge about structure, function and molecular characterization of bile acid transporters and discuss the implications of their defects in various hepatic and intestinal disorders.
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Affiliation(s)
- Waddah A Alrefai
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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12
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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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13
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Alrefai WA, Sarwar Z, Tyagi S, Saksena S, Dudeja PK, Gill RK. Cholesterol modulates human intestinal sodium-dependent bile acid transporter. Am J Physiol Gastrointest Liver Physiol 2005; 288:G978-85. [PMID: 15604201 DOI: 10.1152/ajpgi.00379.2004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Bile acids are efficiently absorbed from the intestinal lumen via the ileal apical sodium-dependent bile acid transporter (ASBT). ASBT function is essential for maintenance of cholesterol homeostasis in the body. The molecular mechanisms of the direct effect of cholesterol on human ASBT function and expression are not entirely understood. The present studies were undertaken to establish a suitable in vitro experimental model to study human ASBT function and its regulation by cholesterol. Luminal membrane bile acid transport was evaluated by the measurement of sodium-dependent 3H-labeled taurocholic acid (3H-TC) uptake in human intestinal Caco-2 cell monolayers. The relative abundance of human ASBT (hASBT) mRNA was determined by real-time PCR. Transient transfection and luciferase assay techniques were employed to assess hASBT promoter activity. Caco-2 cell line was found to represent a suitable model to study hASBT function and regulation. 25-Hydroxycholesterol (25-HCH; 2.5 microg/ml for 24 h) significantly inhibited Na(+)-dependent 3H-TC uptake in Caco-2 cells. This inhibition was associated with a 50% decrease in the V(max) of the transporter with no significant changes in the apparent K(m). The inhibition in hASBT activity was associated with reduction in both the level of hASBT mRNA and its promoter activity. Our data show the inhibition of hASBT function and expression by 25-HCH in Caco-2 cells. These data provide novel evidence for the direct regulation of human ASBT function by cholesterol and suggest that this phenomenon may play a central role in cholesterol homeostasis.
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Affiliation(s)
- Waddah A Alrefai
- Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veteran Affairs Medical Center, Medical Research Service (600/151 820 South Damen Ave., Chicago, Illinois 60612, USA.
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14
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Arrese M, Ananthanarayanan M. The bile salt export pump: molecular properties, function and regulation. Pflugers Arch 2004; 449:123-31. [PMID: 15578267 DOI: 10.1007/s00424-004-1311-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Accepted: 06/16/2004] [Indexed: 12/31/2022]
Abstract
Secretion of bile salts from the hepatocyte into bile is the major driving force for the generation of bile flow. Identification of the bile salt export pump (BSEP, ABCB11) as the main adenosine-triphosphate-dependent bile salt transporter in mammalian liver has led to a greater understanding of the biliary bile salt secretory process and its regulation. The biology and pathobiology of BSEP have been the subject of many recent studies. Thus, it has been recognized that while mutations in the gene encoding BSEP are responsible for a subgroup of progressive familial cholestasis (progressive familial intrahepatic cholestasis subtype 2), a pediatric cholestatic disorder that may progress to cirrhosis, defective expression or function of BSEP may underlie some forms of drug-induced cholestasis. The present review summarizes recent data on the molecular properties and regulation of BSEP, as well as the clinical implications of absent or defective function of this hepatic efflux pump.
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Affiliation(s)
- Marco Arrese
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 367, 6510260 Santiago, Chile.
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Crestani M, Mitro N, De Fabiani E. Lipid-activated nuclear receptors: from gene transcription to the control of cellular metabolism. EUR J LIPID SCI TECH 2004. [DOI: 10.1002/ejlt.200300936] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Li H, Xu G, Shang Q, Pan L, Shefer S, Batta AK, Bollineni J, Tint GS, Keller BT, Salen G. Inhibition of ileal bile acid transport lowers plasma cholesterol levels by inactivating hepatic farnesoid X receptor and stimulating cholesterol 7 alpha-hydroxylase. Metabolism 2004; 53:927-32. [PMID: 15254889 DOI: 10.1016/j.metabol.2004.01.017] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We investigated the effect of SC-435, a competitive inhibitor of ileal apical sodium-dependent bile acid cotransporter (ASBT) on ileal bile acid absorption and the hepatic nuclear receptor FXR (farnesoid X receptor), which regulates cholesterol 7 alpha-hydroxylase (CYP7A1) activity and mRNA levels. Eighteen New Zealand White (NZW) rabbits were divided into 2 groups: controls (n = 10) and fed SC-435 125 mg/kg/d for 1 week (n = 8). In rabbits treated with SC-435, fecal bile acid outputs increased by more than 8 times, reflecting substantial bile acid malabsorption. Plasma cholesterol levels decreased 26%, while bile acid pool sizes and biliary bile acid outputs did not change after treatment. CYP7A1 activity increased 64% and mRNA rose by 4 times after treatment. The expression of FXR target genes in the liver, short heterodimer partner (SHP) and bile salt export pump (BSEP), decreased 11.6 and 2.6 times, respectively, after treatment, which indicates inactivation of hepatic FXR. However, the mRNA levels of ileal bile acid binding protein (IBABP) did not change significantly, while ileal ASBT mRNA expression increased by 2.4 times after treatment. Rabbits treated with SC-435 developed ileal bile acid malabsorption, which decreased the return of bile acids (FXR ligands) to the liver to inactivate hepatic FXR, which upregulated CYP7A1 and lowered plasma cholesterol levels. Although fecal bile acid malabsorption was substantial, increased bile acid production from hepatic cholesterol kept biliary bile acid outputs intact. Thus, a new balance was reached in the liver, where increased bile acid synthesis compensated for diminished ileal bile acid absorption to maintain the circulating enterohepatic bile acid pool.
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Affiliation(s)
- Hai Li
- Department of Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
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17
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Bhat BG, Rapp SR, Beaudry JA, Napawan N, Butteiger DN, Hall KA, Null CL, Luo Y, Keller BT. Inhibition of ileal bile acid transport and reduced atherosclerosis in apoE-/- mice by SC-435. J Lipid Res 2003; 44:1614-21. [PMID: 12810816 DOI: 10.1194/jlr.m200469-jlr200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Blocking intestinal bile acid absorption by inhibiting the apical sodium codependent bile acid transporter (ASBT) is a target for increasing hepatic bile acid synthesis and reducing plasma LDL cholesterol. SC-435 was identified as a potent inhibitor of ASBT (IC50 = 1.5 nM) in cells transfected with the human ASBT gene. Dietary administration of 3 mg/kg to 30 mg/kg SC-435 to apolipoprotein E-/- (apoE-/-) mice increased fecal bile acid excretion by >2.5-fold. In vivo inhibition of ASBT also resulted in significant increases of hepatic mRNA levels for cholesterol 7alpha-hydroxylase and HMG-CoA reductase. Administration of 10 mg/kg SC-435 for 12 weeks to apoE-/- mice lowered serum total cholesterol by 35% and reduced aortic root lesion area by 65%. Treatment of apoE-/- mice also resulted in decreased expression of ileal bile acid binding protein and hepatic nuclear hormone receptor small heterodimer partner, direct target genes of the farnesoid X receptor (FXR), suggesting a possible role of FXR in SC-435 modulation of cholesterol homeostasis. In dogs, SC-435 treatment reduced serum total cholesterol levels by </=12% and, in combination with atorvastatin treatment, caused an additional reduction of 25%. These results suggest that specific inhibition of ASBT is a novel therapeutic approach for treatment of hypercholesterolemia resulting in a decreased risk for atherosclerosis.
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Affiliation(s)
- B Ganesh Bhat
- Cardiovascular and Metabolic Diseases Discovery Research, Pfizer Inc., St. Louis, MO 63167, USA.
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Xu G, Pan LX, Li H, Forman BM, Erickson SK, Shefer S, Bollineni J, Batta AK, Christie J, Wang TH, Michel J, Yang S, Tsai R, Lai L, Shimada K, Tint GS, Salen G. Regulation of the farnesoid X receptor (FXR) by bile acid flux in rabbits. J Biol Chem 2002; 277:50491-6. [PMID: 12401785 DOI: 10.1074/jbc.m209176200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the roles of hydrophobic deoxycholic acid (DCA) and hydrophilic ursocholic acid (UCA) in the regulation of the orphan nuclear farnesoid X receptor (FXR) in vivo. Rabbits with bile fistula drainage (removal of the endogenous bile acid pool), rabbits with bile fistula drainage and replacement with either DCA or UCA, and intact rabbits fed 0.5% cholic acid (CA) (enlarged endogenous bile acid pool) were studied. After bile fistula drainage, cholesterol 7alpha-hydroxylase (CYP7A1) mRNA and activity levels increased, FXR-mediated transcription was decreased, and FXR mRNA and nuclear protein levels declined. Replacing the enterohepatic bile acid pool with DCA restored FXR mRNA and nuclear protein levels and activated FXR-mediated transcription as evidenced by the increased expression of its target genes, SHP and BSEP, and decreased CYP7A1 mRNA level and activity. Replacing the bile acid pool with UCA also restored FXR mRNA and nuclear protein levels but did not activate FXR-mediated transcription, because the SHP mRNA level and CYP7A1 mRNA level and activity were unchanged. Feeding CA to intact rabbits expanded the bile acid pool enriched with the FXR high affinity ligand, DCA. FXR-mediated transcription became activated as shown by increased SHP and BSEP mRNA levels and decreased CYP7A1 mRNA level and activity but did not change FXR mRNA or nuclear protein levels. Thus, both hydrophobic and hydrophilic bile acids are effective in maintaining FXR mRNA and nuclear protein levels. However, the activating ligand (DCA) in the enterohepatic flux is necessary for FXR-mediated transcriptional regulation, which leads to down-regulation of CYP7A1.
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Affiliation(s)
- Guorong Xu
- Medical Service, Veterans Affairs Medical Center, East Orange, New Jersey 07018, USA.
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Gupta S, Pandak WM, Hylemon PB. LXR alpha is the dominant regulator of CYP7A1 transcription. Biochem Biophys Res Commun 2002; 293:338-43. [PMID: 12054605 DOI: 10.1016/s0006-291x(02)00229-2] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cholesterol 7 alpha-hydroxylase (CYP7A1) catalyzes the rate-limiting step in the classic pathway of bile acid biosynthesis. Dietary cholesterol stimulates CYP7A1 transcription via activation of oxysterol receptor, LXR alpha, whereas bile acids repress transcription through FXR-mediated induction of SHP protein. The aim of this study was to determine the quantitative role that LXR- and FXR-regulated pathways play in regulating CYP7A1 and SHP in both rat and hamster models. In rats fed a 2% cholesterol diet, both SHP and CYP7A1 mRNA levels were elevated. The inability to induce CYP7A1 mRNA levels by cholesterol feeding in hamsters led to a decline in SHP mRNA levels. Elimination of hepatic bile acid flux by cholestyramine or bile fistula resulted in a marked repression of rat SHP mRNA levels. These results suggest that under conditions of both SHP and LXR alpha activation, stimulatory effect of LXR alpha overrides the inhibitory effect of FXR and results in an induction of rat CYP7A1 mRNA levels.
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Affiliation(s)
- Seema Gupta
- Department of Microbiology and Immunology, Virginia Commonwealth University, MCV Campus, Richmond, VA 23298, USA
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