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A Transient Inflammatory Response Induced by Lipopolysaccharide Infusion Lowers Markers of Endogenous Cholesterol and Bile Acid Synthesis in Healthy Normocholesterolemic Young Men. Biomedicines 2023; 11:biomedicines11010126. [PMID: 36672634 PMCID: PMC9855383 DOI: 10.3390/biomedicines11010126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 12/27/2022] [Accepted: 01/01/2023] [Indexed: 01/06/2023] Open
Abstract
Inflammation is associated with changes in plasma lipids, lipoproteins, and cholesterol efflux capacity (CEC). It is unknown if the changes in lipids and lipoproteins during inflammation are related to changes in cholesterol absorption, synthesis, and bile acid synthesis. We, therefore, examined the effects of acute lipopolysaccharide (LPS)-induced transient systemic inflammation on lipids, lipoproteins, CEC, and markers of cholesterol metabolism. We also evaluated whether markers for cholesterol metabolism at baseline predict the intensity of the inflammatory response. Eight healthy young subjects received LPS infusion, and blood was sampled for the following 24 h. In addition to lipids, lipoproteins, and CEC, we also measured markers for cholesterol absorption and synthesis, bile acid synthesis, and inflammation. Compared with baseline, plasma total cholesterol, low-density lipoprotein cholesterol, and CEC decreased, while triglycerides increased in the 24 h following LPS infusion. TC-standardized levels of cholesterol synthesis markers (lathosterol, lanosterol, and desmosterol) and a bile acid synthesis marker (7α-OH-cholesterol) also decreased, with no changes in cholesterol absorption markers (campesterol, sitosterol, and cholestanol). Baseline TC-standardized levels of desmosterol and 7α-OH-cholesterol were positively correlated with concentrations of various inflammatory markers. Changes in TC-standardized desmosterol and 7α-OH-cholesterol were negatively correlated with concentrations of inflammatory markers. LPS infusion reduced endogenous cholesterol synthesis and bile acid synthesis in healthy young men.
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Simbrunner B, Mandorfer M, Trauner M, Reiberger T. Gut-liver axis signaling in portal hypertension. World J Gastroenterol 2019; 25:5897-5917. [PMID: 31660028 PMCID: PMC6815800 DOI: 10.3748/wjg.v25.i39.5897] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/15/2019] [Accepted: 09/28/2019] [Indexed: 02/06/2023] Open
Abstract
Portal hypertension (PHT) in advanced chronic liver disease (ACLD) results from increased intrahepatic resistance caused by pathologic changes of liver tissue composition (structural component) and intrahepatic vasoconstriction (functional component). PHT is an important driver of hepatic decompensation such as development of ascites or variceal bleeding. Dysbiosis and an impaired intestinal barrier in ACLD facilitate translocation of bacteria and pathogen-associated molecular patterns (PAMPs) that promote disease progression via immune system activation with subsequent induction of proinflammatory and profibrogenic pathways. Congestive portal venous blood flow represents a critical pathophysiological mechanism linking PHT to increased intestinal permeability: The intestinal barrier function is affected by impaired microcirculation, neoangiogenesis, and abnormal vascular and mucosal permeability. The close bidirectional relationship between the gut and the liver has been termed “gut-liver axis”. Treatment strategies targeting the gut-liver axis by modulation of microbiota composition and function, intestinal barrier integrity, as well as amelioration of liver fibrosis and PHT are supposed to exert beneficial effects. The activation of the farnesoid X receptor in the liver and the gut was associated with beneficial effects in animal experiments, however, further studies regarding efficacy and safety of pharmacological FXR modulation in patients with ACLD are needed. In this review, we summarize the clinical impact of PHT on the course of liver disease, discuss the underlying pathophysiological link of PHT to gut-liver axis signaling, and provide insight into molecular mechanisms that may represent novel therapeutic targets.
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Affiliation(s)
- Benedikt Simbrunner
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1180, Austria
- Vienna Hepatic Hemodynamic Lab, Medical University of Vienna, Vienna 1180, Austria
| | - Mattias Mandorfer
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1180, Austria
- Vienna Hepatic Hemodynamic Lab, Medical University of Vienna, Vienna 1180, Austria
| | - Michael Trauner
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1180, Austria
| | - Thomas Reiberger
- Department of Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna, Vienna 1180, Austria
- Vienna Hepatic Hemodynamic Lab, Medical University of Vienna, Vienna 1180, Austria
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Cao B, Sun RB, Yan G, Yang GY, Aa JY, Li J. Berberine reverses LPS-induced repression of CYP7A1 through an anti-inflammatory effect. CHINESE HERBAL MEDICINES 2019. [DOI: 10.1016/j.chmed.2019.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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Zöhrer E, Resch B, Scharnagl H, Schlagenhauf A, Fauler G, Stojakovic T, Hofer N, Lang U, Jahnel J. Serum bile acids in term and preterm neonates: A case-control study determining reference values and the influence of early-onset sepsis. Medicine (Baltimore) 2016; 95:e5219. [PMID: 27858868 PMCID: PMC5591116 DOI: 10.1097/md.0000000000005219] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Serum bile acids (BA) reference values are lacking for neonates. Therefore, this study aimed to determine serum BA reference values in term and preterm neonates. Furthermore, as serum BA concentrations are well-known to rise in septic adults, BA values were determined in early-onset neonatal sepsis (EOS), a common and serious disease in neonates.Using high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS), we profiled serum BA in 236 infants, including healthy term neonates (n = 84), premature infants (n = 101), and both term infants (n = 35) and preterm infants (n = 16) with EOS. We examined the impact of prematurity and EOS on BA concentrations.The median reference values of serum BA were 8.0 μmol/L, interquartile range (IQR): 4.6 to 12.9, in healthy term neonates and 10.1 μmol/L, IQR: 5.7 to 15.7, in preterm neonates. Neonates with EOS had significantly lower median BA values, term (4.7 μmol/L, IQR: 2.7-7.6; P < 0.01) as well as preterm (6.4 μmol/L, IQR: 3.5-8.4; P < 0.01). Furthermore, primary and conjugated BA were most abundant in all groups. Taurine-conjugated BA were predominant in all neonates; glycine-conjugated BA were significantly lower in term neonates with EOS than in controls (P < 0.05). Multivariate regression analysis results obtained for BA and inflammatory parameters revealed that BA are an independent factor associated with EOS.This is the first study to determine standard value ranges of serum BA in neonates using HPLC-HRMS. In contrast to adults with sepsis, neonates suffering from EOS exhibit significantly lower BA values than do controls of the same gestational age. These data suggest BA as a supplementary parameter within a panel of biomarkers for EOS in the future.
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Affiliation(s)
- Evelyn Zöhrer
- Division of General Pediatrics, Department of Pediatrics and Adolescent Medicine, Medical University of Graz
| | - Bernhard Resch
- Division of Neonatology, Department of Pediatrics and Adolescent Medicine, Medical University of Graz
- Research Unit for Neonatal Infectious Diseases and Epidemiology, Medical University of Graz
| | - Hubert Scharnagl
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz
| | - Axel Schlagenhauf
- Division of General Pediatrics, Department of Pediatrics and Adolescent Medicine, Medical University of Graz
| | - Günter Fauler
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz
| | - Tatjana Stojakovic
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz
| | - Nora Hofer
- Research Unit for Neonatal Infectious Diseases and Epidemiology, Medical University of Graz
| | - Uwe Lang
- Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria
| | - Jörg Jahnel
- Division of General Pediatrics, Department of Pediatrics and Adolescent Medicine, Medical University of Graz
- Correspondence: Jörg Jahnel, MD, Department of Pediatrics and Adolescent Medicine, Medical University of Graz, Auenbruggerplatz 34/2, A-8036 Graz, Austria (e-mail: )
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Abstract
PURPOSE OF REVIEW Studies have shown that chronic inflammatory disorders, such as rheumatoid arthritis, systemic lupus erythematosus, and psoriasis are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism by which inflammation increases cardiovascular disease is likely multifactorial but changes in HDL structure and function that occur during inflammation could play a role. RECENT FINDINGS HDL levels decrease with inflammation and there are marked changes in HDL-associated proteins. Serum amyloid A markedly increases whereas apolipoprotein A-I, lecithin:cholesterol acyltransferase, cholesterol ester transfer protein, paraoxonase 1, and apolipoprotein M decrease. The exact mechanism by which inflammation decreases HDL levels is not defined but decreases in apolipoprotein A-I production, increases in serum amyloid A, increases in endothelial lipase and secretory phospholipase A2 activity, and decreases in lecithin:cholesterol acyltransferase activity could all contribute. The changes in HDL induced by inflammation reduce the ability of HDL to participate in reverse cholesterol transport and protect LDL from oxidation. SUMMARY During inflammation multiple changes in HDL structure occur leading to alterations in HDL function. In the short term, these changes may be beneficial resulting in an increase in cholesterol in peripheral cells to improve host defense and repair but over the long term these changes may increase the risk of atherosclerosis.
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Affiliation(s)
- Kenneth R Feingold
- Metabolism Section, Department of Veterans Affairs Medical Center, University of California San Francisco, San Francisco, California, USA
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He JJ, Ma J, Elsheikha HM, Song HQ, Huang SY, Zhu XQ. Transcriptomic analysis of mouse liver reveals a potential hepato-enteric pathogenic mechanism in acute Toxoplasma gondii infection. Parasit Vectors 2016; 9:427. [PMID: 27488578 PMCID: PMC4973073 DOI: 10.1186/s13071-016-1716-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 07/20/2016] [Indexed: 12/12/2022] Open
Abstract
Background Toxoplasma gondii is a worldwide spread pathogen which can infect all tissues of its host. The transcriptomic responses of infected brain and spleen have been reported. However, our knowledge of the global transcriptomic change in infected liver is limited. Additionally, T. gondii infection represents a highly dynamic process involving complex biological responses of the host at many levels. Herein, we describe such processes at a global level by discovering gene expression changes in mouse livers after acute infection with T. gondii ToxoDB#9 strain. Results Global transcriptomic analysis identified 2,758 differentially expressed transcripts in infected liver, of which 1,356 were significantly downregulated and 1,402 upregulated. GO and KEGG database analyses showed that host immune responses were upregulated, while the metabolic-related processes/pathways were downregulated, especially xenobiotic metabolism, fatty acid metabolism, energy metabolism, and bile biosynthesis and secretion. The metabolism of more than 800 chemical compounds including anti-Toxoplasma prescribed medicines were predicted to be modulated during acute T. gondii infection due to the downregulation of enzymes involved in xenobiotic metabolism. Conclusions To the best of our knowledge, this is the first global transcriptomic analysis of mouse liver infected by T. gondii. The present data indicate that during the early stage of liver infection, T. gondii can induce changes in liver xenobiotic metabolism, upregulating inflammatory response and downregulating hepatocellular PPAR signaling pathway, altering host bile biosynthesis and secretion pathway; these changes could enhance host intestinal dysbacteriosis and thus contribute to the pathological changes of both liver and intestine of infected mice. These findings describe the biological changes in infected liver, providing a potential mechanistic pathway that links hepatic and intestinal pathologies to T. gondii infection. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1716-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jun-Jun He
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China
| | - Jun Ma
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China.,College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan Province, 410128, People's Republic of China
| | - Hany M Elsheikha
- Faculty of Medicine and Health Sciences, School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK
| | - Hui-Qun Song
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China
| | - Si-Yang Huang
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu Province, 225009, People's Republic of China.
| | - Xing-Quan Zhu
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu Province, 225009, People's Republic of China.
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Ridlon JM, Bajaj JS. The human gut sterolbiome: bile acid-microbiome endocrine aspects and therapeutics. Acta Pharm Sin B 2015; 5:99-105. [PMID: 26579434 PMCID: PMC4629220 DOI: 10.1016/j.apsb.2015.01.006] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/05/2015] [Indexed: 01/05/2023] Open
Abstract
The human body is now viewed as a complex ecosystem that on a cellular and gene level is mainly prokaryotic. The mammalian liver synthesizes and secretes hydrophilic primary bile acids, some of which enter the colon during the enterohepatic circulation, and are converted into numerous hydrophobic metabolites which are capable of entering the portal circulation, returned to the liver, and in humans, accumulating in the biliary pool. Bile acids are hormones that regulate their own synthesis, transport, in addition to glucose and lipid homeostasis, and energy balance. The gut microbial community through their capacity to produce bile acid metabolites distinct from the liver can be thought of as an “endocrine organ” with potential to alter host physiology, perhaps to their own favor. We propose the term “sterolbiome” to describe the genetic potential of the gut microbiome to produce endocrine molecules from endogenous and exogenous steroids in the mammalian gut. The affinity of secondary bile acid metabolites to host nuclear receptors is described, the potential of secondary bile acids to promote tumors, and the potential of bile acids to serve as therapeutic agents are discussed.
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Key Words
- APC, adenomatous polyposis coli
- BA, bile acids
- BSH, bile salt hydrolases
- Bile acids
- CA, cholic acid
- CDCA, chenodeoxycholic acid
- COX-2, cyclooxygenase-2
- CRC, colorectal cancer
- CYP27A1, sterol-27-hydroxylase
- CYP7A1, cholesterol 7α-hydroxylase
- CYP8B1, sterol 12α-hydroxylase
- DCA, deoxycholic acid
- EGFR, epidermal growth factor receptor
- FAP, familial adenomatous polyposis
- FGF15/19, fibroblast growth factor 15/19
- FXR, farnesoid X receptor
- GABA, γ-aminobutyric acid
- GPCR, G-protein coupled receptors
- Gut microbiome
- HMP, Human Microbiome Project
- HSDH, hydroxysteroid dehydrogenase
- LCA, lithocholic acid
- LOX, lipooxygenase
- MetaHIT, Metagenomics of the Human Intestinal Tract
- Metabolite
- NSAIDs, non-steroidal anti-inflammatory drugs
- PKC, protein kinase C
- PSC, primary sclerosing cholangitis
- PXR, pregnane X receptor
- Sterolbiome
- Therapeutic agent
- UDCA, ursodeoxycholic acid
- VDR, vitamin D receptor
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Ridlon JM, Alves JM, Hylemon PB, Bajaj JS. Cirrhosis, bile acids and gut microbiota: unraveling a complex relationship. Gut Microbes 2013; 4:382-7. [PMID: 23851335 PMCID: PMC3839982 DOI: 10.4161/gmic.25723] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A picture is now starting to emerge regarding the liver-bile acid-microbiome axis. Increasing levels of the primary bile acid cholic acid (CA) causes a dramatic shift toward the Firmicutes, particularly Clostridium cluster XIVa and increasing production of the harmful secondary bile acid deoxycholic acid (DCA). During progression of cirrhosis, the microbiome, both through their metabolism, cell wall components (LPS) and translocation lead to inflammation. Inflammation suppresses synthesis of bile acids in the liver leading to a positive-feedback mechanism. Decrease in bile acids entering the intestines appears to favor overgrowth of pathogenic and pro-inflammatory members of the microbiome including Porphyromonadaceae and Enterobacteriaceae. Decreasing bile acid concentration in the colon in cirrhosis is also associated with decreases in Clostridium cluster XIVa, which includes bile acid 7α-dehydroxylating bacteria which produce DCA. Rifaximin treatment appears to act by suppressing DCA production, reducing endotoxemia and harmful metabolites without significantly altering microbiome structure. Taken together, the bile acid pool size and composition appear to be a major regulator of microbiome structure, which in turn appears to be an important regulator of bile acid pool size and composition. The balance between this equilibrium is critical for human health and disease.
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Affiliation(s)
- Jason M Ridlon
- Department of Microbiology and Immunology; Virginia Commonwealth University; Richmond, VA USA,McGuire VA Medical Center; Richmond, VA USA
| | - Joao Marcelo Alves
- Department of Microbiology and Immunology; Virginia Commonwealth University; Richmond, VA USA
| | - Phillip B Hylemon
- Department of Microbiology and Immunology; Virginia Commonwealth University; Richmond, VA USA,McGuire VA Medical Center; Richmond, VA USA
| | - Jasmohan S Bajaj
- McGuire VA Medical Center; Richmond, VA USA,Division of Gastroenterology, Hepatology and Nutrition; Virginia Commonwealth University; Richmond, VA USA,Correspondence to: Jasmohan S Bajaj,
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Feingold KR, Grunfeld C. The acute phase response inhibits reverse cholesterol transport. J Lipid Res 2010; 51:682-4. [PMID: 20071695 DOI: 10.1194/jlr.e005454] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- Kenneth R Feingold
- Metabolism Section, Department of Veterans Affairs Medical Center, University of California San Francisco, San Francisco, CA, USA.
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Dikopoulos N, Schmid RM, Bachem M, Buttenschoen K, Adler G, Chiang JYL, Weidenbach H. Bile synthesis in rat models of inflammatory bowel diseases. Eur J Clin Invest 2007; 37:222-30. [PMID: 17359490 DOI: 10.1111/j.1365-2362.2007.01779.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND A broad spectrum of hepatobiliary disorders are found in patients with inflammatory bowel diseases. The aim of the present work was to study interactions between gut and liver in experimental rat models of colitis and small bowel inflammation. MATERIALS AND METHODS Colitis was induced either by trinitrobenzene sulphonic acid or dextran sodium sulphate. Small-bowel inflammation was induced by indomethacin. Bile acid secretion, bile acid pool, and cholesterol 7-alpha hydroxylase were studied. Cholesterol 7-alpha hydroxylase protein expression was analysed in the microsomal liver fraction. As portal mediators released form the inflamed gut we measured lipopolysaccharide, tumour necrosis factor-alpha and interleukin-1beta in portal serum. The hepatic inflammatory response was evaluated by binding activity of nuclear factor-kappaB, activator protein-1 and alpha-2-macroglobulin. RESULTS Increased bile acid secretion, total bile acid content in gut and liver (bile acid pool size), and hepatic cholesterol 7-alpha hydroxylase protein and mRNA levels were found in the two colitis models associated with only a minor hepatic acute phase and cytokine response. In contrast, during indomethacin-induced small-bowel inflammation bile acid secretion, pool size, and cholesterol 7-alpha hydroxylase decreased in parallel to a strong hepatic cytokine and acute phase response. CONCLUSIONS Colitis without portal cytokine release and acute phase reaction shows an induction of bile acid secretion, pool size, and cholesterol 7-alpha hydroxylase. In contrast, intestinal inflammation after indomethacin treatment is associated with an acute phase response and a repression of bile acid synthesis.
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Affiliation(s)
- N Dikopoulos
- Department of Internal Medicine I, University of Ulm, Ulm, Germany.
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Wang M, Tan Y, Costa RH, Holterman AXL. In vivo regulation of murine CYP7A1 by HNF-6: a novel mechanism for diminished CYP7A1 expression in biliary obstruction. Hepatology 2004; 40:600-8. [PMID: 15349898 DOI: 10.1002/hep.20349] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Disruption of the enterohepatic bile acid circulation during biliary tract obstruction leads to profound perturbation of the cholesterol and bile acid metabolic pathways. Several families of nuclear receptor proteins have been shown to modulate this critical process by regulating hepatic cholesterol catabolism and bile acid synthesis through the transcriptional control of cholesterol 7-alpha hydroxylase (CYP7A1). Hepatocyte nuclear factor (HNF) 6 (also known as OC-1) is a member of the ONECUT family of transcription factors that activate numerous hepatic target genes essential to liver function. We have previously shown that hepatic expression of mouse HNF-6 messenger RNA (mRNA) and protein significantly decrease following bile duct ligation. Because CYP7A1 contains potential HNF-6 binding sites in its promoter region, we tested the hypothesis that HNF-6 transcriptionally regulates CYP7A1. Following bile duct ligation, we demonstrated that diminished HNF-6 mRNA levels correlate with a reduction in CYP7A1 mRNA expression. Increasing hepatic levels of HNF-6 either by infection with recombinant adenovirus vector expressing HNF-6 cDNA by growth hormone treatment leads to an induction of CYP7A1 mRNA. To directly evaluate if HNF-6 is a transcriptional activator for CYP7A1, we used deletional and mutational analyses of CYP7A1 promoter sequences and defined sequences -206/-194 to be critical for CYP7A1 transcriptional stimulation by HNF-6 in cotransfection assays. In conclusion, the HNF-6 protein is a component of the complex network of hepatic transcription factors that regulates the expression of hepatic genes essential for bile acid homeostasis and cholesterol/lipid metabolism in normal and pathological conditions.
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Affiliation(s)
- Minhua Wang
- Department of Surgery, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, USA
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