Bile acid detoxifying enzymes limit susceptibility to liver fibrosis in female SHRSP5/Dmcr rats fed with a high-fat-cholesterol diet

During middle age, women are less susceptible to nonalcoholic steatohepatitis (NASH) than men. Thus, we investigated the underlying molecular mechanisms behind these sexual differences using an established rat model of NASH. Mature female and male stroke-prone spontaneously hypertensive 5/Dmcr rats were fed control or high-fat-cholesterol (HFC) diets for 2, 8, and 14 weeks. Although HFC-induced hepatic fibrosis was markedly less severe in females than in males, only minor gender differences were observed in expression levels of cytochrome P450 enzymes (CYP)7A1, CYP8B1 CYP27A1, and CYP7B1, and multidrug resistance-associated protein 3, and bile salt export pump, which are involved in fibrosis-related bile acid (BA) kinetics. However, the BA detoxification-related enzymes UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) 2A1, and the nuclear receptors constitutive androstene receptor (CAR) and pregnane X receptor (PXR), were strongly suppressed in HFC fed males, and were only slightly changed in HFC-diet fed females. Expression levels of the farnesoid X receptor and its small heterodimer partner were similarly regulated in a gender-dependent fashion following HFC feeding. Hence, the pronounced female resistance to HFC-induced liver damage likely reflects sustained expression of the nuclear receptors CAR and PXR and the BA detoxification enzymes UGT and SULT.

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Multiple mechanisms of ontogenic regulation of nuclear receptors during rat liver development

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00351.2004 ◽

2005 ◽

Vol 288 (2) ◽

pp. G251-G260 ◽

Cited By ~ 28

Author(s):

N. Balasubramaniyan ◽

Mohammad Shahid ◽

Frederick J. Suchy ◽

M. Ananthanarayanan

Keyword(s):

Bile Acid ◽

Nuclear Receptors ◽

Rat Liver ◽

Functional Activity ◽

Pregnane X Receptor ◽

Farnesoid X Receptor ◽

Liver Development ◽

Mrna Levels ◽

Bile Formation ◽

Protein Levels

Nuclear receptors (NRs) play pivotal roles in the regulation of genes contributing to hepatobiliary cholesterol and bile acid homeostasis. We have previously shown that transporters involved in bile formation are developmentally regulated and are poorly developed during the fetal stage, but their expression reached gradual maturity during the postnatal period. To define the molecular mechanisms underlying this regulation and the role that class II NRs and associated members [liver receptor homolog-1 (LRH-1) and short heterodimer partner (SHP)] play, we have analyzed the ontogeny of NR expression during liver development. Real-time PCR analysis of hepatic NR expression from fetal day 17 through adult revealed that steady-state mRNA levels for all NRs were very low during the embryonic period. However, mRNA levels peaked close to that of adult rats (>6 wk-old rats) by 4 wk of age for farnesoid X receptor (FXR), pregnane X receptor (PXR), liver X receptor-α (LXRα), peroxisome proliferator-activated receptor-α (PPARα), retinoid acid receptor-α (RARα), LRH-1, and SHP, whereas RXRα mRNA lagged behind. FXR, PXR, LXRα, RARα, and PPARα functional activity in liver nuclear extracts assayed by gel EMSA demonstrated that the activity attained adult levels by 4 wk of age, exhibiting a strict correlation with mRNA levels. Surprisingly, PPARα activity was delayed as seen by EMSA assay. Protein levels for NRs also corresponded to the mRNA and functional activity except for RXRα. RXRα protein levels were higher than message levels, suggesting increased protein stability. We conclude that expression of NRs during rat liver development is primarily regulated by transcriptional mechanisms, which in turn, control the regulation of bile acid and cholesterol metabolic pathways.

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Role of nuclear receptors and hepatocyte-enriched transcription factors for Ntcp repression in biliary obstruction in mouse liver

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00319.2004 ◽

2005 ◽

Vol 289 (5) ◽

pp. G798-G805 ◽

Cited By ~ 46

Author(s):

Gernot Zollner ◽

Martin Wagner ◽

Peter Fickert ◽

Andreas Geier ◽

Andrea Fuchsbichler ◽

...

Keyword(s):

Transcription Factors ◽

Bile Acid ◽

Dna Binding ◽

Nuclear Receptors ◽

Farnesoid X Receptor ◽

Acid Uptake ◽

Mrna Levels ◽

Uptake System ◽

Duct Ligation

Expression of the main hepatic bile acid uptake system, the Na+-taurocholate cotransporter (Ntcp), is downregulated during cholestasis. Bile acid-induced, farnesoid X receptor (FXR)-mediated induction of the nuclear repressor short heterodimer partner (SHP) has been proposed as a key mechanism reducing Ntcp expression. However, the role of FXR and SHP or other nuclear receptors and hepatocyte-enriched transcription factors in mediating Ntcp repression in obstructive cholestasis is unclear. FXR knockout (FXR−/−) and wild-type (FXR+/+) mice were subjected to common bile duct ligation (CBDL). Cholic acid (CA)-fed and LPS-treated FXR−/− and FXR+/+ mice were studied for comparison. mRNA levels of Ntcp and SHP and nuclear protein levels of hepatocyte nuclear factor (HNF)-1α, HNF-3β, HNF-4α, retinoid X receptor (RXR)-α, and retinoic acid receptor (RAR)-α and their DNA binding were assessed. Hepatic cytokine mRNA levels were also measured. CBDL and CA led to Ntcp repression in FXR+/+, but not FXR−/−, mice, whereas LPS reduced Ntcp expression in both genotypes. CBDL and LPS but not CA induced cytokine expression and reduced levels of HNF-1α, HNF-3β, HNF-4α, RXRα, and RARα to similar extents in FXR+/+ and FXR−/−. DNA binding of these transactivators was unaffected by CA in FXR+/+ mice but was markedly reduced in FXR−/− mice. In conclusion, Ntcp repression by CBDL and CA is mediated by accumulating bile acids via FXR and does not depend on cytokines, whereas Ntcp repression by LPS is independent of FXR. Reduced levels of HNF-1α, RXRα, and RARα in CBDL FXR−/− mice and reduced DNA binding in CA-fed FXR−/− mice, despite unchanged Ntcp levels, indicate that these factors may have a minor role in regulation of mouse Ntcp during cholestasis.

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Hypocholesterolaemic effect of whole-grain highland hull-less barley in rats fed a high-fat diet

British Journal Of Nutrition ◽

10.1017/s0007114518000831 ◽

2018 ◽

Vol 119 (10) ◽

pp. 1102-1110 ◽

Cited By ~ 8

Author(s):

Xuejuan Xia ◽

Guannan Li ◽

Jiaxin Song ◽

Jiong Zheng ◽

Jianquan Kan

Keyword(s):

Bile Acid ◽

High Fat Diet ◽

Control Diet ◽

Ldl Receptor ◽

Acid Synthesis ◽

Farnesoid X Receptor ◽

High Dose ◽

Whole Grain ◽

Sprague Dawley ◽

High Fat

AbstractWhole-grain highland hull-less barley (WHLB) contains high amounts of bioactive compounds that potentially exhibit cholesterol-lowering effects. This study investigated the hypocholesterolaemic effect of WHLB. A total of seventy-two male Sprague–Dawley rats were divided into four groups and were fed with the normal control diet, high-fat diet (HFD) and HFD containing low or high dose (10 or 48·95 %) of WHLB. High dose of WHLB significantly decreased the organ indexes of liver and abdominal fat and lipid levels of plasma and liver in HFD rats. The lipid regulation effect of WHLB, which was reconfirmed through hepatocyte morphologic observation, was accompanied by a large excretion of bile acids in the small intestinal contents and the faeces. Real-time PCR analyses, which were further reconfirmed through Western blot analyses, revealed that a high dose of WHLB significantly enhanced the hepatic expressions of AMP-activated protein kinase α, cholesterol 7α-hydroxylase, LDL receptor, liver X receptor, and PPARα and decreased the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase. It also enhanced the ileal expression of farnesoid X receptor and resulted in the decrease of expression of apical sodium-dependent bile acid transporter. WHLB exhibited hypocholesterolaemic effects mainly by inhibiting cholesterol synthesis, cholesterol accumulation in peripheral tissue, and bile acid reabsorption and by stimulating bile acid synthesis.

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III. Bile acids and nuclear receptors

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00417.2002 ◽

2003 ◽

Vol 284 (3) ◽

pp. G349-G356 ◽

Cited By ~ 102

Author(s):

John Y. L. Chiang

Keyword(s):

Bile Acid ◽

Cardiovascular Diseases ◽

Bile Acids ◽

Nuclear Receptors ◽

Molecular Mechanisms ◽

Genetic Manipulation ◽

Regulatory Genes ◽

Cholesterol Homeostasis ◽

Physiological Pathways ◽

Bile Acid Receptor

Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Recent studies reveal that bile acids also are signaling molecules that activate several nuclear receptors and regulate many physiological pathways and processes to maintain bile acid and cholesterol homeostasis. Mutations of the principal regulatory genes in bile acid biosynthetic pathways have recently been identified in human patients with hepatobiliary and cardiovascular diseases. Genetic manipulation of key regulatory genes and bile acid receptor genes in mice have been obtained. These advances have greatly improved our understanding of the molecular mechanisms underlying complex liver physiology but also raise many questions and controversies to be resolved. These developments will lead to early diagnosis and discovery of drugs for treatment of liver and cardiovascular diseases.

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The Decrease in Farnesoid X Receptor, Pregnane X Receptor and Constitutive Androstane Receptor in the Liver after Intestinal Ischemia-Reperfusion

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/j38c88 ◽

2012 ◽

Vol 15 (5) ◽

pp. 616 ◽

Cited By ~ 8

Author(s):

Jiro Ogura ◽

Yusuke Terada ◽

Takashi Tsujimoto ◽

Takahiro Koizumi ◽

Kaori Kuwayama ◽

...

Keyword(s):

Western Blotting ◽

Hepg2 Cells ◽

Intestinal Ischemia ◽

Ischemia Reperfusion ◽

Constitutive Androstane Receptor ◽

Pregnane X Receptor ◽

Farnesoid X Receptor ◽

Expression Levels ◽

Intestinal Ischemia Reperfusion

Purpose. Intestinal ischemia-reperfusion (I/R) damages remote organs, including the liver, and promotes multi-organ failure (MOF). However, the molecular mechanisms underlying acute liver injury after intestinal I/R have not been completely elucidated. Farnesoid X receptor (FXR), pregnane X receptor (PXR) and constitutive androstane receptor (CAR) regulate metabolizing enzymes and transporters, and coordinately prevent hepatotoxicity reflecting an inability of appropriate excretion of endogenous toxic compounds. In this study, we assessed FXR, PXR and CAR expression levels and their localization levels in nuclei in the liver after intestinal I/R. We also investigated the effect of IL-6 on FXR, PXR and CAR expression levels and their localization levels in nuclei in in vitro experiments. Methods. We used intestinal I/R model rats. Moreover, HepG2 cells were used in in vitro study. Real-time PCR and Western blotting were used to assess mRNA and protein expression levels. Nuclear receptor localization in nuclei was analyzed by Western blotting using nuclear extracts. Results. FXR and PXR expression levels began to be decreased at 3 h, and FXR, PXR and CAR expression levels were decreased at 6 h after intestinal I/R. The localization levels of FXR, PXR and CAR in nuclei began to be decreased at 3 h, and all of them were decreased at 6 h after intestinal I/R. In HepG2 cells, FXR, PXR and CAR expression levels were decreased by 0.5-1 ng/mL, 0.5-100 ng/mL and 100 ng/mL IL-6 treatment for 24 h, respectively. FXR, PXR and CAR localization levels in nuclei were suppressed by 0.5-10 ng/mL, 10-100 ng/mL and 10-100 ng/mL IL-6 treatment for 24 h, respectively. Conclusions. FXR, PXR and CAR expression levels are decreased in the liver after intestinal I/R. IL-6 is one of main causes the decreases in expressions of these receptors. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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FXR agonist GW4064 improves liver and intestinal pathology and alters bile acid metabolism in rats undergoing small intestinal resection

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00356.2017 ◽

2019 ◽

Vol 317 (2) ◽

pp. G108-G115 ◽

Cited By ~ 4

Author(s):

Yi Cao ◽

Yongtao Xiao ◽

KeJun Zhou ◽

Junkai Yan ◽

Panliang Wang ◽

...

Keyword(s):

Liver Disease ◽

Bile Acid ◽

Rat Model ◽

Target Genes ◽

Bowel Resection ◽

Farnesoid X Receptor ◽

Bile Acid Metabolism ◽

Short Bowel ◽

Expression Levels ◽

The Impact

Mortality associated with liver disease has been observed in patients with short bowel syndrome (SBS); however, its mechanism remains unclear, but bile acid (BA) dysmetabolism has been proposed as a possible cause. The farnesoid X receptor (FXR) is the key regulator of BA synthesis. Here, we showed that, in a rat model of short bowel resection associated with liver disease (SBR-ALD), the BA composition of hepatic tissues reflected a larger proportion of primary and secondary unconjugated BAs, whereas that of the colon contents and serum showed an increased ratio of secondary unconjugated BAs. Both hepatic and intestinal regulation of BA synthesis was characterized by a blunted hepatic FXR activation response. The mRNA expression levels of cholesterol 7a-hydroxylase ( CYP7A1), sterol 12a-hydroxylase ( CYP8B1), and sterol 27 hydroxylase ( CYP27A1), the key enzymes in BA synthesis, were upregulated. After intervention with the FXR agonist GW4064, both the liver histology and serum transaminase activity were improved, which demonstrated the attenuation of SBR-ALD. The BA compositions of hepatic tissue, the colon contents, and serum recovered and were closer to those of the sham group. The expression levels of hepatic FXR increased, and its target genes were activated. Consistent with this, the expression levels of CYP7A1, CYP8B1, and CYP27A1 were downregulated. Ileum tissue FXR and its target genes were slightly elevated. This study showed that the FXR agonist GW4064 could correct BA dysmetabolism to alleviate hepatotoxicity in SBR animals. GW4064 intervention resulted in a decrease in fecal bile excretion and elevated plasma/hepatic conjugated BA levels. GW4064 increased the reabsorption of conjugated BAs by inducing apical sodium-dependent bile salt transporter expression in the ileum. Concomitantly, FXR activation in the presence of GW4064 decreased BA production by repressing the expression of key synthetases, including CYP7A1, CYP8B1, and CYP27A1. These findings provide a clinical research direction for the prevention of liver disease in patients with SBS. NEW & NOTEWORTHY This study assessed the impact of treatment with GW4064, a farnesoid X receptor agonist, on the development of short bowel resection (SBR) associated with liver disease in a rat model of SBR. GW4064 was able to correct bile acid dysmetabolism and alleviate hepatotoxicity in SBR animals.

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Knockdown of ATP8B1 expression leads to specific downregulation of the bile acid sensor FXR in HepG2 cells: effect of the FXR agonist GW4064

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.90371.2008 ◽

2009 ◽

Vol 296 (5) ◽

pp. G1119-G1129 ◽

Cited By ~ 21

Author(s):

Pilar Martínez-Fernández ◽

Loreto Hierro ◽

Paloma Jara ◽

Luis Alvarez

Keyword(s):

Bile Acid ◽

Hepg2 Cells ◽

Target Genes ◽

Constitutive Androstane Receptor ◽

Pregnane X Receptor ◽

Acid Synthesis ◽

Bile Acid Synthesis ◽

Bile Secretion ◽

Farnesoid X Receptor ◽

Mrna Levels

Farnesoid X receptor (FXR) is a bile acid-sensing nuclear receptor that controls bile acid homeostasis. It has been suggested that downregulation of FXR contributes to the pathogenesis of an inherited disorder of bile secretion caused by mutations in ATP8B1. We have investigated the relationship between ATP8B1 knockdown and FXR downregulation in the human hepatoblastoma cell line HepG2. Transfection of HepG2 cells with ATP8B1 small interfering RNA (siRNA) duplexes led to a 60% reduction in the endogenous levels of ATP8B1 mRNA and protein and a concomitant decrease in FXR mRNA and protein content, as well as in FXR phosphorylation. This decrease was accompanied by a marked reduction in mRNA levels of a subset of FXR targets, such as bile salt export pump ( ABCB11), small heterodimer partner, and uridine 5′-diphosphate-glucuronosyltransferase. ATP8B1 inhibition specifically targeted FXR since mRNA expression of other prominent nuclear receptors, such as pregnane X receptor and constitutive androstane receptor, or liver-enriched transcription factors, such as hepatocyte nuclear factor 1α ( HNF-1α) and HNF-4α, was not altered. The expression of other key genes involved in bile acid synthesis, detoxification, and transport also remained unchanged upon ATP8B1 knockdown. Supporting the specificity of the effect, siRNA-mediated silencing of ABCB11, whose defect is associated with another inherited disorder of bile secretion, did not affect FXR expression. Treatment with the synthetic FXR agonist GW4064 was able to partially neutralize ATP8B1 siRNA-mediated FXR downregulation and fully counteract inhibition of FXR target genes. Collectively these findings indicate that ATP8B1 knockdown specifically downregulates FXR, and this action can be circumvented by treatment with FXR agonists.

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The Xenobiotic-Sensing Nuclear Receptors Pregnane X Receptor, Constitutive Androstane Receptor, and Orphan Nuclear Receptor Hepatocyte Nuclear Factor 4α in the Regulation of Human Steroid-/Bile Acid-Sulfotransferase

Molecular Endocrinology ◽

10.1210/me.2007-0002 ◽

2007 ◽

Vol 21 (9) ◽

pp. 2099-2111 ◽

Cited By ~ 51

Author(s):

Ibtissam Echchgadda ◽

Chung S. Song ◽

Taesung Oh ◽

Mohamed Ahmed ◽

Isidro John De La Cruz ◽

...

Keyword(s):

Bile Acid ◽

Nuclear Receptors ◽

Constitutive Androstane Receptor ◽

Pregnane X Receptor ◽

Nuclear Factor ◽

Orphan Nuclear Receptor ◽

Hepatocyte Nuclear Factor ◽

Site Mutation ◽

Composite Element ◽

Hepatocyte Nuclear Factor 4Α

Abstract The nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are the primary transcription factors coordinating induced expression of the enzymes and proteins directing oxidative, conjugative, and transport phases of endobiotic and xenobiotic metabolism, whereas hepatocyte nuclear factor 4α (HNF4α), a regulator of hepatic lipid homeostasis, can modify the PXR/CAR response. Steroid- and bile acid-sulfotransferase (SULT2A1) promotes phase II metabolism through its sulfonating action on certain endobiotics, including steroids and bile acids, and on diverse xenobiotics, including therapeutic drugs. This study describes characterization of a PXR- and CAR-inducible composite element in the human SULT2A1 promoter and its synergistic interaction with HNF4α. Inverted and direct repeats of AG(G/T)TCA (IR2 and DR4), both binding to PXR and CAR, define the composite element. Differential recognition of the composite element by PXR and CAR is evident because single-site mutation at either IR2 or DR4 in the natural gene abolished the PXR response, whereas mutations at both repeats were necessary to abrogate completely the CAR response. The composite element conferred xenobiotic response to a heterologous promoter, and the cognate ligands induced PXR and CAR recruitment to the chromatin-associated response region. An HNF4α element adjacent to the −30 position enhanced basal promoter activity. Although functioning as a synergizer, the HNF4α element was not essential for the PXR/CAR response. An emerging role of SULT2A1 in lipid and caloric homeostasis suggests that illumination on the regulatory interactions driving human SULT2A1 expression may reveal new avenues to control certain metabolic disorders.

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Mechanisms of Tauroursodeoxycholate-Mediated Hepatoprotection

Digestive Diseases ◽

10.1159/000450915 ◽

2017 ◽

Vol 35 (3) ◽

pp. 224-231 ◽

Cited By ~ 6

Author(s):

Dieter Häussinger ◽

Claus Kordes

Keyword(s):

Bile Acid ◽

Bile Acids ◽

Molecular Mechanisms ◽

Clinical Medicine ◽

Basolateral Membrane ◽

Sodium Taurocholate ◽

Growth Factor Receptor ◽

Adenosine Monophosphate ◽

Farnesoid X Receptor ◽

Integrin Subunit

Ursodeoxycholate and its taurine conjugate tauroursodeoxycholate (TUDC) promote choleresis by triggering the insertion of transport proteins for bile acids into the canalicular and basolateral membranes of hepatocytes. In addition, TUDC exerts hepatoprotective and anti-apoptotic effects, can counteract the action of toxic bile acids and reduce endoplasmic reticulum stress. TUDC can also initiate the differentiation of multipotent mesenchymal stem cells (MSC) including hepatic stellate cells and promote their development into hepatocyte-like cells. Although the hepatoprotective and choleretic action of TUDC is empirically used in clinical medicine since decades, the underlying molecular mechanisms remained largely unclear. Since TUDC has little or no potency to activate known bile acid receptors, such as farnesoid X receptor and transmembrane G protein-coupled bile acid receptor, other receptors must be involved in TUDC-mediated signaling. Recent research demonstrates that integrins serve as sensors for TUDC. After binding of TUDC to α5β1-integrin, the β1-integrin subunit becomes activated through a conformational change, thereby triggering integrin signaling with the downstream activation of focal adhesion kinase, c-Src, the epidermal growth factor receptor and activation of the mitogen-activated protein kinases, Erks and p38. These events trigger choleresis through a coordinated insertion of the sodium-taurocholate cotransporting polypeptide into the basolateral membrane and of the bile salt export pump into the canalicular membrane. In addition to its choleretic action, TUDC-induced integrin activation triggers a cyclic adenosine monophosphate-dependent protein kinase A activation in hepatocytes, which provides the basis for the anti-apoptotic effect of TUDC. On the other hand, the TUDC-induced stimulation of MSC differentiation appears not to be mediated by integrins. This article gives a brief overview about our work on the signaling network-mediating hepatoprotection by TUDC.

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