Ursodeoxycholic acid exerts farnesoid X receptor-antagonistic effects on bile acid and lipid metabolism in morbid obesity.

Background & Aims: Bile acids (BAs) are major regulators of hepatic BA and lipid metabolism but their mechanisms of action in non-alcoholic fatty liver disease (NAFLD) are still poorly understood. Here we aimed to explore the molecular and biochemical mechanisms of ursodeoxycholic acid (UDCA) in modulating the cross-talk between liver and visceral white adipose tissue (vWAT) regarding BA and cholesterol metabolism and fatty acid/lipid partitioning in morbidly obese NAFLD patients.

Methods: In this randomized controlled pharmacodynamic study, we analyzed serum, liver and vWAT samples from 40 well-matched morbidly obese patients receiving UDCA (20 mg/kg/day) or no treatment three weeks prior to bariatric surgery.

Gallstone disease in Swedish twins is associated with the Gilbert variant of UGT1A1.

Background & Aims: The Gilbert syndrome-associated functional TATA box variant UGT1A1*28 (A(TA)7TAA) was found to increase susceptibility to pigment gallstone formation in patients with haemolytic anaemia. Further studies in extensive cohorts demonstrated an increased risk of this variant for cholesterol gallstone disease (GD). We now investigated this polymorphism as a determinant of symptomatic GD in Swedish twins.

The genetic background of gallstone formation: an update.

Gallstone disease is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems that is expected to increase in ageing populations at risk. This review summarizes recent data on the genetic background of cholesterol gallstones and the role of biliary lipid composition. Three previously unknown non-synonymous mutations in the ABCB4 gene encoding the hepatobiliary phospholipid-flippase MDR3 are presented.

ACAT2 and human hepatic cholesterol metabolism: identification of important gender-related differences in normolipidemic, non-obese Chinese patients.

Objective: ACAT2 is a major cholesterol esterification enzyme specifically expressed in hepatocytes and may control the amount of hepatic free (unesterified) cholesterol available for secretion into bile or into HDL. This study aims to further elucidate physiologic roles of ACAT2 in human hepatic cholesterol metabolism.

Methods And Results: Liver biopsies from 40 normolipidemic, non-obese gallstone patients including some gallstone-free patients (female/male, 18/22) were collected and analyzed for microsomal ACAT2 activity, protein and mRNA expression.

Cholesterol synthesis inhibition elicits an integrated molecular response in human livers including decreased ACAT2.

Objective: The purpose of this study was to identify how different degrees of cholesterol synthesis inhibition affect human hepatic cholesterol metabolism.

Methods And Results: Thirty-seven normocholesterolemic gallstone patients randomized to treatment with placebo, 20 mg/d fluvastatin, or 80 mg/d atorvastatin for 4 weeks were studied. Based on serum lathosterol determinations, cholesterol synthesis was reduced by 42% and 70% in the 2 groups receiving statins.

Hypocholesterolemic effects of fatty acid bile acid conjugates (FABACs) in mice.

Fatty acid bile acid conjugates (FABACs) prevent and dissolve cholesterol gallstones and prevent diet induced fatty liver, in mice. The present studies aimed to test their hypocholesterolemic effects in mice. Gallstone susceptible (C57L/J) mice, on high fat (HFD) or regular diet (RD), were treated with the conjugate of cholic acid with arachidic acid (FABAC; Aramchol).

Increased expression of LXR alpha, ABCG5, ABCG8, and SR-BI in the liver from normolipidemic, nonobese Chinese gallstone patients.

Cholesterol supersaturation of bile is one prerequisite for gallstone formation. In the present study of Chinese patients with gallstones, we investigated whether this phenomenon was correlated with the hepatic expression of genes participating in the metabolism of cholesterol and bile acids. Twenty-two nonobese, normolipidemic patients (female-male, 11:11) with gallstones were investigated with 13 age- and body mass index-matched gallstone-free controls (female-male, 10:3).

Ethanol stimulates bile acid formation in primary human hepatocytes.

The conversion of cholesterol to bile acids is a key pathway for elimination of cholesterol from the body, thereby reducing the risk of arteriosclerosis. Moderate consumption of ethanol has been shown to have preventive effects on cardiovascular disease and decrease the risk of gallstone formation. In the present study primary human hepatocytes were used to investigate if ethanol affected bile acid synthesis.

Involvement of corepressor complex subunit GPS2 in transcriptional pathways governing human bile acid biosynthesis.

Coordinated regulation of bile acid biosynthesis, the predominant pathway for hepatic cholesterol catabolism, is mediated by few key nuclear receptors including the orphan receptors liver receptor homolog 1 (LRH-1), hepatocyte nuclear factor 4alpha (HNF4alpha), small heterodimer partner (SHP), and the bile acid receptor FXR (farnesoid X receptor). Activation of FXR initiates a feedback regulatory loop via induction of SHP, which suppresses LRH-1- and HNF4alpha-dependent expression of cholesterol 7alpha hydroxylase (CYP7A1) and sterol 12alpha hydroxylase (CYP8B1), the two major pathway enzymes. Here we dissect the transcriptional network governing bile acid biosynthesis in human liver by identifying GPS2, a stoichiometric subunit of a conserved corepressor complex, as a differential coregulator of CYP7A1 and CYP8B1 expression.

Differential hepatocellular zonation pattern of cholesterol 7alpha-hydroxylase (Cyp7a1) and sterol 12alpha-hydroxylase (Cyp8b1) in the mouse.

The synthesis of primary bile acids is confined to the hepatocytes. This study aimed to evaluate the expression pattern within the liver architecture of the rate-limiting enzyme of the neutral pathway, cholesterol 7alpha-hydroxylase (Cyp7a1), and sterol 12alpha-hydroxylase (Cyp8b1), the enzyme necessary for the synthesis of cholic acid. Specific Cyp8b1 and Cyp7a1 peptide antiserums were used for immunohistochemical staining of livers from wild type and Cyp8b1 null mice, the latter instead expressing beta-galactosidase (beta-Gal) as a replacement reporter gene.

Analysis of ileal sodium/bile acid cotransporter and related nuclear receptor genes in a family with multiple cases of idiopathic bile acid malabsorption.

The etiology of most cases of idiopathic bile acid malabsorption (IBAM) is unknown. In this study, a Swedish family with bile acid malabsorption in three consecutive generations was screened for mutations in the ileal apical sodium-bile acid cotransporter gene (ASBT; gene symbol, SLC10A2) and in the genes for several of the nuclear receptors known to be important for ASBT expression: the farnesoid X receptor (FXR) and peroxisome proliferator activated receptor alpha (PPARalpha). The patients presented with a clinical history of idiopathic chronic watery diarrhea, which was responsive to cholestyramine treatment and consistent with IBAM.

Critical role of cholic acid for development of hypercholesterolemia and gallstones in diabetic mice.

We studied bile acid and cholesterol metabolism in insulin-dependent diabetes utilizing genetically modified mice unable to synthesize cholic acid (Cyp8b1-/-). Diabetes was induced in Cyp8b1-/- and wild type animals (Cyp8b1+/+) by alloxan, and the mice were fed normal or cholesterol-enriched diet for 10 weeks. The serum levels of cholesterol were strongly increased in diabetic Cyp8b1+/+ mice fed cholesterol, while diabetic Cyp8b1-/- mice did not show any aberrations regardless of the diet.

Gallbladder bile composition in patients with Crohn 's disease.

Aim: To further elucidate the pathogenesis and mechanisms of the high risk of gallstone formation in Crohn's disease.

Methods: Gallbladder bile was obtained from patients with Crohn's disease who were admitted for elective surgery (17 with ileal/ileocolonic disease and 7 with Crohn's colitis). Fourteen gallstone patients served as controls.

Gastrointestinal absorption of metallic mercury.

The absorption of mercury from the gastrointestinal systems of 7 subjects, of whom none had any amalgam fillings, was examined in this study. The authors obtained quantitative information about mercury concentration in plasma and duodenal fluid after the gastrointestinal systems of the subjects were exposed to liquid elemental mercury enclosed in rubber balloons (i.e.

Successful treatment of severe unconjugated hyperbilirubinemia via induction of UGT1A1 by rifampicin.

We report two patients with uncommon Gilbert's syndrome with severe unconjugated hyperbilirubinemia which was reduced from 200 to 60-90 micromol/L by long-term administration of rifampicin. Hepatic induction of bilirubin-glucuronosyltransferase was suggested by increased relative amounts of conjugated serum bilirubin. This molecular mechanism was confirmed in primary cultures of human hepatocytes.

Common polymorphisms in the CYP7A1 gene do not contribute to variation in rates of bile acid synthesis and plasma LDL cholesterol concentration.

Transcriptional regulation of the cholesterol 7alpha-hydroxylase (CYP7AI) gene is of critical importance for bile acid and cholesterol metabolism. We evaluated the physiological significance of two common polymorphisms (-203C/A and -469T/C) in the promoter region of the CYP7AI gene. No evidence was found for physiological differences between either the -203C and -203A alleles or the -469T and -469C alleles in transient transfection studies using native 834bp promoter constructs.

Complementary stimulation of hepatobiliary transport and detoxification systems by rifampicin and ursodeoxycholic acid in humans.

Background & Aims: Rifampicin (RIFA) and ursodeoxycholic acid (UDCA) improve symptoms and biochemical markers of liver injury in cholestatic liver diseases by largely unknown mechanisms. We aimed to study the molecular mechanisms of action of these drugs in humans.

Methods: Thirty otherwise healthy gallstone patients scheduled for cholestectomy were randomized to RIFA (600 mg/day for 1 week) or UDCA (1 g/day for 3 weeks) or no medication before surgery.

Human sterol 12a-hydroxylase (CYP8B1) is mainly expressed in hepatocytes in a homogenous pattern.

The liver is the only organ where the complete synthesis of bile acids takes place. The present study was undertaken to investigate whether regional differences exist within the individual human hepatic lobuli regarding the pattern of expression of sterol 12alpha-hydroxylase (CYP8B1), a key enzyme in bile acid synthesis. A specific anti-human CYP8B1 peptide antiserum was developed and used for Western blotting and hepatic immunostaining of livers from various patients.

Changes in gallbladder bile composition and crystal detection time in morbidly obese subjects after bariatric surgery.

The aim of the present study was to elucidate the mechanisms of development of cholesterol crystals and gallstones during weight reduction in obese subjects. Twenty-five morbidly obese, gallstone-free subjects underwent vertical-banded gastroplasty. Gallbladder bile was collected at the time of the operation via needle aspiration and 1.

Feedback regulation of bile acid synthesis in human liver: importance of HNF-4alpha for regulation of CYP7A1.

A great number of nuclear factors are involved in the negative feedback mechanism regulating bile acid synthesis. There are two major ways for the negative feedback to effect the synthesis; the SHP-dependent, involving FXR, and the SHP-independent way, affecting HNF-4alpha. We studied 23 patients with gallstone disease.

Genetic and environmental influences on symptomatic gallstone disease: a Swedish study of 43,141 twin pairs.

The contribution of hereditary and environmental factors to the pathogenesis of symptomatic gallstone disease is still unclear. We estimated the relative importance of genetic and environmental factors by analyzing a large population of twins. For this purpose, the Swedish Twin Registry was linked with the Swedish inpatient-discharge and causes of death registries for symptomatic gallstone disease and gallstone surgery-related diagnoses in 43,141 twin pairs born between 1900 and 1958.

Ursodeoxycholic acid treatment in IBD-patients with colorectal dysplasia and/or DNA-aneuploidy: a prospective, double-blind, randomized controlled pilot study.

Background & Aims: There is an increased risk of colorectal carcinoma (CRC) in patients with longstanding, extensive colonic inflammatory bowel disease (IBD). Primary sclerosing cholangitis, family history of CRC, mucosal dysplasia and DNA-aneuploidy are other risk factors. Recently, results from animal studies have shown that the bile acid ursodeoxycholic acid (UDCA) has a favourable impact on experimentally-induced CRC/neoplasia in rats.

ACAT2 is localized to hepatocytes and is the major cholesterol-esterifying enzyme in human liver.

Background: Two acyl-coenzyme A:cholesterol acyltransferase (ACAT) genes, ACAT1 and ACAT2, have been identified that encode 2 proteins responsible for intracellular cholesterol esterification.

Methods And Results: In this study, immunohistology was used to establish their cellular localization in human liver biopsies. ACAT2 protein expression was confined to hepatocytes, whereas ACAT1 protein was found in Kupffer cells only.

Mechanisms of cholesterol and sterol regulatory element binding protein regulation of the sterol 12alpha-hydroxylase gene (CYP8B1).

Sterol 12alpha-hydroxylase (CYP8B1) is an obligatory enzyme for the synthesis of cholic acid and regulation of liver bile acid synthesis and intestine cholesterol absorption. The present study evaluates the roles for sterol regulatory element binding proteins (SREBPs) in the regulation of the CYP8B1 gene. Cholesterol feeding of mice and rats decreased the activity of CYP8B1, contrary to the up-regulation of cholesterol 7alpha-hydroxylase (CYP7A1).