Hanns-Ulrich Marschall

Intrahepatic cholestasis of pregnancy: Relationships between bile acid levels and fetal complication rates.

Intrahepatic cholestasis of pregnancy (ICP), characterized by pruritus in the second half of pregnancy, entails an increased risk to the fetus. This study was designed to determine the incidence and fetal complication rates in ICP, and to define groups at increased risk. In an prospective cohort study conducted between February 1, 1999, and January 31, 2002, all 45,485 pregnancies in a defined region of Sweden (Västra Götaland) were screened for ICP, defined as otherwise unexplained pruritus of pregnancy in combination with fasting serum bile acid levels ≥10 μmol/L. Pruritus was reported by 937 (2.1%) women, and ICP was diagnosed in 693 (1.5%). Simple logistic regression analyses showed that the probability of fetal complications (spontaneous preterm deliveries, asphyxial events, and meconium staining of amniotic fluid, placenta, and membranes) increased by 1%–2% per additional μmol/L of serum bile acids. Complementary analyses showed that fetal complications did not arise until bile acid levels were ≥40 μmol/L. Gallstone disease and a family history of ICP were significantly (P < .001) more prevalent in the group of ICP patients with higher bile acid levels. In conclusion, we found an incidence of ICP in our population of 1.5%. From complication rates recorded prospectively, we could define a mild (81%) and a severe (19%) form of ICP, the latter with bile acid levels ≥40 μmol/L. No increase in fetal risk was detected in ICP patients with bile acid levels < 40 μmol/L, and we propose that these women be managed expectantly, which would significantly reduce the costs of medical care. (HEPATOLOGY 2004;40:467–474.)

Intrahepatic cholestasis of pregnancy: molecular pathogenesis, diagnosis and management

Frank Lammert, Hanns-Ulrich Marschall1, Anna Glantz2 and Siegfried Matern Department of Internal Medicine III, Aachen University of Technology – RWTH, Aachen, Germany, 1Karolinska Institutet, Department of Medicine, Division of Gastroenterology and Hepatology, Huddinge University Hospital, Stockholm, and 2Department of Obstetrics and Gynecology, Sahlgren’s University Hospital, East, Göteborg, Sweden

CAR and PXR agonists stimulate hepatic bile acid and bilirubin detoxification and elimination pathways in mice

Induction of hepatic phase I/II detoxification enzymes and alternative excretory pumps may limit hepatocellular accumulation of toxic biliary compounds in cholestasis. Because the nuclear xenobiotic receptors constitutive androstane receptor (CAR) and pregnane X receptor (PXR) regulate involved enzymes and transporters, we aimed to induce adaptive alternative pathways with different CAR and PXR agonists in vivo. Mice were treated with the CAR agonists phenobarbital and 1,4‐bis‐[2‐(3,5‐dichlorpyridyloxy)]benzene, as well as the PXR agonists atorvastatin and pregnenolone‐16α‐carbonitrile. Hepatic bile acid and bilirubin‐metabolizing/detoxifying enzymes (Cyp2b10, Cyp3a11, Ugt1a1, Sult2a1), their regulatory nuclear receptors (CAR, PXR, farnesoid X receptor), and bile acid/organic anion and lipid transporters (Ntcp, Oatp1,2,4, Bsep, Mrp2‐4, Mdr2, Abcg5/8, Asbt) in the liver and kidney were analyzed via reverse‐transcriptase polymerase chain reaction and Western blotting. Potential functional relevance was tested in common bile duct ligation (CBDL). CAR agonists induced Mrp2‐4 and Oatp2; PXR agonists induced only Mrp3 and Oatp2. Both PXR and CAR agonists profoundly stimulated bile acid–hydroxylating/detoxifying enzymes Cyp3a11 and Cyp2b10. In addition, CAR agonists upregulated bile acid–sulfating Sult2a1 and bilirubin‐glucuronidating Ugt1a1. These changes were accompanied by reduced serum levels of bilirubin and bile acids in healthy and CBDL mice and by increased levels of polyhydroxylated bile acids in serum and urine of cholestatic mice. Atorvastatin significantly increased Oatp2, Mdr2, and Asbt, while other transporters and enzymes were moderately affected. In conclusion, administration of specific CAR or PXR ligands results in coordinated stimulation of major hepatic bile acid/bilirubin metabolizing and detoxifying enzymes and hepatic key alternative efflux systems, effects that are predicted to counteract cholestasis. (HEPATOLOGY 2005.)

Adaptive changes in hepatobiliary transporter expression in primary biliary cirrhosis

BACKGROUND/AIMS Information about alterations of hepatobiliary transporter expression in primary biliary cirrhosis (PBC) could provide important insights into the pathogenesis of cholestasis. This study aimed to determine the expression of hepatobiliary transport systems for bile salts (Na(+)/taurocholate cotransporter, NTCP; bile salt export pump, BSEP), organic anions (organic anion transporting protein, OATP2; canalicular conjugate export pump, MRP2; basolateral MRP homologue, MRP3), organic cations (canalicular multidrug export pump, MDR1), and phospholipids (canalicular phospholipid flippase MDR3) in livers from patients with advanced stages of PBC. METHODS Transporter mRNA and protein levels were assessed by reverse transcription polymerase chain reaction and Western blot analysis. Tissue distribution of transporters was investigated by immunohistochemistry and immunofluorescence microscopy. Hepatic bile acids were measured by gas chromatography-mass spectrometry. RESULTS Compared to controls, basolateral uptake systems (NTCP, OATP2) were reduced, canalicular export pumps for bile salts and bilirubin (BSEP, MRP2) were preserved, while canalicular MDR P-glycoproteins (MDR1, MDR3) and the basolateral efflux pump MRP3 were increased in PBC. Double immunofluorescence labeling with a canalicular marker (dipeptidyl peptidase IV) demonstrated proper canalicular localization of BSEP and MRP2 in PBC. OATP2 and MRP2 expression correlated inversely with hepatic levels of hydrophobic bile acids, while positively correlating with hepatic enrichment with ursodeoxycholic acid. CONCLUSIONS Down-regulation of basolateral uptake systems and maintenance/up-regulation of canalicular and basolateral efflux pumps may represent adaptive mechanisms limiting the accumulation of toxic biliary constituents.

Role of farnesoid X receptor in determining hepatic ABC transporter expression and liver injury in bile duct-ligated mice

BACKGROUND & AIMS Cholestasis induces changes in hepatic adenosine triphosphate-binding cassette (ABC) transporter expression. We aimed to investigate the role of the nuclear bile acid receptor (farnesoid X receptor [FXR]) in mediating changes in ABC transporter expression and in determining liver injury. METHODS Hepatic ABC transporter (multidrug resistance-associated proteins [Mrp] 2-4 and bile salt export pump [Bsep]) expression and localization were studied in common bile duct-ligated (CBDL) FXR knockout (FXR(-/-)), wild-type (FXR(+/+)), and sham-operated mice. Serum alanine aminotransferase, alkaline phosphatase, bilirubin and bile acid levels, hepatic bile acid composition, and liver histology were investigated. Cholangiomanometry and bile duct morphometry were performed. RESULTS CBDL induced expression of Mrp 3 and Mrp 4 in FXR(+/+) and even more in FXR(-/-), whereas Mrp 2 expression remained unchanged. Bsep expression was maintained in CBDL FXR(+/+) but remained undetectable in CBDL FXR(-/-). Alanine aminotransferase levels and mortality rates did not differ between CBDL FXR(+/+) and FXR(-/-). CBDL increased biliary pressure and induced bile ductular proliferation and bile infarcts in FXR(+/+), whereas FXR(-/-) had lower biliary pressures, less ductular proliferation, and developed disseminated liver cell necroses. CONCLUSIONS Overexpression of Mrp 3 and Mrp 4 in CBDL mice is FXR independent and could play an important role in the adaptive hepatic ABC transporter response to cholestasis. Maintenance of Bsep expression strictly depends on FXR and is a critical determinant of the cholestatic phenotype. Lack of bile infarcts in CBDL FXR(-/-) suggests that development of bile infarcts is related to bile acid-dependent bile flow and biliary pressure. This information is relevant for the potential use of FXR modulators in the treatment of cholestatic liver diseases.

Intrahepatic cholestasis of pregnancy: A randomized controlled trial comparing dexamethasone and ursodeoxycholic acid†

Intrahepatic cholestasis of pregnancy (ICP) is characterized by troublesome maternal pruritus, elevated serum bile acids (≥10 μmol/L) and increased fetal risk. Recently we determined a cutoff level of serum bile acids, ≥40 μmol/L, to be associated with impaired fetal outcome. We have now studied the effects of ursodeoxycholic acid (UDCA) and dexamethasone on pruritus, biochemical markers of cholestasis, and fetal complication rates in a double‐blind, placebo‐controlled trial. For this purpose, 130 women with ICP were randomly allocated to UDCA (1 g/day for three weeks), or dexamethasone (12 mg/day for 1 week and placebo during weeks 2 and 3), or placebo for 3 weeks. Pruritus and biochemical markers of cholestasis were analyzed at inclusion and after 3 weeks of treatment. Fetal complications (spontaneous preterm delivery; asphyxial events; and meconium staining of amniotic fluid, placenta, and membranes) were registered at delivery. An intention‐to‐treat analysis showed significant reduction of alanine aminotransferase (ALT) (P = .01) and bilirubin (P = .002) in the UDCA group only. In a subgroup analysis of ICP women with serum bile acids ≥40 μmol/L at inclusion (n = 34), UDCA had significant effects on pruritus (−75%), bile acids (−79%), ALT (−80%), and bilirubin (−50%) as well, but not on fetal complication rates. Dexamethasone yielded no alleviation of pruritus or reduction of ALT and was less effective than UDCA at reducing bile acids and bilirubin. In conclusion, 3 weeks of UDCA treatment improved some biochemical markers of ICP irrespective of disease severity, whereas significant relief from pruritus and marked reduction of serum bile acids were only found in patients with severe ICP. (HEPATOLOGY 2005;42:1399–1405.)

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. Concordance rates, correlations, and odds ratios were calculated for males, females, monozygotic, and dizygotic twins, respectively, as well as for twin pairs of opposite sex. Structural equation modeling techniques were used to estimate the contributions of genetic effects as well as shared and non‐shared environmental factors to the development of symptomatic gallstone disease. We found that concordances and correlations were higher in monozygotic compared with dizygotic twins, both for males and females. Of note, there were no significant sex differences in heritability. In the full model, genetic effects accounted for 25% (95% CI, 9%–40%), shared environmental effects for 13% (95% CI, 1%–25%), and unique environmental effects for 62% (95% CI, 56%–68%) of the phenotypic variance among twins. In conclusion, our results show heritability to be a major susceptibility factor for symptomatic gallstone disease, consistent with results from previous, much smaller studies. (HEPATOLOGY 2005.)

Role of nuclear bile acid receptor, FXR, in adaptive ABC transporter regulation by cholic and ursodeoxycholic acid in mouse liver, kidney and intestine

BACKGROUND/AIMS Adaptive changes in transporter expression in liver and kidney provide alternative excretory pathways for biliary constituents during cholestasis and may thus attenuate liver injury. Whether adaptive changes in ATP-binding cassette (ABC) transporter expression are stimulated by bile acids and their nuclear receptor FXR is unknown. METHODS Hepatic, renal and intestinal ABC transporter expression was compared in cholic acid (CA)- and ursodeoxycholic acid (UDCA)-fed wild-type (FXR(+/+)) and FXR knock-out mice (FXR(-/-)). Expression was assessed by reverse transcription-polymerase chain reaction, immunoblotting and immunofluorescence microscopy. RESULTS CA feeding stimulated hepatic Mrp2, Mrp3, Bsep and renal Mrp2 as well as intestinal Mrp2 and Mrp3 expression. Lack of Bsep induction by CA in FXR(-/-) was associated with disseminated hepatocyte necrosis which was not prevented by compensatory induction of Mrp2 and Mrp3. With the exception of Bsep, UDCA stimulated expression of hepatic, renal and intestinal ABC transporters independent of FXR without inducing liver toxicity. CONCLUSIONS Toxic CA and non-toxic UDCA induce adaptive ABC transporter expression, independent of FXR with the exception of Bsep. Stimulation of hepatic Mrp3 as well as intestinal and renal Mrp2 by UDCA may contribute to its therapeutic effects by inducing alternative excretory routes for bile acids and other cholephiles.

Side Chain Structure Determines Unique Physiologic and Therapeutic Properties of norUrsodeoxycholic Acid in Mdr2−/− Mice

24‐norursodeoxycholic acid (norUDCA), a side chain–modified ursodeoxycholic acid derivative, has dramatic therapeutic effects in experimental cholestasis and may be a promising agent for the treatment of cholestatic liver diseases. We aimed to better understand the physiologic and therapeutic properties of norUDCA and to test if they are related to its side chain length and/or relative resistance to amidation. For this purpose, Mdr2−/− mice, a model for sclerosing cholangitis, received either a standard diet or a norUDCA‐, tauro norursodeoxycholic acid (tauro‐ norUDCA)‐, or di norursodeoxycholic acid (di norUDCA)‐enriched diet. Bile composition, serum biochemistry, liver histology, fibrosis, and expression of key detoxification and transport systems were investigated. Direct choleretic effects were addressed in isolated bile duct units. The role of Cftr for norUDCA‐induced choleresis was explored in Cftr−/− mice. norUDCA had pharmacologic features that were not shared by its derivatives, including the increase in hepatic and serum bile acid levels and a strong stimulation of biliary HCO3− ‐output. norUDCA directly stimulated fluid secretion in isolated bile duct units in a HCO3− ‐dependent fashion to a higher extent than the other bile acids. Notably, the norUDCA significantly stimulated HCO 3− ‐output also in Cftr−/− mice. In Mdr2−/− mice, cholangitis and fibrosis strongly improved with norUDCA, remained unchanged with tauro‐ norUDCA, and worsened with di norUDCA. Expression of Mrp4, Cyp2b10, and Sult2a1 was increased by norUDCA and di norUDCA, but was unaffected by tauro‐ norUDCA. Conclusion:The relative resistance of norUDCA to amidation may explain its unique physiologic and pharmacologic properties. These include the ability to undergo cholehepatic shunting and to directly stimulate cholangiocyte secretion, both resulting in a HCO3− ‐rich hypercholeresis that protects the liver from cholestatic injury. (HEPATOLOGY 2009;49:1972–1981.)

Intrahepatic cholestasis of pregnancy: the severe form is associated with common variants of the hepatobiliary phospholipid transporter ABCB4 gene

Background: Intrahepatic cholestasis of pregnancy (ICP) is characterised by troublesome maternal pruritus, raised serum bile acid levels and increased fetal risk. Mutations of the ABCB4 gene encoding the hepatobiliary phospholipid transporter have been identified in a small proportion of patients with cholestasis of pregnancy. In a recent prospective study on 693 patients with cholestasis of pregnancy, a cut-off level for serum bile acid (⩾40 μmol/l) was determined for increased risk of fetal complications. Objectives: To investigate whether common combinations of polymorphic alleles (haplotypes) of the genes encoding the hepatobiliary ATP-binding cassette (ABC) transporters for phospholipids (ABCB4) and bile acids (ABCB11) were associated with this severe form of cholestasis of pregnancy. Methods: For genetic analysis, 52 women with bile acid levels ⩾40 μmol/l (called cases) and 52 unaffected women (called controls) matched for age, parity and geographical residence were studied. Gene variants tagging common ABCB4 and ABCB11 haplotypes were genotyped and haplotype distributions were compared between cases and controls by permutation testing. Results: In contrast with ABCB11 haplotypes, ABCB4 haplotypes differed between the two groups (p = 0.019), showing that the severe form of cholestasis of pregnancy is associated with the ABCB4 gene variants. Specifically, haplotype ABCB4_5 occurred more often in cases, whereas haplotypes ABCB4_3 and ABCB4_7 were more common in controls. These associations were reflected by different frequencies of at-risk alleles of the two tagging polymorphisms (c.711A: odds ratio (OR) 2.27, p = 0.04; deletion intron 5: OR 14.68, p = 0.012). Conclusion: Variants of ABCB4 represent genetic risk factors for the severe form of ICP in Sweden.