Rare variant contribution to cholestatic liver disease in a South Asian population in the United Kingdom.

This study assessed the contribution of five genes previously known to be involved in cholestatic liver disease in British Bangladeshi and Pakistani people. Five genes (ABCB4, ABCB11, ATP8B1, NR1H4, TJP2) were interrogated by exome sequencing data of 5236 volunteers. Included were non-synonymous or loss of function (LoF) variants with a minor allele frequency < 5%. Variants were filtered, and annotated to perform rare variant burden analysis, protein structure, and modelling analysis in-silico. Out of 314 non-synonymous variants, 180 fulfilled the inclusion criteria and were mostly heterozygous unless specified. 90 were novel and of those variants, 22 were considered likely pathogenic and 9 pathogenic. We identified variants in volunteers with gallstone disease (n = 31), intrahepatic cholestasis of pregnancy (ICP, n = 16), cholangiocarcinoma and cirrhosis (n = 2). Fourteen novel LoF variants were identified: 7 frameshift, 5 introduction of premature stop codon and 2 splice acceptor variants. The rare variant burden was significantly increased in ABCB11. Protein modelling demonstrated variants that appeared to likely cause significant structural alterations. This study highlights the significant genetic burden contributing to cholestatic liver disease. Novel likely pathogenic and pathogenic variants were identified addressing the underrepresentation of diverse ancestry groups in genomic research.

GWAS meta-analysis of intrahepatic cholestasis of pregnancy implicates multiple hepatic genes and regulatory elements.

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5-2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis-regulatory elements as contributing mechanisms to ICP susceptibility.

Ursodeoxycholic acid in intrahepatic cholestasis of pregnancy: a systematic review and individual participant data meta-analysis.

BACKGROUND: Ursodeoxycholic acid is commonly used to treat intrahepatic cholestasis of pregnancy, yet its largest trial detected minimal benefit for a composite outcome (stillbirth, preterm birth, and neonatal unit admission). We aimed to examine whether ursodeoxycholic acid affects specific adverse perinatal outcomes. METHODS: In this systematic review and individual participant data meta-analysis, we searched PubMed, Web of Science, Embase, MEDLINE, CINAHL, Global Health, MIDIRS, and Cochrane without language restrictions for relevant articles published between database inception, and Jan 1, 2020, using search terms referencing intrahepatic cholestasis of pregnancy, ursodeoxycholic acid, and perinatal outcomes. Eligible studies had 30 or more study participants and reported on at least one individual with intrahepatic cholestasis of pregnancy and bile acid concentrations of 40 µmol/L or more. We also included two unpublished cohort studies. Individual participant data were collected from the authors of selected studies. The primary outcome was the prevalence of stillbirth, for which we anticipated there would be insufficient data to achieve statistical power. Therefore, we included a composite of stillbirth and preterm birth as a main secondary outcome. A mixed-effects meta-analysis was done using multi-level modelling and adjusting for bile acid concentration, parity, and multifetal pregnancy. Individual participant data analyses were done for all studies and in different subgroups, which were produced by limiting analyses to randomised controlled trials only, singleton pregnancies only, or two-arm studies only. This study is registered with PROSPERO, CRD42019131495. FINDINGS: The authors of the 85 studies fulfilling our inclusion criteria were contacted. Individual participant data from 6974 women in 34 studies were included in the meta-analysis, of whom 4726 (67·8%) took ursodeoxycholic acid. Stillbirth occurred in 35 (0·7%) of 5097 fetuses among women with intrahepatic cholestasis of pregnancy treated with ursodeoxycholic acid and in 12 (0·6%) of 2038 fetuses among women with intrahepatic cholestasis of pregnancy not treated with ursodeoxycholic acid (adjusted odds ratio [aOR] 1·04, 95% CI 0·35-3·07; p=0·95). Ursodeoxycholic acid treatment also had no effect on the prevalence of stillbirth when considering only randomised controlled trials (aOR 0·29, 95% CI 0·04-2·42; p=0·25). Ursodeoxycholic acid treatment had no effect on the prevalence of the composite outcome in all studies (aOR 1·28, 95% CI 0·86-1·91; p=0·22), but was associated with a reduced composite outcome when considering only randomised controlled trials (0·60, 0·39-0·91; p=0·016). INTERPRETATION: Ursodeoxycholic acid treatment had no significant effect on the prevalence of stillbirth in women with intrahepatic cholestasis of pregnancy, but our analysis was probably limited by the low overall event rate. However, when considering only randomised controlled trials, ursodeoxycholic acid was associated with a reduction in stillbirth in combination with preterm birth, providing evidence for the clinical benefit of antenatal ursodeoxycholic acid treatment. FUNDING: Tommy's, the Wellcome Trust, ICP Support, and the National Institute for Health Research.

Whole-genome sequencing of patients with rare diseases in a national health system.

Most patients with rare diseases do not receive a molecular diagnosis and the aetiological variants and causative genes for more than half such disorders remain to be discovered1. Here we used whole-genome sequencing (WGS) in a national health system to streamline diagnosis and to discover unknown aetiological variants in the coding and non-coding regions of the genome. We generated WGS data for 13,037 participants, of whom 9,802 had a rare disease, and provided a genetic diagnosis to 1,138 of the 7,065 extensively phenotyped participants. We identified 95 Mendelian associations between genes and rare diseases, of which 11 have been discovered since 2015 and at least 79 are confirmed to be aetiological. By generating WGS data of UK Biobank participants2, we found that rare alleles can explain the presence of some individuals in the tails of a quantitative trait for red blood cells. Finally, we identified four novel non-coding variants that cause disease through the disruption of transcription of ARPC1B, GATA1, LRBA and MPL. Our study demonstrates a synergy by using WGS for diagnosis and aetiological discovery in routine healthcare.

Ursodeoxycholic acid enriches intestinal bile salt hydrolase-expressing Bacteroidetes in cholestatic pregnancy.

Ursodeoxycholic acid (UDCA) treatment can reduce itch and lower endogenous serum bile acids in intrahepatic cholestasis of pregnancy (ICP). We sought to determine how it could influence the gut environment in ICP to alter enterohepatic signalling. The gut microbiota and bile acid content were determined in faeces from 35 pregnant women (14 with uncomplicated pregnancies and 21 with ICP, 17 receiving UDCA). Faecal bile salt hydrolase activity was measured using a precipitation assay. Serum fibroblast growth factor 19 (FGF19) and 7α-hydroxy-4-cholesten-3-one (C4) concentrations were measured following a standardised diet for 21 hours. Women with a high ratio of Bacteroidetes to Firmicutes were more likely to be treated with UDCA (Fisher's exact test p = 0.0178) than those with a lower ratio. Bile salt hydrolase activity was reduced in women with low Bacteroidetes:Firmicutes. Women taking UDCA had higher faecal lithocholic acid (p < 0.0001), with more unconjugated bile acids than women with untreated ICP or uncomplicated pregnancy. UDCA-treatment increased serum FGF19, and reduced C4 (reflecting lower bile acid synthesis). During ICP, UDCA treatment can be associated with enrichment of the gut microbiota with Bacteroidetes. These demonstrate high bile salt hydrolase activity, which deconjugates bile acids enabling secondary modification to FXR agonists, enhancing enterohepatic feedback via FGF19.

Ursodeoxycholic acid versus placebo in women with intrahepatic cholestasis of pregnancy (PITCHES): a randomised controlled trial.

BACKGROUND: Intrahepatic cholestasis of pregnancy, characterised by maternal pruritus and increased serum bile acid concentrations, is associated with increased rates of stillbirth, preterm birth, and neonatal unit admission. Ursodeoxycholic acid is widely used as a treatment without an adequate evidence base. We aimed to evaluate whether ursodeoxycholic acid reduces adverse perinatal outcomes in women with intrahepatic cholestasis of pregnancy. METHODS: We did a double-blind, multicentre, randomised placebo-controlled trial at 33 hospital maternity units in England and Wales. We recruited women with intrahepatic cholestasis of pregnancy, who were aged 18 years or older and with a gestational age between 20 weeks and 40 weeks and 6 days, with a singleton or twin pregnancy and no known lethal fetal anomaly. Participants were randomly assigned 1:1 to ursodeoxycholic acid or placebo, given as two oral tablets a day at an equivalent dose of 500 mg twice a day. The dose could be increased or decreased at the clinician's discretion, to a maximum of four tablets and a minimum of one tablet a day. We recommended that treatment should be continued from enrolment until the infant's birth. The primary outcome was a composite of perinatal death (in-utero fetal death after randomisation or known neonatal death up to 7 days after birth), preterm delivery (<37 weeks' gestation), or neonatal unit admission for at least 4 h (from birth until hospital discharge). Each infant was counted once within this composite. All analyses were done according to the intention-to-treat principle. The trial was prospectively registered with the ISRCTN registry, number 91918806. FINDINGS: Between Dec 23, 2015, and Aug 7, 2018, 605 women were enrolled and randomly allocated to receive ursodeoxycholic acid (n=305) or placebo (n=300). The primary outcome analysis included 304 women and 322 infants in the ursodeoxycholic acid group, and 300 women and 318 infants in the placebo group (consent to use data was withdrawn for 1 woman and 2 infants). The primary composite outcome occurred in 74 (23%) of 322 infants in the ursodeoxycholic acid group and 85 (27%) of 318 infants in the placebo group (adjusted risk ratio 0·85 [95% CI 0·62-1·15]). Two serious adverse events were reported in the ursodeoxycholic acid group and six serious adverse events were reported in the placebo group; no serious adverse events were regarded as being related to treatment. INTERPRETATION: Treatment with ursodeoxycholic acid does not reduce adverse perinatal outcomes in women with intrahepatic cholestasis of pregnancy. Therefore, its routine use for this condition should be reconsidered. FUNDING: National Institute for Health Research Efficacy and Mechanism Evaluation Programme.

Polymorphisms in Natural Killer Cell Receptor Protein 2D (NKG2D) as a Risk Factor for Cholangiocarcinoma.

BACKGROUND AND AIMS: Understanding of the significant genetic risk factors for Cholangiocarcinoma (CC) remains limited. Polymorphisms in the natural killer cell receptor G2D (NKG2D) gene have been shown to increase risk of CC transformation in patients with Primary Sclerosing Cholangitis (PSC). We present a validation study of NKG2D polymorphisms in CC patients without PSC. METHODS: Seven common Single Nucleotide Polymorphisms (SNPs) of the NKG2D gene were genotyped in 164 non-PSC related CC subjects and 257 controls with HaploView. The two SNPs that were positively identified in the previous Scandinavian study, rs11053781 and rs2617167, were included. RESULTS: The seven genotyped SNPs were not associated with risk of CC. Furthermore, haplotype analysis revealed that there was no evidence to suggest that any haplotype differs in frequency between cases and controls (P > 0.1). CONCLUSION: The common genetic variation in NKG2D does not correlate significantly with sporadic CC risk. This is in contrast to the previous positive findings in the Scandinavian study with PSC-patients. The failure to reproduce the association may reflect an important difference between the pathogenesis of sporadic CC and that of PSC-related CC. Given that genetic susceptibility is likely to be multifaceted and complex, further validation studies that include both sporadic and PSC-related CC are required.

Enhanced Microbial Bile Acid Deconjugation and Impaired Ileal Uptake in Pregnancy Repress Intestinal Regulation of Bile Acid Synthesis.

Pregnancy is associated with progressive hypercholanemia, hypercholesterolemia, and hypertriglyceridemia, which can result in metabolic disease in susceptible women. Gut signals modify hepatic homeostatic pathways, linking intestinal content to metabolic activity. We sought to identify whether enteric endocrine signals contribute to raised serum bile acids observed in human and murine pregnancies, by measuring fibroblast growth factor (FGF) 19/15 protein and mRNA levels, and 7α-hydroxy-4-cholesten-3-one. Terminal ileal farnesoid X receptor (FXR)-mediated gene expression and apical sodium bile acid transporter (ASBT) protein concentration were measured by qPCR and western blotting. Shotgun whole-genome sequencing and ultra-performance liquid chromatography tandem mass spectrometry were used to determine the cecal microbiome and metabonome. Targeted and untargeted pathway analyses were performed to predict the systemic effects of the altered metagenome and metabolite profiles. Dietary CA supplementation was used to determine whether the observed alterations could be overcome by intestinal bile acids functioning as FXR agonists. Human and murine pregnancy were associated with reduced intestinal FXR signaling, with lower FGF19/15 and resultant increased hepatic bile acid synthesis. Terminal ileal ASBT protein was reduced in murine pregnancy. Cecal bile acid conjugation was reduced in pregnancy because of elevated bile salt hydrolase-producing Bacteroidetes. CA supplementation induced intestinal FXR signaling, which was not abrogated by pregnancy, with strikingly similar changes to the microbiota and metabonome as identified in pregnancy. Conclusion: The altered intestinal microbiota of pregnancy enhance bile acid deconjugation, reducing ileal bile acid uptake and lowering FXR induction in enterocytes. This exacerbates the effects mediated by reduced bile acid uptake transporters in pregnancy. Thus, in pregnant women and mice, there is reduced FGF19/15-mediated hepatic repression of hepatic bile acid synthesis, resulting in hypercholanemia.

Ursodeoxycholic acid versus placebo in the treatment of women with intrahepatic cholestasis of pregnancy (ICP) to improve perinatal outcomes: protocol for a randomised controlled trial (PITCHES).

BACKGROUND: Intrahepatic cholestasis of pregnancy (ICP) is the most common liver disorder specific to pregnancy and presents with maternal pruritus, raised concentrations of serum bile acids and abnormal liver function tests. ICP is associated with increased rates of spontaneous and iatrogenic preterm labour, fetal hypoxia, meconium-stained amniotic fluid and intrauterine death. Some clinicians treat ICP with ursodeoxycholic acid (UDCA) to improve maternal pruritus and biochemical abnormalities. However, there are currently no data to support the use of UDCA to improve pregnancy outcome as none of the trials performed to date have been powered to address this question. METHODS: The PITCHES trial is a triple-masked, placebo-controlled randomised trial, to evaluate UDCA versus placebo in women with ICP between 20 + 0 to 40 + 6 weeks' gestation. The primary objective of the trial is to determine if UDCA treatment of women with ICP between 20 + 0 and 40 + 6 weeks' gestation reduces the primary perinatal outcome: a composite of perinatal death (as defined by in utero fetal death after randomisation or known neonatal death up to 7 days) or preterm delivery (less than 37 weeks' gestation) or neonatal unit admission for at least 4 h (from infant delivery until hospital discharge). The secondary objectives of the trial are (1) to investigate the effect of UDCA on other short-term outcomes for both mother and infant and (2) to assess the impact of UDCA on health care resource use, in terms of the total number of nights for mother and infant, together with level of care. DISCUSSION: Current practice in the UK at the time of trial commencement for the treatment of ICP is inconsistent, with some units routinely prescribing UDCA, others prescribing very little and the remainder offering it variably. Our previous pilot trial of UDCA in women with ICP demonstrated that the trial would be feasible, and the research question remains active and unanswered. Results are highly likely to influence clinical practice, through direct management and impact on national and international guidelines. TRIAL REGISTRATION: ISRCTN registry, ID: ISRCTN91918806 . Prospectively registered on 27 August 2015.

An expanded role for heterozygous mutations of ABCB4, ABCB11, ATP8B1, ABCC2 and TJP2 in intrahepatic cholestasis of pregnancy.

Intrahepatic cholestasis of pregnancy (ICP) affects 1/140 UK pregnancies; with pruritus, hepatic impairment and elevated serum bile acids. Severe disease is complicated by spontaneous preterm delivery and stillbirth. Previous studies have reported mutations in hepatocellular transporters (ABCB4, ABCB11). High throughput sequencing in 147 patients was performed in the transporters ABCB4, ABCB11, ATP8B1, ABCC2 and tight junction protein 2 (TJP2). Twenty-six potentially damaging variants were identified with the following predicted protein changes: Twelve ABCB4 mutations - Arg47Gln, Met113Val, Glu161Gly, Thr175Ala, Glu528Glyfs*6, Arg590Gln, Ala601Ser, Glu884Ter, Gly722Ala, Tyr775Met (x2), Trp854Ter. Four potential ABCB11 mutations - Glu297Gly (x3) and a donor splice site mutation (intron 19). Five potential ATP8B1 mutations - Asn45Thr (x3), and two others, Glu114Gln and Lys203Glu. Two ABCC2 mutations - Glu1352Ala and a duplication (exons 24 and 25). Three potential mutations were identified in TJP2; Thr62Met (x2) and Thr626Ser. No patient harboured more than one mutation. All were heterozygous. An additional 545 cases were screened for the potential recurrent mutations of ATP8B1 (Asn45Thr) and TJP2 (Thr62Met) identifying three further occurrences of Asn45Thr. This study has expanded known mutations in ABCB4 and ABCB11 and identified roles in ICP for mutations in ATP8B1 and ABCC2. Possible novel mutations in TJP2 were also discovered.

Bile acids and gestation.

There are numerous profound maternal physiological changes that occur from conception onwards and adapt throughout gestation in order to support a healthy pregnancy. By the time of late gestation, when circulating pregnancy hormones are at their highest concentrations, maternal adaptations include relative hyperlipidemia, hypercholanemia and insulin resistance. Bile acids have now been established as key regulators of metabolism, and their role in gestational changes in metabolism is becoming apparent. Bile acid homeostasis is tightly regulated by the nuclear receptor FXR, which has been shown to have reduced activity during pregnancy. This review focuses on the gestational alterations in bile acid homeostasis that occur in normal pregnancy, which in some women can become pathological, leading to the development of intrahepatic cholestasis of pregnancy. As well as their important role in maternal metabolic health, we will review bile acid metabolism in the feto-placental unit.

Pregnancy and bile acid disorders.

During pregnancy, extensive adaptations in maternal metabolic and immunological physiology occur. Consequently, preexisting disease may be exacerbated or attenuated, and new disease susceptibility may be unmasked. Cholestatic diseases, characterized by a supraphysiological raise in bile acid levels, require careful monitoring during pregnancy. This review describes the latest advances in the knowledge of intrahepatic cholestasis of pregnancy (ICP), the most common bile acid disorder specific to pregnancy, with a focus on the disease etiology and potential mechanisms of ICP-associated adverse pregnancy outcomes, including fetal demise. The course of preexisting cholestatic conditions in pregnancy is considered, including primary sclerosing cholangitis, primary biliary cholangitis, biliary atresia, and Alagille syndrome. The currently accepted treatments for cholestasis in pregnancy and promising new therapeutics for the condition are described.

Characterizing Factors Associated With Differences in FGF19 Blood Levels and Synthesis in Patients With Primary Bile Acid Diarrhea.

OBJECTIVES: Chronic diarrhea caused by primary bile acid diarrhea (PBAD) is a common condition. We have previously shown PBAD is associated with low fasting serum levels of the ileal hormone, fibroblast growth factor 19 (FGF19). FGF19 is a negative regulator of hepatic bile acid synthesis and is stimulated by farnesoid X receptor agonists, which produce symptomatic improvement in PBAD. We aimed to assess possible causes for low serum FGF19 in patients with PBAD. METHODS: Patients with PBAD, defined by reduced (75)Se-labelled homocholic acid taurine (SeHCAT) retention, and idiopathic diarrhea controls had measurements of fasting lipids and fasting/post-prandial FGF19 serum profiles. Specific functional variants in candidate genes were investigated in exploratory studies. In further groups, basal and bile acid-stimulated transcript expression was determined in ileal biopsies and explant cultures by quantitative PCR. RESULTS: FGF19 profiles in PBAD patients included low fasting and meal-stimulated responses, which were both strongly correlated with SeHCAT. A subgroup of 30% of PBAD patients had fasting hypertriglyceridemia and higher FGF19. No clear significant differences were found for any genetic variant but there were borderline associations with FGFR4 and KLB. SeHCAT retention significantly correlated with the basal ileal transcript expression of FGF19 (rs=0.59, P=0.03) and apical sodium-dependent bile acid transporter (ASBT) (rs=0.49, P=0.04), and also with the degree of stimulation by chenodeoxycholic acid at 6 h for transcripts of FGF19 (median 184-fold, rs=0.50, P=0.02) and ileal bile acid binding protein (IBABP) (median 2.2-fold, rs=0.47, P=0.04). Median stimulation of FGF19 was lower in patients with SeHCAT retention <10% (P=0.01). CONCLUSIONS: These studies demonstrate a complex, multifactorial etiology of PBAD, including impairments in ileal FGF19 expression and responsiveness.

The pathophysiology of intrahepatic cholestasis of pregnancy.

A number of liver disorders are specific to pregnancy. Amongst these, intrahepatic cholestasis of pregnancy (ICP), also known as obstetric cholestasis (OC), is the commonest, affecting approximately 1 in 140 UK pregnancies. Patients commonly present in the third trimester with severe pruritus and deranged serum liver tests; bile acids are elevated, in severe cases >40 µmol/L. Although the disease is considered relatively benign for the mother, increased rates of adverse fetal outcomes, including stillbirth, are associated with ICP. As our knowledge of the mechanisms underlying bile acid homeostasis has advanced in the last 15 years our understanding of ICP has grown, in particular with respect to genetic influences on susceptibility to the disease, the role of reproductive hormones and their metabolites and the possible identity of the pruritic agents. In this review, we will describe recent advances in the understanding of this condition with a particular emphasis on how aspects of genetic and reproductive hormone involvement in pathophysiology have been elucidated. We also review recent developments regarding our knowledge of placental and fetal pathophysiology and the long-term health consequences for the mother and child.

Prognostic and mechanistic potential of progesterone sulfates in intrahepatic cholestasis of pregnancy and pruritus gravidarum.

UNLABELLED: A challenge in obstetrics is to distinguish pathological symptoms from those associated with normal changes of pregnancy, typified by the need to differentiate whether gestational pruritus of the skin is an early symptom of intrahepatic cholestasis of pregnancy (ICP) or due to benign pruritus gravidarum. ICP is characterized by raised serum bile acids and complicated by spontaneous preterm labor and stillbirth. A biomarker for ICP would be invaluable for early diagnosis and treatment and to enable its differentiation from other maternal diseases. Three progesterone sulfate compounds, whose concentrations have not previously been studied, were newly synthesized and assayed in the serum of three groups of ICP patients and found to be significantly higher in ICP at 9-15 weeks of gestation and prior to symptom onset (group 1 cases/samples: ICP n = 35/80, uncomplicated pregnancy = 29/100), demonstrating that all three progesterone sulfates are prognostic for ICP. Concentrations of progesterone sulfates were associated with itch severity and, in combination with autotaxin, distinguished pregnant women with itch that would subsequently develop ICP from pruritus gravidarum (group 2: ICP n = 41, pruritus gravidarum n = 14). In a third group of first-trimester samples all progesterone sulfates were significantly elevated in serum from low-risk asymptomatic women who subsequently developed ICP (ICP/uncomplicated pregnancy n = 54/51). Finally, we show mechanistically that progesterone sulfates mediate itch by evoking a Tgr5-dependent scratch response in mice. CONCLUSION: Our discovery that sulfated progesterone metabolites are a prognostic indicator for ICP will help predict onset of ICP and distinguish it from benign pruritus gravidarum, enabling targeted obstetric care to a high-risk population. Delineation of a progesterone sulfate-TGR5 pruritus axis identifies a therapeutic target for itch management in ICP.

Autotaxin activity has a high accuracy to diagnose intrahepatic cholestasis of pregnancy.

BACKGROUND & AIMS: Intrahepatic cholestasis of pregnancy (ICP) is defined by pruritus, elevated total fasting serum bile salts (TBS) and transaminases, and an increased risk of adverse fetal outcome. An accurate diagnostic marker is needed. Increased serum autotaxin correlates with cholestasis-associated pruritus. We aimed at unraveling the diagnostic accuracy of autotaxin in ICP. METHODS: Serum samples and placental tissue were collected from 44 women with uncomplicated pregnancies and 105 with pruritus and/or elevated serum transaminases. Autotaxin serum levels were quantified enzymatically and by Western blotting, autotaxin gene expression by quantitative PCR. RESULTS: Serum autotaxin was increased in ICP (mean ± SD: 43.5 ± 18.2 nmol ml(-1)min(-1), n=55, p<0.0001) compared to other pruritic disorders of pregnancy (16.8 ± 6.7 nmol ml(-1)min(-1), n=33), pre-eclampsia complicated by HELLP-syndrome (16.8 ± 8.9 nmol ml(-1)min(-1), n=17), and pregnant controls (19.6 ± 5.7 nmol ml(-1)min(-1), n=44). Longitudinal analysis during pregnancy revealed a marked rise in serum autotaxin with onset of ICP-related pruritus. Serum autotaxin was increased in women taking oral contraceptives. Increased serum autotaxin during ICP was not associated with increased autotaxin mRNA in placenta. With a cut-off value of 27.0 nmol ml(-1)min(-1), autotaxin had an excellent sensitivity and specificity in distinguishing ICP from other pruritic disorders or pre-eclampsia/HELLP-syndrome. Serum autotaxin displayed no circadian rhythm and was not influenced by food intake. CONCLUSIONS: Increased serum autotaxin activity represents a highly sensitive, specific and robust diagnostic marker of ICP, distinguishing ICP from other pruritic disorders of pregnancy and pregnancy-related liver diseases. Pregnancy and oral contraception increase serum autotaxin to a much lesser extent than ICP.

The metabolic profile of intrahepatic cholestasis of pregnancy is associated with impaired glucose tolerance, dyslipidemia, and increased fetal growth.

OBJECTIVE: Quantification of changes in glucose and lipid concentrations in women with intrahepatic cholestasis of pregnancy (ICP) and uncomplicated pregnancy and study of their influence on fetal growth. RESEARCH DESIGN AND METHODS: A prospective study comparing metabolic outcomes in cholestastic and uncomplicated singleton pregnancies was undertaken at two university hospitals in the U.K. and U.S. from 2011-2014. A total of 26 women with ICP and 27 control pregnancies with no prior history of gestational diabetes mellitus were recruited from outpatient antenatal services and followed until delivery. Alterations in glucose, incretins, cholesterol, and triglycerides were studied using a continuous glucose monitoring (CGM) system and/or a standard glucose tolerance test (GTT) in conjunction with GLP-1 and a fasting lipid profile. Fetal growth was quantified using adjusted birth centiles. RESULTS: Maternal blood glucose concentrations were significantly increased in ICP during ambulatory CGM (P < 0.005) and following a GTT (P < 0.005). ICP is characterized by increased fasting triglycerides (P < 0.005) and reduced HDL cholesterol (P < 0.005), similar to changes observed in metabolic syndrome. The offspring of mothers with ICP had significantly larger customized birth weight centiles, adjusted for ethnicity, sex, and gestational age (P < 0.005). CONCLUSIONS: ICP is associated with impaired glucose tolerance, dyslipidemia, and increased fetal growth. These findings may have implications regarding the future health of affected offspring.

Molecular mechanistic explanation for the spectrum of cholestatic disease caused by the S320F variant of ABCB4.

UNLABELLED: ABCB4 flops phosphatidylcholine into the bile canaliculus to protect the biliary tree from the detergent activity of bile salts. Homozygous-null ABCB4 mutations cause the childhood liver disease, progressive familial intrahepatic cholestasis, but cause and effect is less clear, with many missense mutations linked to less severe cholestatic diseases. ABCB4(S320F), in particular, is described in 13 patients, including in heterozygosity with ABCB4(A286V), ABCB4(A953D), and null mutants, whose symptoms cover the spectrum of cholestatic disease. We sought to define the impact of these mutations on the floppase, explain the link with multiple conditions at the molecular level, and investigate the potential for reversal. ABCB4(S320F), ABCB4(A286V), and ABCB4(A953D) expression was engineered in naïve cultured cells. Floppase expression, localization, and activity were measured by western blot, confocal microscopy, and lipid transport assays, respectively. ABCB4(S320F) was fully active for floppase activity but expression at the plasma membrane was reduced to 50%. ABCB4(A286V) expressed and trafficked efficiently but could not flop lipid, and ABCB4(A953D) expressed poorly and was impaired in floppase activity. Proteasome inhibition stabilized nascent ABCB4(S320F) and ABCB4(A953D) but did not improve plasma membrane localization. Cyclosporin-A improved plasma membrane localization of both ABCB4(S320F) and ABCB4(A953D), but inhibited floppase activity. CONCLUSION: The level of ABCB4 functionality correlates with, and is the primary determinant of, cholestatic disease severity in these patients. ABCB4(S320F) homozygosity, with half the normal level of ABCB4, is the tipping point between more benign and potentially fatal cholestasis and makes these patients more acutely sensitive to environmental effects. Cyclosporin-A increased expression of ABCB4(S320F) and ABCB4(A953D), suggesting that chemical chaperones could be exploited for therapeutic benefit to usher in a new era of personalized medicine for patients with ABCB4-dependent cholestatic disease.

A comprehensive analysis of common genetic variation around six candidate loci for intrahepatic cholestasis of pregnancy.

OBJECTIVES: Intrahepatic cholestasis of pregnancy (ICP) has a complex etiology with a significant genetic component. Heterozygous mutations of canalicular transporters occur in a subset of ICP cases and a population susceptibility allele (p.444A) has been identified in ABCB11. We sought to expand our knowledge of the detailed genetic contribution to ICP by investigation of common variation around candidate loci with biological plausibility for a role in ICP (ABCB4, ABCB11, ABCC2, ATP8B1, NR1H4, and FGF19). METHODS: ICP patients (n=563) of white western European origin and controls (n=642) were analyzed in a case-control design. Single-nucleotide polymorphism (SNP) markers (n=83) were selected from the HapMap data set (Tagger, Haploview 4.1 (build 22)). Genotyping was performed by allelic discrimination assay on a robotic platform. Following quality control, SNP data were analyzed by Armitage's trend test. RESULTS: Cochran-Armitage trend testing identified six SNPs in ABCB11 together with six SNPs in ABCB4 that showed significant evidence of association. The minimum Bonferroni corrected P value for trend testing ABCB11 was 5.81×10(-4) (rs3815676) and for ABCB4 it was 4.6×10(-7)(rs2109505). Conditional analysis of the two clusters of association signals suggested a single signal in ABCB4 but evidence for two independent signals in ABCB11. To confirm these findings, a second study was performed in a further 227 cases, which confirmed and strengthened the original findings. CONCLUSIONS: Our analysis of a large cohort of ICP cases has identified a key role for common variation around the ABCB4 and ABCB11 loci, identified the core associations, and expanded our knowledge of ICP susceptibility.

Potent stimulation of fibroblast growth factor 19 expression in the human ileum by bile acids.

Fibroblast growth factor 19 (FGF19) is proposed to be a negative feedback regulator of hepatic bile acid (BA) synthesis. We aimed to clarify the distribution of FGF19 expression in human intestine and to investigate induction in a novel explant system. Ileal and colonic mucosal biopsies were obtained at endoscopy and analyzed for FGF19 transcript expression. Primary explants were incubated with physiological concentrations of various BA for up to 6 h, and expression of FGF19 and other genes was determined. FGF19 transcripts were detected in ileum but were unquantifiable in colon. No loss of FGF19 mRNA occurred as a consequence of the explant system. Ileal FGF19 transcript expression was induced 350-fold by 50 µM chenodeoxycholate (CDCA, n = 24, P < 0.0001) and 161-fold by 50 µM glycochenodeoxycholate (GCDCA, n = 12, P = 0.0005). The responses of other genes to CDCA or GCDCA (50 µM) were smaller: median increases of ileal bile acid binding protein, organic solute transporter-α and -ß, and short heterodimer partner were 2.4- to 4.0-fold; apical membrane sodium bile acid transporter and farnesoid X receptor (FXR) showed little change. The EC50 for FGF19 transcript induction by CDCA was 20 µM. FGF19 protein concentrations were significantly higher in the culture fluid from BA-stimulated explants. FGF19 induction with cholate was 81% of that found with CDCA, but deoxycholate (40%) and lithocholate (4%) were significantly less potent. The synthetic FXR agonist obeticholic acid was much more potent than CDCA with a 70-fold FGF19 stimulation at 1 µM. We concluded that FGF19 expression in human ileum is very highly responsive to BA. Changes in FGF19 induction are a potential mechanism involved in disorders of BA homeostasis.