The role of genetic mutations in intrahepatic cholestasis of pregnancy

Obstetric cholestasis and its impact on the maternal outcome

AIM

To evaluate the association of GDM and pre-eclampsia in women with obstetric cholestasis.

MATERIALS AND METHODS

Pregnant women with > 28 weeks gestation attending ANC, OPD and labor room of J.N.M.C.H, AMU, Aligarh UP (India) from 2020 to 2022 were included in the study after taking informed consent and ethical approval from the Institute. Women were divided into 2 groups, i.e. group 1 having 200 women with IHCP and group 2 having 200 healthy pregnant women; both the groups were followed up for the development of GDM and pre-eclampsia.

RESULTS

A statistically significant association was observed between IHCP and development of GDM [26.5% and odds ratio (OR) 1.64] and pre-eclampsia (17% and OR: 1.95) (p < 0.05), an also GDM and pre-eclampsia were found to be significantly associated with the severity of cholestasis (p < 0.05). Thus, on calculating OR, we found higher odds of developing GDM and pre-eclampsia in IHCP group with raised serum bile acid levels, maximum at 60 μmol/L level as compared to 10-40 μmol/L (GDM: OR: 8.647 and pre-eclampsia: OR: 6.303). Induction and cesarean rates were significantly higher in IHCP group (p < 0.05).

CONCLUSION

Our study concludes significant association of IHCP with GDM and pre-eclampsia as all three shares common pathogenetic pathways and greater risk of development at higher serum bile acid levels.

Genetic issues in ICP

Intrahepatic cholestasis of pregnancy (ICP) is the commonest gestational liver disorder with variable global incidence. Genetic susceptibility, combined with hormonal and environmental influences, contributes to ICP aetiology. Adverse pregnancy outcomes linked to elevated serum bile acids highlight the importance of comprehensive risk assessment. ABCB4 and ABCB11 gene variants play a significant role in about 20% of severe ICP cases. Several other genes including ATP8B1, NR1H4, ABCC2, TJP2, SERPINA1, GCKR and HNF4A have also been implicated with ICP. Additionally, ABCB4 variants elevate the risk of drug-induced intrahepatic cholestasis, gallstone disease, gallbladder and bile duct carcinoma, liver cirrhosis and abnormal liver function tests. Genetic variations, both rare and common, intricately contribute to ICP susceptibility. Leveraging genetic insights holds promise for personalised management and intervention strategies. Further research is needed to elucidate variant-specific phenotypic expressions and therapeutic implications, advancing precision medicine in ICP management.

Intrahepatic cholestasis of pregnancy and theory of inheritance of the disease. Literature review

Intrahepatic cholestasis during pregnancy is associated with a higher risk of prenatal and maternal complications. There are several new publications and guidelines on the detection and thresholds of intrahepatic cholestasis during pregnancy. However, the genetic background of this disease has rarely been investigated. This is a comprehensive review of the roles of genes in intrahepatic cholestasis during pregnancy.

Revisited role of the placenta in bile acid homeostasis

To date, the discussion concerning bile acids (BAs) during gestation is almost exclusively linked to pregnancy complications such as intrahepatic cholestasis of pregnancy (ICP) when maternal serum BA levels reach very high concentrations (>100 μM). Generally, the placenta is believed to serve as a protective barrier avoiding exposure of the growing fetus to excessive amounts of maternal BAs that might cause detrimental effects (e.g., intrauterine growth restriction and/or increased vulnerability to metabolic diseases). However, little is known about the precise role of the placenta in BA biosynthesis, transport, and metabolism in healthy pregnancies when serum BAs are at physiological levels (i.e., low maternal and high fetal BA concentrations). It is well known that primary BAs are synthesized from cholesterol in the liver and are later modified to secondary BA species by colonic bacteria. Besides the liver, BA synthesis in extrahepatic sites such as the brain elicits neuroprotective actions through inhibition of apoptosis as well as oxidative and endoplasmic reticulum stress. Even though historically BAs were thought to be only "detergent molecules" required for intestinal absorption of dietary fats, they are nowadays acknowledged as full signaling molecules. They modulate a myriad of signaling pathways with functional consequences on essential processes such as gluconeogenesis -one of the principal energy sources of the fetus- and cellular proliferation. The current manuscript discusses the potential multipotent roles of physiologically circulating BAs on developmental processes during gestation and provides a novel perspective in terms of the importance of the placenta as a previously unknown source of BAs. Since the principle "not too much, not too little" applicable to other signaling molecules may be also true for BAs, the risks associated with fetal exposure to excessive levels of BAs are discussed.

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.

Whole-exome sequencing expands the roles of novel mutations of organic anion transporting polypeptide, ATP-binding cassette transporter, and receptor genes in intrahepatic cholestasis of pregnancy

Background: Intrahepatic cholestasis of pregnancy (ICP) is associated with a high incidence of fetal morbidity and mortality. Therefore, revealing the mechanisms involved in ICP and its association with fetal complications is very important.

Methods: Here, we used a whole-exome sequencing (WES) approach to detect novel mutations of organic anion transporting polypeptide (OTAP) genes, ATP-binding cassette transporter (ABC) genes, and receptor genes associated with ICP in 249 individuals and 1,029 local control individuals. Two available tools, SIFT and PolyPhen-2, were used to predict protein damage. Protein structuremodeling and comparison between the reference and modified protein structures were conducted by SWISS-MODEL and Chimera 1.14rc software, respectively.

Results: A total of 5,583 mutations were identified in 82 genes related to bile acid transporters and receptors, of which 62 were novel mutations. These novel mutations were absent in the 1,029 control individuals and three databases, including the 1,000 Genome Project (1000G_ALL), Exome Aggregation Consortium (ExAC), and Single-Nucleotide Polymorphism Database (dbSNP). We classified the 62 novel loci into two groups (damaging and probably damaging) according to the results of SIFT and PolyPhen-2. Out of the 62 novel mutations, 24 were detected in the damaging group. Of these, five novel possibly pathogenic variants were identified that were located in known functional genes, including ABCB4 (Ile377Asn), ABCB11 (Ala588Pro), ABCC2 (Ile681Lys and Met688Thr), and NR1H4 (Tyr149Ter). Moreover, compared to the wild-type protein structure, ABCC2 Ile681Lys and Met688Thr protein structures showed a slight change in the chemical bond lengths of ATP-ligand binding amino acid side chains. The combined 32 clinical data points indicate that the mutation group had a significantly (p = 0.04) lower level of Cl ions than the wild-type group. Particularly, patients with the 24 novel mutations had higher average values of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total bile acids (TBA), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) than patients with the 38 novel mutations in the probably damaging group and the local control individuals.

Conclusion: The present study provides new insights into the genetic architecture of ICP involving these novel mutations.

Deep Learning Algorithm-Based Magnetic Resonance Imaging Feature-Guided Serum Bile Acid Profile and Perinatal Outcomes in Intrahepatic Cholestasis of Pregnancy

This study was aimed to explore magnetic resonance imaging (MRI) based on deep learning belief network model in evaluating serum bile acid profile and adverse perinatal outcomes of intrahepatic cholestasis of pregnancy (ICP) patients. Fifty ICP pregnant women diagnosed in hospital were selected as the experimental group, 50 healthy pregnant women as the blank group, and 50 patients with cholelithiasis as the gallstone group. Deep learning belief network (DLBN) was built by stacking multiple restricted Boltzmann machines, which was compared with the recognition rate of convolutional neural network (CNN) and support vector machine (SVM), to determine the error rate of different recognition methods on the test set. It was found that the error rate of deep learning belief network (7.68%) was substantially lower than that of CNN (21.34%) and SVM (22.41%) (P < 0.05). The levels of glycoursodeoxycholic acid (GUDCA), glycochenodeoxycholic acid (GCDCA), and glycocholic acid (GCA) in the experimental group were dramatically superior to those in the blank group (P < 0.05). Both the experimental group and the blank group had notable clustering of serum bile acid profile, and the experimental group and the gallstone group could be better distinguished. In addition, the incidence of amniotic fluid contamination, asphyxia, and premature perinatal infants in the experimental group was dramatically superior to that in the blank group (P < 0.05). The deep learning confidence model had a low error rate, which can effectively extract the features of liver MRI images. In summary, the serum characteristic bile acid profiles of ICP were glycoursodeoxycholic acid, glycochenodeoxycholic acid, and glycocholic acid, which had a positive effect on clinical diagnosis. The toxic effects of high concentrations of serum bile acids were the main cause of adverse perinatal outcomes and sudden death.

Intrahepatic cholestasis of pregnancy - Time to redefine the reference range of total serum bile acids: A cross-sectional study

Objective

To establish pregnancy‐specific reference ranges for fasting and postprandial total serum bile acid (TSBA) concentrations.

Design

Cross‐sectional study.

Setting

Tertiary‐care university hospital.

Population

Healthy pregnant women at term admitted to the Obstetrics Department over a period of 1 year. Exclusion criteria were an established diagnosis of intrahepatic cholestasis of pregnancy (ICP) or any coexisting condition of increased risk for ICP.

Methods

Both fasting (after 8–14 h of fasting) and postprandial (2 h after meal) TSBA concentrations were measured in 612 women (with 528 fasting samples and 377 postprandial samples) by automated enzymatic spectrophotometric assay.

Main outcome measures

Fasting and postprandial TSBA concentrations in 612 women.

Results

Reference intervals of 4.4–14.1 μmol/L for fasting TSBA and 4.7–20.2 μmol/L for postprandial TSBA were established. The postprandial values were significantly higher than the fasting values, with a median increase of 1.0 μmol/L (p < 0.0001). A correlation between fasting TSBA concentrations and postprandial concentrations was found, as well as correlations with fetal sex, parity and assisted reproductive technologies. A seasonal pattern was noticed for both fasting and postprandial TSBA, with the highest values measured in the winter season (p < 0.01 and 0.02, respectively)

Conclusions

Normal pregnancy is associated with mild hypercholanaemia, and therefore a higher threshold should be considered for the diagnosis of ICP. We suggest using the upper reference limits observed in our healthy pregnant population (14 μmol/L for fasting TSBA and 20 μmol/L for postprandial TSBA). As the fasting measurement is more specific for the diagnosis, and the postprandial measurement is essential for the assessment of severity, it is recommended to measure both values rather than use random sampling.

Tweetable abstract

Normal pregnancy is associated with mild hypercholanaemia, a higher threshold should be considered for the diagnosis of ICP.

Normal pregnancy is associated with mild hypercholanaemia, a higher threshold should be considered for the diagnosis of ICP.

Linked article: This article is commented on by Ovadia et al., pp. 1897–1898. in this issue. To view this minicommentary visit https://doi.org/10.1111/1471‐0528.17171

Antiphospholipid Antibodies Increase the Risk of Fetal Growth Restriction: A Systematic Meta-Analysis

OBJECTIVE

Antiphospholipid syndrome (APS) is a chronic autoimmune disease with a high prevalence in females. Published data have identified pregnant women with APS may suffer from recurrent miscarriage, fetal death. However, the association between antiphospholipid antibody (aPL) and fetal growth restriction (FGR) remains controversial. This study aims to systematically review the literature on population-based studies investigating an association between aPL and FGR.

METHODS

The literature was searched on 1 November, 2021, using Ovid MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL), following the MOOSE checklist. Study inclusion criteria focused on peer-reviewed published articles that reported an association between aPL and FGR. Quality assessment was performed based on the Newcastle-Ottawa scale. The between-study heterogeneity was assessed by the Q test. Publication bias was assessed by funnel plots.

RESULTS

Twenty-two studies (with 11745 pregnant women) were included in the final analysis. Pooled odds ratio for association of aPL, anticardiolipin antibodies (ACA), anti-beta2 glycoprotein 1 antibodies (β2GP1), and FGR was 1.26 (95%CI 1.12, 1.40), 2.25 (95%CI 1.55, 2.94), and 1.31 (95% CI 1.12, 1.49), respectively. Lupus anticoagulant (LA) did not increase the chance of FGR (OR 0.82, 95%CI 0.54, 1.10).

CONCLUSIONS

Our meta-analysis showed that aPL increased the risk of FGR. The risk of FGR varies with the aPL types. ACA and β2GP1 are strongly associated with FGR. There are currently insufficient data to support a significant relationship between LA and FGR.

Increased serum delta neutrophil index levels are associated with intrahepatic cholestasis of pregnancy

OBJECTIVE

This study aims to compare the maternal serum delta neutrophil index (DNI) levels in intrahepatic cholestasis of pregnancy (ICP) and healthy pregnancies.

METHODS

This study consisted of a group of patients (n = 40) diagnosed with isolated ICP who gave birth in our hospital and a control group (n = 60) between December 1, 2015, and June 30, 2018. The diagnosis of ICP was made based on pruritus and elevated fasting serum bile acids and liver enzymes. Laboratory tests of both groups in the hospitalization process were retrospectively examined. Maternal and neonatal characteristics, pregnancy outcomes, and DNI values of the two groups were compared. Statistical analyses were performed using SPSS version 20.

RESULTS

Mean maternal serum DNI levels were significantly higher in women with ICP than in the control group (0.49 ± 4.8 vs -3.99 ± 3.02, p = <0.01). Receiver operating characteristic (ROC) curve analysis was used to define the DNI value where ICP can be best predicted.

CONCLUSION

DNI, a new inflammatory marker, was found to be higher in women with ICP than in normal pregnancies.

Molecular Pathogenesis of Intrahepatic Cholestasis of Pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease. The maternal symptoms are characterized by skin pruritus and elevated bile acids, causing several adverse outcomes for fetuses, including an increased risk of preterm birth, meconium-stained amniotic fluid, neonatal depression, respiratory distress syndrome, and stillbirth. Genetic, hormonal, immunological, and environmental factors contribute to the pathogenesis of ICP, and the estrogen-bile acid axis is thought to play a dominant role. The advances in the past 10 years uncover more details of this axis. Moreover, dysregulation of extracellular matrix and oxygen supply, organelle dysfunction, and epigenetic changes are also found to cause ICP, illuminating more potential drug targets for interfering with. Here, we summarize the molecular pathogenesis of ICP with an emphasis on the advancement in the past 10 years, aiming to give an updated full view of this field.