Microsatellite marker association at chromosome region 2p13 in Finnish patients with preeclampsia and obstetric cholestasis suggests a common risk locus

The genetic risk factors for pregnancy-induced hypertension: Evidence from genetic polymorphisms

Pregnancy-induced hypertension (PIH) is a multifactorial and severe pregnancy complication including preeclampsia/eclampsia, gestational hypertension, chronic (pre-existing) hypertension, and preeclampsia/eclampsia variants superimposed on chronic hypertension. PIH-induced maternal mortality accounts for approximately 9% of all maternal deaths over the world. A large number of case-control studies have established the importance of various genetic factors in the occurrence and development of PIH. In this narrative review, we summarized the genetic risk factors involved in the renin-angiotensin system, endothelin system, inflammatory factors, oxidative stress, and other functional networks, with the aim of sorting out the genetic factors that may play a potential role in PIH and providing new ideas to elucidate the pathogenesis of PIH.

Intrahepatic cholestasis of pregnancy: risk factors for severe disease

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-associated hepatic disorder characterized by pruritus in the setting of elevated serum bile acids (BA). Risk factors for the disease include preexisting hepatobiliary disease, personal or family history of ICP, and advanced maternal age. Recent data suggests that patients with severe ICP (BA ≥100 μmol/L) have a higher risk of adverse pregnancy outcomes including stillbirth.

MATERIAL AND METHODS

This was a retrospective cohort study of patients diagnosed with ICP between 2012 and 2019 at a tertiary referral center. ICP was defined as symptomatic pruritus combined with serum BA >10 μmol/L. Maternal characteristics and outcomes were abstracted from electronic medical records. Baseline characteristics were compared between patients with mild (BA <40 μmol/L), moderate (BA 40-99 μmol/L) and severe (BA ≥100 μmol/L) ICP. Obstetrics and neonatal outcomes for patients in each category were then analyzed. Shapiro-Wilk test was used to test for normality for continuous variables, and ANOVA, Kruskal-Wallis, Chi-squared or Fisher's exact tests were used as appropriate. A p-value <.05 was considered statistically significant.

RESULTS

438 patients were included in the analysis. Individuals with pregestational diabetes (p < .01), history of ICP (p < .01), prior cholecystectomy (p < .01), and tobacco use (p < .05) were more likely to have severe disease. When compared to individuals with moderate and mild disease, individuals with severe disease were more likely to be diagnosed earlier (29w1d vs 34w1d vs 34w1d, p < .05), have gestational diabetes (50% vs 6% vs 13%, p < .01), hypertensive disorders of pregnancy (42% vs 10% vs 15%, p = .02), and abnormal aspartate aminotransferase (91% vs 65% vs 27%, p < .01) and alanine aminotransferase levels (91% vs 60% vs 26%, p < .01). There were no differences in preterm labor, meconium-stained amniotic fluid, or neonatal respiratory distress syndrome and no stillbirths in this cohort.

CONCLUSIONS

In patients with ICP, those with pregestational diabetes, history of ICP, prior cholecystectomy, and tobacco use are more likely to develop severe disease. Given the adverse outcomes associated with severe disease, serial BA measurements to monitor for development of severe disease may be warranted in this population.

Intrahepatic cholestasis of pregnancy as a risk factor for preeclampsia

PURPOSE

Intrahepatic cholestasis of pregnancy and preeclampsia are two major pregnancy complications. We aimed to investigate the association between intrahepatic cholestasis of pregnancy (ICP) and preeclampsia.

METHODS

Single-center retrospective study. Study group included 180 women (162 singletons and 18 twin gestations) who were diagnosed with ICP based on clinical presentation, elevated liver enzymes and bile acids. The reference group included 1618 women (1507 singletons and 111 twin gestations) who delivered during the study period, and were matched according to age, gravidity, parity and singleton or twin gestation.

RESULTS

The incidence of ICP was 0.36%. The incidence of preeclampsia was higher in women with ICP compared to reference group (7.78% vs 2.41%, aOR, 3.74 95% CI 12.0-7.02, p < 0.0001), for either without-(3.89% vs 1.61%, aOR 2.83, 95% CI 1.23-6.5, p = 0.145) or with severe features (3.89% vs 0.80%, aOR 5.17 95% CI 2.14-12.50, p = 0.0003). For both singleton and twin pregnancies, overall preeclampsia rates were higher in the ICP group (5.56% vs 2.19%, aOR 2.91 95% CI 1.39-6.07 p = 0.0045; and 27.78% vs 5.41%, aOR 10.9 95% CI 2.16-47.19, p = 0.0033, respectively). Earlier diagnosis of ICP was associated with higher incidence of preeclampsia (31.1 ± 3.8 vs 34.86 ± 6.2 gestational weeks, p = 0.0259). The average time between ICP diagnosis and to the onset of preeclampsia was 29.7 ± 24 days.

CONCLUSION

ICP is associated with an increased risk for preeclampsia. We suggest intensified follow-up for preeclampsia in women with ICP, especially among those with early ICP presentation and twins' gestations.

Genetic Approaches in Preeclampsia

Preeclampsia (PE) is a serious hypertensive disorder that affects up to 8% of all pregnancies annually. An established risk factor for PE is family history, clearly demonstrating an underlying genetic component to the disorder. To date, numerous genetic studies, using both the candidate gene and genome-wide approach, have been undertaken to tease out the genetic basis of PE and understand its origins. Such studies have identified some promising candidate genes such as STOX1 and ACVR2A. Nevertheless, researchers face ongoing challenges of replicating these genetic associations in different populations and performing the functional validation of identified genetic variants to determine their causality in the disorder. This chapter will review the genetic approaches used in the study of PE, discuss their limitations and possible confounders, and describe current strategies.

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.

Perinatal outcomes with intrahepatic cholestasis of pregnancy in twin pregnancies

OBJECTIVE

To describe perinatal outcomes of twin pregnancies complicated by intrahepatic cholestasis of pregnancy (ICP).

METHODS

We conducted a retrospective cohort study of women delivered at a large tertiary obstetric center in Shanghai, China from January 2006 to May 2014. Delivery data were abstracted from medical records of all twin gestations delivered at the hospital.

RESULTS

A total of 129/1922(6.7%) twin and 1190/92 273 singleton (1.3%) pregnancies were complicated by ICP. An increased risk of stillbirth among twin pregnancies was observed (3.9% and 0.8% in the ICP and non-ICP groups, respectively; aOR 5.75, 95% CI 2.00-16.6). Stillbirths with ICP and twins occurred between 33 and 35 weeks gestation compared to 36-38 weeks gestation among singletons. ICP in twins was also associated with an increased risk of preterm birth (<37 weeks) with an aOR of 4.17 (95% CI 2.47-7.04) and an aOR of 1.89 (95% CI 1.26-2.85) for delivery <35 weeks. Twin pregnancies complicated by ICP also had increased meconium staining of amniotic fluid and lower birth weight.

CONCLUSIONS

Twin pregnancies with ICP have significantly increased risks of adverse perinatal outcomes including stillbirth and preterm birth. Stillbirth occurs at an earlier gestational age in twin gestation compared to singletons, suggesting that earlier scheduled delivery should be considered in these women.

Intrahepatic cholestasis of pregnancy: Relationship between bile acid levels and maternal and fetal complications

Objective:

Intrahepatic cholestasis of pregnancy (ICP) complicates pregnancies which is characterized by elevated serum bile acid levels. ICP increases maternal and fetal morbidities. This study was designed to determine the association of maternal and fetal complications and serum bile acid levels.

Material and method:

Maternal and fetal characteristics were analyzed from the medical records of 61 patients who gave birth following a pregnancy complicated with ICP between 2009 and 2013.

Results:

Eighty seven percent of 61 cases were singletons, and 13% of them were twins. Mean SBA level was 36 μmol/L. Preterm birth rate among singletons and twin pregnancies were 24.5% and 62.5%, respectively. Mean SBA level in preterm birth group was statistically higher with respect to the term birth group (100.8 μmol/L and 25.61 μmol/L, respectively; p=0.001). No perinatal mortality associated with ICP was detected in the study group.

Conclusion:

Pregnant women with the ICP compose high-risk group in regard to fetal and maternal risks. Close follow-up of these patients is required due to increased risks such as preterm delivery, meconium staining and fetal death.

(Epi)genetics of pregnancy-associated diseases

This review describes the current knowledge regarding genetics and epigenetics of pregnancy-associated diseases with placental origin. We discuss the effect on genetic linkage analyses when the fetal genotype determines the maternal phenotype. Secondly, the genes identified by genome-wide linkage studies to be associated with pre-eclampsia (ACVR2A, STOX1) and the HELLP-syndrome (LINC-HELLP) are discussed regarding their potential functions in the etiology of disease. Furthermore, susceptibility genes identified by candidate gene approaches (e.g., CORIN) are described. Next, we focus on the additional challenges that come when epigenetics also play a role in disease inheritance. We discuss the maternal transmission of the chromosome 10q22 pre-eclampsia linkage region containing the STOX1 gene and provide further evidence for the role of epigenetics in pre-eclampsia based on the cdkn1c mouse model of pre-eclampsia. Finally, we provide recommendations to unravel the genetics of pregnancy-associated diseases, specifically regarding clear definitions of patient groups and sufficient patient numbers, and the potential usefulness of (epi)genetic data in early non-invasive biomarker development.

STOX1: Key player in trophoblast dysfunction underlying early onset preeclampsia with growth retardation

Currently, only two preeclampsia susceptibility genes (ACVR2A, STOX1) have been identified within confirmed regions with significant genome-wide linkage, although many genetic screens in multiple populations have been performed. In this paper, we focus on the STOX1 gene. The epigenetic status of this gene is discussed explaining the maternal transmission of the STOX1 susceptibility allele observed in preeclamptic families. The known upstream regulation and downstream effector genes of the transcription factor STOX1 are described. Finally, we propose a model in which we combine the cell type-specific and allele-specific effects of STOX1. This includes intrinsic effects (differential CpG island methylation) and extrinsic effects (regulation of effector genes).

The molecular genetics of intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP), also known as obstetric cholestasis, causes maternal pruritus and liver impairment, and may be complicated by spontaneous preterm labour, fetal asphyxial events and intrauterine death. Our understanding of the aetiology of this disease has expanded significantly in the last decade due to a better understanding of the role played by genetic factors. In particular, advances in our knowledge of bile homeostasis has led to the identification of genes that play a considerable role in susceptibility to ICP. In this review we consider these advances and discuss the disease in the context of bile synthesis and metabolism, focusing on the genetic discoveries that have shed light on the molecular aetiology and pathophysiology of the condition.

The genetic aspects of pre-eclampsia: achievements and limitations

Pre-eclampsia, a life-threatening disease during pregnancy, is a leading cause of global maternal mortality. Although there is substantial evidence of a genetic background, the complexity of the processes involved and nature of the maternal-fetal phenomenon do not make the search for the causative genes easy. Recent retrospective studies on the subject suggest the heritable allelic variations, particularly the utero-placental renin-angiotensin system with defective placental vascular development, could become the cornerstone for the genetics of pre-eclampsia and hence might well be associated with such defective development. Moreover, the role of immune mechanisms (immune maladaptation) deserves not to be ignored. Large-scale studies entailing genomewide scanning, sib-pair linkage analysis, and family-based association studies with appropriate power to detect genes with a lower relative risk are necessary to understand the puzzle of the disease. Moreover, recently, the importance of epigenetic features and the effect of imprinted genes related to trophoblast growth as well as fetal development on hypertension in pregnancy have been highlighted. All these possibilities are intuitively attractive and are supported by some circumstantial evidence. Although the consistent tenor of a series of papers instill some confidence, we need meticulously designed larger-scale investigations including large numbers of affected women and their babies to provide the analytic stringency essential to study the polygenic multifactorial basis of pre-eclampsia.

Expressional and epigenetic alterations of placental serine protease inhibitors: SERPINA3 is a potential marker of preeclampsia

Preeclampsia is the major pregnancy-induced hypertensive disorder. It modifies the expression profile of placental genes, including several serine protease inhibitors (SERPINs). The objective of this study was to perform a systematic expression analysis of these genes in normal and pathological placentas and to pinpoint epigenetic alterations inside their promoter regions. Expression of 18 placental SERPINs was analyzed by quantitative RT-PCR on placentas from pregnancies complicated by preeclampsia, intrauterine growth restriction, or both and was compared with normal controls. SERPINA3, A5, A8, B2, B5, and B7 presented significant differences in expression in >or=1 pathological situation. In parallel, the methylation status of the CpG islands located in their promoter regions was studied on a sample of control and preeclamptic placentas. Ten SERPIN promoters were either totally methylated or totally unmethylated, whereas SERPINA3, A5, and A8 presented complex methylation profiles. For SERPINA3, the analysis was extended to 81 samples and performed by pyrosequencing. For the SERPINA3 CpG island, the average methylation level was significantly diminished in preeclampsia and growth restriction. The hypomethylated CpGs were situated at putative binding sites for developmental and stress response (hypoxia and inflammation) factors. Our results provide one of the first observations of a specific epigenetic alteration in human placental diseases and provide new potential markers for an early diagnosis.

Genetics of preeclampsia: paradigm shifts

Segregation of preeclampsia into early-onset, placental and late-onset, maternal subtypes along with the acknowledgement of the contribution of epigenetics in placentally expressed genes proved to be a key first step in the identification of essential gene variants associated with preeclampsia. Application of this insight to other populations and related pregnancy-induced syndromes, such as HELLP, and acknowledgment of the features shared between chromosomal loci associated with preeclampsia in different populations provide the rationale for new strategies for the identification of susceptibility genes and for new and more effective diagnostic strategies.

Circulating angiogenic proteins in trisomy 13

OBJECTIVE

Women who are carrying a trisomy 13 fetus are more prone to develop preeclampsia. Excess circulating soluble fms-like tyrosine kinase-1 has been implicated recently in the pathogenesis of preeclampsia. Since the fms-like tyrosine kinase-1/soluble fms-like tyrosine kinase-1 gene is located on chromosome 13q12, we hypothesized that the extra copy of this gene in trisomy 13 may lead to excess circulating soluble fms-like tyrosine kinase-1, reduced free placental growth factor level, and increased soluble fms-like tyrosine kinase-1/placental growth factor ratio. This may then contribute to the increased risk of preeclampsia that has been observed in these patients. Our objective was to characterize the maternal circulating angiogenic proteins in trisomy 13 pregnancies.

STUDY DESIGN

Maternal serum samples of trisomy 13, 18, 21 and normal karyotype pregnancies were obtained from first and second trimester screening programs. We chose 17 cases of trisomy 13 that were matched for maternal age, freezer storage time, and parity with 85 normal karyotype control samples. Additionally, 20 cases of trisomy 18 and 17 cases of trisomy 21 were included. Cases and control samples were assayed for levels of soluble fms-like tyrosine kinase-1 and placental growth factor by enzyme-linked immunosorbent assay in a blinded fashion. Because of the skewed distributions of soluble fms-like tyrosine kinase-1 and placental growth factor, nonparametric analytic techniques were used, and the results are reported as median and ranges.

RESULTS

In early pregnancy trisomy 13 cases and control samples, the median circulating soluble fms-like tyrosine kinase-1/placental growth factor ratios were 17.0 (range, 1.2-61.3) and 6.7 (range, 0.8-62.9), respectively (P = .003). The median soluble fms-like tyrosine kinase-1/placental growth factor ratios in trisomy 18 and 21 were 4.8 (range, 0.9-53.9) and 5.1 (range, 1.0-18.1), which were not significantly different than the control samples. Furthermore, the differences between trisomy 13 and control samples were more pronounced in the second trimester specimens than in the specimens from the first trimester.

CONCLUSION

These data suggest that alterations in circulating angiogenic factors may be involved intimately in the pathogenesis of preeclampsia in trisomy 13. A larger clinical study that measures these factors longitudinally and correlates them with pregnancy outcomes is needed to further establish the link between trisomy 13, altered angiogenic factors, and preeclampsia.

Sequence variation in the ATP8B1 gene and intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a cholestatic condition that may affect women during the third trimester of pregnancy. Symptoms experienced by these women generally resolve spontaneously following delivery, but prior to delivery the fetus is at increased risk of intrauterine distress and sudden intrauterine death. The genetic etiology of most cases of ICP is unknown, although heterozygous carriers of mutations causing progressive familial intrahepatic cholestasis (PFIC) diseases may experience ICP. When examining linkage to known cholestasis genes, affected members of four Finnish ICP families shared haplotypes around ATP8B1, the gene responsible for PFIC1. This gene was subsequently screened in 176 familial and sporadic ICP patients. A total of 17 sequence changes were detected, five exonic and 12 intronic. No intronic change was associated with ICP in sporadic cases. Four intronic changes segregated with ICP in three families, a different change in each of two families and three changes in another family, although the significance of this is currently unknown. Three exonic changes were nonsynonymous, one (in exon 23) is probably a polymorphism while two predict novel amino-acid replacements (N45T and K203R). These changes, in exons 2 and 7, were detected in one individual each, and may have predisposed these individuals to ICP. In conclusion, although the exon 2 and 7 changes may have functioned as risk alleles, ATP8B1 is probably not a major gene contributing to the occurrence of ICP.

Increased serum levels of neopterin and soluble interleukin-2 receptor in intrahepatic cholestasis of pregnancy

OBJECTIVES

The etiology of intrahepatic cholestasis of pregnancy (ICP), a pregnancy-specific complication, remains not completely understood. Some alterations of immunity in ICP were reported, but the profile of immune alteration was far from clarified. The aim of this investigation was to characterize the changes of serum levels of neopterin, a marker for the activation of macrophage, and soluble interleukin-2 receptor (sIL-2R), a marker for the activation of lymphocyte, in ICP.

METHODS

Serum levels of neopterin and sIL-2R were assayed with enzyme linked immunosorbent assay (ELISA) in 30 patients with ICP and 30 normal pregnant women. Student's t-test was used for statistic analysis, and p < 0.05 was considered significant.

RESULTS

Compared with control, serum levels of neopterin (p < 0.005) and sIL-2R (p < 0.05) were increased significantly in women with ICP.

CONCLUSIONS

Activation of monocyte-macrophage and lymphocyte was demonstrated in ICP, and the participation of the activation of macrophage and lymphocyte in pathogenesis of the disease could be assumed.