Serum activin A and inhibin A elevated in pre-eclampsia: no relation to insulin sensitivity

Evaluation of first trimester maternal serum inhibin-A for preeclampsia screening

BACKGROUND

International professional organizations recommend aspirin prophylaxis to women screened high risk for preterm preeclampsia (PE) in the first trimester. The UK Fetal Medicine Foundation (FMF) screening test for preterm PE using mean arterial pressure (MAP), uterine artery pulsatility index (UTPI) and placental growth factor (PlGF) was demonstrated to have lower detection rate (DR) in Asian population studies. Additional biomarkers are therefore needed in Asian women to improve screening DRs as a significant proportion of women with preterm and term PE are currently not identified.

OBJECTIVES

To evaluate maternal serum inhibin-A at 11-13 weeks as an alternative to PlGF or as an additional biomarker within the FMF screening test for preterm PE.

STUDY DESIGN

This is a nested case-control study using pregnancies initially screened at 11-13 weeks for preterm PE using the FMF triple test in a non-intervention study conducted between December 2016 and June 2018. Inhibin-A levels were retrospectively measured in 1,792 singleton pregnancies, 112 (1.7%) with PE matched for time of initial screening with 1,680 unaffected pregnancies. Inhibin-A levels were transformed to multiple of the expected median (MoM). The distribution of log10 inhibin-A MoM in PE and unaffected pregnancies and the association between log10 inhibin-A MoM and gestational age (GA) at delivery in PE were assessed. The screening performance determined by area under receiver operating characteristic curves (AUC) and detection rates (DRs) at a 10% fixed false positive rate (FPR), for preterm and term PE was determined. All risks for preterm and term PE were based on the FMF competing risk model and Bayes theorem. Differences in AUC (ΔAUC) between different biomarker combinations were compared using the Delong test. McNemar's test was used to assess the off-diagonal change in screening performance at a fixed 10% FPR after adding inhibin-A or replacing PlGF in the preterm PE adjusted risk estimation model.

RESULTS

Inhibin-A levels in unaffected pregnancies were significantly dependent on GA, maternal age and weight and were lower in parous women with no previous history of PE. Mean log10 inhibin-A MoM in any-onset PE (p<0.001), preterm (p<0.001) and term PE (p = 0.015) pregnancies were all significantly higher than that of unaffected pregnancies. Log10 inhibin-A MoM was inversely but not significantly correlated (p = 0.165) with GA at delivery in PE pregnancies. Replacing PlGF with inhibin-A in the FMF triple test reduced AUC and DR from 0.859 and 64.86% to 0.837 and 54.05%, the ΔAUC was not statistically significant. AUC and DR when adding inhibin-A to the FMF triple test were 0.814, 54.05% and the -0.045 reduction in AUC was statistically significant (p = 0.001). At a fixed 10% FPR, replacing PlGF with inhibin-A identified 1 (2.7%) additional pregnancy but missed 5 (13.5%) pregnancies which subsequently developed preterm PE identified by the FMF triple test. Adding inhibin-A missed 4 (10.8%) pregnancies and did not identify any additional pregnancies with preterm PE.

CONCLUSION

Replacing PlGF by inhibin-A or adding inhibin-A as an additional biomarker in and to the FMF triple screening test for preterm PE does not improve screening performance and will fail to identify pregnancies that are currently identified by the FMF triple test.

Sustained Elevated Circulating Activin A Impairs Global Longitudinal Strain in Pregnant Rats: A Potential Mechanism for Preeclampsia-Related Cardiac Dysfunction

Mediators of cardiac injury in preeclampsia are not well understood. Preeclamptic women have decreased cardiac global longitudinal strain (GLS), a sensitive measure of systolic function that indicates fibrosis and tissue injury. GLS is worse in preeclampsia compared to gestational hypertension, despite comparable blood pressure, suggesting that placental factors may be involved. We previously showed that Activin A, a pro-fibrotic factor produced in excess by the placenta in preeclampsia, predicts impaired GLS postpartum. Here, we hypothesized that chronic excess levels of Activin A during pregnancy induces cardiac dysfunction. Rats were assigned to sham or activin A infusion (1.25–6 µg/day) on a gestational day (GD) 14 (n = 6–10/group). All animals underwent blood pressure measurement and comprehensive echocardiography followed by euthanasia and the collection of tissue samples on GD 19. Increased circulating activin A (sham: 0.59 ± 0.05 ng/mL, 6 µg/day: 2.8 ± 0.41 ng/mL, p < 0.01) was associated with impaired GLS (Sham: −22.1 ± 0.8%, 6 µg/day: −14.7 ± 1.14%, p < 0.01). Activin A infusion (6 µg/day) increased beta-myosin heavy chain expression in heart tissue, indicating cardiac injury. In summary, our findings indicate that increasing levels of activin A during pregnancy induces cardiac dysfunction and supports the concept that activin A may serve as a possible mediator of PE-induced cardiac dysfunction.

Dysregulated BMP2 in the Placenta May Contribute to Early-Onset Preeclampsia by Regulating Human Trophoblast Expression of Extracellular Matrix and Adhesion Molecules

Many pregnancy disorders, including early-onset preeclampsia (EOPE), are associated with defects in placental trophoblast cell invasion and differentiation during early placental development. Bone morphogenetic protein 2 (BMP2) belongs to the TGF-β superfamily and controls various physiological and developmental processes. However, the expression of BMP2 in the placenta and underlying molecular mechanisms of how BMP2 regulates trophoblast function remain unclear. In this study, we analyzed several publicly available microarray and RNA-seq datasets and revealed differences in expression of TGF-β superfamily members between gestational age-matched non-preeclamptic control and EOPE placentas. Importantly, BMP2 levels were significantly reduced in EOPE placentas compared with controls, and RNAscope in situ hybridization further demonstrated BMP2 expression was disrupted in EOPE placental villi. To explore the molecular mechanisms of BMP2-regulated early trophoblast differentiation, we examined BMP2 expression in first-trimester human placenta and found it to be localized to all subtypes of trophoblasts and the decidua. RNA-seq analysis on control and BMP2-treated primary human trophoblast cells identified 431 differentially expressed genes, including several canonical TGF-β/BMP signaling targets (BAMBI, ID1, INHBA, IGFBP3). Gene ontology annotations revealed that differentially expressed genes were involved in cell adhesion and extracellular matrix organization. Furthermore, we identified adhesion molecule with IgG-like domain 2 (AMIGO2) as a novel target for BMP2 that contributed to BMP2-induced trophoblast invasion and endothelial-like tube formation. Overall, our findings provide insight into the molecular processes controlled by BMP2 during early placental development that may contribute to the pathogenesis of EOPE.

A study of the diagnostic value of Inhibin A Tests for occurrence of preeclampsia in pregnant women

Background

Hypertensive disorders are common during pregnancy, and are among 3 important causes of maternal death. Preeclampsia occurs in 3 to 5% of pregnancies. Early diagnosis of this disorder can lead to better pregnancy outcomes.

Objective

The aim of this study was to determine the relationship between inhibin A serum levels during second stage pregnancy screening tests, and incidence and severity of preeclampsia.

Methods

In this study, 300 pregnant women who referred to Kowsar Hospital and carried out second stage pregnancy screening tests from September 2014 to March 2015 in Urmia city, Iran, were enrolled. Five ml venous blood samples were obtained from each participant, and inhibin A serum levels were evaluated in all cases. Finally, all the necessary information was obtained from the pregnancy files of participants after delivery, and gathered in a questionnaire. The data were analyzed using SPSS software version 18 and independent t-test, ANOVA and descriptive statistics were used. P-values less than 0.05 were considered significant.

Results

Among the 300 pregnant women who were studied, the gestational age at the time of acquiring blood samples was as follows: 169 cases (56.3%) at 16-17 weeks, 77 cases (25.7%) at 18-19 weeks and 14 cases at 20 weeks (4.7%). In this study, MOM of inhibin A was more than 1.25 in 12 cases that finally, preeclampsia occurred in them. This relationship was statistically significant (p=0.001). The relationship between MOM of inhibin A and severe preeclampsia was evaluated, and the relationship was significant (p=0.004). The relationship between MOM of inhibin A and pregnancy hypertension was not significant (p=0.643).

Conclusion

Considering the results of this study, we can conclude that MOM of inhibin A levels in maternal serum during second stage pregnancy screening tests can predict incidence and severity of developing preeclampsia in pregnant women. This is not true in cases of pregnancy hypertension.

Transforming growth factor β signaling in uterine development and function

Transforming growth factor β (TGFβ) superfamily is evolutionarily conserved and plays fundamental roles in cell growth and differentiation. Mounting evidence supports its important role in female reproduction and development. TGFBs1-3 are founding members of this growth factor family, however, the in vivo function of TGFβ signaling in the uterus remains poorly defined. By drawing on mouse and human studies as a main source, this review focuses on the recent progress on understanding TGFβ signaling in the uterus. The review also considers the involvement of dysregulated TGFβ signaling in pathological conditions that cause pregnancy loss and fertility problems in women.

Association of the rs1424954 polymorphism of the ACVR2A gene with the risk of pre-eclampsia is not replicated in a Finnish study population

BACKGROUND

Pre-eclampsia/eclampsia is a common vascular pregnancy disorder associated with high maternal and infant mortality and morbidity worldwide. The role of Activin A and more recently type 2 Activin A receptor (ACVR2A) in the pathogenesis of pre-eclampsia has been the subject of genetic and biochemical research with controversial results.

FINDINGS

We genotyped a candidate pre-eclampsia-associated single nucleotide polymorphism rs1424954 in ACVR2A in three independent study populations of Finnish pre-eclamptic (total N = 485) and non-pre-eclamptic (total N = 449) women using pre-designed TaqMan allele discrimination assay and polymerase chain reaction. The possible association of the alleles and genotypes of interest with pre-eclampsia was evaluated using the chi-square test and logistic regression analysis. We found no association of rs1424954 to pre-eclampsia in Finnish patients.

CONCLUSIONS

rs1424954 was not associated to pre-eclampsia in the Finnish study population. We hypothesise that while the gene associates to pre-eclampsia worldwide, the causative polymorphism in ACVR2A may be unique in genetically differing populations. Further research is needed to characterise the haplotype structure of ACVR2A in order for the causative genetic variant to be identified.

First-trimester maternal serum activin A in pre-eclampsia and fetal growth restriction

OBJECTIVE

To investigate whether the reported increase in maternal serum activin A concentration in pre-eclampsia is evident from the first trimester.

DESIGN

This was a case-control study carried out in antenatal clinics among singleton pregnancies at 10-14 weeks of gestation.

METHODS

Activin A concentration was measured in stored maternal serum samples obtained at 11-14 weeks of gestation from 131 women who subsequently developed pre-eclampsia, 77 who developed non-proteinuric pregnancy-induced hypertension, 141 with fetal growth restriction in the absence of hypertensive complications and from 494 normotensive controls.

RESULTS

Compared to the median activin A level in the control group (1.00 MoM), the median MoM in the patients who subsequently developed pre-eclampsia and pregnancy-induced hypertension (1.49 MoM and 1.32 MoM, respectively) was significantly increased (p < 0.001), and in patients with fetal growth restriction (1.02 MoM) it was not significantly different (p = 0.57). In the pre-eclampsia group (n = 131) the disease was considered to be sufficiently severe to necessitate iatrogenic delivery before 35 weeks in 25 patients, and in this group the median MoM was 1.92.

CONCLUSION

Maternal serum activin A concentration at 12 weeks of gestation in pregnancies which subsequently develop hypertensive disease is increased, whereas in those complicated by fetal growth restriction it is normal.

Genetic association of the activin A receptor gene (ACVR2A) and pre-eclampsia

Pre-eclampsia is a common serious disorder of human pregnancy, which is associated with significant maternal and perinatal morbidity and mortality. The suspected aetiology of pre-eclampsia is complex, with susceptibility being attributable to multiple environmental factors and a large genetic component. Recently, we reported significant linkage to chromosome 2q22 in 34 Australian/New Zealand (Aust/NZ) pre-eclampsia/eclampsia families, and activin A receptor type IIA (ACVR2A) was identified as a strong positional candidate gene at this locus. In an attempt to identify the putative risk variants, we have now comprehensively re-sequenced the entire coding region of the ACVR2A gene and the conserved non-coding sequences in a subset of 16 individuals from these families. We identified 45 single nucleotide polymorphisms (SNPs), with 9 being novel. These SNPs were genotyped in our total family sample of 480 individuals from 74 Aust/NZ pre-eclampsia families (including the original 34 genome-scanned families). Our best associations between ACVR2A polymorphisms and pre-eclampsia were for rs10497025 (P = 0.025), rs13430086 (P = 0.010) and three novel SNPs: LF004, LF013 and LF020 (all with P = 0.018). After correction for multiple hypothesis testing, none of these associations reached significance (P > 0.05). Based on these data, it remains unclear what role, if any, ACVR2A polymorphisms play in pre-eclampsia risk, at least in these Australian families. However, it would be premature to rule out this gene as significant associations between ACVR2A SNPs and pre-eclampsia have recently been reported in a large Norwegian (HUNT) population sample.

Association between the candidate susceptibility gene ACVR2A on chromosome 2q22 and pre-eclampsia in a large Norwegian population-based study (the HUNT study)

Genome-wide scans in Icelandic, Australian/New Zealand and Finnish pedigrees have provided evidence for maternal susceptibility loci for pre-eclampsia on chromosome 2, although at different positions (Iceland: 2p13 and 2q23, Australia/New Zealand: 2p11-12 and 2q22, Finland: 2p25). In this project, a large population-based (n=65 000) nested case-control study was performed in Norway to further explore the association between positional candidate genes on chromosome 2q and pre-eclampsia, using single-nucleotide polymorphisms (SNPs). DNA samples from 1139 cases (women with one or more pre-eclamptic pregnancies) and 2269 controls (women with normal pregnancies) were genotyped using the Applied Biosystems SNPlex high-throughput genotyping assay. In total, 71 SNPs within positional candidate genes at 2q22-23 locus on chromosome 2 were genotyped in each individual. Genotype data were statistically analysed with the sequential oligogenic linkage analysis routines (SOLAR) computer package. Nominal evidence of association was found for six SNPs (rs1014064, rs17742134, rs1424941, rs2161983, rs3768687 and rs3764955) within the activin receptor type 2 gene (ACVR2A) (all P-values <0.05). The non-independence of statistical tests due to linkage disequilibrium between SNPs at a false discovery rate of 5% identifies our four best SNPs (rs1424941, rs1014064, rs2161983 and rs3768687) to remain statistically significant. The fact that populations with different ancestors (Iceland/Norway-Australia/New Zealand) demonstrate a common maternal pre-eclampsia susceptibility locus on chromosome 2q22-23, may suggest a general role of this locus, and possibly the ACVR2A gene, in pre-eclampsia pathogenesis.

Prediction of pre-eclampsia by uterine artery Doppler ultrasonography and maternal serum pregnancy-associated plasma protein-A, free beta-human chorionic gonadotropin, activin A and inhibin A at 22 + 0 to 24 + 6 weeks' gestation

OBJECTIVE

To investigate the potential value of combining uterine artery Doppler ultrasonography with the measurement of maternal serum pregnancy-associated plasma protein-A (PAPP-A), free beta-human chorionic gonadotropin (beta-hCG), activin A and inhibin A at 22 + 0 to 24 + 6 weeks' gestation, in the prediction of pregnancies that subsequently develop pre-eclampsia.

METHODS

The maternal serum PAPP-A, free beta-hCG, activin A and inhibin A concentrations at 22 + 0 to 24 + 6 weeks' gestation were measured in samples obtained from women with singleton pregnancies who participated in a screening study for pre-eclampsia by transvaginal color flow Doppler measurement of the uterine artery pulsatility index (PI). A search was made of the database to identify those who subsequently developed pre-eclampsia (n = 24) and a group of controls with normal outcome (n = 144). Regression analysis was performed to establish any relationship between the biochemical markers themselves and between the biochemical markers and uterine artery mean PI. A multivariate Gaussian model combining various biochemical markers with uterine artery mean PI was developed using standard statistical modeling techniques and the performance of such models in discriminating cases with pre-eclampsia was evaluated by receiver-operating characteristics curve (ROC) analysis.

RESULTS

In the pre-eclampsia group, compared to the controls, the uterine artery mean PI and the maternal serum levels of PAPP-A, free beta-hCG, activin A and inhibin A were significantly increased. The predicted detection rates of pre-eclampsia, for a false positive rate of 5%, was 50% by uterine artery mean PI, 5% by PAPP-A, 10% by free beta-hCG, 35% by inhibin A and 44% by activin A. Screening by a combination of uterine artery mean PI and maternal serum activin A and inhibin A could detect 75% and 92% of patients who subsequently developed pre-eclampsia, for false positive rates of 5% and 10%, respectively.

CONCLUSION

Screening for pre-eclampsia by uterine artery PI at 22 + 0 to 24 + 6 weeks' gestation can be improved by measurement of activin A and inhibin A levels.

Activin and follistatin in female reproduction

Activin and follistatin were initially identified in the follicular fluid based on their effects on pituitary FSH secretion in the mid-1980s. It is now evident that activin, follistatin and activin receptors are widely expressed in many tissues where they function as autocrine/paracrine regulators of a variety of physiological processes including reproduction. The major function of follistatin is to bind to activin with high affinity and block activin binding to its receptors. Total activin A and follistatin are also found in the maternal circulation throughout pregnancy. Activin A levels are increased in abnormal pregnancies such as pre-eclampsia, fetal growth restriction and gestational hypertension. The placenta, vascular endothelial cells and activated peripheral mononuclear cells (PBMC) may all contribute to the raised levels of activin A in pre-eclampsia with unaltered follistatin in pre-eclamptic placenta, PBMCs or vascular endothelial cells suggesting the availability of 'free' activin A that could be biologically active in these cells.

Prediction of preeclampsia: can it be achieved?

In this review, the various biochemical tests that have been proposed for the prediction of preeclampsia are described and evaluated. Placenta hormone markers do not predict future disease. They denounce the early placental changes that are part of the evolving disease and only predict the imminent of preeclamptic syndrome. This explains why tests are better predictors when preeclampsia supervenes shortly, and why screening in the first trimester is unlikely to work as well as in the second trimester. The use of multiple markers in the screening should reflect different aspects of the disease process and could increase the specificity and sensitivity of the screening and work on different etiologic factors. The possible use of second-trimester biochemical screening to predict the risk of preeclampsia remains to be investigated in the high-risk population.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to list the various theories on the etiology of preeclampsia, to relate the various risk factors for the development of preeclampsia, and to describe the various screening tests for preeclampsia.

Predictive value of hormone measurements in maternal and fetal complications of pregnancy

Intrauterine tissues (placenta, amnion, chorion, decidua) express hormones and cytokines that play a decisive role in maternal-fetal physiological interactions. The excessive or deficient release of some placental hormones in association with gestational diseases may reflect an abnormal differentiation of the placenta, an impaired fetal metabolism, or an adaptive response of the feto-placental unit to adverse conditions. This review is focused on the applicability of hormone measurements in the risk assessment, early diagnosis, and management of pregnancies complicated by Down's syndrome, fetal growth restriction, preeclampsia, preterm delivery, and diabetes mellitus. Combined hormonal tests or the combination of hormones and ultrasound may achieve reasonable sensitivity, but research continues to simplify the screening programs without sacrificing their accuracy. Only in a few instances is there sufficient evidence to firmly recommend the routine use of hormone tests to predict maternal and fetal complications, but the judicious use of selected tests may enhance the sensitivity of the risk assessment based solely on clinical and ultrasound examination.

Measurement of inhibin A and activin A in pregnancy--possible diagnostic applications

Knowledge of the roles of inhibins and activins has progressed rapidly since the development of a specific and sensitive assay that can be used for measurements on human serum and amniotic fluid samples. There is a sound theoretical basis for the role of transforming growth factor-beta family members in inflammatory processes, many of which are analogous to implantation, parturition and a variety of pathological conditions in pregnancy. This review explores the potential use of assays for inhibins and activins in clinical practice and suggests further areas for research.