Angiotensinogen gene variation in a population case-control study of preeclampsia/eclampsia in Australians and Chinese

Correlation of single nucleotide polymorphisms in the AGT gene with susceptibility to systemic lupus erythematosus in Northeast China

To investigate the correlation between susceptibility to systemic lupus erythematosus (SLE) and single nucleotide polymorphisms (SNPs) rs699, rs4762 and rs1926723 in the AGT gene in the population of Northeast China, while also introducing a new method for early detection of SLE. A total of 856 cases of SLE patients and healthy volunteers who attended the First Affiliated Hospital of Harbin Medical University from January 2020 to December 2022 were recruited. Clinical information and biood samples were collected from particpants in this study. SNaPshot sequencing technology was used to sequence the bases of the rs699, rs4762 and rs1926723 in the AGT gene. The genetic stability of SNPs was analysed by means of Hardy-Weinberg (HWE) genetic equilibrium. The study examined the correlation between genetically stable SNPs and susceptibility to SLE using logistic regression analysis. Rs699 did not adhere to the principles of the HWE genetic equilibrium (p < .01). Conversely, both rs4762 and rs1926723 conformed to the HWE genetic equilibrium (p > .05). However, no significant differences in genotypes and alleles frequencies of the rs4762 were observed between the two groups (p > .05). Furthermore, there was a significant difference in the distribution of AG, GG genotypes frequency and G allele frequency at the rs1926723 between the two groups (p < .001). Individuals with AG and GG genotypes and the G allele had a significantly lower frequency of SLE, indicating a potential genetic protective factor against susceptibility to the SLE. The SNPs rs1926723 may be linked to the susceptibility to SLE, and the AG, GG genotypes and the G allele may be important protective factors for the development of SLE in Northeast China.

Pertinence between risk of preeclampsia and the renin-angiotensin-aldosterone system (RAAS) gene polymorphisms: an updated meta-analysis based on 73 studies

The aetiological mechanism of preeclampsia (PE) is unclear exactly, so we attempted to investigate the association between susceptibility to preeclampsia and renin-angiotensin-aldosterone system (RAAS) gene polymorphisms to explore the aetiology in terms of genetics. A systematic search was performed in electronic databases to identify relevant studies. Eventually 73 studies were enrolled, odds ratios were generated by 5 genetic models. In overall analysis, significant associations were detected for AGT M235T, AT1R A1166C and CYP11B2 C344T whereas negative correlation was shown for AGT T174M. As stratified by race and geography, AGT 235T allele and AT1R 1166C allele increased preeclampsia risk and AGT T174M was justified uncorrelated with preeclampsia. Our meta-analysis illustrated that AGT 235T allele and AT1R 1166C allele increased and CYP11B2 344T allele decreased preeclampsia risk while AGT T174M polymorphism did not change preeclampsia risk. Hence, pregnant women carrying high-risk genotypes need strengthened management to prevent and early identification of preeclampsia.

Associations between AGT, MTHFR, and VEGF gene polymorphisms and preeclampsia in the Chinese population

INTRODUCTION

Preeclampsia (PE) is a pregnancy-specific multisystemic syndrome. This study aimed to investigate the associations between angiotensinogen (AGT), methylenetetrahydrofolate reductase (MTHFR), vascular endothelial growth factor (VEGF) polymorphisms, and PE in the Han Chinese population.

METHODS

We genotyped 26 single-nucleotide polymorphisms (SNP) in three genes by using QuantStudio™ 12 K Flex Real-Time PCR technology in 168 patients with PE and 204 healthy pregnant control subjects. The associations of tested polymorphisms with PE were analyzed at allele, genotype, and haplotype levels.

RESULTS

A common coding variant in MTHFR, rs2274976, was significantly associated with increased risk of PE in both allelic and genotype models (P < 0.05). The heterozygous genotypes of rs699 (G/A vs G/G) in AGT gene and rs3025035 (C/T vs C/C) in VEGF gene showed weak associations with increased PE risk, whereas the mutant homozygous genotype of rs3024987 (TT vs C/C) and the heterozygous genotype of rs3025039 (C/T vs C/C) in VEGF gene displayed weak associations with decreased PE risk (P < 0.05).

DISCUSSION

However, these weak associations lost significance after multiple testing correction. The results indicated that rs2274976 in MTHFR gene may contribute to the increased risk of PE in pregnant women. AGT and VEGF gene polymorphisms may not play a significant role in PE development.

A study of the association between angiotensinogen (AGT) gene polymorphism (M235T) and preeclampsia in Thai pregnant women

AGT M235T gene polymorphism may cause increased blood pressure in preeclampsia in pregnancy; however, the evidence remains controversial. This study investigated the association between AGT M235T and preeclampsia in Thai pregnant women. A case-control study was conducted to compare the distributions of AGT M235T genotypes and alleles between 142 normotensive pregnancies as controls and 61 preeclampsia pregnancies as cases in a tertiary-care university hospital in Chiang Mai, Thailand. The results show that the distribution of AGT M235T genotypes (MM, MT and TT) of both groups were not significantly different (preeclampsia: 0.0, 16.4, 83.6%; control: 2.1, 22.5, 75.4%, respectively; p = .30). Additionally, there was no statistical difference in the distribution of AGT M235T alleles (M and T alleles) (preeclampsia: 8.2 and 91.8% versus control: 13.4 and 86.6%, respectively; p = .14). In this study, the distributions of AGT M235T were not different in both groups. Therefore, AGT M235T polymorphism may not play a significant role in preeclampsia pathophysiology in Thai population.Impact statementWhat is already known on this subject? Preeclampsia is one of the major complications during pregnancy; it significantly affects maternal and perinatal morbidity and mortality. Effort has been made to find markers and predictors that are associated with the pathophysiology of preeclampsia. AGT M235T gene polymorphism may cause increased blood pressure in preeclampsia pregnancy; however, evidences are still controversial.What do the results of this study add? We conducted a case-control study to compare the distributions of AGT M235T genotypes and alleles between 142 normotensive pregnancies as controls and 61 preeclampsia pregnancies as cases. The results show that preeclamptic women are more likely to deliver at an earlier gestational age and have a smaller baby in comparison with the normotensive group. In addition, women with preeclampsia had a higher chance of having an operative delivery and caesarean section. However, the distribution of AGT M235T polymorphism of preeclampsia women and the control group were not significantly different.What are the implications of these findings for clinical practice and/or further research? AGT M235T polymorphism may not play a significant role in preeclampsia pathophysiology in Thai population.

Three polymorphisms of renin-angiotensin system and preeclampsia risk

Purpose

Some data suggest an association between the single nucleotide polymorphisms AGT T704C, ACE I/D, and AT1R A1166C and preeclampsia, but overall, the data are conflicting; the aim of our study was to discover a more stable and reliable association between these polymorphisms and PE risk.

Methods

A comprehensive literature search for this meta-analysis was conducted. Odds ratios (OR) and 95% confidence intervals (CIs) were calculated to evaluate the strength, and heterogeneity test was conducted. Trial sequential analysis was also performed.

Results

A total of forty studies were finally included in our meta-analysis. The AGT T704C polymorphism was associated with PE risk in three genetic models (dominant OR = 1.33, 95%CI = 1.12–1.59; heterozygote OR = 1.26, 95%CI = 1.05–1.52; homozygote OR = 1.44, 95%CI = 1.14–1.83). No heterogeneity was observed in the three genetic models for the ACE I/D polymorphism. For subgroup analysis by geography, no significant association was detected. Significant associations were observed in mixed race, early-onset, late-onset, and more than 200 subgroups for the AT1R A1166C polymorphism; however, only one study was analyzed in these subgroups.

Conclusions

Our results indicated the AGT T704C and ACE I/D polymorphisms were associated with an increased risk of PE. Increased risks were also observed for the two polymorphisms in subgroups including Asians, Europeans, Caucasoid, and Mongoloid. Moreover, an increased PE risk with the ACE I/D polymorphism in the severe PE population was also detected. Regarding the AT1R A1166C polymorphism, weak associations were observed, but further studies are required.

Electronic supplementary material

The online version of this article (10.1007/s10815-020-01971-8) contains supplementary material, which is available to authorized users.

Association of angiotensinogen gene polymorphisms and angiogenic factors with preeclampsia in Chinese women

OBJECTIVE

To investigate the association of angiotensinogen (AGT) gene polymorphisms and angiogenic factors with preeclampsia (PE) in Chinese women.

METHODS

A study on Chinese women was performed. Detection of the M235T polymorphism of AGT gene was carried out by PCR. Using a χ² test, genotype and allele frequencies were compared in all groups. Maternal serum levels of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt1) at gestation were compared between 92 women with PE and 100 controls by ELISA.

RESULTS

Compared to the controls, the AGT homozygous of TT genotype in PE occurred significantly more frequently and the T allele was observed to occur more frequently than the M allele (p < 0.05). sFlt1 was present in high quantities in the serum of women with PE and was associated with low levels of free VEGF and PlGF (p < 0.05). Plasma sFlt1 levels are higher in PE patients with TT heterozygotes compared with MM homozygotes, but PIGF is lower (p < 0.05). Plasma VEGF concentrations showed no significant difference.

CONCLUSIONS

Our study showed that AGT M235T polymorphism is associated with PE in Chinese women. Furthermore, the gene polymorphism of the components of the renin-angiotensin system may contribute to the concentration alterations of sFlt1, VEGF, and PlGF in maternal serum, which causes disordered vasculogenesis contributing to PE.

Angiotensinogen gene M235T and T174M polymorphisms and susceptibility of pre-eclampsia: a meta-analysis

There are controversies in reports on the association of the angiotensinogen (AGT) gene polymorphisms with the risk of developing pre-eclampsia (PE). We performed a meta-analysis to examine the association between the AGT polymorphisms and PE risk: M235T (31 studies involving 2555 patients and 6114 controls) and T174M (six studies involving 681 patients and 2076 controls). For the M235T polymorphism, the TT genotype increased the PE risk as compared to the MM genotype (odds ratio 1.61, 95% confidence intervals 1.22-2.14, P= 0.001). When stratified by ethnicity, the TT genotype remained significantly associated with higher PE risk in Caucasians and Mongolians but not in Africans. Similar results were also obtained under all three genetic models of the M235T polymorphism. For the T174M polymorphism, no significant association was found in the comparisons (MT vs. TT and MM vs. TT) and under any genetic models. The analysis excluding the highly significant Hardy-Weinberg equilibrium-violating studies and sensitivity analysis further strengthened the validity of these associations. No publication bias was observed in this study. This meta-analysis demonstrates that the AGT M235T polymorphism is significantly associated with PE whereas the T174M polymorphism is not.

Associations of ACE I/D, AGT M235T gene polymorphisms with pregnancy induced hypertension in Chinese population: a meta-analysis

PURPOSE

There have been many studies concerning the associations of angiotensin-converting enzyme (ACE) I/D, angiotensinogen (AGT) M235T polymorphisms with pregnancy induced hypertension (PIH) among Chinese populations. However, the results were inconsistent, prompting the necessity of meta-analysis.

METHODS

Studies published in English and Chinese were mainly searched in EMbase, PubMed and CBM up to January 2012.

RESULTS

Twenty-three studies with 3,551 subjects for ACE I/D and seven studies with 1,296 subjects for AGT M235T were included. Significant associations were found between ACE I/D and PIH under dominant, recessive and allelic models. A separate analysis confined to preeclampsia suggested that ACE I/D was associated with preeclampsia under recessive model and allelic model, but not dominant model. Stratified analyses were conducted as meta-regression analysis indicated that the sample size of case group was a significant source of heterogeneity, which suggested no significant association between ACE I/D and PIH in the subgroup of more than 100 cases. Associations were found between AGT M235T and PIH under dominant genetic model (OR = 1.59; 95 %CI: 1.04-2.42), recessive genetic model (OR = 1.60; 95 %CI: 1.07-2.40), and allelic model (OR = 1.40; 95 %CI: 1.17-1.68). No publication bias was found in either meta-analysis.

CONCLUSIONS

The present meta-analysis suggested significant associations between ACE I/D, AGT M235T and PIH in Chinese populations. However, no significant association was found between ACE I/D and PIH in the subgroup of more than 100 cases. Studies with larger sample sizes are necessary to investigate the associations between gene polymorphisms and PIH in Chinese populations.

AGT M235T polymorphism contributes to risk of preeclampsia: evidence from a meta-analysis

Objective: Preeclampsia a hypertensive disorder of pregnancy that mainly manifests as high blood pressure and proteinuria. Angiotensinogen (AGT) plays important roles in the regulation of blood pressure. The purpose of this study was to investigate the relationship between AGT M235T polymorphism and risk of preeclampsia using a meta-analysis. Methods: In this meta-analysis, 22 studies were selected by searching PubMed, EMBASE, ISI and CNKI databases up to October 2011. Crude odds ratios with corresponding 95% confidence intervals were used to evaluate the association between the AGT M235T polymorphism and risk of preeclampsia. Subgroup analyses were conducted by ethnicity and parity. Results: The TT genotype of the AGT M235T polymorphism was associated with elevated risk of preeclampsia in the overall analysis. In subgroup analysis according to ethnicity, increased risks were also found in Caucasians. After stratification based on parity, the excess risk was found in multigravida. Conclusions: These results showed that the TT genotype may play critical roles in the development of preeclampsia.

Angiotensinogen G(–6)A Polymorphism Is Associated With the Elevation of Blood Pressure in the Hypertensive Disorders of Pregnancy

The objective of the present study was to determine whether angiotensinogen G(–6)A polymorphism is associated with the elevation of blood pressure (BP) in the hypertensive disorders of pregnancy in Korean population. The subjects included 201 cases with the hypertensive disorders of pregnancy and 160 healthy controls. The medical records of subjects were reviewed. Cases were classified into the four subtypes (transient hypertension, preeclampsia, chronic hypertension, and preeclampsia superimposed on chronic hypertension) by the diagnostic criteria suggested by the National High Blood Pressure Education Program Working Group. Cases were also divided into the high and low BP group by the elevation of BP (diastolic BP greater than or equal to 110 mmHg). Maternal angiotensinogen G(–6)A polymorphism was determined by restriction fragment length polymorphism. Frequencies of AA genotype were significantly higher in the high than in the low BP group in the preeclampsia, superimposed preeclampsia, and the combined group (N = 201), suggesting that the angiotensinogen G(–6)A allele was significantly associated with the elevation of BP in the hypertensive disorders of pregnancy among South Korean women. The present findings imply that the elevation of BP can serve as an endophenotype for a spectrum of hypertensive conditions in pregnancy.

The associations between maternal and fetal angiotensinogen M235T polymorphism and pregnancy-induced hypertension in Chinese women

This study was to investigate whether the maternal and fetal angiotensinogen (AGT) M235T polymorphism were associated with the risk of pregnancy-induced hypertension (PIH) in Chinese Han ethnic women. Using a case-control mother-baby dyads study, a total of 226 maternal/offspring pairs were recruited at Anyang Maternal and Child Health Hospital from January 2008 to December 2009. Genomic DNA was extracted from maternal venous and cord blood. We genotyped the AGT M235T polymorphism by using PCR-RFLP assay and examined the association with PIH using logistic regression analysis. In the current study, the maternal AGT M235T polymorphism showed no effect on the risk of PIH (P = .786) while the fetal AGT M235T polymorphism is significantly associated with PIH in Chinese Han ethnic women (P = .004). The fetus carrying TT genotype is a protective factor in developing PIH in the study population (OR = .28, 95% CI = .14-0.59).

Role of C825T Polymorphism of GNβ3 Gene in Preeclampsia

OBJECTIVE

The main objective of the study was to understand the role of C825T polymorphism that generates a splice variant in the beta3 subunit of heterotrimeric G-protein in preeclampsia.

RESULTS

We analyzed genomic DNA of 151 women with preeclampsia (72 Caucasians and 79 African-Americans) and 198 women with normal delivery (102 Caucasians and 96 African-Americans) for C825T polymorphism of GNbeta3 gene. The T-allele frequency in Caucasian women with preeclampsia was 0.42 as compared to 0.25 in normal pregnant women (p = 0.0004) and in African-American women with preeclampsia was 0.82 as compared to 0.68 in normal pregnant women (p = 0.0028).

CONCLUSIONS

Results of these experiments show that the allele frequency of C825T polymorphism is significantly different in women with preeclampsia compared with women with normal delivery in Caucasian as well as African-American population.

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

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.

Impact of maternal angiotensinogen M235T polymorphism and angiotensin-converting enzyme insertion/deletion polymorphism on blood pressure, protein excretion and fetal outcome in pregnancy

OBJECTIVE

To test the hypothesis that genetically determined alterations of the renin-angiotensin system are associated with hypertensive disorders in pregnancy.

METHODS

A genetic association study was conducted at the obstetrics department of the Charité university hospital, Berlin, Germany. A total of 1068 Caucasian women were consecutively included after delivery and genotyped for the angiotensinogen M235T polymorphism and the angiotensin-converting enzyme (ACE) insertion/deletion polymorphism.

RESULTS

Women homozygous for the angiotensinogen T allele have significantly elevated mean systolic and diastolic blood pressures in the third trimester (118.4 +/- 1.1/71.5 +/- 0.7 versus 116.9 +/- 0.3/70.4 +/- 0.2 mmHg, n = 128 versus 940; P < 0.05). This finding is especially pronounced in the subgroup of primigravid women. The ACE polymorphism is not associated with blood pressure during pregnancy. None of the polymorphisms is associated with urinary protein excretion or oedema during pregnancy. Maternal polymorphisms do not influence fetal growth and birth weight. There is, however, an interesting trend towards an increased incidence of circulatory system malformations in newborns carrying alleles that are known to be associated with decreased intrinsic renin-angiotensin system activity.

CONCLUSION

We demonstrate for the first time in a large Caucasian population that a common maternal polymorphism of the angiotensinogen gene is related to a blood pressure increase during pregnancy. The angiotensinogen M235T polymorphism might contribute to the multifactorial pathogenesis of gestational hypertension and pre-eclampsia.

Genetic polymorphisms in vasoactive genes and preeclampsia: a meta-analysis

There are controversies in reports on the association of polymorphisms in endothelial nitric oxide synthase, angiotensinogen, angiotensin receptor type 1 and angiotensin-converting enzyme genes with an increased risk of developing preeclampsia. We performed a systematic search of published case-control studies through the PubMed database up to January 2006, and report the results of a meta-analysis of polymorphisms investigated in more than five studies: Glu298Asp in eNOS gene (9 analyses involving 1055 patients and 1788 controls), Met235Thr in AGT gene (13 analyses involving 1128 patients and 2278 controls), and intron 16 insertion-deletion polymorphism in ACE gene (10 analyses involving 1121 patients and 1361 controls). Statistically significant associations with preeclampsia were identified for the Met235Thr/AGT polymorphism: OR 1.65 (95% CI 1.19, 2.29) if the polymorphism is considered under the dominant genetic model, and OR 1.54 (95% CI 1.12, 2.11) under the recessive model. For insertion-deletion/ACE polymorphism, statistical significance was demonstrated when the polymorphism was considered under the recessive model: OR 1.51 (95% CI 1.17, 1.94). No single polymorphism was identified as having a major effect.

Preeclampsia: a renal perspective

Preeclampsia is a syndrome that affects 5% of all pregnancies, producing substantial maternal and perinatal morbidity and mortality. The aim of this review is to summarize our current understanding of the pathogenesis of preeclampsia with special emphasis on the recent discovery that circulating anti-angiogenic proteins of placental origin may play an important role in the pathogenesis of proteinuria and hypertension of preeclampsia.

Preventing pregnancy-induced hypertension: are there regional differences for this global problem?

Developing countries have had persistently higher rates of maternal and child mortality due to pre-eclampsia in comparison with developed countries. Moreover, evidence from studies of interventions to prevent pre-eclampsia have given contradictory results. In this review, we discuss the underlying causes of pre-eclampsia, and the results of clinical trials performed to prevent this disease, that support the proposal that the causes and strategies to prevent pre-eclampsia are different in developed and developing countries. We also suggest that the establishment of an adequate prenatal care is the only effective way to reduce the incidence of pre-eclampsia in populations from developing countries, especially in women at high risk of pregnancy-induced hypertension.

Genetic thrombophilia has pleiotropic effects in pregnancy

Genetic thrombophilia has been established as a risk factor for pregnancy-associated disorders, such as thrombosis, early and late miscarriage, and pre-eclampsia. Associations between the factor V (F5) Leiden G1691A and the prothrombin/factor II (F2) G20210A SNPs and pre-eclampsia have been evaluated in over 50 association studies. A pooled analysis of 23 and 11 studies demonstrates that carriage of the F5 Leiden G1691A (p < 0.001; odds ratio [OR] 2.0; 95% confidence interval [CI] 1.6-2.5) and the F2 G20210A (p < 0.001; OR 1.8; 95% CI 1.1-2.9) SNPs is significantly associated with pre-eclampsia. Besides pre-eclampsia, genotyping for the F5 Leiden G1691A and the F2 G20210A SNPs is also useful for individual risk assessment regarding pregnancy-associated thrombosis. Carriers of the F5 Leiden G1691A SNP will develop this condition in 6.4% of heterozygotes and in 8.9-16.7% of homozygotes. A total of 6.2% of women with the F2 G20210A SNP and 17.8% of women with simultaneous carriage of the F5 Leiden G1691A and F2 G20210A SNPs will develop pregnancy-associated thrombosis. Both the F5 Leiden G1691A and F2 G20210A SNPs are also risk factors of early recurrent, late recurrent and late spontaneous miscarriage based on a published meta-analysis of 31 studies. These women may benefit from prophylactic heparinization. Six case-control and cohort studies of 687 women with genetic thrombophilia document live birth rates of 82% (181/221) using low-molecular-weight heparin or fractionated heparin compared with 20% (95/466) without therapy (p < 0.001, OR 17.7; 95% CI 12.2-25.5). Based on the data in the literature, including association studies and meta-analyses of these association studies, it can be concluded that genetic thrombophilia due to carriage of the F5 Leiden G1691A and F2 G20210A SNPs is a significant and clinically relevant risk factor for pre-eclampsia, pregnancy-associated thrombosis, and early and late miscarriages.

Associations of polymorphisms of the angiotensinogen M235 polymorphism and angiotensin-converting-enzyme intron 16 insertion/deletion polymorphism with preeclampsia in Korean women

OBJECTIVE

The contribution of genetic factors to preeclampsia has been well documented. However, there has not been any study done on the association between preeclampsia and the angiotensinogen (AGT) M235T polymorphism and angiotensin-converting-enzyme (ACE) intron 16 insertion/deletion (I/D) polymorphism among Korean preeclampsia women. We performed a hospital-based case-control study on Korean women to investigate the association between preeclampsia and the angiotensinogen M235T polymorphism and also to determine the association between preeclampsia and the angiotensin-converting-enzyme intron 16 polymorphism.

METHODS

DNA was extracted from whole blood of 104 preeclampsia patients and 114 healthy pregnant women. All samples were genotyped for all the polymorphisms using amplification after PCR of known allelic variants. Results were analyzed with the chi-square test, Student's t-test, and logistic regression.

RESULTS

18 of 50 women with preeclampsia (36.0%) in nulliparous women and 15 of 37 women with preeclampsia (40.5%) in parous women were homozygous for methionine (M235) to threonine (T235) substitution at residue 235 of AGT gene, versus 12 of 38 women in nulliparous control women and 18 of 50 women in parous control women. There was no association between the AGT M235T polymorphism and preeclampsia according to age. Fourteen of 55 women with preeclampsia (25.5%) in nulliparous women and 11 of 39 women with preeclampsia (28.2%) in parous women were homozygous for the D allele of the ACE intron 16, versus 9 of 52 women in nulliparous control women and 16 of 53 women in parous control women. No association was demonstrated between D allele of ACE intron 16 and preeclampsia according to age. There were significant differences in birth weight and delivery weeks between controls and preeclampsia patients (P < 0.001). There were no significant differences in age and nulliparity between controls and preeclampsia patients.

CONCLUSION

The result indicates that the AGT M235T polymorphism and the ACE intron 16 polymorphism play no significant role in preeclampsia observed in Korean women.

Hypertension-related gene polymorphisms in pre-eclampsia, eclampsia and gestational hypertension in Black South African women

OBJECTIVE

To examine whether polymorphisms in the renin-angiotensin system (RAS) are associated with pregnancy-related hypertensive disorders in a black South African population.

DESIGN

The angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen M235T and angiotensin II receptor type 1 1166A<--C polymorphisms were assessed in study groups comprising 204 women with pre-eclampsia, 120 with eclampsia, 67 with early onset pre-eclampsia and 78 with gestational hypertension.

METHODS

Using chi analysis, results were compared with those obtained from 338 ethnically matched normotensive pregnant women following normal full term pregnancies. No significant differences in the distribution of any of these polymorphisms were found between patients with pre-eclampsia or eclampsia and the normal control subjects. Patients with gestational hypertension were less frequently homozygous for the ACE insertion polymorphism compared with controls (5 versus 13%, respectively; P = 0.049; odds ratio 0.36 [95% confidence interval (CI) 0.09-1.04]).

CONCLUSION

The commonly occurring RAS polymorphisms are not predictive of pre-eclampsia or eclampsia in the Black South African population.

Association of Angiotensin-converting enzyme and angiotensinogen gene polymorphisms with preeclampsia

We tested the hypothesis that angiotensin-converting enzyme (ACE) and angiotensinogen gene polymorphism influence the incidence, development and outcome of preeclampsia. Subjects were recruited from 90 Korean patients with preeclampsia during pregnancy and 98 age-matched controls. After isolation of DNA, polymerase chain reactions (PCR) were carried out to detect polymorphism of the ACE and angiotensinogen. M235T and T174M genotypes of angiotensinogen were determined by digestion with restriction enzyme endonuclease Tth 111-I and NCo I, respectively. The frequency of DD genotype was significantly greater in preeclampsia (0.36) than in controls (0.14) (p<0.05). The frequency of D allele was 0.55 in preeclampsia and 0.40 in controls (p<0.05). There were no differences in the onset of preeclampsia and pregnancy outcomes according to the ACE genotypes. There was no difference in the frequency of a allele of angiotensinogen M235T between the groups (0.79:0.78 in preeclampsia : controls). The frequency of T allele of angiotensinogen T174M gene was slightly increased, but not significantly, in preeclampsia (0.11) than in controls (0.07). In a multivariate analysis, only ACE genotype was associated with the development of preeclampsia (beta=0.27, p=0.05). In conclusion, a molecular variant of ACE, but not angiotensinogen, gene is associated with preeclampsia in Korean women.

Genetics of preeclampsia: what are the challenges?

Despite recent efforts to identify susceptibility genes of preeclampsia, the genetic determinants of the condition remain ill-defined, as is the situation for most disorders of complex inheritance patterns. The angiotensinogen, factor V, and methylenetetrahydrofolate reductase genes have been investigated in different populations, as have other genes involved in blood pressure, vascular volume control, thrombophilia, lipid metabolism, oxidative stress, and endothelial dysfunction. The study of the genetics of complex traits is faced with both methodological and genetic issues; these include adequate sample size to allow for the identification of modest genetic effects, of gene-gene and gene-environment interactions, the study of adequate quantitative traits and extreme phenotypes, haplotype analyses, statistical genetics, genome-wide (hypothesis-free) versus candidate-gene (hypothesis-driven) approaches, and the validation of positive associations. The use of genetically well-characterized populations showing a founder effect, such as the French-Canadian population of Quebec, in genetic association studies, may help to unravel the susceptibility genes of disorders showing complex inheritance, such as preeclampsia. It is necessary to better evaluate the role of the fetal genome in the resulting predisposition to preeclampsia and its complications. Eventually, we may be able to integrate genetic information to better identify the women at risk of developing preeclampsia, and to improve the management of those suffering from this condition.

Molecular epidemiology of preeclampsia

Numerous articles have been published that address the possible genetic influences on the development of preeclampsia (PE). However, to our knowledge, a complete review of the results has not yet been completed. We undertook a MEDLINE search to identify English-language articles published after January 1, 1990 that examined the possible role of specific genes in the etiology of PE. After a brief introduction and a concise review of the prevailing etiologic hypotheses, we have categorized the candidate genes into six categories, based on their hypothesized role in PE etiology. The purpose of this paper is to review the literature, comment on its quality, and provide a reference for researchers interested in the molecular epidemiology of preeclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to list the prevailing etiologic hypotheses of preeclampsia, to outline the published data on possible genetic influence on the development of preeclampsia, and to clearly state the definition of preeclampsia.

Susceptibility loci for preeclampsia on chromosomes 2p25 and 9p13 in Finnish families

Preeclampsia is a common, pregnancy-specific disorder characterized by reduced placental perfusion, endothelial dysfunction, elevated blood pressure, and proteinuria. The pathogenesis of this heterogeneous disorder is incompletely understood, but it has a familial component, which suggests that one or more common alleles may act as susceptibility genes. We hypothesized that, in a founder population, the genetic background of preeclampsia might also show reduced heterogeneity, and we have performed a genomewide scan in 15 multiplex families recruited predominantly in the Kainuu province in central eastern Finland. We found two loci that exceeded the threshold for significant linkage: chromosome 2p25, near marker D2S168 (nonparametric linkage [NPL] score 3.77; P=.000761) at 21.70 cM, and 9p13, near marker D9S169 (NPL score 3.74; P=.000821) at 38.90 cM. In addition, there was a locus showing suggestive linkage at chromosome 4q32 between D4S413 and D4S3046 (NPL score 3.13; P=.003238) at 163.00 cM. In the present study the susceptibility locus on chromosome 2p25 is clearly different (21.70 cM) from the locus at 2p12 found in an Icelandic study (94.05 cM) and the locus at 2q23 (144.7 cM) found in an Australian/New Zealand study. The locus at 9p13 has been shown to be a candidate region for type 2 diabetes in two recently published genomewide scans from Finland and China. The regions on chromosomes 2p25 and 9p13 may harbor susceptibility genes for preeclampsia.

Searching for preeclampsia genes: the current position

Although there is substantial evidence that preeclampsia has a genetic background, the complexity of the processes involved and the fact that preeclampsia is a maternal-fetal phenomenon does not make the search for the molecular basis of preeclampsia genes easy. It is possible that the single phenotype 'preeclampsia' in fact should be divided into different sub-groups on genetic or biochemical level. In the present review, the preeclampsia phenotype and its pathophysiologic features are discussed. Family studies and postulated inheritance models are summarized. A systematic overview is given on the numerous candidate gene studies and gene-expression studies performed so far and on the currently available genome-wide scan data. Despite extensive research the molecular genetic basis of preeclampsia remains unclear. Future studies will hopefully enhance our insights in the molecular pathogenesis of preeclampsia.

Angiotensinogen gene M235T variant and pre-eclampsia in Romanian pregnant women

BACKGROUND

Association between the human angiotensinogen gene and essential hypertension has been confirmed in recent studies. Pre-eclampsia is a complication of pregnancy characterised by increased vascular resistance, high blood pressure, proteinuria and oedema, that appears in the second and third trimester of pregnancy. The aim of our study was the analysis of M235T mutation in the gene encoding angiotensinogen in Romanian women with different forms of hypertension during pregnancy.

METHODS

Fourteen women with obstetric complications were tested for M235T angiotensinogen gene mutation. Indications for testing were: severe or mild pre-eclampsia and pre-eclampsia associated with chronic hypertension. We also tested for control 6 healthy women. The M235T angiotensinogen gene mutation was analysed by polymerase chain reaction followed by enzymatic digestion with Tth 111I restriction endonuclease enzyme and agarose gel electrophoresis of the products.

RESULTS

Eleven (78.57%) of the 14 women with complications of pregnancy had M235T mutation: 9 (64.28%) were found to be heterozygous carriers of the M235T variant of the angiotensinogen gene and 2 (14.28%) were found to be homozygous carriers. In the group of women with normal pregnancy, 3 (50%) of the 6 women had M235T mutation: 2 (33.33%) were found to be heterozygous carriers of the M235T variant of the angiotensinogen gene and 1 (16.66%) was found to be homozygous carrier.

CONCLUSIONS

Our study shows that the M235T variant in the gene encoding angiotensinogen could be a risk factor in mild and severe pre-eclampsia.

A genome-wide scan for preeclampsia in the Netherlands

Preeclampsia, hallmarked by de novo hypertension and proteinuria in pregnancy, has a familial tendency. Recently, a large Icelandic genome-wide scan provided evidence for a maternal susceptibility locus for preeclampsia on chromosome 2p13 which was confirmed by a genome scan from Australia and New Zealand (NZ). The current study reports on a genome-wide scan of Dutch affected sib-pair families. In total 67 Dutch affected sib-pair families, comprising at least two siblings with proteinuric preeclampsia, eclampsia or HELLP-syndrome, were typed for 293 polymorphic markers throughout the genome and linkage analysis was performed. The highest allele sharing lod score of 1.99 was seen on chromosome 12q at 109.5 cM. Two peaks overlapped in the same regions between the Dutch and Icelandic genome-wide scan at chromosome 3p and chromosome 15q. No overlap was seen on 2p. Re-analysis in 38 families without HELLP-syndrome (preeclampsia families) and 34 families with at least one sibling with HELLP syndrome (HELLP families), revealed two peaks with suggestive evidence for linkage in the non-HELLP families on chromosome 10q (lod score 2.38, D10S1432, 93.9 cM) and 22q (lod score 2.41, D22S685, 32.4 cM). The peak on 12q appeared to be associated with HELLP syndrome; it increased to a lod score of 2.1 in the HELLP families and almost disappeared in the preeclampsia families. A nominal peak on chromosome 11 in the preeclampsia families showed overlap with the second highest peak in the Australian/NZ study. Results from our Dutch genome-wide scan indicate that HELLP syndrome might have a different genetic background than preeclampsia.

Pregnancy outcomes and community health: the POUCH study of preterm delivery

In light of the social/ethnic disparity in preterm delivery (PTD) rates, the Pregnancy Outcomes and Community Health (POUCH) Study takes a broad view of the determinants of PTD by attempting to link underlying biological and psychosocial factors. The relationships between placental pathology, maternal biomarkers, and antecedent psychosocial factors are evaluated in three hypothesised pathways of PTD - one characterised primarily by infection, one by maternal vascular disease, and one by premature elevations in corticotropin releasing hormone in the absence of histological evidence of placental pathology. Within each pathway, an emphasis is placed on understanding the roles of stress and of maternal serum alpha-fetoprotein, an early biomarker associated with PTD. The POUCH Study enrolls pregnant women from five Michigan communities. Information about these women and their environments is gathered through detailed interviews and collection of biological samples including hair, urine, saliva, blood, vaginal fluid, and vaginal smear at 15-26 weeks of gestation. We have chosen to focus on the second trimester--a time when pathological processes may have evolved to a detectable stage, but generally before the onset of biological changes that accompany labour. This focus is consistent with the long-range goal of early detection/intervention and prevention of PTD.

Angiotensinogen and endothelial nitric oxide synthase gene polymorphisms among Hispanic patients with preeclampsia

OBJECTIVE

We sought to establish an association between preeclampsia and the methionine to threonine polymorphism at amino acid residue 235 (Met235Thr) in angiotensinogen in a Hispanic population. We looked for a relationship between this allele and the allele in the endothelial nitric oxide synthase gene (NOS3) that produces the A form (NOS3*A) with respect to preeclampsia.

STUDY DESIGN

Clinical data were collected from 87 patients with preeclampsia and 53 control subjects. Patients and controls were genotyped for the angiotensinogen polymorphism allele (AGT*T) and the NOS3*A polymorphism. We then compared patients with preeclampsia and control subjects and investigated disease severity within the preeclampsia group as a function of genotype.

RESULTS

The AGT*T allelic frequencies among patients with preeclampsia and control subjects were 0.72 and 0.70, respectively (P =.84). The blood pressure of patients with an AGT*T allele who also carried a NOS3*A allele was higher at earlier gestational ages (r = -0.052; P =.02). Analysis suggested that the systolic blood pressure differences were due to gestational age effects and the presence of a NOS3*A allele (P <.10).

CONCLUSION

The AGT*T allele was not associated with the development of preeclampsia. Independently of the presence of an AGT*T allele, the NOS3*A allele was associated with a higher blood pressure at an earlier gestational age.

A genome scan in families from Australia and New Zealand confirms the presence of a maternal susceptibility locus for pre-eclampsia, on chromosome 2

Epidemiological studies have shown that genetic factors contribute to the etiology of the common and serious pregnancy-specific disorder pre-eclampsia (PE)/eclampsia (E). Candidate-gene studies have provided evidence (albeit controversial) of linkage to several genes, including angiotensinogen on 1q42-43 and eNOS on 7q36. A recent medium-density genome scan in Icelandic families identified significant linkage to D2S286 (at 94.05 cM) on chromosome 2p12 and suggestive linkage to D2S321 (at 157.5 cM) on chromosome 2q23. In the present article, the authors report the results of a medium-density genome scan in 34 families, representing 121 affected women, from Australia and New Zealand. Multipoint nonparametric linkage analysis, using the GENEHUNTER-PLUS program, showed suggestive evidence of linkage to chromosome 2 (LOD=2.58), at 144.7 cM, between D2S112 and D2S151, and to chromosome 11q23-24, between D11S925 and D11S4151 (LOD=2.02 at 121.3 cM). Given the limited precision of estimates of the map location of disease-predisposing loci for complex traits, the present finding on chromosome 2 is consistent with the finding from the Icelandic study, and it may represent evidence of the same locus segregating in the population from Australia and New Zealand. The authors propose that the PE/E-linked locus on chromosome 2p should be designated the "PREG1" (pre-eclampsia, eclampsia gene 1) locus.

Current topic: the uteroplacental renin-angiotensin system

The components of the renin-angiotensin system (RAS) are expressed in the uteroplacental unit. The expression varies between species, probably due to the marked species differences in placental architecture. The conditions for angiotensin (Ang) II formation exist and Ang II receptors are present throughout the human uteroplacental unit, indicating the presence of a functional local RAS. The uteroplacental RAS interacts with other regulatory systems and in this way modulates various aspects of tissue function. It is suggested that the uteroplacental RAS is important for the regeneration of the endometrium after shedding, and for decidualization, implantation and placentation. The RAS participates in the regulation of the uteroplacental blood flow, prostaglandin synthesis and oestradiol secretion. Disturbances of the uteroplacental RAS may lead to dysfunctional bleeding and to reduced uteroplacental blood flow in pregnancies complicated by pre-eclampsia and intrauterine growth retardation.

The L10F mutation of angiotensinogen is rare in pre-eclampsia

BACKGROUND

A mutation in the gene for angiotensinogen, changing the leucine residue at position 10 to a phenylalanine (L10F), has been reported in a patient with proteinuric pre-eclampsia. In vitro enzymatic studies suggest this mutation would increase production of the vasoactive peptide, angiotensin II in vivo, and therefore explain the etiology of the maternal hypertension.

OBJECTIVE

To determine whether mutation of codon 10 of angiotensinogen is common in pre-eclampsia, and therefore likely to be involved in disease susceptibility.

DESIGN

We collected a cohort of 32 women with 'true' pre-eclampsia. All were normotensive prior to the 20th week of pregnancy, developed blood pressures consistently above 140/90 mmHg and had proteinuria of greater than 300 mg/day during the third trimester. All had blood pressures that returned to normal within 1 month of delivery; 31 women were primigravida. Genomic DNA was isolated from their peripheral blood lymphocytes for genetic analyses.

METHODS

A polymerase chain reaction-restriction enzyme-based assay was devised to screen for mutation of codon 10 of the angiotensinogen gene. In addition, we determined the frequency of a threonine residue at position 235 in the angiotensinogen gene, given previous controversial findings of association of this polymorphism with disease.

CONCLUSIONS

We detected no mutation of codon 10 in angiotensinogen in any of the 32 women studied, indicating that this mutation is not commonly associated with proteinuric pre-eclampsia. Furthermore, there was no increased frequency of threonine 235 in the affected individuals studied compared with respective normotensive Caucasian-American and African-American populations.

Factor V Leiden and thermolabile methylenetetrahydrofolate reductase gene variants in an East Anglian preeclampsia cohort

Preeclampsia is a heritable condition that develops as a result of widespread vascular endothelial dysfunction. The thrombotic tendency in this condition has suggested a number of candidate genes, and there have been recent reports of positive association with the Leiden variant of factor V and the thermolabile variant of methylenetetrahydrofolate reductase. We attempted to reproduce these results in a large cohort of well-characterized women with preeclampsia, recruited prospectively within the East Anglian region of the United Kingdom. Women in the preeclampsia cohort (n=283) were genotyped for both the Leiden variant (G1691A) of factor V and the thermolabile variant (C677T) of methylenetetrahydrofolate reductase. Genotype and allele frequencies were compared with those of 2 control groups, one consisting of women recruited prospectively (n=100) from the same maternity hospital as the subjects and another consisting of normotensive women (n=100) from East Anglia. No significant differences were detected. Specifically, the carrier rate for the Leiden variant was 5.3% in the preeclampsia group and 5. 5% in the combined control group. T677 homozygotes for methylenetetrahydrofolate reductase were 11% and 11.5% in the 2 groups, respectively. We conclude that there is no evidence of association of preeclampsia with either of these 2 polymorphisms in our study population.

Angiotensinogen variants and human hypertension

The research on molecular genetics of human hypertension aims to identify the loci involved in the regulation of blood pressure, detect gene variants within the identified loci, associate them with intermediate phenotypes, and ultimately estimate their quantitative effects on blood pressure level and their interaction with main environmental factors. So far, the angiotensinogen (AGT) gene is one of the few candidate genes that has been investigated using these multiple statistical, clinical, and biochemical strategies. A highly polymorphic dinucleotide GT repeat (80% heterozygosity) has been used in several linkage studies. Other diallelic polymorphisms, located in the 5' regulatory region of the gene in intronic and exonic sequences, have been described, which were then used in association studies in different clinical settings. Positive associations between the M235T and the G-6A polymorphisms and plasma angiotensinogen levels indicates a pathway by which the AGT locus could be involved in essential hypertension.