No association of the Asp298 variant of the endothelial nitric oxide synthase gene with preeclampsia

Association of endothelial nitric oxide synthase gene variants in pre-eclampsia: an updated systematic review and meta-analysis

INTRODUCTION

Three common endothelial nitric oxide synthase (eNOS) gene variants are existed such as; G-894T, T-786C, and variable number tandem repeats in intron-4 (VNTR intron-4) which has been proposed to be linked with PE. However, there is still debate regarding the findings. To address this, a review was conducted to assess the potential association of eNOS gene variants at these positions with the risk of PE.

METHODS

PubMed, Scopus, Science Direct, Hinari, and African Journal Online databases and Google Scholar search engines were utilized to search studies published in English-language until 30 January 2023. The Joanna Briggs Institute Meta-Analysis instrument was used for data extraction process and the Newcastle-Ottawa Scale was used to appraise the quality of the included studies. Meta-regression analysis was conducted using Stata 14 statistical software. The pooled odds ratios (ORs) of fixed and random effect models were utilized to evaluate the association of eNOS gene polymorphism with the risk of PE at 95% CI. Publication bias was assessed using Egger's test and a funnel plot.

RESULTS

The study included 47 observational studies involving 13,795 pregnant women (6216 cases and 7579 controls). Pregnant women carrying TT and CC genotypes of eNOS gene at 894 and 786 positions were found to have a greater probability of developing PE as compared to GG and TT genotypes (OR = 1.54 vs. 1.43 and CI: 1.12 - 2.14 vs.1.02 - 2.00 at 95% CI), respectively. However, a significant association was not observed between aa genotype of eNOS gene in VNTR intron-4 region and risk of PE as compared to bb genotype (OR =1.26, 95% CI: 0.83 - 1.89). The allelic model of eNOS gene at all positions showed nonsignificant association with the risk of PE.

CONCLUSIONS

The women having eNOS gene variants at 894 and 786 positions showed a significant association with the risk of PE. Yet, the women having eNOS gene variant at intron-4 region showed nonsignificant association with the risk of PE. Thus, this study suggests that eNOS gene variants may play a role in the development of PE, but large-scale studies are required to inaugurate concrete evidence on the roles of eNOS gene variants in PE pathogenesis.

The eNOS-G894T genetic polymorphism and risk of preeclampsia: A case-control study, an updated meta-analysis, and a bioinformatic assay

OBJECTIVES

Preeclampsia (PE) is a leading cause of maternal death worldwide and involves vascular endothelial dysfunction. The aim of this study was to investigate the association of the G894T polymorphism in the endothelial nitric oxide synthase (eNOS) gene and the risk of preeclampsia in a case-control design in an Iranian population, which was followed by a meta-analysis and an in silico approach.

METHODS

In the case-control study, 300 people including 135 pregnant women with preeclampsia and 165 healthy pregnant women were included. The genotype of G894T polymorphism was determined by the PCR-RFLP method. We searched authoritative scientific databases to find eligible studies for meta-analysis. The odds ratio with a 95% confidence interval was estimated to find the strength of the association of the mentioned polymorphism with the risk of preeclampsia. In addition, the effect of G894T transversion on eNOS gene function was evaluated by some bioinformatics tools.

RESULTS

Our case-control data showed that the G894T polymorphism is associated with an increased risk of preeclampsia. In the meta-analysis, 33 eligible studies were included, and the results showed that the G894T polymorphism is associated with an increased risk of preeclampsia in the overall analysis and some stratified analyses. In addition, the structural analysis showed that the G894T variant can affect the splicing process as well as the protein stability.

CONCLUSIONS

Based on the results, the aforementioned polymorphism may be a risk factor for preeclampsia and could be considered a potential molecular biomarker for screening susceptible individuals.

Association of Endothelial Nitric Oxide Synthase 894G > T Polymorphism with Preeclampsia Risk: A Systematic Review and Meta-Analysis based on 35 Studies

Several case-control studies have been performed to investigate the association between 894 G > T polymorphism in endothelial nitric oxide synthase (eNOS) gene and susceptibility to preeclampsia. However, the results were inconsistent and inconclusive. Therefore, we conducted this meta-analysis to investigate the association. Methods: All studies published up to September 30, 2019 were identified by searching electronic databases such as PubMed, EMBASE, CNKI, and WANFANG. Results: A total of 35 case- control studies with 4,254 cases and 5,801 controls were selected. There was a significant association between the eNOS 894 G > T and preeclampsia risk. When stratified by ethnicity, an increased risk of preeclampsia was found in Caucasian and Mixed populations, but not in Asians or Africans. Conclusion: Based on our meta-analysis, the eNOS 894 G > T polymorphism was associated with an increased risk of preeclampsia, especially among Caucasian and Mixed populations.

Association Between Endothelial Nitric Oxide Synthase (eNOS) -786 T/C and 27-bp VNTR 4b/a Polymorphisms and Preeclampsia Development

The aim of the present study was to analyze the distribution of genotypes and haplotypes of functional eNOS gene polymorphisms in the promoter (-786 T/C), intron 4 (VNTR4b/a) and exon 7 (894 G/T), in Serbian population of pregnant women, and establish a possible association between these polymorphisms and preeclampsia development. DNA was isolated from venous blood samples of 50 heathy pregnant women and 50 preeclampsia patients. Polymerase Chain Reaction/Restriction Fragment Length Polymorphism (PCR/RFLP) technique, with appropriate sets of primers and specific restriction enzymes, was used to determine polymorphisms in eNOS gene. Statistical analysis was done using the SPSS and HAPLOVIEW software packages. eNOS -786 T/C polymorphism was significantly associated with preeclampsia (P = 0.006). Homozygotes for the VNTR polymorphism had also an elevated risk of developing preeclampsia (OR=7.68, 95%CI (0.89-65.98)), especially the mild (OR=9.33, 95%CI (0.98-88.57)) and late form (OR=8.52, 95%CI (0.90-80.58)). The 894 G/T polymorphism was not associated with preeclampsia. "G-C-b" and "T-4a-T" haplotypes were more frequent in preeclampsia, though without reaching statistical significance. -786 T/C and VNTR 4b/a eNOS gene polymorphisms were associated with preeclampsia risk in Serbian patients.

Maternal/fetal eNOS-Glu298Asp genotypes and their influence on the severity, prognosis, and lipid profile of preeclampsia

OBJECTIVES

To analyze the contribution of maternal eNOS-Glu298Asp genotypes and also the association with fetal genotypes to the development of preeclampsia, prognosis, and maternal dyslipidemia.

METHODS

Sixty-nine pairs of preeclamptic mothers/newborns and 94 pairs of normotensive mothers/newborns were genotyped for eNOS-Glu298Asp using PCR-RFLP methods.

RESULTS

Women carriers of at least one Asp298 allele had a 1.53-fold (p = NS), 1.88-fold (p = NS), and 2.08-fold (p = .05), respectively, increased risk to develop PIH, mild, or severe preeclampsia. If both the mother and the newborn were carriers of the Asp298 allele, the risk for preeclampsia was 5.09-fold higher (p < .001). Preeclamptic women with severe preeclampsia had significantly higher cholesterol (mg/dl, 287.23 ± 43.01 versus 235.36 ± 45.01, p = .02) and LDL (mg/dl, 194.9 ± 42.8 versus 144.98 ± 54.84, p = .04) levels and lower HDL levels (mg/dl, 32.12 ± 5.48 versus 57.84 ± 20.59, p = .02) compared to noncarriers. Also, higher LDL levels (mg/dl, 188.76 ± 46.61 versus 136.75 ± 41.85, p = .03) and lower HDL levels (mg/dl, 32.8 ± 5.64 versus 61.06 ± 22.45, p = .02) were found in preeclamptic women with severe preeclampsia whose newborns were carriers of the Asp298 allele.

CONCLUSIONS

The eNOS-Glu298Asp variant (in mothers and newborns) in association with dyslipidemia could affect bioavailability of NO and could represent an increased risk for preeclampsia.

Polymorphisms in the Endothelial Nitric Oxide Synthase Gene May Be Protective Against Preeclampsia in a Chinese Population

The association between the endothelial nitric oxide synthase (eNOS) gene with vascular diseases in Western populations and with severe preeclampsia (PE) in the Japanese population have been demonstrated, lacing the data in Chinese population. The authors examine the association between PE and 2 polymorphisms of the eNOS gene in a Chinese population, consisting of 92 pregnant women with PE and 256 healthy controls. All were genotyped for the Glu298Asp polymorphism in exon 7 and the number of 27 base pair repeats in intron 4 of the eNOS gene. The frequencies of both the variant T allele and eNOS 4a (small allele with 4 repeats of 27 bp) were significantly lower in the PE group than in the control group. The genotype distribution of Glu298Glu, Glu298Asp, and Asp298Asp in eNOS exon 7 and bb type and ab type in eNOS intron 4 revealed statistically significant differences between control and PE groups. This is the first study to evaluate the association between 2 polymorphisms in the maternal eNOS gene with PE simultaneously in a Chinese population. Similar to the findings in Western populations, polymorphisms in the eNOS gene may be protective against PE in a Chinese population, in contrast to the results in the Japanese population.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

Association of Nitric Oxide Synthase and Matrix Metalloprotease Single Nucleotide Polymorphisms with Preeclampsia and Its Complications

Background

Preeclampsia is one of the leading causes of maternal and neonatal morbidity and mortality in the world, but its appearance is still unpredictable and its pathophysiology has not been entirely elucidated. Genetic studies have associated single nucleotide polymorphisms in genes encoding nitric oxide synthase and matrix metalloproteases with preeclampsia, but the results are largely inconclusive across different populations.

Objectives

To investigate the association of single nucleotide polymorphisms (SNPs) in NOS3 (G894T, T-786C, and a variable number of tandem repetitions VNTR in intron 4), MMP2 (C-1306T), and MMP9 (C-1562T) genes with preeclampsia in patients from Southeastern Brazil.

Methods

This prospective case-control study enrolled 77 women with preeclampsia and 266 control pregnant women. Clinical data were collected to assess risk factors and the presence of severe complications, such as eclampsia and HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome.

Results

We found a significant association between the single nucleotide polymorphism NOS3 T-786C and preeclampsia, independently from age, height, weight, or the other SNPs studied, and no association was found with the other polymorphisms. Age and history of preeclampsia were also identified as risk factors. The presence of at least one polymorphic allele for NOS3 T-786C was also associated with the occurrence of eclampsia or HELLP syndrome among preeclamptic women.

Conclusions

Our data support that the NOS3 T-786C SNP is associated with preeclampsia and the severity of its complications.

Endothelial nitric oxide synthase (eNOS) gene Glu298Asp polymorphism and expression in North Indian preeclamptic women

BACKGROUND

Pathophysiological processes in preeclampsia (PE) are influenced by genetic factors, nitric oxide synthases seem to play important roles, although their expression in and their role is still unclear. To better characterize the host genetic factors determining the susceptibility to PE, we evaluated the influence of polymorphisms (Glu298Asp) in the endothelial nitric oxide synthase (eNOS) gene on the risk of developing PE by checking the expression level.

METHODS

We conducted a hospital-based case-control study including 300 women with preeclampsia and 200 healthy pregnant women. Their blood samples were analyzed for levels of nitric oxide, eNOS gene polymorphism and expression. eNOS mRNA levels were determined using RT-PCR and expressed as arbitrary units after correction with control β-Actin gene mRNA levels.

RESULTS

The mRNA expression of eNOS gene was found to be significantly lower in blood (P<0.05) from women with PE compared to that from normal pregnancies. The total nitric oxide levels (P<0.001) were decreased in study Group as compared to healthy pregnant patients. The intergenotypic variation of nitric oxide levels in preeclamptic women was found to be significant (P<0.001).

CONCLUSIONS

These results indicate the relationship between reduced nitric oxide levels and eNOS gene polymorphism leading to its altered expression in preeclamptic women.

The polymorphism for endothelial nitric oxide synthase gene, the level of nitric oxide and the risk for pre-eclampsia: a meta-analysis

Endothelial NO, which is synthesized by endothelial nitric oxide synthase (eNOS), has been reported to be related with the occurrence of pre-eclampsia (PE). However, the polymorphisms of eNOS (-786 T>C, 4b/a and G894T), the level of nitric oxide and the risk of PE remain unclear. Thus we performed this meta-analysis to determine the associations between them in order to predict the risk for PE and interference with PE development in the early period of antenatal care. All studies investigating the associations between PE risk and polymorphisms of eNOS, or PE risk and serum concentration of NO were reviewed. Finally, 29 studies were included, involving 11 for -786 T>C, 11 for 4b/a, and 22 for G894T polymorphisms and PE risk. In the overall analysis, -786 T>C polymorphism was found to be related with increased PE risk in the dominant model (OR=1.17, 95% CI=1.02-1.35). a allele for 4b/a suffers the high risk of PE (OR=1.46, 95% CI=1.01-2.10). In the subgroup analysis, significantly increased risk was detected among Europeans for -786 T>C polymorphism (OR=1.40, 95%CI=1.14-1.73).However, no significant association was detected for G894T polymorphism in the overall and subgroup analysis. The comprehensive evaluation of 9 available studies indicated that serum NO level was significantly decreased in case group (SMD=-0.96 umol/mL, 95%CI=-1.80, -0.12 umol/mL).Hence, we concluded that eNOS gene -786 T>C and 4b/a except for G894T polymorphisms were contributed significantly to PE risk, especially for Europeans, and a low NO concentration in serum increased the risk for PE.

eNOS tag SNP haplotypes in hypertensive disorders of pregnancy

Haplotypes formed by polymorphisms (T-786C, rs2070744; a variable number of tandem repeats in intron 4, and Glu298Asp, rs1799983) of the eNOS gene were associated previously with gestational hypertension (GH) and preeclampsia (PE). However, no study has explored the Tag SNPs rs743506 and rs7830 in these disorders. The aim of the current study was to compare the distribution of the genotypes and haplotypes formed by the five eNOS polymorphisms mentioned among healthy pregnant (HP, n=122), GH (n=138), and PE (n=157). The haplotype formed by "C b G G C" was more frequent in HP compared to GH and PE (p=0.0071), which is supported by previous findings that demonstrated the association of the combination "C b G" with a higher level of nitrite (NO marker). Our results suggest a protective effect of the haplotype "C b G G C" against the development of hypertensive disorders of pregnancy.

FOLATE METABOLISM AND PREECLAMPSIA

Preeclampsia (PE) is a multisystem disorder of human pregnancy, affecting about 6% of all pregnancies worldwide, and is one of the leading causes of maternal and infant morbidity and mortality. Despite decades of research into the pathogenesis of this complex disease, the underlying mechanisms remain unclear. As a result, the options for prevention and management of PE are limited. In recent years, there has been a growing body of evidence suggesting that folate deficiency is associated with PE, and folic acid supplementation may reduce the risk of developing PE in certain populations. Folate contributes to cell division and growth, and folate metabolism is involved in a large number of physiological and pathophysiological processes in human development. Sufficient supply of folate is therefore particularly important during pregnancy. Nevertheless, the exact mechanisms of folic acid deficiency increasing the risk of developing PE are still unclear. This article reviews what is understood about the aetiology of PE and the relationship between folate metabolism and PE so as to enhance further discussions on the subject.

The effect of maternal and fetal β2-adrenoceptor and nitric oxide synthase genotype on vasopressor requirement and fetal acid-base status during spinal anesthesia for cesarean delivery

BACKGROUND

Previous work demonstrated that maternal haplotypes of the β₂-adrenoceptor gene (ADRB2) influence ephedrine requirements during cesarean delivery. The use of ephedrine versus a pure α-adrenergic agonist such as phenylephrine has been associated with lower umbilical artery (UA) pH, thought to be secondary to increased fetal metabolism. There are no data evaluating the effect of fetal/neonatal genotypes on the metabolic response to maternally administered vasopressors. We hypothesized that neonatal ADRB2 genotype would affect the extent of neonatal acidemia. We also examined the effect of maternal ADRB2 and the endothelial nitric oxide synthase gene (NOS3) on ephedrine and phenylephrine requirements for treatment of maternal hypotension.

METHODS

The study was performed on 104 Chinese women scheduled for cesarean delivery under spinal anesthesia who were participating in a double-blind randomized clinical trial evaluating the maternal and neonatal effects of ephedrine versus phenylephrine infusions. Blood samples were drawn from the UA, umbilical vein, and maternal radial artery to measure blood gas values and lactate, ephedrine, and phenylephrine concentrations, and to determine maternal and neonatal genotype at nonsynonymous single nucleotide polymorphisms at codons 16 (rs1042713) and 27 (rs1042714) of ADRB2 and codon 298 (rs1799983) of NOS. Clinical variables (UA pH, UA lactate, and dose of vasopressors) among genotypes were compared, and regression models were created to assess the effect of genotype on vasopressor dose and fetal acid-base status.

RESULTS

Maternal ADRB2 genotype did not affect the ephedrine dose. Neonatal genotype at codon 16 influenced fetal acid-base status. UA pH was higher in Arg16 homozygous neonates (7.31 ± 0.03 in p.16Arg/Arg vs. 7.25 ± 0.11 in p.16 Arg/Gly and p.16 Gly/Gly; P < 0.001, 95%confidence interval (CI) of difference 0.03 ~ 0.09) and UA lactate was lower (2.67 mmol/L ± 0.99 in p.16Arg/Arg vs 4.28 mmol/L ± 2.79 in. p.16 Arg/Gly and p.16 Gly/Gly; P < 0.001, 95% CI of difference -2.40 ~ -0.82). In neonates born to mothers receiving ephedrine, the magnitude of the difference among genotypes was even greater (pH 7.30 ± 0.02 in p.16Arg/Arg vs. 7.19 ± 0.10 in p.16 Arg/Gly and p.16 Gly/Gly; P < 0.001, 95% CI of difference 0.07 ~ 0.14) and UA lactate was lower (3.66 mmol/L ± 1.30 in p.16Arg/Arg vs. 5.79 mmol/L ± 2.88 in p.16 Arg/Gly and p.16 Gly/Gly; P = 0.003, 95% CI of difference -3.48 ~ -0.80). In a multiple linear regression model (R² = 63.6%; P = 0.03), neonatal ADRB2 genotypes (p.16Arg/Arg and p.27Gln/Glu) and lower neonatal birth weight predicted lower UA lactate concentrations. Phenylephrine dose was not affected by maternal ADRB2 or NOS3 genotypes, and neonatal NOS3 genotype did not affect UA pH or UA lactate.

CONCLUSION

In contrast to previous findings in a North American cohort, maternal ADRB2 genotype did not affect ephedrine requirements during elective cesarean delivery in a Chinese cohort. However, our findings suggest that neonatal ADRB2 p.Arg16 homozygosity confers a protective effect against developing ephedrine-induced fetal acidemia.

Oxidative stress and eNOS (Glu298Asp) gene polymorphism in preeclampsia in Indian population

Oxidative stress causing widespread endothelial dysfunction has been proposed as a key factor involved in the development of preeclampsia (PE). With this background our objective was to study oxidative stress biomarkers like nitric oxide and malondialdehyde (MDA) and to correlate these markers with endothelial nitric oxide synthase (eNOS) (Glu298Asp) gene polymorphism. This cross-sectional study included 300 pregnant women diagnosed with PE and 200 women with normal pregnancy. Plasma NO and MDA levels were analyzed using student's t test and eNOS gene polymorphism was studied by performing polymerase chain reaction amplification and restriction length polymorphism and frequencies were distributed by using χ(2) analysis. The mean plasma levels of NO were significantly lower in study group while MDA levels were significantly higher in study group (P < 0.001). Genotypic and allelic frequency of eNOS gene in both groups was found to be significant (P < 0.05). The intergenotypic variation of NO and MDA levels was found to be significant (P < 0.001). We concluded that the plasma levels of NO are decreased while MDA levels are increased in subjects with PE and that might contribute to the pathophysiology of PE. As observed in this study Glu298Asp eNOS gene polymorphism showed significant association with PE.

Variable effects of maternal and paternal-fetal contribution to the risk for preeclampsia combining GSTP1, eNOS, and LPL gene polymorphisms

Objective

To evaluate the maternal, paternal, and fetal genotype contribution to preeclampsia.

Study design, materials, and methods

We combined the analysis of polymorphisms of the GSTP1, eNOS, and LPL genes – affecting biotransformation enzymes and endothelial function – in a cohort of 167 preeclamptic and normal control trios (mother, father, and child) comprising a total of 501 samples in the Greek population, never analyzed before by this approach.

Results

For the frequency of the GSTP1 Ile¹⁰⁵/Val¹⁰⁵, the eNOS Glu298Asp and the LPL-93 polymorphisms, statistically significant differences were found between the two groups. However, the transmission rates of the parental alleles to neonates studied by the transmission disequilibrium test, disclosed no increased rate of transmission to preeclampsia children for the variant alleles of Val¹⁰⁵ GSTP1, 298Asp eNOS, and -93G LPL.

Conclusions

These novel data, suggest that interaction of all three types of genotypes (mother, father and neonate), reveals no effects on the development of preeclampsia, but provide the impetus for further studies to decipher the individual contribution of each genetic parameter of preeclampsia.

The significance of -786T > C polymorphism of endothelial NO synthase (eNOS) gene in severe preeclampsia

OBJECTIVE

Preeclampsia (PE) is believed to be induced by endothelial cell dysfunction in placenta. Highly polymorphic endothelial nitric oxide synthase (eNOS) activity belongs to the factors significantly influencing vaso-motor tone in placenta and PE susceptibility. The aim of this study was to evaluate prevalence of -786T/C polymorphism of eNOS gene in the groups of women with mild and severe PE.

STUDY DESIGN

The study was performed in the group of 218 preeclamptic (including 136 with severe PE) and of 400 normotensive healthy women delivered normally after a healthy gestation. The eNOS -786T/C polymorphism was determined using PCR/RFLP assay. Additionally, detailed correlation between eNOS genotypes and clinical/laboratory data in the PE group has been analyzed.

RESULTS

The higher frequency of mutated homozygous CC genotypes (17.4% vs. 11.5% in controls, OR 1.62, n.s.) and of C alleles (allelic frequency 44.1 vs. 36.6%; OR 1.36, p = 0.012) in the group of PE has been determined. Furthermore, in the group of severe PE the overrepresentation of mutated CC genotypes (23.5% vs. 11.5%, OR 2.37, p = 0.0014) and mutated C alleles (47.8 vs. 36.6%, OR 1.58, p = 0.0016) has been found.

CONCLUSIONS

The presence of mutated homozygous CC genotype and C allele of -786T/C polymorphism of eNOS gene influences the higher susceptibility to develop severe PE development.

Endothelial nitric oxide synthase, angiotensin-converting enzyme and angiotensinogen gene polymorphisms in hypertensive disorders of pregnancy

We investigated the variations in genes encoding endothelial nitric oxide synthase (NOS3), angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) in hypertensive disorders of pregnancy and the relationship between the polymorphisms and circulating nitric oxide (NO) and ACE levels in pregnant north Indian women. Frequencies of NOS3 G894T, 4b/a and T(-786) --> C, AGT T704C and ACE ins/del polymorphisms were studied in 342 subjects: 120 with preeclampsia (PE), 104 with gestational hypertension and 118 normotensive pregnant women. Variations were evaluated by polymerase chain reaction-restriction fragment length polymorphism. NO and ACE levels were determined using ELISA. There was no difference in the distribution of individual NOS3 and ACE polymorphisms in the study groups. Haplotype analysis showed a global difference in the NOS3 haplotype distribution between the PE and non-PE subjects (P=0.03). The presence of AGT 704C allele was associated with a reduced risk of developing PE (odds ratio: 0.33, 95% CI: 0.19-0.59 in recessive mode). Circulating total NO and ACE levels were similar in three groups. No relationship was found between circulating NO levels and any of the NOS3 polymorphisms, but the circulating ACE levels were higher in those with DD genotype (P<0.05). In conclusion, there was no association between individual NOS3 and the ACE gene polymorphisms and hypertensive disorders of pregnancy in north Indian women. The presence of minor alleles at all the three sites in NOS3 seemed to increase the risk of PE, and AGT 704C allele was associated with a reduced PE risk. The complexity of interaction between these genetic abnormalities requires further studies.

4G/5G variant of plasminogen activator inhibitor-1 gene and severe pregnancy-induced hypertension: subgroup analyses of variants of angiotensinogen and endothelial nitric oxide synthase

Background

Pregnancy-induced hypertension (PIH) is a common cause of perinatal mortality. It is believed to result from the interaction of several factors, including those related to the blood coagulation system. We performed genotyping and subgroup analyses to determine if the 4G/5G genotypes of the plasminogen activator inhibitor-1 gene (PAI-1) play a role in the pathogenesis of PIH, and to evaluate possible interactions of the PAI-1 polymorphisms with those of the angiotensinogen gene (AGT) and the endothelial nitric oxide synthase gene (NOS3).

Methods

An association study of PAI-1 polymorphism, and subgroup analyses of common variants of AGT and NOS3, among 128 patients with PIH and 376 healthy pregnant controls.

Results

No significant differences were found between the cases and controls in the frequencies of allele 4G or the 4G/4G genotype. In subgroup analyses, after adjustment for multiple comparison, a significant association with the AGT TT genotype was found among women with the PAI-1 4G/4G genotype, and an association with the NOS3 GA+AA genotype was found among women with the 5G/5G or 4G/5G genotypes.

Conclusions

Our findings suggest that there are at least 2 pathways in the pathogenesis of severe PIH. However, with respect to early prediction and prevention of severe PIH, although the PAI-1 4G/4G genotype alone was not a risk factor for severe PIH, the fact that PAI-1 genotypes are associated with varying risks for severe PIH suggests that PAI-1 genotyping of pregnant women, in combination with other tests, may be useful in the development of individualized measures that may prevent severe PIH.

eNOS haplotypes associated with gestational hypertension or preeclampsia

AIMS

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been inconsistently associated with preeclampsia. We compared genotype and haplotype frequencies of three eNOS gene polymorphisms in normotensive and hypertensive pregnancies.

METHODS

Genotypes and haplotypes for eNOS polymorphisms (T-786C, Glu298Asp and intron 4 b/a) were determined in 326 pregnant women (110 healthy pregnancies, 103 gestational hypertensives and 113 preeclamptic).

RESULTS

No differences were observed in the frequencies of genotypes and alleles of the three polymorphisms among the groups (all p > 0.05). However, the haplotype 'T Glu a' was more common in healthy pregnancies than in gestational hypertensives or preeclamptic (20 vs 6 and 6%, respectively; p < 0.0032). Conversely, the haplotype 'C Glu a' was more common in gestational hypertensives and preeclamptic than in healthy pregnancies (17 vs 17 and 5%; p = 0.0061).

CONCLUSION

These findings suggest a contribution of eNOS haplotypes to the development of hypertensive disorders of pregnancy that is obscured when specific eNOS genotypes alone are considered.

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.

Endothelial nitric oxide synthase gene influences the risk of pre-eclampsia, the recurrence of negative pregnancy events, and the maternal-fetal flow

OBJECTIVES

Pre-eclampsia is associated with vascular endothelial dysfunction, adverse pregnancy outcome and cardiovascular disease in later life. An inadequate nitric oxide availability related to polymorphisms in the endothelial nitric oxide synthase gene (eNOS) might predispose to the disease.

METHODS

We investigated the role of eNOS T-786C, G894T and 4a4b polymorphisms in predisposing to both pre-eclampsia and the recurrence of negative pregnancy events, per se and in the presence of angiotensin-converting enzyme (ACE) DD genotype, and investigated their influence on maternal-fetal flow in 106 non-thrombophilic women with a history of pre-eclampsia, compared with 106 women with a history of normal pregnancy.

RESULTS

No association between eNOS polymorphisms and predisposition to pre-eclampsia was found; nevertheless, the contemporary presence of eNOS 894TT and -786CC genotypes represented a susceptibility factor to the disease. In 48 out of 106 women, documented complications (pre-eclampsia and fetal growth restriction) were present in the current pregnancy. The eNOS 894TT genotype influenced the risk of recurrence of negative events (odds ratio = 5.45), particularly in contemporary women homozygous for both eNOS 894TT and ACE DD genotypes (odds ratio = 11.4). Throughout the pregnancy, a progressive alteration of maternal-fetal flow indices was found in women carrying the eNOS 894TT genotype, and this effect was strengthened in women with the contemporary presence of the ACE DD genotype.

CONCLUSIONS

An original finding is the increased risk of pre-eclampsia and recurrence of pregnancy negative events, probably by modulating the maternal-fetal flow, in women homozygous for the eNOS 894T allele previously analyzed for the ACE I/D polymorphism.

Endothelial dysfunction: a link among preeclampsia, recurrent pregnancy loss, and future cardiovascular events?

We tested the hypothesis that endothelial dysfunction could cause placentation-related defects, persist after the complicated pregnancy, and probably cause cardiovascular disease later in life. Brachial arterial reactivity and factors related to endothelial dysfunction, such as circulating cholesterol, uric acid, nitrites, l-arginine, asymmetrical dimethylarginine, vascular endothelial growth factor, and soluble vascular endothelial growth factor receptor-1, in women with previous healthy pregnancies (n=22), patients with severe preeclampsia (n=25), or patients with recurrent pregnancy loss (n=29), at day 10 of the luteal phase of an ovulatory cycle an average of 11 to 27 months after pregnancy were evaluated. Both groups with placentation defects had a significant decrease in endothelium-dependent dilatation, a higher rate of endothelial dysfunction, lower serum nitrites, and higher cholesterol as compared with control subjects; subjects with previous preeclampsia additionally had higher normal blood pressures and a greater parental prevalence of cardiovascular disease. Patients with recurrent pregnancy loss also demonstrated a significantly lower endothelium-independent vasodilatation. A trend to an inverse correlation was found between serum cholesterol serum and endothelial-mediated vasodilatation in the whole study population. Uric acid, l-arginine, asymmetrical dimethylarginine, vascular endothelial growth factor, and soluble vascular endothelial growth factor receptor-1 were similar in all of the groups. We postulate that endothelial dysfunction may represent a link between preeclampsia and increased cardiovascular disease latter in life and propose that women with unexplained recurrent miscarriages are also at increased cardiovascular risk. The identification and correction of endothelial dysfunction detected during the reproductive stage on obstetric outcome and on cardiovascular diseases needs to be elucidated.

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.

Endothelial nitric oxide synthase gene polymorphism (Glu298Asp) and development of pre-eclampsia: a case-control study and a meta-analysis

BACKGROUND

Pre-eclampsia is thought to have an important genetic component. Recently, pre-eclampsia has been associated in some studies with carriage of a common eNOS gene Glu298Asp polymorphism, a variant that leads to the replacement of glutamic acid by aspartic acid at codon 298.

METHOD

Healthy women with singleton pregnancies were recruited from 7 district general hospitals in London, UK. Women at high risk of pre-eclampsia were screened by uterine artery Doppler velocimetry at 22-24 weeks of gestation and maternal blood was obtained to genotype the eNOS Glu298Asp polymorphism. Odds ratios (OR) and 95%CI, using logistic regression methods, were obtained to evaluate the association between the Glu298Asp polymorphism and pre-eclampsia. A meta-analysis was then undertaken of all published studies up to November 2005 examining the association of eNOS Glu298Asp genotype and pre-eclampsia.

RESULTS

89 women with pre-eclampsia and 349 controls were included in the new study. The Glu298Asp polymorphism in a recessive model was not significantly associated with pre-eclampsia (adjusted-OR: 0.83 [95%CI: 0.30-2.25]; p = 0.7). In the meta-analysis, under a recessive genetic model (1129 cases & 2384 controls) women homozygous for the Asp298 allele were not at significantly increased risk of pre-eclampsia (OR: 1.28 [95%CI: 0.76-2.16]; p = 0.34). A dominant model (1334 cases & 2894 controls) was associated with no increase of risk of pre-eclampsia for women carriers of the Asp298 allele (OR: 1.12 [95%CI: 0.84-1.49]; p = 0.42).

CONCLUSION

From the data currently available, the eNOS Glu298Asp polymorphism is not associated with a significant increased risk of pre-eclampsia. However, published studies have been underpowered, much larger studies are needed to confirm or refute a realistic genotypic risk of disease, but which might contribute to many cases of pre-eclampsia in the population.

The Glu298Asp variant of the endothelial nitric oxide synthase gene is associated with an increased risk for abruptio placentae in pre-eclampsia

Attempts to define a pre-eclampsia susceptibility profile have been hampered by the wide clinical spectrum of the condition and the complex genetics underlying it. Genes that modulate blood pressure, fluid homeostasis and placental vascular development have been considered plausible candidates. Among these are the angiotensinogen (AGT) gene variant Met235Threo, which has been associated with pre-eclampsia and the endothelial nitric oxide synthase (eNOS) polymorphism Glu298Asp, which has been associated with both pre-eclampsia and abruptio placentae, a condition that often co-exists with pre-eclampsia. The aim of this study was to investigate a potential association between these gene variants and pre-eclampsia with and without abruptio placentae in a South African patient group. Fifty primigravidas with early onset, severe pre-eclampsia, 50 women presenting primarily with abruptio placentae (whether associated with pre-eclampsia or not) and a control panel of 50 healthy pregnant women constituted the study groups. The Met235Threo and Glu298Asp variants were characterised by polymerase chain reaction and restriction enzyme analysis. No association was demonstrated between the M235T variant of the AGT gene and pre-eclampsia or abruptio placentae. In contrast, the combined frequency of the eNOS variant genotypes (GT and TT) was significantly higher in the abruptio placentae group (49%) than the control group (21%) (p=0.006). Furthermore, in the pre-eclampsia patients who subsequently developed abruptio placentae, the eNOS GT genotype emerged as a major risk factor for the development of abruptio placentae (p<0.0001). These data suggest that the presence of a Glu298Asp eNOS variant may pre-dispose a pre-eclamptic woman to develop abruptio placentae or that it is a marker for predisposition.

Reduced L-arginine level and decreased placental eNOS activity in preeclampsia

Nitric oxide is produced enzymatically by the nitric oxide synthase (NOS), which converts L-arginine in the presence of oxygen to L-citrulline and NO. Moreover, it has been reported that asymmetric dimethylarginine (ADMA) acts as is an endogenous inhibitor of endothelial NOS (eNOS) by competing with the enzyme for L-arginine. In this study, we measured L-arginine and ADMA in normal and preeclamptic women, and also investigated the association between the Glu298Asp eNOS gene polymorphism and preeclampsia. Finally, we assessed eNOS expression levels in the placentas of both normal and preeclamptic patients, using Western blot and immunohistochemistry. L-arginine levels were found to be significantly lower in the preeclamptic women than in the normal pregnant women (p=0.02) but there were no significant differences in ADMA levels between the normal and preeclamptic women. We also determined there to be no association between the Glu298Asp eNOS gene and preeclampsia. With regard to placental eNOS expression, we detected a lower degree of eNOS expression in the preeclamptic syncytiotrophoblasts than in the normal syncytiotrophoblasts. We suggest that reduced L-arginine levels, rather than increased ADMA levels, contribute to the development of preeclampsia, and also that decreased placental eNOS expression constitutes a characteristic finding in preeclamptic placentas.