The M235T Variant of the Angiotensinogen Gene Is Related to Development of Self-Reported Hypertension during Pregnancy: The Prospect-EPIC Cohort Study

Genetic Appraisal of RAAS-Associated SNPs: REN (rs16853055), AGT (rs3789678) and ACE (rs4305) in Preeclamptic Women Living with HIV Infection

PURPOSE OF REVIEW

The primary goal of this review article was to determine whether the three RAAS-associated SNPs, Renin-rs16853055, AGT-rs3789678 and ACE-rs4305 are genetically linked to the development of hypertension in preeclampsia. The secondary goal was to establish if there was a link between these SNPs and HIV infection.

RECENT FINDINGS

There is a paucity of findings related to the aforementioned SNPs and preeclampsia. There are no recent findings on the rs16853055 renin polymorphism. The rs3789678 angiotensinogen polymorphism correlated significantly with gestational hypertension. The rs4305 ACE polymorphism showed no significant association with the development of pregnancy-induced hypertension. There are conflicting findings when determining the relationship between ethnicity and the predisposition of preeclampsia and hypertension in relation to the discussed RAAS-associated SNPs. To date, the association between RAAS-associated SNPs and preeclamptic women co-morbid with HIV in South Africa has revealed that certain alleles of the AGT gene are more prominent in HIV-infected PE compared to normotensive pregnant HIV-infected women.

Comparative risks and predictors of preeclamptic pregnancy in the Eastern, Western and developing world

Preeclampsia (PE) is a complication of pregnancy characterized by hypertension (HTN-Preg), and often proteinuria. If not managed promptly, PE could lead to eclampsia and seizures. PE could also lead to intrauterine growth restriction (IUGR) and prematurity at birth. Although PE is a major cause of maternal and fetal morbidity and mortality, the underlying mechanisms are unclear. Also, there is a wide variability in the incidence of PE, ranging between 2 and 8% of pregnancies in the Eastern, Western and Developing world, suggesting regional differences in the risk factors and predictors of the pregnancy-related disorder. Several demographic, genetic, dietary and environmental factors, as well as maternal circulating biomarkers have been associated with PE. Demographic factors such as maternal race and ethnicity could play a role in PE. Specific genetic polymorphisms have been identified in PE. Maternal age, parity, education and socioeconomic status could be involved in PE. Dietary fat, protein, calcium and vitamins, body weight, and environmental factors including climate changes and air pollutants could also play a role in PE. Several circulating cytoactive factors including anti-angiogenic factors and cytokines have also been associated with PE. Traditional midwifery care is a common practice in local maternity care units, while advanced perinatal care and new diagnostic tools such as uterine artery Doppler velocimetry have been useful in predicting early PE in major medical centers. These PE risk factors, early predictors and diagnostic tools vary vastly in different regions of the Eastern, Western and Developing world. Further understanding of the differences in the demographic, genetic, dietary and environmental factors among pregnant women in different world regions should help in designing a region-specific cluster of risk factors and predictors of PE, and in turn provide better guidance for region-specific tools for early detection and management of PE.

Epidemiology of hypertensive disorders in pregnancy: prevalence, risk factors, predictors and prognosis

Hypertensive disorders in pregnancy (HDP) represent some of the most important problems faced by public health because HDP is a major cause of maternal and prenatal morbidity and mortality. Several epidemiological studies have been performed to determine the prevalence and risk factors of HDP as well as its subtypes. The prevalences of HDP, gestational hypertension and preeclampsia are 5.2-8.2%, 1.8-4.4% and 0.2-9.2%, respectively. Body mass index, anemia and lower education appear to be modifiable risk factors for HDP. Maternal age, primiparous, multiple pregnancy, HDP in previous pregnancy, gestational diabetes mellitus, preexisting hypertension, preexisting type 2 diabetes mellitus, preexisting urinary tract infection and a family history of hypertension, type 2 diabetes mellitus and preeclampsia appear to be nonmodifiable risk factors. Genetic variants including a single-nucleotide polymorphism in the angiotensinogen gene have also been reported to be nonmodifiable risk factors. Epidemiological studies have recently examined the associations between a history of HDP and its subtypes and future risks of other diseases. These studies have reported associations between a history of HDP and a risk of coronary heart disease, heart failure, dysrhythmia, stroke, hypertension, diabetes mellitus, end-stage renal dysfunction and cardiomyopathy. HDP is not associated with the future incidence of total cancer. In conclusion, HDP is not a rare complication of pregnancy and the influence of HDP remains for an extended duration. Physicians should consider the effects of HDP when treating chronic diseases in women.

Genetic, immune and vasoactive factors in the vascular dysfunction associated with hypertension in pregnancy

INTRODUCTION

Preeclampsia (PE) is a major complication of pregnancy that could lead to maternal and fetal morbidity and mortality. The pathophysiological mechanisms of PE are not completely understood, but recent research has begun to unravel some of the potential mechanisms.

AREAS COVERED

Genetic polymorphisms and altered maternal immune response may cause impaired remodeling of the spiral arteries; a potential early defect in PE. Inadequate invasion of cytotrophoblasts into the decidua leads to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia causes the release of biologically active factors such as anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and angiotensin II receptor autoantibodies. These vasoactive factors could cause systemic vascular endotheliosis and consequent increase in vascular resistance and blood pressure, glomerular endotheliosis causing proteinuria, cerebrovascular endotheliosis causing cerebral edema, seizures and visual disturbances, and hepatic endotheliosis, which may contribute to the manifestations of HELLP syndrome. PE-associated vascular endotheliosis causes a decrease in vasodilator mediators such as nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor, an increase in vasoconstrictors such as endothelin-1, angiotensin II and thromboxane A2, and enhanced mechanisms of vascular smooth muscle contraction such as intracellular Ca(2+), protein kinase C and Rho-kinase. Changes in matrix metalloproteinase activity and extracellular matrix cause vascular remodeling and further vasoconstriction.

EXPERT OPINION

Some of the genetic, immune and vasoactive factors involved in vascular endotheliosis could be used as biomarkers for early detection, and as potential targets for prevention and treatment of PE.

Bioactive factors in uteroplacental and systemic circulation link placental ischemia to generalized vascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-associated disorder characterized by hypertension, and could lead to maternal and fetal morbidity and mortality; however, the pathophysiological mechanisms involved are unclear. Predisposing demographic, genetic and environmental risk factors could cause localized abnormalities in uteroplacental cytoactive factors such as integrins, matrix metalloproteinases, cytokines and major histocompatibility complex molecules leading to decreased vascular remodeling, uteroplacental vasoconstriction, trophoblast cells apoptosis, and abnormal development of the placenta. Defective placentation and decreased trophoblast invasion of the myometrium cause reduction in uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia, an important event in preeclampsia. RUPP could stimulate the release of circulating bioactive factors such as the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin that cause imbalance with the pro-angiogenic factors vascular endothelial growth factor and placental growth factor, or cause the release of inflammatory cytokines, reactive oxygen species, hypoxia-induced factor-1 and AT1 angiotensin receptor agonistic autoantibodies. The circulating bioactive factors target endothelial cells causing generalized endotheliosis, endothelial dysfunction, decreased vasodilators such as nitric oxide and prostacyclin and increased vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction. The bioactive factors also stimulate the mechanisms of VSM contraction including Ca(2+), protein kinase C, and Rho-kinase and induce extracellular matrix remodeling leading to further vasoconstriction and hypertension. While therapeutic options are currently limited, understanding the underlying mechanisms could help design new interventions for management of preeclampsia.

Gene polymorphisms of adducin GLY460TRP, ACE I/D, AND AGT M235T in pediatric hypertension patients

BACKGROUND

Hypertension is a major global public health problem that affects both pediatric and adult populations. ACE I/D, AGT M235T, and ADD Gly460Trp polymorphisms are thought to be associated with primary hypertension. In the present study, we examined the frequency of these polymorphisms in a pediatric population with secondary hypertension.

MATERIAL AND METHODS

Included in the study were 58 hypertensive and 58 normotensive pediatric patients. ACE I/D and AGT M235T polymorphisms are determined by conventional PCR; ADD Gly460Trp polymorphism was investigated using PCR amplification of genomic DNA.

RESULTS

There were significant differences between the control group and pediatric hypertensive group in terms of ACE I/D (P<0.05) and AGT M235T (P<0.05) polymorphisms, but there were no differences in ADD Gly460Trp (P>0.05) polymorphism.

CONCLUSIONS

We suggest that RAS gene polymorphisms (ACE-I/D, AGT M235T) are significantly associated with susceptibility to diseases that lead to secondary hypertension.

The role of the renin-angiotensin-aldosterone system in preeclampsia: genetic polymorphisms and microRNA

The compensatory alterations in the rennin-angiotensin-aldosterone system (RAAS) contribute to the salt-water balance and sufficient placental perfusion for the subsequent well-being of the mother and fetus during normal pregnancy and is characterized by an increase in almost all the components of RAAS. Preeclampsia, however, breaks homeostasis and leads to a disturbance of this delicate equilibrium in RAAS both for circulation and the uteroplacental unit. Despite being a major cause for maternal and neonatal morbidity and mortality, the pathogenesis of preeclampsia remains elusive, where RAAS has been long considered to be involved. Epidemiological studies have indicated that preeclampsia is a multifactorial disease with a strong familial predisposition regardless of variations in ethnic, socioeconomic, and geographic features. The heritable allelic variations, especially the genetic polymorphisms in RAAS, could be the foundation for the genetics of preeclampsia and hence are related to the development of preeclampsia. Furthermore, at a posttranscriptional level, miRNA can interact with the targeted site within the 3'-UTR of the RAAS gene and thereby might participate in the regulation of RAAS and the pathology of preeclampsia. In this review, we discuss the recent achievements of genetic polymorphisms, as well as the interactions between maternal and fetal genotypes, and miRNA posttranscriptional regulation associated with RAAS in preeclampsia. The results are controversial but utterly inspiring and attractive in terms of potential prognostic significance. Although many studies suggest positive associations with genetic mutations and increased risk for preeclampsia, more meticulously designed large-scale investigations are needed to avoid the interference from different variations.

Maternal/newborn genotype contribution of the renin–angiotensin system (Met235Thr, Thr174Met, I/D-ACE, A2350G-ACE, A1166C-AT2R1, C3123A- AT2R2, 83A/G-REN) to the risk of pre-eclampsia: a Romanian study

Introduction: We evaluated the association of the mutated genotypes Met235Thr-AGT, Thr174Met-AGT, I/D-ACE, A2350G-ACE, A1166C-AT2R1, C3123A-AT2R2, 83A/G-REN with the risk and outcome of pre-eclampsia; we also investigated whether genes in newborns increase maternal risk of pre-eclampsia.

Materials and methods: Thirty-six pairs of pre-eclamptic women and their newborns were genotyped, along with 71 pairs of controls (mothers/newborns) using PCR-RFLP analysis.

Results: The Thr235/Thr235 (OR 3.44, p = 0.01), DD (OR 2.66, p = 0.039), CC1166 (OR 5.56, p = 0.04), AA3123 (OR 3.77, p = 0.03) and GG83 (OR 8.32, p = 0.006) genotypes are significantly associated with pre-eclampsia. Women with pre-eclampsia positive for Met235Thr (34.64 ± 3.92 weeks vs. 38 ± 2 weeks), Thr174Met (32.58 ± 3.92 weeks vs. 36.38 ± 3.25 weeks), I/D (34.47 ± 3.67 weeks vs. 38.33 ± 3.5 weeks) delivered at a significant lower gestational age compared with pre-eclamptic women with a normal genotype. Newborns from women with pre-eclampsia positive for Thr174Met (2190 ± 820.21 g vs. 2702.08 ± 967.23 g), I/D (2399.33 ± 938.38 g vs. 3191.66 ± 684.40 g) had a significant lower birth weight compared with newborns from women with normal pregnancies. When both the mother and the newborn were positive for Met235Thr, I/D, A2350G, A1166C or 83A/G polymorphisms, the risk for pre-eclampsia was significantly increased at 6.67 ( p < 0.01), 5 ( p < 0.01), 3.33 ( p = 0.006), 2.72 ( p = 0.04) and 7.8 ( p < 0.01), respectively.

Conclusions: The results of our study confirm that, in pre-eclampsia, both maternal and newborn genetic variations implicated in blood pressure regulation are important.

Molecular and vascular targets in the pathogenesis and management of the hypertension associated with preeclampsia

Normal pregnancy is associated with significant hemodynamic changes and vasodilation of the uterine and systemic circulation in order to meet the metabolic demands of the mother and developing fetus. Preeclampsia (PE) is one of the foremost complications of pregnancy and a major cause of maternal and fetal mortality. The pathophysiological mechanisms of PE have been elusive, but some parts of the puzzle have begun to unravel. Genetic factors such as leptin gene polymorphism, environmental and dietary factors such as Ca(2+) and vitamin D deficiency, and co-morbidities such as obesity and diabetes may increase the susceptibility of pregnant women to develop PE. An altered maternal immune response may also play a role in the development of PE. Although the pathophysiology of PE is unclear, most studies have implicated inadequate invasion of cytotrophoblasts into the uterine artery, leading to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia induces the release of biologically active factors such as growth factor inhibitors, anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and antibodies to vascular angiotensin II (AngII) receptor. These bioactive factors could cause vascular endotheliosis and consequent increase in vascular resistance and blood pressure, as well as glomerular endotheliosis with consequent proteinuria. The PE-associated vascular endotheliosis could be manifested as decreased vasodilator mediators such as nitric oxide, prostacyclin and hyperpolarizing factor and increased vasoconstrictor mediators such as endothelin-1, AngII and thromboxane A₂. PE could also involve enhanced mechanisms of vascular smooth muscle contraction including intracellular Ca(2+), and Ca(2+) sensitization pathways such as protein kinase C and Rho-kinase. PE-associated changes in the extracellular matrix composition and matrix metalloproteinases activity also promote vascular remodeling and further vasoconstriction in the uterine and systemic circulation. Some of these biologically active factors and vascular mediators have been proposed as biomarkers for early prediction or diagnosis of PE, and as potential targets for prevention or treatment of the disease.

Risk factors and mediators of the vascular dysfunction associated with hypertension in pregnancy

Normal pregnancy is associated with significant hemodynamic changes and vasodilation in the uterine and systemic circulation in order to meet the metabolic demands of the mother and developing fetus. Hypertension in pregnancy (HTN-Preg) and preeclampsia (PE) are major complications and life-threatening conditions to both the mother and fetus. PE is precipitated by various genetic, dietary and environmental factors. Although the initiating events of PE are unclear, inadequate invasion of cytotrophoblasts into the uterine artery is thought to reduce uteroplacental perfusion pressure and lead to placental ischemia/hypoxia. Placental hypoxia induces the release of biologically active factors such as growth factor inhibitors, anti-angiogenic proteins, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and antibodies to vascular angiotensin II receptor. These bioactive factors affect the production/activity of various vascular mediators in the endothelium, smooth muscle and extracellular matrix, leading to severe vasoconstriction and HTN. As an endothelial cell disorder, PE is associated with decreased vasodilator mediators such as nitric oxide, prostacyclin and hyperpolarizing factor and increased vasoconstrictor mediators such as endothelin, angiotensin II and thromboxane A(2). PE also involves enhanced mechanisms of vascular smooth muscle contraction including intracellular free Ca(2+) concentration ([Ca(2+)](i)), and [Ca(2+)](i) sensitization pathways such as protein kinase C, Rho-kinase and mitogen-activated protein kinase. Changes in extracellular matrix composition and matrix metalloproteases activity also promote vascular remodeling and further vasoconstriction in the uterine and systemic circulation. Characterization of the predisposing risk factors, the biologically active factors, and the vascular mediators associated with PE holds the promise for early detection, and should help design specific genetic and pharmacological tools for the management of the vascular dysfunction associated with HTN-Preg.

G protein-coupled receptor kinase 4 gene variants are not associated with preeclampsia in Northern Han Chinese

Genetic variations in preeclampsia (PE) may affect PE risk. The G protein-coupled receptor kinase 4 (GRK4) gene encodes a member of the Ser/Thr protein kinase family and has been linked to both genetic and acquired hypertension. The aim of this study was to investigate the association between polymorphisms (T-rs1024323-C and T-rs1801058-C) in GRK4 and PE in Northern Han Chinese. Using a case-control design, the association between the GRK4 exon-4 T-rs1024323-C and exon-13 T-rs1801058-C polymorphisms and the risk of PE in Northern Han Chinese was assessed in 105 individuals with PE and 103 age- and area-matched normotensive controls. Genotypes were determined by allelic discrimination. The odds ratio and 95% confidence interval were estimated by binary logistic regression. No association was found between the GRK4 polymorphisms (T-rs1024323-C and T-rs1801058-C) and PE, and there was also no relationship with the severity of PE. The risk of homozygous and heterozygous variant allele carriers of the analyzed single-nucleotide polymorphisms did not differ significantly from that of the homozygous wild-type allele carriers, even after adjustment for age, body mass index, (family) history of hypertension and smoking status. The GRK4 (T-rs1024323-C and T-rs1801058-C) polymorphisms were not associated with a risk of PE in the present Northern Han Chinese study group. Thus, the GRK4 polymorphisms do not seem to have an important role in PE in this population.

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.

Fetal sex determines the impact of maternal PROGINS progesterone receptor polymorphism on maternal physiology during pregnancy

BACKGROUND

Recent evidence from very rare human diseases suggests that variation in the fetal genome can modify maternal physiology during pregnancy. Here, we tested the hypothesis that fetal sex as a major genetic variant of the fetal genome may affect maternal physiology during pregnancy in genetically susceptible pregnant women.

METHODS

We analyzed the impact of fetal sex on maternal physiology during pregnancy in relationship with the maternal PROGINS progesterone receptor gene polymorphism. Two thousand and eighty-nine (2089) Caucasian women without preexisting diabetes and preexisting hypertension with singleton pregnancies delivering consecutively at the Charité obstetrics department participated in this study.

RESULTS

The maternal PROGINS progesterone receptor polymorphism on its own had no effect on blood pressure, new onset of proteinuria, and total glycated hemoglobin at delivery. However, by considering the offspring's sex, the AA variant of the PROGINS progesterone receptor polymorphism was associated with profound cardiovascular/metabolic effects; mothers carrying both A alleles (AA genotype) delivering a boy had significantly lower systolic blood pressure during the first trimester of pregnancy versus AA mothers delivering girls (107.9+/-10.2 vs. 116.6+/-15.1 mmHg, P = 0.044). Diastolic blood pressure was similarly lower during the first trimester of pregnant AA women delivering boys in comparison with AA women delivering girls (63.4+/-5.7 vs. 68.2+/-10.9 mmHg, P = 0.032). Total glycated hemoglobin at delivery was significantly (P = 0.002) higher in AA mothers delivering boys (6.6+/-0.7%) versus AA mothers delivering girls (5.9+/-0.6%).

CONCLUSION

Our study indicates that fetal sex may substantially affect maternal blood pressure as well as glycemic control during pregnancy in genetically susceptible mothers.