A molecular variant of angiotensinogen associated with preeclampsia

Preeclampsia in North Indian women: the contribution of genetic polymorphisms

AIM

To find association of angiotensin-converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) T704C, methylenetetrahydrofolate reductase (MTHFR) C677T and factor V Leiden (FVL) G1691A polymorphisms with pre-eclampsia (PE) in North Indian women.

MATERIAL & METHODS

In this prospective case-control study, genotyping of 200 pre-eclamptic women and 200 normotensive pregnant controls was performed for the ACE I/D, AGT T/C,MTHFR C/T and FVL G/A polymorphisms. Statistical analysis was carried out using SPSS and Epi Info to estimate their association with PE. The association of these polymorphisms with nonsevere PE and severe PE was separately assessed.

RESULTS

The FVL mutation was found in 4% of women and increased the risk of PE twofold (odds ratio [OR] 2.08, P-value 0.03). The MTHFR mutant allele was found to be protective (OR 0.59, P-value 0.01). Both these polymorphisms showed similar association with nonsevere PE (OR 2.149, P-value 0.038 and OR 0.565, P-value 0.222, respectively) but not with severe PE. The ACE I/D and AGT T/C polymorphisms were not found to be associated with PE overall (OR 1.26, P-value 0.11 and OR 1.15, P-value 0.35, respectively), but ACE I/D polymorphism was found to increase the risk of severe PE (OR 1.53, P-value 0.019).

CONCLUSION

FVL mutation is more common in North Indians than previously believed and it predisposes the women to PE. MTHFR mutant allele is paradoxically protective. ACE polymorphism appears to predispose to severe PE but not nonsevere PE. No significant contribution of AGT polymorphism to PE is found.

Modulation of the BP response to diet by genes in the renin-angiotensin system and the adrenergic nervous system

BACKGROUND

Essential hypertension results from the interaction of several genetic and environmental factors. Identification of genetic factors that modulate blood pressure (BP) response to interventions can lead to improved strategies for prevention and control. The purpose of this study was to identify genes that modulate BP response to dietary interventions.

METHODS

We used data and samples collected in two randomized feeding studies to determine the extent to which genetic architecture is associated with the effect on BP of sodium intake and the Dietary Approaches to Stop Hypertension (DASH) dietary pattern. Participants in both trials were adults with above-optimal BP or unmedicated stage 1 hypertension. Genomic DNA was typed for several candidate genes.

RESULTS

The effect of sodium intake on BP differed by genotype at the angiotensinogen, β2-adrenergic receptor, and kallikrein loci. The effect of DASH dietary pattern on BP differed by genotype at the β2-adrenergic receptor locus.

CONCLUSIONS

These findings have implications for understanding the mechanism(s) through which diet affects BP, the heterogeneity of these effects, and the extent to which dietary interventions can modulate genetic predisposition.

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).

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.

Trophoblast function in normal and preeclamptic pregnancy

Preeclampsia (PE) is a common disease of pregnancy that affects women particularly in their first pregnancies. Current estimates suggest that between 7 and 10% of pregnancies may be complicated by PE. Despite considerable research and medical efforts, the incidence of the disease has not changed substantially in the last century. In severe cases the disease may be life-threatening and is associated with high neonatal mortality and morbidity. Furthermore, therapy is often ineffective and at best treats the disease symptoms rather than the aetiology. One reason for the lack of progress may be that while the disease is generally agreed by most to be due to abnormal implantation and development of the placenta (events which happen in the first trimester) most research efforts have focused on managing and understanding the maternal disease. Since the disease typically appears in the last trimester, many weeks after the likely start of the pathology, it has been difficult to understand the progression of events. However, this picture has improved recently. The purpose here is to review how placental development is affected in PE and describe new insights into the causes. It is hoped that an understanding of the pathogenesis of the placental defects in PE will lead to new efforts towards early diagnosis, before the onset of clinical symptoms, as well as new treatments for these lesions.

Environmental contributions to disparities in pregnancy outcomes

One of the most persistent disparities in American health status is the pronounced difference in birth outcomes between non-Hispanic black and non-Hispanic white women. Poor pregnancy outcomes have a substantial impact on mortality, morbidity, and health care costs. Increasing evidence indicates that environmental exposures are associated with poor birth outcomes. This paper reviews the latest research on how environmental exposures affect pregnancy outcomes and then discusses how these exposures may be embedded within a context of significant social and host factor stress. The analysis suggests that environmental, social, and host factors are cumulatively stressing non-Hispanic black women and that this cumulative stress may be a cause of the persistent disparities in pregnancy outcomes.

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.

Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1-7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy.

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.

Severe Preeclampsia is Associated with a Positive Family History of Hypertension and Hypercholesterolemia

OBJECTIVE

To investigate an association between a family history of cardiovascular disease and severe preeclampsia and/or HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets).

METHODS

One hundred twenty-eight women with a history of severe preeclampsia and/or HELLP syndrome and 123 women with previous uncomplicated pregnancies only were included in the study. All participants completed questionnaires about diagnoses of cardiovascular diseases, hypertension, and hypercholesterolemia among their first-degree relatives, which were subsequently confirmed by the relatives' general practitioners. The main outcome measures were the prevalence of cardiovascular diseases, hypertension, and hypercholesterolemia among first-degree relatives of both groups. Statistical analysis was done using chi(2)-analysis.

RESULTS

The prevalence of familial cardiovascular disease among women with a history of severe preeclampsia and/or HELLP syndrome (23%) compared to controls (19%) was not significantly different (OR 1.3, 95%CI 0.7-2.5). However, women with a history of severe preeclampsia and/or HELLP syndrome more often had one or more first-degree relatives with hypertension and/or hypercholesterolemia before the age of 60 years compared to controls (54% vs. 32%, respectively; OR 2.6, 95%CI 1.5-4.3). The prevalence of hypertension and hypercholesterolemia among first-degree relatives, irrespective of age, also was significantly higher among women with a history of severe preeclampsia and/or HELLP syndrome as compared to controls (60% vs. 42%, respectively; OR 2.0, 95%CI 1.2-3.4).

CONCLUSION

Severe preeclampsia is associated with a positive family history of hypertension and/or hypercholesterolemia.

Study of Association Between Hypertensive Disorders of Pregnancy and the Human Coagulation Factor XI Gene

OBJECTIVE

Hypertensive disorders of pregnancy (HDP) are among the most common and serious complications of pregnancy. Persuasive evidence implicaties genetic factors in the genesis of HDP. The aim of the present study was to assess the association between single-nucleotide polymorphisms (SNPs) in the human coagulation factor XI (F11) gene and HDP, by conducting a haplotype-based case-control study.

METHODS

We chose 3 SNPs (rs925453, rs925451, and rs12500151) in the human F11 gene as genetic markers. We then conducted an association study with 77 HDP patients and 154 age-matched non-HDP subjects.

RESULTS

The frequency of rs925453 genotypes significantly differed between the two groups. The frequency of the T-G-G haplotype was significantly higher in the HDP group than in the non-HDP group (p = 0.0002).

CONCLUSIONS

The T allele of rs925453 and the T-G-G haplotype appear to be useful genetic markers of HDP.

Angiotensin-Converting Enzyme Insertion/Deletion (ACE I/D) and Angiotensin II Type 1 Receptor (AT1R) Gene Polymorphism and Its Association with Preeclampsia in Chinese Women

OBJECTIVE

To investigate whether polymorphisms of angiotensin converting enzyme gene (ACE) and angiotensin II receptor type 1 gene (AT1R) are associated with etiology of preeclampsia and renal impact in women with preeclampsia.

METHODS

DNA was extracted from peripheral blood of 133 patients with preeclampsia and 105 healthy pregnant women. The I/D polymorphism of the ACE gene was assessed by polymerase chain reaction, and the A1166C polymorphism of the AT(1)R gene was additionally assessed by DdeI digestion. The level of proteinuria, fasting serum urea, creatinine and uric acid were investigated according to different genotypes of ACE and AT1R genes.

RESULTS

The frequency of genotypes of the ACE gene and the AT1R gene was similar in preeclampsia and normal pregnancy. DD and ID genotype predominated in patients with severe proteinuria, as well as increased serum urea and uric acid. Serum creatinine was also increased, but no significant difference was found among three genotypes. The level of proteinuria, serum uric acid, urea, and creatinine did not vary between different AT1R genotypes. Compared with patients without renal dysfunction, the frequency of DD and ID genotypes of ACE gene was much higher in those with renal dysfunction, but AC and CC genotypes of AT1R gene were not.

CONCLUSION

We found no association of the two gene polymorphisms with preeclampsia. However, ACE gene I/D polymorphisms were associated with the severe proteinuria and renal dysfunction seen in preeclampsia. Preeclampsia patients carrying the D allele may be susceptible to renal dysfunction.

Genetic thrombophilia variants and risk for preeclampsia among American Indians

OBJECTIVE

To determine the prevalence of thrombophilic genetic variants in an American Indian population and determine if they are associated with preeclampsia.

METHODS

A total of 87 cases, 165 controls and an additional 75 population-based controls were genotyped for two thrombophilic polymorphisms.

RESULTS

The allelic prevalence of the factor V Leiden and 20210 G/A prothrombin variants in this population was 2.1% and 0.5% respectively. No statistically significant associations between these genetic variants and preeclampsia were found.

CONCLUSION

The prevalence of thrombophilic variants is of possible public health significance for other morbidity; but perhaps not in relation to preeclampsia.

Genotype distribution of estrogen receptor alpha polymorphisms in pregnant women from healthy and preeclampsia populations and its relation to blood pressure levels

BACKGROUND

The estrogen receptor alpha gene (ESR1) seems to be a potential candidate in altering risk for preeclampsia due to important estrogenic biological effects. Despite its previously reported association with severe preeclampsia in combined genotype in one selected ethnic group, further studies in other populations are required. The objective of this study was to investigate the relationship of the gene polymorphisms of the estrogen receptor alpha with preeclampsia in a southwest Chinese population.

METHODS

We genotyped two polymorphisms in the ESR1 gene (PvuII and XbaI) by polymerase chain reaction-restriction fragment length polymorphism analysis in a Chinese population.

RESULTS

In the case-control study which included 204 preeclampsia case subjects and 236 normal control subjects, the frequencies of allele T for the PvuII site and allele G for the XbaI site in the patients (41.67% and 23.53%, respectively) were similar to those observed in controls (43.01% and 19.70%, respectively). Furthermore, the combined genotype analysis of ESR1 PvuII and XbaI polymorphisms showed no increased risk of either severe or total preeclampsia in our study populations. However, it showed that the CC homozygotes and CT heterozygotes in control pregnant women had higher systolic blood pressure levels than TT homozygotes for the PvuII site after adjustment for age and body mass index (p<0.05).

CONCLUSIONS

Our work does not provide evidence in favor of ESR1 PvuII and XbaI being associated with preeclampsia but with increased blood pressure levels in normal pregnant women, in a southwest Chinese population.

Comparison between essential hypertension and pregnancy-induced hypertension: a genetic perspective

Essential hypertension (EH) accounts for 80-90% of hypertension, and pregnancy-induced hypertension (PIH) is responsible for hypertension during pregnancy. Both considered multifactorial disorders. While both have many features in common, conditions and causes of these diseases have yet to be clarified. Since both diseases are associated with hypertension, the genetic backgrounds may contain common features. The present study reviewed similarities and differences between women with EH and PIH, with a particular focus on their genetic backgrounds.

Preeclampsia risk and angiotensinogen polymorphisms M235T and AGT -217 in African American and Caucasian women

INTRODUCTION

Genetic variants of the angiotensinogen gene have been linked to both hypertension and preeclampsia. The M235T polymorphism is more common in hypertension and preeclampsia in some populations. A polymorphism in the angiotensinogen basal promoter region of AGT -217 is more common in African Americans with hypertension. The authors investigated the frequency of M235T and AGT -217 in Caucasian and African American women with and without preeclampsia.

METHODS

The study was a nested case-control study of primiparous women with singleton pregnancies. Genomic DNA from preeclamptic and control subjects underwent polymerase chain reaction amplification and restriction digestion.

RESULTS

The M235T and AGT -217 polymorphisms were both more common in African American women; however, the variants were not more common in preeclampsia.

CONCLUSION

The frequency of angiotensinogen polymorphisms M235T and AGT -217 is different by race; however, these polymorphisms are not associated with an increased risk of preeclampsia.

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.

HAEMODYNAMIC CONTRIBUTIONS TO THE PATHOGENESIS OF PREECLAMPSIA AND ECLAMPSIA

Current hypotheses regarding the origins of preeclampsia have focused on the “Two stage model”. This model suggests that the primary steps in the pathophysiologic sequence of preeclampsia are initiated by abnormal placentation including the classic finding of abnormal trophoblast invasion of maternal decidual spiral arteries. The second stage of the sequence includes the elaboration of a single or multiple substances from these disordered placentas which contribute to the generalized maternal systemic illness, eventually manifesting as endothelial injury, hypertension and proteinuria. Recent studies have focused on the role of pro and anti-angiogenic peptides as potential placentally derived aetiologic agents in this pathophysiologic sequence, although other placental products have been highlighted in recent research. Despite the fact that this modeling of preeclampsia has widespread support significant limitations to this hypothesis can be identified.

The M235T polymorphism in the angiotensinogen gene is associated with the risk of malignant hypertension in white patients

BACKGROUND

Malignant hypertension can be considered an extreme phenotype of renin-mediated hypertension. Therefore, we compared the allelic frequencies of the angiotensinogen (AGT) M235T, angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensin II-type I receptor (AT1R) A1166C polymorphisms in malignant hypertensive patients with hypertensive and normotensive controls.

METHODS

A total of 101 consecutive patients between 1995 and 2005 admitted to a large university hospital fulfilled the criteria for malignant hypertension. Seventy-five patients (74%) were compared with 150 hypertensive and 150 normotensive controls, randomly selected from a population study and individually matched on age, sex and ethnicity.

RESULTS

The odds of malignant hypertension in white subjects with the TT genotype of the AGT M235T polymorphism was 14.3 (5.5-37) compared to hypertensive controls, and 9.4 (3.8-23.2) compared to normotensive controls. Adjustment for age, sex, smoking and antihypertensive therapy did not affect this association. The association of AGT M235T with malignant hypertension was not significant in blacks. In patients with malignant hypertension, the TT genotype was associated with more severe renal dysfunction and microangiopathic haemolysis. No differences were found in allele frequencies of the ACE I/D or the AT1R A1166C polymorphisms between study groups.

CONCLUSIONS

The TT genotype of AGT M235T is associated with malignant hypertension in whites, carriers having an odds of approximately 10 to 1 compared to hypertensive and normotensive controls. These observations may provide a better understanding of the pathophysiology of malignant hypertension and offer possibilities for identifying patients at risk. Larger association or linkage studies are needed for a more detailed risk assessment.

Gene polymorphisms of the renin-angiotensin-aldosterone system and angiotensin II type 1-receptor activating antibodies in renal rejection

Steroid refractory acute rejection (SRAR) is a major vital factor in renal transplantation recipients. The pathogenesis of SRAR may involve both immune and non-immune mechanisms. A decreased renal allograft function has also been associated with increased activity of renin-angiotensin-aldosterone system (RAS), which may be genetically determined. A total 206 renal transplant recipients, 116 males and 90 females, were included. The effects of gene polymorphisms of the four components of RAS including angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin type 1 receptor (AT1R), and aldosterone synthase (CYP11B2) were investigated in 19 cases of renal transplant patients with SRAR. The association between SRAR and the activating antibodies targeting the AT1R were also investigated. Genotyping was performed for the M235T-AGT, the I/D-ACE, the A1166C-AT1R, and the -344T/C-CYP11B2 gene polymorphisms using polymerase chain reaction. Our results showed that renal allograft recipients with SRAR had significantly higher occurrences of the DD genotype of ACE and CC genotype of AT1R than recipients without SRAR. The other genetic polymorphisms of the RAS were not associated with SRAR. Activating antibodies targeting the AT1R were detected in the sera from 14 SRAR victims with malignant hypertension and without anti-HLA antibodies. This study provides evidence that determination before transplantation of the polymorphism of the gene encoding components of RAS may help identify patients who are at risk for SRAR. The detection of the antibodies of AT1R may contribute to the prevention of SRAR.

Vascular endothelial growth factor gene +936 C/T polymorphism is associated with preeclampsia in Korean women

OBJECTIVE

The purpose of this study was to evaluate potential associations between vascular endothelial growth factor (VEGF) gene polymorphisms and preeclampsia.

STUDY DESIGN

One hundred ten patients with preeclampsia and 209 healthy pregnant control subjects were enrolled in the study. After peripheral blood was obtained from all women and the genomic DNA was isolated, we genotyped +936C/T polymorphisms in the 3'-untranslated region of the VEGF gene, using polymerase chain reaction and restriction fragment length polymorphism techniques.

RESULTS

The distribution of genotypes of the +936C/T polymorphism was significantly different between women with preeclampsia and the control group (P < .001). Carriage of the +936T allele was significantly more frequent in preeclamptic patients than in control subjects (odds ratio, 2.06; 95% CI,1.38-3.08). Logistic regression analysis on VEGF genotype and clinical parameters such as age, educational status, body mass index, and neonatal gender showed carriage of the 936T allele to be significantly more frequent in preeclamptic patients than in control subjects (adjusted odds ratio, 2.23; 95% CI, 1.46-3.42).

CONCLUSION

Carriage of the +936T allele of the VEGF gene may be associated with increased susceptibility to the development of preeclampsia and may be an independent risk factor for preeclampsia.

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.

Angiotensinogen M235T and T174M Gene Polymorphisms in Combination Doubles the Risk of Mortality in Heart Failure

Angiotensinogen M235T and T174M polymorphisms have individually been associated with elevated levels of plasma angiotensinogen, hypertension, and left ventricular hypertrophy. In this study, heart failure patients (n=451) were genotyped for the angiotensinogen M235T and T174M polymorphisms to investigate association with survival (recorded over 4 years of follow-up) and prognostic hormone markers. Patients carrying the 235TT genotype (n=86) were 3 years younger at admission ( P =0.011), and, in those with hypertension, diagnosis was made ≈10 years earlier than other patients. Patients carrying ≥1 174M allele (n=94) were more likely to have a previous history of heart failure ( P =0.044) and increased mortality during follow-up (risk ratio: 1.69, 95% CI: 1.03 to 2.79; P =0.038) compared with 174TT homozygotes (n=355), despite having a higher left ventricular ejection fraction ( P =0.009). “High-risk” genotype combinations (defined a priori as 235TT and/or ≥1 174M allele; n=144; 32%) were independently predictive of mortality, conferring a 2-fold greater risk of dying during the follow-up period (odds ratio: 2.0; 95% CI: 1.3 to 3.0; P =0.001). This study suggested that angiotensinogen gene variants M235T and T174M may provide prognostic information for long-term survival in heart failure patients.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Genetic susceptibility to essential hypertension: insight from angiotensinogen

Although progress in the genetics of essential hypertension may seem disappointing, it has considerable potential in defining research directions that will ultimately translate into clinical practice. The hypothesis that genetic variation at the angiotensinogen locus impacts on individual susceptibility to develop essential hypertension has motivated a substantial body of research by us and many others. We examine how analyses of the mechanisms by which variation in angiotensinogen expression may contribute to disease susceptibility and may have arisen in human populations have progressed in recent years. Although the objective of personalized medicine is still in the future, a genetic hypothesis based on human variation can uniquely empower functional genomics approaches to reach such an ultimate goal.

Candidate-gene association study of mothers with pre-eclampsia, and their infants, analyzing 775 SNPs in 190 genes

Pre-eclampsia (PE) affects 5-7% of pregnancies in the US, and is a leading cause of maternal death and perinatal morbidity and mortality worldwide. To identify genes with a role in PE, we conducted a large-scale association study evaluating 775 SNPs in 190 candidate genes selected for a potential role in obstetrical complications. SNP discovery was performed by DNA sequencing, and genotyping was carried out in a high-throughput facility using the MassARRAY(TM) System. Women with PE (n = 394) and their offspring (n = 324) were compared with control women (n = 602) and their offspring (n = 631) from the same hospital-based population. Haplotypes were estimated for each gene using the EM algorithm, and empirical p values were obtained for a logistic regression-based score test, adjusted for significant covariates. An interaction model between maternal and offspring genotypes was also evaluated. The most significant findings for association with PE were COL1A1 (p = 0.0011) and IL1A (p = 0.0014) for the maternal genotype, and PLAUR (p = 0.0008) for the offspring genotype. Common candidate genes for PE, including MTHFR and NOS3, were not significantly associated with PE. For the interaction model, SNPs within IGF1 (p = 0.0035) and IL4R (p = 0.0036) gave the most significant results. This study is one of the most comprehensive genetic association studies of PE to date, including an evaluation of offspring genotypes that have rarely been considered in previous studies. Although we did not identify statistically significant evidence of association for any of the candidate loci evaluated here after adjusting for multiple testing using the false discovery rate, additional compelling evidence exists, including multiple SNPs with nominally significant p values in COL1A1 and the IL1A region, and previous reports of association for IL1A, to support continued interest in these genes as candidates for PE. Identification of the genetic regulators of PE may have broader implications, since women with PE are at increased risk of death from cardiovascular diseases later in life.

Hypervolemia of pregnancy is not maintained in mice chronically overexpressing angiotensinogen

OBJECTIVE

Women who develop pre-eclampsia show significantly less hypervolemia of pregnancy, compared with controls. We have shown that chronically elevated angiotensinogen expression increases a woman's risk of developing pre-eclampsia. Our objective was to determine whether increased angiotensinogen expression is sufficient to cause failed hypervolemia.

STUDY DESIGN

To isolate the effects of elevated angiotensinogen expression, we studied transgenic mice with either 2 or 3 copies of the murine angiotensinogen gene. Plasma volume was measured by Evans blue dye dilution, and kidney sections were immunostained for angiotensinogen and renin.

RESULTS

Three-copy mice failed to maintain hypervolemia after midgestation (P < .01) and failed to up-regulate renin expression in the distal nephron, compared with 2-copy controls. Intrarenal angiotensinogen was up-regulated during pregnancy in both genotypes.

CONCLUSION

Chronically elevated angiotensinogen expression is sufficient to cause failed hypervolemia of pregnancy. Whether this observation is related to failed up-regulation of distal tubule renin expression requires further study.

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.

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

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

Population genetics models of common diseases

The number and frequency of susceptibility alleles for common diseases are important factors to consider in the efficient design of disease association studies. These quantities are the results of the joint effects of mutation, genetic drift and selection. Hence, population genetics models, informed by empirical knowledge about patterns of disease variation, can be used to make predictions about the allelic architecture of common disease susceptibility and to gain an overall understanding about the evolutionary origins of such diseases. Equilibrium models and empirical studies suggest a role for both rare and common variants. In addition, increasing evidence points to changes in selective pressures on susceptibility genes for common diseases; these findings are likely to form the basis for further modeling studies.

Differential roles of Angiotensinogen and Angiotensin Receptor type 1 polymorphisms in breast cancer risk

While angiotensinogen (AGT) seems to have anti proliferative properties, angiotensin II (ATII) is a potent growth factor and it mediates its actions through the angiotensin type 1 receptor (AGTR1). In the AGT gene, the M235T polymorphism has been associated with the variation in angiotensinogen levels and in the AGTR1 gene; the C573T variant is associated with different pathologies. We aimed to evaluate the relationship of these two variants and the risk of breast cancer. These polymorphisms were genotyped in 3787 women participating the Rotterdam Study. We performed a logistic regression and a disease free survival analysis by genotype. The logistic regression yielded an odds ratio of 1.4 (95% CI: 1.1-1.9) for the MM genotype carriers versus the T allele carriers. The breast cancer free survival by AGT genotype was significantly reduced in MM genotype carriers compared to non-carriers (hazard ratio (HR) = 1.5; 95% CI: 1.1-2.2). We did not find any association of the AGTR1 polymorphism and breast cancer risk or disease free survival. Our results suggest that AGT plays a role in breast cancer risk in postmenopausal women, whereas the role of AGTR1 needs further studying.