Essential arterial hypertension and polymorphism of angiotensinogen M235T gene

Polymorphisms in the Renin-Angiotensin System and eNOS Glu298Asp Genes Are Associated with Increased Risk for Essential Hypertension in a Mexican Population

Background

Essential hypertension is the result of modifiable and genetic factors, and it is associated with increased risk for atherothrombosis. Some polymorphisms are associated with hypertensive disease. The objective was to analyze the association between eNOS Glu298Asp, MTHR C677T, AGT M235T, AGT T174M, and A1166C and ACE I/D polymorphisms with essential hypertension in the Mexican population.

Materials and Methods

In the present study, 224 patients with essential hypertension and 208 subjects without hypertension were included. The Glu298Asp, C677T, M235T, T174M, A1166C, and I/D polymorphisms were determined by the PCR-RFLP technique.

Results

We found statistical differences in age, gender, BMI, systolic and diastolic blood pressure, and total cholesterol between control and cases. However, we found no significant differences in HbA1c and triglycerides between both groups. We observed statistical significant differences in the genotype distribution of Glu298Asp (P = 0.001), I/D (P = 0.02), and M235T (P = 0.004) polymorphisms between both groups. In contrast, there were no differences related to distribution of genotypes of MTHFR C677T (P = 0.12), M174T (P = 0.46), and A1166C (P = 0.85) between cases and control groups.

Conclusions

We identified that Glu298Asp, I/D, and M234T polymorphisms represented an increased risk for essential hypertension and those genetic variants could contribute to the presence of endothelial dysfunction and vasopressor effect, hyperplasia, and hypertrophy of smooth muscle cells, which had an impact for hypertension. In contrast, we found no association between C677C, M174T, and A1166C polymorphisms and hypertensive disease. We suggested that those genetic variants could be identified in individuals with high risk to avoid hypertension and thrombotic disease.

Association Between M235T-AGT and I/D-ACE Polymorphisms and Carotid Atheromatosis in Hypertensive Patients: A Cross-Sectional Study

BACKGROUND/AIM

The renin-angiotensin-aldosterone system (RAAS) may be implicated in carotid atheromatosis (CA) development. We aimed to assess the relationship of M235T-angiotensinogen (AGT) and insertion/deletion of angiotensin conversion enzyme (I/D-ACE) genotypes with CA in patients with essential hypertension (EHT).

PATIENTS AND METHODS

We determined the M235T-AGT and I/D-ACE genotypes, using PCR-RFLP methods, in 162 hypertensive subjects from three tertiary regional medical centers. The relationship between the studied RAAS gene polymorphisms and CA was assessed by multiple logistic regressions.

RESULTS

Hypertensive patients carrying the MT/TT235-AGT and MT235-AGT genotypes had a 2.17-fold (p=0.033) and 2.24-fold (p=0.036) increased risk to develop CA, respectively. These genotypes, MT/TT 235-AGT (OR=2.17, p=0.033) and MT235-AGT (OR=2.24, p=0.036), remain independent risk factors for CA in hypertensive patients according to the multivariate model.

CONCLUSION

There is a statistically significant association between M235T-AGT and CA, when adjusting for several confounders and controlling for hypertension.

Myocardial Infarction and AGT p.Thr174Met Polymorphism: A Meta-Analysis of 7657 Subjects

Background

It has been suggested that the angiotensinogen (AGT) gene rs4762 (p.Thr174Met) polymorphism might be associated with myocardial infarction (MI) risk, but the study results are still debatable. Objective and Methods. In order to explore the relationship between AGT p.Thr174Met polymorphism and MI risk, the current meta-analysis involving 7657 subjects from 11 individual studies was conducted.

Results

A significant association between AGT p.Thr174Met polymorphism and MI was found under recessive (OR: 2.26, 95% CI: 1.35-3.77, P = 0.002), dominant (OR: 1.131, 95% CI: 1.016-1.260, P = 0.024), codominant (OR: 2.198, 95% CI: 1.334-3.621, P = 0.002), and additive (OR: 1.363, 95% CI: 1.132-1.641, P = 0.001) genetic models. In the Asian subgroup, significantly increased MI risk was found under all genetic models (P < 0.05). No significant association between AGT p.Thr174Met polymorphism and MI was found under all genetic models in the Caucasian subgroup (P > 0.05).

Conclusions

AGT p.Thr174Met variant might increase MI risk, especially within the Asian population. The Met174 allele of AGT p.Thr174Met might confer the risk for MI.

Association Between AGT M235T and Left Ventricular Mass in Vietnamese Patients Diagnosed With Essential Hypertension

Background: Increasing left ventricular mass in hypertensive patients is an independent prognostic marker for adverse cardiovascular outcomes. Genetic factors have been shown to critically affect left ventricular mass. AGT M235T is one of the genetic polymorphisms that may influence left ventricular mass due to its pivotal role in the regulation of plasma angiotensinogen level as well as hypertension pathophysiology in Asian populations. Currently, how M235T affects left ventricular mass is not well-described in Vietnamese hypertensive patients. This study aimed to investigate the association between M235T and left ventricular mass in Vietnamese patients diagnosed with essential hypertension. Materials and Methods: AGT M235T genotyping and 2D echocardiography were performed on 187 Vietnamese subjects with essential hypertension. All the ultrasound parameters were obtained to calculate the left ventricular mass index according to the American Society of Echocardiography and the European Association of Cardiovascular Imaging 2015 guidelines. Other clinical characteristics were also recorded, including age, gender, duration of hypertension, hypertensive treatment, lifestyle, renal function, fasting plasma glucose, and lipid profile. Results: MT and TT genotypes were determined in 30 and 157 subjects, respectively. AGT M235T genotype, duration of hypertension, body mass index, and ejection fraction statistically affected the left ventricular mass index, which was significantly greater in TT compared to MT carriers after adjusting for confounding factors. Conclusion: The TT genotype of AGT M23T was associated with greater left ventricular mass in Vietnamese patients diagnosed with essential hypertension.

LINKS BETWEEN RENIN-ANGIOTENSIN SYSTEM GENETIC POLYMORPHISMS AND LEPTIN SECRETION IN OBESE HEART FAILURE PATIENTS

Chronic heart failure (CHF) and obesity are two conditions frequently associated and which, despite all the advances made in their management in the recent years, their prevalence continues to rise. Obese patients present unique challenges in the diagnosis of CHF and also therapeutic particularities. The genetic differences may be a possible explanation for the fact that some people, irrespective of their lifestyle and common classical cardiovascular risk factors, are more susceptible to develop heart failure. Moreover, the adipose tissue, a huge endocrine organ which secretes adipokines, is also a well-established source of all renin-angiotensin-aldosterone system components, being strongly involved in the pathogenesis of CHF. That is why this review will explore the possible links between the RAS genetic polymorphisms and leptin secretion in obese HF patients, trying to bring a more precise understanding of this relationship, which will undoubtedly facilitate a more appropriate treatment of HF in obese patients. We also try to explain the possible incriminated mechanisms, and plausible biological explanations for the relationship between RAS genetic polymorphisms and adipokines secretion in obese heart failure patients.

Case-control association study of polymorphisms in the angiotensinogen and angiotensin-converting enzyme genes and coronary artery disease and systemic artery hypertension in African-Brazilians and Caucasian-Brazilians

The rennin-angiotensin-aldosterone system (RAAS) is a critical pathway in regulating blood pressure and salt/water homeostasis, possessing an intimate relationship with the development of systemic artery hypertension (SAH). Once hypertension is considered a risk factor for coronary artery disease (CAD), the RAAS is also related to this pathology. This investigation aimed to analyse if the frequencies of AGT M235T (rs699) and ACE I/D (rs4646994) polymorphisms are associated with CAD and SAH in African-Brazilians and Caucasian-Brazilians. In this study we analysed 714 subjects who underwent coronary angiography to detect obstructive lesions and CAD, as well as blood pressure measurement and SAH, grouped according to ethnicity: 266 African-Brazilians and 448 Caucasian-Brazilians. Among CAD and SAH cases and controls, the genotype and allele frequencies of ACE I/D polymorphism were similar in both ethnic groups. The AGT 235TT genotype and 235T allele frequencies were higher in SAH cases (32%, 54.7%) versus controls in Caucasian-Brazilians (19.8%, 46.4%; P = 0.038, P = 0.031, respectively). The AGT 235TT (OR = 1.8; P = 0.028) demonstrated to be an independent factor risk in a multivariate logistic regression increasing SAH risk in Caucasians but not in African-Brazilians. In summary, AGT M235T polymorphism was associated with SAH risk in Caucasian-Brazilians, and no association was detected with CAD. No association was also observed in ACE I/D polymorphism either in CAD or SAH in African-Brazilians and Caucasian-Brazilians.

Renin-angiotensin system transgenic mouse model recapitulates pathophysiology similar to human preeclampsia with renal injury that may be mediated through VEGF

Using a transgenic cross, we evaluated features of preeclampsia, renal injury and the sFlt1/VEGF changes. Transgenic hAGT and hREN, or wild-type (WT) C57Bl/6 mice were cross-bred: female hAGT × male hREN for preeclampsia (PRE) model and female WT × male WT for pregnant controls (WTP). Samples were collected for plasma VEGF, sFlt1, and urine albumin. Blood pressures (BP) were monitored by telemetry. Vascular reactivity was investigated by wire myography. Kidneys and placenta were immunostained for sFlt1 and VEGF. Eleven PRE and 9 WTP mice were compared. PRE more frequently demonstrated albuminuria, glomerular endotheliosis (80% vs. 11%; P = 0.02), and placental necrosis (60% vs. 0%; P < 0.01). PRE group demonstrated declining BPs with advancing gestation. Plasma sFlt1 increased across pregnancy in PRE; VEGF did not vary. IHC demonstrated the presence of sFlt1 in glomeruli, lymphatics, and collecting tubules of PRE kidneys, suggesting excretion. VEGF immunostaining was increased specifically in the glomeruli of PRE kidneys. Placenta in PRE showed marked immunostaining for sFlt1. We conclude that this transgenic model of preeclampsia recapitulates human preeclamptic state with high fidelity, and that, vascular adaptation to pregnancy is suggested by declining BPs and reduced vascular response to PE and increased response to acetylcholine. Placental damage with resultant increased release of sFlt1, proteinuria, deficient spiral artery remodeling, and glomerular endotheliosis were observed in this model of PRE. Increased VEGF binding to glomerular endothelial cells in this model of PRE is similar to human PRE and leads us to hypothesize that renal injury in preeclampsia may be mediated through local VEGF.

[Association of T174M polymorphism of the angiotensinogen gene with the higher risk of cerebral stroke in women]

AIM

To study the association of M235T (rs699) and T174M (rs4762) polymorphisms of the angiotensinogen (AGT) gene with the risk of cerebral stroke (CS) in the Russians of the Central Chernozem Region.

MATERIALS AND METHODS

A total of 638 DNA samples obtained from 353 patients with CS and 285 sex- and age-matched healthy individuals were examined. The polymorphisms were genotyped by polymerase chain reaction (T174M) and TaqMan allelic discrimination (M235T) assays.

RESULTS

Heterozygous AGT 174TM genotype carriers were found to be at a higher risk for CS (odd ratio (OR) = 1.52; 95% confidence interval (CI), 1.08-2.15; p = 0.02). A gender-stratified analysis showed that the mutant 174M allele (OR = 1.86; 95% CI, 1.14-3.03, p = 0.01) and variant 174TM and 174MM genotypes (OR = 1.86; 95% CI, 1.09-3.20; p = 0.02) were associated with the higher risk of cerebral stroke in women.

CONCLUSION

The association of AGT T174M polymorphism with the risk of CS was first found; but the higher risk of the disease in the carriers of variant alleles and genotypes was observed in the women only.

Gender-related association of AGT gene variants (M235T and T174M) with essential hypertension--a case-control study

INTRODUCTION

The human angiotensinogen (AGT) is a promising candidate gene for evaluating susceptibility to essential hypertension (EH). We aimed to assess the association of the variants of AGT gene and the extent of risk involved in developing EH.

METHODS

A case-control study was designed to compare 279 hypertensive patients with 200 normotensive subjects. The frequency distribution of M235T and T174M polymorphisms of AGT gene was assessed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. A haplotype analysis was done to determine the risk conferred by the combination of alleles of the two polymorphisms for EH.

RESULTS

The genotype distribution of the T174M variant differed significantly between hypertensives and normotensives, whereas genotypes of M235T variant did not show such difference. For M235T, MM genotype conferred an increase in risk for hypertension in women (odds ratios (OR) = 2.82; 95% confidence interval (CI) = 1.22-6.49). For the variant T174M, the TM genotype frequency was elevated in hypertensive females (36.5%) as compared to controls (18.8 %; P = .034). The 174M allele was more prevalent among female hypertensives than among female controls (0.20 vs. 0.12; P = .059). The haplotype analysis showed a significant association for the haplotypes of paired markers (M235 and 174M) with a χ(2) value of 8.037 (P = .045).

CONCLUSION

Our findings suggest that the polymorphic variants of AGT gene-M235T and T174M-show association with hypertension.

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.

Angiotensinogen gene variants in a Pakistani hypertensive population of Punjab

Background. The renin-angiotensin-aldosterone system (RAAS) plays a key role in blood pressure (BP) regulation. Among the components of the RAAS, the gene for the angiotensinogen (AGT) has been extensively studied. Several studies in different populations link Threonine instead of methionine at position 235 (M235T) and Methinine instead of threonine at position 174 (T174M) polymorphisms with essential hypertension. We were unable to study these polymorphisms in the Punjab population of Pakistan through routine Restriction Fragment Length Polymorphism (RFLP) method. Considering the importance of this region we decided to further investigate the 300 bp region harbouring these two single nucleotide polymorphisms.

Methods. Samples were derived from a larger study group. Polymerase chain reaction amplified fragments were subjected to either RFLP or Single Strand Conformation. Polymorphism. Single stranded DNA showing mobility shift on denaturing gel were sequenced.

Results. Sequencing confirmed the presence of M235T and T174M polymorphisms in the local population. In addition to these polymorphisms one additional base was found at an identical position in two of the samples. We found a substitution of G with C just adjacent to T174M polymorphism in all seven of our samples studied.

Conclusions. We report two additional bases and one substitution in the angiotensinogen gene of Punjab population. We also suggest that SsmI can be used for the investigation of T174M polymorphism.

Polymorphisms of the insertion / deletion ACE and M235T AGT genes and hypertension: surprising new findings and meta-analysis of data

Background

Essential hypertension is a common, polygenic, complex disorder resulting from interaction of several genes with each other and with environmental factors such as obesity, dietary salt intake, and alcohol consumption. Since the underlying genetic pathways remain elusive, currently most studies focus on the genes coding for proteins that regulate blood pressure as their physiological role makes them prime suspects.

The present study examines how polymorphisms of the insertion/deletion (I/D) ACE and M235T AGT genes account for presence and severity of hypertension, and embeds the data in a meta-analysis of relevant studies.

Methods

The I/D polymorphisms of the ACE and M235T polymorphisms of the AGT genes were determined by RFLP (restriction fragment length polymorphism) and restriction analysis in 638 hypertensive patients and 720 normotensive local blood donors in Weisswasser, Germany. Severity of hypertension was estimated by the number of antihypertensive drugs used.

Results

No difference was observed in the allele frequencies and genotype distributions of ACE gene polymorphisms between the two groups, whereas AGT TT homozygotes were more frequent in controls (4.6% vs. 2.7%, P = .08). This became significant (p = 0.035) in women only. AGT TT genotype was associated with a 48% decrease in the risk of having hypertension (odds ratio: 0.52; 95% CI, 0.28 to 0.96), and this risk decreased more significantly in women (odds ratio: 0.28; 95% CI, 0.1 to 0.78). The meta-analysis showed a pooled odds ratio for hypertension of 1.21 (TT vs. MM, 95% CI: 1.11 to 1.32) in Caucasians. No correlation was found between severity of hypertension and a specific genotype.

Conclusion

The ACE I/D polymorphism does not contribute to the presence and severity of essential hypertension, while the AGT M235T TT genotype confers a significantly decreased risk for the development of hypertension in the population studied here. This contrasts to the findings of meta-analyses, whereby the T allele is associated with increased risk for hypertension.

Genotyping the -6A/G functional polymorphism in the core promoter region of angiotensinogen gene by microchip electrophoresis

Angiotensinogen (AGT) gene has been regarded as one of the candidate genes for essential hypertension. In our study, the role of AGT gene as a putatively predisposing gene for hypertension was evaluated by genotyping a A (-6) G polymorphism in the core promoter region in 123 patients with essential hypertension and 103 healthy controls. A microchip electrophoresis method coupled with polymorphism chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay was used for genotyping the A (-6) G single-nucleotide polymorphism. The separation and detection of the digested PCR amplicons were completed just in 280 s or less. The genotype frequency fulfilled the criteria of the Hardy-Weinbery equilibrium (X2 = 3.067, P > 0.05). The results showed a higher frequency of the -6 A allele (0.70) in the normotensive subjects, which is higher than those reported in Germany (0.47) and Czech (0.40) populations, but similar to that found in Japanese populations (0.73). The frequencies of genotype AA, AG, and GG were 0.46, 0.49, and 0.05 in hypertensive subjects, and 0.44, 0.53, and 0.03 in control subjects. There is no significant difference in the distributions of the genotype and allele between the two groups (X2 = 0.88, P > 0.05; X2 = 0.024, P > 0.05). These findings differ from some of the results obtained in other ethnic groups, indicating the potential importance of ethnic origin in the assessment of genetic risk identifiers for a complex disease.

Glucocorticoid exposure in late gestation in the rat permanently programs gender-specific differences in adult cardiovascular and metabolic physiology

Glucocorticoid overexposure in utero may underlie the association between low birth weight and subsequent development of common cardiovascular and metabolic pathologies. Previously, we have shown that prenatal dexamethasone (DEX) exposure in rat reduces birth weight and programs the hypothalamic-pituitary axis and fasting and postprandial hyperglycemia in adult males and hypertension in adult males and females. This study aimed to determine 1) whether there were gender differences in prenatal DEX-programmed offspring, and 2) whether the renin-angiotensin system (RAS) plays a role in the programming of hypertension. Rats exposed to DEX in utero (100 microg.kg(-1).day(-1) from embryonic days 14-21) were of lower birth weight (by 12%, P < 0.01) and displayed full catch-up growth within the first month of postnatal life. DEX-treated male offspring in adulthood selectively displayed elevated plasma adrenocorticotropic hormone (by 221%) and corticosterone (by 188%, P < 0.05), postprandial insulin-glucose ratios (by 100%, P < 0.05), and hepatic expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (by 38%, P < 0.05). Conversely, DEX-programmed females were hypertensive (by 11%, P < 0.05), with elevated hepatic angiotensinogen mRNA expression (by 9%, P < 0.05), plasma angiotensinogen (by 61%, P < 0.05), and renin activity (by 88%, P < 0.05). These findings demonstrate that prenatal glucocorticoids program adulthood cardiovascular and metabolic physiology in a gender-specific pattern, and that an activated RAS may in part underlie the hypertension associated with prenatal DEX programming.