Haplotypes of angiotensinogen in essential hypertension

Angiotensinogen as a Therapeutic Target for Cardiovascular and Metabolic Diseases

AGT (angiotensinogen) is the unique precursor for the generation of all the peptides of the renin-angiotensin system, but it has received relatively scant attention compared to many other renin-angiotensin system components. Focus on AGT has increased recently, particularly with the evolution of drugs to target the synthesis of the protein. AGT is a noninhibitory serpin that has several conserved domains in addition to the angiotensin II sequences at the N terminus. Increased study is needed on the structure-function relationship to resolve many unknowns regarding AGT metabolism. Constitutive whole-body genetic deletion of Agt in mice leads to multiple developmental defects creating a challenge to use these mice for mechanistic studies. This has been overcome by creating Agt-floxed mice to enable the development of cell-specific deficiencies that have provided considerable insight into a range of cardiovascular and associated diseases. This has been augmented by the recent development of pharmacological approaches targeting hepatocytes in humans to promote protracted inhibition of AGT synthesis. Genetic deletion or pharmacological inhibition of Agt has been demonstrated to be beneficial in a spectrum of diseases experimentally, including hypertension, atherosclerosis, aortic and superior mesenteric artery aneurysms, myocardial dysfunction, and hepatic steatosis. This review summarizes the findings of recent studies utilizing AGT manipulation as a therapeutic approach.

Association of rs5051 and rs699 polymorphisms in angiotensinogen with coronary artery disease in Iranian population: A case-control study

Coronary artery disease (CAD) is the third most common cause of mortality globally (with 17.8 million deaths annually). Angiotensinogen (AGT) and polymorphisms in this gene can be considered as susceptibility factors for CAD. We performed a retrospective case-control study to determine the correlation of AGT rs5051 and rs699 polymorphisms with CAD in an Iranian population. We genotyped 310 CAD patients and 310 healthy subjects using polymerase chain reaction-based methods. To confirm the accuracy of the screening approach, 10% of genotyped subjects were validated using gold-standard Sanger Sequencing. To evaluate the effect of the candidate polymorphisms, white blood cells were randomly purified from the subjects and AGT expression was measured by quantitative reverse transcriptase-polymerase chain reaction. Sex stratification indicated a significant correlation between CAD and male sex (P = .0101). We found a significant association between the rs5051 A allele (P = .002) and the rs699 C allele, and CAD (P = .0122) in recessive and dominant models. Moreover, our findings showed a significant association of the haplotype, including the rs5051 A/A and rs699 T/C genotypes, with CAD (P = .0405). Finally, AGT mRNA levels were significantly decreased in patients harboring the candidate polymorphisms (P = .03). According to our findings The AGT rs5051 A and AGT rs699 C alleles are predisposing variants of CAD risk and severity in the Iranian population.

Angiotensinogen: More Than its Downstream Products: Evidence From Population Studies and Novel Therapeutics

The renin-angiotensin-aldosterone system (RAAS) is a well-defined pathway playing a key role in maintaining circulatory homeostasis. Abnormal activation of RAAS contributes to development of cardiovascular disease, including heart failure, cardiac hypertrophy, hypertension, and atherosclerosis. Although several key RAAS enzymes and peptide hormones have been thoroughly investigated, the role of angiotensinogen-the precursor substrate of the RAAS pathway-remains less understood. The study of angiotensinogen single-nucleotide polymorphisms (SNPs) has provided insight into associations between angiotensinogen and hypertension, congestive heart failure, and atherosclerotic cardiovascular disease. Targeted drug therapy of RAAS has dramatically improved clinical outcomes for patients with heart failure, myocardial infarction, and hypertension. However, all such therapeutics block RAAS components downstream of angiotensinogen and elicit compensatory pathways that limit their therapeutic efficacy as monotherapy. Upstream RAAS targeting by an angiotensinogen inhibitor has the potential to be more efficacious in patients with suboptimal RAAS inhibition and has a better safety profile than multiagent RAAS blockade. Newly developed therapeutics that target angiotensinogen through antisense oligonucleotides or silencer RNA technologies are providing a novel perspective into the pathobiology of angiotensinogen and show promise as the next frontier in the treatment of cardiovascular disease.

Regulators of Epithelial Sodium Channels in Aldosterone-Sensitive Distal Nephrons (ASDN): Critical Roles of Nedd4L/Nedd4-2 and Salt-Sensitive Hypertension

Ubiquitination is a representative, reversible biological process of the post-translational modification of various proteins with multiple catalytic reaction sequences, including ubiquitin itself, in addition to E1 ubiquitin activating enzymes, E2 ubiquitin conjugating enzymes, E3 ubiquitin ligase, deubiquitinating enzymes, and proteasome degradation. The ubiquitin–proteasome system is known to play a pivotal role in various molecular life phenomena, including the cell cycle, protein quality, and cell surface expressions of ion-transporters. As such, the failure of this system can lead to cancer, neurodegenerative diseases, cardiovascular diseases, and hypertension. This review article discusses Nedd4-2/NEDD4L, an E3-ubiquitin ligase involved in salt-sensitive hypertension, drawing from detailed genetic dissection analysis and the development of genetically engineered mice model. Based on our analyses, targeting therapeutic regulations of ubiquitination in the fields of cardio-vascular medicine might be a promising strategy in future. Although the clinical applications of this strategy are limited, compared to those of kinase systems, many compounds with a high pharmacological activity were identified at the basic research level. Therefore, future development could be expected.

Effect of Genetic and Nongenetic Factors on the Clinical Response to Mineralocorticoid Receptor Antagonist Therapy in Egyptians with Heart Failure

This prospective cohort study evaluated the association between the renin angiotensin aldosterone system genotypes and response to spironolactone in 155 Egyptian patients with heart failure with reduced ejection fraction (HFrEF). Genotype frequencies for AGT rs699 were: CC = 16%, CT = 48%, and TT = 36%. Frequencies for CYP11B2 rs1799998 were: TT = 33%, TC = 50%, and CC = 17%. After 6 months of spironolactone treatment, change in the left ventricular ejection fraction (LVEF) differed by AGT rs699 (CC, 14.6%; TC, 7.9%; TT, 2.7%; P = 2.1E‐26), and CYP11B2 rs1799998 (TT, 9.1%; TC, 8.7%; CC, 1.4%; P = 0.0006) genotypes. Multivariate linear regression showed that the AGT rs699 and CYP11B2 rs1799998 polymorphisms plus baseline serum potassium explained 71% of variability in LVEF improvement (P = 0.001), 63% of variability in serum potassium increase (P = 2.25E‐08), and 39% of the variability in improvement in quality of life (P = 2.3E‐04) with spironolactone therapy. These data suggest that AGT and CYP11B2 genotypes as well as baseline serum K are predictors of spironolactone response in HFrEF.

Association study of M235T and A-6G polymorphisms in angiotensinogen gene with risk of developing preeclampsia in Iranian population

OBJECTIVE

Preeclampsia (PE) is a life-threatening complication of pregnancy that accounts for 12% of all maternal deaths worldwide. The aim of this study is to investigate the relationships between the polymorphisms of angiotensinogen (AGT) gene and preeclampsia.

MATERIAL AND METHODS

In this study, 240 unrelated preeclampsia patients and 178 normotensive women were examined. Genomic DNA was extracted then we assessed M235T(C/T) and A-6G polymorphisms of the AGT gene. Genotyping of M235T and A-6G polymorphisms were performed using SSP-PCR and MS-PCR, respectively.

RESULTS

A significant protective association was observed between A-6G G allele, A-6G A/G heterozygote genotype (OR = 0.6, p = 0.007 and OR = 0.6, p = 0.04) against PE. Furthermore, it was shown that two copies of A-6G A allele would increase PE risk (OR: 0.62, p = 0.04). Our results did not show a significant association for M235T polymorphism and PE. However, the combinations of A-6G A/A genotype and M235T T/C genotype (OR = 0.4, p = 0.02) and also A-6G A/G genotype and M235T T/C genotype (OR = 0.5, p = 0.04) in controls represented a significant protective association against PE.

CONCLUSION

According to the existence of significant correlation between two candidate polymorphisms, A-6G and M235T polymorphisms, with PE disease in our study, they may be considered as valuable factors in susceptibility to PE disease in Iranian women.

The relationship among angiotensinogen genes polymorphisms and hs-CRP and coronary artery disease

OBJECTIVE

To assess the association of gene polymorphisms of angiotensinogen (AGT), the key factor in rennin-angiotensin-aldosterone system (RAAS), with high-sensitivity C-reactive protein (hs-CRP) and coronary artery disease (CAD).

METHODS

The current study recruited the patients who were hospitalized and assessed by coronary angiography for suspected CAD. The patients with documented CAD served as CAD group (n = 492) while the patients without documented CAD (n = 87) served as control group. We compared laboratory data and CAD risk factors between the two groups. Furthermore, we analyzed the association of AGT M235T, G217A, G152A, G-6A, A-20C genotypes with coronary artery stenosis and in-stent restenosis.

RESULTS

There were significantly differences between two patient groups in sex, smoking history, diabetes mellitus, carotid atherosclerosis, lower limb arteriosclerosis, hs-CRP, blood glucose, and the level of high-density lipoprotein (HDL; P < 0.05). In CAD group, hs-CRP levels increased with increasing number of coronary artery branches (1, 2, or ≥3; P < 0.01), and Gensini integral was positively correlated with hs-CRP levels (r = 0.361, P < 0.01). Frequencies of genotype and allele distribution in individual angiotensinogen loci (M235T, G217A, G152A, G-6A, A-20C) did not differ in two patient groups. Following stratification of patients according to hs-CRP levels (<1 mg/L, 1-3 mg/L, and >3 mg/L), the distribution frequency of allele M235T was statistically different among the groups (P < 0.05).

CONCLUSION

In CAD patients, M235T among several AGT gene polymorphisms is associated with elevated hs-CRP levels with AGT C allele as the significant factor for patients with hs-CRP level of more than 1 mg/L.

Hypertension and Cerebral Microangiopathy (Cerebral Small Vessel Disease): Genetic and Epigenetic Aspects of Their Relationship

Hypertension (HT) and its cerebral complications are extremely vexing medical and social problems. Despite the obvious association between hypertension and the clinical and neuroimaging features of cerebral microangiopathy (CMA) (also known as cerebral small vessel disease), the causal links between them remain ambiguous. Besides, antihypertensive therapy as the only way to manage these patients does not always prevent brain damage. Knowledge about the key factors and mechanisms involved in HT and CMA development is important for predicting the risk of cerebral complications and developing new approaches to their prevention and treatment. At present, genome-wide association studies and other approaches are used to investigate the common hereditary mechanisms of HT and CMA development, which will explain a large number of CMA cases not associated with hypertension, lack of a correlation between HT severity and the degree of cerebral injury, and failure of antihypertensive therapy to prevent CMA progression. Epigenetic markers likely play a modulating role in the development of these diseases.

Familial Analysis of Epistatic and Sex-Dependent Association of Genes of the Renin-Angiotensin-Aldosterone System and Blood Pressure

BACKGROUND

Renin-angiotensin-aldosterone system genes have been inconsistently associated with blood pressure, possibly because of unrecognized influences of sex-dependent genetic effects or gene-gene interactions (epistasis).

METHODS AND RESULTS

We tested association of systolic blood pressure with single-nucleotide polymorphisms (SNPs) at renin (REN), angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin II type 1 receptor (AGTR1), and aldosterone synthase (CYP11B2), including sex-SNP or SNP-SNP interactions. Eighty-eight tagSNPs were tested in 2872 white individuals in 809 pedigrees from the Victorian Family Heart Study using variance components models. Three SNPs (rs8075924 and rs4277404 at ACE and rs12721297 at AGTR1) were individually associated with lower systolic blood pressure with significant (P<0.00076) effect sizes ≈1.7 to 2.5 mm Hg. Sex-specific associations were seen for 3 SNPs in men (rs2468523 and rs2478544 at AGT and rs11658531 at ACE) and 1 SNP in women (rs12451328 at ACE). SNP-SNP interaction was suggested (P<0.005) for 14 SNP pairs, none of which had shown individual association with systolic blood pressure. Four SNP pairs were at the same gene (2 for REN, 1 for AGT, and 1 for AGTR1). The SNP rs3097 at CYP11B2 was represented in 5 separate pairs.

CONCLUSIONS

SNPs at key renin-angiotensin-aldosterone system genes associate with systolic blood pressure individually in both sexes, individually in one sex only and only when combined with another SNP. Analyses that incorporate sex-dependent and epistatic effects could reconcile past inconsistencies and account for some of the missing heritability of blood pressure and are generally relevant to SNP association studies for any phenotype.

Angiotensin II receptor type 1 A1166C modifies the association between angiotensinogen M235T and chronic kidney disease

Single nucleotide polymorphisms (SNPs) in renin-angiotensin system (RAS) genes are associated with RAS imbalance and chronic kidney disease (CKD). We performed a case-control study and meta-analysis to investigate the association between angiotensinogen (AGT) M235T polymorphism and CKD. A total of 634 patients with end-stage renal disease and 739 healthy controls were studied. We also searched PubMed and the Cochrane Library to identify prospective observational studies published before December 2015. We found that the TT and MT genotypes were associated with a higher risk of CKD than the MM genotype (odds ratio [OR]: 3.56; 95% confidence interval [CI]: 1.14-11.16 and OR: 2.93; 95% CI: 0.91-9.46, respectively). Thirty-eight study populations were included in the meta-analysis. The T allele was associated with a higher risk of CKD than the M allele in all populations (OR: 1.19; 95% CI: 1.08-1.32). The OR was 1.33 in Asians (95% CI: 1.06-1.67) and 1.10 in Caucasians (95% CI: 1.02-1.18). Evaluation of gene-gene and gene-environment interactions using epistasis analysis revealed an interaction between AGT M235T and angiotensin II receptor type 1 A1166C in CKD (OR: 0.767; 95% CI: 0.609-0.965). Genetic testing for CKD in high-risk individuals may be an effective strategy for CKD prevention.

The Hypertension Pandemic: An Evolutionary Perspective

Hypertension affects over 1.2 billion individuals worldwide and has become the most critical and expensive public health problem. Hypertension is a multifactorial disease involving environmental and genetic factors together with risk-conferring behaviors. The cause of the disease is identified in ∼10% of the cases (secondary hypertension), but in 90% of the cases no etiology is found (primary or essential hypertension). For this reason, a better understanding of the mechanisms controlling blood pressure in normal and hypertensive patients is the aim of very active experimental and clinical research. In this article, we review the importance of the renin-angiotensin-aldosterone system (RAAS) for the control of blood pressure, focusing on the evolution of the system and its critical importance for adaptation of vertebrates to a terrestrial and dry environment. The evolution of blood pressure control during the evolution of primates, hominins, and humans is discussed, together with the role of common genetic factors and the possible causes of the current hypertension pandemic in the light of evolutionary medicine.

Association of angiotensinogen gene SNPs and haplotypes with risk of hypertension in eastern Indian population

BACKGROUND

Angiotensinogen (AGT) enzyme comprises a vital module of RAAS system that effectively controls the blood pressure and related cardiovascular functions. Ample association studies have reported the importance of AGT variants in cardiovascular and non-cardiovascular adversities. But lately, owing to the complexity of the many anomalies, the haplotype based examination of genetic variation that facilitates the identification of polymorphic sites which are located in the vicinity of the causative polymorphic site, gets greater appreciation.

METHODS

In the present study, we have done genotype and haplotype analysis of AGT gene in reference to hypertension to confirm the association of the two in an Indian population. To accomplish this, we performed candidate SNPs analysis and construct possible haplotypes across the AGT promoter and gene region in 414 subjects (256 Hypertensive cases and 158 controls).

RESULTS

We found four SNPs (rs11568020: A-152G and rs5050: A-20C in promoter; rs4762 and rs699 in exon2) and 3 haplotypes (H4, H7 and H8) that showed a stronger positive association with hypertension. The haplotype H2 was showing protective association with hypertension.

CONCLUSION

The results of the present study confirmed and reestablished the role of AGT gene variants and their haplotypes in the causation of hypertension in Indian population and showed that haplotypes can provide stronger evidence of association.

Quantification of intact plasma AGT consisting of oxidized and reduced conformations using a modified ELISA

The pleiotropic actions of the renin-angiotensin system (RAS) depend on the availability of angiotensinogen (AGT) which generates angiotensin I (ANG I) when cleaved by renin. Thus, quantification of the intact AGT (iAGT) concentrations is important to evaluate the actual renin substrate available. The iAGT conformation exists as oxidized AGT (oxi-AGT) and reduced AGT (red-AGT) in a disulfide bond, and oxi-AGT has a higher affinity for renin, which may exacerbate RAS-associated diseases. Accordingly, we determined iAGT, oxi-AGT, and red-AGT levels in plasma from rats and mice. Blood samples were obtained by cardiac puncture and then immediately mixed with an inhibitor solution containing a renin inhibitor. Total AGT (tAGT) levels were measured by tAGT ELISA which detects both cleaved and iAGT. iAGT levels were determined by iAGT ELISA which was found to only detect red-AGT. Thus, it was necessary to treat samples with dithiothreitol, a reducing agent, to quantify total iAGT concentration. tAGT levels in rat and mouse plasma were 1,839 ± 139 and 1,082 ± 77 ng/ml, respectively. iAGT levels were 53% of tAGT in rat plasma but only 22% in mouse plasma, probably reflecting the greater plasma renin activity in mice. The ratios of oxi-AGT and red-AGT were ∼4:1 (rat) and 16:1 (mouse). Plasma iAGT consists of oxi-AGT and red-AGT, suggesting that oxidative stress can influence ANG I generation by the AGT conformation switch. Furthermore, the lower availability of plasma iAGT in mice suggests that it may serve as a limiting factor in ANG I formation in this species.

Role of tagged SNPs of the AGT gene in causing susceptibility to essential hypertension

AIM

Angiotensinogen (AGT) is one of the candidate genes that has been extensively investigated for association of its variants with essential hypertension. Studies focusing on the contribution of tagged single nucleotide polymorphisms (SNPs) in the AGT gene are limited and lacking from Indian population. Hence, the present study was carried out to examine the role of five tagged SNPs viz., g.6147G>A (rs7539020), g.5978A>G (rs2493134); g.6241T>C (rs1078499), g.7781G>T (rs11122577), and g.5855G>A (rs3789678) in the development of hypertension.

MATERIALS AND METHODS

202 hypertensives and 222 normotensives were screened for five tagged SNPs using the method of polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The present study revealed significant association of g.5855G>A polymorphism with essential hypertension in different logistic regression models wherein protection was conferred by g.5855G>A against developing the condition. The polymorphism led to the creation of new exonic splicing enhancer and destruction of exonic splicing silencer site thereby enhancing the process of mRNA splicing. The haplotypes AGTG and GACG were found to have a significant protective effect. Other polymorphisms did not show any significant association with hypertension.

CONCLUSION

The present study is the first one to report the protective role of g.5855G>A polymorphism in the development of essential hypertension. The results reflect possibility of ethnic variation in the contribution of g.5855G>A polymorphism of the AGT gene to essential hypertension.

STK39 and WNK1 Are Potential Hypertension Susceptibility Genes in the BELHYPGEN Cohort

The serine/threonine kinase With-No-Lysine (K) Kinase 1 (WNK1) activates the thiazide-sensitive Na(+)/Cl(-) cotransporter through phosphorylation of STE20/SPS1-related proline/alanine-rich kinase, another serine/threonine kinase encoded by STK39. The aim of this study was to look for association between WNK1 and STK39 gene variants, and blood pressure (BP) and hypertension. Seven hundred seventy-nine Caucasian hypertensive patients (HYP) recruited in 6 academic centers from Belgium, and 906 normotensive (NT) controls were genotyped for 5 single nucleotide polymorphisms-rs3754777, rs6749447, rs35929607 (STK39), rs1468326, and rs765250 (WNK1)-using the Snapshot method. The rare TT genotype at the rs3754777 locus (STK39) was overrepresented in HYP versus NT (7.3% vs 3.0%, P = 0.0002). In the whole study population, the multivariable-adjusted odds ratio (OR) for having hypertension associated with the TT genotype was 5.9 (95% confidence interval: 2.2-15.6), and systolic BP was 10 mm Hg higher in TT compared with wild-type subjects (140.1 vs 130.4 mm Hg, P = 0.002). Similarly, the AA genotype at the rs1468326 locus (WNK1) was twice as frequent in HYP versus NT (5.5% vs 2.3%, P < 0.0001), and associated with an increased adjusted OR of hypertension (4.1; 1.5-11.7) and a higher systolic BP (139.8 vs 130.1 mm Hg, P = 0.003). In the whole cohort, a dose-dependent increase in systolic BP was observed according to the number of at-risk genotypes (0: 129.8 mm Hg; 1: 133.0 mm Hg; 2: 149.3 mm Hg, P = 0.02). Single nucleotide polymorphisms rs3754777 (STK39) and rs1468326 (WNK1) were associated with hypertension and BP in our multicenter Belgian case-control study, which supports the role of STK39 and WNK1 as potential hypertension susceptibility genes. Replication in different clinical settings and study of other candidate loci belonging to the same molecular pathway is warranted.

Molecular genetics of essential hypertension

Hypertension is a major public health problem in the developing as well as in developed countries due to its high prevalence and its association with coronary heart disease, renal disease, stroke, peripheral vascular disease, and related disorders. Essential hypertension (EH) is the most common diagnosis in this disease, suggesting that a monocausal etiology has not been identified. However, a number of risk factors associated with EH have also been identified such as age, sex, demographic, environmental, genetic, and vascular factors. Recent advances in molecular biological research had achieved clarifying the molecular basis of Mendelian hypertensive disorders. Molecular genetic studies have now identified mutations in several genes that cause Mendelian forms of hypertension in humans. However, none of the single genetic variants has emerged from linkage or association analyses as consistently related to the blood pressure level in every sample and in all populations. Besides, a number of polymorphisms in candidate genes have been associated with differences in blood pressure. The most prominent candidate has been the polymorphisms in the renin-angiotensin-aldosterone system. In total, EH is likely to be a polygenic disorder that results from inheritance of a number of susceptibility genes and involves multiple environmental determinants. These determinants complicate the study of blood pressure variations in the general population. The complex nature of the hypertension phenotype makes large-scale studies indispensable, when screening of familial and genetic factors was intended. In this review, recent genetic studies exploring the molecular basis of EH, including different molecular pathways, are highlighted.

Association of polymorphisms within the Renin-Angiotensin System with metabolic syndrome in a cohort of Chilean subjects

OBJECTIVE

Metabolic syndrome (MetS) is associated with hypertension, obesity and dyslipidemia. Thus, genetic variants related with these conditions may modulate its development. We evaluated the effect of polymorphisms in the renin-angiotensin system (RAS) on metabolic syndrome risk in a cohort of Chilean subjects.

SUBJECTS AND METHODS

A total of 152 subjects, 83 with MetS (51.2 ± 9.6 years) and 69 without MetS (49.5 ± 9.3 years) of both genders were included, according to the ATP III update criteria. The rs4340 Insertion/Deletion (I/D), rs699 (T>C) and rs5186 (A>C) of the ACE, AGT and AGTR1 genes, respectively, were genotyped.

RESULTS

After adjusting for age and gender, we observed the DD genotype of rs4340 associated with MetS (p = 0.02). Specifically, the DD genotype was associated with MetS risk in women (OR = 4.62, 95%CI, 1.41 - 15.04; p < 0.01). In males, the AA genotype for rs5186 variant was associated with an increased risk for developing MetS when compared with women carrying the same genotype (OR = 3.2; 95%CI, 1.03 - 9.89; p = 0.04). In subjects without MetS, DD genotype was associated with increased waist circumference (p = 0.023) while subjects with MetS carrying the rs5186 TT genotype showed higher levels of HDL-cholesterol (p = 0.031).

CONCLUSION

The present study contributes data highlighting the role for RAS polymorphisms in predisposing to metabolic syndrome in Chilean subjects.

Angiotensinogen (AGT) M235T, AGT T174M and Angiotensin-1-Converting Enzyme (ACE) I/D Gene Polymorphisms in Essential Hypertension: Effects on Ramipril Efficacy

Background:

Hypertension, one of the most important risk factors for premature cardiovascular disease, is a major worldwide public health problem. Angiotensin-1-converting enzyme (ACE) and angiotensinogen (AGT) gene polymorphisms are thought to be associated with primary hypertension. In the present study, we examined the frequency of these gene polymorphisms in an adult population with and without essential hypertension. Furthermore, we evaluated the effect of ACE and AGT gene polymorphisms on ramipril treatment efficacy in the hypertensive patients.

Methods:

A total of 166 adults (83 hypertensives and 83 normotensives) were involved in the study and genotyped for AGTM235T (rs699), AGTT174M (rs4762) and ACEI/D (rs1799752) gene polymorphisms.

Results:

The genotype and allele distribution of the AGTM235T variant significantly differed between hypertensives and normotensives [odds ratio (OR) = 1.57% (T vs M allele), 95% confidence intervals (CIs): 1.01 - 2.44; p=0.045 for hypertensives]. However, none of the 3 studied Simple Nucleotide Polymorphisms were associated with the blood pressure-lowering response to ramipril.

Conclusion:

These results suggest that AGTM235T gene polymorphism is associated with essential hypertension. However, none of the AGTM235T, AGTT174M and ACEI/D gene polymorphisms influenced ramipril effectiveness.

Association of the angiotensinogen M235T polymorphism with recurrence after catheter ablation of acquired atrial fibrillation

PURPOSE

Previous studies showed that genetic variants of the angiotensinogen (AGT) gene conferred higher risk for acquired atrial fibrillation (AF). The present study investigated whether AGT variants correlate with the clinical outcome in patients with acquired AF after catheter ablation (CA).

METHODS

A total of 150 acquired symptomatic drug-refractory AF patients (mean age 63.7±11.0 years, 24.6% non-paroxysmal AF) with acquired AF underwent a single CA procedure in our department and were included in this retrospective analysis. Eight tagging single nucleotide polymorphisms (tSNPs) in the AGT gene were genotyped. Standard electrocardiographs (ECGs) and 24-hour Holter recordings were performed during a median follow-up period of 57.5 months to detect AF recurrence.

RESULTS

Sixty-one patients (40.7%) suffered AF recurrences after a single CA procedure during follow up. Of the eight tSNPs, the frequency of the M allele of M235T was significantly higher in the recurrence group (28%) compared to the non-recurrence group (18%) (p=0.042). The recurrence rates of patients with the TT, MT, and MM genotypes were 34.4%, 50%, and 55.6%, respectively (ptrend=0.049). After adjusting for age, sex, body mass index, hypertension, left atrial volume index (LAVI) and other covariates, M235T increased the risk of AF recurrence in additive and dominant models with odds ratios of 2.023 (95% confidence interval (CI): 1.034-3.926, p=0.033) and 2.601 (95% CI: 1.102-6.056, p=0.025), respectively. However, in multiple correction analyses, the p values of multiple comparisons were not statistically significant (pcorrect>0.05).

CONCLUSIONS

The M allele of M235T might be associated with an increased risk of AF recurrence after CA. Genotyping may thus be helpful on identifying patients with higher risks of AF recurrence after CA and developing optimal follow-up strategies. These strategies may differ and should be individualized according to patients' genotype. Future studies are warranted to validate the potential effect of AGT M235T on AF recurrence post CA.

Association between angiotensinogen M235T polymorphism and hypertrophic cardiomyopathy

BACKGROUND

To investigate the relationship between angiotensinogen (AGT) gene M235T polymorphism and hypertrophic cardiomyopathy (HCM) to explore the potential role of the AGT polymorphism in HCM.

METHODS

PubMed, Embase, OVID, Cochrane library, CNKI, Wan Fang Database were searched to identify the studies involving AGT M235T polymorphism and HCM. Two authors performed independent literature review and study quality assessment using the Newcastle-Ottawa Scale (NOS) checklist. A random-effects model was used to calculate the overall combined risk estimates.

RESULTS

Nine studies involving 887 cases and 1407 controls were included in our meta-analysis. No significant associations were found between AGT M235T polymorphism and HCM (allele model T vs M: OR = 1.17, 95% CI = 0.95-1.45; dominant model TT vs (MM/MT): OR = 1.21, 95% CI = 1.00-1.45; recessive model (TT/MT) vs MM: OR = 1.12, 95% CI = 0.87-1.45; heterozygous comparison MT vs MM: OR = 1.07, 95% CI = 0.82-1.41; homozygous comparison TT vs MM OR = 1.19, 95% CI = 0.88-1.61. In subgroup analysis, the significant difference of association between AGT M235T polymorphism and HCM existed in Asian and sporadic hypertrophic cardiomyopathy (SHCM), but no significant difference was found in Europeans and familial hypertrophic cardiomyopathy (FHCM).

CONCLUSIONS

There is no association between AGT M235T polymorphism and HCM in general populations, but such a relationship exists in Asians and SHCM.

Epithelial sodium transport and its control by aldosterone: the story of our internal environment revisited

Transcription and translation require a high concentration of potassium across the entire tree of life. The conservation of a high intracellular potassium was an absolute requirement for the evolution of life on Earth. This was achieved by the interplay of P- and V-ATPases that can set up electrochemical gradients across the cell membrane, an energetically costly process requiring the synthesis of ATP by F-ATPases. In animals, the control of an extracellular compartment was achieved by the emergence of multicellular organisms able to produce tight epithelial barriers creating a stable extracellular milieu. Finally, the adaptation to a terrestrian environment was achieved by the evolution of distinct regulatory pathways allowing salt and water conservation. In this review we emphasize the critical and dual role of Na(+)-K(+)-ATPase in the control of the ionic composition of the extracellular fluid and the renin-angiotensin-aldosterone system (RAAS) in salt and water conservation in vertebrates. The action of aldosterone on transepithelial sodium transport by activation of the epithelial sodium channel (ENaC) at the apical membrane and that of Na(+)-K(+)-ATPase at the basolateral membrane may have evolved in lungfish before the emergence of tetrapods. Finally, we discuss the implication of RAAS in the origin of the present pandemia of hypertension and its associated cardiovascular diseases.

Risk conferred by tagged SNPs of AGT gene in causing susceptibility to essential hypertension

Abstract Introduction: AGT gene harbors several variants of which 21 are found to be in high linkage disequilibrium as per Hapmap database. Studies delineating the importance of these tagged SNPs are very limited and lacking from Indian population. In the present study, we evaluated the contribution of four tagged SNPs namely, g.6635G > A, g.6506G > A, g.12840G > A, and g.13828T > C at AGT locus along with the analyses of haplotype and epistatic interactions in causing susceptibility to essential hypertension (EHT).

METHODS

About 215 hypertensives and 230 normotensives were genotyped for selected tagged SNPs using PCR-RFLP method.

RESULTS

Significant association was obtained for g.6635G > A and g.6506G > A polymorphisms wherein GG homozygotes for both the markers were at risk for developing the condition. g.13828T > C polymorphism specially, female heterozygotes (TC) were found to be at increased risk for EHT. Haplotype GGGC was found to have a significant protective effect (p = 0.0059). Markers g.6506G > A and g.12840G > A resulted in the creation of new enhancer sites thereby affecting splicing process.

CONCLUSION

The present report is the first one in the literature showing general- and gender-specific association of g.6506G > A and g.13828T > C polymorphisms, respectively, with EHT. However, further studies for replication of present observations are warranted from other populations and other parts of India.

Novel variants detected in AGT gene among patients with essential hypertension

INTRODUCTION

AGT is the first gene to be linked to essential hypertension (EHT). It harbors several variants of which only few polymorphisms are found to exhibit positive and negative associations with hypertension. In the present study, the AGT gene was screened to detect already reported and novel variations contributing to the development of hypertension.

METHOD

In total, 215 hypertensives and 230 normotensives were screened for variations in all the five exons and a part of promoter of AGT gene using single strand conformation polymorphism analysis followed by sequencing of samples showing mobility shifts on polyacrylamide gels.

RESULTS

Five novel variants, namely c.-61G>A in promoter, c.-4+17C>T in intron1, c.24T>C and c.28A>T in Exon2, and c.*90 T>C in 3' untranslated region were detected in the AGT gene. c.-61G>A lies in the promoter region that plays a critical role in its expression. Variation c.-4+17C>T created a new enhancer site. c.24T>C (TCT-TCC) is a silent mutation while c.28A>T (p. M10L) has a possible damaging effect on the AGT protein. c.*90T>C, detected in the 3' untranslated region is thought to play an important role in the translation and stability of the mRNA.

CONCLUSION

Studies on the functional role of these novel variants are warranted to understand the mechanism underlying the development of EHT.

The influence of Angiotensin converting enzyme and angiotensinogen gene polymorphisms on hypertrophic cardiomyopathy

Some studies have reported that angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes have been associated with hypertrophic cardiomyopathy (HCM). However, there have been inconsonant results among different studies. To clarify the influence of ACE and AGT on HCM, a systemic review and meta-analysis of case-control studies were performed. The following databases were searched to indentify related studies: PubMed database, the Embase database, the Cochrane Central Register of Controlled Trials database, China National Knowledge Information database, and Chinese Scientific and Technological Journal database. Search terms included "hypertrophic cardiomyopathy", "angiotensin converting enzyme" (ACE) or "ACE" and "polymorphism or mutation". For the association of AGT M235T polymorphism and HCM, "angiotensin converting enzyme" or "ACE" was replaced with "angiotensinogen". A total of seventeen studies were included in our review. For the association of ACE I/D polymorphism and HCM, eleven literatures were included in the meta-analysis on association of penetrance and genotype. Similarly, six case-control studies were included in the meta-analysis for AGT M235T. For ACE I/D polymorphism, the comparison of DI/II genotype vs DD genotype was performed in the present meta-analysis. The OR was 0.73 (95% CI: 0.527, 0.998, P = 0.049, power = 94%, alpha = 0.05) after the study which deviated from Hardy-Weinberg Equilibrium was excluded, indicating that the ACE I/D gene polymorphism might be associated with HCM. The AGT M235T polymorphism did not significantly affect the risk of HCM. In addition, ACE I/D gene polymorphism did not significantly influence the interventricular septal thickness in HCM patients. In conclusion, the ACE I/D polymorphism might be associated with the risk of HCM.

Angiotensinogen promoter polymorphisms predict low diffusing capacity in U.S. and Spanish IPF cohorts

BACKGROUND

Single nucleotide polymorphisms (SNPs) in angiotensinogen (AGT) at positions -20 and -6 are associated with increased severity and progression of various fibrotic diseases. Our earlier work demonstrated that the progression of idiopathic pulmonary fibrosis (IPF) was associated with the A-6 allele. This study examined the hypothesis that the homozygous CC genotype at -20 and the AA genotype at -6 would confer worse measures of pulmonary function (measured by pulmonary function tests) in IPF.

METHODS

Multiple logistic regression analysis was applied to a NIH Lung Tissue Research Consortium cohort and a Spanish cohort, while also adjusting for covariates to determine the effects of these SNPs on measures of pulmonary function.

RESULTS

Analysis demonstrated that the CC genotype at -20 was strongly associated with reduced diffusing capacity in males in both cohorts (p = 0.0028 for LTRC and p = 0.017 for the Spanish cohort). In females, the AA genotype was significantly associated with lower FVC (p = 0.0082) and V alv (p = 0.022). In males, the haplotype CA at -20 and -6 in AGT was also strongly associated with reduced diffusing capacity in both cohorts.

CONCLUSIONS

This study is the first to demonstrate an association of AGT polymorphisms (-20A > C and -6G > A) with lower measures of pulmonary function in IPF. It is also the first to relate the effect of gender in lung fibrosis with polymorphisms in AGT.

The relationship between angiotensinogen gene polymorphisms and essential hypertension in a Northern Han Chinese population

Gene polymorphisms of the renin-angiotensin system are involved in the pathophysiology of hypertension. We genotyped 4 polymorphisms of angiotensinogen (AGT) gene A-20C (rs5050), A-6G (rs5051), C3889T (rs4762), and C4072T (rs699) by polymerase chain reaction-restriction fragment length polymorphism in 652 patients and 780 controls to examine the association of AGT and hypertension in a Northern Han Chinese population. There were significant differences in the distribution of genotypes and allele frequencies at C4072T between the patients and the controls (both P < .01); patients with CC genotype had a higher risk of hypertension (odds ratio = 1.7, 95% confidence interval 1.4-2.1). The distribution of genotypes at A-6G was significantly different between patients and controls (P < .05). No other significant differences in genotypes or frequencies were observed. No association was observed between the haplotypes of AGT and hypertension. The AGT-6A and 4072C alleles are associated with susceptibility to hypertension in this population.

Central angiotensinergic mechanisms associated with hypertension

Following its generation by both systemic and tissue-based renin-angiotensin systems, angiotensin II interacts with specific, G-protein coupled receptors to modulate multiple physiological systems, including the cardiovascular system. Genetic models in which the different components of the renin-angiotensin system have been deleted show large changes in resting blood pressure. Interruption of the generation of angiotensin II, or its interaction with these receptors, decreases blood pressure in hypertensive humans and experimental animal models of hypertension. Whilst the interaction of angiotensin II with the kidney is pivotal in this modulation of blood pressure, an involvement of the system in other tissues is important. Both systemic angiotensins, acting via the blood-brain barrier deficient circumventricular organs, and centrally-generated angiotensin modulate cardiovascular control by regulating fluid and electrolyte ingestion, autonomic activity and neuroendocrine function. This review discusses the pathways in the brain that are involved in this regulation of blood pressure as well as examining the sites in which altered angiotensin function might contribute to the development and maintenance of high blood pressure.

Adipocyte deficiency of angiotensinogen prevents obesity-induced hypertension in male mice

Previous studies demonstrated that diet-induced obesity increased plasma angiotensin II concentrations and elevated systolic blood pressures in male mice. Adipocytes express angiotensinogen and secrete angiotensin peptides. We hypothesize that adipocyte-derived angiotensin II mediates obesity-induced increases in systolic blood pressure in male high fat-fed C57BL/6 mice. Systolic blood pressure was measured by radiotelemetry during week 16 of low-fat or high-fat feeding in Agt(fl/fl) and adipocyte angiotensinogen-deficient mice (Agt(aP2)). Adipocyte angiotensinogen deficiency had no effect on diet-induced obesity. Basal 24-hour systolic blood pressure was not different in low fat-fed Agt(fl/fl) compared with Agt(aP2) mice (124 ± 3 versus 128 ± 3 mm Hg, respectively). In Agt(fl/fl) mice, high-fat feeding significantly increased systolic blood pressure (24 hours; 134 ± 2 mm Hg; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit an increase in systolic blood pressure (126 ± 2 mm Hg). Plasma angiotensin II concentrations were increased by high-fat feeding in Agt(fl/fl) mice (low fat, 32 ± 14; high fat, 219 ± 58 pg/mL; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit elevated plasma angiotensin II concentrations (high fat, 18 ± 7 pg/mL). Similarly, adipose tissue concentrations of angiotensin II were significantly decreased in low fat- and high fat-fed Agt(aP2) mice compared with controls. In conclusion, adipocyte angiotensinogen deficiency prevented high fat-induced elevations in plasma angiotensin II concentrations and systolic blood pressure. These results suggest that adipose tissue serves as a major source of angiotensin II in the development of obesity hypertension.

Angiotensin-converting enzyme deletion allele is beneficial for the longevity of Europeans

The human angiotensin converting enzyme (ACE) gene is one of the most investigated candidate genes for cardiovascular diseases (CVD), but the understanding of its role among the elderly is vague. Therefore, this study focuses at: (a) testing the association of ACE polymorphism with CVD risk factors among the elderly, and (b) detecting the possible unequal distribution of ACE genotypes between senescent and younger segments of the European populations. The association of ACE I/D polymorphism with CVD health status [hypertension (HT), obesity, dislypidemia] in 301 very old subjects (88.2 ± 5 years; F/M = 221/80) was tested by means of logistic regression analysis. The meta-analysis of D allele frequency in general vs. elderly (80+ years) groups was conducted using all publicly available data for European populations comprising both age cohorts. Multiple multinomial logistic regression revealed that within this elderly sample, age (younger olds, 80-90 years), female sex (OR = 3.13, 95% CI = 1.59-6.19), and elevated triglycerides (OR = 2.53, 95% CI = 1.29-4.95) were positively associated with HT, while ACE polymorphism was not. It was also established that the DD genotype was twice as high in 80+ cohort compared to general population of Croatia (p < 0.00001). This trend was confirmed by the meta-analysis that showed higher D allele frequencies in olds from nine of ten considered European populations (OR = 1.19, 95% CI = 1.08-1.31). The data in elderly cohort do not confirm previously reported role of ACE DD genotype to the development of HT. Moreover, meta-analysis indicated that ACE D allele has some selective advantage that contributes to longevity in majority of European populations.

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

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

Hypercontrols in genotype-phenotype analysis reveal ancestral haplotypes associated with essential hypertension

The angiotensinogen gene locus has been associated with essential hypertension in most populations analyzed to date. Increased plasma angiotensinogen levels have been proposed as an underlying cause of essential hypertension in whites; however, differences in the genetic regulation of plasma angiotensinogen levels have also been reported for other populations. The aim of this study was to analyze the relationship between angiotensinogen gene polymorphisms and haplotypes with plasma angiotensinogen levels and the risk of essential hypertension in the Mexican population. We genotyped 9 angiotensinogen gene polymorphisms in 706 individuals. Four polymorphisms, A-6, C4072, C6309, and G12775, were associated with increased risk, and the strongest association was found for the C6309 allele (χ(2)=23.9; P=0.0000009), which resulted in an odds ratio of 3.0 (95% CI: 1.8-4.9; P=0.000006) in the recessive model. Two polymorphisms, A-20C (P=0.003) and C3389T (P=0.0001), were associated with increased plasma angiotensinogen levels but did not show association with essential hypertension. The haplotypes H1 (χ(2)=8.1; P=0.004) and H5 (χ(2)=5.1; P=0.02) were associated with essential hypertension. Using phylogenetic analysis, we found that haplotypes 1 and 5 are the human ancestral haplotypes. Our results suggest that the positive association between angiotensinogen gene polymorphisms and haplotypes with essential hypertension is not simply explained by an increase in plasma angiotensinogen concentration. Complex interactions between risk alleles suggest that these haplotypes act as "superalleles."

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

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

Angiotensinogen gene haplotype is associated with the prevalence of Japanese non-alcoholic steatohepatitis

AIM

  Non-alcoholic steatohepatitis (NASH) patients frequently have hypertension, which is considered to be an important predictive factor for the subsequent development of hepatic fibrosis. The renin-angiotensin system is also known to contribute to the progression of NASH. Various types of functional single-nucleotide polymorphisms (SNPs) involved in the development of NASH have been proposed. Angiotensinogen (AGT) gene SNPs related to cardiovascular diseases have been reported. We aimed to evaluate the involvement of the AGT gene haplotype in Japanese NASH patients.

METHODS

  Previously described genotypes of SNPs of the AGT gene, rs4762 C/T polymorphism (T207M), rs699 C/T polymorphism (T268M), and rs7079 C/A polymorphism (C11537A), were determined in 124 Japanese biopsy-proven NASH patients and 150 healthy volunteers (controls).

RESULTS

  The allele and genotype frequencies in rs4762 and rs699 SNPs in NASH patients were similar to those in controls, while the frequency of the A allele and A/- genotype in rs7079 SNPs were much higher in NASH patients than in controls. In addition, the 3-SNP haplotype CTA was significantly over-represented in NASH patients compared with controls. Regarding clinical features of NASH patients, diastolic blood pressures in patients with the CTA/- genotype were much higher than in patients with other genotypes.

CONCLUSIONS

  We found a 3-SNP haplotype of the AGT gene that is involved in the development of NASH and influences hypertension in NASH patients. These results provide new insight into the therapy of NASH patients with the CTA haplotype using ACE inhibitors or angiotensin II type 1 receptor blockers.

The epistasis between vascular homeostasis genes is apparent in essential hypertension

OBJECTIVE

The epistasis influence of vascular homeostasis genes is vital to multigenetic diseases. This study was designed to perceive the possible role of epistasis in the etiology of essential hypertension.

METHODS

We investigated seven polymorphisms of ACE, CYP11B2 and NOS3 epistatically, and SBP, DBP, MAP, ACE activity, plasma aldosterone concentration (PAC) and NOx level in 860 age- and ethnicity-matched unrelated north-Indian subjects.

RESULTS

The hypertension risk in individuals with interacted-genotypes (IwIw+IwIc)+(4aa), (IcIc)+(4bb+4ba) and IcIc+4aa of the CYP11B2 and NOS3 was significantly higher with odds ratio 5.5 (95% CI=2.9-10.6, P<0.0001), 2.4 (95% CI=1.4-4.1, P<0.0008) and 7.5 (95% CI=1.6-34.8, P=0.010), respectively. The odds ratio for hypertension with interacted-haplotypes (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) of CYP11B2 and NOS3 was 5.3 (95% CI=2.0-14.2, P=0.005) and 3.9 (95% CI=1.4-10.4, P=0.04), respectively; whereas for the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G), the odds ratio was 0.7 (95% CI=0.5-0.9, P=0.03). While the interacted-genotypes, IcIc+4aa correlated with higher SBP and MAP (P=0.006; P=0.04), the interacted-haplotypes, (-344T/Ic)+(-922A/-786T/4a/894G) and (-344T/Ic)+(-922G/-786C/4a/894G) correlated with higher MAP and lower NOx level (P=0.02 and P=0.03, respectively), and the protective interacted-haplotypes (-344T/Iw)+(-922A/-786T/4b/894G) correlated with lower PAC and MAP (P=0.024 and P=0.018, respectively).

CONCLUSIONS

The epistasis between CYP11B2 and NOS3 and its correlation with varied clinical and biochemical parameters signify its possible contribution in the complex etiology of hypertension.

Variants and haplotypes in angiotensinogen gene are associated with plasmatic angiotensinogen level in Mexican population

INTRODUCTION

The plasmatic angiotensinogen (AGT) level has been associated with essential hypertension. Linkage analysis has found a relationship between the AGT gene locus and hypertension in the Mexican-American population, but studies have failed to identify genetic variants associated with hypertension or plasma AGT levels. This study analyzes the relationship between polymorphisms in the AGT gene and plasmatic AGT levels in Mexican population.

METHODS

Nine polymorphisms in AGT gene were genotyped, and plasma AGT level was determined by enzyme-linked immunosorbent assay.

RESULTS

Differences in AGT plasma levels were associated with 2 polymorphisms: T-20G, TT = 25.3 ± 8.3 versus TG + GG = 21.6 ± 8.8 μg/mL; P = 0.008 and C3389T (T174M), CC = 25.8 ± 9.9 versus TC + TT = 20.5 ± 5.4 μg/mL; P = 0.0002. Haplotype 2 was associated with low plasma AGT (-5.1 μg/mL [95% confidence interval: -8.6 to -1.6], P = 0.004) and Haplotype 8 was associated with high plasma AGT (6.5 μg/mL [95% confidence interval: 2.5 to 10.6], P = 0.001). This association remained after adjustment for covariates. A Likelihood Ratio Test for haplotype-phenotype association adjusted for covariates resulted in χ = 38.9, P = 0.0005. The total effect of the haplotypes on plasma AGT level variance was 19.5%. No association was identified between haplotypes and quantitative traits of blood pressure.

CONCLUSIONS

Two polymorphisms (T-20G and C3389T) and 2 haplotypes (H2 and H8) showed an association with plasma AGT levels in Mexican population.

The association of the angiotensinogen gene with insulin sensitivity in humans: a tagging single nucleotide polymorphism and haplotype approach

The purpose of this study was to clarify the association of the angiotensinogen gene (AGT) with insulin sensitivity using single nucleotide polymorphism (SNP) and haplotype analyses in a white cohort. A candidate gene association study was conducted in white persons with and without hypertension (N = 449). Seventeen SNPs of the AGT gene and their haplotypes were analyzed for an association with homeostasis model assessment of insulin resistance (HOMA-IR). Multivariate regression model accounting for age, sex, body mass index, hypertension status, study site, and sibling relatedness was used to test the hypothesis. Nine of the 17 SNPs were significantly associated with lower HOMA-IR levels. Homozygous minor allele carriers of the most significant SNP, rs2493134 (GG), a surrogate for the gain-of-function mutation rs699 (AGT p.M268T), had significantly lower HOMA-IR levels (P = .0001) than heterozygous or homozygous major allele carriers (AG, AA). Direct genotyping of rs699 in a subset of the population showed similar results, with minor allele carriers exhibiting significantly decreased HOMA-IR levels (P = .003). Haplotype analysis demonstrated that haplotypes rs2493137A|rs5050A|rs3789678G|rs2493134A and rs2004776G|rs11122576A|rs699T|rs6687360G were also significantly associated with HOMA-IR (P = .0009, P = .02), and these results were driven by rs2493134 and rs699. This study confirms an association between the AGT gene and insulin sensitivity in white humans. Haplotype analysis extends this finding and implicates SNPs rs2493134 and rs699 as the most influential. Thus, AGT gene variants, previously shown to be associated with AGT levels, are also associated with insulin sensitivity; suggesting a relationship between the AGT gene, AGT levels, and insulin sensitivity in humans.

Interaction of A-240T and A2350G related genotypes of angiotensin-converting enzyme (ACE) is associated with decreased serum ACE activity and blood pressure in a healthy Iranian population

Most of renin-angiotensin system (RAS) gene polymorphisms have not yet been studied in the Iranian population. In the present study, the frequencies of common polymorphisms in the RAS genes, including angiotensin-converting enzyme (ACE) insertion/deletion (I/D) and three single-nucleotide polymorphisms (SNPs), i.e., A-240T, T-93C and A2350G, angiotensinogen M235T, angiotensin II receptor type 1 A1166C and angiotensin II receptor type 2 C3123A variants were determined in DNAs extracted from venous blood of 104 healthy Iranian volunteers. Genotyping was performed by PCR-RFLP method. Serum ACE activity was also assayed using reverse phase HPLC. Combined polymorphisms of TT (A-240T) and GG (A2350G) was significantly associated with decreased serum ACE activity (P=0.042) and decreased diastolic blood pressure (P=0.040). The angiotensin II receptor type 1 A1166C polymorphism (CC genotype) showed a significant association with declined diastolic blood pressure (P=0.028). Serum ACE activity was significantly higher in men compared to women (P=0.033). ACE activity also showed a direct association with diastolic blood pressure (P<0.001). No association was obtained among each single polymorphism with body mass index (BMI), fasting blood sugar (FBS), lipid profile and ACE activity. In conclusion, combined polymorphisms of A-240T and A2350G seem to affect serum ACE level as well as diastolic blood pressure in our study population. However, it also might be hypothesized that they are in strong linkage disequilibrium with other functional mutations not studied yet. Our findings revealed that gene interactions can play an important role in various biological conditions.

Impact of polymorphisms in the renin–angiotensin–aldosterone system on hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous autosomal dominant heart disease characterised by left ventricular hypertrophy in the absence of another cardiac or systemic disease that is capable of producing significant wall thickening. Microscopically it is characterised by cardiomyocyte hypertrophy, myofibrillar disarray and fibrosis. The phenotypic expression of HCM is multifactorial, with the majority of cases occurring secondary to mutations in genes encoding the sarcomere proteins. In conjunction with the genetic heterogeneity of HCM, phenotypic expression also exhibits a high level of variability even within families with the same aetiological mutation, and may be influenced by additional genetic factors. Polymorphisms of the renin–angiotensin–aldosterone system (RAAS) represent an attractive hypothesis as potential disease modifiers, as these genetic variants alter the ‘activation status’ of the RAAS, which leads to more left ventricular hypertrophy through different pathways. The main objective of this review is to provide an overview of the role of different polymorphisms identified in the RAAS, in patients with HCM.

Renin-angiotensin-aldosterone system genotypes and haplotypes affect the susceptibility to nephropathy in type 2 diabetes patients

BACKGROUND

The association between renin C-4063T and angiotensinogen (AGT) T174M, M235T, and A-6G polymorphisms with diabetic nephropathy (DN) was investigated in Tunisian type 2 diabetes (T2DM) patients.

METHODS

Study subjects comprised 917 T2DM patients (405 normoalbuminuric, 329 microalbuminuric and 185 macroalbuminuric). Genotyping was done by PCR-RFLP.

RESULTS

Renin C-4063T allele and genotype frequencies were comparable between DN cases and normoalbuminuric controls. Although AGT 235T and -6G allele, and 235T/T and -6G/G genotype frequencies were higher in DN compared to normoalbuminuric patients, they were comparable between microalbuminuric or macroalbuminuric patients. Three-locus AGT haplotype analysis (A-6G/T174M/M235T) identified DN-protective (ATM, AMM, GTM) and DN-susceptible (GTM, ATT, GMT and AMT) haplotypes, and demonstrated enrichment of GTT haplotype in macroalbuminuric compared to microalbuminuric or normoalbuminuric patients. Regression analysis confirmed negative (AMM) and positive (GTM, ATT, GMT, AMT) association of AGT haplotypes with microalbuminuria, and negative (AMM) and positive (GTM and ATT) association of AGT haplotypes with macroalbuminuria. None of the AGT haplotypes was associated with DN severity.

CONCLUSIONS

Genetic variation at the AGT gene influences the risk of nephropathy in T2DM patients but not extent of DN severity, and thus represents a potential DN genetic susceptibility locus worthy of replication.

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).

Epistatic effects of ACE I/D and AGT gene variants on left ventricular mass in hypertensive patients: the HyperGEN study

Identifying predictors of left ventricular hypertrophy has been an active study topic because of its association with cardiovascular morbidity and mortality. We examined the epistatic effect (gene-gene interaction) of two genes (angiotensin-converting enzyme (ACE) insertion/deletion (I/D); angiotensinogen (AGT) -6G-A, M235T, -20A-C) in the renin-angiotensin system on left ventricular mass (LVM) among hypertensive participants in the Hypertension Genetic Epidemiology Network study. Included were 2156 participants aged 20-87 years (60% women, 63% African American). We employed mixed linear regression models to assess main effects of four genetic variants on echocardigraphically determined LVM (indexed for height), and ACE-by-AGT epistatic effects. There was evidence that AGT -6G-A was associated with LVM among white participants: adjusted mean LVM (gm(-2.7)) increased with 'G' allele copy number ('AA':41.2, 'AG':42.3, 'GG':44.0; P=0.03). There was also evidence of an ACE I/D-by-AGT -20A-C epistatic effect among white participants (interaction P=0.03): among ACE 'DD' participants, AGT -20A-C 'C' allele carriers had lower mean LVM than 'AA' homozygotes ('DD/CC':39.2, 'DD/AC':39.9, 'DD/AA':43.9), with no similar significant effect among ACE 'I' allele carriers ('ID/CC':47.2, 'ID/AC':43.4, 'ID/AA':42.6; 'II/CC': NA, 'II/AC':41.3, 'II/AA':43.1). These findings indicate that renin-angiotensin system variants in at least two genes may interact to modulate LVM.

Difference in angiotensinogen haplotype frequencies between chronic heart failure and advanced atherosclerosis patients - new prognostic factor?

Numerous association studies have been involved in studying the angiotensinogen (AGT) variants, AGT plasma levels and relations to cardiovascular diseases, such as hypertension, myocardial infarction, coronary heart disease. To investigate a role of AGT G(-6)A and M235T genetic variants for chronic heart failure (CHF) and advanced atherosclerosis (AA), a total of 240 patients with CHF and 200 patients with AA of the Czech origin were evaluated for the study. The study shows the role of polymorphism AGT G(-6)A in genetic background among advanced atherosclerosis patients and chronic heart failure patients (Pg=0.001). This difference was also observed in comparison of AA patients with subgroup of CHF with dilated cardiomyopathy (Pg=0.02; Pa=0.009), and ischemic heart disease (Pg=0.007). The greatest difference between triple-vessel disease and chronic heart failure groups was observed in frequency of GT haplotype (P<0.001) and GGMT associated genotype (P<0.001). Retrospectively, we found the same trend when the subgroups of CHF were compared to AA group (AA vs. IHD with CHF P<0.001; AA vs. DCM P<0.001). These results suggest AGT genetic variants as a risk factor for chronic heart failure compared to advanced atherosclerosis disease without heart failure, with a strong difference between IHD patients and chronic heart failure patients with ischemic heart disease, especially in haplotypes and associated genotypes.

Renin angiotensin system polymorphisms in patients with metabolic syndrome (MetS)

BACKGROUND

The genes associated with hypertension could be genetic risk factors for metabolic syndrome (MetS).

AIM

To determine the frequency of M235T and T174M-AGT, I/D-ACE and A1166C-AGTR1 in hypertensive patients with MetS and to evaluate the relationship between these polymorphisms and central obesity and dyslipidemia, respectively.

MATERIALS AND METHODS

We performed AGT, AGTR1 and ACE genotyping in 56 hypertensive women (24 with MetS) and 71 normotensive women using PCR-RFLP methods and PCR, respectively.

RESULTS

Hypertensive patients carrying the mutated TT235, MM174 and DD genotypes had an 1.53 (p=0.56), 1.78 (p=0.52) and 1.28 (p=0.78)-fold increased risk to develop MetS. Hypertensive carriers of both mutated TT235 and MM174 or TT235 and D/D or TT235 and CC+AC genotypes had an 8.15 (p=0.04), 4.83 (p=0.04) and 10.53 (p=0.05)-fold increased risk to develop MetS. Hypertensive patients with MetS and TT, D/D or CC genotypes had higher body mass index compared to hypertensive patients without MetS (p</=0.05 for all the genotypes). Hypertensive patients with MetS and TT235, MM174, D/D or CC1166 genotypes had higher triglyceride levels, lower HDL-cholesterol levels and higher waist circumference compared to hypertensive patients without MetS (p</=0.05, except for the association between CC1166 and HDL-cholesterol level).

CONCLUSIONS

The effect of the T174M, I/D and A1166C polymorphisms on MetS may depend on the M235T polymorphism. Among hypertensive subjects with MetS, the presence of TT235, MM174, DD and CC1166 genotypes could be a risk factor for central obesity and dyslipidemia.