New polymorphisms of the angiotensin II type 1 receptor gene and their associations with myocardial infarction and blood pressure: the ECTIM study. Etude Cas-Témoin de l'Infarctus du Myocarde

Association of angiotensin ІІ type 1 receptor gene A1166C polymorphism with cancer risk: An updated meta-analysis

Objective:

The association between angiotensin II type 1 receptor (AGTR1) gene A1166C polymorphism and cancer risk has been investigated in many studies. However, the results have been inconclusive. A meta-analysis was performed to obtain a more precise estimation of the relationship.

Methods:

The PubMed and China National Knowledge Infrastructure databases were searched for published literature. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strengths of association.

Results:

Ten studies, including 1553 patients and 1904 controls, were included in the meta-analysis. Overall, there were no significant associations between the AGTR1 gene A1166C polymorphism and cancer risk in the general population (CC vs AA: OR = 1.09, 95% CI = 0.50–2.37; AC vs AA: OR = 1.54, 95% CI = 0.81–2.91; dominant model: OR = 1.46, 95% CI = 0.77–2.79; recessive model: OR = 1.12, 95% CI = 0.84–1.49). In a subgroup analysis by nationality and cancer type, the results also showed no association between this polymorphism and cancer risk.

Conclusions:

This meta-analysis demonstrated that the AGTR1 gene A1166C polymorphism does not appear to be related to the risk of cancer.

Association and Interaction Effect of AGTR1 and AGTR2 Gene Polymorphisms with Dietary Pattern on Metabolic Risk Factors of Cardiovascular Disease in Malaysian Adults

Gene-diet interaction using a multifactorial approach is preferred to study the multiple risk factors of cardiovascular disease (CVD). This study examined the association and gene-diet interaction effects of the angiotensin II type 1 receptor (AGTR1) gene (rs5186), and type 2 receptor (AGTR2) gene (rs1403543) polymorphisms on metabolic risk factors of CVD in Malaysian adults. CVD parameters (BMI, blood pressure, glycated hemoglobin, total cholesterol (TC), triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), and TC/HDL-C ratio), and constructed dietary patterns “vegetables, fruits, and soy diet” (VFSD), and “rice, egg, and fish diet” (REFD) were obtained from previous studies. Genotyping analysis was performed by real-time PCR using Taqman probes. The subjects were 507 adults (151 Malays; 179 Chinese; and 177 Indians). Significant genetic associations were obtained on blood lipids for rs5186 in Malays and Chinese, and rs1403543 in Chinese females. The significant gene-diet interaction effects after adjusting for potential confounders were: rs5186 × VFSD on blood pressure in Malays (p = 0.016), and in Chinese on blood lipids for rs5186 × REFD (p = 0.009–0.023), and rs1403543 × VFSD in female subjects (p = 0.001–0.011). Malays and Chinese showed higher risk for blood pressure and/or lipids involving rs5186 and rs1403543 SNPs together with gene-diet interactions, but not Indians.

Association of Polymorphisms in Endothelial Nitric Oxide Synthesis and Renin-Angiotensin-Aldosterone System with Developing of Coronary Artery Disease in Bulgarian Patients

AIM

The purpose of this study was to evaluate the association of common polymorphisms in endothelial nitric oxide synthesis (eNOS; G894T) and renin-angiotensin-aldosterone system (angiotensin converting enzyme [ACE]-I/D, angiotensinogen-T704C, and angiotensin II receptor type 1-A1166C) as risk factors in the pathogenesis of coronary artery disease (CAD) in Bulgarian patients.

METHODS

This study included 171 patients with CAD and 123 control subjects. Polymerase chain reaction-restriction fragment length polymorphism was used for studying the single-nucleotide polymorphisms. Statistical analysis was performed using statistical software PASW for Windows.

RESULTS

A significantly higher percentage of the eNOS T894 allele was found in patients with acute coronary syndrome (ACS), compared to controls (p = 0.006) and patients with stable angina pectoris (SAP, p = 0.005). Results from a binary regression analysis suggested that eNOS T allele and ACE D allele carriers were more likely to develop ACS than controls (T allele odds ratio [OR] 2.585, p = 0.024; D allele OR 3.585, p = 0.046) and patients with SAP (T allele OR 2.955, p = 0.009; D allele OR 2.703, p = 0.05). Exploratory evaluation of gene-gene combinations showed a significant association between eNOS-G894T/ACE-I/D and ACS compared to controls (p = 0.022) and patients with SAP (p = 0.017).

CONCLUSIONS

The eNOS G894T and ACE I/D polymorphisms are associated with an increased risk of developing ACS after adjusting for classical risk factors for atherosclerosis in the Bulgarian cohort.

Application of microRNAs in diagnosis and treatment of cardiovascular disease

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Innovative, more stringent diagnostic and prognostic biomarkers and effective treatment options are needed to lessen its burden. In recent years, microRNAs have emerged as master regulators of gene expression - they bind to complementary sequences within the mRNAs of their target genes and inhibit their expression by either mRNA degradation or translational repression. microRNAs have been implicated in all major cellular processes, including cell cycle, differentiation and metabolism. Their unique mode of action, fine-tuning gene expression rather than turning genes on/off, and their ability to simultaneously regulate multiple elements of relevant pathways makes them enticing potential biomarkers and therapeutic targets. Indeed, cardiovascular patients have specific patterns of circulating microRNA levels, often early in the disease process. This article provides a systematic overview of the role of microRNAs in the pathophysiology, diagnosis and treatment of CVD.

Association of angiotensin II type 1 receptor (A1166C) gene polymorphism and its increased expression in essential hypertension: a case-control study

OBJECTIVES

Hypertension is one of the major cardiovascular diseases. It affects nearly 1.56 billion people worldwide. The present study is about a particular genetic polymorphism (A1166C), gene expression and protein expression of the angiotensin II type I receptor (AT1R) (SNP ID: rs5186) and its association with essential hypertension in a Northern Indian population.

METHODS

We analyzed the A1166C polymorphism and expression of AT1R gene in 250 patients with essential hypertension and 250 normal healthy controls.

RESULTS

A significant association was found in the AT1R genotypes (AC+CC) with essential hypertension (χ2 = 22.48, p = 0.0001). Individuals with CC genotypes were at 2.4 times higher odds (p = 0.0001) to develop essential hypertension than individuals with AC and AA genotypes. The statistically significant intergenotypic variation in the systolic blood pressure was found higher in the patients with CC (169.4±36.3 mmHg) as compared to that of AA (143.5±28.1 mmHg) and AC (153.9±30.5 mmHg) genotypes (p = 0.0001). We found a significant difference in the average delta-CT value (p = 0.0001) wherein an upregulated gene expression (approximately 16 fold) was observed in case of patients as compared to controls. Furthermore, higher expression of AT1R gene was observed in patients with CC genotype than with AC and AA genotypes. A significant difference (p = 0.0001) in the protein expression of angiotensin II Type 1 receptor was also observed in the plasma of patients (1.49±0.27) as compared to controls (0.80±0.24).

CONCLUSION

Our findings suggest that C allele of A1166C polymorphism in the angiotensin II type 1 receptor gene is associated with essential hypertension and its upregulation could play an important role in essential hypertension.

Effects of Angiotensinogen and Angiotensin II Type I Receptor Genes on Blood Pressure and Left Ventricular Mass Trajectories in Multiethnic Youth

The objective of this study was to evaluate the impact of variations of the angiotensinogen (AGT) and angiotensin II type I receptor (AGTR1) genes on progression of blood pressure (BP) and left ventricular mass (LVM) in multiethnic youth. The study was longitudinal involving 581 European American (EA) and African American (AA) youth with 12 assessments over a 15-year period. AGT M235T and three AGTR1 polymorphisms (C-521T, L191L and A1166C) were genotyped and individual growth curve modeling analyses were conducted. Single nucleotide polymorphism (SNP) analyses found a significant 3-way interaction between M235T, ethnicity and gender on BP levels. Systolic BP (SBP) levels were 5.8 mmHg (p = .00003) and diastolic BP (DBP) levels were 2.6 mmHg (p = .005) lower in carriers versus noncarriers of the M235 allele in AA males only. Furthermore, the AGTR1 L191 allele showed a SBP lowering effect in subjects with a high socioeconomic status (SES; p = .048) and a DBP lowering effect in AAs (p = .038). Haplotype analyses identified a protective haplotype (C-521, 191L and A1166) for LVM levels (p = .03). LVM in individuals homozygous for this haplotype was 12.9 g lower than those homozygous for the most common haplotype (–521T, 191L and A1166). No significant interactions were found between the AGT M235T polymorphism and any of the single SNPs or haplotypes of the AGTR1 gene. Our results in multiethnic youth uncover an ethnicity and gender-specific effect of the AGT M235T polymorphism and a SES or ethnicity-specific effect of the AGTR1 L191L polymorphism on the progression of hypertension risk. A protective AGTR1 haplotype for LVM was also identified.

Next steps in cardiovascular disease genomic research--sequencing, epigenetics, and transcriptomics

BACKGROUND

Genomic research in cardiovascular disease (CVD) has progressed rapidly over the last 5 years. In most cases, however, these groundbreaking observations have not yet been accompanied by clinically applicable tools for risk prediction, diagnosis, or therapeutic interventions.

CONTENT

We reviewed the scientific literature published in English for novel methods and promising genomic targets that would permit large-scale screening and follow-up of recent genomic findings for CVD. We anticipate that advances in 3 key areas will be critical for the success of these projects. First, exome-centered and whole-genome next-generation sequencing will identify rare and novel genetic variants associated with CVD and its risk factors. Improvements in methods will also greatly advance the field of epigenetics and gene expression in humans. Second, research is increasingly acknowledging that static DNA sequence variation explains only a fraction of the inherited phenotype. Therefore, we expect that multiple epigenetic and gene expression signatures will be related to CVD in experimental and clinical settings. Leveraging existing large-scale consortia and clinical biobanks in combination with electronic health records holds promise for integrating epidemiological and clinical genomics data. Finally, a systems biology approach will be needed to integrate the accumulated multidimensional data.

SUMMARY

Novel methods in sequencing, epigenetics, and transcriptomics, plus unprecedented large-scale cooperative efforts, promise to generate insights into the complexity of CVD. The rapid accumulation and integration of knowledge will shed light on a considerable proportion of the missing heritability for CVD.

The ACE gene and human performance: 12 years on

Some 12 years ago, a polymorphism of the angiotensin I-converting enzyme (ACE) gene became the first genetic element shown to impact substantially on human physical performance. The renin-angiotensin system (RAS) exists not just as an endocrine regulator, but also within local tissue and cells, where it serves a variety of functions. Functional genetic polymorphic variants have been identified for most components of RAS, of which the best known and studied is a polymorphism of the ACE gene. The ACE insertion/deletion (I/D) polymorphism has been associated with improvements in performance and exercise duration in a variety of populations. The I allele has been consistently demonstrated to be associated with endurance-orientated events, notably, in triathlons. Meanwhile, the D allele is associated with strength- and power-orientated performance, and has been found in significant excess among elite swimmers. Exceptions to these associations do exist, and are discussed. In theory, associations with ACE genotype may be due to functional variants in nearby loci, and/or related genetic polymorphism such as the angiotensin receptor, growth hormone and bradykinin genes. Studies of growth hormone gene variants have not shown significant associations with performance in studies involving both triathletes and military recruits. The angiotensin type-1 receptor has two functional polymorphisms that have not been shown to be associated with performance, although studies of hypoxic ascent have yielded conflicting results. ACE genotype influences bradykinin levels, and a common gene variant in the bradykinin 2 receptor exists. The high kinin activity haplotye has been associated with increased endurance performance at an Olympic level, and similar results of metabolic efficiency have been demonstrated in triathletes. Whilst the ACE genotype is associated with overall performance ability, at a single organ level, the ACE genotype and related polymorphism have significant associations. In cardiac muscle, ACE genotype has associations with left ventricular mass changes in response to stimulus, in both the health and diseased states. The D allele is associated with an exaggerated response to training, and the I allele with the lowest cardiac growth response. In light of the I-allele association with endurance performance, it seems likely that other regulatory mechanisms exist. Similarly in skeletal muscle, the D allele is associated with greater strength gains in response to training, in both healthy individuals and chronic disease states. As in overall performance, those genetic polymorphisms related to the ACE genotype, such as the bradykinin 2 gene, also influence skeletal muscle strength. Finally, the ACE genotype may influence metabolic efficiency, and elite mountaineers have demonstrated an excess of I alleles and I/I genotype frequency in comparison to controls. Interestingly, this was not seen in amateur climbers. Corroboratory evidence exists among high-altitude settlements in both South America and India, where the I allele exists in greater frequency in those who migrated from the lowlands. Unfortunately, if the ACE genotype does influence metabolic efficiency, associations with peak maximal oxygen consumption have yet to be rigorously demonstrated. The ACE genotype is an important but single factor in the determinant of sporting phenotype. Much of the mechanisms underlying this remain unexplored despite 12 years of research.

Interplay between miR-155, AT1R A1166C polymorphism, and AT1R expression in young untreated hypertensives

BACKGROUND

A silent polymorphism (+1166 A/C single-nucleotide polymorphism) localized in the 3'-UTR (untranslated region) of the human angiotensin II type-1 receptor (AT1R) has been associated with hypertension and cardiovascular complications. The +1166 A/C is recognized by a specific microRNA-155 (miR-155), which is base-pairing complementary with the +1166 A-allele but not with the mutant +1166 C allele. Aim of our study was to investigate the interplay between miR-155 and AT1R protein expression.

METHODS

Sixty-four subjects were selected for the +1166 A/C from the cohort of hypertensives (n = 573) of the Hypertension and Ambulatory Recording Venetia Study (HARVEST): 25 were homozygous for the 1166 A allele, 20 heterozygous, and 19 homozygous for the 1166 C allele.

RESULTS

miR-155 expression was significantly decreased in subjects with CC genotype in comparison to AA and AC genotype. AT1R protein expression was significantly increased in the CC group in comparison to AA and AC (P < 0.01) although AT1R mRNA expression was not significantly different in the three groups. AT1R protein expression was positively correlated with systolic and diastolic blood pressure and negatively correlated with miR-155 expression level. Plasma transforming growth factor-β1 (TGF-β1) may have a modulator role in the interplay between miR-155 and AT1R protein expression as it was correlated negatively with miR-155 expression and positively with AT1R protein expression in subjects with CC genotype.

CONCLUSION

The interplay between miR-155 expression, +1166C polymorphism, and AT1R protein expression may have a role in the regulation of blood pressure.

A1166C genetic variation of the angiotensin II type I receptor gene and susceptibility to coronary heart disease: collaborative of 53 studies with 20,435 cases and 23,674 controls

OBJECTIVE

Angiotensin II induces vasoconstriction and vascular smooth muscle growth via stimulation of the angiotensin II type I receptor (AGTR1). Some studies have reported an association between a genetic variant (A1166C) in the 3' un-translated region of AGTR1 and increased risk of coronary heart disease (CHD), but other have yielded apparently conflicting results.

METHODS

Literature-based meta-analyses were performed on 48 papers including 53 studies published before June 2008 in relation to the A1166C polymorphism (NCBI, dbSNP: rs5186) of the AGTR1, involving a total of 20,435 CHD cases and 23,674 controls. We also explored potential sources of heterogeneity and conducted appropriate stratified analyses.

RESULTS

In a combined analysis, the per-allele odds ratio (OR) for CHD of the A1166C polymorphism was 1.11 (95% confidence interval: 1.03-1.19), but there is an indication of publication bias and heterogeneity among the 53 studies. Sample size and study quality were significant sources of heterogeneity among studies of the A1166C polymorphism with possibly overestimates in studies of smaller sample-size and poor-quality. When the analyses were restricted to 11 larger studies (≥500 cases), and to 8 high-quality studies (quality score: ≥11 points), the summary per-allele odds ratios were 0.992 (95% confidence interval, 0.944-1.042) and 0.990 (95% confidence interval, 0.915-1.072), respectively.

CONCLUSIONS

An overall weak association between the A1166C polymorphism and CHD is observed but this is likely to be due to publication bias and heterogeneity between studies. There were no significant associations among the larger sample-size and high-quality studies which are less prone to selective publication and have greater power to detect a true association.

The angiotensin converting enzyme D allele is an independent risk factor for early onset coronary artery disease

OBJECTIVE

The role of angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in early onset coronary artery disease age < 55years (ECAD) is controversial. The aim of this study was to further evaluate the role of this ACE(I/D) gene polymorphism on the risk of premature CAD in patients from western Iran.

METHODS

The ACE(I/D) genotypes were detected by PCR-RFLP in 323 individuals undergoing their first coronary angiography. Patients were placed into two groups: ECAD and late onset CAD age ≥ 55years (LCAD).

RESULTS

We found a statistically significant association of the ACE D allele, as homozygous or ACE ID plus DD genotypes (ID+DD), only in the ECAD subjects OR=1.35, p=0.015, OR=3.27, p=0.014, and OR=2.8, p=0.013, respectively. In addition, there was a significant association after adjustment for the absence of history of diabetes, presence of normolipidemia and absence of history of blood pressure [OR 1.38, p=0.017 and 2.35, p=0.02]. Our results indicated that the ACE D allele is a risk factor for early onset of CAD even after correcting for conventional risk factors. The incidence of triple vessel disease was significantly higher in individuals carrying ACE(D/D) genotype in ECAD patients compared to those who carried ACE(I/I) genotype (OR 3.38; p=0.019; 57.5% vs. 42.5%; p=0.013).

CONCLUSION

The presence of D allele of ACE can be important independent risk factor in the onset of CAD patients less than 55 years old in a west population of Iran. Larger collaborative studies are needed to confirm these results.

Angiotensin II type 1 receptor gene A1166C polymorphism and essential hypertension in Chinese: a meta-analysis

Introduction. We performed a meta-analysis with the aim of assessing the association of the angiotensin II type 1 (AT1) receptor gene A1166C polymorphism with essential hypertension in Chinese case-control studies. Methods. Studies were searched from the Chinese Biomedicine Database, the China National Knowledge Infrastructure platform, Pubmed and Medline, using the search terms ‘hypertension’, ‘angiotensin II type 1 receptor’, ‘AT1R’, ‘polymorphism’, ‘China’ and ‘Chinese’, without limiting to any specific language. The strength of the association between the A1166C polymorphism and hypertension was evaluated by the odds ratio (OR) with the corresponding 95% confidence interval (CI). The analyses were performed with Cochrane RevMan software version 4.2.

Results. Overall, the variant genotype AC/CC was associated with a statistically increased essential hypertension risk with the pooled OR 1.48 (95% CI: 1.20—1.83). In the subgroup analyses, the association was also significant among studies using Northern populations, Southern populations, Han Chinese and hospital-based controls. The age did not influence the relationship between the AT 1 receptor A1166C polymorphism and hypertension in the subgroup analyses.

Conclusions. The present meta-analysis suggests that the AT1 receptor 1166 AC/CC genotype is associated with susceptibility to hypertension in the Chinese population.

Genetic variation in the renin-angiotensin system and arterial stiffness. The Rotterdam Study

We studied the associations of three renin-angiotensin system polymorphisms, angiotensin-converting enzyme (ACE) I/D, angiotensinogen 235 M/T, and angiotensin II receptor type I 573 C/T, with arterial stiffness. The study was embedded in the Rotterdam Study, a population-based study older adults. The association of the polymorphisms with pulse wave velocity, the carotid distensibility, and pulse pressure was investigated in 3706 subjects. We found no association of the ACE I/D polymorphism with pulse wave velocity, but the D-allele was associated with a lower distensibility coefficient (p = 0.05) and higher pulse pressure (p = 0.01). For the angiotensinogen 235 M/T polymorphism, no significant associations with either pulse wave velocity (p = 0.71), the distensibility coefficient (p = 0.16) or pulse pressure (p = 0.34) were found. Also, we found no significant associations of pulse wave velocity (PWV) (p = 0.32), the distensibility coefficient (p = 0.08), and pulse pressure (p = 0.09) with the angiotensin II receptor type 1 573 C/T polymorphism. No epistatic effects were observed between the three renin-angiotensin system (RAS) genes with arterial stiffness. Our findings suggest that genetic variation in the renin-angiotensin system may play a role in determining carotid distensibility and pulse pressure.

Independent and combined influence of AGTR1 variants and aerobic exercise on oxidative stress in hypertensives

Abstract Angiotensin II (AngII), via the AngII type 1 receptor (AT(1)R), contributes to oxidative stress. Aerobic exercise training (AEXT) reduces the risk of cardiovascular (CV) disease, presumably by reducing the grade of oxidative stress. We investigated the independent and combined influence of the AGTR1 A1166C and -825 T/A polymorphisms on oxidative stress and plasma AngII responses to AEXT in pre- and stage 1 hypertensives. Urinary 8-iso-PGF(2alpha) significantly increased with AEXT (p=0.002); however, there were no significant changes in superoxide dismutase activity or AngII levels. There was a significant difference in the change in AngII levels with AEXT between A1166C genotype groups (p=0.04) resulting in a significant interactive effect of the A1166C polymorphism and AEXT on the change in AngII (p<0.05). Only the TT genotype group of the -825 T/A polymorphism had a significant reduction in plasma AngII (p=0.02). Risk allele analysis revealed a significant reduction in plasma AngII (p=0.04) and a significant increase in urinary 8-iso-PGF(2alpha) (p=0.01) with AEXT in individuals with two risk alleles only. Our findings suggest that variation in the AGTR1 gene is associated with differential changes in plasma AngII but not oxidative stress.

Angiotensin II type 1 receptor gene polymorphism predicts development of hypertension and metabolic syndrome

BACKGROUND

The aim of the study was to investigate the effect of polymorphism A1166C for AGTR1 and -1332G/A for AGTR2 on the incidence of sustained hypertension (HT) and metabolic syndrome in a cohort of young patients screened for stage 1 HT.

METHODS

We assessed 420 white hypertensive subjects never treated for HT and followed up for 7.3 years in the HT and Ambulatory Recording Venetia Study (HARVEST). Incident physician-diagnosed HT, increase in ambulatory blood pressure (BP), and new onset metabolic syndrome were the outcome measures.

RESULTS

For AGTR1, 37.2% of the subjects in the group with AA genotype, 47.5% in the group with AC genotype, and 66.7% in the group with CC genotype developed HT during follow-up (P = 0.001). Ambulatory systolic (P = 0.007) and diastolic (P < 0.001) BPs increased largely in the patients with CC genotype than in the rest of the group. New onset metabolic syndrome during follow-up (n = 30, P = 0.008), and the frequency of the metabolic syndrome at the end of follow-up (n = 65, P = 0.002) were also more common among the patients with CC and AC genotype. In a Cox analysis, subjects with CC genotype had an increased risk of developing HT (hazard ratio (HR) 1.6, 95% confidence interval (CI) 1.2-2.0, P = 0.000) and metabolic syndrome (HR 2.8, 1.5-5.2, P = 0.002) than AA subjects. No association was found between the AGTR2 polymorphism and any outcome measure.

CONCLUSIONS

The AGTR1 A1166C polymorphism may be considered a genetic marker predisposing to an increase in BP and the development of the metabolic syndrome in subjects screened for stage 1 HT.

Angiotensin II type 1 receptor polymorphisms and susceptibility to hypertension: a HuGE review

The angiotensin II type 1 receptor (AGTR1) plays an integral role in blood pressure control, and is implicated in the pathogenesis of hypertension. Polymorphisms within this gene have been extensively studied in association with hypertension; however, findings are conflicting. To clarify these data, we conducted a systematic review of association studies of AGTR1 polymorphisms and hypertension, and performed a meta-analysis of the rs5186 variant. Results show that the currently available literature is too heterogeneous to draw meaningful conclusions. The definition of hypertension and gender composition of individual studies helps to explain this heterogeneity. Although the structure and splicing pattern of AGTR1 would suggest a likely effect of polymorphisms within the promoter region on gene function, few studies have been conducted thus far. In conclusion, there is insufficient evidence that polymorphisms in the AGTR1 gene are risk factors for hypertension. However, most studies are inadequately powered, and larger well-designed studies of haplotypes are warranted.

Polymorphisms of the renin-angiotensin system are associated with blood pressure, atherosclerosis and cerebral white matter pathology

BACKGROUND

The renin-angiotensin system is involved in the development of hypertension, atherosclerosis and cardiovascular disease. We studied the association between the M235T polymorphism of the angiotensinogen gene (AGT) and the C573T polymorphism of the angiotensin II type 1 receptor (AT1R) and blood pressure, carotid atherosclerosis and cerebrovascular disease.

METHODS

We genotyped over 6000 subjects from the Rotterdam Study and more than 1000 subjects from the Rotterdam Scan Study. We used logistic regression and univariate analyses, adjusting for age and sex with, for AGT, the MM and, for AT1R, the TT genotype as reference.

RESULTS

We found that AGT-235T increased systolic (p for trend = 0.03) and diastolic blood pressure (p for trend = 0.04). The prevalence of carotid plaques was increased 1.25-fold (95% CI 1.02-1.52) in AGT-TT carriers. There was a significant increase in mean volume deep subcortical white matter lesions (WML) for AGT-TT carriers (1.78 ml vs 1.09 ml in the reference group; p = 0.008). A significant interaction was found between AGT and AT1R, further increasing the effect on periventricular and subtotal WML (p for interaction = 0.02). We found a non-significant increased risk of silent brain infarction for AGT-TT carriers and AT1R-CC carriers, but no effect on stroke.

CONCLUSION

We found an association between AGT and blood pressure, atherosclerosis and WML. Also, we found synergistic effects between AGT and AT1R on the development of WML. These findings raise the question of whether the renin-angiotensin system may be a therapeutic target for the prevention of cerebral white matter pathology.

Renin-angiotensin-aldosterone system polymorphisms: a role or a hole in occurrence and long-term prognosis of acute myocardial infarction at young age

Background

The renin-angiotensin-aldosterone system (RAAS) is involved in the cardiovascular homeostasis as shown by previous studies reporting a positive association between specific RAAS genotypes and an increased risk of myocardial infarction. Anyhow the prognostic role in a long-term follow-up has not been yet investigated.

Aim of the study was to evaluate the influence of the most studied RAAS genetic Single Nucleotide Polymorphisms (SNPs) on the occurrence and the long-term prognosis of acute myocardial infarction (AMI) at young age in an Italian population.

Methods

The study population consisted of 201 patients and 201 controls, matched for age and sex (mean age 40 ± 4 years; 90.5% males). The most frequent conventional risk factors were smoke (p < 0.001), family history for coronary artery diseases (p < 0.001), hypercholesterolemia (p = 0.001) and hypertension (p = 0.002). The tested genetic polymorphisms were angiotensin converting enzyme insertion/deletion (ACE I/D), angiotensin II type 1 receptor (AGTR1) A1166C and aldosterone synthase (CYP11B2) C-344T. Considering a long-term follow-up (9 ± 4 years) we compared genetic polymorphisms of patients with and without events (cardiac death, myocardial infarction, revascularization procedures).

Results

We found a borderline significant association of occurrence of AMI with the ACE D/I polymorphism (DD genotype, 42% in cases vs 31% in controls; p = 0.056). DD genotype remained statistically involved in the incidence of AMI also after adjustment for clinical confounders.

On the other hand, during the 9-year follow-up (65 events, including 13 deaths) we found a role concerning the AGTR1: the AC heterozygous resulted more represented in the event group (p = 0.016) even if not independent from clinical confounders. Anyhow the Kaplan-Meier event free curves seem to confirm the unfavourable role of this polymorphism.

Conclusion

Polymorphisms in RAAS genes can be important in the onset of a first AMI in young patients (ACE, CYP11B2 polymorphisms), but not in the disease progression after a long follow-up period. Larger collaborative studies are needed to confirm these results.

Quantitated transcript haplotypes (QTH) of AGTR1, reduced abundance of mRNA haplotypes containing 1166C (rs5186:A>C), and relevance to metabolic syndrome traits

The angiotensin II type 1 receptor (AGTR1) is the main target through which angiotensin II influences cardiovascular tone, cell growth, and fluid and electrolyte balance. AGTR1 polymorphism has been reported to associate with hypertension, myocardial infarction (MI), and metabolic traits. Here we describe a novel approach to quantitation of transcript haplotypes (QTH) of AGTR1. To determine relative allelic expression from haplotypes, within-individual-between-allele ratiometric analyses in placental cDNA were developed for the transcribed SNPs rs5182:C>T (encoding p.L191) and rs5186:A>C (3'-noncoding "A1166C"). Additionally, between-individual comparisons were made using TaqMan assays applied to both homozygous and heterozygous genotypes and haplotypes. In conjunction, linkage disequilibrium (LD) and genomic haplotype associations with metabolic syndrome were examined. There was no significant difference of mRNA level for alleles of rs5182:C>T, but allele and mRNA haplotypes carrying 1166C exhibited reduced abundance. The effect was much greater in CC homozygotes than in heterozygotes. The promoter region was confirmed to be in a separate haplotype block from the AGTR1 3' region containing rs5182:C>T and rs5186:A>C. Metabolic syndrome trait associations were strongest for the 3' block generally and for the C allele of rs5186:A>C specifically. All effects were much more prominent in homozygotes, possibly reflecting interallelic interaction through feedback loops of mRNA regulation. Differential abundance of AGTR1 mRNA haplotypes may mediate clinical phenotypic observations of the AGTR1 genotype.

Heritability of blood pressure traits and the genetic contribution to blood pressure variance explained by four blood-pressure-related genes

OBJECTIVE

To study the heritability of four blood pressure traits and the proportion of variance explained by four blood-pressure-related genes.

METHODS

All participants are members of an extended pedigree from a Dutch genetically isolated population. Heritability and genetic correlations of systolic blood pressure, diastolic blood pressure, mean arterial pressure and pulse pressure were assessed using a variance components approach (SOLAR). Polymorphisms of the alpha-adducin (ADD1), angiotensinogen (AGT), angiotensin II type 1 receptor (AT1R) and G protein beta3 (GNB3) genes were typed.

RESULTS

Heritability estimates were significant for all four blood pressure traits, ranging between 0.24 and 0.37. Genetic correlations between systolic blood pressure, diastolic blood pressure and mean arterial pressure were high (0.93-0.98), and those between pulse pressure and diastolic blood pressure were low (0.05). The ADD1 polymorphism explained 0.3% of the variance of pulse pressure (P = 0.07), and the polymorphism of GNB3 explained 0.4% of the variance of systolic blood pressure (P = 0.02), 0.2% of mean arterial pressure (P = 0.05) and 0.3% of pulse pressure (P = 0.06).

CONCLUSION

Genetic factors contribute to a substantial proportion of blood pressure variance. In this study, the effect of polymorphisms of ADD1, AGT, AT1R and GNB3 explained a very small proportion of the heritability of blood pressure traits. As new genes associated with blood pressure are localized in the future, their effect on blood pressure variance should be calculated.

Association between angiotensinogen, angiotensin II receptor genes, and blood pressure response to an angiotensin-converting enzyme inhibitor

BACKGROUND

To identify the genetic contribution to the variation in blood pressure (BP) response to angiotensin-converting enzyme inhibitors (ACEIs), single-nucleotide polymorphisms (SNPs) in the angiotensinogen (AGT), angiotensin receptor 1 (AGTR1), and angiotensin receptor 2 (AGTR2) genes were evaluated for their association with BP response to ACEI in Chinese patients with hypertension in a 2-stage design.

METHODS AND RESULTS

We selected 1447 hypertensive patients from a 3-year benazepril postmarket surveillance trial and genotyped them for 14 SNPs in the AGT, AGTR1, and AGTR2 genes. The AGT rs7079 (C/T) SNP (3'-untranslated region) was significantly associated with the response of diastolic BP to benazepril (diastolic BP response: -7.4 mm Hg for subjects with the CC genotype, -8.9 mm Hg for CA, and -10.1 mm Hg for AA; P=0.001). Although there was no association of individual SNPs in the AGTR1 gene, there was a graded response between common haplotypes and systolic BP reduction in the order of haplotype 2 (H2)/lack of haplotype 3 (non-H3) (-13.6 mm Hg) > non-H2/non-H3 (-10.9 mm Hg) > H3/non-H2 (-6.6 mm Hg) (P=0.004). The total variations in response to ACEI therapy that were explained by the AGT SNP and AGTR1 haplotype groups were 13% for systolic and 9% to 9.6% for diastolic BP, respectively.

CONCLUSIONS

AGT SNP rs7079 and AGTR1 haplotypes were associated with BP reduction in response to ACEI therapy in hypertensive Chinese patients. This will be useful in future studies, providing genetic markers to predict the hypertensive response to ACEI therapy.

Restenosis after percutaneous coronary intervention is associated with the angiotensin-II type-1 receptor 1166A/C polymorphism but not with polymorphisms of angiotensin-converting enzyme, angiotensin-II receptor, angiotensinogen or heme oxygenase-1

OBJECTIVES

The renin-angiotensin system (RAS) is thought to play a major role in the pathophysiology of de-novo restenotic lesions and in-stent restenosis after percutaneous coronary intervention (PCI). Heme oxygenase-1 (HO-1), is thought to beneficially influence these processes. We examined the effect of pharmacologic as well as genetic RAS interactions on restenosis in a large population of consecutive patients undergoing PCI, and evaluated possible gene-gene interactions in both systems.

METHODS

The GENDER project is a multicenter prospective follow-up study, including 3146 patients after successful PCI. Genotyping in these patients was performed for the ACE gene insertion/deletion, the angiotensinogen 235Met/Thr, T174M and A(-6)G, the angiotensin-II type 1 receptor (AT1R) 1166A/C and T810A, the angiotensin-II type 2 receptor (AT2R) 1675G/A and 3123A polymorphisms and the length polymorphism in the HO-1 promoter region.

RESULTS

A total of 3104 patients were followed for 10 months. In 2975 patients at least one of the nine genotypes could be determined. The AT1R 1166 CC genotype showed a significant association with TVR; the other polymorphisms did not. RAS-inhibitory drugs were not associated with the incidence of TVR, nor did they interact with any of the investigated polymorphisms. Patients with the ACE I/I polymorphism showed a trend towards a better outcome if they had a short number of repeats in the HO-1 promoter. This relationship was inversely present in carriers of the ACE D/D polymorphism.

CONCLUSION

We could only establish a role for the AT1R 1166A/C polymorphism in restenosis after PCI. However, significant gene-gene interaction was suggested for the ACE gene and the HO-1 promotor. The RAS and HO-1 relation in restenosis merits further investigation.

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.

Angiotensin II type I receptor gene polymorphism: anthropometric and metabolic syndrome traits

BACKGROUND

The renin angiotensin system is important in the regulation of vascular tone and fluid and electrolyte balance. The angiotensin converting enzyme gene (ACE) genotype has been shown to affect exercise response and glucose load response dependent on birth weight. Angiotensin II type I receptor (AGTR1) A1166C has previously been associated with the development of hypertension and coronary disease, but its metabolic effects have not been investigated.

METHOD

AGTR1 A1166C was genotyped by allele specific PCR in 378 individuals from Hertfordshire, UK, who had been characterised for metabolic syndrome traits.

RESULTS

Genotype counts were: AA, 183; AC, 170; CC, 25, consistent with Hardy-Weinberg equilibrium. The CC genotype was associated with significantly lower body mass index (by 1.7 units) in men (p = 0.03), and the same magnitude effect in women with significant lower weight in both genders (p = 0.01), also lower waist circumference and waist-hip ratio (p = 0.01) in men, with a trend for lower waist circumference in women also. Additionally, the CC genotype and/or C allele was associated with lower fasting glucose and insulin, and 30 and 120 min glucose in men (respectively, p = 0.08, 0.04, 0.01, 0.06). Lower means of systolic blood pressure, pulse pressure, cholesterol, and fasting triglyceride were also observed for the CC genotype in both genders though these were not statistically significant.

CONCLUSIONS

The AGTR1 1166 CC genotype appears to predispose to favourable anthropometric and metabolic traits, relative to cardiovascular risk.

Genetic contribution to the acute effects of angiotensin II type 1 receptor blockade

OBJECTIVE

Clinical observations point towards heterogeneity in patients' responses to antihypertensive drugs. As our earlier work showed that angiotensin II (AngII) sensitivity is associated with the A1166C polymorphism of the AngII type 1 receptor (AT1R) gene, we conducted the present study in which the responses to acute AT1R blockade were evaluated.

METHODS

After 7 days of low and high sodium diet, the hormonal as well as systemic and renal hemodynamic responses to acute AT1R blockade with EXP3174 (active metabolite of losartan) were studied in 15 AA and 14 CC essential hypertensive patients. By means of platelet-binding studies the baseline AT1R density (Bmax) and affinity (KD) was tested.

RESULTS

During low and high salt diet, baseline Bmax and KD were comparable between both genotype groups. At baseline, during low salt diet, CC patients had significantly lower glomerular filtration rate and a trend towards lower effective renal plasma flow (ERPF) compared to AA patients. Blood pressure responses to EXP3174 during high salt were significantly blunted in CC patients compared to AA patients (mean arterial pressure: 1.8 versus 7.5%; P < 0.05). During low salt the increase in ERPF (12.9 versus 16.1%; P = 0.08), as well as the decrease in filtration fraction (9.0 versus 14.0%; P = 0.05) and renal vascular resistance (7.5 versus 15.1%; P = 0.06) were blunted in CC patients compared to AA patients. Humoral effects did not differ between the groups.

CONCLUSION

This study shows that the systemic and renal hemodynamic responses to acute AT1R blockade are, at least in part, genetically determined.

Polymorphism in angiotensin II receptor genes and hypertension

Molecular variants of individual components of the renin-angiotensin system (RAS) have been thought to contribute to an inherited predisposition towards essential hypertension. The angiotensin II type 1 receptor (AT-1) mediates the major pressor and trophic actions of angiotensin II (Ang II) and at least 50 different polymorphisms have been described in the AT-1 gene (AT(1)R gene); in particular, the C allele of the +1166A/C polymorphism has been associated with the severe form of essential hypertension, but the role of this polymorphism is still ambiguous in pathologies related to high Ang II levels, such as deterioration of renal function, arterial stiffness and hypertrophic cardiomyopathy. A relationship was suggested between AT 1R A1166C polymorphism and the humoral and renal haemodynamic responses to losartan, an AT-1 blocker, as well as with enhanced Ang II vascular reactivity or sensitivity. Polymorphism has also been described in angiotensin II type 2 receptor (AT-2) gene, AT-2 being the mediator for vasodilatation, natriuresis and apoptosis of smooth muscle cells; associations were found between some of these polymorphisms and both hypertension and left ventricular structure. Further evaluation in adequately powered studies is necessary for full assessment of the allelic markers in genes for RAS components, as well as to allow determination of a predisposition to hypertension or related diseases and selection of an appropriate antihypertensive drug for an individual.

F2-Isoprostane level is associated with the angiotensin II type 1 receptor -153A/G gene polymorphism

Recent studies have shown that F2-isoprostane levels-a marker for lipid peroxidation-are increased in human renovascular hypertension but not in essential hypertension. Angiotensin II specifically stimulates F2-isoprostane production through activation of the AT1 receptor. The objective was to determine whether there is a relationship between the level of oxidative stress evaluated by measuring urinary F2-isoprostanes levels and polymorphisms of genes involved in the renine angiotensin aldosterone system (RAAS) regulation. The population studied included 100 subjects, 65 of whom were healthy normotensives; the other 35 were suffering from untreated, essential hypertension. The polymorphisms studied concern the genes encoding angiotensin I-converting enzyme (ACE/in16del/ins), angiotensin II receptor type I (AGTR1/A+39C[A+1166C] and AGTR1/A-153G), angiotensinogen (AGT/M235T), and aldosterone synthase (CYP11B2/T344C). Oxidative stress was evaluated by measuring urinary F2-isoprostanes levels. The characteristics of the population were as follows: men/women = 46/56; age = 50 +/- 10 years; BMI = 24 +/- 3 kg/m2; SBP = 131.7 +/- 17.2 mm Hg; DBP = 84.6 +/- 10.4 mm Hg. In univariate analysis, urinary F2-isoprostane levels were significantly lower in the presence of the G allele of AGTR1/A-153G (56 +/- 17 vs 76 +/- 39 pmol/mmol creatinine; P < 0.001, and P < 0.01 after Bonferroni correction for 10 tests). In multivariate analysis, taking into account BP, age, gender, BMI, plasma glucose, and total cholesterol, the G allele of AGTR1/A-153G is linked independently to urinary F2-isoprostanes level (P < 0.01). Our data suggest that F2-isoprostane level depends at least in part on the A-153G polymorphism of the angiotensin II AT1 receptor gene. The clinical and prognostic relevance of this polymorphism requires further investigation.

Haplotypes of the angiotensin II receptor genes AGTR1 and AGTR2 in women with normotensive pregnancy and women with preeclampsia

Angiotensin II (AII) acts as a growth factor in local systems, mediating diverse effects such as cellular proliferation and apoptosis. These effects are controlled through two main receptor subtypes: AGTR1 and AGTR2. We studied the haplotype frequencies of both receptor genes in women with preeclamptic pregnancies and normotensive pregnant women. We also looked for any association between AGTR1 genotype at sites in the 5' flanking region and binding of AII to platelets, which express AGTR1, in 58 normotensive pregnant women. There were nine common haplotypes of AGTR1, with no significant difference in haplotype frequency between the two groups of women. Platelet AII binding in normotensive pregnant women was associated with the genotype at g.5245C>T in the 5' flanking region of AGTR1 (GenBank AF245699.1), with CC homozygotes at g.5245 having the lowest levels, and g.5245 TT homozygotes having the highest levels (P=0.05). Two novel polymorphisms were identified in AGTR2 (GenBank AY324607.1) at nucleotides g.1701T>C and g.2184A>T. Variation of AGTR2 could be explained by the existence of four common haplotypes. There was evidence for a significant increase in the frequency of the haplotype TAATGC at nucleotides g.1701, g.2041, g.2184, g.4673, g.4679, and g.4975, respectively (P=0.004), in women with preeclampsia.

Angiotensin II type I receptor gene and myocardial infarction

OBJECTIVES

The present study aimed to assess the effect of haplotype variation in angiotensin II type I receptor (AGTR1) gene on the risk of myocardial infarction (MI) in Chinese males.

METHODS

We used 48 patients to identify the putative functional polymorphisms in AGTR1 gene by direct sequencing. The program tagSNPs was used to identify an optimal set of tagging single nucleotide polymorphisms (SNPs). These selected SNPs were then genotyped in 419 male patients with MI and 400 age-matched male controls. The program haplo.stats was used to investigate the relationship between the haplotypes and MI.

RESULTS

Sixteen polymorphisms in AGTR1 gene were identified. Based on the linkage disequilibrium pattern among these SNPs, six polymorphisms, SNP1, SNP6-SNP7 and SNP13-SNP15, were selected as haplotype tagging SNPs and further genotyped. Single SNP analyses indicated that the SNP1, SNP6 and SNP13 were significantly associated with MI, adjusted for covariates. Haplotype-based association analyses identified the frequency of haplotype AGATAA was lower in cases than in controls (P = 0.006). In comparison, three haplotypes (AAATAA, TAGCAA and AAACAG) were found to significantly increase the risk of MI with adjusted odds ratio equal to 1.33, 1.75 and 2.64, respectively (P = 0.029, 0.026 and 0.015).

CONCLUSIONS

Our study suggests that common genetic variations in the AGTR1 gene may affect the risk of MI in Chinese males, and that there might be several functional variants in AGTR1 gene and the combined effect of these variants seemed to have a larger effect on the risk of MI in Chinese males.

Automated detection of informative combined effects in genetic association studies of complex traits

There is a growing body of evidence suggesting that the relationships between gene variability and common disease are more complex than initially thought and require the exploration of the whole polymorphism of candidate genes as well as several genes belonging to biological pathways. When the number of polymorphisms is relatively large and the structure of the relationships among them complex, the use of data mining tools to extract the relevant information is a necessity. Here, we propose an automated method for the detection of informative combined effects (DICE) among several polymorphisms (and nongenetic covariates) within the framework of association studies. The algorithm combines the advantages of the regressive approaches with those of data exploration tools. Importantly, DICE considers the problem of interaction between polymorphisms as an effect of interest and not as a nuisance effect. We illustrate the method with three applications on the relationship between (1). the P-selectin gene and myocardial infarction, (2). the cholesteryl ester transfer protein gene and plasma high-density-lipoprotein cholesterol concentration, and (3). genes of the renin-angiotensin-aldosterone system and myocardial infarction. The applications demonstrated that the method was able to recover results already found using other approaches, but in addition detected biologically sensible effects not previously described.

The angiotensin II receptor (Agtr1a): functional regulatory polymorphisms in a locus genetically linked to blood pressure variation in the mouse

Hypertension is a complex trait with multiple genetic determinants. A previous genome-wide linkage study of systolic blood pressure in a mouse genetic backcross implicated a region of chromosome 13 (LOD = 3.3 at 16.0 cM) as a determinant of blood pressure differences between a hereditary low blood pressure strain of Mus musculus (BPL/1) and Mus spretus (SPRET); at this locus, the unexpected effect of the BPL/1 allele was to increase blood pressure. A plausible candidate locus encoding angiotensin II receptor isoform 1a (Agtr1a) is also located at 16.0 cM on chromosome 13. We therefore investigated structural and functional differences at Agtr1a between BPL/1 and SPRET, as well as the BPH/2 strain. Resequencing Agtr1a in the three strains established the exon/intron and proximal promoter structure of the mouse gene. Coding exon 3 spanned 1,960 bp (with 26 SNPs), including the 1,077-bp/359-amino acid ORF (with 5 cSNPs, all of which were synonymous). Promoter sequences revealed a consensus TATA box, conserved G/C-rich regions, and a striking, lengthy simple sequence repeat region, composed of di-, tri-, tetra-, and penta-nucleotide repeats, whose overall length varied markedly among the strains. Twenty-five other SNPs and three single nucleotide deletions differentiated the strains' promoters, six of which were in likely functional promoter motifs. Agtr1a mRNA abundance in the adrenal gland in vivo was greater (P < 0.05) in BPL/1 than SPRET, consistent with the predicted effect of the BPL/1 allele to confer higher blood pressure. When Agtr1a promoters were subcloned into luciferase reporter plasmids and transfected into PC12 chromaffin cells, basal promoter expression was higher (P < 0.001) in BPL/1 than in SPRET, consistent with the endogenous mRNA results. In summary, Agtr1a on chromosome 13 is highly polymorphic between mouse strains, although the amino acid sequence specified by the ORF is invariant, even across mouse species. We conclude that polymorphisms in the Agtr1a promoter account for differences in gene expression in vivo between BPL/1 and SPRET, in a way consistent with the effects of alleles at this locus on chromosome 13 to affect blood pressure in the mouse genome-wide linkage study.

Interactions between gender and the angiotensin type 1 receptor gene polymorphism

BACKGROUND

The cardiovascular effects of angiotensin II are mediated by the angiotensin II type 1 receptor (AGT1R); one polymorphism of the AGT1R gene, A1166-->C, has been associated with hypertension. The hemodynamic response to angiotensin II is blunted in women compared to men, but interactions between gender, blood pressure, and AGT1R gene polymorphisms are unclear.

METHODS

A total of 81 young healthy normotensive individuals maintained regulated sodium and protein intake prior to study. They were divided into four groups based on gender and A1166-->C genotype (AA versus AC/CC); serial supine blood pressures were obtained. A subset of 52 individuals received graded infusions of angiotensin II. Inulin and paraaminohippurate clearance techniques were used to measure renal hemodynamic function at baseline and in response to the infusions.

RESULTS

Men with the AC/CC genotype exhibited higher blood pressures than men with the AA genotype; however, this relationship was not found among women. Analysis of covariance revealed a significant interaction between gender and AGT1R genotype in the determination of blood pressure. Glomerular filtration rate (GFR) declined variably in the study subjects following infusion of angiotensin II, and a statistical model incorporating gender and genotype best predicted the fall in GFR. There was a trend for females of the AA genotype to have a greater fall in GFR in response to angiotensin II infusion, than any of the other groups.

CONCLUSION

In young healthy subjects, there is an important interaction between gender, the AGT1R A1166-->C gene polymorphism, and blood pressure. In addition, the renal hemodynamic response to angiotensin II infusion is a function of both gender and the AGT1R genotype.

Renin-angiotensin gene polymorphism in children with uremia and essential hypertension

The M235T polymorphism of the angiotensinogen (ANG) gene, the I/D polymorphism of the angiotensin converting enzyme (ACE) gene, and the A1166C polymorphism of the angiotensin II type 1 receptor (AT1R) gene were identified in 70 patients with end-stage renal disease [20 pediatric ESRD, aged 14.9+/-3.1, years blood pressure (BP) 139+/-14/91+/-13 mmHg, 50 adult ESRD, aged 48.7+/-18.7 years, BP 149.1+/-24/96.9+/-12 mmHg], 35 with juvenile essential hypertension (JEHT, aged 14.4+/-2.7 years, 24-h mean BP 135.37+/-7.37/72.4+/-7.68 mmHg), 130 adult healthy normotensive controls (aged 34.9+/-8.1 years, BP 117.8+/-8.7/78.7+/-8.5 mmHg), and 20 pediatric controls (aged 13.2+/-1.2 years, BP 109+/-6.5/71+/-5.9 mmHg). The ACE gene polymorphism was determined by polymerase chain reaction and the ANG and AT1R gene polymorphisms by single-step LightCycler technology. The ACE gene distribution of the Hungarian controls did not differ from the results of the other Caucasian populations. In JEHT and pediatric ESRD patients, the MT genotype of ANG was more frequent than in controls (JEHT 80%, pediatric ESRD 74% versus controls 50%, P<0.02). The DD genotype of ACE was over-represented in pediatric ESRD compared with controls (ESRD 45% versus controls 22%, P<0.05). There was a non-significant increase in the CC genotype frequency of AT1R in adult patients with ESRD compared with controls. In conclusion, there was an increased frequency of the ACE DD genotype in pediatric ESRD, which could be a genetic risk factor for the development of ESRD. Furthermore, there was a significant increase in MT genotype frequency of ANG M235T polymorphism in pediatric ESRD and JEHT. The role of AT1R gene polymorphism needs further investigation.

Interaction between gene polymorphisms of renin-angiotensin system and metabolic risk factors in premature myocardial infarction

The renin-angiotensin system is involved in the pathogenesis of coronary artery disease (CAD) and myocardial infarction (MI). The authors investigated the association of genetic variability in the renin-angiotensin system (RAS) with premature MI and interactive effects between gene polymorphisms and metabolic risk factors on MI risk. Their study compared 142 patients with MI younger than 55 years with 142 healthy subjects. Polymorphisms of angiotensin-I converting enzyme (ACE) gene (insertion/deletion), angiotensinogen gene (M235T), and angiotensin-II type-1 receptor (AGT1R) gene (A1166C) were tested. The ACE-DD (deletion/deletion) genotype conferred a twofold independent risk for MI (confidence interval [CI] = 1.1-3.7; p = 0.01) after adjustment for cardiovascular risk factors, whereas angiotensinogen-TT genotype and AGT1R-AA genotype were not independent risk factors for MI. An interactive effect on MI risk was found between ACE-DD and AGT1R-AA genotypes (odds ratio [OR]=2, 95% CI= 1-3.9), between ACE-DD and angiotensinogen-TT genotypes (OR = 2.7, 95% CI = 1-7.3), as well as among ACE-DD, angiotensinogen-TT, and AGT1R-AA genotypes (OR=4.8, 95% CI = 1-22.8). Similarly, metabolic risk factors interacted with angiotensinogen-TT genotype (OR= 2, 95% CI = 1.1-3.9) on MI risk. The ACE-DD genotype is an independent risk factor for MI in patients younger than 55 years. Additionally, the authors provide evidence of an interactive effect on MI risk between risk genotypes of RAS, as well as between the angiotensinogen-TT genotype and metabolic risk factors.

Angiotensin II type 1 receptor-153A/G and 1166A/C gene polymorphisms and increase in aortic stiffness with age in hypertensive subjects

OBJECTIVES

Arterial stiffness is associated with excess morbidity and mortality, independently of other cardiovascular risk factors. Age is the main determinant responsible for arterial wall changes leading to arterial stiffening. Environmental and genetic factors may however influence the magnitude of the effects of age on large artery stiffness.

DESIGN AND METHODS

The present study assessed whether or not the relationship between age and aortic stiffness was influenced by genetic variants of angiotensinogen (AGT 174T/M, 235M/T), angiotensin converting enzyme (ACE I/D), angiotensin II type 1 receptor (AT1 1166A/C, -153A/G) and aldosterone synthase (CYP11B2 -344T/C). This study was realized in 441 untreated hypertensive subjects of European origin (aged 18-74 years). Aortic stiffness was assessed by carotid-femoral pulse wave velocity (PWV).

RESULTS

Carriers of the angiotensin II type 1 receptor -153G allele showed a steeper age/PWV relationship than the AT1 -153AA subjects. The effect of the AT1 -153A/G polymorphism on aortic stiffness became apparent after the age of 55 years. In subjects with the AT1 1166C allele, the relationship age/PWV is shifted upward, indicating higher values of aortic stiffness at any age compared to the AT1 1166AA patients. Carriers of both the AT1 1166C and -153G alleles presented the additive effects of these 2 genotypes on aortic stiffness. Angiotensinogen, ACE and CYP11B2 genotypes did not influence the effects of age on PWV.

CONCLUSIONS

AT1 receptor genotypes could influence arterial ageing in hypertensive subjects. These results also show that the association between genotypes and arterial stiffness may manifest itself later in life.

Genetic background in patients with acute myocardial infarction

The renin-angiotensin system is believed to play important roles in the development of acute myocardial infarction, and gene polymorphisms may also be involved. To investigate the genetic background in patients with acute myocardial infarction, we performed a case control study in a Japanese population. The study included 150 patients with acute myocardial infarction and 150 healthy, age- and sex-matched controls. We examined polymorphisms of angiotensin II type 1 receptor (1 166 A / C), type 2 receptor (3123 C / A), and bradykinin B2 receptor (-58 T / C) in these subjects. The allelic frequencies of angiotensin II type I receptor C and angiotensin II type 2 receptor A were significantly higher in the acute myocardial infarction subjects than in the control subjects, and this tendency was more significant in the younger patients. The combined ratios of angiotensin II type 1 receptor C and type 2 receptor A alleles in patients under 64 years old were significantly higher than in their older counterparts. However the total numbers of conventional coronary risk factors (hypertension, hypercholesterolemia, diabetes mellitus, and smoking) in individual subjects were not significantly different between younger and older patients. These polymorphisms were found to be involved in the development of acute myocardial infarction, particularly in the younger patients, and it was concluded that the incidence of acute myocardial infarction might be reduced by management from the genotypes.

Angiotensin II type 1 receptor gene polymorphisms in humans: physiology and pathophysiology of the genotypes

Many studies have attempted to relate genetic variants of components of the renin-angiotensin system to complex diseases such as essential hypertension, cardiovascular disease and progressive renal failure. The angiotensin II type 1 receptor (AT1R) gene is an important example of this approach. Many polymorphisms of the AT1R gene have been identified, but the A1166-->C polymorphism has been the most extensively studied. The physiological significance of this polymorphism is uncertain because of its location in the 3'-untranslated region of the gene. The present review summarizes association studies of the AT1R gene, focusing on clinical end-points and physiological responses.

Genetic polymorphisms in the renin-angiotensin system: relevance for susceptibility to cardiovascular disease

The renin-angiotensin system plays an important role in the pathogenesis of cardiovascular disease. Cloning of the human genes coding for the angiotensin-converting enzyme, angiotensinogen, and angiotensin II type 1 receptor has led to the discovery of several polymorphisms, which may be implicated in the pathogenesis of cardiovascular disease. The deletion/insertion (D/I) polymorphism of the angiotensin-converting enzyme gene is associated with hypertension in men, left ventricular hypertrophy in untreated hypertensive patients, various atherosclerotic cardiovascular complications, and microvascular disorders. The M235T polymorphism of the angiotensinogen gene may be associated with a higher risk of hypertension. The A1166C polymorphism of the angiotensin II type 1 receptor gene is probably correlated with hypertension and through an epistatic interaction with the D/I polymorphism of the angiotensin-converting enzyme gene possibly also with coronary heart disease. Several other gene polymorphisms, in particular those in the promoter area of the angiotensinogen gene, have been studied in relation to cardiovascular disease. Based on the insights gained from the reports summarized in this review article, population-based genetic studies of nuclear families are currently being conducted in Belgium and in the People's Republic of China with blood pressure and hypertension as the main outcome variables.

Lack of association between polymorphisms of angiotensin II receptor genes and response to short-term angiotensin II infusion

OBJECTIVES

The physiological effects of polymorphisms of the renin-angiotensin-aldosterone system (RAAS) are poorly understood. Long-term effects of genetic variants can be studied in cross-sectional linkage studies. In this study, we examined the short-term effects of genetic polymorphisms of the angiotensin II AT1 - and AT2-receptor subtypes in humans by means of angiotensin II infusion.

METHODS

In 120 male, white, young (26 +/- 3 years) subjects with normal or mildly elevated blood pressure, changes in mean arterial blood pressure, aldosterone levels, glomerular filtration rate (GFR), and renal plasma flow (RPF) were measured in response to angiotensin II infusion (0.5 ng/kg per min and 3.0 ng/kg per min, each over 30 min). The -2228 G/A polymorphism of the AT1-receptor gene, and the +1675 G/A polymorphism of the AT2-receptor gene were determined by restriction digestion and single strand conformation polymorphism analysis, respectively.

RESULTS

Infusion of angiotensin II resulted in an increase in mean arterial pressure, serum aldosterone levels and GFR, and in a decrease in RPF (all P< 0.001). However, at similar baseline mean arterial pressure, aldosterone levels, and renal haemodynamics, the response to angiotensin II did not significantly differ across the AT1 - and AT2-receptor genotypes with the sample size of our study being adequate to detect relevant differences across the genotypes with a power of > 90% for all parameters.

CONCLUSIONS

The response to angiotensin II infusion does not differ across the the AT1- and AT2-receptor genotypes examined in our study. However, long-term effects of variants of angiotensin II receptor genes cannot be ruled out with this approach.

Genetic determination of human essential hypertension

Recent advances in genetic determination of human essential hypertension (EHT) are discussed by reviewing the candidate genes. Candidate genes have been selected based on genetic information from classical linkage analysis (affected sib-pair analysis) or mendelian hypertension (autosomal dominant inheritance of hypertension). Most of these genes are, directly or indirectly, coupled to salt handling of the kidney, being included in the renin-angiotensin system (RAS), steroid-hormone metabolism, and renal sodium transporters. Angiotensinogen (AGT) gene in RAS was first described as a strong candidate associated with the onset of hypertension, since sib-pair linkage analysis has demonstrated the trait loci for hypertension which includes the coding region for AGT. M235T polymorphism of AGT has been studied extensively in many populations including Japanese, and the results suggest a weak, but significant linkage with hypertension. The presence (insertion [I]) or absence (deletion [D]) of 287bp in intron 16 of angiotensin converting enzyme gene has also been examined in RAS, and the results suggest D polymorphism as a risk factor for hypertension in men. Other components in RAS, such as renin, angiotensinogen II type I receptor, or kallikrein have also been studied, but the available information is still incomplete. Genetic investigations of mendelian hypertension has identified the genetic mechanisms for glucocorticoid remediable aldosteronism, apparent mineral corticoid excess, and Liddle's syndrome as chimeric gene duplications of CYP11B1 (aldosterone synthase gene) and CYP11B2 (11beta-hydroxylase gene), mutations in the gene of 11beta-hydroxysteroid dehydrogenase type 2 that catalyzes the conversion of cortisol to cortisone, and mutations in beta or gamma subunit of epithelial sodium channel (ENaC), respectively. Subsequently, genetic variants of CYP11B2 and beta or gamma subunit of ENaC have been found, suggesting the -344C polymorphism of CYP11B2, 594S variant of betaENaC, and two rare variants of gammaENaC as risk factors for EHT. In spite of the extensive research, haplotypes in individual populations remain to be elucidcated in most candidate genes. Even casual conclusions of possible linkage with EHT need to be further examined with better determinations of phenotypes, such as ambulatory and home blood pressure monitoring or identification of onset of hypertension in cohort studies.

Angiotensin II sensitivity is associated with the angiotensin II type 1 receptor A(1166)C polymorphism in essential hypertensives on a high sodium diet

Several investigations have shown heterogeneity in the functional responses to angiotensin II (Ang II) in patients with essential hypertension. The present study was initiated to evaluate whether the A(1166)C polymorphism of the Ang II type 1 receptor (AT(1)R) gene contributes to this variability in Ang II responses. After 7 days of a high-sodium diet (220 mmol Na(+) per day), we measured in 42 essential hypertensive patients blood pressure, heart rate, effective renal plasma flow (ERPF), glomerular filtration rate (GFR), active plasma renin concentration, aldosterone, and atrial natriuretic peptide (ANP) before and during Ang II infusion (increasing doses of 0.3, 1.0, and 3.0 ng/kg per minute). Calculated variables were filtration fraction and renal vascular resistance (RVR). Patients in the 3 genotype groups (AA: n=14; AC: n=17; CC: n=11) were matched for gender, age, and body mass index. At baseline, CC patients had decreased GFR (P:=0.06) and aldosterone (P:<0.05) and increased ANP (P:<0.05) compared with AA patients. Moreover, responses of ERPF, GFR, and RVR to the lowest concentration of Ang II (0.3 ng/kg per minute) were more pronounced in CC patients than in AA patients (ERPF/GFR: P:<0.05; RVR: P:=0.07), whereas maximal responses were all comparable between the groups. Heart rate was decreased at all levels of Ang II infusion in CC patients, while it did not change in AA or AC patients. There were no differences in responses of active plasma renin concentration, aldosterone, and ANP to Ang II between the 3 groups. From these data, we conclude that the C allele of the AT(1)R A(1166)C polymorphism is associated with increased sensitivity but not reactivity to Ang II. An augmented response to Ang II may well be responsible for the increased incidence of cardiovascular abnormalities found in patients with 1 or 2 C alleles.

Angiotensin II type 1 receptor A1166C gene polymorphism is associated with an increased response to angiotensin II in human arteries

An adenine/cytosine (A/C) base substitution at position 1166 in the angiotensin II type 1 receptor (AT(1)R) gene is associated with the incidence of essential hypertension and increased coronary artery vasoconstriction. However, it is still unknown whether this polymorphism is associated with a difference in angiotensin II responsiveness. Therefore, we assessed whether the AT(1)R polymorphism is associated with different responses to angiotensin II in isolated human arteries. Furthermore, we evaluated whether inhibition of the renin-angiotensin system modifies the effect of the AT(1)R polymorphism. One hundred twelve patients who were undergoing coronary artery bypass graft surgery were prospectively randomized to receive an ACE inhibitor or a placebo for 1 week before surgery. Excess segments of the internal mammary artery were exposed to angiotensin II (0.1 nmol/L to 1 micromol/L) and KCl (60 mmol/L) in organ bath experiments. Patients homozygous for the C allele (n=17) had significantly greater angiotensin II responses (percentage of this maximal KCl-induced response) than did patients genotyped with AA+AC (n=95, P<0.05). Although ACE inhibition increased the response to angiotensin II, the difference in the response to angiotensin II, between CC and AA+AC patients remained intact in ACE inhibitor-treated patients. These results indicate increased responses to angiotensin II in patients with the CC genotype. The mechanism is preserved during ACE inhibition, which in itself also increased the response to angiotensin II. This reveals that the A1166C polymorphism may be in linkage disequilibrium with a functional mutation that alters angiotensin II responsiveness, which may explain the described relation between this polymorphism and cardiovascular abnormalities.

Evaluation of three polymorphisms in the promoter region of the angiotensin II type I receptor gene

BACKGROUND

Angiotensin II induces vasoconstriction and growth via stimulation of the AT1 receptor. A genetic variant (+1166A/C) in the 3' untranslated region of this gene had been found to be associated with arterial hypertension, aortic stiffness and coronary artery disease.

OBJECTIVE

In order to evaluate further the potential implications of the genetic variability of the AT1 gene we explored three newly characterized single nucleotide polymorphisms (SNPs) in its promoter in a Caucasian population-based sample (n = 623). One of these (-2228G/A) is in complete linkage disequilibrium with six additional SNPs in the region such that, indirectly, potential functional implications of these sites were assessed as well. For comparison, we genotyped the previously described +1166A/C variant

RESULTS

The allele frequencies of the -2228G/A, -1424C/ G and -521 C/T SNPs were 0.82/0.18, 0.963/0.037 and 0.64/0.36, respectively. Statistical analysis by one-factor ANOVA revealed no significant relationship of any allele, genotype or haplotype with age, sex, body mass index, heart rate, systolic or diastolic blood pressure, hypertension, the intake of antihypertensive medication or left ventricular mass. Likewise, renin, angiotensinogen, angiotensin-converting enzyme, aldosterone or atrial natriuretic peptide levels were not found to be associated with any of these SNPs. Surprisingly, the -2228 A allele was found to be overrepresented in subjects with diabetes mellitus (n = 25, P = 0.006). However, this result could not be confirmed when additional individuals with diabetes mellitus (n = 45) were analysed. A weak linkage disequilibrium was observed between the -2228 A allele and the +1166 C allele (chi2 1 3.1; P = 0.010).

CONCLUSION

From the present data it is unlikely that any one of the nine newly characterized SNPs in the promoter region of AT1 gene is associated with arterial hypertension.