Significance of angiotensin I-converting enzyme and angiotensin II type 1 receptor gene polymorphisms as risk factors for coronary heart disease

Association between angiotensin II type-1 receptor A1166C polymorphism and the presence of angiographically-defined coronary artery disease in an Iranian population

Background: There are reported associations between a polymorphism of the angiotensin II type 1 receptor (AT1R/A1166C) gene and coronary artery disease (CAD), hypertension, and myocardial infarction in some populations. Objective: Investigate the association between A1166C polymorphism and CAD in an Iranian population. Methods: Four hundred and thirteen patients with suspected CAD were recruited. Based on coronary angiography, the patients were classified into CAD+ (n=315) and CAD- (n=98) groups defined as >50% and <50% stenosis of any major coronary artery, respectively. One hundred and thirty-five healthy subjects were also recruited as the control group. The AT1R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method. Results: A higher frequency of the AC and CC genotypes and lower frequency of the AA genotype was observed in both CAD+ and CAD- groups, compared with the control group (p <0.05). CAD+ and CAD- groups also had a higher frequency of the C allele than controls (p <0.01). There was no significant difference in genotype and allele frequencies between hypertensive and non-hypertensive patients (p > 0.05). In addition, the AT1R genotype frequencies did not differ significantly among different subgroups of CAD+ patients, based on the number of affected coronary vessels (p >0.05). Conclusion: The frequency AT1R/A1166C polymorphism was higher among patients with some degrees of coronary stenosis who are candidates of coronary angiography.

Sonographic evaluation of atherosclerosis burden in carotid arteries of ischemic stroke patients and its relation to paraoxonase 1 and 2, MTHFR and AT1R genetic variants

OBJECTIVE

Common variants of the Paraoxonase (PON), 5-Methyl-Tetrahydrofolate-Reductase (MTHFR) and Angiotensin-II receptor 1 (AT1R) genes have been associated with ischemic stroke (IS) risk. Moreover, carotid atherosclerosis is a common cause of IS. The aim of this study is to explore whether variants in these genes associate with the severity of ultrasonographic determined atherosclerosis assessed in carotid arteries.

PATIENTS AND METHODS

Etiologic subtype of cerebral ischemia was determined according to the TOAST classification. Genotypes were detected by PCR and restriction analysis. An ultrasonographic supra-aortic trunks study was performed to all patients to assess their atherosclerotic involvement based on predefined criteria.

RESULTS

In IS patients, none of the analyzed gene distributions differed concerning the stenosis degree. Nevertheless, a trend was observed for the rs662 and rs7493 variants of the PON1 and PON2 genes respectively. When evaluated the results based on different inheritance models, a significant contribution of rs7493 variant according to a dominant (OR=2.397, 95% CI (1.001-5.376); p=0.045) and log-additive inheritance forms (OR=1.85, 95% CI (1.07-3.2); p=0.03) was observed. Only rs7493 reached statistical significance (p=0.013), when genotype distribution was analyzed according to carotid intima-media thickness (cIMT) and remain significant in multivariate logistic regression analysis (OR=2.66, 95% CI (1.1 to 6.4); p=0.03).

CONCLUSION

In IS patients of the north area of the Gran Canaria island the PON2 (rs7493) gene variant associates with a worse ultrasonographic profile. Conversely, the Cys311Cys homozygosis of the rs7493 variant was also related to a better ultrasonographic profile in our study.

Gene Polymorphisms of Angiotensin II Type 1 Receptor and Angiotensin-Converting Enzyme in Two Ethnic Groups Living in Zhejiang Province, China

Polymorphisms of ACE insertion/deletion (I/D) and angiotensin II type 1 receptor (AT1R) 1166A-C have been associated with many diseases, and distributions of their genotypes vary in different races and populations. The aim of this study was to investigate distributions of angiotensin-converting enzyme (ACE) and AT1R genotypes in Han and She populations in ZheJiang province. We determined ACE and AT1R genotypes in 189 Han and 163 She individuals. DNA was extracted from peripheral blood samples. Analyses of ACE and AT 1R genotypes were performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The frequencies of ACE genotypes and alleles among the Han sample (41.3%II, 41.3%ID, 17.5%DD; 61.9%I allele, 38.1%D allele) were similar to those among She individuals (39.9%II, 39.3%ID, 20.9%DD; 59.5%I allele, 40.5%D allele), with p=0.660; p=0.421. However, significant differences in the distributions of ACE polymorphism between men and women among She population were observed, with p=0.042, p=0.014. AT1R genotype and allele frequencies in the Han population were (88.4%AA, 11.1%AC, 0.5%CC) and (93.9%A allele, 6.1%C) allele respectively. In the She population they were (78.0%AA, 21.3%AC, 0.6%CC) and (89.0%A allele, 11.0%C allele). The significant differences were found between Han and She populations with p=0.031, p=0.018, and within subgroups of women, with p=0.010, p=0.021. There were no significant differences within subgroups of men (p=0.476, p=0.261). The genotype distributions or allele frequencies of ACE and AT1R were significantly different between the samples of the She and Han populations.

Renin-angiotensin system gene polymorphisms and premature coronary heart disease

Introduction

Experimental and clinical studies demonstrated that the renin-angiotensin system (RAS) affects the pathogenesis of atherosclerosis and prognosis of coronary heart disease (CHD). The aim of this study was to investigate the genotype distribution and the allele frequencies of three RAS genes polymorphisms and their effects on premature CHD in a Turkish population.

Materials and methods

One-hundred and fifteen Turkish patients with premature CHD and 128 controls were included into the study. Angiotensin-converting enzyme (ACE), angiotensin II type 1 (AT1) receptor and angiotensinogen (AGT) gene polymorphisms were analysed by polymerase chain reaction (PCR ) and restriction fragment length polymorphism (RFLP).

Results

The patients group showed an increased frequency of the ACE D allele compared with controls (65% vs. 35%, p=0.0001). There was a significant association between the DD genotype and premature CHD (ACE DD vs. ID and II; odds ratio [OR]=2.82 [CI 95% 1.33—2.91, p=0.002]). Also, we observed increased premature CHD risk associated with higher frequencies of the AGT MM genotype in patients when compared with controls (AGT MM vs. TT and MT, OR=1.92 [CI 95% 1.11—3.33, p=0.018]). We found a significant association between AT1-receptor AA genotype and decreased risk of premature CHD (AT1R AA vs. AC and CC, OR= 0.57[CI 95% 0.34—0.95, p=0.03]).

Conclusions

We demonstrated that increased premature CHD risk is associated with higher frequencies of the ACE DD and AGT MM genotypes. These findings indicate a synergistic contribution of ACE DD and AGT MM polymorphisms to the development of premature CHD. Also, our results suggest that family history, smoking, diabetes, hypertension, obesity and ACE DD genotype were independent risk factors for premature CHD.

Genes of renin angiotensin system and coronary heart disease

Coronary constriction, proliferation of smooth muscle cells and arrhythmia are involved in the pathophysiology of coronary heart disease and its complications such as myocardial infarction and sudden death. All these effects are favoured by high angiotensin II levels. Angiotensin II is the main effector molecule of the renin angiotensin system and it acts through angiotensin II type receptors. Genetically determined differences in the expression of the components of this system could adversely affect angiotensin II concentration and subsequently heart. Consequently each component of this system represents a potential candidate in the etiology of cardiovascular disease. In this article we review the variation of the angiotensin I converting enzyme, angiotensin II type I receptor and angiotensinogen genes and their association with cardiovascular disease.

Renin-angiotensin system genes polymorphism in Egyptians with premature coronary artery disease

Genetics polymorphism of the renin-angiotensin system (RAS) affects the pathogenesis of atherosclerosis and associated with coronary artery disease (CAD). We aimed to investigate the association between the RAS genes and premature CAD (PCAD) in Egyptians. 116 patients with PCAD, 114 patients with late onset CAD and 119 controls were included in the study. Angiotensin converting enzyme (ACE), angiotensin II receptor type 1 (ATR1) and angiotensinogen (AGT) genes polymorphisms were analyzed by polymerase chain reaction (PCR). We found that ACE DD, AGT TT and ATR1 CC increased the risk of PCAD by 2.7, 2.8 and 2.86 respectively). Smoking, hypertension, diabetes, total cholesterol, triglycerides and LDL cholesterol were independent risk factors for the development of PCAD. We conclude that the ACE DD, AGT TT and ATR1 CC genotypes may increase the susceptibility of an individual to have PCAD. The coexistence of CAD risk factors with these risky RAS genotypes may lead to the development of PCAD in Egyptian patients.

Angiotensin converting enzyme gene polymorphism is associated with severity of coronary artery disease in men with high total cholesterol levels

This study examines whether renin-angiotensin-aldosterone system gene polymorphisms: ACE (encoding for angiotensin converting enzyme) c.2306-117_404 I/D, AGTR1 (encoding for angiotensin II type-1 receptor) c.1080*86A>C and CYP11B2 (encoding for aldosterone synthase) c.-344C>T are associated with the extension of coronary atherosclerosis in a group of 647 patients who underwent elective coronary angiography. The extension of CAD was evaluated using the Gensini score. The polymorphisms were determined by PCR and RFLP assays. The associations between genotypes and the extent of coronary atherosclerosis were tested by the Kruskal-Wallis test, followed by pairwise comparisons using Wilcoxon test. The population has been divided into groups defined by: sex, smoking habit, past myocardial infarction, BMI (>, ≤ 25), age (>, ≤ 55), diabetes mellitus, level of total cholesterol (>, ≤ 200 mg/dl), LDL cholesterol (>, ≤ 130 mg/dl), HDL cholesterol (>, ≤ 40 mg/dl), triglycerides (>, ≤ 150 mg/dl). Significant associations between the ACE c.2306-117_404 I/D polymorphism and the Gensini score in men with high total cholesterol levels (P(Kruskal-Wallis) = 0.008; P(adjusted) = 0.009), high level of LDL cholesterol (P(Kruskal-Wallis) = 0.016; P(adjusted) = 0.028) and low level of HDL cholesterol (P(Kruskal-Wallis) = 0.04; P(adjusted) = 0.055) have been found. No association between the AGTR1 c.1080*86A>C and CYP11B2 c.-344C>T and the Gensini score has been found. These results suggest that men who carry ACE c.2306-117_404 DD genotype and have high total cholesterol, high LDL cholesterol and low HDL cholesterol levels may be predisposed to the development of more severe CAD.

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.

Functional polymorphisms in genes of the Angiotensin and Serotonin systems and risk of hypertrophic cardiomyopathy: AT1R as a potential modifier

Background

Angiotensin and serotonin have been identified as inducers of cardiac hypertrophy. DNA polymorphisms at the genes encoding components of the angiotensin and serotonin systems have been associated with the risk of developing cardiovascular diseases, including left ventricular hypertrophy (LVH).

Methods

We genotyped five polymorphisms of the AGT, ACE, AT1R, 5-HT2A, and 5-HTT genes in 245 patients with Hypertrophic Cardiomyopathy (HCM; 205 without an identified sarcomeric gene mutation), in 145 patients with LVH secondary to hypertension, and 300 healthy controls.

Results

We found a significantly higher frequency of AT1R 1166 C carriers (CC+AC) among the HCM patients without sarcomeric mutations compared to controls (p = 0.015; OR = 1.56; 95%CI = 1.09-2.23). The AT1R 1166 C was also more frequent among patients who had at least one affected relative, compared to sporadic cases. This allele was also associated with higher left ventricular wall thickness in both, HCM patients with and without sarcomeric mutations.

Conclusions

The 1166 C AT1R allele could be a risk factor for cardiac hypertrophy in patients without sarcomeric mutations. Other variants at the AGT, ACE, 5-HT2A and 5-HTT did not contribute to the risk of cardiac hypertrophy.

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.

RAS gene polymorphisms, classical risk factors and the advent of coronary artery disease in the Portuguese population

Background

Several polymorphisms within the renin-angiotensin system cluster of genes have been associated with the advent of coronary artery disease (CAD) or related pathologies. We investigated the distribution of 5 of these polymorphisms in order to find any association with CAD development and distinguish if any of the biochemical and behavioural factors interact with genetic polymorphisms in the advent of the disease.

Methods

ACE I/D (rs4340), ACE A11860G (rs4343), AT1R A1166C (rs5186), AGT T174M (rs4762) and AGT M235T (rs699) gene polymorphisms were PCR-RFLP analysed in 298 CAD patients and 510 controls from Portugal. Several biochemical and behavioural markers were obtained.

Results

ACE I/D DD and ACE11860 GG genotypes are risk factors for CAD in this population. The simultaneous presence of ACE I/D I and ACE11860 A alleles corresponds to a significant trend towards a decrease in CAD incidence. We found several synergistic effects between the studied polymorphisms and classical risk factors such as hypertension, obesity, diabetes and dyslipidaemia: the presence of the DD genotype of ACE I/D (and also ACE11860 GG) increases the odds of developing CAD when associated to each one of these classical risk factors, particularly when considering the male and early onset CAD subgroup analysis; AGT235 TT also increases the CAD risk in the presence of hypertension and dyslipidaemia, and AT1R1166 interacts positively with hypertension, smoking and obesity.

Conclusion

ACE polymorphisms were shown to play a major role in individual susceptibility to develop CAD. There is also a clear interaction between RAS predisposing genes and some biochemical/environmental risk factors in CAD onset, demonstrating a significant enhancement of classical markers particularly by ACE I/D and ACE11860.

Renin-angiotensin system haplotypes and the risk of myocardial infarction and stroke in pharmacologically treated hypertensive patients

The products of the renin-angiotensin system (RAS) play an important role in the pathogenesis of cardiovascular disease. Studies examining RAS gene variants and cardiovascular disease have focused on single-nucleotide polymorphisms (SNPs) rather than haplotypes, which better characterize the patterns of genetic variation. The authors conducted a population-based, case-control study at Group Health (Seattle, Washington) between 1995 and 1999 to determine whether common haplotypes in the angiotensinogen gene (AGT), the renin gene, the angiotensin-converting enzyme gene, and the angiotensin II receptor type 1 and receptor type 2 genes were associated with the risk of myocardial infarction and stroke among pharmacologically treated hypertensive patients. SNP discovery was done using 23 European-origin samples. Thirty tagSNPs (the minimum sets of SNPs that capture most of the haplotype diversity within a block) were genotyped in cases and controls. Haplotypes were inferred using the program PHASE (http://www.stat.washington.edu/stephens/software.html). The authors used weighted logistic regression to estimate associations and conducted a permutation test to estimate the probability of a chance finding. AGT haplotype B was associated with the risk of myocardial infarction (odds ratio = 1.58, 95% confidence interval: 1.06, 2.35); however, results were not statistically significant given the number of tests performed (permutation p = 0.17). In this case-control study, RAS gene haplotypes were not significantly associated with increased risks of myocardial infarction or stroke.

ACE-DD genotype is associated with the occurrence of acute coronary syndrome in postmenopausal women

The insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE), the A1166C polymorphism in the angiotensin type 1 receptor (AT1R), and the M235T polymorphism of the angiotensinogen gene are associated with cardiovascular disease mostly in men. Few data are available on the effects of these genetic variations in postmenopausal women according to hormone replacement therapy (HRT) use. In this case-control study, we determine the frequency of mutant alleles in the ACE I/D, M235T and A1166C polymorphisms in postmenopausal Caucasian women with and without a diagnosis of acute coronary syndrome (ACS). Data from 198 women with ACS (63+/-10 years) and 149 controls (62+/-7 years) showed that ACE-DD genotype was more prevalent in women with ACS compared to controls (30% vs. 19%, P<0.05). There was no difference in genotype distributions for either the M235T or the A1166C polymorphisms between groups. The difference in ACE genotype distribution between ACS women and controls was driven by current HRT users with 30% of ACS and 15% of controls carrying the ACE-DD genotype (P<0.05). The oligenic combination of ACE-DD and M235T-TT genotypes was higher in ACS compared to controls. Among carriers of M235T-TT, 7% of ACS and 1% of controls also had the ACE-DD genotype, P<0.05. Thus, the ACE-DD genotype may be associated with ACS in postmenopausal women, particularly in HRT users.

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.

Blood pressure response to strength training may be influenced by angiotensinogen A-20C and angiotensin II type I receptor A1166C genotypes in older men and women

OBJECTIVES

To determine the influence of angiotensinogen (AGT) A-20C, M235 T, and angiotensin II type 1 receptor (AGTR1) A1166C genotypes on resting blood pressure (BP) response to strength training (ST) in older men and women.

DESIGN

Prospective intervention study with retrospective genotyping.

SETTING

University of Maryland Exercise Physiology Laboratory.

PARTICIPANTS

Seventy sedentary, healthy older men (n=34) and women (n=36).

INTERVENTION

Approximately 23 weeks of ST performed 3 days per week.

MEASUREMENTS

Resting BP was measured on six separate occasions before and after ST for each subject. AGT and AGTR1 genotyping was performed retrospectively from each subject's genomic deoxyribonucleic acid.

RESULTS

Systolic BP decreased in C-allele carriers at the AGT A-20C locus with ST (122+/-1 to 116+/-2 mmHg, P<.05), which was significantly greater than the decrease in the A homozygotes (126+/-1 to 123+/-1 mmHg, P<.05). At the AGTR1 A1166C locus, diastolic BP decreased to a greater extent in the C-allele carriers (76+/-1 to 70+/-2 mmHg, P<.05) than in the A homozygotes (75+/-1 to 72+/-1 mmHg, P<.05).

CONCLUSION

The AGT A-20C and AGTR1 A1166C genotypes may influence resting BP response to ST, such that C-allele carriers at each of these loci reduce their resting BP in response to ST to a greater extent than A homozygotes.

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.

Genotypic interactions of renin-angiotensin system genes in myocardial infarction

BACKGROUND

Three-gene interactions among the genetic polymorphisms of the renin-angiotensin system (RAS) associated with acute myocardial infarction (AMI) have not been examined in a single population. We hypothesized that all types of gene-to-gene associations may occur in AMI, but that some will have a higher risk, depending on the gene frequencies.

METHODS

Polymorphisms of the AGT (M235T), ACE (I/D) and AGTR1 (A1166C) genes in AMI patients and controls were analyzed using the polymerase chain reaction. Classic coronary risk factors were analyzed in all individuals.

RESULTS

Logistic regression analysis of these factors and the genetic polymorphisms demonstrated that smoking, family history of CAD, arterial hypertension and total cholesterol were the most significant contributors to AMI. The genotypic frequencies for all three genes alone were similar between the infarction and control groups, with no increased risk of developing AMI. Double homozygous combinations for normal alleles (MM of AGT, II of ACE and AA of AGTR1) had a lower risk of AMI (odds ratio<0.38), indicating a protective effect in these individuals. In genotypic combinations that included at least one unfavorable allele, the risk (odds ratio) of developing AMI was 2.92, 2.63 and 2.68 for AGT vs. ACE, AGT vs. ATR1 and ACE vs. AGTR1, respectively. The positive interaction among the three genes and the risk of AMI had an odds ratio of 3.78 with a 95% CI of 0.88-12.85.

CONCLUSIONS

The risk of developing AMI is higher whenever there are unfavorable alleles in gene-to-gene associations in the RAS.

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.

Genetic variants of angiotensin II receptors and cardiovascular risk in hypertension

Renin-angiotensin systems may mediate cardiovascular disease pathogenesis through a balance of actions of angiotensin II on (potentially proatherogenic) constitutive type 1 (AT1R) and (potentially antiatherogenic) inducible type 2 (AT2R) receptors. We explored such potential roles in a prospective candidate gene association study. Cardiovascular end points (fatal, nonfatal, and silent myocardial infarction and coronary artery bypass surgery/angioplasty) were documented among 2579 healthy UK men (mean age, 56.1+/-3.5 years; median follow-up, 10.1 years) genotyped for the AT1R1166A>C and the X chromosome located AT2R1675A>G and 3123C>A polymorphisms. Baseline characteristics, including blood pressure, were independent of genotype. The AT1R1166CC genotype was associated with relative cardiovascular risk (hazard ratio, 1.65 [1.05 to 2.59]; P=0.03) independent of blood pressure. Systolic blood pressure was associated with risk (P=0.0005), but this association was restricted to AT2R1675A allele carriers (P<0.00001), with G allele carriers protected from the risk associated with blood pressure (P=0.18). Hypertensive carriers with the AT2R1675A/3123A haplotype were at most risk, with 37.5% having an event. This is the first study to demonstrate an association of AT2R genotype with coronary risk, an effect that was confined to hypertensive subjects and supports the concept that the inducible AT2R is protective. Conversely, the AT1R1166CC genotype was associated with cardiovascular risk irrespective of blood pressure. These data are important to our understanding of the divergent role of angiotensin II acting at its receptor subtypes and coronary disease pathogenesis and for the development of future cardiovascular therapies.

Overestimation of genetic risks owing to small sample sizes in cardiovascular studies

We sought evidence of publication bias to explain conflicting findings in studies of angiotensin-converting enzyme deletion polymorphism (ACE D) and glycoprotein IIIa PlA2 (PLA2) polymorphism and the risk of myocardial infarction. Factor 5 Leiden (F5L), a well-established thrombotic risk factor, served as an internal comparison. We conducted systematic reviews of published studies involving ACE D, PLA2, F5L and relevant outcomes, searching medline (January 1990 through February, 2001), bibliographies, and meta-analyses. Random effects pooled odds ratios (95% confidence interval) for cardiovascular outcomes were as follows: PLA2 (n = 13,167 subjects): 1.13 (1.02, 1.26); ACE D (n = 42,140 subjects): 1.22 (1.11, 1.35); and F5L (n = 27,277 subjects): 4.43 (3.65, 5.38). However, funnel plots of ACE D and PLA2, but not F5L, showed an inverse relationship between sample size and odds ratios for ACE D (p = 0.02) and PLA2 (p = 0.04) but not F5L (p = 0.65) by Egger's test for potential publication bias. Despite research-based genotyping of over 50,000 subjects, the overall risk for myocardial infarction as a result of PLA2 and ACE D remains doubtful. Our study provides a clear example of how publication of underpowered studies can spuriously implicate polymorphisms as genetic risk factors.

Polymorphisms in the RAS and cardiac function

Since the discovery of the polymorphism in the angiotensin converting enzyme (ACE) and the consequences of this polymorphism on the activity levels of the enzyme, numerous association studies have been performed. However, these investigations do not often adhere to the most stringent criteria for such studies. The initial study reporting a positive association of the ACE polymorphism and myocardial infarction showed an increased risk of the DD genotype. This initial association was eventually refuted by a large, well conducted association study, which found a risk ratio of 1.02 after combining their own data with all published data. Although such large, well conducted association studies have not been performed in left ventricular (LV) hypertrophy, the association between DD genotype and hypertrophy is more convincing with a 192% excess risk of LV hypertrophy in untreated hypertensives. The role of ACE genotype in LV growth is well established, especially in athletes. In heart failure, large studies or meta-analyses have not been performed, because most studies have selected different end-points. This hampers a proper meta-analysis of the results obtained in associations with heart failure. As most association studies do not fulfill the criteria for good association studies and use too small sample sizes, it remains important to perform a meta-analysis to add meaning to the results of such studies. Above all, it is important to obey the rules set for association studies, large sample size, small P values, report associations that make biological sense and alleles that affect the gene product in a physiologically meaningful way.

Renin-angiotensin-aldosterone system loci and multilocus interactions in young-onset essential hypertension

OBJECTIVE

Renin-angiotensin-aldosterone system component genes have been associated to essential hypertension. Thus, we studied the association of singe locus or multilocus interactions with young-onset essential hypertension.

SETTING AND DESIGN

This is a case-control study based on a population sample of adolescent at an inner city.

PARTICIPANTS

We studied 54 adolescents with hypertension and 121 age-matched normotensives, recruited from a high-school student population of 934 interviewed individuals.

METHODS

Resting blood pressure was measured on three different days and normalized (Z-score) by sex and age. Genotypes of ACE (I/D) angiotensinogen (T174M and M235T), ATIR (A1166C), and CYP11B2 (C-344T) were determined by PCR/RFLP or ASO.

RESULTS

Although genotype frequencies were not different in both groups, we found a significant dominant effect of ACE D and angiotensinogen 235T alleles on normalized systolic arterial blood pressure in males. This effect was confirmed by sib-pair linkage analysis taking normalized blood pressure as a quantitative trait. We independently analyzed multilocus interactions in normotensive and hypertensive adolescents searching for multiple locus deviation from Hardy-Weinberg or linkage equilibrium. We found that from 63 multilocus combinations, 4 deviated significantly from equilibrium in hypertensive adolescents but none in the normotensives. Deviations from equilibrium may indicate that the combination of alleles at different loci affects susceptibility or resistance to the disease.

CONCLUSION

In addition to the angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) gene variants, gene-gene interactions may be important causative factors in a complex disease such as young-onset essential hypertension.

Progression of atherosclerosis in patients with peripheral arterial disease as a function of angiotensin-converting enzyme gene insertion/deletion polymorphism

Angiotensin-converting enzyme insertion/deletion (I/D) gene polymorphism plays a role in determining the inter-individual variability of circulating angiotensin-converting enzyme activity and intracellular angiotensin-converting enzyme levels. Angiotensin-converting enzyme, as a key enzyme in the renin-angiotensin system, catalyzes the activation of the vasoconstricting and proliferation-stimulating angiotensin II and breaks down the vasodilatory peptide bradykinin. It is assumed that the excess supply of angiotensin II (due to the deletion polymorphism of the angiotensin-converting enzyme gene) contributes to endothelial dysfunction and in this way promotes the onset and progression of atherosclerosis. The aim of this study was to test whether the presence of the deletion allele of the angiotensin-converting enzyme gene predisposes a more rapid systemic progression of a preexisting peripheral arterial disease. To this end, the course of disease was surveyed for an average of 5 years in 97 patients who were angiotensin-converting enzyme gene-typed and suffered from a stable stage II peripheral arterial disease according to Fontaine. These patients did not suffer from an additional coronary artery disease, a cerebrovascular disease, or other serious illness. A local progression in the periphery or a systemic progression in the coronary or cerebrovascular areas was regarded as study endpoints. Of the patients, 49.5% showed an atherosclerosis progression during the surveillance period. With II-carriers, a progression was registered in 42.1% and with DD carriers, progression was seen in 59.4%. D/I allele frequencies were seen in patients with progression at a level of 0.60/0.40 vs 0.55/0.45 for patients without progression. The average duration of disease in stable stage II (before progression appeared) amounted to 108 +/- 14 months for II carriers, 88 +/- 8 months for ID carriers, and 92 +/- 11 months for DD carriers (p = 0.21). Based on these findings, the deletion polymorphism of the angiotensin-converting enzyme gene is not an independent risk factor for progression of atherosclerosis in patients with peripheral arterial disease.

Polymorphisms of genes encoding components of the sympathetic nervous system but not the renin-angiotensin system as risk factors for orthostatic hypotension

OBJECTIVE

The genetic background of orthostatic hypotension, an important risk factor for future cardiovascular morbidity and mortality, was investigated.

DESIGN AND METHODS

The study subjects comprised 415 community-dwelling individuals, who were free from any cardiovascular complications, aged 50 years or older (mean age 70.5 +/- 9 years). Basal systolic blood pressure (SBP) was measured twice in supine posture after resting for more than 10 min. The orthostatic change in SBP was determined at 1 min and 3 min after standing up. The maximum change in SBP after standing was determined. Orthostatic hypotension was defined as a decline in SBP greater than 20 mmHg. The polymorphisms of genes encoding components of the renin-angiotensin system and sympathetic nervous system, which play pivotal roles in postural change in blood pressure regulation, were determined.

RESULTS

There were no significant associations between the maximum change in SBP, the prevalence of orthostatic hypotension and gene polymorphisms of angiotensin-converting enzyme I/D, angiotensinogen M235T and angiotensin II type 1 receptor A1166C. On the contrary, polymorphism of the Gs protein alpha-subunit (GNAS1) T131C was significantly associated with the maximum change in SBP after standing [1.9 +/- 16 versus -3.6 +/- 16 mmHg (TT + TC versus CC), P = 0.008]. The prevalence of orthostatic hypotension was significantly different among GNAS1 genotypes (chi squared = 10.12, P = 0.011) and G-protein beta 3 subunit (GNB3) genotypes (chi squared = 6.12, P = 0.020). Multiple logistic regression analysis showed that both GNAS1 CC genotype [odds ratio (OR) = 2.79, 95% confidence interval (CI) 1.35-5.79, P = 0.006] and GNB3 C allele (OR = 1.78, 95% CI 1.06-3.00, P = 0.030) were independent risks for orthostatic hypotension.

CONCLUSIONS

These findings indicate that genes encoding sympathetic nervous components could be involved in the predisposition for orthostatic hypotension.

[The involvement of the renin-angiotensin system gene polymorphisms in coronary heart disease]

INTRODUCTION AND OBJECTIVES

Previous studies angiotensin-converting enzyme gene insertion/deletion polymorphism ACE (I/D), angiotensinogen gene polymorphism, and angiotensin II AT1 receptor polymorphism in relation to coronary heart disease controversial results. This study was designed to analyze the association between these gene polymorphisms and the first coronary event in individuals residing on Grand Canary Island, Spain.

PATIENTS AND METHOD

Case-control study. Case subjects (n = 304) were recruited at the first coronary event; age-matched controls (n = 315) were randomly selected from the Grand Canary population. Participants were examined for the usual risk factors. Blood samples were obtained for biochemical analyses and DNA extraction. Genotyping was performed by PCR and restriction analysis.

RESULTS

Neither ACE (I/D) nor AT1 receptor polymorphism was associated with coronary heart disease, whereas the frequency distribution of AGT M235T genotypes among patients and control subjects (TT: 29% and 19%; MT: 48% and 50%; MM: 22% and 31%, respectively) was statistically different (p = 0.003). Multiple logistic regression analysis identified the TT genotype of the angiotensinogen gene (OR = 1.9; 95% CI 1.1-3.4), diabetes (OR = 4.4; 95% CI 2.0-9.4) and hypertension (OR = 2.1; 95% CI 1.3-3.3) as risk factors predicting the coronary event.

CONCLUSIONS

Our results provide no evidence of an association between ACE (I/D) or AT1 receptor polymorphism and coronary heart disease. However, homozygosity for the T allele of the angiotensinogen gene, diabetes and hypertension independently place individuals at higher risk of experiencing a coronary event on Grand Canary Island.

Influence of angiotensinogen M253T gene polymorphism and an angiotensin converting enzyme inhibitor on restenosis after percutaneous coronary intervention

We studied the relation between renin-angiotensin system (RAS) related gene polymorphisms, such as angiotensin converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M253T and angiotensin II type 1 receptor (AT1R) A1166C, and the effect of quinapril, an ACE inhibitor with high tissue-binding affinity, on preventing restenosis after percutaneous coronary intervention (PCI). A total of 253 patients successfully treated for coronary artery disease were randomly assigned to quinapril or control. Of the 215 patients who completed the follow-up, we determined gene polymorphisms in 204 patients with 241 lesions who provided blood samples for genotype determination. In the control, the ACE D homozygotes showed a smaller minimal lumen diameter (MLD) at follow-up (P=0.063). The other two genotypes of AGT and AT1R did not affect restenosis after PCI. According to quinapril treatment, the AGT T homozygotes significantly showed a beneficial effect of quinapril on MLD (P=0.013) and late lumen loss (P=0.013). The ACE I homozygotes also exhibited beneficial effects of quinapril on larger MLD (P=0.065). The AT1R genotype did not influence the quinapril effect. In conclusion, the AGT T homozygotes might benefit from effects of quinapril on preventing restenosis after PCI.

Genotype-specific association between circulating soluble cellular adhesion molecules and carotid intima-media thickness in community residents: J-SHIPP study. Shimanami Health Promoting Program

Plasma levels of soluble forms of cellular adhesion molecules (CAMs) and their relationships with carotid intima-media thickness (IMT) were investigated in community residents. Plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured by ELISA in 200 community residents in Japan. Carotid IMT showed a weak but significant positive correlation with the plasma levels of both sICAM-1 (r=0.175, p=0.013) and sVCAM-1 (r=0.19, p=0.0075). Gene polymorphisms of angiotensin converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M235T, angiotensin II type 1 receptor (AT1R) A1166C and apolipoprotein E (apoE) were determined for each subject. The plasma level of sVCAM-1 tended to be lower in subjects with the ACE DD genotype than in those with the ACE ID and II genotypes (373+/-94, 421+/-133, 443+/-135 ng/ml, respectively, p=0.056). However, there were no genotype-specific differences in the plasma levels of soluble forms of CAMs for the other genes examined. In a separate analysis, the plasma level of sICAM-1 was significantly associated with carotid IMT in ACE D carriers (ID + DD) (r=0.28, p=0.002), AGT M carriers (MT + MM) (r=0.32, p=0.0045), and subjects with apoE4 (r=0.35, p=0.036). In contrast, the plasma level of sVCAM-1 showed significant positive correlations with carotid IMT in subjects with the ACE II genotype (r=0.33, p=0.0027) or AGT TT genotype (r= 0.22, p=0.015), and subjects with apoE E2/E3 or E3/E3 (r=0.16, p=0.043). Stepwise regression analysis showed that plasma sVCAM-1 was independently associated with carotid IMT in subjects with the ACE II genotype or apoE4 genotype. Similarly, the plasma level of sICAM-1 was independently associated with carotid IMT in AGT M carriers. These findings suggest that genetic background could be involved in the association between plasma CAMs and atherosclerosis.

Angiotensin II receptor polymorphisms in hypertension. Pharmacogenomic considerations

Molecular variants of individual components of the renin-angiotensin system (RAS) are thought to contribute to inherited predisposition towards essential hypertension. Polymorphisms in genes of angiotensinogen (AGT), angiotensin I-converting enzyme (ACE) and angiotensin II type 1 receptor (AT-1) have been related to differential responses to antihypertensive drugs. AT-1 receptor mediates the major pressor and trophic actions of angiotensin II (Ang II). At least 14 AT-1 polymorphisms have been described in the gene (AGT1R); in particular the +1166 A/C polymorphism has been associated with the severe form of essential hypertension. A relationship was suggested between this polymorphism and the humoral and renal hemodynamic responses to losartan, an antihypertensive drug acting as an AT-1 blocker. Variability in the individual response to AT-1 antagonists could also be due to variations in the pharmacokinetics of the drugs. This review presents current knowledge on Ang II-receptors and polymorphisms in AGT1R related to cardiovascular disease and antihypertensive therapy.

The associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein

We sought to determine the associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein (HDL) in a case-control study. The function of HDL can be assessed by the fractional esterification rate of cholesterol in low density lipoprotein (LDL)- and very low density lipoprotein (VLDL)-depleted plasma (FER(HDL)), which reflects a balance of cholesterol uptake by HDL and cholesterol ester (CE) transport in the reverse cholesterol transport (RCT) system in humans. Cases (n=51, age: 64.3+/-8.0 years) and controls (n=51, age: 58.7+/-13.1 years) were defined as subjects with/without angiographically proven coronary artery disease (CAD), respectively and examined for thoracic aortic atherosclerosis (TAA) by transesophageal echocardiography. The severity of TAA was determined by the ratio of average sclerotic areas (ASA) and average sclerotic lengths (ASL). The cases had significantly (P<0.05) higher values of ASA (0.22+/-0.18 vs. 0.10+/-0.11), ASL (0.82+/-0.56 vs. 0.48+/-0.45), ASA/ASL ratio (0.23+/-0.08 vs. 0.17+/-0.09) and FER(HDL) (10.3+/-3.8 vs. 8.3+/-3.5% per hour) and lower HDL-C and apolipoprotein A-I levels than the controls. A receiver operating characteristic (ROC) curve analysis showed that ASA/ASL and FER(HDL) had moderate discriminating ability for CAD and the diagnostic accuracy of ASA/ASL was better than that of FER(HDL) (area under ROC curve: 0.703 and 0.656, respectively). Multivariate logistic regression analysis indicated that ASA/ASL and FER(HDL) were independent indicators for CAD [odds ratio (95% CI): 7.5 (2.4-27), P<0.01 and 4.0 (1.2-15), P<0.05] after adjusting for age, gender and other conventional risk factors, and that a high FER(HDL) value greatly increased the relative risk of CAD associated with a high ASA/ASL. The function of HDL, as assessed by FER(HDL), enhances the ability of TAA to predict CAD.

Association of angiotensinogen M235T and A(-6)G gene polymorphisms with coronary heart disease with independence of essential hypertension: the PROCAGENE study. Prospective Cardiac Gene

OBJECTIVES

We examined the relationship between the angiotensinogen (AGT) gene M235T polymorphism, the variant promoter of the AGT gene A(-6)G and the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and coronary heart disease (CHD) in native Gran Canaria Island habitants, who have the highest rates of CHD in Spain.

BACKGROUND

Some studies subject that the ACE (I/D) polymorphism could be associated with CHD, while AGT (M235T) has been related to essential hypertension.

METHODS

We studied 304 subjects with angiographic evidence of coronary artery disease and a clinical diagnosis of myocardial infarction or unstable angina and 315 age- and gender-matched controls. Blood was drawn and DNA extracted. Angiotensin-converting enzyme (I/D) gene polymorphism was analyzed by polymerase chain reaction (PCR) and AGT gene polymorphisms by restriction fragment length polymorphism-PCR and mutagenically-separated PCR.

RESULTS

The ACE (I/D) polymorphism showed no association with CHD, whereas the frequency distribution of AGT (M235T) genotypes among patients and controls (235T: 29.1% and 19.0%; M235T: 48.5% and 50.2%; M235: 22.4% and 30.8%, respectively) was statistically different (p = 0.005) and not related to the presence of essential hypertension. Similar results were observed with the AGT A(-6)G polymorphism. In multiple logistic regression analysis, CHD odds ratio associated with 235T and M235 homozygotes were 1.7 (1.1 to 2.6) and 0.54 (0.36 to 0.82), respectively.

CONCLUSIONS

This study shows that genetic variation of the AGT (M235T), but not the ACE (I/D), genotypes contributes to the presence of CHD independently of blood pressure profile in a subset of the Spanish population with a high prevalence of cardiovascular disease.

Influence of angiotensin II type 1 receptor polymorphism on hypertension in patients with hypercholesterolemia

Essential hypertension results from the combined influence of environmental and genetic factors. The relationship between angiotensin II type 1 receptor (AT(1)) A-C(1166) polymorphism and essential hypertension is controversial. Because it is accepted that high concentration of serum cholesterol is one of risk factors of atherosclerosis, we investigated the influence of the AT(1) A-C(1166) polymorphism on hypertension in patients with hypercholesterolemia. A total of 131 hypertensive, 97 borderline, and 175 normotensive subjects were enrolled in this study. We selected hypercholesterolemic subjects on the condition that their serum concentration of total cholesterol was >220 mg/dl, and obtained 55 hypertensive, 24 borderline, and 52 normotensive subjects with hypercholesterolemia. There were no significant differences in the genotype nor allele frequency between hypertensive and normotensive subjects in the overall population. However, the presence of the C allele of the AT(1) gene has a tendency to increase the value of systolic blood pressure not only in subjects with hypercholesterolemia but also in the overall population. Furthermore, we found a significant relationship between the AT(1) polymorphism and hypertension in subjects with hypercholesterolemia; i.e., the frequency of the C allele of the AT(1) gene was significantly higher in hypertensives than in normotensives (P<0.005). These results suggested that high concentration of total cholesterol was an important risk factor to the occurrence of essential hypertension for patients who carried the C allele of the AT(1) gene.

Analysis of the postulated interaction between the angiotensin II sub-type 1 receptor gene A1166C polymorphism and the insertion/deletion polymorphism of the angiotensin converting enzyme gene on risk of myocardial infarction

A synergistic interaction between the insertion/deletion (I/D) polymorphism within the angiotensin-converting enzyme (ACE) gene and an A/C transversion at nucleotide position 1166 within the angiotensin II sub-type 1 receptor (AT1R) gene on risk of myocardial infarction has been reported. The risk associated with the ACE DD genotype increased with the number of AT1R C alleles present. To investigate this further, ACE I/D and AT1R A1166C genotypes were determined in 541 cases recruited at the time of infarction and 507 population-based controls. There was no difference in either the genotype distribution or allele frequencies between cases and controls for either the ACE polymorphism (P=0.48 and 0.35 respectively) or the AT1R polymorphism (P=0.35 and 0.21 respectively). Odds ratios for risk of MI associated with the ACE DD and AT1R CC genotypes were 1.09 (95% CI, 0.82-1.45) and 1.06 (0.67-1.68) respectively. 3.1% of cases versus 3.6% of controls were homozygous for both the D and C alleles (P=0.71). There was no increase in risk associated with the DD genotype in the presence of either one or two AT1R C alleles in the whole cohorts (OR 0.99, 95% CI 0.65-1.51 and 0.76, 95% CI 0.30-1.88, respectively) nor in sub-groups defined by specific risk factors. In conclusion, no evidence was found to support any interaction between the ACE gene I/D polymorphism and the ATIR gene A1166C transversion in determining the risk of myocardial infarction in the population studied.

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.

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.

A1166C polymorphism of the angiotensin II type 1 receptor gene and risk of adverse events after coronary catheter interventions

BACKGROUND

Contradictory reports exist concerning the role of the angiotensin II type 1 receptor A1166C polymorphism as a coronary risk factor. Moreover, it is unknown whether the A1166C polymorphism is associated with thrombotic complications after coronary catheter interventions.

METHODS

We investigated the role of the A1166C polymorphism as a risk factor in 1000 patients with coronary artery disease (CAD) and in 1000 age- and sex-matched controls. A total of 649 patients receiving interventions (270 coronary angioplasty, 102 atherectomy, and 277 stenting) were investigated for a 30-day composite end point including target vessel revascularization, myocardial infarction, or death.

RESULTS

The composite end point was reached by 42 patients (6.5%) without evidence that the C allele was associated with excess procedural risk (odds ratio 0.93; 95% confidence interval 0.79-1.75; P =.82). Further analyses by device failed to show linkage with adverse events complicating coronary angioplasty, atherectomy, and stenting. Moreover, in the entire CAD group (n = 1000), the polymorphism even showed a trend to underrepresentation (odds ratio 0.83; 95% confidence interval 0.69-1. 004, P =.054).

CONCLUSIONS

These results indicate that the A1166C polymorphism neither represents a risk factor for adverse events complicating coronary interventions nor seems to have significant impact on further long-term processes such as development and severity of CAD.

Genetic polymorphisms of the renin-angiotensin system and complications of insulin-dependent diabetes mellitus

OBJECTIVE

Patients with insulin-dependent diabetes mellitus (IDDM) have a high risk of developing diabetic nephropathy, retinopathy and cardiovascular diseases. The contribution of gene polymorphisms of the renin angiotensin system to these complications is controversial and may differ among populations.

METHODS

In 257 Dutch IDDM patients (188 with urinary albumin excretion (UAE) <30 mg/24 h), logistic regression analysis was used to study the relationships among, on the one hand, the insertion/deletion gene polymorphism of the angiotensin-converting enzyme gene (ACE-ID), the M235T gene polymorphism of the angiotensinogen gene (AGT-M235T), and the A1166C gene polymorphism of the angiotensin type 1 receptor gene (AT1-A1166C), and, on the other hand, UAE, retinopathy, hypertension, and coronary heart disease.

RESULTS

The T-allele of the AGT-M235T polymorphism was associated with an increased risk of an elevated UAE (odds ratio (OR) 3.03; 95% confidence interval (CI) 1.06-8.61), but only when interaction with the D-allele of the ACE-ID polymorphism was considered. A previously described positive interaction between the T-allele of the AGT-M235T polymorphism and the D-allele of the ACE-ID polymorphism could not be confirmed. The T-allele was also associated with an increased risk of retinopathy (OR 3.89, 95% CI 1.79-8.47). The CC-genotype of the AT1-A1166C polymorphism was associated with hypertension (OR 3.58; 95% CI 1. 23-10.37).

CONCLUSIONS

In a Dutch IDDM population, including 69 patients with (incipient) diabetic nephropathy, the T-allele of the AGT-M235T polymorphism is associated with an elevated UAE and diabetic retinopathy and the CC-genotype of the AT1-A1166C polymorphism is associated with hypertension. A previously described interaction between the AGT-M235T and the ACE-ID polymorphisms could not be confirmed. Since the number of nephropathic patients in this study is small, these conclusions must be interpreted with caution.

Large-scale test of hypothesised associations between the angiotensin-converting-enzyme insertion/deletion polymorphism and myocardial infarction in about 5000 cases and 6000 controls. International Studies of Infarct Survival (ISIS) Collaborators

BACKGROUND

The original report of a possible association between myocardial infarction and the insertion/deletion (I/D) polymorphism of the gene for the angiotensin-1-converting enzyme (ACE) indicated a risk ratio for myocardial infarction with the DD genotype of 1.34 (95% CI 1.05-1.70), and the association was claimed to be particularly strong in a retrospectively defined low-risk subgroup (3.2 [95% CI 1.7-5.9). Subsequent investigations reached varying conclusions, but all were small, and much larger studies were needed.

METHODS

4629 myocardial infarction cases and 5934 controls were compared. Cases were UK men aged 30-54 years and women aged 30-64 years recruited on presentation to hospital with confirmed myocardial infarction. Controls were aged 30-64 years with no history of cardiovascular disease, but were siblings or children of myocardial infarction survivors, or spouses of such relatives. All risk-ratio calculations allow for this relatedness of some of the controls. An updated meta-analysis of previous studies was also conducted.

FINDINGS

The ACE DD genotype was found in 1359 (29.4%) of the myocardial infarction cases and in 1637 (27.6%) of the controls (risk ratio 1.10 [95% CI 1.00-1.21]). The association between myocardial infarction and the DD genotype did not seem to be stronger in the subgroup defined as low risk by previously used criteria (234 [28%] of 836 cases and 911 [28%] of 3253 controls: risk ratio 1.04 [95% CI 0.87-1.24]), or in any other subgroup. Nor was the ACE I/D genotype predictive of subsequent survival.

INTERPRETATION

This study involved many more cases than any previously reported study of this question, but did not confirm the existence of any substantial association. In an updated meta-analysis of these results with those of previously published studies, the risk ratio for myocardial infarction with the DD genotype seems to lie in the range 1.0 to about 1.1. Although an increase in risk of up to about 10-15% cannot be ruled out, substantially more extreme risks can be. Moreover, there are not especially strong associations in the subgroups previously selected for emphasis. These findings illustrate the need for some studies of candidate genes to involve much larger populations than is customary, without undue emphasis on retrospectively defined subgroups.

Genetic risk factors and restenosis after percutaneous coronary interventions

Restenosis is the major limitation of percutaneous coronary interventions. Depending on the form of intervention and patients' characteristics, 20 to 50% of the treated patients incur significant restenosis. Restenosis is caused by a complex and only partially understood cascade of events. Thrombus formation at the injury site, formation of the neointima as a result of the migration and proliferation of smooth muscle cells (SMC) and extracellular matrix production, as well as constrictive remodeling of the vessel wall contribute by a variable degree to restenosis. Restenosis is not a random event but it affects selectively a certain subset of patients. These patients have some peculiar characteristics that help to identify the presence of a higher risk for restenosis. Conventional patient-related factors account only for a relatively small portion of the predictive power, much more contribution comes from lesion and procedural characteristics. There is increasing evidence that inherited factors may explain at least part of the excessive risk for restenosis observed in certain patients. Evidence exists that gene polymorphisms may lead to quantitative or functional alterations of the respective gene products. Recent studies have also found significant associations between several polymorphic alleles encoding for proteins with a relevant role in the process of lumen renarrowing and restenosis after percutaneous coronary interventions. The best studied polymorphisms in this regard are those of the genes encoding for angiotensin-converting enzyme and platelet glycoprotein-IIIa. Completed or ongoing studies have focused on polymorphisms of genes encoding for proteins interfering with lipid metabolism, hemostasis, nitric oxide production, inflammatory mechanisms, SMC proliferation and matrix production. The results of this research will have considerable pathophysiological and therapeutical implications for the battle against restenosis.

Genetic polymorphism of the renin-angiotensin system and organ damage in essential hypertension

BACKGROUND

The renin-angiotensin-aldosterone system (RAAS) plays a significant role in the development of hypertensive cardiac and vascular remodeling. Recently, several genetic variants of its key components, which may be clinically relevant and thus prove to be useful in the evaluation of cardiovascular risk, have been described. We therefore investigated the association between ACE I/D, AGT M235T, and AT1 A1266C gene polymorphisms and early signs of target organ damage in 215 untreated patients with essential hypertension (EH).

METHODS

Genotyping was based on the polymerase chain reaction technique, with further restriction analysis when required. Albuminuria was measured as the albumin-to-creatinine ratio (ACR). The left ventricular mass index (LVMI) was assessed by echocardiography (LVH = LVMI > or = 125 g/m2), carotid wall thickness (IMT) by an ultrasonographic (US) scan, and retinal vascular changes by direct ophthalmoscopy (Keith-Wagener classification).

RESULTS

The prevalence of microalbuminuria (Mi), LVH, and retinal vascular changes was 14, 46, and 74%, respectively. ACE, AGT, and AT1 genotype distribution was in agreement with the Hardy-Weinberg equilibrium. There was no difference in age, duration of disease, body mass index (BMI), blood pressure, and lipid profile when data were analyzed on the basis of genotype. Serum levels of angiotensin-converting enzyme (ACE) were related to the ACE genotype (10.2 +/- 0.5, DD; 8.2 +/- 0.3, ID; 6.5 +/- 0.4 IU/mL, II; P < 0. 0001 by analysis of variance). The ACE genotype independently influences serum ACE levels and accounts for approximately 14% of its variations (F = 26.7, r2 = 0.1393, df 1 to 214, P < 0.0001). Patients with DD and ID genotypes showed higher levels of ACR (1.59 +/- 0.2, DD + ID; 0.8 +/- 0.2 mg/mmol, II; P < 0.006 by ANOVA) and bigger LVMI (124.1 +/- 2.3, DD + ID vs. 117.8 +/- 3.6 g/m2, II; P < 0.01 by ANOVA). No differences in the prevalence and degree of target organ damage (TOD) were found when data were analyzed on the basis of the AGT and AT1 genotypes, respectively. Potentially unfavorable combinations of genotypes were also investigated by K-means cluster analysis. Two subgroups of patients were identified (cluster 1, N = 70; cluster 2, N = 57), and each differed significantly with regards to the presence and degree of TOD and patterns of RAAS gene polymorphisms (F, 15.97 for ACR; F, 7.19 for IMT; F, 217.03 for LVMI; F, 3.91 for ACE; F, 4.06 for AGT; and F, 5. 22 for AT1; df 1 to 214, P < 0.02, for each one of the variables examined).

CONCLUSION

The D allele of the ACE gene may be an independent risk factor for the development of target organ damage, and evaluating it could be useful for assessing cardiovascular risk in EH. Unfavorable patterns of RAAS genotypes seem to predispose patients to subclinical cardiovascular disease in EH.

Angiotensin-II type 1 receptor gene polymorphism and long-term survival in patients with idiopathic congestive heart failure

BACKGROUND

It has been suggested that a genetic polymorphism in the angiotensin II type 1 receptor gene (ATRG) and the ACE gene DD genotype might have a synergistic influence on the risk of developing cardiovascular disease.

AIMS

To study the possible interaction between polymorphisms in the ACE gene and the ATRG, regarding survival and left ventricular function.

METHODS

Polymorphism of the two genes was studied in a population-based cohort of 194 patients with idiopathic heart failure, recruited from the western part of Sweden 1985-1988. The patients were investigated by echocardiography. The survival status was checked during the 7-year follow-up period.

RESULTS

Although there was no statistically significant additive risk of the ATRG polymorphism, patients carrying the ACE gene DD genotype in combination with a C allele of the ATRG tended to have a poorer prognosis. DD +AA, OR 1.24 (95% CI 0.67-2.32, P = 0.49); DD +AC, OR 1.64 (95% CI 0.95-2.83, P = 0.08); DD + CC, OR 3.54 95% CI 0.78-16.1, P = 0.10); DD +AC/CC, OR 1.84 (95% CI 1.10-3.08, P = 0.02). Patients with the DD +AC/CC genotypes tended to have lower ejection fraction and increased left ventricular mass.

CONCLUSIONS

There was a trend toward a worse prognosis in patients with the combination of a C-allele in the ATRG and the ACE gene DD genotype, suggesting an interaction of these two genetic polymorphisms on disease severity.