Molecular variant of angiotensinogen gene is associated with coronary atherosclerosis

Clinical Utility of Amplification Refractory Mutation System-Based PCR and Mutation-Specific PCR for Precise and Rapid Genotyping of Angiotensin-Converting Enzyme 1 (ACE1-rs4646996 D>I) and Angiotensin-Converting Enzyme 2 (ACE2-rs4240157T>C) Gene Variations in Coronary Artery Disease and Their Strong Association with Its Disease Susceptibility and Progression

Background: Experimental clinical and research studies demonstrated that the renin−angiotensin system (RAS) affects the pathogenesis of atherosclerosis and the prognosis of coronary heart disease (CHD). The results show that ACE2 (angiotensin I-converting enzyme 2) might act as a protective protein for cardiovascular diseases; however, only a few studies in human populations have been carried out. The aim of this study was to develop, optimize, and validate a direct T-ARMS-based PCR assay for the precise and rapid genotyping of ACE1-rs4646996 D>I and ACE2-rs4240157T>C and study their association with coronary artery disease susceptibility and progression. Methodology: This study included 149 consecutive coronary artery disease patients and 150 healthy controls. We utilized T-ARMS for the precise and rapid genotyping of ACE2-rs4240157; rs4646994. Results: Our results indicated that the ACE1-rs4646996 D>I genotypes observed between CAD cases and controls were statistically significant (p < 0.008) and, similarly, the ACE2-rs4240157T>C genotypes observed were significant (p < 0.0001). Moreover, the frequency of the D allele (ACE1-D>I) and C allele (ACE2-rs4240157T>C) was found to be higher among CAD patients than the HC. Our results indicated that in the codominant model, the ACE2-ID genotype was strongly associated with increased CAD susceptibility in a codominant model with an OR of 2.37, (95%) CI = (1.023−5.504), and p < 0.04. Similarly, the ACE2-DD genotype was strongly associated with an increased CAD susceptibility with an OR of 3.48, (95%) CI = (1.49 to 8.117), and p < 0.003. Similarly, in allelic comparison, the D allele was strongly associated with CAD susceptibility with an OR of 1.59, (95%) CI = (1.12−2.24), and p < 0.003. Our results revealed that there was a significant correlation between ACE2-I/D genotypes and hypertension, T2D, and obesity (p < 0.05). The results of ACE2 rs4240157 genotyping indicated a strong association in the codominant model with an increased CAD susceptibility with an OR of 3.62, (95%) CI = (2.027 to 6.481), and p < 0.0001. Similarly, in a dominant inheritance model, a strong association is observed between the ACE2 rs4240157 (CT+CC) genotype with an OR of 6.34, (95%) CI = (3.741 to 10.749), and p < 0.0001. In allelic comparison, the T allele was strongly associated with CAD susceptibility with an OR of 5.56, (95% CI = (3.56 to 7.17), and p < 0.0001. Similarly, our results revealed that there was a significant association of the ACE2-rs4240157T>C genotypes with Triglycerides (mg/dL), HDL-C (mg/dL), total Cholesterol (mg/dL), and C-reactive protein (mg/L) in CAD. Conclusion: It was indicated that the ARMS technique and MS-PCR assay proved to be fast, accurate, and reliable for ACE2-rs4240157T>C and ACE1-rs4646996 D>I, respectively, and can be used as a potential molecular tool in the diagnosis of genetic diseases in undeveloped and developing countries—where there might be a shortage of medical resources and supplies. ACE1-I>D genotypes were strongly associated with T2D, hypertension, and obesity (p < 0.002). Besides the ACE2-rs4240157 CT heterozygosity genotype, the T allele was strongly associated with CAD susceptibility. Future longitudinal studies in different ethnic populations with larger sample sizes are recommended to validate these findings

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

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

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.

Renin-Angiotensin System Polymorphisms and Coronary Artery Surgery Patients

The frequencies of angiotensin-converting enzyme gene insertion/deletion, angiotensinogen-M253T, and angiotensin II type 1 receptor-A1166C polymorphisms were analyzed in 105 patients undergoing coronary artery bypass grafting (group 1) and a control group of 105 non-cardiac patients (group 2). Blood samples were obtained for biochemical analyses and DNA extraction. Genotyping was performed by polymerase-chain-reaction-based restriction analysis. According to the angiotensin-converting enzyme gene insertion/deletion polymorphism, 36.3% of patients in group 1 and 30.7% in group 2 were homozygous for the DD allele. This difference was not statistically significant. Angiotensin II type 1 receptor-A1166C genotype polymorphism was also not significantly different between the groups. The results showed the angiotensinogen-M235T polymorphism to be heterogenous. The MM homozygote frequency was significantly higher in controls (72.3%), whereas 80% of the TT homozygote frequency was in the surgical group ( p = 0.001). These results show that although there were no significant differences in angiotensin-converting enzyme gene insertion/deletion and angiotensin II type 1 receptor-A1166C genotype polymorphisms between the groups, angiotensinogen-M235T polymorphism of TT homozygote frequency was significantly associated with patients undergoing coronary artery bypass surgery.

Correlation between renin-angiotensin system gene polymorphisms and essential hypertension in the Chinese Yi ethnic group

INTRODUCTION

The renin-angiotensin system (RAS) has been considered to play an important role in the regulation of blood pressure. This study aimed to investigate the correlation between RAS gene polymorphisms and essential hypertension (EH) in the Chinese Yi ethnic group.

MATERIALS AND METHODS

A total of 244 EH subjects and 185 normotensive individuals from the Chinese Yi ethnic group were genotyped for AGT M235T (rs699), AT1R A1166C (rs5186), ACE I/D (rs4340) and ACE G2350A (rs4343) polymorphisms by the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method.

RESULTS

Significant differences in the allele and genotype frequency of ACE G2350A were observed between the EH cases and controls (p=0.001, 0.002). After being grouped by gender, significant differences in the allele and genotype frequency of ACE G2350A and AT1R A1166C were observed between females of the EH cases and controls (ACE G2350A: p=0.000, 0.002; AT1R A1166C: p=0.008, 0.011). After excluding the influence of multifactorial interactions, the ACE G2350A polymorphism is significantly associated with the pathogenesis of EH in the Chinese Yi ethnic group (odds ratio (OR)=1.656, 95% confidence interval (CI) 1.807-2.524, p=0.019).

CONCLUSIONS

The RAS-related ACE G2350A polymorphism is associated with the pathogenesis of EH in the Chinese Yi ethnic group.

Hypoxia-induced endothelial progenitor cell function is blunted in angiotensinogen knockout mice

Angiotensinogen (AGT), the precursor of angiotensin I, is known to be involved in tumor angiogenesis and associated with the pathogenesis of coronary atherosclerosis. This study was undertaken to determine the role played by AGT in endothelial progenitor cells (EPCs) in tumor progression and metastasis. It was found that the number of EPC colonies formed by AGT heterozygous knockout (AGT(+/-)) cells was less than that formed by wild-type (WT) cells, and that the migration and tube formation abilities of AGT(+/-) EPCs were significantly lower than those of WT EPCs. In addition, the gene expressions of vascular endothelial growth factor (VEGF), Flk1, angiopoietin (Ang)-1, Ang-2, Tie-2, stromal derived factor (SDF)-1, C-X-C chemokine receptor type 4 (CXCR4), and of endothelial nitric oxide synthase (eNOS) were suppressed in AGT(+/-) EPCs. Furthermore, the expressions of hypoxia-inducible factor (HIF)-1α and -2α were downregulated in AGT(+/-) early EPCs under hypoxic conditions, suggesting a blunting of response to hypoxia. Moreover, the activation of Akt/eNOS signaling pathways induced by VEGF, epithelial growth factor (EGF), or SDF-1α were suppressed in AGT(+/-) EPCs. In AGT(+/-) mice, the incorporation of EPCs into the tumor vasculature was significantly reduced, and lung tumor growth and melanoma metastasis were attenuated. In conclusion, AGT is required for hypoxia-induced vasculogenesis.

Gender specificity of a genetic variant of angiotensin-converting enzyme and risk of coronary artery disease

Etiological factors for coronary artery disease (CAD) involve a wide range of gene and environmental interactions. One of the systems being implicated in the pathophysiology of CAD is the renin-angiotensin system (RAS). However, the genetic polymorphisms of this system have not been widely studied in Iranian patients diagnosed with CAD. The aim of this study was to assess the relationship between six gene polymorphisms of RAS components and CAD in a sample of Iranian population. A total of 374 participants were enrolled in a case/control study. The presence of CAD was determined by coronary angiography. Genotyping of six RAS gene polymorphisms was performed using a modified PCR-RFLP method. Our results revealed, for the first time, a significant independent association of angiotensin-converting enzyme (ACE) A-240T polymorphism and incidence of CAD among Iranian women (P=0.005, OR=20.4, 95% CI=2.49-41.2). There has also been a significant difference in genotype distribution of ACE A-240T (P=0.008) and angiotensin II receptor type 2 C3123A polymorphism (P=0.032) in Iranian female participants. In conclusion, TT genotype of ACE A-240T seems to be a genetic risk factor for CAD in Iranian women.

Association of the angiotensinogen gene polymorphism with atherosclerosis and its risk traits in the Saudi population

Background

Angiotensinogen (AGT) constitutes a central component of the renin-angiotensin system that controls the systemic blood pressure and several other cardiovascular functions and may play an important role in atherosclerosis pathways. In this study, we employed TaqMan genotyping assays to evaluate the role of 8 AGT variants in primary hypertension (HTN), type 2 diabetes mellitus (T2DM), and obesity as a possible trigger of coronary artery disease (CAD) in a population of 4615 angiographed native Saudi individuals.

Methods

Linkage analysis was done by using the Affymetrix Gene Chip array, sequencing by using the MegaBACE DNA analysis system and genotyping accomplished by TaqMan chemistry using the Applied Biosystem real-time Prism 7900HT Sequence Detection System.

Results

Six variants, rs2067853 GG [Odds ratio(95% Confidence Interval) = 1.44(1.17-1.78); p = 0.001], rs7079 [1.49(1.20-1.85); p < 0.0001], rs699 G [1.19(1.08-1.13); p < 0.0001], rs3789679 A [1.51(1.14-1.99); p = 0.004], rs2148582 GG [1.31(1.11-1.55); p = 0.002] and rs5051 TC + CC [1.32(1.13-1.60); p = 0.001] conferred risk for HTN (3521 cases versus 1094 controls). The rs2067853 (p = 0.042), rs699G (p = 0.007) and rs5051 (p = 0.051) also conferred risk for myocardial infarction (MI; 2982 vs 1633), while rs3789679 A (p < 0.0001) and GA + AA (p < 0.0001) as well as rs4762G (p = 0.019) were associated with obesity (1576 vs 2458). However, while these variants appeared to be also associated with CAD (2323 vs 2292), only the rs7079G (p = 0.035) retained its significant relationship. Interestingly, among the haplotypes constructed from these SNPs, the baseline 8-mer haplotype, GGTGGGGT (χ² = 7.02; p = 0.0081) and another GGCGGAGT (χ² = 5.10; p = 0.024), together with several of their derivatives were associated with HTN. T2DM was associated with two 8-mer haplotypes, GGTAGGAC (χ² = 5.66; p = 0.017) and ATTGAGAC (χ² = 5.93; p = 0.015), obesity with GGCGGAGT (χ² = 9.49; p = 0.0021) and MI was linked to ATTGGGAC (χ² = 6.68; p = 0.010) and GGTGGGAT (χ² = 4.25; p = 0.039). Furthermore, several causative haplotypes were also shared among the risk traits as well as with CAD.

Conclusion

These results point to AGT as independently conferring risk for various cardiovascular traits, and possibly interacting with these traits in events leading to atherosclerosis.

Elevated properdin and enhanced complement activation in first-degree relatives of South Asian subjects with type 2 diabetes

OBJECTIVE

Emerging data implicate activation of the complement cascade in the pathogenesis of type 2 diabetes. The objective of the current study was to evaluate the relationships between components of the complement system, metabolic risk factors, and family history of type 2 diabetes in healthy South Asians.

RESEARCH DESIGN AND METHODS

We recruited 119 healthy, first-degree relatives of South Asian subjects with type 2 diabetes (SARs) and 119 age- and sex-matched, healthy South Asian control subjects (SACs). Fasting blood samples were taken for measurement of complement factors and standard metabolic risk factors.

RESULTS

SARs were characterized by significantly higher properdin (mean concentration 12.6 [95% CI 12.2-13.1] mg/L vs. SACs 10.1 [9.7-10.5] mg/L, P < 0.0001), factor B (187.4 [180.1-195.0] mg/L vs. SACs 165.0 [158.0-172.2] mg/L, P < 0.0001), and SC5b-9 (92.0 [86.1-98.3] ng/mL vs. SACs 75.3 [71.9-78.9] ng/mL, P < 0.0001) and increased homeostasis model assessment of insulin resistance (2.86 [2.61-3.13] vs. SACs 2.31 [2.05-2.61], P = 0.007). C-reactive protein did not differ between SARs and SACs (P = 0.17). In subgroup analysis of 25 SARs and 25 SACs with normal oral glucose tolerance tests, properdin, factor B, and SC5b-9 remained significantly elevated in SARs.

CONCLUSIONS

Increased properdin and complement activation are associated with a family history of type 2 diabetes in South Asians independent of insulin resistance, and predate the development of impaired fasting glucose and impaired glucose tolerance. Properdin and SC5b-9 may be novel biomarkers for future risk of type 2 diabetes in this high-risk population and warrant further investigation.

Association between polymorphisms of the renin angiotensin system and carotid stenosis

OBJECTIVE

Carotid stenosis is a common manifestation of systemic atherosclerosis. Apart from traditional risk factors, genetic determinants, such as polymorphisms of the renin angiotensin system (RAS), may be relevant in modulating the atherosclerotic process leading to carotid stenosis. In this study, we investigated the role of angiotensin-converting enzyme (ACE) I/D and -240A>T, angiotensinogen (AGT) M235T, and angiotensin type 1 receptor (AGTR1) 1166A > C polymorphisms in modulating the susceptibility to the disease.

METHODS

Eight hundred twenty-one consecutive patients with severe carotid stenosis (≥70%) and 847 control subjects were investigated.

RESULTS

A significant difference in genotype distribution (P < .0001) and allele frequency (P < .0001) between patients and controls for the ACE I/D polymorphism, but not for the other single-nucleotide polymorphisms investigated, was observed. The ACE D allele frequency was significantly higher in patients without traditional risk factors in comparison with that observed in those with at least one risk factor (0.71 vs 0.61; P = .04). The ACE D allele significantly influenced carotid stenosis under dominant, recessive, and additive model of inheritance at both univariate (P < .0001) and multivariate analysis (P < .0001). When the combined effect of RAS unfavorable alleles was considered, patients carrying less than three alleles had a lower risk of carotid stenosis (odds ratio [OR], 0.79 [0.63-0.99]; P = .05), while carriers of more than four unfavorable alleles had an increased risk (OR, 1.44 [1.12-1.84]; P = .004), in comparison with subjects carrying three or four unfavorable alleles. ACE D allele frequency was similar in patients with and without additional atherosclerotic localizations (0.61 vs 0.62, respectively).

CONCLUSIONS

Our findings evidence a role for ACE I/D polymorphism in influencing the susceptibility to carotid stenosis, even in the absence of traditional risk factors. Interestingly, our findings provided further information concerning the role of this polymorphism in modulating the atherosclerotic process apart from its different localizations.

The M235T polymorphism of the angiotensinogen gene in South Indian patients of hypertrophic cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a complex disorder and genetically transmitted cardiac disease with a diverse clinical course. The objective of the present study was to examine the association of the T704C polymorphism of exon 2 of the angiotensinogen (AGT) gene with HCM in a South Indian population from Andhra Pradesh. Subjects and methods. One-hundred and fifty HCM (90 sporadic hypertrophic cardiomyopathy [SHCM] and 60 familial hypertrophic cardiomyopathy [FHCM]) patients and 165 age- and sex-matched normal healthy controls without known hypertension and left ventricular hypertrophy were included in the study. DNA was isolated from peripheral leukocytes and the region of interest in the AGT gene bearing a missense mutation methionine to threonine substitution at codon 235 (M235T) of exon 2, was amplified by polymerase chain reaction (PCR). The PCR products were subjected to restriction digestion with the enzyme SfaNI.

RESULTS

Significant differences were detected in genotypic distribution (p = 0.04) as well as the allelic frequency (p = 0.003) between the SHCM patients and controls. The polymorphism did not show any association with FHCM.

CONCLUSION

Our results suggest that the T allele of the AGT gene is significantly associated with SHCM in a South Indian population from Andhra Pradesh. However, we did not find significant association of this polymorphism with FHCM.

Angiotensinogen gene polymorphism in acute myocardial infarction patients

Introduction. The objective of the study was to explore the role of a genetic variant of angiotensinogen (AGT), M235T, as an independent risk factor for acute myocardial infarction (AMI) and to investigate the possible association with the severity of coronary artery disease (CAD), estimated on the basis of the number of coronary stenoses and critical arterial occlusions.

Patients and methods. 123 AMI patients were compared to 144 healthy controls. AGT genotypes were determined by PCR.

Results. A significant association was found between AGT M235T polymorphism and AMI ( p = .021). By logistic regression, the TT genotype appeared to confer 1.9-fold increased risk for AMI in both the univariate and the multivariate model. The frequencies of the TT genotype and T allele increased with the number of stenoses in coronary vessels. Moreover, the TT genotype and the T allele were more frequent in the subgroup of patients with stenoses in at least four coronary vessels than in other patients, including subjects with one- to three-vessel disease. Furthermore, the TT genotype and the T allele were significantly more frequent in patients with critical arterial occlusions (> 90%) than in subjects without critical stenoses.

Conclusions. The AGT M235T polymorphism associates with AMI risk and influences CAD severity.

Multilocus analysis in candidate genes ACE, AGT, and AGTR1 and predisposition to peripheral arterial disease: role of ACE D/-240T haplotype

OBJECTIVE

Peripheral arterial disease (PAD) is a common manifestation of systemic atherosclerosis. Apart from traditional cardiovascular risk factors, several novel biologic mediators and genetic predisposing factors appear relevant in determining the atherogenetic process leading to PAD. Genes encoding for renin angiotensin system (RAS) components have been proposed as candidate in atherosclerosis. This study investigated four polymorphisms in angiotensinogen (AGT), angiotensin converting enzyme (ACE), and angiotensin II receptor type 1 (AGTR1), genes of RAS, in both predicting PAD and modulating the severity of the disease.

METHODS

The ACE I/D and -240A>T, AGT M235T, and AGTR1 1166A>C polymorphisms were analyzed in 281 PAD patients and in 485 controls comparable for age and sex.

RESULTS

The ACE D and -240T alleles both significantly influenced the predisposition to PAD. The ACE D, but not -240 T, allele remained associated with PAD after Bonferroni correction (P = .004) and adjustment for cardiovascular risk factors (P = .03). The ACE D allele influenced PAD predisposition with a dose-dependent effect (odds ratio for ACE ID vs II genotype, 1.77; P = .006; ACE DD vs II genotype, 2.15; P = .001). The haplotype reconstruction analysis for the ACE gene showed that the D/-240T haplotype significantly and independently influenced the predisposition to PAD (P = .02). In 190 PAD patients with no additional atherosclerotic localizations (isolated PAD), a significant association between ACE D and -240T alleles and PAD was observed. Only the ACE D allele remained associated with isolated PAD after Bonferroni correction (P = .02) and after adjustment for cardiovascular risk factors (P = .02). The haplotype reconstruction analysis for the ACE gene showed that the D/-240T, but not the D/-240A haplotype significantly influenced the predisposition to PAD (P = .0003). No influence of the polymorphisms analyzed on the severity of the disease, according to Rutherford categories, was found.

CONCLUSIONS

The present study contributes data to highlight the role of the ACED/-240T haplotype in predisposing to PAD, also in the absence of other atherosclerotic comorbidities.

Angiotensin II type 1 receptor gene polymorphism in myocardial infarction patients

Introduction. Acute myocardial infarction is commonly known as heart attack. It is a multifactorial disease influenced by environmental and genetic factors.The objective of the present study was to investigate the association of the angiotensin II type 1 receptor gene A/C polymorphism in South Indian myocardial infarction patients.

Subjects and methods. The present study included a total number of 221 subjects (107 myocardial infarction patients and 114 age- and sex-matched controls). Demographic and clinical characteristics were collected. Lipid profiles were estimated. DNA was isolated and the angiotensin II type 1 receptor gene A/C polymorphism was determined by polymerase chain reaction.

Results. Comparison of the lipid profiles between patients and controls showed that patients had statistically highly significant values (p=0.0001).The CC genotype of the angiotensin II type 1 receptor was not associated with myocardial infarction patients when compared to controls. CC vs. AA was χ2 = 2.08, odds ratio 2.30, 95% confidence interval 0.72 — 7.23, and p value was 0.14.

Conclusion. The angiotensin II type 1 receptor CC genotype is not a risk factor for myocardial infarction in patients in a South Indian population.

The M235T polymorphism in the AGT gene and CHD risk: evidence of a Hardy-Weinberg equilibrium violation and publication bias in a meta-analysis

Background

The M235T polymorphism in the AGT gene has been related to an increased risk of hypertension. This finding may also suggest an increased risk of coronary heart disease (CHD).

Methodology/Principal Findings

A case-cohort study was conducted in 1,732 unrelated middle-age women (210 CHD cases and 1,522 controls) from a prospective cohort of 15,236 initially healthy Dutch women. We applied a Cox proportional hazards model to study the association of the polymorphism with acute myocardial infarction (AMI) (n = 71) and CHD. In the case-cohort study, no increased risk for CHD was found under the additive genetic model (hazard ratio [HR] = 1.20; 95% confidence interval [CI], 0.86 to 1.68; P = 0.28). This result was not changed by adjustment (HR = 1.17; 95% CI, 0.83 to 1.64; P = 0.38) nor by using dominant, recessive and pairwise genetic models. Analyses for AMI risk under the additive genetic model also did not show any statistically significant association (crude HR = 1.14; 95% CI, 0.93 to 1.39; P = 0.20). To evaluate the association, a comprehensive systematic review and meta-analysis were undertaken of all studies published up to February 2007 (searched through PubMed/MEDLINE, Web of Science and EMBASE). The meta-analysis (38 studies with 13284 cases and 18722 controls) showed a per-allele odds ratio (OR) of 1.08 (95% CI, 1.01 to 1.15; P = 0.02). Moderate to large levels of heterogeneity were identified between studies. Hardy-Weinberg equilibrium (HWE) violation and the mean age of cases were statistically significant sources of the observed variation. In a stratum of non-HWE violation studies, there was no effect. An asymmetric funnel plot, the Egger's test (P = 0.066), and the Begg-Mazumdar test (P = 0.074) were all suggestive of the presence of publication bias.

Conclusions/Significance

The pooled OR of the present meta-analysis, including our own data, presented evidence that there is an increase in the risk of CHD conferred by the M235T variant of the AGT gene. However, the relevance of this weakly positive overall association remains uncertain because it may be due to various residual biases, including HWE-violation and publication biases.

Heritability of carotid intima-media thickness: a twin study

OBJECTIVE

To estimate the heritability of carotid intima-media thickness (IMT), a surrogate marker for atherosclerosis, independent of traditional coronary risk factors.

METHODS AND RESULTS

We performed a classical twin study of carotid IMT using 98 middle-aged male twin pairs, 58 monozygotic (MZ) and 40 dizygotic (DZ) pairs, from the Vietnam Era Twin Registry. All twins were free of overt cardiovascular disease. Carotid IMT was measured by ultrasound. Bivariate and multivariate analyses were used to determine the association between traditional cardiovascular risk factors and carotid IMT. Intraclass correlation coefficients and genetic modeling techniques were used to determine the relative contributions of genes and environment to the variation in carotid IMT. In our sample, the mean of the maximum carotid IMT was 0.75+/-0.11. Age, systolic blood pressure and HDL were significantly associated with carotid IMT. The intraclass correlation coefficient for carotid IMT was larger in MZ (0.66; 95% confidence interval [CI], 0.62-0.69) than in DZ twins (0.37; 95% CI, 0.29-0.44), and the unadjusted heritability was 0.69 (95% CI, 0.54-0.79). After adjusting for traditional coronary risk factors, the heritability of carotid IMT was slightly reduced but still of considerable magnitude (0.59; 95% CI, 0.39-0.73).

CONCLUSION

Genetic factors have a substantial influence on the variation of carotid IMT. Most of this genetic effect occurs through pathways independent of traditional coronary risk factors.

Placental abruption is more frequent in women with the angiotensinogen Thr235 mutation

OBJECTIVE

Obstetrical complications such as preeclampsia, fetal growth restriction, and placental abruption are associated with inadequate placental perfusion. Previous studies have shown that the angiotensinogen (AGT) Thr235 mutation is associated with abnormal remodeling of the uterine spiral arteries and occurs at higher frequencies in preeclampsia. This study was done to evaluate whether the AGT Thr235 mutation increases the risk of placental abruption.

MATERIALS AND METHODS

We compared 62 placentas from women who had placental abruption with 240 control patients of similar age and ethnicity. DNA was extracted from paraffin blocks from placentas. AGT Met235Thr mutation status was determined by single fluoresceine labeled probe real-time PCR using a LightCycler system.

RESULT

AGT genotypes were divided into three groups: MM (homozygous wild), TT (homozygous mutant), and MT (heterozygous). The constituent ratio of AGT genotype in abrupted placentas (MM 14.5%, MT 43.5%, TT 41.9%) was significantly different from in control group (MM42.5%, MT 39.6%, TT 17.9%) (p<0.001). AGT mutant allele frequency in placental abruption (0.637) was significantly higher than in the control group (0.377) (p<0.001).

CONCLUSION

The AGT Thr235 mutation was observed more frequently in placental abruption. AGT Thr235 mutation may be considered a risk factor for placental abruption.

How frequent is altered gene expression among susceptibility genes to human complex disorders?

It is regularly thought that human complex disorder susceptibility genes show differences in gene expression between normal and pathologic tissues. Thus, differences of transcript amounts could be indicative of complex disorder susceptibility loci and, therefore, be used for the discovery or the validation of human susceptibility genes to complex disorders/traits. Whether human complex disorder susceptibility genes effectively display differences in transcript amounts was tested by meta-analysis of the published literature comparing transcript amounts of well-validated human susceptibility genes to complex traits/disorders. A total of 94 gene-disease associations, which were studied in at least three independent studies and showed strong evidence of positive association, were analyzed. For 23 out of these 94 well-validated gene-disease associations, 120 gene expression studies comparing normal and pathologic human tissues were found. For 60 out of these 120 gene expression studies, the difference of level expression between normal and pathologic human tissues was statistically significant. This result was highly significant, as only 6 significant results were expected randomly under the null hypothesis (P < 10(-112)). A large excess of replication studies were also found, which were in agreement with the original report (P = 6 x 10(-4)). However, the overall level of expression change between normal and pathologic human tissues was relatively moderate, because only 36 (60%) and 19 (31.6%) out of the 62 statistically significant gene expression studies reached 2- or 3-fold changes in expression level, respectively. The present meta-analysis confirms statistical differences of expression levels between normal and pathologic human tissues for human susceptibility genes to complex traits/disorders. However, the levels of differences in transcript amounts appear to be relatively weak. These findings rationalize the use of gene expression for the discovery/validation of human susceptibility genes, but the weak differences of expression typically found should be taken into account for the design of such studies.

Processing of surfactant protein C requires a type II transmembrane topology directed by juxtamembrane positively charged residues

Surfactant protein C (SP-C) is a lung-specific protein that is synthesized as a 21-kDa integral membrane propeptide (pro-SP-C) and proteolytically processed to a 3.7-kDa secretory product. Previous studies have shown that palmitoylation of pro-SP-C is dependent on two N-terminal juxtamembrane positively charged residues. We hypothesized that these residues influence modification of pro-SP-C by directing transmembrane orientation. Double substitution mutation of these juxtaposed residues from positive to neutral charged species resulted in complete reversal of transmembrane orientation of pro-SP-C and total abrogation of post-translational processing. Mutation of a single residue resulted in mixed orientation. Protein trafficking studies in A549 cells showed that while the double mutant was retained in the endoplasmic reticulum, single mutants produced a mixed pattern of both endoplasmic reticulum (double mutant-like) and vesicular (wild type-like) expression. Our study demonstrates the crucial role juxtamembrane positively charged residues play in establishing membrane topology and their influence on the trafficking and processing of pro-SP-C. Moreover this study provides a likely precedent for a mechanism in disorders associated with mutations in the membrane-flanking region of integral membrane proteins.

Genetic testing for coronary heart disease: the approaching frontier

The prospect for genetic testing to better delineate the risk for coronary heart disease will become a reality in the next decade. Advances in this area will follow the accelerated trajectory in our ability to dissect the genetics of complex diseases including coronary heart disease. A brief overview of the present state of knowledge will follow the discussion of present approaches in discovering these genetic predispositions. The key issues that will likely shape the field in the near future will also be presented.

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.

Coronary heart disease, hypertension, and angiotensinogen gene variants in Indian population

Gene encoding components of the renin angiotensin system (RAS) have been implicated with the increased risk of cardiovascular disease (CVD). Two variants of the angiotensinogen (AGT) gene, M235T and T174M, have been shown to be associated with increased risk of hypertension. In the present study, we examined the association of these two polymorphisms and their synergistic interaction with the angiotensin I-converting enzyme (ACE) deletion homozygote genotype (D/D) on subjects with coronary heart disease (CHD) and hypertension. We studied 131 healthy individuals, 141 angiographically verified CHD patients, and 159 hypertensive subjects. The identification of the ACE and AGT gene polymorphisms was carried out using a PCR-based restriction endonuclease digestion method. There was no significant difference in the distribution of the M235T and T174M variants between the two test groups and the control group. Association was also not seen when analysis was carried out in patients when subgrouped according to the extent of the severity of the disease. In addition, the risk was not restricted to subjects carrying the D allele of the ACE gene and T235T of AGT. M235T and T174M variants do not contribute to the increased risk of CHD or hypertension in the Indian population.

Associations between angiotensinogen gene variants and left ventricular mass and function in the HyperGEN study

BACKGROUND

The angiotensinogen M235T polymorphism is positively associated with plasma angiotensinogen, hypertension, and coronary heart disease. However, the association of M235T polymorphism with left ventricular (LV) mass and function is not well defined at the population level. We investigated whether 2 tightly linked polymorphisms of angiotensinogen gene, M235T and G-6A, are associated with LV mass and function in a large population-based sample, composed mostly of patients with hypertension.

METHODS

Two-dimensional guided M-mode and pulsed Doppler scan echocardiograms were performed in 605 participants. The angiotensinogen M235T was analyzed with a standard polymerase chain reaction test, and the G-6A variant was measured with mass spectrophotometry.

RESULTS

The association of angiotensinogen gene to LV mass and LV mass indexed to body surface area (LVMI) differed significantly between subjects with normotensive and hypertensive conditions with respect to the direction of association (P <.005). The methionine-threonine/threonine-threonine genotype was negatively associated with LV mass and LVMI in patients with hypertension after adjustment for blood pressure, antihypertensive medication use, weight, and other covariates (P <.001), and patients with normotensive conditions with the methionine-threonine/threonine-threonine genotype had higher LV mass and LVMI (P =.04, for LV mass; P =.14, for LVMI). The association in patients with normotensive conditions was not influenced by blood pressure but was partly confounded by weight.

CONCLUSION

Variation in the angiotensinogen gene was modestly associated with LV mass independently of covariates in patients with hypertensive conditions. The direction of the association was opposite to that observed in patients with normotensive conditions, probably because of the influence of other risk factors or antihypertensive medication use or both.

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.

Insertion-deletion polymorphism in the gene for angiotensin-converting enzyme is associated with obstetric cholestasis but not with preeclampsia

OBJECTIVE

Our purpose was to investigate the contribution of angiotensin-converting enzyme insertion-deletion polymorphism in the development of obstetric complications.

STUDY DESIGN

In a retrospective case-control study, angiotensin-converting enzyme insertion-deletion polymorphism was investigated in a control group of healthy women (n = 115) and in a group of women diagnosed with preeclampsia (n = 133) and obstetric cholestasis (n = 57). Polymerase chain reaction detection of insertion-deletion polymorphism was used to determine the presence of the two angiotensin-converting enzyme alleles in the groups; the frequencies in the general population in our area are presented for comparison.

RESULTS

The frequency of the D allele was 43.9% among women with obstetric cholestasis and 27% among healthy fertile women, which is close to the rate in the general population in our area (28%). The odds ratio for obstetric cholestasis associated with the DD genotype was 2.12 (95% CI, 1.08-4.12) compared with the pooled II and ID genotypes (P = .03). Neither the ID genotype distributions nor the allele frequencies differed significantly between preeclamptic and normotensive pregnancies (P = .36).

CONCLUSION

The present data indicate that the DD genotype is a genetic marker associated with an elevated risk of obstetric cholestasis, but this polymorphism of the angiotensin-converting enzyme gene is unlikely to play any significant role in preeclampsia.

Insulin resistance precedes the appearance of albuminuria in non-diabetic subjects: 6 years follow up study

Microalbuminuria is a marker of increased risk of cardiovascular mortality in type 1 and type 2 diabetes, and in non-diabetic subjects. Little is known about the association between prospective changes of microalbuminuria and the risk factors of atherosclerosis, or gene polymorphism in non-diabetic subjects. We conducted a 6-year prospective study of risk factors for progression of albuminuria in non-diabetic subjects. The participants were 116 non-diabetic subjects who consecutively underwent medical examinations for Japanese-Americans living in Hawaii. In the baseline examination in 1992, normoalbuminuria was found in all subjects. After 6 years, 101 subjects remained normoalbuminuria (non-progressors), 15 subjects changing from normoalbuminuria to microalbuminuria or proteinuria and were defined as progressors. In progressors, compared with non-progressors, the fasting insulin level and HOMA-R were significantly higher at 3 years follow-up, and the systolic and diastolic pressure and Sigma insulin level were significantly higher at 6 years follow-up. Insulin resistance appeared earlier than the appearance of hypertension and albuminuria. In progressors, there was no significant correlation with angiotensin-converting enzyme (ACE) genotype or angiotensinogen (AGT) genotype compared with non-progressors. Therefore, the appearance of insulin resistance should be regarded as a remarkable mediator of albuminuria.

Homozygosity for angiotensinogen 235T variant increases the risk of myocardial infarction in patients with multi-vessel coronary artery disease

OBJECTIVE

Molecular variants of the angiotensinogen (AGT) and the angiotensin II type 1 receptor (ATR) genes have been associated with the risk of coronary artery disease (CAD) and myocardial infarction (MI), but data so far available are conflicting. The primary object of the paper is to verify this possible association by a rigorous, angiographically controlled study in a large sample of patients with or without multi-vessel CAD.

DESIGN

We designed a large case-control study in Italian patients candidates for coronary artery bypass grafting, with angiographically documented multi-vessel CAD, compared to subjects with angiographically documented normal coronary arteries.

METHODS AND RESULTS

AGT M235T and ATR A1166C gene polymorphisms were analysed in 699 subjects; 454 patients were candidates for coronary artery bypass grafting, having angiographically documented (mainly multi-vessel) CAD. An appropriate documentation of previous MI was obtained from 404/454 (89%, 247 with and 157 without MI). Subjects (n = 245) with angiographically documented normal coronary arteries, were included as control group (CAD-free group). CAD patients had a substantial burden of conventional risk factors as compared with controls free of coronary atherosclerosis. Age, gender, smoking habit and number of stenosed vessels were the only differences between patients with or without previous myocardial infarction, who were similarly exposed to the other conventional risk factors (including hypertension). AGT M235T and ATR A1166C allele and genotype frequencies were similar between CAD and CAD-free patients. In the CAD group, AGT 235T allele was found more frequently in subjects with a previous myocardial infarction (0.494 versus 0.414; P < or = 0.05). By logistic regression, homozygosity for AGT 235T variant appeared to confer 1.9-fold increased risk for MI in both the univariate and the multivariate (adjusted for age, gender, smoking habit and number of stenosed vessels) model.

CONCLUSIONS

AGT 235 T homozygous patients with multivessel CAD have an increased risk of myocardial infarction as compared with subjects with clinically similar phenotype but different genotype.

Angiotensin-converting enzyme and angiotensinogen gene polymorphisms are non-randomly distributed in oral contraceptive-induced hypertension

OBJECTIVES AND METHODS

Oral contraceptives (OC) usage increases serum angiotensinogen levels to three to five times normal and about 5% of these women develop arterial hypertension. The genetic contribution to this susceptibility to OC-induced hypertension is poorly understood. We have analyzed the genotypes of 149 hypertensive and 101 normotensive women using oral contraceptives, for three genetic polymorphisms in genes of the renin-angiotensin system: an insertion/deletion (I/ D) in the angiotensin converting enzyme (ACE) gene, the T235M polymorphism of the angiotensinogen gene (AGT) and a point mutation in its promoter.

RESULTS

After cessation of oral contraception the mean arterial pressures of the hypertensive women were separable into two non-overlapping groups; 88 of the women remained hypertensive and 61 returned to normal blood pressure. Both groups of hypertensive women had a similarly higher frequency of hypertensive relatives than the normotensive women, but were otherwise similar. The 235T allele of AGT was significantly increased in frequency in the 61 oral contraceptive-inducible hypertensive women compared with the controls and the 88 women that remained hypertensive. The ACE I/D genotypes were similarly distributed within the three groups of women, but were distinctly non-random in the oral contraceptive-induced hypertensive women when they were also classified by AGT genotype.

CONCLUSION

This statistical interaction of genotype frequencies suggests that the genetic basis of susceptibility to OC-induced hypertension is complex.

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.

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.

Synergistic effect of angiotensin-converting enzyme and angiotensinogen gene on cardiac hypertrophy

AIMS

There are controversies concerning the association of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism with left ventricular hypertrophy (LVH), and the unclear association between angiotensinogen (ATG) M235T polymorphism and LVH. We investigated both the separate and interactive effects of these two genes on LVH in patients (N=396) with cardiovascular disease and normal healthy volunteers (N=133).

RESULTS

Frequency of DD genotype of ACE gene was significantly (P<0.05) higher in patients with LVH than patients without LVH or normal controls. Frequency of IT genotype of ATG gene in patients with LVH was significantly (P<0.01) greater than that in normal controls or marginally (P=0.1) higher than that in patients without LVH. These findings were also observed in normotensive patients and normal controls after excluding hypertensive patients. Only in patient group, the frequency of DD genotype in the highest quartile of LVMI was significantly greater than that in the lowest quartile (P<0.05). The higher tendency of TT genotype in the highest quartile patients compared with that in the lowest, did not reach statistical significance. In combined genotype analysis, there was a remarkable difference in LVMI between the two extreme double homozygotes only in patient group (156+/-25 versus 109+/-25 g/m2 for TT+DD versus MM+II) (P<0.01). In ANCOVA, the interaction term composed of ACE and ATG genotype was a significant independent variable for LVMI only in the male patient group (P<0.01).

CONCLUSION

The D-allele of ACE and T-allele of ATG gene exert a synergistic effect on cardiac hypertrophy in male patients with cardiovascular diseases, but not in normal healthy population.

Appropriate tissue- and cell-specific expression of a single copy human angiotensinogen transgene specifically targeted upstream of the HPRT locus by homologous recombination

Development of experimental models by genetic manipulation in mice has proven to be very useful in determining the significance of particular genes in the development of or susceptibility to hypertension. Advances in molecular genetics, transgenic mouse technology, and physiological measurements in mice provided an opportunity to go a step further and develop models to analyze the physiological significance of specific gene variants potentially causing hypertension. In this report, we describe the development of a human angiotensinogen transgenic mouse model generated by targeting the human angiotensinogen gene upstream of the mouse HPRT locus by homologous recombination. The main benefit of this transgenic mouse model is that the human angiotensinogen gene is inserted into the mouse genome as a single copy at a predefined locus and in a specific orientation-a process that can be repeated utilizing other variants of this gene. We establish the validity of this approach by showing that the hAGT(hprt) mice have normal tissue- and cell-specific expression of the human angiotensinogen gene and normally produce and process the hAGT protein at physiological levels.

Renin-angiotensin-aldosterone system gene polymorphisms and hypertension in Hong Kong Chinese

In Chinese populations, hypertension is common and is a major risk factor for cerebrovascular and coronary heart disease. The renin-angiotensin-aldosterone system (RAAS) helps maintain blood pressure and salt homeostasis and appears important in the pathogenesis of hypertension and some forms of vascular disease. We investigated three RAAS gene polymorphisms, the angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen (AGT) M235T and angiotensin II type 1 receptor A1166C polymorphisms in 232 hypertensive and 178 normotensive Chinese subjects. The hypertensives were generally more obese and dyslipidaemic. No significant differences in genotype or allele frequencies for any of the polymorphisms were identified between the groups, nor was there any interactive contribution to blood pressure by the ACE and AGT polymorphisms. However, there were large differences in genotype and allele frequencies between the healthy Chinese and published data for equivalent Caucasian populations. These findings suggest these polymorphisms are unlikely to be involved in the pathogenesis of hypertension in Chinese.

Regulated expression of human angiotensinogen gene by hepatocyte nuclear factor 4 and chicken ovalbumin upstream promoter-transcription factor

We previously identified various upstream and downstream regulatory elements and factors important for hepatic expression of the human angiotensinogen (ANG) gene, the precursor of vasoactive octapeptide angiotensin II. In the present study, to further investigate the molecular mechanism of human ANG transcriptional regulation, we generated transgenic mice carrying the fusion gene composed of the 1. 3-kilobase promoter of the human ANG gene, its downstream enhancer, and the chloramphenicol acetyltransferase reporter gene. Because expression of the chloramphenicol acetyltransferase gene was observed strongly in the liver and weakly in the kidney, we suspected that hepatocyte nuclear factor (HNF) 4 with a tissue expression pattern similar to that of the reporter gene would regulate ANG transcription. In vitro assays indicated that HNF4 bound to the promoter elements and strongly activated the ANG transcription, but that chicken ovalbumin upstream promoter transcription factor (COUP-TF), a transcriptional repressor, dramatically repressed human ANG transcription through the promoter elements and the downstream enhancer core elements. Furthermore, COUP-TF dramatically decreased the human ANG transcription in the mouse liver by the Helios Gene Gun system in vivo. These results suggest that an interplay between HNF4 and COUP-TF could be important in hepatic human ANG transcription.

The genotype interactions of methylenetetrahydrofolate reductase and renin-angiotensin system genes are associated with myocardial infarction

We analyzed the evolution with age of the frequencies of the I/D polymorphism of the angiotensin I-converting enzyme (ACE), a1166c of the angiotensin II AT1 receptor (AT1R), M235T of the angiotensinogen (AGT) and A225V of their methylenetetrahydrofolate reductase (MTHFR) gene in a healthy (H) population and the subsequent comparison to age- and sex-matched groups of myocardial infarction (MI) subjects. A total of 472 H subjects were divided into three groups < 30, 30-55 and > 55 years old and 277 individuals with MI into two groups 30-55 and > 55 years old. The evolution with age showed that the AGT M allele (P < 0.001) and the MTHFR V allele (P < 0.05) frequency decreased with age in H men. The comparison between healthy and MI groups showed that the MM genotype frequency increased in MI men > 55 years (OR =4.16; 95% CI; 1.72-10.1) The cc genotype showed a similar behaviour (OR = 3.96; 95% CI; 1.21-12.9). In men, all the combinations with MM genotype presented a high risk, with OR values between 1.10 and 7.22. In women, the cc genotype increased in the MI > 55 group (OR = 6.66; 95% CI; 2.02-21.9). All the combinations with the cc genotype showed OR values between 1.71 and 13.3. The MM genotype in men and cc genotype in men and women, are independent risk factors for MI. We propose that the study of the allele frequency evolution in an H population at different ages is essential to determine risk factors for MI in case-control studies, since data from isolated age-matched groups can be misinterpreted.

Angiotensinogen M235T polymorphism is associated with plasma angiotensinogen and cardiovascular disease

BACKGROUND

Genes encoding components of the renin-angiotensin system have been associated with elevated blood pressure (BP) and an increased risk of coronary artery disease. To explore the role of the angiotensinogen (AGT) gene in coronary atherosclerosis and thrombosis, we studied the effect of the AGT M235T gene variant on plasma AGT levels and BP in patients with coronary artery disease and in the subgroup of survivors of myocardial infarction as compared with angiographically defined control subjects.

METHODS AND RESULTS

This was a case-control study of 301 white male subjects examined at Frankfurt University medical center. Plasma AGT levels increased stepwise according to the number of T235 alleles present (no T235 allele, 14.8 +/- 3.9 nmol/L; 1 allele, 15.7 +/- 5.1 nmol/L; 2 alleles, 17.3 +/- 4.7 nmol/L; P =.006). In a multivariate model, circulating AGT emerged as the most important predictor of diastolic pressure (P =.001). In addition, AGT M235T gene polymorphism remained a significant predictor of diastolic BP in a multivariate model adjusted for age, body mass index, fasting glucose, apolipoprotein B, presence of coronary artery disease, and treatment with antihypertensive agents ( P <.05). Finally, homozygosity for T235 was associated with increased univariate risk of coronary artery disease and myocardial infarction (odds ratio estimates 1.5; 95% confidence intervals 1.1 to 2.1, P =.03, and 1.0 to 2.1, P =.05, respectively).

CONCLUSIONS

The significant relations observed between the AGT M235T variant, its protein product, and the cardiovascular disease phenotypes provide evidence for a possible role of elevated circulating AGT in the pathogenesis of coronary artery disease.

New insights into the genetics of preeclampsia

Preeclampsia is familial. Pedigree analyses suggest that one or more common alleles may act as "preeclampsia susceptibility genes." The authors speculate that genes involved in blood pressure control, volume regulation, placental health, vascular disease, and vascular remodeling, underlie familial susceptibility to preeclampsia. Several candidate genes have been examined. These data suggest that a common mutation in the angiotensinogen promoter, A(-6), leads to elevated expression of this gene and pleiotropic effects, including abnormal spiral artery remodeling and failed hypervolemia of pregnancy. The factor V Leiden mutation, which predisposes women to thromboembolic disorders during pregnancy, has been implicated as another preeclampsia susceptibility gene. New insights into the genetics of preeclampsia will contribute to the understanding of this disease and should ultimately lead to improved diagnosis and treatment.

M235T angiotensinogen gene polymorphism and cardiovascular renal risk

OBJECTIVE

In this meta-analysis, we attempted to derive pooled estimates for the putative associations between various cardiovascular-renal disorders and the M235T polymorphism of the angiotensinogen gene.

METHODS

Case-control studies were combined, using the Mantel and Haenszel approach. Joint P values for continuous variables were calculated by Stouffer's method. Continuous measurements reported in different units were expressed on a percentage scale using the intrastudy mean of the MM genotype as denominator.

RESULTS

The computerized database used for this analysis included 69 reports with an overall sample size of 27,906 subjects. Overall, possession of the T allele was associated with an increased risk of hypertension. In comparison with the MM reference group (number of studies, n = 32), the excess risk was 31% (P = 0.001) in TT homozygotes and 11% (P = 0.03) in TM heterozygotes. The sensitivity analysis showed that this association was present only in whites (T allelic frequency, f = 42.2%), but not in blacks (f = 77.0%) or Asians (f = 78.0%). Atherosclerotic complications (n = 12), renal microvascular disorders (n = 13), cardiomyopathy (n = 2) or diabetic retinopathy (n = 3) were not correlated with the M235T polymorphism. Publication bias was observed for hypertension, but not for coronary heart disease, including myocardial infarction, and for microvascular nephropathy. Furthermore, in comparison with the MM control group, the circulating angiotensinogen levels (n = 8) were raised by 11 and 7% (P = 0.01) in TT and TM subjects, respectively. In contrast, plasma levels of the angiotensin I converting enzyme (n = 4) and body mass index (n = 15) were not associated with the T allele.

CONCLUSION

The T allele encoding angiotensinogen is not associated with atherosclerotic or microvascular complications, but in Caucasians behaves as a marker for hypertension. This association, which may have been inflated by publication bias, does not necessarily imply causality.

Exon-I is involved in positive as well as negative regulation of human angiotensinogen gene expression

Angiotensinogen is the glycoprotein precursor of one of the most potent vasoactive hormones, angiotensin-II. Angiotensinogen gene is primarily expressed in the liver, and this gene locus is linked with human essential hypertension. We show here that a mutation in exon-I reduces the basal expression of the human angiotensinogen gene in liver cells. We also show that a nucleotide sequence in exon-I binds to liver-enriched transcription factor HNF-3 and a ubiquitous factor AP4. Our studies also show that transient transfection of an expression vector containing AP4 coding sequence downregulates the expression of reporter constructs containing human angiotensinogen gene promoter. By contrast, co-transfection of an expression vector containing HNF-3beta coding sequence increases the expression of these reporter constructs. The human angiotensinogen gene has a C/A polymorphism located at -20, and we have shown that estrogen receptor-alpha binds to this sequence when nucleoside A is present at this site. We show here that co-transfection of an expression vector containing AP4 coding sequence reduces estrogen-induced promoter activity of reporter constructs containing human angiotensinogen gene promoter (with nucleoside A at -20) attached to the CAT gene. These studies partly explain the molecular mechanisms involved in tissue-specific expression of the human angiotensinogen gene.

DBP binds to the proximal promoter and regulates liver-specific expression of the human angiotensinogen gene

Angiotensinogen is the glycoprotein precursor of one of the most potent vasoactive hormones, angiotensin-II. It has been shown recently that an ATF like element (ALE) located between bases -102 and -87 of the human angiotensinogen gene plays an important role in liver specific expression of this gene and binds to CREB/ATF family of transcription factors and a novel factor (ALF). We show here that this sequence binds to the liver enriched transcription factor DBP and cotransfection of expression vector CMV-DBP increases the expression of reporter constructs containing this sequence. In addition, we show that transcription factor C/EBP-delta binds to this sequence and an expression vector containing C/EBP-delta coding region increases the expression of reporter constructs containing this sequence. Since DBP is involved in circadian rhythm, our studies suggest that this sequence may be involved in circadian expression of the human angiotensinogen gene.

Associations of angiotensinogen gene mutations with hypertension and myocardial infarction in a gulf population

To date, the human angiotensinogen (AGT) gene and some of its variants represent the best examples of genetic influences that are involved in the determination of essential hypertension (EH) and associated cardiovascular diseases (CVDs). To assess the value of genotyping AGT in a genetically homogeneous population, we carried out a retrospective, case control study of variants M235T and T174M for putative correlations with CVDs among nationals from the United Arab Emirates (Emirati)--an ethnic group characterized by no alcohol intake and no cigarette smoking. We investigated a sample population of 229 Emirati (119 males and 110 females), comprising groups of controls and patients with clinical diagnoses of EH, left ventricular hypertrophy (LVH), ischaemic heart disease (IHD) and myocardial infarction (MI). M235T and T174M alleles were determined via assays based on the polymerase chain reaction. T174M showed no correlation with any of the four clinical entities included in this study. T235 alleles, however, occurred more frequently in the EH group and less frequently in the group of MI survivors. We also found that T235 allele frequencies decreased with age, indicating that in the Emirati population, T235 alleles are associated with a reduced life span and that this effect could occur through independent mechanisms underlying genetic susceptibilities to both EH and MI.

M235T polymorphism of the angiotensinogen gene and hypertension in Chinese

OBJECTIVES

To compare the distributions of the genotypes and alleles of the M235T polymorphism of the angiotensinogen gene for hypertensive patients and normotensive controls.

DESIGN

A study of association of genetic polymorphisms.

SETTING

An outpatient clinic run by a university department handling referrals from primary care.

PATIENTS

Two hundred and four subjects, 103 normal controls and 101 patients with newly diagnosed or documented hypertension.

METHOD

Genomic DNA was extracted from peripheral blood leucocytes, amplified by polymerase chain reaction and digested with the restriction enzyme Tth 111 I. Methionine (M) and threonine (T) alleles were identified after electrophoresis.

MAIN OUTCOME MEASURES

Prevalences of angiotensinogen genotypes and alleles for hypertensive patients and controls.

RESULTS

MM, TM and TT genotypes occurred in 3, 24 and 73% of controls and 1, 22 and 77% of hypertensive patients, respectively. The prevalences of the M and T alleles were 0.15 and 0.85 among controls and 0.12 and 0.88 among hypertensive patients. The prevalences of the angiotensinogen genotypes and alleles for controls and hypertensive patients did not differ significantly.

CONCLUSIONS

Our findings differed from previous reports and suggested that this polymorphism is not associated with hypertension in this population.