Lack of association of the renin-angiotensin system genes polymorphisms and left ventricular hypertrophy in hypertension

Association between polymorphisms of genes involved in the Renin-Angiotensin-Aldosterone System and the adaptive morphological and functional responses to essential hypertension

Hypertensive cardiac remodeling is illustrated by increased left ventricular (LV) mass index values and/or relative wall thickness (RWT) values >0.42, and functionally by isolated alteration of LV diastole (abnormal relaxation). The aim of the present study was to establish differentiated models of anatomical and functional adaptation to essential hypertension (EHT), in relation to the genetic variants of genes involved in the Renin-Angiotensin-Aldosterone System (RAAS). The M235T-AGT, I/D-ACE, A1166C-R1AngII, A3123C-R2AngII and G83A-REN genotypes were determined using PCR-Restriction Fragment Length Polymorphism in 139 hypertensive subjects. The relationship between the studied RAAS gene polymorphisms with morphological and functional cardiac remodeling was assessed by multiple logistic regression analysis. Patients carrying the C/C, A/C genotypes (A3123C-R2AngII polymorphism) had a 2.72-fold (P=0.033) increased risk of exhibiting an RWT value <0.42; in the multivariate model the risk was 4.02-fold higher (P=0.008). Analysis of LV diastolic dysfunction (LVDD) revealed that hypertensive patients carrying the T/T, M/T genotypes (M235T-AGT polymorphism) had a 2.24-fold (P=0.037) increased risk of developing LVDD and a 2.42-fold increased risk (P=0.039) after adjustment for confounders. Similarly, carriers of the G/G, A/G genotypes (G83A-REN) had a 2.32-fold (P=0.021) increased risk of developing LVDD, and this remained an independent risk factor based on the multivariate model (P=0.033). The results of the present study showed that no particular gene was associated with increased LV mass, but the A3123C-R2AngII polymorphism was associated with a non-concentric type of cardiac response in hypertensive patients. Conversely, the M235T-AGT and G83A-REN polymorphisms were found to be statistically significantly associated with LVDD when assessing abnormal relaxation.

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

Background: Increasing left ventricular mass in hypertensive patients is an independent prognostic marker for adverse cardiovascular outcomes. Genetic factors have been shown to critically affect left ventricular mass. AGT M235T is one of the genetic polymorphisms that may influence left ventricular mass due to its pivotal role in the regulation of plasma angiotensinogen level as well as hypertension pathophysiology in Asian populations. Currently, how M235T affects left ventricular mass is not well-described in Vietnamese hypertensive patients. This study aimed to investigate the association between M235T and left ventricular mass in Vietnamese patients diagnosed with essential hypertension.

Materials and Methods:AGT M235T genotyping and 2D echocardiography were performed on 187 Vietnamese subjects with essential hypertension. All the ultrasound parameters were obtained to calculate the left ventricular mass index according to the American Society of Echocardiography and the European Association of Cardiovascular Imaging 2015 guidelines. Other clinical characteristics were also recorded, including age, gender, duration of hypertension, hypertensive treatment, lifestyle, renal function, fasting plasma glucose, and lipid profile.

Results: MT and TT genotypes were determined in 30 and 157 subjects, respectively. AGT M235T genotype, duration of hypertension, body mass index, and ejection fraction statistically affected the left ventricular mass index, which was significantly greater in TT compared to MT carriers after adjusting for confounding factors.

Conclusion: The TT genotype of AGT M23T was associated with greater left ventricular mass in Vietnamese patients diagnosed with essential hypertension.

Deletion Polymorphism of Angiotensin Converting Enzyme Gene is Associated with Left Ventricular Hypertrophy in Uighur Hypertension-Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) Patients

Background

This study aimed to explore the association of angiotensin converting enzyme (ACE) gene insertion/deletion polymorphisms with left ventricular hypertrophy (LVH) in Han and Uighur hypertension-OSAHS (obstructive sleep apnea hypopnea syndrome) patients in China.

Material/Methods

A total of 162 Han and 72 Uygur patients with hypertension-OSAHS were independently subdivided into an LVH group and a non-LVH (NLVH) group based on the left ventricular mass index. The insertion/deletion polymorphisms of ACE gene were determined by polymerase chain reaction. The association of ACE gene insertion/deletion polymorphisms with LVH was assessed by chi-squared test. Logistic regression analysis was performed to obtain the odds ratios and 95% confidence intervals for the risk of LVH after adjusting for confounding factors.

Results

In Uighur patients, the distributions of D allele and DD genotype showed significant differences between the LVH group and the NLVH group. The difference of DD genotype remained significant after multivariate adjustment. In contrast, no significant differences were observed in the distributions of D allele and DD genotype between the LVH group and the NLVH group in Han patients. Moreover, moderate-severe OSAHS was an independent risk factor for LVH.

Conclusions

D allele and DD genotype of ACE gene are possible genetic markers for the risk of LVH in Uighur but not Han hypertension-OSAHS patients.

The utility of copy number variation (CNV) in studies of hypertension-related left ventricular hypertrophy (LVH): rationale, potential and challenges

The ultimate goal of human genetics is to understand the role of genome variation in elucidating human traits and diseases. Besides single nucleotide polymorphism (SNP), copy number variation (CNV), defined as gains or losses of a DNA segment larger than 1 kb, has recently emerged as an important tool in understanding heritable source of human genomic differences. It has been shown to contribute to genetic susceptibility of various common and complex diseases. Despite a handful of publications, its role in cardiovascular diseases remains largely unknown. Here, we deliberate on the currently available technologies for CNV detection. The possible utility and the potential roles of CNV in exploring the mechanisms of cardiac remodeling in hypertension will also be addressed. Finally, we discuss the challenges for investigations of CNV in cardiovascular diseases and its possible implications in diagnosis of hypertension-related left ventricular hypertrophy (LVH).

Association of left ventricular mass with the AGTR1 A1166C polymorphism

BACKGROUND

The A1166C polymorphism is located within the microRNA-155 binding site of the human angiotensin II (Ang II) type-1 receptor (AGTR1) gene. The C allele interferes with the base-pairing complementariness between AGTR1 mRNA and microRNA-155 and thereby increases AGTR1 protein expression in vitro. We hypothesized that left ventricular (LV) mass is associated with the AGTR1 A1166C polymorphism.

METHODS

Among 708 individuals (mean age, 49.4 years; 51.8% women) randomly recruited in a white European population, we measured LV structure by two-dimensional guided M-mode echocardiography, the AGTR1 A1166C polymorphism and the 24-h urinary aldosterone. We applied a mixed model to assess phenotype-genotype associations while adjusting for covariables and accounting for relatedness.

RESULTS

The AA (49.1%), AC (42.8%), and CC (8.1%) genotypes were in Hardy-Weinberg equilibrium. Using a recessive model, CC homozygotes compared to A-allele carriers showed significant increases (P < 0.021) in LV mass index (+5.78 ± 2.25 g/m(2)), mean wall thickness (MWT) (+0.48 ± 0.15 mm), interventricular septum (IVS) (+0.60 ± 0.18 mm) and posterior wall thickness (PWT) (+0.34 ± 0.15 mm), but lower 24-h urinary aldosterone excretion (geometric mean, 22.4 vs. 19.0 nmol; P = 0.050). Sensitivity analyses in 552 participants untreated for hypertension were confirmatory.

CONCLUSIONS

LV mass index is associated with the AGTR1 A1166C polymorphism. Further research should clarify to what extent this association might be mediated via different expression of AGTR1 as modulated by microRNA-155.

Association of echocardiographic left ventricular structure with the ACE D/I polymorphism: a meta-analysis

Introduction: In a previous meta-analysis, we derived pooled estimates for the association of left ventricular mass (LVM) and hypertrophy (LVH), as diagnosed by electrocardiography or echocardiography, with the ACE D/I polymorphism. We updated this meta-analysis until May 2009 only considering echocardiographic phenotypes.

Methods: We computed pooled estimates from a random-effects model.

Results: Across 38 studies, both DD homozygotes ( n = 2440) and DI heterozygotes ( n = 4310) had higher ( p ≤ 0.002) LVM or LVM index than II homozygotes ( n = 2229). Across 21 studies with available data, this was due to increased mean wall thickness (MWT) with no difference in left ventricular internal diameter (LVID). Standardised differences (DD versus II) were 0.39 ( p < 0.001) for LVM, 0.34 ( p = 0.009) for MWT, and 0.066 ( p = 0.26) for LVID. Across 16 studies (4894 participants), the pooled odds ratios of LVH (versus II homozygotes) were 1.11 ( p = 0.29) and 1.02 ( p = 0.88) for the DD and DI genotypes, respectively. Sensitivity analyses were confirmatory.

Conclusions: Our meta-analysis supports the hypothesis that the enhanced ACE activity associated with the D allele is associated with higher LV mass. Smaller sample size might explain the lack of significant association with LVH.

The risk of coronary artery disease associated with cigarette smoking and hypercholesterolemia is additionally increased by the presence of the AT1R gene 1166C allele

Cigarette smoking and hypercholesterolemia influence the renin-angiotensin system (RAS) functions, including increased RAS-mediated vasoconstriction, mitogenic signaling, and angiotensin II type 1 receptor (AT1R) expression. We have explored the interactions of the AT1R gene 1166 A>C polymorphism and traditional risk factors using an epidemiological approach. The study cohort included 341 subjects; 172 were patients with angiographically confirmed coronary artery disease (CAD) and 169 were blood donors. The 1166 A>C polymorphism was genotyped using the PCR-RFLP method. We found a synergy of the 1166C allele with cigarette smoking (synergy indices: SI = 1.41, SIM = 1.33), LDL cholesterol levels > or = 3 mmol/l (SI = 1.25, SIM = 1.19), and elevated total cholesterol (> or =5 mmol/l) levels (SI = 1.15, SIM = 1.13). In each case, the estimated CAD risk was greater than that predicted by assuming the additivity and multiplication of effects. We conclude that the 1166C allele increases the risk of CAD associated with the presence of cigarette smoking and hypercholesterolemia.

Ten renin-angiotensin system-related gene polymorphisms in maximally treated Canadian Caucasian patients with heart failure

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The progression and pharmacological response of heart failure-affected patients are subject to interindividual variability. It is also acknowledged that the genotype frequency of certain gene polymorphisms varies across different ethnic groups and that a difference in gene polymorphism frequencies between healthy and heart failure patients seems to exist.

WHAT THIS STUDY ADDS

This study investigated associations between 10 gene polymorphisms of RAAS-related genes with an individual's susceptibility to heart failure. Our data suggest that the angiotensinogen (AGT) 235 single nucleotide polymorphism (SNP) may be associated with heart failure in our population and that the AGT(M174)-AGT(T235) haplotype, as well as the AGT/angiotensin-converting enzyme (ACE) gene combination, may play an important role in disease predisposition.

AIMS

Racial differences in survival outcomes point towards a genetic role in the pathophysiology of heart failure. Furthermore, contemporary evidence links genetics to heart failure (HF) predisposition. We tested for a difference in prevalence of 10 renin-angiotensin-aldosterone system (RAAS)-related gene polymorphisms between a homogenous population of HF patients and healthy controls.

METHODS

One hundred and eleven healthy volunteers and 58 HF patients were included in this study. The healthy control group consisted of males aged between 18 and 35 years old. The HF group consisted of patients (89.7% male) who were 63.8 +/- 7.9 years old, were in New York Heart Association (NYHA) class II-III and had a documented left ventricular ejection fraction (LVEF)

CONCLUSIONS

This study demonstrates that the SNPs of AGT may be associated with HF in our population and that the AGT/ACE gene combination may play an important role in disease predisposition.

Collapse

Key Words

• ace
• angiotensin
• heart failure
• polymorphisms
• raas
• renin

Collapse

MESH Headings

• Adolescent
• Adult
• Aged
• Canada/epidemiology
• Double-Blind Method
• Female
• Gene Frequency/genetics
• Genetic Predisposition to Disease/genetics
• Heart Failure/blood
• Heart Failure/genetics
• Humans
• Male
• Middle Aged
• Polymorphism, Genetic
• Renin-Angiotensin System/genetics
• White People/genetics

Collapse

Grants Collapse

Affiliation(s)

Marcin Zakrzewski-Jakubiak Université de MontréalMontréal, Canada
Simon de Denus Université de MontréalMontréal, Canada Montreal Heart InstituteMontréal, Canada
Marie-Pierre Dubé Montreal Heart InstituteMontréal, Canada
François Bélanger Université de MontréalMontréal, Canada
Michel White Montreal Heart InstituteMontréal, Canada
Jacques Turgeon Université de MontréalMontréal, Canada

Collapse

Genetic polymorphisms and heart failure

Heart failure is a complex clinical syndrome. There is evidence for a genetic contribution to the pathophysiology of heart failure. Considering the fundamental role of neurohormonal factors in the pathophysiology and progression of cardiac dysfunction and hypertrophy, variants of genes involved in this system are logical candidate genes in heart failure. In this report, genetic polymorphisms of the major neurohormonal systems in heart failure will be discussed. Studies on polymorphisms of the renin-angiotensin-aldosterone system (RAAS), adrenergic receptor polymorphisms, endothelin (receptor) polymorphisms, and a group of miscellaneous polymorphisms that may be involved in the development or phenotypic expression of heart failure will be reviewed. Research on left ventricular hypertrophy is also included. The majority of genetic association studies focused on the ACE I/D polymorphism. Initial genetic associations have often been difficult to replicate, mainly due to problems in study design and lack of power. Promising results have been obtained with genetic polymorphisms of the RAAS and sympathetic system. Considering the evidence so far, a modifying role for these polymorphisms seems more likely than a role of these variants as susceptibility genes. Besides the need for larger studies to examine the effects of single nucleotide polymorphisms and haplotypes, future studies also need to focus on the complexity of these systems and study gene-gene interactions and gene-environment interactions.

Association of Angiotensin Converting Enzyme Gene Polymorphisms with Left Ventricular Hypertrophy

The angiotensin converting enzyme gene (ACE) is of much interest as a candidate gene conferring an individual's genetic susceptibility to left ventricular hypertrophy (LVH). LVH has long been thought to be an end point of essential hypertension (EH), rather than a separate entity, though it is influenced by a unique set of hormonal, vascular and genetic factors. In this study, we attempted to determine whether two representative polymorphisms of the ACE gene, ACE I/D and 2350 G>A, known to be associated with EH and to have a highly significant influence on plasma ACE levels, could implicate ACE as a quantitative trait locus (QTL) for LVH. We carried out a retrospective, case-control study of the two ACE polymorphisms amongst 180 nationals (50 LVH patients and 130 controls) from the United Arab Emirates (Emirati)--an ethnic group characterized by an absence of alcohol intake and cigarette smoking--for putative correlations with LVH. Clinical diagnoses of LVH were based on echocardiographic and ECG criteria. ACE I/D and 2350 G>A genotypes were determined by polymerase chain reaction (PCR) and restriction digestion. Univariate and multivariate logistic regression analyses revealed an association between ACE polymorphisms and LVH. Haplotype analysis further supported this finding. The ACE I/D and ACE 2350 G>A polymorphisms were in strong linkage disequilibrium and were independently associated with LVH, suggesting that ACE is likely to be a QTL for LVH. In conclusion, This is the first association study of the ACE 2350 G>A polymorphism with LVH; the results showed that this polymorphism, along with ACE I/D, is associated with LVH.

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.