Genetic variants of proteins from the renin angiotensin system are associated with pressure load cardiac hypertrophy

Association of the common genetic polymorphisms and haplotypes of the chymase gene with left ventricular mass in male patients with symptomatic aortic stenosis

We investigated the association between polymorphisms and haplotypes of the chymase 1 gene (CMA1) and the left ventricular mass index (LVM/BSA) in a large cohort of patients with aortic stenosis (AS). Additionally, the gender differences in cardiac remodeling and hypertrophy were analyzed. The genetic background may affect the myocardial response to pressure overload. In human cardiac tissue, CMA1 is involved in angiotensin II production and TGF-β activation, which are two major players in the pathogenesis of hypertrophy and fibrosis. Preoperative echocardiographic data from 648 patients with significant symptomatic AS were used. The LVM/BSA was significantly lower (p<0.0001), but relative wall thickness (RWT) was significantly higher (p = 0.0009) in the women compared with the men. The haplotypes were reconstructed using six genotyped polymorphisms: rs5248, rs4519248, rs1956932, rs17184822, rs1956923, and rs1800875. The haplotype h1.ACAGGA was associated with higher LVM/BSA (p = 9.84×10⁻⁵), and the haplotype h2.ATAGAG was associated with lower LVM/BSA (p = 0.0061) in men, and no significant differences were found in women. Two polymorphisms within the promoter region of the CMA1 gene, namely rs1800875 (p = 0.0067) and rs1956923 (p = 0.0015), influenced the value of the LVM/BSA in males. The polymorphisms and haplotypes of the CMA1 locus are associated with cardiac hypertrophy in male patients with symptomatic AS. Appropriate methods for the indexation of heart dimensions revealed substantial sex-related differences in the myocardial response to pressure overload.

The global burden of aortic stenosis

Degenerative, calcific valvular aortic stenosis (AS), caused by an active process of atherosclerosis, calcification and ossification, is the most common cause of AS in industrialized nations. The prevalence of calcific AS is age-dependent, and thus is expected to increase due to demographic aging of the global population. It is well recognized that severe AS carries a poor prognosis if left untreated. Despite this recognition, many patients are inappropriately denied surgery because of perceived risk. This article will examine the etiology, prevalence, and current trends in the treatment of degenerative AS focusing on indications for surgical aortic valve replacement.

Left ventricular hypertrophy in aortic valve stenosis: preventive or promotive of systolic dysfunction and heart failure?

AIMS

In aortic stenosis (AS), left ventricular (LV) hypertrophy is considered a compensatory response helping maintain systolic function. Recent research in experimental AS suggests, however, that LV hypertrophy is not necessary to sustain LV contractions but may in fact be maladaptive. The present work aimed to clarify the role of LV hypertrophy in AS-related heart failure (HF) in man.

METHODS AND RESULTS

We studied 137 adult patients with isolated AS undergoing pre-operative echocardiography and cardiac catheterization. HF was diagnosed by the European criteria and LV hypertrophy by sex-specific limits of echocardiographic LV mass. The higher the LV mass was, the poorer was the LV ejection fraction (beta=-0.26, P< 0.001, linear regression) and the greater the likelihood of HF independent of the severity of AS (P< 0.001, logistic regression). In the subgroup of critical AS (valve area <0.4 cm(2)/m(2), n=85), patients with absent LV hypertrophy (n=19) had better preserved ejection fraction (mean+/-SE, 64+/-3 vs. 57+/-2%, P=0.045) and less HF (16 vs. 48%, P=0.025) than patients with LV hypertrophy (n=66).

CONCLUSION

In isolated AS, increased LV mass predicts the presence of systolic dysfunction and HF independent of the severity of valvular obstruction. LV hypertrophy may be maladaptive rather than beneficial in AS in man.

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

OBJECTIVE

The aim of the present study was to determine if there is an association of different gene polymorphisms of renin-angiotensin system and left ventricular hypertrophy (LVH) in patients with essential hypertension (EH) in St Petersburg population.

PATIENTS AND METHODS

We examined 156 patients (the mean age 49+/-8 years) with mild-to-moderate EH recruited from the general population of the outpatient clinic. Left ventricular mass was measured by echocardiography and left ventricular mass index (LVMI) was calculated. Subjects were genotyped for I/D polymorphism of the angiotensin-converting enzyme (ACE) gene, A1166C polymorphism of the AT1 receptor gene, M235T polymorphism of angiotensinogen gene and -6G/A polymorphism of its promoter region.

RESULTS

Genotype distribution of the sample obeyed Hardy-Weinberg equilibrium and was comparable to that reported previously for hypertensive individuals. Groups of patients with II, ID and DD polymorphism of ACE gene did not differ significantly in their LVMI levels. Furthermore, neither ID ACE-gene polymorphism nor ATI-receptor gene and angiotensinogen gene polymorphism was associated with LVH. Additionally, no any significant gene-gene interactions were found to be associated with LVH in the group studied.

CONCLUSIONS

In the light of these observations it seems reasonable to make a preliminary conclusion about lack of association between LVH and distinct polymorphisms of renin-angiotensin system genes in the population studied.

Genes and their polymorphisms in mono- and multifactorial cardiomyopathies: towards pharmacogenomics in heart failure

Cardiomyopathies are diseases of the myocardium associated with cardiac dysfunction, and are classified as dilated cardiomyopathy (DCM), hypertropic cardiomyopathy (HCM) and restrictive cardiomyopathy. Heart failure and sudden death are the two major complications. Also, since DCM is the primary indication for heart transplantation and HCM the primary cause of sudden death in young athletes, the socioeconomic impact of these diseases is important. Recently, the role of the genetic background in both monogenic and multifactorial cardiomyopathies has been studied, which has led to a better understanding of the underlying mechanisms that promote the development and progression of these diseases. Preliminary data suggest interactions between pharmacological treatment and genetic polymorphisms, which appear to be the first steps towards the application of pharmacogenetics in heart failure.

Lack of association among five genetic polymorphisms of the renin-angiotensin system and cardiac hypertrophy in patients with aortic stenosis

BACKGROUND

Patients with aortic stenosis (AS) have left ventricular hypertrophy (LVH). It is thought that LVH in these patients is a consequence of chronic left ventricular pressure overload. However, there is only a poor correlation between the degree of AS and the degree of LVH. Genetic polymorphisms of the renin-angiotensin-aldosterone system (RAAS) have been considered to trigger the response of the left ventricle to chronic pressure overload and determine the degree of LVH in patients with AS.

METHODS

One hundred five consecutive patients with symptomatic AS were examined by echocardiography and left heart catheterization to determine the severity of AS and LVH. Five genetic polymorphisms of the RAAS (ACE, AGTR1, AGT, CMA, CYP11B2) were analyzed in all patients and the results of genetic analysis were correlated to severity of AS and LVH to determine the importance of the polymorphisms for LVH.

RESULTS

All tested genotypes were in Hardy-Weinberg equilibrium and allele frequencies were similar to other study populations. There was no correlation between the severity of AS and the severity of LVH. There was no association between the five tested genotypes of the RAAS and the severity of AS (mean gradient and area of the aortic valve) or LVH (LV muscle mass).

CONCLUSION

We conclude that LVH in patients with AS is not determined by the tested genetic polymorphisms of the RAAS.

Genetic aspects of heart failure

Heart failure is a major health problem and is associated with a high mortality and morbidity. Recently, the role of the genetic background in the onset and the development of the disease has been evidenced in both heart failure with and without systolic dysfunction and in familial and non-familial forms of this condition. Preliminary studies suggest that the I/D polymorphism of the Angiotensin Converting Enzyme gene influence the development of left ventricular hypertrophy, a major determinant of heart failure. Familial hypertrophic cardiomyopathy (FHC) is a highly heterogenous autosomal dominant disease. Seven genes have been identified which all encode proteins of the sarcomere or proteins involved in the regulation of contraction. More than one hundred mutations have been evidenced. Modifier genes such as the I/D polymorphism seem to play a role in the expression of the disease. Susceptibility genes have been searched for in sporadic forms of dilated cardiomyopathy and conflicting results have been published with regard to the I/D polymorphism. Finally, familial forms of dilated cardiomyopathy (FDC) are frequent. Various modes of inheritance and phenotypes have been reported and this condition appears genetically highly heterogenous. It has been postulated that the molecular defect involved in FDC is an abnormality in the transmission of contractile force. The analysis of genetic factors that predispose to heart failure looks promising: it should allow better understanding of the underlying mechanisms that promote the progression of the disease, to identify subjects at risk of the disease who would benefit from early medical management and promote the development of pharmacogenetics.

Renin-angiotensin system gene polymorphisms and left ventricular hypertrophy. The case against an association

There is accumulating evidence for association between genetic polymorphisms of components of the renin angiotensin system (RAS), especially angiotensin-converting enzyme (ACE), and cardiovascular disease. However, there is lack of agreement that the ACE polymorphism is associated with left ventricular hypertrophy (LVH) in hypertension. A possible paradigm for the development of LVH involves the ACE gene polymorphism influencing cardiac mass by an action on plasma and/or tissue levels of angiotensin II. Such a model has experimental support and provides the basis for examining the lack of agreement between studies. The finding of lack of association between RAS gene polymorphism and LVH may be due to methodological problems, differences in genetic background between populations, interactions between genetic variants of RAS components or to the model being inappropriate. Low predictability of ACE genotype markers for LVH together with conflicting reports on the influence of RAS genetic variants on angiotensin II production suggests that the simple RAS paradigm may not apply for hypertension. Further information on the nature of the link between the ACE polymorphism and ACE regulation as well as the relation between the RAS and pathophysiology of LVH is needed. At present there is insufficient evidence to accept ACE gene polymorphism as a susceptibility marker for LVH.

Erythrocyte calpain activity and left ventricular mass in essential hypertension

BACKGROUND

Calpains are cytoplasmic proteases widely distributed among eucaryotic cells. Low levels of calpain activity were found in hypertrophic hearts from hypertensive rats, but its role in hypertrophic hearts from human hypertensives is unknown. Therefore, calpain activity was investigated in erythrocytes from essential hypertensive patients in relation to their left ventricular mass.

OBJECTIVE

To study the role of calpain activity in the development of left ventricular hypertrophy (LVH) in human essential hypertension.

METHODS

A total of 115 hypertensives (72 untreated and 43 with treatment interrupted for at least 4 months) were included in the study. Calpain I activity was measured in human erythrocytes and LVH was measured as left ventricular mass index (LVMI) by M-mode echocardiography.

RESULTS

Values are given as mean+/-SEM. The hypertensives (97 men and 18 women) were 43.5+/-0.9 years old with mild to moderate levels of hypertension (systolic/diastolic blood pressure of 147.9+/-1.4/98.7+/-0.9 mmHg) and relatively recent LVH onset (3.5+/-0.5 years). An inverse relation between LVMI and erythrocytic calpain activity was present in all (P = 0.0023, R2 = 7.9%). This relation was still present considering only untreated hypertensives (P = 0.008; R2 = 9.7%), but was lost in the 43 previously treated hypertensives. Moreover, in the untreated hypertensives, after excluding the possible confounding effects of sex, age, body mass index, blood pressure and duration of hypertension, a stepwise regression showed that only two variables remained significantly related to LVMI: calpain (F = 6.23) and mean arterial pressure (F = 4.689). No relations were found between LVMI and calpastatin activity either in the whole population, or in treated or untreated hypertensives.

CONCLUSIONS

If we assume that the level of erythrocyte calpain activity mirrors the level in cardiomyocytes, these data seem to suggest that increased protein degradation by calpain may prevent the development of LVH in hypertensive patients. This effect is independent of the duration and severity of hypertension.