Angiotensinogen gene polymorphism in Japanese patients with hypertrophic cardiomyopathy

Association between ACE and AGT polymorphism and cardiovascular risk in acromegalic patients

PURPOSE

Whether the renin-angiotensin-aldosterone system plays a role or not in the development of cardiovascular morbidity in acromegaly patients is unknown. The aim of the study was to investigate the association between ACE (I/D) and AGT (M235T) gene polymorphisms and cardiovascular and metabolic disorders in the acromegaly.

METHODS

The study included one hundred and seventeen acromegalic patients (62 F/55 M, age: 50.2 ± 12.3 years) and 106 healthy controls (92 F/14 M, age: 41.4 ± 11.3 years). PCR method was used to evaluate the prevalence of ACE and AGT genotype.

RESULTS

The genotypes of ACE polymorphism in acromegalic patients were distributed as follows; 41.0% (n: 48) for DD, 44.4% (n: 52) for ID and 14.5% (n: 17) for II genotype. The control group had significantly different distribution of the ACE polymorphism [48.1% (n: 51) for DD, 25.5% (n: 27) for ID and 26.4% (n: 28) for II genotype]compared to acromegalic group. Regarding AGT polymorphism, AGT-MT genotype was seen in 88.9% of the acromegalic patients while MM and TT genotype (9.4% and 1.7%, respectively) were present in the rest. The controls had similar distribution of the AGT genotype with the acromegaly group (80.2% MT genotype, 15.1% MM genotype and 4.7% TT genotype). Due to the small number of patients with TT allele (n: 2), T carriers for AGT genotype (AGT-MT+TT) were subgrouped and compared to those with AGT-MM group. ACE-DD, ID and II groups had similar anthropometric measures, blood pressure values and baseline GH and IGF-1 levels. Significantly higher baseline GH levels were found in AGT-MM group compared to T allele carriers [40 (16-60) vs. 12 (5-36) µg/L, p < 0.05]. The compared groups in both polymorphisms had similar fasting plasma glucose levels. Patients with ACE-II genotype had significantly higher HDL-C levels compared to those with ACE-DD and ACE-ID polymorphisms (p < 0.05) whereas there was no significant difference in lipid profile between AGT-MM group and AGT-T allele carriers. Moreover, the compared groups in both polymorphisms had similar distribution of hyperlipidemia, hypertension, impaired glucose metabolism (prediabetes or type 2 diabetes mellitus) and coronary artery disease. In terms of echocardiographic parameters, systolic and diastolic function was similar among the groups in ACE and AGT genotypes. Interestingly, AGT-MM group had higher mitral inflow A_peak values than T allele carriers (0.94 ± 0.46 vs. 0.73 ± 0.20; p = 0.051). No significant difference was observed in LV mass index values in acromegalic patients among the groups in both polymorphisms.

CONCLUSIONS

Both ACE (I/D) and AGT (M235T) gene polymorphisms do not seem to have a significant effect on the development of clinical properties or cardiovascular comordities of acromegalic patients.

The angiotensinogen gene polymorphism is associated with heart failure among Asians

The angiotensinogen (AGT) gene M235T polymorphism has been suggested to be linked to risk of heart failure (HF). However, association studies on the M235T polymorphism and HF risk have shown conflicting results. PubMed and China Biology Medicine (CBM) databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association. A total of 1,281 HF cases and 1,376 controls were included in the analysis. The pooled data showed that there was no significant associations between the AGT M235T polymorphism and HF risk for TT vs. MM (OR = 1.17, 95%CI = 0.62–2.19, P = 0.635), MT vs. MM (OR = 0.97, 95%CI = 0.77–1.22, P = 0.776), MT/TT vs. MM (OR = 1.07, 95%CI = 0.67–1.69, P = 0.781), and TT vs. MM/MT (OR = 1.23, 95%CI = 0.86–1.76, P = 0.259). In contrast, in the HF subgroup analysis by ethnicity, the AGT M235T polymorphism had a decreased risk of HF among Asians (MT vs. MM, OR = 0.39, 95%CI = 0.17–0.92, P = 0.032). Our results suggest that the AGT M235T polymorphism is a low-penetrant risk factor for the development of HF among Asians.

The influence of Angiotensin converting enzyme and angiotensinogen gene polymorphisms on hypertrophic cardiomyopathy

Some studies have reported that angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes have been associated with hypertrophic cardiomyopathy (HCM). However, there have been inconsonant results among different studies. To clarify the influence of ACE and AGT on HCM, a systemic review and meta-analysis of case-control studies were performed. The following databases were searched to indentify related studies: PubMed database, the Embase database, the Cochrane Central Register of Controlled Trials database, China National Knowledge Information database, and Chinese Scientific and Technological Journal database. Search terms included "hypertrophic cardiomyopathy", "angiotensin converting enzyme" (ACE) or "ACE" and "polymorphism or mutation". For the association of AGT M235T polymorphism and HCM, "angiotensin converting enzyme" or "ACE" was replaced with "angiotensinogen". A total of seventeen studies were included in our review. For the association of ACE I/D polymorphism and HCM, eleven literatures were included in the meta-analysis on association of penetrance and genotype. Similarly, six case-control studies were included in the meta-analysis for AGT M235T. For ACE I/D polymorphism, the comparison of DI/II genotype vs DD genotype was performed in the present meta-analysis. The OR was 0.73 (95% CI: 0.527, 0.998, P = 0.049, power = 94%, alpha = 0.05) after the study which deviated from Hardy-Weinberg Equilibrium was excluded, indicating that the ACE I/D gene polymorphism might be associated with HCM. The AGT M235T polymorphism did not significantly affect the risk of HCM. In addition, ACE I/D gene polymorphism did not significantly influence the interventricular septal thickness in HCM patients. In conclusion, the ACE I/D polymorphism might be associated with the risk of HCM.

Angiotensinogen gene variations and LV outflow obstruction in hypertrophic cardiomyopathy

BACKGROUND

Variations of angiotensinogen (AGT) gene have been associated with cardiac hypertrophy. We hypothesized that AGT gene polymorphism may play a modifier role in the diversity of left ventricular outflow obstruction.

METHODS

The polymorphisms of the AGT gene were genotyped in 225 patients with hypertrophic cardiomyopathy (HCM) and 243 age-and sex-matched healthy controls. The effect of the A and G alleles on the expression of the reporter gene were evaluated in vitro using dual-luciferase reporter assays.

RESULTS

Our results showed that the frequency of the A allele was higher in patients than in controls (50.2 % vs. 35.8 %, p < 0.05). Patients carrying the AA and AG genotypes had a higher proportion of left ventricular outflow obstruction (30.1 % vs. 17.0 %, p < 0.05) and heart failure (NYHA functional class III ~ IV, 35.4 % vs. 18.8 %, p < 0.05) than those carrying the GG genotype had. After adjusted for age, sex, the thickness of the interventricular septum, family history of HCM, and sudden death, the A allele conferred a 2.4-fold risk for left ventricular outflow obstruction than the GG genotype did (adjusted OR = 2.4, 95 %CI 1.2-4.8). The G allele suppressed the expression of the reporter gene significantly compared with the A allele (p < 0.05).

CONCLUSION

AGT gene variations may be genetic modifiers for the development of HCM.

The role of renin-angiotensin-aldosterone system polymorphisms in phenotypic expression of MYBPC3-related hypertrophic cardiomyopathy

The phenotypic variability of hypertrophic cardiomyopathy (HCM) in patients with identical pathogenic mutations suggests additional modifiers. In view of the regulatory role in cardiac function, blood pressure, and electrolyte homeostasis, polymorphisms in the renin-angiotensin-aldosterone system (RAAS) are candidates for modifying phenotypic expression. In order to investigate whether RAAS polymorphisms modulate HCM phenotype, we selected a large cohort of carriers of one of the three functionally equivalent truncating mutations in the MYBPC3 gene. Family-based association analysis was performed to analyze the effects of five candidate RAAS polymorphisms (ACE, rs4646994; AGTR1, rs5186; CMA, rs1800875; AGT, rs699; CYP11B2, rs1799998) in 368 subjects carrying one of the three mutations in the MYBPC3 gene. Interventricular septum (IVS) thickness and Wigle score were assessed by 2D-echocardiography. SNPs in the RAAS system were analyzed separately and combined as a pro-left ventricular hypertrophy (LVH) score for effects on the HCM phenotype. Analyzing the five polymorphisms separately for effects on IVS thickness and Wigle score detected two modest associations. Carriers of the CC genotype in the AGT gene had less pronounced IVS thickness compared with CT and TT genotype carriers. The DD polymorphism in the ACE gene was associated with a high Wigle score (P=0.01). No association was detected between the pro-LVH score and IVS thickness or Wigle score. In conclusion, in contrast to previous studies, in our large study population of HCM patients with functionally equivalent mutations in the MYBPC3 gene we did not find major effects of genetic variation within the genes of the RAAS system on phenotypic expression of HCM.

Interaction of A-240T and A2350G related genotypes of angiotensin-converting enzyme (ACE) is associated with decreased serum ACE activity and blood pressure in a healthy Iranian population

Most of renin-angiotensin system (RAS) gene polymorphisms have not yet been studied in the Iranian population. In the present study, the frequencies of common polymorphisms in the RAS genes, including angiotensin-converting enzyme (ACE) insertion/deletion (I/D) and three single-nucleotide polymorphisms (SNPs), i.e., A-240T, T-93C and A2350G, angiotensinogen M235T, angiotensin II receptor type 1 A1166C and angiotensin II receptor type 2 C3123A variants were determined in DNAs extracted from venous blood of 104 healthy Iranian volunteers. Genotyping was performed by PCR-RFLP method. Serum ACE activity was also assayed using reverse phase HPLC. Combined polymorphisms of TT (A-240T) and GG (A2350G) was significantly associated with decreased serum ACE activity (P=0.042) and decreased diastolic blood pressure (P=0.040). The angiotensin II receptor type 1 A1166C polymorphism (CC genotype) showed a significant association with declined diastolic blood pressure (P=0.028). Serum ACE activity was significantly higher in men compared to women (P=0.033). ACE activity also showed a direct association with diastolic blood pressure (P<0.001). No association was obtained among each single polymorphism with body mass index (BMI), fasting blood sugar (FBS), lipid profile and ACE activity. In conclusion, combined polymorphisms of A-240T and A2350G seem to affect serum ACE level as well as diastolic blood pressure in our study population. However, it also might be hypothesized that they are in strong linkage disequilibrium with other functional mutations not studied yet. Our findings revealed that gene interactions can play an important role in various biological conditions.

Impact of polymorphisms in the renin–angiotensin–aldosterone system on hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous autosomal dominant heart disease characterised by left ventricular hypertrophy in the absence of another cardiac or systemic disease that is capable of producing significant wall thickening. Microscopically it is characterised by cardiomyocyte hypertrophy, myofibrillar disarray and fibrosis. The phenotypic expression of HCM is multifactorial, with the majority of cases occurring secondary to mutations in genes encoding the sarcomere proteins. In conjunction with the genetic heterogeneity of HCM, phenotypic expression also exhibits a high level of variability even within families with the same aetiological mutation, and may be influenced by additional genetic factors. Polymorphisms of the renin–angiotensin–aldosterone system (RAAS) represent an attractive hypothesis as potential disease modifiers, as these genetic variants alter the ‘activation status’ of the RAAS, which leads to more left ventricular hypertrophy through different pathways. The main objective of this review is to provide an overview of the role of different polymorphisms identified in the RAAS, in patients with HCM.

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.

Rescue of familial cardiomyopathies by modifications at the level of sarcomere and Ca2+ fluxes

Cardiomyopathies are a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that frequently show inappropriate ventricular hypertrophy or dilation. Current data suggest that numerous mutations in several genes can cause cardiomyopathies, and the severity of their phenotypes is also influenced by modifier genes. Two major types of inherited cardiomyopathies include familial hypertrophic cardiomyopathy (FHC) and dilated cardiomyopathy (DCM). FHC typically involves increased myofilament Ca(2+) sensitivity associated with diastolic dysfunction, whereas DCM often results in decreased myofilament Ca(2+) sensitivity and systolic dysfunction. Besides alterations in myofilament Ca(2+) sensitivity, alterations in the levels of Ca(2+)-handling proteins have also been described in both diseases. Recent work in animal models has attempted to rescue FHC and DCM via modifications at the myofilament level, altering Ca(2+) homeostasis by targeting Ca(2+)-handling proteins, such as the sarcoplasmic reticulum ATPase and phospholamban, or by interfering with the products of different modifiers genes. Although attempts to rescue cardiomyopathies in animal models have shown great promise, further studies are needed to validate these strategies in order to provide more effective and specific treatments.

Histologic characterization of hypertrophic cardiomyopathy with and without myofilament mutations

BACKGROUND

Between 30% and 60% of clinical cases of hypertrophic cardiomyopathy (HC) can be attributed to mutations in the genes encoding cardiac myofilament proteins. Interestingly, it appears that the likelihood of an underlying myofilament mutation can be predicted by echocardiographic assessment of left ventricular morphology. However, it is not known whether genotypically characterized HC exists as a separate entity with discrete phenotypic morphology and histology or to what extent recognized polymorphisms of the renin-angiotensin-aldosterone system (RAAS) influence this relationship. The presence of cardiac myofilament and mutations and RAAS polymorphisms will have a strong association with the severity of histologic features of HC and characteristic septal shape.

METHODS

We conducted a retrospective review of histology specimens, obtained at septal myectomy among 181 patients with medically refractory symptomatic HC. All patients underwent comprehensive genetic analysis for mutations in 8 myofilament-encoding genes; a subset was genotyped for 6 known RAAS-polymorphisms. Patients underwent comprehensive echocardiography by an expert blinded to genotype and microscopic status.

RESULTS

Microscopically, severity of myocyte hypertrophy appears to be associated with the presence of recognized HC cardiac myofilament mutations (P = .03). Other histologic features characteristic of HC were not consistently associated with myofilament mutation status. A higher burden of pro-LVH RAAS polymorphisms also appeared to predict only myocyte hypertrophy (P = .01). The presence of RAAS polymorphisms was not associated with the development of a specific septal morphology (P = .6).

CONCLUSION

Myofilament-positive HC does not appear to represent a distinct clinical phenotypic entity as evidenced by specific histologic characteristics and septal shape.

Association of angiotensin-converting enzyme activity and polymorphism with echocardiographic measures in familial and nonfamilial hypertrophic cardiomyopathy

Angiotensin-converting enzyme (ACE) activity and polymorphism contribute significantly to the prognosis of patients with cardiomyopathy. The aim of this study was to determine the activity and type of ACE polymorphism in patients with familial and nonfamilial hypertrophic cardiomyopathy (HCM) and to correlate these with echocardiographic measurements (echo-Doppler). We studied 136 patients (76 males) with HCM (69 familial and 67 nonfamilial cases). Mean age was 41 +/- 17 years. DNA was extracted from blood samples for the polymerase chain reaction and the determination of plasma ACE levels. Left ventricular mass, interventricular septum, and wall thickness were measured. Mean left ventricular mass index, interventricular septum and wall thickness in familial and nonfamilial forms were 154 +/- 63 and 174 +/- 57 g/m(2) (P = 0.008), 19 +/- 5 and 21 +/- 5 mm (P = 0.02), and 10 +/- 2 and 12 +/- 3 mm (P = 0.0001), respectively. ACE genotype frequencies were DD = 35%, ID = 52%, and II = 13%. A positive association was observed between serum ACE activity and left ventricular mass index (P = 0.04). Logistic regression showed that ACE activity was twice as high in patients with familial HCM and left ventricular mass index >or=190 g/m(2) compared with the nonfamilial form (P = 0.02). No other correlation was observed between ACE polymorphisms and the degree of myocardial hypertrophy. In conclusion, ACE activity, but not ACE polymorphisms, was associated with the degree of myocardial hypertrophy in the patients with HCM.

Gene-specific modifying effects of pro-LVH polymorphisms involving the renin-angiotensin-aldosterone system among 389 unrelated patients with hypertrophic cardiomyopathy

AIMS

The purpose of this study was to determine whether the deletion/insertion (D/I) polymorphism in the ACE-encoded angiotensin-converting enzyme or the pooled gene effect of five renin-angiotensin-aldosterone system (RAAS) polymorphisms were disease modifiers in a large cohort of unrelated patients with genotyped hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Five different RAAS polymorphism genotypes were established by PCR amplification of the surrounding polymorphic regions of genomic DNA in a cohort of 389 unrelated patients comprehensively genotyped for HCM-causing mutations in eight sarcomeric/myofilament genes. Patient clinical data were archived in a database blinded both to the primary myofilament defect and the polymorphism genotype. Each patient was assessed with respect to ACE genotype as well as composite pro-left ventricular hypertrophy (LVH) RAAS polymorphism score (0-5). Overall, no clinical parameter correlated independently with ACE genotype. Subset analysis of the two most common genetic subtypes of HCM, MYBPC3 (myosin binding protein C) and MYH7 (beta myosin heavy chain), demonstrated a significant pro-LVH effect of DD-ACE only in patients with MYBPC3-HCM. In MYBPC3-HCM, left ventricular wall thickness was greater in patients with DD genotype (25.8+/-5 mm) compared with DI (21.8+/-4) or II genotype (20.8+/-5, P=0.01). Moreover, extreme hypertrophy (>30 mm) was only seen in MYBPC3-HCM patients who also hosted DD-ACE. An effect of RAAS pro-LVH score was evident only in the subgroup of patients with no previously identified myofilament mutation.

CONCLUSION

This study demonstrates that RAAS genotypes may modify the clinical phenotype of HCM in a disease gene-specific fashion rather than indiscriminately.

Single nucleotide polymorphisms predict the change in left ventricular mass in response to antihypertensive treatment

BACKGROUND

Our aim was to determine whether the change in left ventricular (LV) mass in response to antihypertensive treatment could be predicted by multivariate analysis of single nucleotide polymorphisms (SNPs) in candidate genes reflecting pathways likely to be involved in blood pressure control.

METHODS

Patients with mild to moderate primary hypertension and LV hypertrophy were randomized in a double-blind fashion to treatment with either the angiotensin II type 1 receptor antagonist irbesartan (n = 48) or the beta1 adrenoreceptor blocker atenolol (n = 49). A microarray-based minisequencing system was used for genotyping 74 SNPs in 25 genes. These genotypes were related to the change in LV mass index by echocardiography, after 12 weeks treatment as monotherapy, using stepwise multiple regression analysis.

RESULTS

The blood pressure reductions were similar and significant in both treatment groups. Two SNPs in two separate genes (the angiotensinogen T1198C polymorphism, corresponding to the M235T variant and the apolipoprotein B G10108A polymorphism) for those treated with irbesartan, and the adrenoreceptor alpha2A A1817G for those treated with atenolol, significantly predicted the change in LV mass. The predictive power of these SNPs was independent of the degree of blood pressure reduction.

CONCLUSION

SNPs in the angiotensinogen, apolipoprotein B, and the alpha2 adrenoreceptor gene predicted the change in LV mass during antihypertensive therapy. These results illustrate the potential of using microarray-based technology for SNP genotyping in predicting individual drug responses.

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.

Progression of left ventricular hypertrophy and the angiotensin-converting enzyme gene polymorphism in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy is an inherited primary disorder of the myocardium characterised by clinical heterogeneity. The severity and rate of progression of hypertrophy is an important factor in prognosis, and is likely to be dependent on factors including age, the disease-causing gene mutation, environmental influences and genetic modifiers.

METHODS

To study the influence of age on progression of hypertrophy, 62 patients with hypertrophic cardiomyopathy followed up for a minimum of 2 years were studied to determine the changes in left ventricular hypertrophy based on transthoracic M-mode and 2D echocardiography. DNA studies were performed to determine the role of the angiotensin-converting enzyme (ACE) gene deletion polymorphism in modulating progression of left ventricular hypertrophy.

RESULTS

Sixty-two patients were followed-up over a period of 6.0 +/- 3.2 years (range 2-16 years). Patient data were analysed in two age groups: group 1 (patients aged < or = 30 years at first echocardiogram) had an increase in left ventricular septal wall thickness from 23.8 +/- 8.9 to 28.8 +/- 8.7 mm (p < 0.001), while group 2 (patients aged > 30 years) had a smaller but significant increase from 17.8 +/- 4.2 to 19.5 +/- 6.2 mm (p < 0.05). DNA analysis of the ACE gene deletion polymorphism showed those with the deletion/deletion (D/D) genotype had a greater progression of left ventricular hypertrophy compared to those carrying the other ACE genotypes (increase in hypertrophy: 6.2 +/- 3.3 vs. 1.7 +/- 4.2 mm; p < 0.01, D/D vs. I/D genotype; 2.8 +/- 5.8 mm; p = ns, D/D vs. I/I genotype). This association was independent of age, body mass and resting blood pressure.

CONCLUSIONS

Progression of left ventricular hypertrophy is most evident in the first 3 decades of life, but is also observed in older age groups. Presence of the ACE gene D/D polymorphism may be an important marker to identify those individuals with hypertrophic cardiomyopathy who are likely to have more progressive disease, and therefore at higher risk of adverse clinical outcomes.

Polymorphisms in the angiotensinogen and angiotensin II type 1 receptor gene are related to change in left ventricular mass during antihypertensive treatment: results from the Swedish Irbesartan Left Ventricular Hypertrophy Investigation versus Atenolol (SILVHIA) trial

BACKGROUND

Our aim was to determine if gene polymorphisms in the renin-angiotensin-aldosterone system (RAAS) were related to the degree of change in left ventricular hypertrophy (LVH) during antihypertensive treatment.

METHODS AND RESULTS

Patients with essential hypertension and echocardiographically diagnosed LVH were included in a double-blind study to receive treatment with either the angiotensin II type 1 receptor (AT1-receptor) antagonist irbesartan (n = 41), or the beta-1 adrenergic receptor blocker atenolol (n = 43) as monotherapy for 3 months. The angiotensinogen T174M and M235T, the angiotensin-converting enzyme I/D, the AT1-receptor A1166C and the aldosterone synthase (CYP11B2) -344 C/T polymorphisms were analysed and related to the change in left ventricular mass (LVM). Patients with the angiotensinogen 174 TM genotype treated with irbesartan responded with the greatest reduction in LVM (-23 +/- 31SD g/m2 for TM and +0.5 +/- 18 g/m2 for TT, P = 0.005), independent of blood pressure reduction. Both the angiotensinogen 235 T-allele (P = 0.02) and the AT1-receptor 1166 AC genotype responded with the greatest reduction in LVM when treated with irbesartan (-0.1 +/- 19 g/m2 for AA and -18 +/- 30 g/m2 for AC, P = 0.02), independent of blood pressure reduction. These polymorphisms were not associated with the change in LVM during treatment with atenolol.

DISCUSSION

The angiotensinogen T174M and M235T and the AT1-receptor A1166C polymorphisms were related to the change in LVH during antihypertensive treatment with an AT1-receptor antagonist; of these angiotensinogen T174M was the most powerful. This highlights the role of the RAAS for left ventricular hypertrophy and the potential of pharmacogenetics as a tool for guidance of antihypertensive therapy.

Genetic polymorphisms in the renin-angiotensin-aldosterone system associated with expression of left ventricular hypertrophy in hypertrophic cardiomyopathy: a study of five polymorphic genes in a family with a disease causing mutation in the myosin binding protein C gene

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is an inherited disease of the sarcomere characterised clinically by myocardial hypertrophy and its consequences. Phenotypic expression is heterogeneous even within families with the same aetiological mutation and may be influenced by additional genetic factors.

OBJECTIVE

To determine the influence of genetic polymorphisms of the renin-angiotensin-aldosterone system (RAAS) on ECG and two dimensional echocardiographic left ventricular hypertrophy (LVH) in genetically identical patients with HCM.

PATIENTS AND METHODS

Polymorphisms of five RAAS components were determined in 26 gene carriers from a single family with HCM caused by a previously identified myosin binding protein C mutation. Genotypes associated with a higher activation status of the RAAS were labelled "pro-LVH genotypes".

RESULTS

There was a non-biased distribution of pro-LVH genotypes in the gene carriers. Those without pro-LVH genotypes did not manifest cardiac hypertrophy whereas gene carriers with pro-LVH genotypes did (mean (SD) left ventricular muscle mass 190 (48) v 320 (113), p = 0.002; interventricular septal thickness 11.5 (2.0) v 16.4 (6.7), p = 0.01; pathological ECG 0% (0 of 10) v 63% (10 of 16), respectively). Multivariate analysis controlling for age, sex, and hypertension confirmed an independent association between the presence of pro-LVH polymorphisms and left ventricular mass. When each polymorphism was assessed individually, carriers of each pro-LVH genotype had a significantly greater left ventricular mass than those with no pro-LVH mutation; these associations, with the exception of cardiac chymase A AA polymorphism (p = 0.06), remained significant in multivariate analysis.

CONCLUSION

Genetic polymorphisms of the RAAS influence penetrance and degree of LVH in 26 gene carriers from one family with HCM caused by a myosin binding protein C mutation.

From the sarcomere to the nucleus: role of genetics and signaling in structural heart disease

The identification of genetic mutations underlying familial structural heart disease has provided exciting new insights into how alterations in structural components of the cardiomyocyte lead to different forms of cardiomyopathy. Specifically, mutations in components of the sarcomere are frequently associated with hypertrophic cardiomyopathy, whereas mutations in cytoskeletal proteins lead to dilated cardiomyopathy. In addition, extrinsic stresses such as hypertension and valvular disease can produce myocardial remodeling that is very similar to that observed in genetic cardiomyopathy. For myocardial remodeling to occur, changes in gene expression must occur; therefore, changes in contractile function or wall stress must be communicated to the nucleus via signal transduction pathways. The identity of these signaling pathways has become a key question in molecular biology. Numerous signaling molecules have been implicated in the development of hypertrophy and failure, including the beta-adrenergic receptor, G alpha(q) and downstream effectors, mitogen-activated protein kinase pathways, and the Ca(2+)-regulated phosphatase, calcineurin. In the past it has been difficult to discern which signaling molecules actually contributed to disease progression in vivo; however, the development of numerous transgenic and knockout mouse models of cardiomyopathy is now allowing the direct testing of stimulatory and inhibitory molecules in the mouse heart. From this work it has been possible to identify signaling molecules and pathways that are required for different aspects of disease progression in vivo. In particular, a number of signaling pathways have now been identified that may be key regulators of changes in myocardial structure and function in response to mutations in structural components of the cardiomyocyte. Myocardial structure and signal transduction are now merging into a common field of research that will lead to a more complete understanding of the molecular mechanisms that underly heart disease.

Angiotensin II type 2 receptors and cardiac hypertrophy in women with hypertrophic cardiomyopathy

The development of left ventricular hypertrophy in subjects with hypertrophic cardiomyopathy (HCM) is variable, suggesting a role for modifying factors such as angiotensin II. Angiotensin II mediates both trophic and antitrophic effects, via angiotensin II type 1 (AT(1)-R) and angiotensin II type 2 (AT(2)-R) receptors, respectively. Here we investigated the effect of the AT(2)-R gene A/C(3123) polymorphism, located in the 3' untranslated region of exon 3, on left ventricular mass index (LVMI) in 103 genetically independent subjects with HCM (age, 12 to 81 years). LVMI and interventricular septum thickness were determined by 2D echocardiography. Extent of hypertrophy was quantified by a point score (Wigle score). Plasma prorenin, renin, and ACE were determined by immunoradiometric or fluorometric assays, and genotyping was performed by polymerase chain reaction. In men, no associations between AT(2)-R genotype and any of the measured parameters were observed, whereas in women, LVMI decreased with the number of C alleles (211+/-19, 201+/-18, and 152+/-10 g/m(2) in women with the AA, AC, and CC genotype, respectively; P=0.015). Similar C allele-related decreases in women were observed for interventricular septum thickness (P=0.13), Wigle score (P=0.05), plasma renin (P=0.03), and plasma prorenin (P=0.26). Multiple regression analysis revealed that the AT(2)-R C allele-related effect on LVMI (beta=-30.7+/-11.1, P=0.010) occurred independently of plasma renin, the AT(1)-R gene A/C(1166) polymorphism, or the ACE gene I/D polymorphism. In conclusion, AT(2)-Rs modulate cardiac hypertrophy in women with HCM, independently of the circulating renin-angiotensin system. These data support the contention that AT(2)-Rs mediate antitrophic effects in humans.

Cardiomyopathies: from genetics to the prospect of treatment

Cardiomyopathies are defined as diseases of the myocardium associated with cardiac dysfunction ranging from lifelong symptomless forms to major health problems such as progressive heart failure, arrhythmia, thromboembolism, and sudden cardiac death. They are classified by morphological characteristics as hypertrophic (HCM), dilated (DCM), arrhythmogenic right ventricular (ARVC), and restrictive cardiomyopathy (RCM). A familial cause has been shown in 50% of patients with HCM, 35% with DCM, and 30% with ARVC. In HCM, nine genetic loci and more than 130 mutations in ten different sarcomeric genes and in the gamma 2 subunit of AMP-activated protein kinase (AMPK) have been identified, suggesting impaired force production associated with inefficient use of ATP as the crucial disease mechanism. In DCM, 16 chromosomal loci with defects of several proteins also involved in the development of skeletal myopathies have been detected. These mutated cytoskeletal and nuclear transporter proteins may alter force transmission or disrupt nuclear function, resulting in cell death. Further DCM mutations have also been identified in sarcomeric genes, which indicates that different defects of the same protein can result in either HCM or DCM. In ARVC, six genetic loci and mutations in the cardiac ryanodine receptor, which controls electromechanical coupling, and in plakoglobin and desmoglobin (molecules involved in desmosomal cell-junction integrity), have been identified. Yet, no genetic linkage has been shown in RCM. Apart from disease-causing mutations, other factors, such as environment, genetic background, and the recently identified modifier genes of the renin-angiotensin, adrenergic, and endothelin systems are likely to result in the wide variety of RCM clinical presentations. Treatment options are symptomatic and are mainly focused on treatment of heart failure and prevention of thromboembolism and sudden death. Identification of patients with high risk for major arrhythmic events is important because implantable cardioverter defibrillators can prevent sudden death. Clinical and genetic risk stratification may lead to prospective trials of primary implantation of cardioverter defibrillators in people with hereditary cardiomyopathy.

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 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.

[Sudden death (V). Identification and treatment of patients with hypertrophic cardiomyopathy at risk of sudden death]

During the last 20 years, the principal objective in hypertrophic cardiomyopathy research has been the refinement of algorithms for the identification and treatment of patients at risk of sudden death. Sudden death is an important problem in hypertrophic cardiomyopathy, with an incidence of 4-6% in referral populations and approximately 1% in non-referral centers and because it affects young and often asymptomatic patients. We now know that hypertrophic cardiomyopathy is not a single disease, but a group of diseases caused by mutations in genes encoding different sarcomeric proteins. The phenotypic expression depends on multiple modifying genetic and environmental factors. Even though genetic testing is not presently a practical approach in hypertrophic cardiomyopathy risk stratification, it is important to consider new genetic data in the prognostic evaluation of patients. In this paper, we review the published data on risk stratification in hypertrophic cardiomyopathy and we set forth our opinion with regard to the available therapeutic options and their indications in the prevention of sudden death.

Familial dilated cardiomyopathy: evidence for genetic and phenotypic heterogeneity. Heart Muscle Disease Study Group

OBJECTIVES

This study was performed to evaluate the characteristics, mode of inheritance and etiology of familial dilated cardiomyopathy (FDC).

BACKGROUND

A genetic form of disease transmission has been identified in a relevant proportion of patients with dilated cardiomyopathy (DCM). Variable clinical characteristics and patterns of inheritance, and an increased frequency of cardiac antibodies have been reported. An analysis of FDC may improve the understanding of the disease and the management of patients.

METHODS

Of 350 consecutive patients with idiopathic DCM, 281 relatives from 60 families were examined. Family studies included clinical examination, electrocardiography, echocardiography and blood sampling. Of the 60 DCM index patients examined, 39 were attributable to FDC and 21 were due to sporadic DCM. Clinical features, histology, mode of inheritance and autoimmune serology were examined, molecular genetic studies were undertaken and the difference between familial and sporadic forms was analyzed.

RESULTS

Only a younger age (p = 0.0005) and a higher ejection fraction (p = 0.03) could clinically distinguish FDC patients from those with sporadic DCM. However, a number of distinct subtypes of FDC were identified: 1) autosomal dominant, the most frequent form (56%); 2) autosomal recessive (16%), characterized by worse prognosis; 3) X-linked FDC (10%), with different mutations of the dystrophin gene; 4) a novel form of autosomal dominant DCM with subclinical skeletal muscle disease (7.7%); 5) FDC with conduction defects (2.6%), and 6) rare unclassifiable forms (7.7%). The forms with skeletal muscle involvement were characterized by a restrictive filling pattern; the forms with isolated cardiomyopathy had an increased frequency of organ-specific cardiac autoantibodies. Histologic signs of myocarditis were frequent and nonspecific.

CONCLUSIONS

Familial dilated cardiomyopathy is frequent, cannot be predicted on a clinical or morphologic basis and requires family screening for identification. The phenotypic heterogeneity, different patterns of transmission, different frequencies of cardiac autoantibodies and the initial molecular genetic data indicate that multiple genes and pathogenetic mechanisms can lead to FDC.

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.

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.