RAAS gene polymorphisms influence progression of pediatric hypertrophic cardiomyopathy

Percutaneous cutting balloon angioplasty for the treatment of renovascular hypertension in children and adolescents

OBJECTIVE

Percutaneous transluminal renal angioplasty (PTRA), the recommended treatment in children with renovascular hypertension (RVH), often has unsatisfactory outcomes. Cutting balloons may improve the results of angioplasty in different vascular beds with complex and resistant lesions. We retrospectively analysed the effects of percutaneous cutting balloon angioplasty (PCBA) on blood pressure, cardiac mass and renal artery acceleration time in children/adolescents referred to our centre for RVH.

PATIENTS AND METHODS

Thirteen patients (aged 9-19 years) with renal artery stenosis (RAS) and severe hypertension were identified. RASs were focal fibromuscular (FMD) or FMD-like dysplasia (in six cases bilateral, in five associated with mid aortic syndrome). Ten patients had uncontrolled hypertension, in nine cases associated with left ventricular hypertrophy (LVH). Acceleration time was abnormal in all stenotic arteries. Eighteen PCBA were performed, in three arteries associated with stent implantation.

RESULTS

PCBA was technically successful in all individuals without major complications. In one patient, an intra-stent restenosis occurred, successfully redilated with conventional angioplasty without recurrence at 4 years distance. One year after PCBA, mean SBP and DBPs were markedly reduced from 146 ± 25 to 121 ± 10 mmHg and from 87 ± 11 to 65 ± 12 mmHg, respectively (P < 0.001 for both). At that time, hypertension was cured in seven children and controlled in five individuals. This favourable outcome was confirmed with ambulatory blood pressure measurement in four patients. At the latest follow-up, left ventricular mass and acceleration time were normal in all patients.

CONCLUSION

PCBA proved to be a well tolerated and effective procedure that can be considered as an alternative to PTRA to treat hypertensive children/adolescents with recurrent or resistant RAS.

Effect of rs4646994 polymorphism of angiotensin converting enzyme on the risk of nonischemic cardiomyopathy

Background: Angiotensin-converting enzyme (ACE) gene polymorphisms have recently been shown to be associated with risk of developing left ventricular hypertrophy (LVH). However, the results were controversial. We aimed to conduct this meta-analysis to further confirm the association between ACE rs4646994 polymorphism and hypertrophic cardiomyopathy (HCM)/dilated cardiomyopathy (DCM).

Methods: PubMed, Embase, the Chinese National Knowledge Information, and Wanfang databases were searched for eligible studies. The Newcastle–Ottawa Scale (NOS) was used to evaluate the quality of included studies. Then we evaluated the association between ACE gene mutation and HCM/DCM by calculating odds ratios (ORs) and 95% confidence intervals (95% CIs). Subgroup analysis was further performed to explore situations in specialized subjects. Sensitivity analysis and publication bias was assessed to confirm the study reliability.

Results: There were 13 studies on DCM (2004 cases and 1376 controls) and 16 studies on HCM (2161 controls and 1192 patients). ACE rs4646994 polymorphism was significantly associated with DCM in all genetic models. However, in HCM, four genetic models (allele model, homozygous model, heterozygous model, and dominant model) showed significant association between ACE rs4646994 polymorphism and DCM. In subgroup analysis, we found that ACE rs4646994 polymorphism was significantly associated with DCM/HCM in Asian population. Finally, we also conducted a cumulative meta-analysis, which indicates that the results of our meta-analysis are highly reliable.

Conclusion: ACE rs4646994 polymorphism increases the risk of DCM/HCM in Asians, but not in Caucasians. More case–control studies are needed to strengthen our conclusions and to assess the gene–gene and gene–environment interactions between ACE rs4646994 polymorphism and DCM/HCM.

Newer risk assessment strategies in hypertrophic cardiomyopathy

PURPOSE OF REVIEW

The present article serves to review current risk assessment guidelines for sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM) and to discuss how these guidelines can be applied to patients with childhood HCM. New diagnostic techniques that could lead to more accurate risk assessment tools are also discussed.

RECENT FINDINGS

Current guidelines for risk assessment in childhood HCM are extrapolated from adult guidelines and lack background research to validate their use. Continuous variables, such as wall thickness, are converted to binary variables, which is particularly concerning in pediatric patients' where weight gain and linear growth is likely to lead to more significant hemodynamic changes in shorter periods of time. Some studies have even shown that risk factors concerning in adults may actually be protective in pediatric patients. Additionally, large gaps still remain between genotype and phenotype expression in HCM.

SUMMARY

A better understanding of the relationship between cause, phenotype, and outcomes is needed to truly be able to determine risk for SCD in childhood HCM. Larger studies, including newer technologies and quantitative models, similar to the European HCM Risk-SCD model, which allows for a quantitative risk diagnosis, are needed as well.

Exome sequencing identifies a FHOD3 p.S527del mutation in a Chinese family with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disease and is characterised by unexplained ventricular myocardial hypertrophy. HCM is highly heterogeneous and is primarily caused by the mutation of genes encoding sarcomere proteins. As a result of its genetic basis, we investigated the underlying cause of HCM in a Chinese family by whole-exome sequencing.

METHODS

Whole-exome sequencing was performed for seven clinically diagnosed HCM family members and the resulting single nucleotide variants associated with cardiac hypertrophy or heart development were analysed by a polymerase chain reaction and Sanger sequencing.

RESULTS

A non-frameshift deletion mutation (p.S527del) of Formin Homology 2 Domain Containing 3 (FHOD3) was detected in all of the affected family members and was absent in all unaffected members, with the exception of one young member. Moreover, three single nucleotide variants associated with heart development and morphogenesis were identified in the proband but were absent in the other affected subjects.

CONCLUSIONS

This is the first HCM family case of FHOD3 (p.S527del) variation in Asia. Additionally, RNF207 (p.Q268P), CCM2 (p. E233K) and SGCZ (p.Q134X) may be related to the clinical heterogeneity of the family. The present study could enable the provision of genetic counseling for this family and provide a basis for future genetic and functional studies.

The genetics of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is most commonly transmitted as an autosomal dominant trait, caused by mutations in genes encoding cardiac sarcomere proteins^1–3. Other inheritable causes of the disease include mutations in genes coding for proteins important in calcium handling or that form part of the cytoskeleton^4–6. At present, the primary clinical role of genetic testing in HCM is to facilitate familial screening to allow the identification of individuals at risk of developing the disease^7,8. It is also used to diagnose genocopies, such as lysosomal^9–11 and glycogen storage disease which have different treatment strategies, rates of disease progression and prognosis^12–14. The role of genetic testing in predicting prognosis is limited at present, but emerging data suggest that knowledge of the genetic basis of disease will assume an important role in disease stratification^15–17 and offer potential targets for disease-modifying therapy in the near future¹⁸.

Hypertrophic Cardiomyopathy: Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder that is characterized by left ventricular hypertrophy unexplained by secondary causes and a nondilated left ventricle with preserved or increased ejection fraction. It is commonly asymmetrical with the most severe hypertrophy involving the basal interventricular septum. Left ventricular outflow tract obstruction is present at rest in about one third of the patients and can be provoked in another third. The histological features of HCM include myocyte hypertrophy and disarray, as well as interstitial fibrosis. The hypertrophy is also frequently associated with left ventricular diastolic dysfunction. In the majority of patients, HCM has a relatively benign course. However, HCM is also an important cause of sudden cardiac death, particularly in adolescents and young adults. Nonsustained ventricular tachycardia, syncope, a family history of sudden cardiac death, and severe cardiac hypertrophy are major risk factors for sudden cardiac death. This complication can usually be averted by implantation of a cardioverter-defibrillator in appropriate high-risk patients. Atrial fibrillation is also a common complication and is not well tolerated. Mutations in over a dozen genes encoding sarcomere-associated proteins cause HCM. MYH7 and MYBPC3, encoding β-myosin heavy chain and myosin-binding protein C, respectively, are the 2 most common genes involved, together accounting for ≈50% of the HCM families. In ≈40% of HCM patients, the causal genes remain to be identified. Mutations in genes responsible for storage diseases also cause a phenotype resembling HCM (genocopy or phenocopy). The routine applications of genetic testing and preclinical identification of family members represents an important advance. The genetic discoveries have enhanced understanding of the molecular pathogenesis of HCM and have stimulated efforts designed to identify new therapeutic agents.

Adrenergic receptor genotypes influence postoperative outcomes in infants in the Single-Ventricle Reconstruction Trial

OBJECTIVES

Adrenergic receptor (ADR) genotypes have been associated with adverse outcomes in heart failure. Our objective was to evaluate the association of ADR genotypes with post-Norwood outcomes in infants with hypoplastic left heart syndrome (HLHS).

METHODS

Infants with HLHS participating in the Pediatric Heart Network Single-Ventricle Reconstruction Trial underwent genotyping for 4 single-nucleotide polymorphisms in 3 ADR genes: ADRB1_231A/G, ADRB1_1165G/C, ADRB2_5318C/G, and ADRA2A_2790C/T. The association of genotype with freedom from serious adverse events (SAEs) (death, transplant, extracorporeal membrane oxygenation, cardiopulmonary resuscitation, acute shunt failure, unplanned reoperations, or necrotizing enterocolitis) during 14 months' follow-up was assessed with Cox regression and the association with post-Norwood complications was assessed with Poisson regression. Models were adjusted for clinical and surgical factors.

RESULTS

The study included 351 eligible patients (62% male; 83% white). The mean age at Norwood procedure was 5.6 ± 3.6 days. A total of 152 patients had SAEs during 14-month follow-up including 84 deaths and 10 transplants. ADRA2A_2790CC genotype had lower SAE-free survival compared with CT/TT genotypes during follow-up (Log rank test, P = .02), and this association was independent of clinical and surgical risk factors (adjusted Cox regression, hazard ratio 1.54 [95% confidence interval 1.04, 2.30] P = .033). Post-Norwood complication rate did not differ by genotype.

CONCLUSIONS

Infants with HLHS harboring ADR genotypes that are associated with greater catecholamine release or sensitivity had lower event-free survival after staged palliation. Excess catecholamine activation may adversely affect cardiovascular adaptation after the Norwood procedure. Future studies should explore whether targeting adrenergic activation in those harboring risk genotypes can improve outcomes. (ClinicalTrials.gov number NCT00115934).

Update on hypertrophic cardiomyopathy and a guide to the guidelines

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder, affecting 1 in 500 individuals worldwide. Existing epidemiological studies might have underestimated the prevalence of HCM, however, owing to limited inclusion of individuals with early, incomplete phenotypic expression. Clinical manifestations of HCM include diastolic dysfunction, left ventricular outflow tract obstruction, ischaemia, atrial fibrillation, abnormal vascular responses and, in 5% of patients, progression to a 'burnt-out' phase characterized by systolic impairment. Disease-related mortality is most often attributable to sudden cardiac death, heart failure, and embolic stroke. The majority of individuals with HCM, however, have normal or near-normal life expectancy, owing in part to contemporary management strategies including family screening, risk stratification, thromboembolic prophylaxis, and implantation of cardioverter-defibrillators. The clinical guidelines for HCM issued by the ACC Foundation/AHA and the ESC facilitate evaluation and management of the disease. In this Review, we aim to assist clinicians in navigating the guidelines by highlighting important updates, current gaps in knowledge, differences in the recommendations, and challenges in implementing them, including aids and pitfalls in clinical and pathological evaluation. We also discuss the advances in genetics, imaging, and molecular research that will underpin future developments in diagnosis and therapy for HCM.

Contribution of Post-translational Phosphorylation to Sarcomere-Linked Cardiomyopathy Phenotypes

Secondary shifts develop in post-translational phosphorylation of sarcomeric proteins in multiple animal models of inherited cardiomyopathy. These signaling alterations together with the primary mutation are predicted to contribute to the overall cardiac phenotype. As a result, identification and integration of post-translational myofilament signaling responses are identified as priorities for gaining insights into sarcomeric cardiomyopathies. However, significant questions remain about the nature and contribution of post-translational phosphorylation to structural remodeling and cardiac dysfunction in animal models and human patients. This perspective essay discusses specific goals for filling critical gaps about post-translational signaling in response to these inherited mutations, especially within sarcomeric proteins. The discussion focuses primarily on pre-clinical analysis of animal models and defines challenges and future directions in this field.

Involvement of the -420C>G RETN polymorphism in myocardial fibrosis in patients with hypertrophic cardiomyopathy

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and fibrosis. HCM is an autosomal-dominant disease caused by more than 400 mutations in sarcomeric genes. Changes in nonsarcomeric genes contribute to its phenotypic heterogeneity. Cardiac fibrosis can be studied using late gadolinium enhancement (LGE) cardiac magnetic resonance imaging. We evaluated the potential role of two polymorphisms in nonsarcomeric genes on interstitial fibrosis in HCM.

MATERIALS AND METHODS

Two polymorphisms in nonsarcomeric genes [ACE (deletion of 287 bp in the 16th intron) and RETN (-420C>G)] were analysed in 146 HCM patients. Cardiac fibrosis was assessed using LGE to determine the number of affected segments.

RESULTS

Allelic frequencies in ACE and RETN polymorphisms were consistent with the Hardy-Weinberg equilibrium (both P > 0.05). We found that the presence of the polymorphic allele in the -420C>G RETN polymorphism was independently associated with the number of affected segments of LGE (P = 0.038). Increased circulating resistin concentration, measured by enzyme-linked immunosorbent assay, was associated with a higher degree of cardiac fibrosis. Myocardial fibrosis, assessed by Masson's trichrome staining, was associated with the -420C>G RETN polymorphism in 46 tissue samples obtained by septal myectomy (P = 0.044).

CONCLUSIONS

The -420C>G RETN polymorphism was independently associated with the degree of cardiac fibrosis, assessed by LGE, in patients with HCM. In addition, there was an association between the polymorphism and the circulating resistin levels as well as with myocardial fibrosis in tissues obtained by myectomy. Investigating the physiological implication of the RETN polymorphism in HCM in combination with the use of imaging technologies might help to establish the severity of disease in patients with HCM.

Prognostic value of two polymorphisms in non-sarcomeric genes for the development of atrial fibrillation in patients with hypertrophic cardiomyopathy

BACKGROUND

Several non-sarcomeric genes have been postulated to act as modifiers in the phenotypic manifestations of hypertrophic cardiomyopathy (HCM). The development of atrial fibrillation (AF) in HCM has adverse prognostic implications with increased thromboembolism and functional class impairment.

AIM

We tested the hypothesis that 2 non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] are associated with the development of AF.

DESIGN

Prospective study.

METHODS

Two polymorphisms in non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] were analysed in 159 HCM patients (49.3 ± 14.9 years, 70.6% male) and 136 controls. All subjects were clinically stable and in sinus rhythm at entry in the study, without ischemic heart disease or other significant co-morbidities that could mask the effect of the analysed polymorphisms (i.e. previous AF). Thirty-nine patients (24.4%) developed AF during a median follow-up of 49.5 months.

RESULTS

Patients with the -344T>C polymorphism in CYP11B2 gene had a higher risk for AF development [HR: 3.31 (95% CI 1.29-8.50); P = 0.008]. In a multivariate analysis, the presence of the C allele in CYP11B2 gene [HR: 3.02 (1.01-8.99); P = 0.047], previous AF [HR: 2.81 (1.09-7.23); P = 0.033] and a left atrial diameter of ≥42 mm [HR: 2.69 (1.01-7.18); P = 0.048] were independent predictors of AF development. The presence of the polymorphic allele was associated with higher aldosterone serum levels.

CONCLUSION

We have shown for the first time that the CYP11B2 polymorphism is an independent predictor for AF development in HCM patients. This highlights the importance of non-sarcomeric genes in the phenotypic heterogeneity of HCM. The association with higher aldosterone serum levels could relate to greater fibrosis and cardiac remodelling.

Genetic biomarkers in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a common inherited heart muscle disorder associated with sudden cardiac death, arrhythmias and heart failure. Genetic mutations can be identified in approximately 60% of patients; these are commonest in genes that encode proteins of the cardiac sarcomere. Similar to other Mendelian diseases these mutations are characterized by incomplete penetrance and variable clinical expression. Our knowledge of this genetic diversity is rapidly evolving as high-throughput DNA sequencing technology is now used to characterize an individual patient's disease. In addition, the genomic basis of several multisystem diseases associated with a hypertrophic cardiomyopathy phenotype has been elucidated. Genetic biomarkers can be helpful in making an accurate diagnosis and in identifying relatives at risk of developing the condition. In the clinical setting, genetic testing and genetic screening should be used pragmatically with appropriate counseling. Here we review the current role of genetic biomarkers in hypertrophic cardiomyopathy, highlight recent progress in the field and discuss future challenges.

Impact of angiotensin I converting enzyme insertion/deletion polymorphisms on dilated cardiomyopathy and hypertrophic cardiomyopathy risk

Background

Genetic factors in the pathogenesis of cardiomyopathies have received a lot attention during the past two decades. Angiotensin I converting enzyme (ACE) insertion/deletion (I/D) polymorphisms were found to be associated with cardiomyopathies. However, the previous results were inconsistent. The current meta-analysis aims to examine the association of ACE I/D polymorphisms and dilated cardiomyopathy (DCM) or hypertrophic cardiomyopathy (HCM).

Methods

Eight studies on DCM (1387 controls and 977 patients) and eight studies on HCM (1055 controls and 827 patients) were included in this meta-analysis.

Results

The overall data showed no significant association between ACE I/D polymorphism and DCM risk. Further subgroup analysis by ethnicity also did not find a significantly increased risk for D allele carriers among East Asians and Europeans. However, the overall analysis suggested that the D allele carriers might be associated with increased risk of HCM (DD/ID vs. II: OR = 1.69, 95% CI 1.04–2.74, P = 0.03).

Conclusion

In summary, the meta-analysis indicated that certain ACE I/D polymorphism might be associated with HCM but not DCM susceptibility. Given the limited sample sizes, further large multicenter case-control investigation is needed.

Formin homology 2 domain containing 3 variants associated with hypertrophic cardiomyopathy

BACKGROUND

Incomplete penetrance and variable expression of hypertrophic cardiomyopathy (HCM) is well appreciated. Common genetic polymorphisms variants that may affect HCM penetrance and expression have been predicted but are not well established.

METHODS AND RESULTS

We performed a case-control genomewide association study to identify common HCM-associated genetic polymorphisms and then asked whether such common variants were more represented in HCM or could explain the heterogeneity of HCM phenotypes. We identified an intronic FHOD3 variant (rs516514) associated with HCM (odds ratio, 2.45; 95% confidence interval, 1.76-3.41; P=1.25×10(-7)) and validated this finding in an independent cohort. Next, we tested FHOD3-V1151I (rs2303510), a nonsynonymous variant in partial linkage disequilibrium with rs516514, and we detected an even stronger association with HCM (P=1.76×10(-9)). Although HCM patients were more likely to carry these, FHOD3 allele subjects homozygous for FHOD3-1151I had similar HCM phenotypes as carriers of the V1151 allele. FHOD3 expression is increased in the setting of HCM, and both alleles of FHOD3-V1151I were detected in HCM myectomy tissue. Previously, FHOD3 was found to be required for formation of the sarcomere, and here we demonstrate that its fly homolog fhos is required for normal adult heart systolic contraction.

CONCLUSIONS

Here we demonstrate the association of a common nonsynonymous FHOD3 genetic variant with HCM. This discovery further strengthens the potential role of gene mutations and polymorphisms that alter the amino acid sequence of sarcomere proteins and HCM.

Genetic variations in hypoxia response genes influence hypertrophic cardiomyopathy phenotype

BACKGROUND

Risk factors for diastolic dysfunction in hypertrophic cardiomyopathy (HCM) are poorly understood. We investigated the association of variants in hypoxia-response genes with phenotype severity in pediatric HCM.

METHODS

A total of 80 unrelated patients <21 y and 14 related members from eight families with HCM were genotyped for six variants associated with vascular endothelial growth factor A (VEGFA) downregulation, or hypoxia-inducible factor A (HIF1A) upregulation. Associations between risk genotypes and left-ventricular (LV) hypertrophy, LV dysfunction, and freedom from myectomy were assessed. Tissue expression was measured in myocardial samples from 17 patients with HCM and 20 patients without HCM.

RESULTS

Age at enrollment was 9 ± 5 y (follow-up, 3.1 ± 3.6 y). Risk allele frequency was 67% VEGFA and 92% HIF1A. Risk genotypes were associated with younger age at diagnosis (P < 0.001), septal hypertrophy (P < 0.01), prolonged E-wave deceleration time (EWDT) (P < 0.0001) and isovolumic relaxation time (IVRT) (P < 0.0001), and lower freedom from myectomy (P < 0.05). These associations were seen in sporadic and familial HCM independent of the disease-causing mutation. Risk genotypes were associated with higher myocardial HIF1A and transforming growth factor B1 (TGFB1) expression and increased endothelial-fibroblast transformation (P < 0.05).

CONCLUSION

HIF1A-upregulation and/or VEGFA-downregulation genotypes were associated with more severe septal hypertrophy and diastolic dysfunction and may provide genetic markers to improve risk prediction in HCM.

A polymorphic miR-155 binding site in AGTR1 is associated with cardiac hypertrophy in Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition with a heterogeneous cardiac phenotype caused primarily by an expanded GAA trinucleotide repeat in the frataxin gene (FXN). FXN is important in mitochondrial iron efflux, sensitivity to oxidative stress, and cell death. The number of GAA repeats on the smaller FXN allele (GAA1) only accounts for a portion of the observed variability in cardiac phenotype. Genetic modifying factors, such as single nucleotide polymorphisms (SNPs) in genes of the Renin-Angiotensin-Aldosterone system (RAAS), may contribute to phenotype variability. This study investigated genetic variability in the angiotensin-II type-1 receptor (AGTR1), angiotensin-converting enzyme (ACE), and ACE2 genes as cardiac phenotype modifying factors in FRDA patients. Comprehensive review of the AGTR1, ACE and ACE2 genes identified twelve haplotype tagging SNPs. Correlation of these SNPs with left ventricular internal diameter in diastole (LVIDd), interventricular septal wall thickness (SWT) and left ventricular mass (LVM) was examined in a large Australian FRDA cohort (n=79) with adjustments performed for GAA repeats, age, sex, body surface area and diastolic blood pressure. A significant inverse relationship was observed between GAA1 and LVIDd (p=0.010) but not with SWT or LVM after adjustment for covariates. The AGTR1 polymorphism rs5186 was more common in FRDA patients than in a control population (p=0.002). Using a recessive model of inheritance, the C allele of rs5186 was associated with a significant increase in SWT (p=0.003) and LVM (p=0.001). This functional polymorphism increases expression of AGTR1 by altering the binding site for miR-155, a regulatory microRNA. No significant associations with left ventricular structure were observed for the remaining RAAS polymorphisms. The AGTR1 polymorphism rs5186 appears to modify the FRDA cardiac phenotype independently of GAA1. This study supports the role of RAAS polymorphisms as modifiers of cardiac phenotype in FRDA patients.

[Advances in the molecular pathogenesis of hypertrophic cardiomyopathy]

Hypertrophic Cardiomyopathy (HCM) is a primary cardiac disorder characterized by asymmetric thickening of the septum and left ventricular wall. HCM affects 1 in 500 individuals in the general population, and it is the most common cause of sudden death in the young and athletes. The clinic phenotype of HCM is highly variable with respect to age at onset, degree of symptoms, and risk of sudden death. HCM is usually inherited as a Mendelian autosomal dominant trait. To date, over 900 mutations have been reported in HCM, which were mainly located in 13 genes encoding cardiac sarcomere protein, e.g., MYH7, MYBPC3, and TnT. In addition, more and more mitochondrial DNA mutations were reported to be associated with the pathogenesis of HCM. Based on the description of the clinical phenotype and morphological characteristics, this review focuses on the research in the molecular pathogenic mechanism of HCM and its recent advances.

Renin-angiotensin-aldosterone genotype influences ventricular remodeling in infants with single ventricle

BACKGROUND

We investigated the effect of polymorphisms in the renin-angiotensin-aldosterone system (RAAS) genes on ventricular remodeling, growth, renal function, and response to enalapril in infants with single ventricle.

METHODS AND RESULTS

Single ventricle infants enrolled in a randomized trial of enalapril were genotyped for polymorphisms in 5 genes: angiotensinogen, angiotensin-converting enzyme, angiotensin II type 1 receptor, aldosterone synthase, and chymase. Alleles associated with renin-angiotensin-aldosterone system upregulation were classified as risk alleles. Ventricular mass, volume, somatic growth, renal function using estimated glomerular filtration rate, and response to enalapril were compared between patients with ≥2 homozygous risk genotypes (high risk), and those with <2 homozygous risk genotypes (low risk) at 2 time points: before the superior cavopulmonary connection (pre-SCPC) and at age 14 months. Of 230 trial subjects, 154 were genotyped: Thirty-eight were high risk, and 116 were low risk. Ventricular mass and volume were elevated in both groups pre-SCPC. Ventricular mass and volume decreased and estimated glomerular filtration rate increased after SCPC in the low-risk (P<0.05), but not the high-risk group. These responses were independent of enalapril treatment. Weight and height z-scores were lower at baseline, and height remained lower in the high-risk group at 14 months, especially in those receiving enalapril (P<0.05).

CONCLUSIONS

Renin-angiotensin-aldosterone system-upregulation genotypes were associated with failure of reverse remodeling after SCPC surgery, less improvement in renal function, and impaired somatic growth, the latter especially in patients receiving enalapril. Renin-angiotensin-aldosterone system genotype may identify a high-risk subgroup of single ventricle patients who fail to fully benefit from volume-unloading surgery. Follow-up is warranted to assess long-term impact.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00113087.

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.

Genetic variation in angiotensin II type 2 receptor gene influences extent of left ventricular hypertrophy in hypertrophic cardiomyopathy independent of blood pressure

Introduction. Hypertrophic cardiomyopathy (HCM), an inherited primary cardiac disorder mostly caused by defective sarcomeric proteins, serves as a model to investigate left ventricular hypertrophy (LVH). HCM manifests extreme variability in the degree and distribution of LVH, even in patients with the same causal mutation. Genes coding for renin—angiotensin—aldosterone system components have been studied as hypertrophy modifiers in HCM, with emphasis on the angiotensin (Ang) II type 1 receptor (AT1R). However, Ang II binding to Ang II type 2 receptors (AT2R) also has hypertrophy-modulating effects.

Methods. We investigated the effect of the functional +1675 G/A polymorphism (rs1403543) and additional single nucleotide polymorphisms in the 3’ untranslated region of the AT2R gene ( AGTR2) on a heritable composite hypertrophy score in an HCM family cohort in which HCM founder mutations segregate.

Results. We find significant association between rs1403543 and hypertrophy, with each A allele decreasing the average wall thickness by ~0.5 mm, independent of the effects of the primary HCM causal mutation, blood pressure and other hypertrophy covariates ( p = 0.020).

Conclusion. This study therefore confirms a hypertrophy-modulating effect for AT2R also in HCM and implies that +1675 G/A could potentially be used in a panel of markers that profile a genetic predisposition to LVH in HCM.

Prevalence and spectrum of mutations in a cohort of 192 unrelated patients with hypertrophic cardiomyopathy

Hypertrophic Cardiomyopathy (HCM), a common and clinically heterogeneous disease characterized by unexplained ventricular myocardial hypertrophy and a high risk of sudden cardiac death, is mostly caused by mutations in sarcomeric genes but modifiers genes may also modulate the phenotypic expression of HCM mutations. The aim of the current study was to report the frequency of single and multiple gene mutations in a large French cohort of HCM patients and to evaluate the influence of polymorphisms previously suggested to be potential disease modifiers in this myocardial pathology. We report the molecular screening of 192 unrelated HCM patients using denaturing high-performance liquid chromatography/sequencing analysis of the MYBPC3, MYH7, TNNT2 and TNNI3 genes. Genotyping of 6 gene polymorphisms previously reported as putative HCM modifiers (5 RAAS polymorphisms and TNF-α -308 G/A) was also performed. Seventy-five mutations were identified in 92 index patients (48%); 32 were novel. MYBPC3 mutations (25%) represent the most prevalent cause of inherited HCM whereas MYH7 mutations (12%) rank second in the pathogenesis. The onset age was older in patients carrying MYBPC3 mutations than in those with MYH7 mutations. The MYBPC3 IVS20-2A>G splice mutation was identified in 7% of our HCM population. Multiple gene mutations were identified in 9 probands (5%), highlighting the importance of screening other HCM-causing genes even after a first mutation has been identified, particularly in young patients with a severe phenotype. No single or cumulative genetic modifier effect could be evidenced in this HCM cohort.

Gene expression profiling of dilated cardiomyopathy in older male EP4 knockout mice

Using a line of mice with cardiac-specific knockout (KO) of the EP4 receptor gene, experiments were designed to determine whether a cardiac phenotype developed with age. Cardiac function was assessed by echocardiography in 23- to 33-wk-old male and female KO and littermate controls (WT) mice. After echocardiography, hearts were removed to assess weight, and then some were further processed for histology [myocyte cross-sectional area (MCSA), interstitial collagen fraction (ICF), and macrophage infiltration] and some for extraction of total RNA and protein. Older male KO mice had reduced ejection fraction (EF) coupled with left ventricular dilatation. MCSA and infiltrating macrophages were not different between groups, but ICF increased by 39% in KO mice. In contrast to male KO mice, 30- to 32-wk-old female KO mice had only a slight reduction in EF. To understand gene expression differences between male WT and KO mice, we performed whole genome gene expression profiling (Illumina BeadChips) on hearts of 30-to 32-wk-old mice. Data indicated that 156 genes were overexpressed in the KO hearts more than twofold, including genes involved in remodeling, inflammation, and oxidative stress. Overexpressed chemokines/cytokines were further examined in hearts of 10- to 12-wk-old male KO mice, and we found that growth differentiation factor-15 (GDF-15) expression was higher in KO than in WT hearts. In conclusion, EP4 knockdown in cardiac myocytes in aged male KO mice is in part associated with increased fibrosis, reduced EF, and dilated cardiomyopathy. Early overexpression of GDF-15 in hearts of male KO mice may contribute to or be a marker of the disease phenotype. The absence of serious cardiac dysfunction in aged female mice suggests a sexual dimorphism in the phenotype.

[Update on pediatric cardiology and congenital heart disease]

The fields of pediatric cardiology and congenital heart disease have experienced considerable progress in the last few years, with advances in new diagnostic and therapeutic techniques that can be applied at all stages of life from the fetus to the adult. This article reviews scientific publications in a number of areas that appeared between August 2007 and September 2008. In developed countries, congenital heart disease is becoming increasingly prevalent in nonpediatric patients, including pregnant women. Actions aimed at preventing coronary heart disease must be started early in infancy and should involve the promotion of a healthy diet and lifestyle. Recent developments in echocardiography include the introduction of three-dimensional echocardiography and of new techniques such as two-dimensional speckle tracking imaging, which can be used for both anatomical and functional investigations in patients with complex heart disease, including a univentricular heart. Progress has also occurred in fetal cardiology, with new data on prognosis and prognostic factors and developments in intrauterine interventions, though indications for these interventions have still to be established. Heart transplantation has become a routine procedure, supplemented in some cases by circulatory support devices. In catheter interventions, new devices have become available for the closure of atrial or ventricular septal defects and patent ductus arteriosus as well as for percutaneous pulmonary valve implantation. Surgery is also advancing, in some cases with hybrid techniques, particularly for the treatment of hypoplastic left heart syndrome. The article ends with a review of publications on cardiomyopathy, myocarditis and the treatment of bacterial endocarditis.