Angiotensin-converting enzyme-gene polymorphism is associated with collagen I synthesis and QT dispersion in essential hypertension

Role of collagen turnover biomarkers in the noninvasive assessment of myocardial fibrosis: an update

The pro-fibrotic milieu, as the result of the extracellular matrix remodeling, is a central feature in the pathophysiology of heart disease and contributes to its high morbidity and mortality. Fibrosis is a recognized risk factor for development of heart failure and arrythmias and is usually detected by cardiac magnetic resonance or endomyocardial biopsy. Collagen type I and type III are major components of the collagen network, and the assessment of their derived biomarkers could serve as estimate of the myocardial fibrotic content. This review summarizes data from numerous studies in which these biomarkers have proven their diagnostic and prognostic utility, setting the stage for further randomized clinical trials that might translate into early implementation of antifibrotic therapies.

Association Between ACE Gene Polymorphism and QT Dispersion in Patients with Acute Myocardial Infarction

Background:

Angiotensin converting enzyme (ACE) gene polymorphism is associated with high renin-angiotensin system causing myocardial fibrosis and ventricular repolarization abnormality. Based on these findings, this study was designed to determine the association between ACE gene insertion/deletion (I/D) polymorphism and QT dispersion after acute myocardial infarction (MI).

Objective and Methods:

The study included 108 patients with acute MI. Blood samples were obtained from all the patients for genomic DNA analysis. ECGs were recorded at baseline and at the end of a 6-month follow up. The OT dispersion was manually calculated.

Results:

The mean age of the patients was 57.5 ±9.9 years (ranging from 36 to 70). The patients with DD genotype showed longer QT dispersion than patients with II or DI genotype at the baseline, while at the end of the six-month follow up the patients with DI genotype showed longer QT dispersion than patients with DD or II genotypes. However, the magnitude of the QT dispersion prolongation was higher in patients carrying the ACE D allele than patients who were not carrying it, at baseline and at the end of six-month follow up (52.5 ±2.6 msn vs. 47.5±2.1 msn at baseline, 57±3.2 msn vs. 53±2.6 msn in months, P: 0.428 and P: 0.613, respectively).

Conclusion:

Carriers of the D allele of ACE gene I/D polymorphism may be associated with QT dispersion prolongation in patients with MI.An interaction of QT dispersion and ACE gene polymorphism may be associated with an elevation of serum type I-C terminal pro-collagen concentration, possibly leading to myocardial fibrosis, and increased action potential duration.

The relationship between angiotensin converting enzyme gene I/D polymorphism and QT dispersion in patients with hypertrophic cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is characterized by disorganized myocardial architecture, and may cause ventricular arrhythmias and sudden death. The angiotensin-converting enzyme (ACE) with two deletion alleles (DD genotype) has been proposed to be associated with increased myocardial collagen content. We evaluated QT dispersion (QTd), which reflects regional differences in ventricular repolarization, in HCM patient and controls among the three different ACE genotypes.

MATERIALS AND METHODS

Sixty-three patients with HCM and 20 healthy subjects were included in the study. QT parameters were measured from 12 lead electrocardiograms. ACE genotypes were determined from the DNA extracted from peripheral blood by a polymerase chain reaction (PCR) method. QT parameters were compared among the three ACE genotypes both in HCM patients and controls.

RESULTS

Median ages were similar in HCM and control groups. QTd and corrected QTd (QTcd) were significantly greater in the HCM group compared with the controls. The frequencies of each genotype were similar in both groups. Although QTd and QTcd did not differ among the three genotypes in the control subjects, they were significantly greater in patients with DD genotype compared with other genotypes in the HCM group.

CONCLUSION

QTd and QTcd are increased in patients with HCM, especially in those with the DD genotype.

Functional polymorphisms in ACE and CYP11B2 genes and atrial fibrillation in patients with hypertensive heart disease

BACKGROUND

The activated renin-angiotensin-aldosterone system has been reported to play an important role in the pathogenesis of atrial fibrillation (AF). We hypothesized that functional genetic variations of angiotensin-converting enzyme (ACE) and CYP11B2 genes may influence the susceptibility to AF in patients with hypertensive heart disease.

METHODS

The I/D polymorphism of ACE was detected by polymerase chain reaction (PCR), and the -344C/T polymorphism of the CYP11B2 gene was detected using PCR and subsequent cleavage by HaeIII restriction endonuclease.

RESULTS

The overall distribution of ACE I/D genotypes in patients with and without AF was significantly different (p=0.001). The frequency of the DD genotype was significantly higher in patients with AF than in patients without AF (20.6% vs. 8.1%, OR 2.94, 95% CI 1.64-5.26, p<0.001). The frequency of the D allele was significantly higher in the AF group than in the non-AF group (p=0.001). After adjustment for age and left atrial dimension, multivariable analysis showed that the DD genotype of the ACE gene was an independent risk factor for AF in patients with hypertensive heart disease. No relationship between -344 C/T CYP11B2 polymorphism and AF was found in this cohort.

CONCLUSIONS

Our study suggests that ACE I/D polymorphism is associated with AF and the DD genotype may be an independent predictive factor for AF in patients with hypertensive heart disease.

The angiotensin-converting enzyme insertion/deletion polymorphism is associated with phagocytic NADPH oxidase-dependent superoxide generation: potential implication in hypertension

The objective of the present study was to analyse the influence of the ACE (angiotensin-converting enzyme) gene I/D (insertion/deletion) polymorphism on NADPH oxidase-dependent O(2)(*-) (superoxide radical) production, and to investigate the clinical implication of this association in hypertensive subjects. A case-control study was performed in a random sample of the general population composed of 189 normotensive subjects and 223 hypertensive subjects. The ACE polymorphism was determined by PCR. NADPH oxidase-dependent O(2)(*-) production was quantified in phagocytic cells by chemiluminescence. MMP-9 (matrix metalloproteinase-9), a marker of atherosclerosis previously reported to be associated with NADPH oxidase overactivity, was quantified by ELISA in plasma samples. The distribution of genotypes was in Hardy-Weinberg equilibrium. The I/D polymorphism was not associated with hypertension. NADPH oxidase-dependent O(2)(*-) production was significantly higher in D/D (deletion/deletion) than in I/I (insertion/insertion) and I/D, both in normotensive and hypertensive subjects. Interestingly, plasma levels of angiotensin II were significantly higher in D/D than in I/I and I/D, both in normotensive and hypertensive subjects. Plasma levels of MMP-9 and systolic blood pressure values were significantly higher in D/D than in I/I and I/D hypertensive subjects, whereas no differences were found among genotypes in normotensive subjects. Interestingly, NADPH oxidase-dependent O(2)(*-) production positively associated with plasma MMP-9 levels in hypertensive subjects, which remained significant after adjustment for age and gender. In conclusion, in the present study we have reported for the first time an association of the D/D genotype of the ACE I/D polymorphism with phagocytic NADPH oxidase-mediated O(2)(*-) overproduction. Within the group of hypertensive patients, D/D cases also associated with increased blood pressure values and with enhanced plasma levels of MMP-9.

Angiotensin-converting enzyme gene polymorphism in arrhythmogenic right ventricular dysplasia: is DD genotype helpful in predicting syncope risk?

Introduction. Arrhythmogenic right ventricular dysplasia (ARVD) is a heritable disorder characterised by fibrofatty replacement of right ventricular myocytes and increased risk of ventricular arrhythmias and sudden cardiac death. Angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism affects myocardialACE levels. DD genotype favours myocardial fibrosis and is associated with malignant ventricular tachycardia.The aim of this study was to explore ACE gene polymorphism inARVD patients.

Methods. Twenty-nine patients with ARVD and 24 controls were included.AllARVD patients had documented sustained ventricular tachycardia. Thirteen patients had syncopal episodes. Six patients were resuscitated from sudden cardiac death.ACE gene polymorphism was identified by polymerase chain reaction technique.

Results. There was no significant difference in DD genotype frequency between ARVD patients and controls (44.8% vs. 45.8%, p=0.94). However, DD genotype frequency was significantly higher in ARVD patients with syncopal episodes compared to those without syncope (69.2% vs. 25.0%, p=0.017, odds ratio:6.750,95% confidence interval: 1.318—34.565). DD genotype was detected in higher frequency also in patients with a family history of sudden cardiac death (66.7% vs. 39.1%,p=0.36).

Conclusion. High prevalence of DD genotype in ARVD patients with syncope suggests that ACE I/D polymorphism might be useful in identifying high-risk patients for syncope.

Association between angiotensin-converting enzyme gene polymorphisms and QT duration in a multiethnic population in Hawaii

OBJECTIVES

Recent studies have suggested that heart-rate corrected QT interval (QTc) in normal populations may be influenced by genetic factors. We report findings of a study of the relationship between QTc, increased QTc (> 440 ms) and angiotensin-converting enzyme (ACE) genotype in a multiethnic, population-based study completed in rural Hawaii.

METHODS

Blood samples were obtained while fasting and after an oral glucose challenge from 1452 individuals between 1997 and 2000. The clinical examination included an electrocardiogram. Medical histories, behavioral and socio-demographic information were obtained during the interview. Ethnicity was estimated by self-report. The insertion/deletion (I/D) polymorphism in intron 16 of the ACE gene was determined by polymerase chain reaction (PCR) from a random sample of 588 participants. Multiple linear and logistic regression was used to test for associations between QTc and ACE gene polymorphisms.

RESULTS

The overall crude prevalence of increased QTc was 21.2%. The prevalence of increased QTc was lowest among those with ACE DD genotype, and highest among those with ACE insertion/insertion (II) genotype. The adjusted odds ratio for increased QTc was 2.29 (95% CI 1.02-5.12) and 3.61 (95% CI 1.60-8.13) for ID and II genotypes, respectively, compared to the DD genotype. The test for trend was highly significant (p < 0.001).

CONCLUSIONS

The ACE insertion allele was associated with increased prevalence of prolonged QTc independent of ethnicity, age, gender, and BMI. These findings may implicate the ACE gene as an important genetic risk factor for cardiovascular disease morbidity and mortality.

D-Allele of ACE Polymorphism is Associated With Increased Magnitude of QT Dispersion Prolongation in Elderly Chinese 4-Year Follow-up Study

BACKGROUND

There has not been a longitudinal investigation of the influence of angiotensin-converting enzyme (ACE) insertion/deletion and angiotensinogen (AGT) M235T gene polymorphisms on repolarization parameters, such as QT dispersion (QTd) and the peak and the end of the T-wave interval (Tpe).

METHODS AND RESULTS

Electrocardiographys were recorded from 106 elderly Chinese at baseline, and 2nd and 4th year follow-up. The corrected QT (QTc), QTd, QTc dispersion (QTcd) and Tpe were manually calculated. Average age was 72.7+/-4.1 years (range 62-81). QTd, QTcd and Tpe were significantly prolonged (all p<0.001 at the 2nd and 4th year). At the 4th year the magnitude of the QTd prolongation, but not Tpe, was significantly higher in subjects carrying the ACE D allele than non-D-allele carriers (p=0.001), as was QTcd (p=0.002). This association was still significant in the multivariate analyses (p<0.001 and p=0.001 for QTc and QTcd, respectively). No significant correlation was found between repolarization parameters and AGT genotype.

CONCLUSIONS

This longitudinal study shows that the ageing process is associated with prolongation of QTd, QTcd and Tpe after 4 years follow-up. The elderly Chinese subjects with the ACE D-allele had greater prolongation QTd and QTcd.

Lone and secondary nonvalvular atrial fibrillation: role of a genetic susceptibility

BACKGROUND

An involvement of the renin angiotensin system in atrial fibrillation (AF) has been hypothesized, and ACE DD genotype has been suggested to influence the predisposition to AF. The aim of this study was to investigate the role of the ACE I/D polymorphism in relation to the different clinical forms of AF, lone and secondary nonvalvular atrial fibrillation (NVAF).

METHODS

510 consecutive patients with documented NVAF (106 patients had lone, and 404 secondary NVAF), and 520 controls with a negative history of cardiovascular disease have been studied.

RESULTS

A significant difference in allele frequency between lone and secondary NVAF (p=0.002) has been found. The ACE D allele was associated with the predisposition to lone NVAF under a dominant, recessive and additive model, both at univariate and multivariate analysis, after adjustment for age and gender (multivariate analysis: dominant OR=2.87, p=0.02; recessive OR=2.01, p=0.003; additive OR=4.47, p<0.0001). ACE D allele was significantly associated with secondary NVAF at both univariate and multivariate analysis under a recessive and additive, but not dominant, model (multivariate analysis: recessive OR=1.89, p=0.001; additive OR=2.50, p<0.0001).

CONCLUSIONS

This study highlights the role of ACE gene in predisposing to both lone and secondary NVAF, further contributing to penetrate the genetic mechanisms responsible for this complex disease. The clinical relevance of our results may be related to the possible characterization of subjects predisposed to NVAF in the absence of traditional risk factors, and to the use of ACE-inhibitors therapy able to improve the arrhythmogenic substrate.

Blockade of renin-angiotensin system reduces QT dispersion and improves intracellular Ca/Mg status in hemodialysis patients

BACKGROUND

Electrolyte impairments are common in hemodialysis (HD) patients. Consequently, QT dispersion (QTd) is prolonged, correlating with high intracellular magnesium. In patients with cardiac disorders, renin-angiotensin system (RAS) inhibition reduces QTd.

AIM

To compare the effects of ACE inhibition or AT-1 blockade on QTd duration and intracellular magnesium (Mg)/calcium (Ca) in peripheral blood mononuclear cells (PBMC) from chronic HD patients.

METHODS

24 HD patients received cilazapril for 8 weeks and, following a 2-week withdrawal, were switched to valsartan for additional 8 weeks. QTd measurements and PBMC isolation were performed at the beginning and the end of each period. Total intracellular Ca and Mg were assessed by atomic spectrometer, and cytosolic free Ca2+ by fluorocytometer.

RESULTS

Both treatments significantly decreased QTd, demonstrating similar reduction magnitudes. In both groups, PBMC exhibited basally low cytosolic Ca2+ and undisturbed high transmembrane Ca2+ influx following phytohemagglutinin stimulation. Total intracellular Ca was increased, while Mg was reduced, following either treatment. The total intracellular Ca/Mg ratio inversely correlated with QTd duration.

CONCLUSIONS

(1) RAS inhibition reduces prolonged QTd in HD patients. (2) In PBMC from ordinarily Ca-depleted HD patients, RAS suppression brings about elevation of total intracellular Ca. (3) RAS blockade decreases high intracellular Mg in PBMC from HD patients. Consequently, the Ca/Mg ratio increases, inversely correlating with QTd reduction.

Renin-angiotensin polymorphisms and QTc interval prolongation in end-stage renal disease

BACKGROUND

Polymorphisms of renin-angiotensin system (RAS) genes in patients with end-stage renal disease (ESRD) on chronic hemodialysis may be associated with QTc interval prolongation, leading to fatal arrhythmias. The objective of this study was to determine (1) the prevalence of QTc prolongation in hemodialysis patients, and (2) the association of a prolonged QTc in these patients with RAS polymorphisms [angiotensin-converting enzyme-insertion/deletion (ACE-I/D), angiotensin type 1 receptor-A1166C (AT1R-A1166C), and angiotensinogen-M235T (AGT-M235T)].

METHODS

Twelve-lead electrocardiograms (ECGs), serum electrolytes (sodium, potassium, and calcium), and ACE and angiotensin II levels were obtained 10 to 12 hours after a hemodialysis session in 43 patients with ESRD on chronic hemodialysis [mean age (+/-SD), 55 +/- 14 years]. Using polymerase chain reaction (PCR), the presence of polymorphisms of the ACE-I/D, AT1R-A1166C, and AGT-M235T genes was determined from the buccal cells. A maximum QT interval in patients with sinus rhythm and normal QRS duration was corrected for heart rate using Hodges' formula.

RESULTS

Fifty-eight percent of the patients had QTc interval prolongation (>440 msec). The ACE-DD genotype (P = 0.002) and the C allele of the AT1R-A1166C gene (P = 0.004), but not the AGT-M235T gene, contributed to QTc prolongation.

CONCLUSION

Polymorphisms of ACE and AT1R genes additively contribute to QTc prolongation found in a great majority of ESRD patients. Therefore, ESRD patients with both or one of these polymorphisms may be at a higher risk for sudden cardiac death.

New directions in the assessment and treatment of hypertensive heart disease

PURPOSE OF REVIEW

This article will review briefly the emerging new concepts in the diagnosis and treatment of myocardial fibrosis in patients with hypertensive heart disease.

RECENT FINDINGS

Although hypertensive heart disease is characterized clinically by development of left-ventricular hypertrophy in the absence of a cause other than arterial hypertension, changes in the composition of myocardial tissue also develop in arterial hypertension leading to structural remodeling of the myocardium (e.g. fibrosis). Recent available data on the determination of serum concentrations of collagen-derived serum peptides and quantitative analysis of echoreflectivity to address the presence of fibrosis in the myocardium of hypertensive patients are promising. In addition, preliminary data suggest that the goal of reducing myocardial fibrosis is achievable in patients with hypertensive heart disease using specific antihypertensive agents (e.g. those interfering with angiotensin II).

SUMMARY

The time has come to revisit the current management of hypertensive heart disease simply focused on detecting left-ventricular hypertrophy and controlling blood pressure to reduce left-ventricular mass. It is necessary to develop new approaches aimed at assessing and repairing alterations of myocardial structure and protect myocardial function and, in so doing, to reduce in a more-effective manner adverse risk associated with hypertensive heart disease.

Prevalence and risk factors for prolonged QTc in a multiethnic cohort in rural Hawaii

BACKGROUND

Few studies have examined the biochemical risk factors for prolonged QTc, a predictor of mortality in numerous studies. We report on the prevalence and risk factors for prolonged QTc in a multiethnic population in rural Hawaii.

METHODS

Electrocardiograms were collected from 1415 participants in a cross-sectional survey. The QT interval lengths were corrected for heart rate using Bazett's formula. Linear and logistic regression models were used to examine associations between various cardiovascular risk factors with QTc.

RESULTS

Among the CVD risk factors examined, only age, gender, 2-h glucose, and systolic blood pressure (SBP) were independently associated with QTc interval length. Significant ethnic differences in prevalence were also observed, which persisted after controlling for other risk factors.

CONCLUSIONS

Significant associations between prolonged QTc and ethnic ancestry, but not cholesterol or triglyceride levels, suggest that genetic factors may play a more important role in determining QTc interval length than conventional biochemical and metabolic CVD risk factors.

Hypertensive heart disease and fibrosis

PURPOSE OF REVIEW

The clinical importance of fibrosis in hypertensive heart disease is now well recognized. However, the precise mechanisms involved in the pathophysiology and therefore the potential cardioreparative strategies are still not fully understood. These areas continue to be the focus of extensive research. This review summarizes the work conducted in this field over the past 12 months.

RECENT FINDINGS

This article further confirms the involvement of the renin-angiotensin system in cardiac fibrosis and illustrates the supportive roles of mineralocorticoids, endothelin, and novel signaling pathways. It also summarizes the most recent data examining the genetic aspects of myocardial fibrosis and further clarifies potential cardioreparative strategies.

SUMMARY

Myocardial fibrosis in hypertensive heart disease remains an area of intensive research. Whereas recent work has expanded our knowledge of the underlying processes in the development of this fibrosis, additional scientific and clinical research is required to assist clinical risk assessment and to provide evidence that therapeutic intervention confers improved clinical outcome in hypertensive heart disease.