Functional effects of β1-adrenoceptor polymorphisms on the hemodynamic response to dobutamine with and without β-blocker administration

Effect of β1-adrenergic receptor gene polymorphism on ventricular arrhythmia and prognosis after myocardial infarction

BACKGROUND

Ventricular arrhythmia is a common complication of acute myocardial infarction (AMI). The Arg389Gly polymorphism of the β1-adrenergic receptor genotype may affect AMI patients.

METHOD

Patients diagnosed with AMI were included in this study. Clinical data were obtained from the patient's medical history, and genotypes were retrieved from laboratory test reports. ECG data were recorded daily. Data analysis was performed using SPSS 20.0, and differences were deemed statistically significant at P  < 0.05.

RESULT

In the final study, 213 patients were included. The proportions of the Arg389Arg, Arg389Gly, and Gly389Gly genotypes were 65.7%, 21.6%, and 12.7%, respectively. Patients with the Arg389Arg genotype exhibited significantly elevated cardiac troponin T (cTnT) and pro-BNP levels compared to the Arg389Gly and Gly389Gly genotypes [cTnT: 4.00 ± 2.43 ng/ml versus 2.82 ± 1.82 ng/ml, P  = 0.012; pro-BNP: 1942.37 (1223.194, 206.59) pg/ml versus 1604.57 (798.05, 1884.79) pg/ml, P  = 0.005]. Patients with the Arg389Arg genotype exhibited a lower ejection fraction than those with the Gly389Gly genotype (54.13 ± 4.94% vs. 57.11 ± 2.87%, P  < 0.001). Patients homozygous for Arg389Arg exhibited a higher incidence of ventricular tachycardia and a greater proportion of premature ventricular contraction (PVC) compared to patients homozygous for Gly389Gly (ventricular tachycardia: 19.29% vs. 0.00%, P  = 0.009; PVC: 70.00% vs. 40.74%, P  = 0.003).

CONCLUSION

The Arg389Arg genotype is associated with greater myocardial damage, impaired cardiac function, and an increased probability of ventricular arrhythmia in AMI patients.

Adrenergic receptors gene polymorphisms and autonomic nervous control of heart and vascular tone

Adrenergic receptors (ARs) are the primary targets of catecholamines released from the sympathetic nerve endings during their activation. ARs play a central role in autonomic nervous system and serve as important targets of widely used drugs. Several ARs gene polymorphisms were found to be associated with cardiovascular disease in previous clinical studies. Although more precise mechanism of the polymorphisms influence on autonomic control of cardiovascular system was studied in many previous physiological studies, their results are not unequivocal. This paper reviews the results of clinical and physiological studies focused on the impact of selected common single nucleotide polymorphisms of ARs genes involved in sympathetic control on cardiovascular system and its control. In summary, many studies assessed only a very limited range of cardiovascular control related parameters providing only very limited view on the complex cardiovascular control. The overview of partially contradicting results underlines a need to examine wider range of cardiovascular measures including their reactivity under various stress conditions requiring further study. It is expected that an effect of one given polymorphism is not very prominent, but it is suggested that even subtle differences in cardiovascular control could – on a longer time scale – lead to the development of severe pathological consequences.

Beta-adrenergic receptors gene polymorphisms are associated with cardiac contractility and blood pressure variability

Beta-adrenergic receptors (beta-ARs) play a pivotal role in the cardiovascular regulation. In the human heart beta1- and beta2-ARs dominate in atria as well as in ventricle influencing heart rate and myocardial contractility. Some single nucleotide polymorphisms (SNPs) of beta-ARs might influence cardiovascular function. However, the influence of beta-AR genes SNPs on hemodynamic parameters at rest and their reactivity under stress is still not well known. We aimed to explore the associations between four selected beta-ARs gene polymorphisms and selected cardiovascular measures in eighty-seven young healthy subjects. While in beta1-AR polymorphism rs1801252 no significant association was observed, second beta1-AR polymorphism rs1801253 was associated with decreased cardiac output and cardiac index during all phases and with decreased flow time corrected and ejection time index at rest and during mental arithmetics. Polymorphism rs1042713 in beta2-AR was associated with alterations in blood pressure variability at rest and during head-up-tilt, while rs1042714 was associated predominantly with decreased parameters of cardiac contractility at rest and during mental arithmetics. We conclude that complex analysis of various cardiovascular characteristics related to the strength of cardiac contraction and blood pressure variability can reveal subtle differences in cardiovascular sympathetic nervous control associated with beta-ARs polymorphisms.

β1-adrenoceptor Arg389Gly polymorphism confers differential β-arrestin-binding tropism in cardiac myocytes

AIM

The β₁-adrenergic receptor (AR) Arg389Gly polymorphism affects efficacy of its procontractile signaling in cardiomyocytes and carriers' responses to β-blockers. To identify molecular mechanisms underlying functional differences between Arg389 and Gly389 β₁ARs, we examined their binding to β-arrestins (βarr-1 and -2), which mediate β₁AR signaling, in neonatal rat ventricular myocytes.

METHODS

We tested the β₁AR-βarr interaction via β₁AR immunoprecipitation followed by βarr immunoblotting.

RESULTS

βarr1 binds both variants upon isoproterenol, carvedilol or metoprolol treatment in neonatal rat ventricular myocytes. Conversely, the potentially beneficial in the heart βarr2 only interacts with the Arg389 receptor in response to isoproterenol or carvedilol.

CONCLUSION

Arg389 confers unique βarr2-interacting tropism to the β₁AR in cardiac myocytes, potentially underlying this variant's gain-of-function phenotype and better clinical responses to β-blockers.

Effects of sex and the common ADRB1 389 genetic polymorphism on the hemodynamic response to dobutamine

INTRODUCTION

The ADRB1 389 polymorphism affects responses to the β-1 adrenergic receptor (β1AR) agonist in vitro. Previous studies on its effect on the response to dobutamine stress echocardiography were conflicting. In addition, sex differences in the response to dobutamine have been suggested. The aim of this study was to determine whether the ADRB1 389 polymorphism affects the hemodynamic response to dobutamine in healthy individuals including men and women.

PARTICIPANTS AND METHODS

Healthy individuals were recruited according to their ADRB1 49 and 389 genotypes [15 Arg389Arg, 10 Gly389Arg, and 10 Gly389Gly individuals, (all Ser49Ser), 21 men and 14 women]. Dobutamine was infused at 2, 4, and 6 mcg/kg/min. Standardized exercise was performed during the last minute of each infusion.

RESULTS

Resting heart rate (HR) response to 6 mcg/kg/min dobutamine (ΔHR) was 4.7-fold larger in Arg389Arg than in Gly389Gly [(mean ± SD) 12.95 ± 6.99, 2.75 ± 1.65 bpm, respectively, PANOVA=0.012]. Renin response to dobutamine (ΔRenin) was 3.9-fold greater in Arg389Arg than in Gly389Gly (PANOVA=0.032). Among Arg389Gly heterozygotes, ΔHR and ΔRenin were not significantly different from either homozygote group. In multivariate analysis for ΔHR variance, significant contributions were observed for genotype (P=0.011), baseline HR (P=0.011), and borderline effect for sex (P=0.049).

CONCLUSION

In healthy individuals, HR and renin responses to dobutamine were more than three-fold greater among ADRB1 Arg389 compared with Gly389 homozygotes. Future studies on the effect of the ADRB1 389 polymorphism on dobutamine stress echocardiography should compare Arg389 and Gly389 homozygotes.

Ivabradine: potential clinical applications in critically ill patients

It has been extensively demonstrated that an elevated heart rate is a modifiable, independent risk factor for cardiovascular events. A high heart rate increases myocardial oxygen consumption and reduces diastolic perfusion time. It can also increase ventricular diastolic pressures and induce ventricular arrhythmias. Critical care patients are prone to develop a stress induced cardiac impairment and consequently an increase in sympathetic tone. This in turn increases heart rate. In this setting, however, heart rate lowering might be difficult because the effects of inotropic drugs could be hindered by heart rate reducing drugs like beta-blockers. Ivabradine is a new selective antagonist of funny channels. It lowers heart rate, reducing the diastolic depolarization slope. Moreover, ivabradine is not active on sympathetic pathways, thus avoiding any interference with inotropic amines. We reviewed the literature available regarding heart rate control in critical care patients, focusing our interest on the use of ivabradine to assess the potential benefits of the drug in this particular setting.

Impact of the β1-adrenoceptor Arg389Gly polymorphism on heart-rate responses to bisoprolol and carvedilol in heart-failure patients

This pharmacogenetic substudy of the prospective, double-blind, randomized CIBIS-ELD trial determined the impact of the β1-adrenoceptor Arg189Gly polymorphism on heart-rate responses to bisoprolol or carvedilol in elderly patients with heart failure (421 with sinus rhythm, 107 with atrial fibrillation). Patients were randomized 1:1 to bisoprolol or carvedilol with a fortnightly dose-doubling scheme and guideline target doses. Patients with sinus rhythm responded essentially identically to bisoprolol and carvedilol, independent of genotype. Atrial fibrillation patients homozygous for Arg389 had a much smaller response to carvedilol than carriers of at least one Gly389 allele (mean difference 12 bpm, P < 0.00001). Carvedilol up to 2 × 12.5 mg did not reduce heart rate in Arg389Arg homozygotes at all. Interestingly, the immediate response to carvedilol did not differ between genotypes. The Arg389Gly polymorphism has a major impact on the heart-rate response to carvedilol (but not bisoprolol) in patients with heart failure plus atrial fibrillation.

Effect of the ADRB1 1165C>G and 145A>G polymorphisms on hemodynamic response during dobutamine stress echocardiography

Purpose

The aim of this study was to determine an association between the ADRB1 1165C>G and 145A>G polymorphisms and hemodynamic response [heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure] to dobutamine during dobutamine stress echocardiography (DSE).

Methods

The study involved 144 patients with clinical indications for DSE. The PCR–restriction fragment length polymorphism method was used to identify the ADRB1 1165C>G and 145A>G polymorphisms.

Results

Heart rate during DSE increased in all analyzed study groups. Patients with the ADRB1 1165CC and 1165CG+GG polymorphisms demonstrated similar HR, including magnitude of response [change in heart rate (ΔHR 0–30): 42.1 ± 17.5 vs. 46.1 ± 15.5 bpm, respectively]. HR and ΔHR 0–30 were comparable in ADRB1145AA and 145AG subjects in the course of DSE. SBP and DBP at all stages of DSE were similar in subjects with either polymorphism and did not differentiate patients with the ADRB1 145AA polymorphism from those with the ADRB1 145AG polymorphism, nor those with the ADRB1 1165CC polymorphism from those with the ADRB1 1165CG+GG polymorphism. No differences were noted in the magnitude of response, with the increase in SBP and DBP comparable in all genotypes. Similar observations were made in patients (25/144 studied) with atropine requirements during DSE.

Conclusion

The ADRB1 1165C>G and 145A>G polymorphisms are not associated with the HR, SBP and DBP responses in Polish Caucasian patients requiring diagnostic dobutamine stress echocardiography