A novel polymorphism in the gene coding for the beta(1)-adrenergic receptor associated with survival in patients with heart failure

A cross-ancestry genome-wide meta-analysis, fine-mapping, and gene prioritization approach to characterize the genetic architecture of adiponectin

Previous genome-wide association studies (GWASs) for adiponectin, a complex trait linked to type 2 diabetes and obesity, identified >20 associated loci. However, most loci were identified in populations of European ancestry, and many of the target genes underlying the associations remain unknown. We conducted a cross-ancestry adiponectin GWAS meta-analysis in ≤46,434 individuals from the Metabolic Syndrome in Men (METSIM) cohort and the ADIPOGen and AGEN consortiums. We combined study-specific association summary statistics using a fixed-effects, inverse variance-weighted approach. We identified 22 loci associated with adiponectin (p < 5×10-8), including 15 known and seven previously unreported loci. Among individuals of European ancestry, Genome-wide Complex Traits Analysis joint conditional analysis (GCTA-COJO) identified 14 additional distinct signals at the ADIPOQ, CDH13, HCAR1, and ZNF664 loci. Leveraging the cross-ancestry data, FINEMAP + SuSiE identified 45 causal variants (PP > 0.9), which also exhibited potential pleiotropy for cardiometabolic traits. To prioritize target genes at associated loci, we propose a combinatorial likelihood scoring formalism (Gene Priority Score [GPScore]) based on measures derived from 11 gene prioritization strategies and the physical distance to the transcription start site. With GPScore, we prioritize the 30 most probable target genes underlying the adiponectin-associated variants in the cross-ancestry analysis, including well-known causal genes (e.g., ADIPOQ, CDH13) and additional genes (e.g., CSF1, RGS17). Functional association networks revealed complex interactions of prioritized genes, their functionally connected genes, and their underlying pathways centered around insulin and adiponectin signaling, indicating an essential role in regulating energy balance in the body, inflammation, coagulation, fibrinolysis, insulin resistance, and diabetes. Overall, our analyses identify and characterize adiponectin association signals and inform experimental interrogation of target genes for adiponectin.

Impact of Neuroeffector Adrenergic Receptor Polymorphisms on Incident Ventricular Fibrillation During Acute Myocardial Ischemia

Background Cardiac adrenergic receptor gene polymorphisms have the potential to influence risk of developing ventricular fibrillation (VF) during ST-segment-elevation myocardial infarction, but no previous study has comprehensively investigated those most likely to alter norepinephrine release, signal transduction, or biased signaling. Methods and Results In a case-control study, we recruited 953 patients with ST-segment-elevation myocardial infarction without previous cardiac history, 477 with primary VF, and 476 controls without VF, and genotyped them for ADRB1 Arg389Gly and Ser49Gly, ADRB2 Gln27Glu and Gly16Arg, and ADRA2C Ins322-325Del. Within each minor allele-containing genotype, haplotype, or 2-genotype combination, patients with incident VF were compared with non-VF controls by odds ratios (OR) of variant frequencies referenced against major allele homozygotes. Of 156 investigated genetic constructs, 19 (12.2%) exhibited significantly (P<0.05) reduced association with incident VF, and none was associated with increased VF risk except for ADRB1 Gly389 homozygotes in the subset of patients not receiving β-blockers. ADRB1 Gly49 carriers (prevalence 23.0%) had an OR (95% CI) of 0.70 (0.49-0.98), and the ADRA2C 322-325 deletion (Del) carriers (prevalence 13.5%) had an OR of 0.61 (0.39-0.94). When present in genotype combinations (8 each), both ADRB1 Gly49 carriers (OR, 0.67 [0.56-0.80]) and ADRA2C Del carriers (OR, 0.57 [0.45- 0.71]) were associated with reduced VF risk. Conclusions In ST-segment-elevation myocardial infarction, the adrenergic receptor minor alleles ADRB1 Gly49, whose encoded receptor undergoes enhanced agonist-mediated internalization and β-arrestin interactions leading to cardioprotective biased signaling, and ADRA2C Del322-325, whose receptor causes disinhibition of norepinephrine release, are associated with a lower incidence of VF. Registration URL: https://clinicaltrials.gov; Unique identifier: NCT00859300.

Multivariable prognostic model for heart failure in Chinese Han population-based setting

Aims

The prognosis of heart failure (HF) depends on genetic predisposition, and recent studies have shown that impaired autophagy is involved in HF. This study was aimed to construct a prognostic model combining polygenetic background based on the autophagy pathway and other traditional risk factors (TRF) of HF prognosis.

Methods and results

Via re‐analysing the transcriptomic data of 50 failing and 14 non‐failing donors, differentially expressed autophagy‐related genes (ARGs) were chosen for further comparison and analysis with whole exome sequencing and follow‐up data of 1000 HF patients. By searching from reported articles, prognosis‐related polymorphisms were identified. ARGs and prognosis‐related polymorphisms were used to develop genetic risk score (GRS) and genetic risk factor (GRF), respectively. We compared the predictive power of five models [Model 1, GRS; Model 2, composite of TRF and N‐terminal B‐type natriuretic peptide (NT‐proBNP); Model 3, composite of TRF, NT‐proBNP, and GRS; Model 4, composite of TRF, NT‐proBNP, and GRF; and Model 5, composite of TRF, NT‐proBNP, GRF, and GRS] by applying receiver operating characteristic curves. Twenty‐four prognosis‐related polymorphisms were used to construct GRF and 11 variants among 48 differentially expressed ARGs associated with clinical outcomes of HF patients were applied for GRS. GRS was strongly associated with cardiac mortality of HF patients, independent of TRF and GRF (95% confidence interval 1.273–1.739, P = 5.78 × 10⁻⁷). Comparing with patients with lowest GRS tertile, those with highest tertile had higher risks of developing worse clinical outcomes (hazard ratio = 1.866; 95% confidence interval 1.352–2.575, P = 1.47 × 10⁻⁴). The discrimination power of the model including GRS, TRF, GRF, and NT‐proBNP is most considerable (area under curve = 0.777), especially in men, patients over 60, patients with hypertension, patients without diabetes or hyperlipidaemia.

Conclusions

The model combining autophagy‐related GRS, TRF, GRF, and NT‐proBNP performs well in distinguishing between worse‐prognosis and better‐prognosis HF patients, leading a promising strategy for HF treatment and HF prevention.

Pharmacogenetics may explain part of the interindividual variability of dobutamine pharmacodynamics in neonates

AIM

To determine whether the known single nucleotide polymorphisms in adrenoreceptor associated genes affect the hemodynamic response to dobutamine in critically ill neonates.

METHODS

Alleles in the known genetic single nucleotide polymorphisms in β1 and β2 adrenoceptor (AR) genes and Gs protein α-subunit gene (GNAS) possibly affecting inotropic effect were identified in patients of neonatal dobutamine pharmacokinetic-pharmacodynamic study. Linear mixed-effect models were used to describe the effect of genetic polymorphisms to heart rate (HR), left ventricular output (LVO) and right ventricular output (RVO) during dobutamine treatment.

RESULTS

26 neonates (5 term, 21 preterm) were studied. Dobutamine plasma concentration and exposure time respective HR (adjusted to gestational age) is dependent on β1-AR Arg389Gly polymorphism so that in G/G (Gly) homozygotes and G/C heterozygotes dobutamine increases HR more than in C/C (Arg) homozygotes, with parameter estimate (95% CI) of 38.3 (15.8 - 60.7) bpm per AUC of 100 μg L^-1 h, p=0.0008. LVO (adjusted to antenatal glucocorticoid administration and illness severity) and RVO (adjusted to gestational age and illness severity) is dependent on GNAS c.393C>T polymorphism so that in T/T homozygotes and C/T heterozygotes but not in C/C homozygotes LVO and RVO increase with dobutamine treatment, 24.5 (6.2 - 42.9) mL kg^-1 min^-1 per AUC of 100 μg L^-1 h, p=0.0095 and 33.2 (12.1 - 54.3) mL kg^-1 min^-1 per AUC of 100 μg L^-1 h, p=0.0025, respectively.

CONCLUSION

In critically ill neonates, β1-AR Arg389Gly and GNAS c.393C>T polymorphisms may play a role in the haemodynamic response to dobutamine during the first hours and days of life.

Dissecting miRNA–Gene Networks to Map Clinical Utility Roads of Pharmacogenomics-Guided Therapeutic Decisions in Cardiovascular Precision Medicine

MicroRNAs (miRNAs) create systems networks and gene-expression circuits through molecular signaling and cell interactions that contribute to health imbalance and the emergence of cardiovascular disorders (CVDs). Because the clinical phenotypes of CVD patients present a diversity in their pathophysiology and heterogeneity at the molecular level, it is essential to establish genomic signatures to delineate multifactorial correlations, and to unveil the variability seen in therapeutic intervention outcomes. The clinically validated miRNA biomarkers, along with the relevant SNPs identified, have to be suitably implemented in the clinical setting in order to enhance patient stratification capacity, to contribute to a better understanding of the underlying pathophysiological mechanisms, to guide the selection of innovative therapeutic schemes, and to identify innovative drugs and delivery systems. In this article, the miRNA–gene networks and the genomic signatures resulting from the SNPs will be analyzed as a method of highlighting specific gene-signaling circuits as sources of molecular knowledge which is relevant to CVDs. In concordance with this concept, and as a case study, the design of the clinical trial GESS (NCT03150680) is referenced. The latter is presented in a manner to provide a direction for the improvement of the implementation of pharmacogenomics and precision cardiovascular medicine trials.

Genetic Polymorphism of beta1-adrenergic Receptors and the Effect on the Clinical Efficacy of beta-adrenoblockers

Beta-adrenergic blockers are a valuable class of cardiovascular drugs and are widely used in the treatment of arterial hypertension (AH), coronary heart disease, chronic heart failure (CHF), cardiac arrhythmias, significantly improving the prognosis of patients. However, the clinical efficacy of betablockers is largely dependent on the genetic polymorphism of beta1-adrenergic receptors (ADRB1). The aim of the review was a systematic analysis of scientific data from pharmacogenetic studies on the role of beta1-adrenergic receptor polymorphism in the clinical efficacy of beta-blockers in the treatment of hypertension, chronic heart failure, and atrial fibrillation. The results of clinical trials and meta-analyzes were used. Of greatest importance is the genetic polymorphism of beta1-adrenergic receptors of two loci – Arg389Gly and Ser49Gly; the frequency of occurrence of variant and less functionally active alleles Gly389 and Gly49 in Europeans reaches 27% and 15%. The variant Gly389 allele has reduced functional activity and carriers have a weak response to the use of beta-blockers. In carriers of variant alleles Gly389 and Gly49 a reduced hypotensive effect on the use of beta-blockers was observed, and in studies of long-term efficacy, carriage of variant alleles was accompanied by an increase in the frequency and risk of unfavorable outcomes of hypertension. In pharmacogenetic studies, a reduced effect of the effect on myocardial remodeling in patients with CHF for beta-blockers in carriers of the variant Gly389 allele were confirmed. According to two meta-analyzes of trials on use of beta-blockers in patients with CHF, the frequency of increased left ventricle ejection fraction was significantly higher in carriers of the wild Arg389Arg gene type (risk ratio=1.83, p=0,001). In contrast, in atrial fibrillation, the frequency of rhythm control with beta-blockers was achieved better in the presence of the variant allele Gly389 with “loss of function”. Another polymorphic Gly49 allele plays a role in desensitization and down-regulation of beta1-receptor activity, although clinically this effect has been less obvious and contradictory. However, in studies, a more pronounced clinical effect of beta-blockers was observed in carriers of the wild genotype Ser49Ser, as well as in carriers of the haplotype Ser49Ser/Arg389Arg. Thus, genetic polymorphism ADRB1 may be another important predictor of the effectiveness of beta-blockers in clinical practice, which must be taken into account in the treatment of cardiovascular diseases.

Pharmacogenomic Effects of β-Blocker Use on Femoral Neck Bone Mineral Density

CONTEXT

Recent studies have shown that β-blocker (BB) users have a decreased risk of fracture and higher bone mineral density (BMD) compared to nonusers, likely due to the suppression of adrenergic signaling in osteoblasts, leading to increased BMD. There is also variability in the effect size of BB use on BMD in humans, which may be due to pharmacogenomic effects.

OBJECTIVE

To investigate potential single-nucleotide variations (SNVs) associated with the effect of BB use on femoral neck BMD, we performed a cross-sectional analysis using clinical data, dual-energy x-ray absorptiometry, and genetic data from the Framingham Heart Study's (FHS) Offspring Cohort. We then sought to validate our top 4 genetic findings using data from the Rotterdam Study, the BPROOF Study, the Malta Osteoporosis Fracture Study (MOFS), and the Hertfordshire Cohort Study.

METHODS

We used sex-stratified linear mixed models to determine SNVs that had a significant interaction effect with BB use on femoral neck (FN) BMD across 11 gene regions. We also evaluated the association of our top SNVs from the FHS with microRNA (miRNA) expression in blood and identified potential miRNA-mediated mechanisms by which these SNVs may affect FN BMD.

RESULTS

One variation (rs11124190 in HDAC4) was validated in females using data from the Rotterdam Study, while another (rs12414657 in ADRB1) was validated in females using data from the MOFS. We performed an exploratory meta-analysis of all 5 studies for these variations, which further validated our findings.

CONCLUSION

This analysis provides a starting point for investigating the pharmacogenomic effects of BB use on BMD measures.

Ser49Gly Beta1-Adrenergic Receptor Genetic Polymorphism as a Death Predictor in Brazilian Patients with Heart Failure

Background The role of Ser49Gly beta1-adrenergic receptor genetic polymorphism (ADBR1-GP-Ser49Gly) as a predictor of death in heart failure (HF) is not established for the Brazilian population. Objectives To evaluate the association between ADBR1-GP-Ser49Gly and clinical outcomes in individuals with HF with reduced ejection fraction. Methods Secondary analysis of medical records of 178 patients and genotypes of GPRβ1-Ser49Gly variants, classified as Ser-Ser, Ser-Gly and Gly-Gly. To evaluate their association with clinical outcome. A significance level of 5% was adopted. Results Cohort means were: clinical follow-up 6.7 years, age 63.5 years, 64.6% of men and 55.1% of whites. HF etiologies were predominantly ischemic (31.5%), idiopathic (23.6%) and hypertensive (15.7%). The genetic profile was distributed as follows: 122 Ser-Ser (68.5%), 52 Ser-Gly (28.7%) and 5 Gly-Gly (2.8%). There was a significant association between these genotypes and mean NYHA functional class at the end of follow-up (p = 0.014) with Gly-Gly being associated with less advanced NYHA. In relation to the clinical outcomes, there was a significant association (p = 0.026) between mortality and GPRβ1-Ser49Gly: the number of deaths in patients with Ser-Gly (12) or Gly-Gly (1) was lower than in those with Ser-Ser (54). The Gly allele had an independent protective effect maintained after multivariate analysis and was associated with a reduction of 63% in the risk of death (p = 0.03; Odds Ratio 0.37 - CI 0.15-0.91). Conclusion The presence of β1-AR-GP Gly-Gly was associated with better clinical outcome evaluated by NYHA functional class and was a predictor of lower risk of mortality, regardless of other factors, in a 6.7-year of follow-up. (Arq Bras Cardiol. 2020; 114(4):613-615).

Quantitative trait loci associated with angiotensin II and high-salt diet induced acute decompensated heart failure in Balb/CJ mice

Genetic background of different mouse strains determines their susceptibility to disease. We have previously shown that Balb/CJ and C57BL/6J mice develop cardiac hypertrophy to the same degree when treated with a combination of angiotensin II and high-salt diet (ANG II+Salt), but only Balb/CJ show impaired cardiac function associated with edema development and substantial mortality. We hypothesized that the different response to ANG II+Salt is due to the different genetic backgrounds of Balb/CJ and C57BL/6J. To address this we performed quantitative trait locus (QTL) mapping of second filial generation (F2) of mice derived from a backcross between Balb/CJ and first filial generation (F1) of mice. Cardiac function was measured with echocardiography, glomerular filtration rate using FITC-inulin clearance, fluid and electrolyte balance in metabolic cages, and blood pressure with tail-cuff at baseline and on the fourth day of treatment with ANG II+Salt. A total of nine QTLs were found to be linked to different phenotypes in ANG II+Salt-treated F2 mice. A QTL on chromosome 3 was linked to cardiac output, and a QTL on chromosome 12 was linked to isovolumic relaxation time. QTLs on chromosome 2 and 3 were linked to urine excretion and sodium excretion. Eight genes located at the different QTLs contained coding nonsynonymous SNPs published in the mouse genome database that differ between Balb/CJ and C57BL/6J. In conclusion, ANG II+Salt-induced acute decompensation in Balb/CJ is genetically linked to several QTLs, indicating a multifaceted phenotype. The present study identified potential candidate genes that may represent important pathways in acute decompensated heart failure.

β1-Adrenoreceptor Polymorphisms and Blood Pressure: 49S Variant Increases Plasma Renin But Not Blood Pressure in Hypertensive Patients

BACKGROUND

Activation of beta-1 adrenoreceptor (β1-AR) in the kidney releases renin that plays a major role in the maintenance of blood pressure. Genetic variation in β1-AR could therefore alter the physiological and clinical effects of this hormone. We tested this hypothesis in patients from a primary care cohort being screened for primary hyperaldosteronism (n = 467).

METHODS

Demographic and hemodynamic data were measured and plasma renin was determined by a standard immunoassay. Subjects were genotyped for the 2 common single-nucleotide polymorphisms Arg389Gly (rs1801253) and Ser49Gly (rs1801252), and thus the 4 possible haplotypes in β1-AR gene.

RESULTS

In patients being screened for hyperaldosteronism, plasma renin was significantly elevated in Ser49 homozygotes (49SS) compared with Gly49 (49G) allele carriers (0.307 ± 0.03 vs. 0.164 ± 0.05; P = 0.01). However, this did not translate into differences in either blood pressure or heart rate. On the other hand, the Arg389Gly polymorphism did not affect either plasma renin or blood pressure in this group. There was also no evidence that the 2 loci were linked in this group of patients.

CONCLUSION

These data suggest that in this cohort the Ser49 variant of the Ser49Gly β1-AR gene polymorphism associates with higher renin levels. However, these common β1-AR gene polymorphisms do not affect blood pressure in the same cohort.

β-Adrenergic Receptor Signaling and Heart Failure: From Bench to Bedside

Despite improvements in management and therapeutic approach in the last decades, heart failure is still associated with high mortality rates. The sustained enhancement in the sympathetic nervous system tone, observed in patients with heart failure, causes alteration in β-adrenergic receptor signaling and function. This latter phenomenon is the result of several heart failure-related molecular abnormalities involving adrenergic receptors, G-protein-coupled receptor kinases, and β-arrestins. This article summarizes novel encouraging preclinical strategies to reactivate β-adrenergic receptor signaling in heart failure, including pharmacologic and gene therapy approaches, and attempts to translate acquired notions into the clinical setting.

Association of Genetic Polymorphisms in the Beta-1 Adrenergic Receptor with Recovery of Left Ventricular Ejection Fraction in Patients with Heart Failure

Two common genetic polymorphisms in the beta-1 adrenergic receptor (ADRB1 Ser49Gly [rs1801252] and Arg389Gly [rs1801253]) significantly affect receptor function in vitro. The objective of this study was to determine whether ADRB1 Ser49Gly and Arg389Gly are associated with recovery of left ventricular ejection fraction (LVEF) in patients with heart failure. Patients with heart failure and baseline LVEF ≤ 40% were genotyped (n = 98), and retrospective chart review assessed the primary outcome of LVEF recovery to ≥ 40%. Un/adjusted logistic regression models revealed that Ser49Gly, but not Arg389Gly, was significantly associated with LVEF recovery in a dominant genetic model. The adjusted odds ratio for Ser49 was 8.2 (95% CI = 2.1-32.9; p = 0.003), and it was the strongest predictor of LVEF recovery among multiple clinical variables. In conclusion, patients with heart failure and reduced ejection fraction that are homozygous for ADRB1 Ser49 were significantly more likely to experience LVEF recovery than Gly49 carriers.

Influence of Beta-1 Adrenergic Receptor Genotype on Cardiovascular Response to Exercise in Healthy Subjects

Background

The beta-1 adrenergic receptor (ADRB1) has been shown to play a functional role in cardiomyocyte function and accounts for up to 80% of the cardiac tissue adrenergic receptors with ADRB1 stimulation increasing cardiac rate, contractility and work. Multiple polymorphisms of the ADRB1 have been identified such as the Gly49 polymorphism that includes at least one glycine (Gly) for serine (Ser) at amino acid 49 resulting in either homozygous for Gly (Gly49Gly) or heterozygous for Gly (Gly49Ser) polymorphisms. Heart failure patients with this polymorphism (Gly49) have been shown to have improved cardiac function and decreased mortality risk, but if there is an effect in healthy subjects is less clear. The purpose of this study was to determine the effects of the Gly/Ser polymorphism at position 49 of the ADRB1on the cardiovascular response to exercise in healthy subjects.

Methods

We performed genotyping of the ADRB1 (amino acid 49) and high-intensity, steady-state exercise on 71 healthy subjects (Ser49Ser = 52, Gly49Ser = 19).

Results

There were no differences between genotype groups in age, height, weight, body mass index (BMI), or watts achieved (age = 28.9 ± 5.6 years (yrs.), 30.6 ± 6.4yrs., height = 173.6 ± 9.9 cm, 174 ± 7.5 cm, weight = 74.4 ± 13.3 kg, 71.9 ± 13.5 kg, BMI = 24.6 ± 3.5, 23.6 ± 3.3, and watts = 223.8 ± 76.8, 205 ± 49.4, for Ser49Ser and Gly49Ser respectively). Additionally, there were no differences for genotype groups for cardiac output (CO), systolic blood pressure (BP_sys), or diastolic blood pressure (BP_dias) at rest, maximal exercise, or in change from rest to maximal exercise. The genotype groups differed significantly in heart rate (HR_max) at maximal exercise and cardiac index at rest (CI) (HR_max = 184.2 ± 9.5 bpm, 190.7 ± 10.6 bpm, CI = 0.063 ± 0.014, 0.071 ± 0.013, for Ser49Ser and Gly49Ser respectively). There was a trend towards significance (P = 0.058) for the change in stroke volume from rest to peak exercise (ΔSV) (0.016 ± 0.018 L, 0.0076 ± 0.012 L, for Ser49Ser and Gly49Ser respectively).

Conclusions

These data suggest genetic variations of the ADRB1 may influence cardiovascular responses to exercise in healthy subjects.

Site-specific O-Glycosylation by Polypeptide N-Acetylgalactosaminyltransferase 2 (GalNAc-transferase T2) Co-regulates β1-Adrenergic Receptor N-terminal Cleavage

The β1-adrenergic receptor (β1AR) is a G protein-coupled receptor (GPCR) and the predominant adrenergic receptor subtype in the heart, where it mediates cardiac contractility and the force of contraction. Although it is the most important target for β-adrenergic antagonists, such as β-blockers, relatively little is yet known about its regulation. We have shown previously that β1AR undergoes constitutive and regulated N-terminal cleavage participating in receptor down-regulation and, moreover, that the receptor is modified by O-glycosylation. Here we demonstrate that the polypeptide GalNAc-transferase 2 (GalNAc-T2) specifically O-glycosylates β1AR at five residues in the extracellular N terminus, including the Ser-49 residue at the location of the common S49G single-nucleotide polymorphism. Using in vitro O-glycosylation and proteolytic cleavage assays, a cell line deficient in O-glycosylation, GalNAc-T-edited cell line model systems, and a GalNAc-T2 knock-out rat model, we show that GalNAc-T2 co-regulates the metalloproteinase-mediated limited proteolysis of β1AR. Furthermore, we demonstrate that impaired O-glycosylation and enhanced proteolysis lead to attenuated receptor signaling, because the maximal response elicited by the βAR agonist isoproterenol and its potency in a cAMP accumulation assay were decreased in HEK293 cells lacking GalNAc-T2. Our findings reveal, for the first time, a GPCR as a target for co-regulatory functions of site-specific O-glycosylation mediated by a unique GalNAc-T isoform. The results provide a new level of β1AR regulation that may open up possibilities for new therapeutic strategies for cardiovascular diseases.

Genetics and genomics of dilated cardiomyopathy and systolic heart failure

Heart failure is a major health burden, affecting 40 million people globally. One of the main causes of systolic heart failure is dilated cardiomyopathy (DCM), the leading global indication for heart transplantation. Our understanding of the genetic basis of both DCM and systolic heart failure has improved in recent years with the application of next-generation sequencing and genome-wide association studies (GWAS). This has enabled rapid sequencing at scale, leading to the discovery of many novel rare variants in DCM and of common variants in both systolic heart failure and DCM. Identifying rare and common genetic variants contributing to systolic heart failure has been challenging given its diverse and multiple etiologies. DCM, however, although rarer, is a reasonably specific and well-defined condition, leading to the identification of many rare genetic variants. Truncating variants in titin represent the single largest genetic cause of DCM. Here, we review the progress and challenges in the detection of rare and common variants in DCM and systolic heart failure, and the particular challenges in accurate and informed variant interpretation, and in understanding the effects of these variants. We also discuss how our increasing genetic knowledge is changing clinical management. Harnessing genetic data and translating it to improve risk stratification and the development of novel therapeutics represents a major challenge and unmet critical need for patients with heart failure and their families.

Towards Precision in HF Pharmacotherapy

PURPOSE OF REVIEW

Heart failure (HF) is a disease state with great heterogeneity, which complicates the therapeutic process. Identifying more precise HF phenotypes will allow for the development of more targeted therapies and improvement in patient outcomes. This review explores the future for precision medicine in HF treatment.

RECENT FINDINGS

Rather than a continuous disease spectrum with a uniform pathogenesis, HF has phenotypes with different underlying pathophysiologic features. The challenge is to establish clinical phenotypic characterizations to direct therapy. Phenomapping, a process of using machine learning algorithms applied to clinical data sets, has been used to identify phenotypically distinct and clinically meaningful HF groups. As powerful technologies extend our knowledge, future analyses may be able to compile more comprehensive phenotypic profiles using genetic, epigenetic, proteomic, and metabolomic measurements. Identifying clinical characterizations of particular HF patients that would be uniquely or disproportionately responsive to a specific treatment would allow for more direct selection of optimal therapy, reduce trial-and-error prescribing, and help avoid adverse drug reactions.

Evolution of the β-adrenoreceptors in vertebrates

The study of the evolutionary history of genes related to human disease lies at the interface of evolution and medicine. These studies provide the evolutionary context on which medical researchers should work, and are also useful in providing information to suggest further genetic experiments, especially in model species where genetic manipulations can be made. Here we studied the evolution of the β-adrenoreceptor gene family in vertebrates with the aim of adding an evolutionary framework to the already abundant physiological information. Our results show that in addition to the three already described vertebrate β-adrenoreceptor genes there is an additional group containing cyclostome sequences. We suggest that β-adrenoreceptors diversified as a product of the two whole genome duplications that occurred in the ancestor of vertebrates. Gene expression patterns are in general consistent across species, suggesting that expression dynamics were established early in the evolutionary history of vertebrates, and have been maintained since then. Finally, amino acid polymorphisms that are associated to pathological conditions in humans appear to be common in non-human mammals, suggesting that the phenotypic effects of these mutations depend on epistatic interaction with other positions. The evolutionary analysis of the β-adrenoreceptors delivers new insights about the diversity of these receptors in vertebrates, the evolution of the expression patterns and a comparative perspective regarding the polymorphisms that in humans are linked to pathological conditions.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

The influence of clinical and genetic factors on left ventricular wall thickness in Ragdoll cats

OBJECTIVES

To investigate the effect of various genetic and environmental modifiers on left ventricular (LV) wall thickness in a cohort of cats genotyped for the myosin binding protein C3 mutation (MYBPC3).

ANIMALS

Sixty-four Ragdoll cats.

METHODS

All cats were screened for HCM with echocardiography and genotyping for the HCM-associated MYBPC3:R820W mutation. Cats were also genotyped for previously identified variant polymorphisms of the angiotensin-converting enzyme (ACE) and cardiac beta-adrenergic receptor (ADRB1) genes. Plasma N-terminal pro-B-type natriuretic peptide and cardiac troponin I were also measured. Associations were evaluated between genotype (MYBPC3 negative/positive, and ACE and ADRB1 negative/heterozygous/homozygous), patient factors (body weight, age and sex) and echocardiographic measurements of LV wall thickness.

RESULTS

Male cats had greater maximum wall thickness (LVmax; 5.8 mm, IQR 5.1-6.4 mm) than females (4.7 mm, IQR 4.4-5.3 mm, p = 0.002). Body weight positively correlated with LVmax (ρ = 0.604, p < 0.001). The MYBPC3:R820W-positive cats had a greater LVmax (5.44 mm, IQR 4.83-6.28 mm) than the negative cats (4.76 mm, IQR 4.36-5.32 mm, p = 0.001). Also, the ACE polymorphism genotype was associated with LVmax: the homozygous cats (5.37 mm, IQR 5.14-6.4 mm) had greater LVmax than the heterozygous cats (4.73 mm, IQR 4.41-5.55 mm, p = 0.014). Only the MYBPC3 genotype and body weight were independently associated with wall thickness in multivariable analysis.

CONCLUSIONS

This study provides evidence that the MYBPC3:R820W mutation is independently associated with LV wall thickness in Ragdoll cats. Body weight is also independently associated with maximum LV wall thickness, but is not currently accounted for in HCM screening. In addition, other genetic modifiers may be associated with variation in LV wall thickness in Ragdolls.

Association between Beta1 -Adrenergic Receptor Polymorphism and Risk of ICD Shock in Heart Failure Patients

BACKGROUND

Sympathetic activation in heart failure patients favors the development of ventricular arrhythmias, thus leading to an increased risk of sudden cardiac death. β1 - and β2 -adrenergic receptor polymorphisms have been linked to the risk of sudden death. Implantable cardioverter-defibrillators (ICD) are implanted in a large percentage of heart failure patients, and beyond preventing sudden cardiac death they provide a continuous monitoring of major ventricular arrhythmias and of their own interventions. We investigated whether functionally relevant β1 - and β2 -adrenergic receptor polymorphisms are associated with risk of ICD shocks, as evidenced in ICD memory.

METHODS

311 patients with systolic heart failure were enrolled, and number and timing of shocks in ICD memory were recorded. Four selected polymorphisms were determined: β1 -adrenergic receptor polymorphisms Ser(49) Gly and Arg(389) Gly and β2 -adrenergic receptor polymorphisms Arg(16) Gly and Gln(27) Glu.

RESULTS

Only Ser(49) Gly was significantly correlated with time free from ICD shocks, both considering time to the first event in a Cox model (hazard ratio 2.117), and modeling repeated events with the Andersen-Gill method (hazard ratio 2.088). Gly allele carriers had a higher probability of ICD shock. The relationship remained significant even after adjusting for ejection fraction and beta-blocker dosage (hazard ratio 1.910).

CONCLUSIONS

Data from our study suggest that the β adrenoreceptor Gly 49 allele of the β1 -adrenergic receptor Ser(49) Gly polymorphisms may increase the risk of ICD shock in patients with heart failure, independent of beta-blocker dosage.

Impact of the β-1 adrenergic receptor polymorphism on tolerability and efficacy of bisoprolol therapy in Korean heart failure patients: association between β adrenergic receptor polymorphism and bisoprolol therapy in heart failure (ABBA) study

BACKGROUND/AIMS

We evaluated the association between coding region variants of adrenergic receptor genes and therapeutic effect in patients with congestive heart failure (CHF).

METHODS

One hundred patients with stable CHF (left ventricular ejection fraction [LVEF] < 45%) were enrolled. Enrolled patients started 1.25 mg bisoprolol treatment once daily, then up-titrated to the maximally tolerable dose, at which they were treated for 1 year.

RESULTS

Genotypic analysis was carried out, but the results were blinded to the investigators throughout the study period. At position 389 of the β-1 adrenergic receptor gene (ADRB1), the observed minor Gly allele frequency (Gly389Arg + Gly389Gly) was 0.21, and no deviation from Hardy-Weinberg equilibrium was observed in the genotypic distribution of Arg389Gly (p = 0.75). Heart rate was reduced from 80.8 ± 14.3 to 70.0 ± 15.0 beats per minute (p < 0.0001). There was no significant difference in final heart rate across genotypes. However, the Arg389Arg genotype group required significantly more bisoprolol compared to the Gly389X (Gly389Arg + Gly389Gly) group (5.26 ± 2.62 mg vs. 3.96 ± 2.05 mg, p = 0.022). There were no significant differences in LVEF changes or remodeling between two groups. Also, changes in exercise capacity and brain natriuretic peptide level were not significant. However, interestingly, there was a two-fold higher rate of readmission (21.2% vs. 10.0%, p = 0.162) and one CHF-related death in the Arg389Arg group.

CONCLUSIONS

The ADRB1 Gly389X genotype showed greater response to bisoprolol than the Arg389Arg genotype, suggesting the potential of individually tailoring β-blocker therapy according to genotype.

Genetic polymorphisms associated with heart failure: A literature review

Objective

To review possible associations reported between genetic variants and the risk, therapeutic response and prognosis of heart failure.

Methods

Electronic databases (PubMed, Web of Science and CNKI) were systematically searched for relevant papers, published between January 1995 and February 2015.

Results

Eighty-two articles covering 29 genes and 39 polymorphisms were identified.

Conclusion

Genetic association studies of heart failure have been highly controversial. There may be interaction or synergism of several genetic variants that together result in the ultimate pathological phenotype for heart failure.

The future of pharmacogenetics in the treatment of heart failure

Heart failure is a common disease with high levels of morbidity and mortality. Current treatment comprises β-blockers, ACE inhibitors, aldosterone antagonists and diuretics. Variation in clinical response seen in patients begs the question of whether there is a pharmacogenetic component yet to be identified. To date, the genes most studied involve the β-1, β-2, α-2 adrenergic receptors and the renin-angiotensin-aldosterone pathway, mainly focusing on SNPs. However results have been inconsistent. Genome-wide association studies and next-generation sequencing are seen as alternative approaches to discovering genetic variations influencing drug response. Hopefully future research will lay the foundations for genotype-led drug management in these patients with the ultimate aim of improving their clinical outcome.

The Genetic Challenges and Opportunities in Advanced Heart Failure

The causes of heart failure are diverse. Inherited causes represent an important clinical entity and can be divided into 2 major categories: familial and metabolic cardiomyopathies. The distinct features that might be present in early disease states can become broadly overlapping with other diseases, such as in the case of inherited cardiomyopathies (ie, familial hypertrophic cardiomyopathy or mitochondrial diseases). In this review article, we focus on genetic issues related to advanced heart failure. Because of the emerging importance of this topic and its breadth, we sought to focus our discussion on the known genetic forms of heart failure syndromes, genetic testing, and newer data on pharmacogenetics and therapeutics in the treatment of heart failure, to primarily encourage clinicians to place a priority on the diagnosis and treatment of these potentially treatable conditions.

SH2B3 Is a Genetic Determinant of Cardiac Inflammation and Fibrosis

BACKGROUND

Genome-wide association studies are powerful tools for nominating pathogenic variants, but offer little insight as to how candidate genes affect disease outcome. Such is the case for SH2B adaptor protein 3 (SH2B3), which is a negative regulator of multiple cytokine signaling pathways and is associated with increased risk of myocardial infarction (MI), but its role in post-MI inflammation and fibrosis is completely unknown.

METHODS AND RESULTS

Using an experimental model of MI (left anterior descending artery occlusion/reperfusion injury) in wild-type and Sh2b3 knockout rats (Sh2b3(em2Mcwi)), we assessed the role of Sh2b3 in post-MI fibrosis, leukocyte infiltration, angiogenesis, left ventricle contractility, and inflammatory gene expression. Compared with wild-type, Sh2b3(em2Mcwi) rats had significantly increased fibrosis (2.2-fold; P<0.05) and elevated leukocyte infiltration (>2-fold; P<0.05), which coincided with decreased left ventricle fractional shortening (-Δ11%; P<0.05) at 7 days post left anterior descending artery occlusion/reperfusion injury. Despite an increased angiogenic potential in Sh2b3(em2Mcwi) rats (1.7-fold; P<0.05), we observed no significant differences in left ventricle capillary density between wild-type and Sh2b3(em2Mcwi) rats. In total, 12 genes were significantly elevated in the post left anterior descending artery occluded/reperfused hearts of Sh2b3(em2Mcwi) rats relative to wild-type, of which 3 (NLRP12, CCR2, and IFNγ) were significantly elevated in the left ventricle of heart failure patients carrying the MI-associated rs3184504 [T] SH2B3 risk allele.

CONCLUSIONS

These data demonstrate for the first time that SH2B3 is a crucial mediator of post-MI inflammation and fibrosis.

Pharmacogenomics in heart failure: where are we now and how can we reach clinical application?

Heart failure is becoming increasingly prevalent in the United States and is a significant cause of morbidity and mortality. Several therapies are currently available to treat this chronic illness; however, clinical response to these treatment options exhibit significant interpatient variation. It is now clearly understood that genetics is a key contributor to diversity in therapeutic response, and evidence that genetic polymorphisms alter the pharmacokinetics, pharmacodynamics, and clinical response of heart failure drugs continues to accumulate. This suggests that pharmacogenomics has the potential to help clinicians improve the management of heart failure by choosing the safest and most effective medications and doses. Unfortunately, despite much supportive data, pharmacogenetic optimization of heart failure treatment regimens is not yet a reality. In order to attenuate the rising burden of heart failure, particularly in the context of the recent paucity of new effective interventions, there is an urgent need to extend pharmacogenetic knowledge and leverage these associations in order to enhance the effectiveness of existing heart failure therapies. This review focuses on the current state of pharmacogenomics in heart failure and provides a glimpse of the aforementioned future needs.

Polymorphisms of β 1-adrenoreceptor gene and cardiovascular complications in patients with thyrotoxicosis

Human cardiac β1-AR perform a crucial role in mediating the cardiostimulating effects of norepinephrine. Gly389Arg and Ser49Gly polymorphisms of β1-adrenoreceptors (β1-AR) can influence the cardiovascular prognosis. However, the possible effect of Gly389Arg and Ser49Gly polymorphisms on heart function in thyrotoxicosis has not been studied. We investigated the possible link between Gly389Arg and Ser49Gly polymorphisms and echocardiography parameters in 165 normotensive patients with a thyrotoxicosis without any cardiovascular disorders. Echo-CG was performed according to standard protocol before and during the thyreostatic treatment. Our data demonstrate that both Gly389Arg and Ser49Gly polymorphisms have very moderate influence on the risk of left ventricular hypertrophy and atrial fibrillation with no statistically significant effects on cardiac function and the development of cardiovascular complications.

Pharmacogenomics of heart failure

The combination of angiotensin-converting enzyme (ACE) inhibitors and β-adrenergic receptor (βAR) blockers remains the essential component of heart failure (HF) pharmacotherapy. However, individual patient responses to these pharmacotherapies vary widely. The variability in response cannot be explained entirely by clinical characteristics, and genetic variation may play a role. The purpose of this chapter is to examine the current knowledge in the field of beta-blocker and ACE inhibitor pharmacogenetics in HF. β-blocker and ACE inhibitor pharmacogenetic studies performed in patients with HF were identified from the PubMed database from 1966 to July 2011. Thirty beta-blocker and 10 ACE inhibitor pharmacogenetic studies in patients with HF were identified.The ACE deletion variant was associated with greater survival benefit from ACE inhibitors and beta-blockers compared with the ACE insertion. Ser49 in the β1AR, the insertion in the α2CAR, and Gln41 in G protein-coupled receptor (GPCR) kinase (GRK)-5 are associated with greater survival benefit from β-blockers, compared with Gly49, the deletion, and Leu41, respectively. However, many of these associations have not been validated. The HF pharmacogenetic literature is still in its very early stages, but there are promising candidate genetic variants that may identify which HF patients are most likely to benefit from beta-blockers and ACE inhibitors and patients that may require additional therapies.

A novel approach to drug development in heart failure: towards personalized medicine

Evidence-based treatment has succeeded in improving clinical outcomes in heart failure. Nevertheless, morbidity, mortality, and the economic burden associated with the syndrome remain unsatisfactorily high. Most landmark heart failure studies included broad study populations, and thus current recommendations dictate standardized, universal therapy. While most patients included in recent trials benefit from this background treatment, exceeding this already significant gain has proven to be a challenge. The early identification of responders and nonresponders to treatment could result in improved therapeutic effectiveness, while reduction of unnecessary exposure may limit harmful and unpleasant side effects. In this review, we examine the potential value of currently available information on differential responses to heart failure therapy-a first step toward personalized medicine in the management of heart failure.

Impact of polymorphic variants on the molecular pharmacology of the two-agonist conformations of the human β1-adrenoceptor

β-blockers are widely used to improve symptoms and prolong life in heart disease primarily by inhibiting the actions of endogenous catecholamines at the β1-adrenoceptor. There are two common naturally occurring polymorphisms within the human β1-adrenoceptor sequence: Ser or Gly at position 49 in the N-terminus and Gly or Arg at position 389 in the C-terminus and some clinical studies have suggested that expression of certain variants may be associated with disease and affect response to treatment with β-blockers. The β1-adrenoceptor also exists in two agonist conformations - a high affinity catecholamine conformation and a low affinity secondary agonist conformation. Receptor-effector coupling and intracellular signalling from the different conformations may be affected by the polymorphic variants. Here, we examine in detail the molecular pharmacology of the β1-adrenoceptor polymorphic variants with respect to ligand affinity, efficacy, activation of the different agonist conformations and signal transduction and determine whether the polymorphic variants do indeed affect this secondary conformation. Stable cell lines expressing the wildtype and polymorphic variants were constructed and receptor pharmacology examined using whole cell binding and intracellular secondary messenger techniques. There was no difference in affinity for agonists and antagonists at the human wildtype β1-adrenoceptor (Ser49/Gly389) and the polymorphic variants Gly49/Gly389 and Ser49/Arg389. Furthermore, the polymorphic variant receptors both have two active agonist conformations with pharmacological properties similar to the wildtype receptor. Although the polymorphism at position 389 is thought to occur in an intracellular domain important for Gs-coupling, the two agonist conformations of the polymorphic variants stimulate intracellular signalling pathways, including Gs-cAMP intracellular signalling, in a manner very similar to that of the wildtype receptor.

Adrenergic nervous system in heart failure: pathophysiology and therapy

Heart failure (HF), the leading cause of death in the western world, develops when a cardiac injury or insult impairs the ability of the heart to pump blood and maintain tissue perfusion. It is characterized by a complex interplay of several neurohormonal mechanisms that become activated in the syndrome to try and sustain cardiac output in the face of decompensating function. Perhaps the most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are enormously elevated in HF. Acutely, and if the heart works properly, this activation of the ANS will promptly restore cardiac function. However, if the cardiac insult persists over time, chances are the ANS will not be able to maintain cardiac function, the heart will progress into a state of chronic decompensated HF, and the hyperactive ANS will continue to push the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, methods of measuring ANS activity in HF, the molecular alterations in heart physiology that occur in HF, along with their pharmacological and therapeutic implications, and, finally, drugs and other therapeutic modalities used in HF treatment that target or affect the ANS and its effects on the failing heart.

S49G and R389G polymorphisms of the β₁-adrenergic receptor influence signaling via the cAMP-PKA and ERK pathways

Two functionally important β1-adrenergic receptor (β1AR) polymorphisms have been identified. The R389G polymorphism influences coupling to the Gs-cAMP pathway. R(389)-β1ARs display enhanced activation of cAMP/PKA; they provide short-term inotropic support but also cause a predisposition to cardiomyopathic decompensation. A second S49G polymorphism is implicated in the evolution of heart failure, but the mechanism remains uncertain. This study shows that position 49 and 389 polymorphisms function in a coordinate manner to influence agonist-dependent cAMP/PKA and ERK responses. cAMP/PKA and ERK responses are more robust in HEK293 cells that heterologously overexpress G(49)-β1ARs, compared with S(49)-β1ARs. However, this phenotype is most obvious on a G(389)-β1AR background; the more robust agonist-dependent cAMP/PKA and ERK responses in R(389)-β1AR cells effectively obscure the effect of the S49G polymorphism. We also show that isoproterenol (Iso) and carvedilol activate ERK via a similar EGFR-independent mechanism in cells expressing various β1AR haplotypes. However, Iso activates ERK via an Src-independent pathway, but carvedilol-dependent ERK activation requires Src. Since the S49G polymorphism has been linked to changes in β1AR trafficking, we examined whether β1AR polymorphisms influence partitioning to lipid raft membranes. Biochemical fractionation studies show that all four β1AR variants are recovered in buoyant flotillin-enriched membranes; the distinct signaling phenotypes of the different β1AR variants could not be attributed to any gross differences in basal compartmentalization to lipid raft membranes. The allele-specific differences in β1AR signaling phenotypes identified in this study could underlie interindividual differences in responsiveness to β-blocker therapy and clinical outcome in heart failure.

Genetic prediction of heart failure incidence, prognosis and beta-blocker response

Heart failure (HF) is a widespread syndrome due to left ventricular dysfunction with high mortality, morbidity and health-care costs. Beta-blockers, together with diuretics and ACE-inhibitors or angiotensin receptor blockers, are a cornerstone of HF therapy, as they reduce mortality and morbidity. Nevertheless, their efficacy varies among patients, and genetics is likely to be one of the modifying factors. In this article, literature on the role of candidate genes on the development of HF, its prognosis and pharmacogenomics of β-blockers in patients with HF is reviewed. The available findings do not support, at the present time, a role for genetic tests in the treatment of HF. More large-scale genome-wide studies with adequate methodology and statistical analysis are required before considering genetic tailoring of HF therapy in patients with systolic HF.

[Molecular and genetic background of sudden cardiac death]

Despite recent findings on the functional, structural and genetic background of sudden cardiac death, the incidence is still relatively high in the entire population. A thorough knowledge on susceptibility, as well as pathophysiology behind the development of malignant arrhythmias will help us to identify individuals at risk and prevent sudden cardiac death. This article presents a review of the current literature on the role of altered intracellular Ca2+ handling, acute myocardial ischaemia, cardiac autonomic innervation, renin-angiotensin-aldosterone system, monogenic and complex heritability in the pathogenesis of sudden cardiac death.

Beta-adrenergic receptor polymorphisms and cardiac graft function in potential organ donors

Prior studies have demonstrated associations between beta-adrenergic receptor (βAR) polymorphisms and left ventricular dysfunction-an important cause of allograft nonutilization for transplantation. We hypothesized that βAR polymorphisms predispose donor hearts to LV dysfunction after brain death. A total of 1043 organ donors managed from 2001-2006 were initially studied. The following βAR single nucleotide polymorphisms were genotyped: β1AR 1165C/G (Arg389Gly), β1AR 145A/G (Ser49Gly), β2AR 46G/A (Gly16Arg) and β2AR 79C/G (Gln27Glu). In multivariable regression analyses, the β2AR46 SNP was significantly associated with LV systolic dysfunction, with each minor allele additively decreasing the odds for LV ejection fraction <50%. The β1AR1165 and β2AR46 SNPs were associated with higher dopamine requirement during the donor management period: donors with the GG and AA genotypes had ORs of 2.64 (95% CI 1.52-4.57) and 2.70 (1.07-2.74) respectively for requiring >10 μg/kg/min of dopamine compared to those with the CC and GG genotypes. However, no significant associations were found between βAR SNPs and cardiac dysfunction in 364 donors managed from 2007-2008, perhaps due to changes in donor management, lack of power in this validation cohort, or the absence of a true association. βAR polymorphisms may be associated with cardiac dysfunction after brain death, but these relationships require further study in independent donor cohorts.

β-adrenergic receptor polymorphisms in susceptibility, response to treatment and prognosis in heart failure: implication of ethnicity

Common functional polymorphisms in β-adrenergic receptor (βAR) genes have been associated with heart failure (HF) phenotypes and pharmacogenetic interactions with βAR blockers. This study evaluated the association between βAR polymorphisms and carvedilol drug response and prognosis in patients with HF. In this prospective cohort controlled study, 326 volunteers were enrolled [146 HF patients (ejection fraction (EF)<50% by Simpson) and 180 healthy controls]. Drug response was evaluated by echocardiography and outcomes were mortality and hospitalization. DNA was extracted from peripheral blood leukocytes, fragments were amplified by the polymerase reaction and genotyped by restriction fragment length polymorphism (RFLP) for Ser49Gly and Arg389Gly βAR-1 polymorphisms and Gln27Glu and Arg16Gly βAR-2 polymorphisms. The study population was in Hardy‑Weinberg equilibrium. The survival rate was adjusted using the Kaplan-Meier method. HF patients showed the following characteristics: EF 35±9%, 69.9% male, age 59±13 years, 50.7% self-identified as black, 46% had ischemic etiology. The mean follow-up of 23 months showed 18 mortalities and 46 hospitalizations. The genotypes Glu27Glu (24.7 vs. 6.1%, p=0.0004) and Arg16Arg (72.6 vs. 22.8, p<0.0001) of βAR2 polymorphisms and Gly49Gly (33.6 vs. 4.3%, p<0.0001) of the βAR1 polymorphism were higher in HF patients compared with controls. Patients with hospital admission showed a significantly higher Gly389 allelic frequency (54.9 vs. 42.1%, p=0.039), and the trend prevailed among patients who succumbed to the disease (61.1%, p=0.047). Black patients with the Ser49Ser genotype showed a reduced survival compared with the Gly49Gly or Ser49Gly genotypes (p=0.028). There was no association between improved LVEF >20% and βAR polymorphisms. HF patients with β-blocker therapy and the Gly389 allele have reduced event-free survival compared to those carrying the Arg389 allele. Additionally, systolic HF outpatients undergoing β-blocker therapy, self‑identified as black and homozygous for Ser49Ser may have reduced event-free survival, while Glu27Glu, Arg16Arg and Gly49Gly genotypes may be associated with risk for HF.

Pharmacogenetics in chronic heart failure: new developments and current challenges

The individual patient responses to chronic heart failure (HF) pharmacotherapies are highly variable. This variability cannot be entirely explained by clinical characteristics, and genetic variation may play a role. Therefore, this review will summarize the background pharmacogenetic literature for major HF pharmacotherapy classes (ie, β-blockers, angiotensin-converting enzyme inhibitors, digoxin, and loop diuretics), evaluate recent advances in the HF pharmacogenetic literature in the context of previous findings, and discuss the challenges and conclusions for HF pharmacogenetic data and its clinical application.

A common β1-adrenergic receptor polymorphism predicts favorable response to rate-control therapy in atrial fibrillation

OBJECTIVES

In this study, we evaluated the impact of 2 common β1-adrenergic receptor (β1-AR) polymorphisms (G389R and S49G) in response to ventricular rate control therapy in patients with atrial fibrillation (AF).

BACKGROUND

Randomized studies have shown that ventricular rate control is an acceptable treatment strategy in patients with AF. However, identification of patients who will adequately respond to rate-control therapy remains a challenge.

METHODS

We studied 543 subjects (63% men; age 61.8 ± 14 years) prospectively enrolled in the Vanderbilt AF registry and managed with rate-control strategy. A "responder" displayed adequate ventricular rate control based on the AFFIRM (Atrial Fibrillation Follow-Up Investigation of Rhythm Management) criteria: average heart rate (HR) at rest ≤80 beats/min; and maximum HR during a 6-min walk test ≤110 beats/min or average HR during 24-h Holter ≤100 beats/min.

RESULTS

A total of 295 (54.3%) patients met the AFFIRM criteria. Baseline clinical characteristics were similar in responders and nonresponders except for mean resting HR (76 ± 20 beats/min vs. 70 ± 15 beats/min; p < 0.01) and smoking (6% vs. 1%; p < 0.01). Multiple clinical variables (age, gender, hypertension) failed to predict response to rate-control therapy. By contrast, carriers of Gly variant at 389 were more likely to respond favorably to rate-control therapy; 60% versus 51% in the Arg389Arg genotype, p = 0.04. This association persisted after correction for multiple clinical factors (odds ratio: 1.42, 95% confidence interval: 1.00 to 2.03, p < 0.05). Among responders, subjects carrying the Gly389 variant required the lowest doses of rate-control medications; atenolol: 92 mg versus 68 mg; carvedilol: 44 mg versus 20 mg; metoprolol: 80 mg versus 72 mg; diltiazem: 212 mg versus 180 mg, and verapamil: 276 mg versus 200 mg, respectively (p < 0.01 for all comparisons).

CONCLUSIONS

We have identified a common β1-AR polymorphism, G389R, that is associated with adequate response to rate-control therapy in AF patients. Gly389 is a loss-of-function variant; consequently, for the same adrenergic stimulation, it produces reduced levels of adenyl cyclase, and hence, attenuates the β-adrenergic cascade. Mechanistically, the effect of rate-control drugs will be synergistic with that of the Gly389 variant, which could possibly explain our findings. These findings represent a step forward in the development of a long-term strategy of selecting treatment options in AF based on genotype.

Genetic tailoring of pharmacotherapy in heart failure: optimize the old, while we wait for something new

BACKGROUND

The combination of angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic receptor blockers remains the essential component of heart failure (HF) pharmacotherapy. However, individual patient responses to these pharmacotherapies vary widely. The variability in response cannot be explained entirely by clinical characteristics, and genetic variation may play a role. The purpose of this review is to examine our current state of understanding of beta-blocker and ACE inhibitor pharmacogenetics in HF.

METHODS AND RESULTS

Beta-blocker and ACE inhibitor pharmacogenetic studies performed in patients with HF were identified from the Pubmed database from 1966 to July 2011. Thirty beta-blocker and 10 ACE inhibitor pharmacogenetic studies in patients with HF were identified. The ACE deletion variant was associated with greater survival benefit from ACE inhibitors and beta-blockers compared with the ACE insertion. Ser49 in the beta-1 adrenergic receptor, the insertion in the alpha-2C adrenergic receptor, and Gln41 in G-protein-coupled receptor kinase 5 are associated with greater survival benefit from beta-blockers, compared with Gly49, the deletion, and Leu41, respectively. However, many of these associations have not been validated.

CONCLUSIONS

The HF pharmacogenetic literature is still in its very early stages, but there are promising candidate genetic variants that may identify which HF patients are most likely to benefit from beta-blockers and ACE inhibitors and patients that may require additional therapies.

Beta receptor-mediated modulation of the late positive potential in humans

RATIONALE

Electrophysiological studies have identified a scalp potential, the late positive potential (LPP), which is modulated by the emotional intensity of observed stimuli. Previous work has shown that the LPP reflects the modulation of activity in extrastriate visual cortical structures, but little is known about the source of that modulation.

OBJECTIVES

The present study investigated whether beta-adrenergic receptors are involved in the generation of the LPP.

METHODS

We used a genetic individual differences approach (experiment 1) and a pharmacological manipulation (experiment 2) to test the hypothesis that the LPP is modulated by the activation of β-adrenergic receptors.

RESULTS

In experiment 1, we found that LPP amplitude depends on allelic variation in the β1-receptor gene polymorphism. In experiment 2, we found that LPP amplitude was modulated by the β-blocker propranolol in a direction dependent on subjects' level of trait anxiety: In participants with lower trait anxiety, propranolol led to a (nonsignificant) decrease in the LPP modulation; in participants with higher trait anxiety, propranolol increased the emotion-related LPP modulation.

CONCLUSIONS

These results provide initial support for the hypothesis that the LPP reflects the downstream effects, in visual cortical areas, of β-receptor-mediated activation of the amygdala.

Cardiovascular pharmacogenetics

Human genetic variation in the form of single nucleotide polymorphisms as well as more complex structural variations such as insertions, deletions and copy number variants, is partially responsible for the clinical variation seen in response to pharmacotherapeutic drugs. This affects the likelihood of experiencing adverse drug reactions and also of achieving therapeutic success. In this paper, we review key studies in cardiovascular pharmacogenetics that reveal genetic variations underlying the outcomes of drug treatment in cardiovascular disease. Examples of genetic associations with drug efficacy and toxicity are described, including the roles of genetic variability in pharmacokinetics (e.g. drug metabolizing enzymes) and pharmacodynamics (e.g. drug targets). These findings have functional implications that could lead to the development of genetic tests aimed at minimizing drug toxicity and optimizing drug efficacy in cardiovascular medicine.

The effect of beta1-adrenergic receptor gene polymorphism on prolongation of corrected QT interval during endotracheal intubation under sevoflurane anesthesia

Background

The hemodynamic responses to endotracheal intubation are associated with sympathoadrenal activity. Polymorphisms in the beta1-adrenergic receptor (β₁AR) gene can alter the pathophysiology of specific diseases. The aim of this study is to investigate whether the Ser49Gly and Arg389Gly polymorphism of the β₁AR gene have different cardiovascular responses during endotracheal intubation under sevoflurane anesthesia.

Methods

Ninety-one healthy patients undergoing general anesthesia were enrolled. Patients underwent slow inhalation induction of anesthesia using sevoflurane in 100% oxygen. Vecuronium 0.15 mg/kg was given for muscle relaxation. Endotracheal intubation was performed by an anesthesiologist. The mean arterial pressure (MAP), heart rate (HR), and the corrected QT (QTc) interval were measured before induction, before laryngoscopy, and immediately after tracheal intubation. Genomic DNA was isolated from the patients' peripheral blood and then evaluated for the β₁AR-49 and β₁AR-389 genes using an allele-specific polymerase chain reaction method.

Results

No differences were found in the baseline values of MAP, HR, and the QTc interval among β₁AR-49 and β₁AR-389, respectively. In the case of β₁AR-49, the QTc interval change immediately after tracheal intubation was significantly greater in Ser/Ser genotypes than in Ser/Gly genotypes. No differences were observed immediately after tracheal intubation in MAP and HR for β₁AR-49 and β₁AR-389.

Conclusions

We found an association between the Ser49 homozygote gene of β₁AR-49 polymorphism and increased QTc prolongation during endotracheal intubation with sevoflurane anesthesia. Thus, β₁AR-49 polymorphism may be useful in predicting the risk of arrhythmia during endotracheal intubation in patients with long QT syndrome.