Role of beta adrenergic receptor polymorphisms in heart failure: systematic review and meta-analysis

Genetic Variants of Adrenoceptors

Adrenoceptors are class A G-protein-coupled receptors grouped into three families (α1-, α2-, and β-adrenoceptors), each one including three members. All nine corresponding adrenoceptor genes display genetic variation in their coding and adjacent non-coding genomic region. Coding variants, i.e., nucleotide exchanges within the transcribed and translated receptor sequence, may result in a difference in amino acid sequence thus altering receptor function and signaling. Such variants have been intensely studied in vitro in overexpression systems and addressed in candidate-gene studies for distinct clinical parameters. In recent years, large cohorts were analyzed in genome-wide association studies (GWAS), where variants are detected as significant in context with specific traits. These studies identified two of the in-depth characterized 18 coding variants in adrenoceptors as repeatedly statistically significant genetic risk factors - p.Arg389Gly in the β1- and p.Thr164Ile in the β2-adrenoceptor, along with 56 variants in the non-coding regions adjacent to the adrenoceptor gene loci, the functional role of which is largely unknown at present. This chapter summarizes current knowledge on the two coding variants in adrenoceptors that have been consistently validated in GWAS and provides a prospective overview on the numerous non-coding variants more recently attributed to adrenoceptor gene loci.

MiR-133b as a crucial regulator of TCS-induced cardiotoxicity via activating β-adrenergic receptor signaling pathway in zebrafish embryos

As a commonly used antibacterial agent in daily consumer products, triclosan (TCS) has attracted significant attention due to its potential environmental risks. In this study, we investigated the toxic effects of TCS exposure (1.4 μM) on heart development in zebrafish embryos. Our findings revealed that TCS exposure caused significant cardiac dysfunction, characterized by pericardial edema, malformations in the heart structure, and a slow heart rate. Additionally, TCS exposure induced oxidative damage and abnormal apoptosis in heart cells through the up-regulation of β-adrenergic receptor (β-AR) signaling pathway genes (adrb1, adrb2a, arrb2b), similar to the effects induced by β-AR agonists. Notably, the adverse effects of TCS exposure were alleviated by β-AR antagonists. Using high-throughput transcriptome miRNA sequencing and targeted miRNA screening, we focused on miR-133b, which targets adrb1 and was down-regulated by TCS exposure, as a potential contributor to TCS-induced cardiotoxicity. Inhibition of miR-133b produced similar toxic effects as TCS exposure, while overexpression of miR-133b down-regulated the β-AR signaling pathway and rescued heart defects caused by TCS. In summary, our findings provide new insights into the mechanisms underlying the cardiotoxic effects of TCS. We suggest that targeting the β-AR pathway and miR-133b may be effective strategies for pharmacotherapy in cardiotoxicity induced by environmental pollutants such as TCS.

Influence of β1 Adrenergic Receptor Genotype on Longitudinal Measures of Left Ventricular Ejection Fraction and Responsiveness to ß-Blocker Therapy in Patients With Duchenne Muscular Dystrophy

The purpose of this study was to determine whether the longitudinal progression of decline in left ventricular ejection fraction (LVEF) in Duchenne muscular dystrophy (DMD) patients is moderated by ADRB1 genotype and whether the efficacy of ß-blocker therapy is influenced by genotype status. About 147 DMD patients (6-34 years.) were analyzed with a focus on β1 adrenergic receptor (ADRB1) genotype variants. Patients were grouped by ADRB1 genotype resulting in Gly389 patients and Arg389 patients. A generalized additive mixed effects model was used to examine differences in the nonlinear trend of LVEF across patient ages between genotype groups and for ß-blocker use. Both genotype groups displayed a progressive decline in LVEF starting around the mean age of ambulation loss (~12 years). However, there was no difference between genotype groups in the progression of decline in LVEF. There was a significant effect of ß-blocker use on longitudinal LVEF, wherein patients on ß-blockers had systematically lower LVEF when compared to patients not on ß-blockers. However, the effect of ß-blocker therapy on LVEF was not affected by ADRB1 genotype. The current study did not demonstrate an influence of patient ADRB1 genotype on longitudinal LVEF in our cohort. Despite previous literature suggesting a positive influence of ß-blocker use on cardiac function in DMD patients and of an ADRB1 genotypic difference in responsiveness to ß-blocker use, we did not observe this in our cohort. Interestingly, our cohort did not demonstrate a positive influence of ß-blocker use on LVEF measures.

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.

Ex Ante Economic Evaluation of Arg389 Genetically Targeted Treatment with Bucindolol versus Empirical Treatment with Carvedilol in NYHA III/IV Heart Failure

OBJECTIVE

The Beta-Blocker Evaluation Survival Trial showed no survival benefit for bucindolol in New York Heart Association (NYHA) class III/IV heart failure (HF) with reduced ejection fraction, but subanalyses suggested survival benefits for non-Black subjects and Arg389 homozygotes. We conducted an ex ante economic evaluation of Arg389 targeted treatment with bucindolol versus carvidolol, complementing a previous ex ante economic evaluation of bucindolol preceded by genetic testing for the Arg389 polymorphism, in which genetic testing prevailed economically over no testing.

METHODS

A decision tree analysis with an 18-month time horizon was performed to estimate the cost effectiveness/cost utility of trajectories of 100%, 50%, and 0% of patients genetically tested for Arg389 and comparing bucindolol with empirical carvedilol treatment as per prior BEST subanalyses. Incremental cost-effectiveness/cost-utility ratios (ICERs/ICURs) were estimated.

RESULTS

Race-based analyses for non-White subjects at 100% testing showed a loss of (0.04) life-years and (0.03) quality-adjusted life-years (QALYs) at an incremental cost of $2185, yielding a negative ICER of ($54,625)/life-year and ICUR of ($72,833)/QALY lost; at 50%, the analyses showed a loss of (0.27) life-years and (0.16) QALYs at an incremental cost of $1843, yielding a negative ICER of ($6826)/life-year and ICUR of ($11,519)/QALY lost; at 0%, the analyses showed a loss of (0.33) life-years and (0.30) QALYs at an incremental cost of $1459, yielding a negative ICER of ($4421)/life-year and ICUR of ($4863)/QALY lost. Arg389 homozygote analyses at 100% testing showed incremental gains of 0.02 life-years and 0.02 QALYs at an incremental cost of $378, yielding an ICER of 18,900/life-year and ICUR of $18,900/QALY gained; at 50%, the analyses showed a loss of (0.24) life-years and (0.09) QALYs at an incremental cost of $1039, yielding a negative ICER of ($4329)/life-year and ICUR of ($9336)/QALY lost; at 0%, the analyses showed a loss of (0.33) life-years and (0.30) QALYs at an incremental cost of $1459, yielding a negative ICER of ($4421)/life-year and ICUR of ($4863)/QALY lost.

CONCLUSION

This independent ex ante economic evaluation suggests that genetically targeted treatment with bucindolol is unlikely to yield clinicoeconomic benefits over empirical treatment with carvedilol in NYHA III/IV HF.

Clinical value of detecting autoantibodies against β1-, β2,- and α1-adrenergic receptors in carvedilol treatment of patients with heart failure

Objective

To determine the possible association of anti-β₁-adrenergic receptors (anti-β₁-AR), anti-β₂-AR and anti-α₁-AR with carvedilol treatment in patients with heart failure (HF).

Methods

A total of 267 HF patients were prospectively enrolled. Blood samples were measured by an enzyme-linked immunosorbent assay. All of the patients received carvedilol for their HF. Each patient was followed up for six months and their cardiac function was measured.

Results

The final analysis encompassed 137 patients comprising 65 patients with three autoantibodies (positive group) and 72 patients without all three autoantibodies but with one or two autoantibodies (negative group). The frequency and geometric mean titer of anti-β₁-AR, anti-β₂-AR, and anti-α₁-AR were significantly lower in the group without all three autoantibodies after six months of carvedilol treatment (all P < 0.01; from 100% to 57%, 50%, and 49%, respectively; and from 1: 118, 1: 138, and 1: 130 to 1: 72, 1: 61, and 1: 67, respectively). Furthermore, 28 patients in the positive group demonstrated complete ablation of autoantibodies. In addition, left ventricular remodelling and function was significantly improved by the use of carvedilol combined with the standard treatment regime for six months in the positive group (P < 0.01) when compared to the negative group (P < 0.05).

Conclusions

Carvedilol treatment significantly decreases frequency and geometric mean titer in patients with all three autoantibodies, even up to complete ablation, and significantly improved cardiac function and remodelling. The effect of carvedilol is probably correlated to the presence of all three autoantibodies.

Literature data based systems pharmacology uncovers the essence of "body fire" in traditional Chinese medicine: A case by Huang-Lian-Jie-Du-Tang

ETHNOPHARMACOLOGY RELEVANCE

Like other concepts in traditional Chinese medical theory, "body fire", a concept that has already been well-known and widely used in describing the symptoms and the treatment of corresponding diseases, is, however, still under suspicions in the western medicine due to its vague essence and symptoms. Presently, Huang-Lian-Jie-Du-Tang (HLJDT), a typical popular TCM formula in cleansing the "body fire", is studied as a probe by a systems pharmacology method we produced, with purpose to explore the mechanisms of the potion, as well as to interpret the essence of "body fire" disease.

METHODS

The systematic process includes a pharmacokinetics prescreening, pharmacodynamics targets and pathways identification, and candidate-target-pathway network construction.

RESULTS

Through this method, 145 chemicals and 91 proteins are identified as active ingredients and "body fire"-related targets. And we find that the mechanism of HLJDT prescription for cleansing "body fire" lies in three, i.e., anti-OS/NS, anti-inflammation and anti-infection function modules, which are mainly executed through four, i.e., PI3K-AKT, MAPK, VEGF as well as Calcium signaling pathways.

CONCLUSIONS

Accordingly, the essence of "body fire" is a gradual process which is an integration of OS/NS, inflammation and infection. This work, we hope, may not only offer a systemic methodology for exploring and elucidating TCM concepts from a multi-scale perspective, but also provide an efficient way for herbal drug discovery.

Adrenergic Polymorphisms and Survival in African Americans With Heart Failure: Results From A-HeFT

BACKGROUND

Polymorphisms in adrenergic signaling affect the molecular function of adrenergic receptors and related proteins. The β1 adrenergic receptor (ADRB1) Arg389Gly, G-protein receptor kinase type 5 (GRK5) Gln41Leu, G-protein β-3 subunit (GNB3) 825 C/T, and α2c deletion affect adrenergic tone, impact heart failure outcomes and differ in prevalence by ethnicity. Their combined effect within black cohorts remains unknown.

METHODS AND RESULTS

We analyzed subjects from the African American Heart Failure Trial (A-HeFT) by assessing event-free survival, quality of life, and gene coinheritance. Significant coinheritance effects on survival included GRK5 Leu41 among subjects co-inheriting GNB3 825 C alleles (n = 166, 90.4% vs 69.0%, P < 0.001). By contrast, the impact of ADRB1 Arg389Arg genotype was magnified among subjects with GNB3 825 TT genotype (n = 181, 66.3% vs 85.7%, P = .002). The lack of the α2c deletion (ie, insertion) led to a greater impact of the ARG389Arg genotype (n = 289, 76.4% vs 86.1%, P = .007).

CONCLUSIONS

Polymorphisms in adrenergic signaling affects outcomes in black subjects with heart failure. Coinheritance patterns in genetic variation may help determine heart failure survival.

Beta 1, Beta 2 and Beta 3 Adrenergic Receptor Gene Polymorphisms in a Southeastern European Population

Genetic polymorphisms in β₁-, β₂- and β₃-adrenergic receptors (β-ARs) have been associated with chronic non-communicable disorders, such as cardiovascular diseases, asthma, chronic obstructive pulmonary disease (COPD) and obesity, as well as β-agonists and antagonists response and toxicity. The purpose of this study was to determine the frequency distribution of ADRB1 genetic variants Ser49Gly and Arg389Gly, ADRB2 variants Gly16Arg and Gln27Glu, ADRB3 variant Trp64Arg in a Southeastern European Caucasian (SEC) population sample and to establish a comparison with existing data from other human populations. A sample of 431 men and 590 women volunteered to participate in this genotyping analysis after anonymization and de-identification. Real Time PCR (Melting Curve Analysis) followed DNA extraction from buccal swabs and statistical analysis of the results was performed. The allele frequencies in the SEC population were Ser49 (90.3%), Arg389 (69.49%), Gly16 (61.61%), Gln27 (65.72%), and Trp64 (94.52%), while a Hardy-Weinberg Equilibrium (HWE) was detected in the population studied. Comparisons for the Ser49Gly, Gln27Glu, and Trp64Arg allele distributions demonstrated significant differences between SEC and the European group. European subgroups comparisons showed that allele distributions were similar for four of the five SNPs between SEC and Southwestern European Caucasians (SWC), while they were quite distinct from the Northwestern European Caucasians (NWC). These data underline the importance of interethnic variability of β-ARs genetic polymorphisms.

Hypertension genomics and cardiovascular prevention

Hypertension continues to be a major risk factor for global mortality, and recent genome-wide association studies (GWAS) have expanded in size, leading to the identification of further genetic loci influencing blood pressure. In light of the new knowledge from the largest cardiovascular GWAS to date, we review the potential impact of genomics on discovering potential drug targets, risk stratification with genetic risk scores, drug selection with pharmacogenetics, and exploring insights provided by gene-environment interactions.

Pharmacogenetics in Cardiovascular Medicine

Considerable interindividual variability in response to cardiovascular pharmacotherapy exists with drug responses varying from being efficacious to inadequate to induce severe adverse events. Fueled by advancements and multidisciplinary collaboration across disciplines such as genetics, bioinformatics, and basic research, the vision of personalized medicine, rather than a one-size-fits-all approach, may be within reach. Pharmacogenetics offers the potential to optimize the benefit-risk profile of drugs by tailoring diagnostic and treatment strategies according to the individual patient. To date, a multitude of studies has tried to delineate the effects of gene-drug interactions for drugs commonly used to treat cardiovascular-related disease. The focus of this review is on how genetic variability may modify drug responsiveness and patient outcomes following therapy with commonly used cardiovascular drugs including clopidogrel, warfarin, statins, and β-blockers. Also included are examples of how genetic studies can be used to guide drug discovery and examples of how genetic information may be deployed in clinical decision making.

The impact of dual bronchodilation on cardiovascular serious adverse events and mortality in COPD: a quantitative synthesis

Objective

Long-acting β₂-agonists (LABAs) and long-acting muscarinic antagonists (LAMAs) are burdened by the potential risk of inducing cardiovascular serious adverse events (SAEs) in COPD patients. Since the risk of combining a LABA with a LAMA could be greater, we have carried out a quantitative synthesis to investigate the cardiovascular safety profile of LABA/LAMA fixed-dose combinations (FDCs).

Methods

A pair-wise and network meta-analysis was performed by using the data of the repository database ClinicalTrials.gov concerning the impact of approved LABA/LAMA FDCs versus monocomponents and/or placebo on cardiovascular SAEs in COPD.

Results

Overall, LABA/LAMA FDCs did not significantly (P>0.05) modulate the risk of cardiovascular SAEs versus monocomponents. However, the network meta-analysis indicated that aclidinium/formoterol 400/12 µg and tiotropium/olodaterol 5/5 µg were the safest FDCs, followed by umeclidinium/vilanterol 62.5/25 µg which was as safe as placebo, whereas glycopyrronium/formoterol 14.9/9.6, glycopyrronium/indacaterol 15.6/27.5 µg, and glycopyrronium/indacaterol 50/110 µg were the least safe FDCs. No impact on mortality was detected for each specific FDC.

Conclusion

This meta-analysis indicates that LABA/LAMA FDC therapy is characterized by an excellent cardiovascular safety profile in COPD patients. However, the findings of this quantitative synthesis have been obtained from populations that participated in randomized clinical trials, and were devoid of major cardiovascular diseases. Thus, post-marketing surveillance and observational studies may help to better define the real impact of specific FDCs with regard to the cardiovascular risk.

Genetics of systolic and diastolic heart failure

Heart failure accounts for a significant portion of heart diseases. Molecular mechanisms gradually emerge that participate in pathways leading to left ventricular dysfunction in common systolic heart failure (SHF) and diastolic heart failure (DHF). A human genome-wide association study (GWAS) identified two markers for SHF and no GWAS on DHF has been documented. However, genetic analyses in rat models of SHF and DHF have begun to unravel the genetic components known as quantitative trait loci (QTLs) initiating systolic and diastolic function. A QTL for systolic function was detected and the gene responsible for it is identified to be that encoding the soluble epoxide hydrolase. Diastolic function is determined by multiple QTLs and the Ccl2/monocyte chemotactic protein gene is the strongest candidate. An amelioration on diastolic dysfunction is merely transient from changing such a single QTL accompanied by a blood pressure reduction. A long-term protection can be achieved only via combining alleles of several QTLs. Thus, distinct genes in synergy are involved in physiological mechanisms durably ameliorating or reversing diastolic dysfunction. These data lay the foundation for identifying causal genes responsible for individual diastolic function QTLs and the essential combination of them to attain a permanent protection against diastolic dysfunction, and consequently will facilitate the elucidation of pathophysiological mechanisms underlying hypertensive diastolic dysfunction. Novel pathways triggering systolic and diastolic dysfunction have emerged that will likely provide new diagnostic tools, innovative therapeutic targets and strategies in reducing, curing and even reversing SHF and DHF.

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.

3D structure prediction of human β1-adrenergic receptor via threading-based homology modeling for implications in structure-based drug designing

Dilated cardiomyopathy is a disease of left ventricular dysfunction accompanied by impairment of the β₁-adrenergic receptor (β₁-AR) signal cascade. The disturbed β₁-AR function may be based on an elevated sympathetic tone observed in patients with heart failure. Prolonged adrenergic stimulation may induce metabolic and electrophysiological disturbances in the myocardium, resulting in tachyarrhythmia that leads to the development of heart failure in human and sudden death. Hence, β₁-AR is considered as a promising drug target but attempts to develop effective and specific drug against this tempting pharmaceutical target is slowed down due to the lack of 3D structure of Homo sapiens β₁-AR (hsβADR1). This study encompasses elucidation of 3D structural and physicochemical properties of hsβADR1 via threading-based homology modeling. Furthermore, the docking performance of several docking programs including Surflex-Dock, FRED, and GOLD were validated by re-docking and cross-docking experiments. GOLD and Surflex-Dock performed best in re-docking and cross docking experiments, respectively. Consequently, Surflex-Dock was used to predict the binding modes of four hsβADR1 agonists. This study provides clear understanding of hsβADR1 structure and its binding mechanism, thus help in providing the remedial solutions of cardiovascular, effective treatment of asthma and other diseases caused by malfunctioning of the target protein.

Polymorphic variants of adrenoceptors: pharmacology, physiology, and role in disease

The human genome encodes nine different adrenoceptor genes. These are grouped into three families, namely, the α1-, α2-, and β-adrenoceptors, with three family members each. Adrenoceptors are expressed by most cell types of the human body and are primary targets of the catecholamines epinephrine and norepinephrine that are released from the sympathetic nervous system during its activation. Upon catecholamine binding, adrenoceptors change conformation, couple to and activate G proteins, and thereby initiate various intracellular signaling cascades. As the primary receivers and transducers of sympathetic activation, adrenoceptors have a central role in human physiology and disease and are important targets for widely used drugs. All nine adrenoceptor subtypes display substantial genetic variation, both in their coding sequence as well as in adjacent regions. Despite the fact that some of the adrenoceptor variants range among the most frequently studied genetic variants assessed in pharmacogenetics to date, their functional relevance remains ill defined in many cases. A substantial fraction of the associations reported from early candidate gene approaches have not subsequently been confirmed in different cohorts or in genome-wide association studies, which have increasingly been conducted in recent years. This review aims to provide a comprehensive overview of all adrenoceptor variants that have reproducibly been detected in the larger genome sequencing efforts. We evaluate these variants with respect to the modulation of receptor function and expression and discuss their role in physiology and disease.

GNAS gene variants affect β-blocker-related survival after coronary artery bypass grafting

BACKGROUND

Cardiac overexpression of the β-adrenoreceptor (βAR)-coupled stimulatory G-protein subunit Gαs enhances inotropic responses to adrenergic stimulation and improves survival in mice under βAR blockade. The authors recently identified three common haplotypes in the GNAS gene encoding Gαs, with the greatest Gαs protein expression and signal transduction in haplotype *3 carriers and less in haplotype *2 and *1 carriers. The authors tested the hypothesis that these GNAS variants result in altered mortality in patients after coronary artery bypass graft surgery, particularly in those receiving βAR blockade.

METHODS

This prospective analysis included 1,627 European ancestry patients undergoing primary coronary artery bypass graft surgery. Patients were genotyped for two GNAS haplotype tagging single-nucleotide polymorphisms defining three major haplotypes. Up to 5-yr all-cause mortality was estimated using a Cox proportional hazard model; hazard ratios and 95% CIs were calculated while adjusting for demographics, clinical covariates, and the new EuroSCORE II.

RESULTS

Univariate analysis revealed haplotype-dependent 5-yr mortality rates (*1/*1: 18.9%, *2/*1: 13.7%, *2/*2: 9.3%, *3/*1: 10.6%, *3/*2: 9.1%, and *3/*3: 9.6%; P = 0.0006). After adjustment for other predictors of death, homozygote haplotype *1 carriers showed a doubled risk for death (hazard ratio, 2.2; 95% CI, 1.2 to 3.8; P = 0.006). Considering only patients receiving βAR blockers (n = 1,267), the adjusted risk of death even tripled (hazard ratio, 3.0; 95% CI, 1.5 to 6.1; P = 0.002).

CONCLUSIONS

GNAS haplotypes independently associate with an increased risk of death after primary coronary artery bypass graft surgery. These results are most pronounced in patients receiving βAR blockers, strengthening the rationale for personalized treatment, to decrease medication side effects and improve outcomes.

Biomarkers for the development of new medications for cocaine dependence

There has been significant progress in personalized drug development. In large part, this has taken place in the oncology field and been due to the ability of researchers/clinicians to discover and develop novel drug development tools (DDTs), such as biomarkers. In cancer treatment research, biomarkers have permitted a more accurate pathophysiological characterization of an individual patient, and have enabled practitioners to target mechanistically the right drug, to the right patient, at the right time. Similar to cancer, patients with substance use disorders (SUDs) present clinically with heterogeneous symptomatology and respond variably to therapeutic interventions. If comparable biomarkers could be identified and developed for SUDs, significant diagnostic and therapeutic advances could be made. In this review, we highlight current opportunities and difficulties pertaining to the identification and development of biomarkers for SUDs. We focus on cocaine dependence as an example. Putative diagnostic, pharmacodynamic (PD), and predictive biomarkers for cocaine dependence are discussed across a range of methodological approaches. A possible cocaine-dependent clinical outcome assessment (COA)--another type of defined DDT--is also discussed. At present, biomarkers for cocaine dependence are in their infancy. Much additional research will be needed to identify, validate, and qualify these putative tools prior to their potential use for medications development and/or application to clinical practice. However, with a large unmet medical need and an estimated market size of several hundred million dollars per year, if developed, biomarkers for cocaine dependence will hold tremendous value to both industry and public health.

Applied pharmacogenomics in cardiovascular medicine

Interindividual heterogeneity in drug response is a central feature of all drug therapies. Studies in individual patients, families, and populations over the past several decades have identified variants in genes encoding drug elimination or drug target pathways that in some cases contribute substantially to variable efficacy and toxicity. Important associations of pharmacogenomics in cardiovascular medicine include clopidogrel and risk for in-stent thrombosis, steady-state warfarin dose, myotoxicity with simvastatin, and certain drug-induced arrhythmias. This review describes methods used to accumulate and validate these findings and points to approaches--now being put in place at some centers--to implementing them in clinical care.

Expanding role of pharmacogenomics in the management of cardiovascular disorders

Cardiovascular disease is a leading cause of death worldwide. Many pharmacologic therapies are available that aim to reduce the risk of cardiovascular disease but there is significant inter-individual variation in drug response, including both efficacy and toxicity. Pharmacogenetics aims to personalize medication choice and dosage to ensure that maximum clinical benefit is achieved whilst side effects are minimized. Over the past decade, our knowledge of pharmacogenetics in cardiovascular therapies has increased significantly. The anticoagulant warfarin represents the most advanced application of pharmacogenetics in cardiovascular medicine. Prospective randomized clinical trials are currently underway utilizing dosing algorithms that incorporate genetic polymorphisms in cytochrome P450 (CYP)2C9 and vitamin k epoxide reductase (VKORC1) to determine warfarin dosages. Polymorphisms in CYP2C9 and VKORC1 account for approximately 40 % of the variance in warfarin dose. There is currently significant controversy with regards to pharmacogenetic testing in anti-platelet therapy. Inhibition of platelet aggregation by aspirin in vitro has been associated with polymorphisms in the cyclo-oxygenase (COX)-1 gene. However, COX-1 polymorphisms did not affect clinical outcomes in patients prescribed aspirin therapy. Similarly, CYP2C19 polymorphisms have been associated with clopidogrel resistance in vitro, and have shown an association with stent thrombosis, but not with other cardiovascular outcomes in a consistent manner. Response to statins has been associated with polymorphisms in the cholesterol ester transfer protein (CETP), apolipoprotein E (APOE), 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, calmin (CLMN) and apolipoprotein-CI (APOC1) genes. Although these genes contribute to the variation in lipid levels during statin therapy, their effects on cardiovascular outcomes requires further investigation. Polymorphisms in the solute carrier organic anion transporter 1B1 (SLCO1B1) gene is associated with increased statin exposure and simvastatin-induced myopathy. Angiotensin-converting enzyme (ACE) inhibitors and β-adrenoceptor antagonists (β-blockers) are medications that are important in the management of hypertension and heart failure. Insertion and deletion polymorphisms in the ACE gene are associated with elevated and reduced serum levels of ACE, respectively. No significant association was reported between the polymorphism and blood pressure reduction in patients treated with perindopril. However, a pharmacogenetic score incorporating single nucleotide polymorphisms (SNPs) in the bradykinin type 1 receptor gene and angiotensin-II type I receptor gene predicted those most likely to benefit and suffer harm from perindopril therapy. Pharmacogenetic studies into β-blocker therapy have focused on variations in the β1-adrenoceptor gene and CYP2D6, but results have been inconsistent. Pharmacogenetic testing for ACE inhibitor and β-blocker therapy is not currently used in clinical practice. Despite extensive research, no pharmacogenetic tests are currently in clinical practice for cardiovascular medicines. Much of the research remains in the discovery phase, with researchers struggling to demonstrate clinical utility and validity. This is a problem seen in many areas of therapeutics and is because of many factors, including poor study design, inadequate sample sizes, lack of replication, and heterogeneity amongst patient populations and phenotypes. In order to progress pharmacogenetics in cardiovascular therapies, researchers need to utilize next-generation sequencing technologies, develop clear phenotype definitions and engage in multi-center collaborations, not only to obtain larger sample sizes but to replicate associations and confirm results across different ethnic groups.

Genetic determinants of response to cardiovascular drugs

PURPOSE OF REVIEW

To survey genetic variation contributing to variable responsiveness and toxicity to important cardiovascular drugs and highlight recent developments in the field of cardiovascular pharmacogenomics and personalized medicine.

RECENT FINDINGS

Previously recognized pharmacogenomic associations with drug efficacy have been further validated (e.g. with clopidogrel and warfarin) and shown to influence clinically important outcomes. The clinical significance of variants modulating toxicity (e.g. SLCO1B1 with simvastatin) has also been confirmed. The genetic contribution to variable efficacy and toxicity of other important classes of cardiovascular drugs, such as beta-blockers, is becoming increasingly recognized. Prospective trials testing whether the use of genomic information improves clinical care are underway. Guidance based on the most well-established pharmacogenomic findings has appeared in prescribing labeling and is in the early stages of being implemented into routine clinical care.

SUMMARY

Clinically validated gene variants that modulate responsiveness to cardiovascular drugs continue to be discovered and validated. Early steps are underway to translate these discoveries into clinical care.

β1 adrenergic receptor polymorphisms and heart failure: a meta-analysis on susceptibility, response to β-blocker therapy and prognosis

Aims

The risk stratification of patients for heart failure (HF) remains a challenge, as well as the anticipation of the response to β-blocker therapy. Since the pivotal role of β1 adrenergic receptor (β1-AR) in HF, many publications have studied the associations between the β1-AR polymorphisms (Ser49Gly and Arg389Gly) and HF, with inconsistent results. Thus, we performed a meta-analysis of studies to evaluate the impact of β1-AR polymorphisms on susceptibility to HF, the response to β-blocker therapy and the prognosis of HF.

Methods and Results

Electronic databases were systematically searched before August 2011. We extracted data sets and performed meta-analysis with standardized methods. A total of 27 studies met our inclusion criteria. It was found that in East Asians, the Gly389 allele and Gly389 homozygotes significantly increased the HF risk, while the Gly389 allele and Gly389 homozygotes trended to decrease the risk of HF in whites. With the similar reduction of heart rate, overall, the Arg389 homozygotes showed a better response to β-blocker therapy. Furthermore, the Arg389 homozygotes were significantly associated with better LVEF improvement in East Asians and a mixed population. And in white people, the Arg389 homozygotes made a greater LVESd/v improvement and trended to be associated with better LVEDd/v improvement. However, the prognosis of Arg389 homozygotes HF patients was similar to those with Gly389 carriers. The Ser49Gly polymorphism did not impact the risk or prognosis of HF.

Conclusion

Based on our meta-analysis, the Gly389 allele and Gly389 homozygotes were risk factors in East Asians while trending to protect whites against HF. Furthermore, Arg389 homozygote is significantly associated with a favorable response to β-blocker treatment in HF patients. However, neither of the two polymorphisms is an independent predictor of the prognosis of HF.

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.

Heart rate achieved or beta-blocker dose in patients with chronic heart failure: which is the better target?

AIMS

To investigate whether the mortality of patients with chronic heart failure (CHF) due to left ventricular systolic dysfunction (LVSD) is more strongly related to beta-blocker dose or to heart rate. It is known that beta-blockers reduce mortality in patients with CHF and LVSD, but the primary mechanism of action is uncertain.

METHODS AND RESULTS

Patients with an ejection fraction ≤40%, who were in sinus rhythm both at an initial (visit 1) and at a 4-month clinic review (visit 2), were followed for a maximum of 36 months. The relationships between heart rate, beta-blocker dose, and survival in a multivariable model were examined. Of 654 eligible patients, 381 (58%) were started on beta-blockers prior to the initial visit, increasing to 537 (82%) by visit 2. During follow-up, 142 (22%) patients died. Neither resting heart rate nor beta-blocker dose at visit 1 predicted mortality (P = 0.09 and P = 0.99), but resting heart rate at visit 2 did (P = 0.02). Beta-blocker use at visit 2 was associated with better outcome (P = 0.03) but with little variation in outcome according to dose. Patients with a heart rate of 58-64 b.p.m. at visit 2 had the best prognosis.

CONCLUSIONS

The use of beta-blockers and resting heart rate at visit 2 both independently indicated prognosis, but beta-blocker dose did not. Beta-blockers may reduce mortality by several mechanisms; one that may be specific to blockade of adrenergic receptors and another related to heart rate reduction. Achieving a target heart rate range may be an appropriate therapeutic goal for patients with CHF.

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.

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.

A highly versatile microscope imaging technology platform for the multiplex real-time detection of biomolecules and autoimmune antibodies

The analysis of different biomolecules is of prime importance for life science research and medical diagnostics. Due to the discovery of new molecules and new emerging bioanalytical problems, there is an ongoing demand for a technology platform that provides a broad range of assays with a user-friendly flexibility and rapid adaptability to new applications. Here we describe a highly versatile microscopy platform, VideoScan, for the rapid and simultaneous analysis of various assay formats based on fluorescence microscopic detection. The technological design is equally suitable for assays in solution, microbead-based assays and cell pattern recognition. The multiplex real-time capability for tracking of changes under dynamic heating conditions makes it a useful tool for PCR applications and nucleic acid hybridization, enabling kinetic data acquisition impossible to obtain by other technologies using endpoint detection. The paper discusses the technological principle of the platform regarding data acquisition and processing. Microbead-based and solution applications for the detection of diverse biomolecules, including antigens, antibodies, peptides, oligonucleotides and amplicons in small reaction volumes, are presented together with a high-content detection of autoimmune antibodies using a HEp-2 cell assay. Its adaptiveness and versatility gives VideoScan a competitive edge over other bioanalytical technologies.

A systematic review on pharmacogenetics in cardiovascular disease: is it ready for clinical application?

Pharmacogenetics is the search for heritable genetic polymorphisms that influence responses to drug therapy. The most important application of pharmacogenetics is to guide choosing agents with the greatest potential of efficacy and smallest risk of adverse drug reactions. Many studies focusing on drug-gene interactions have been published in recent years, some of which led to adaptation of FDA recommendations, indicating that we are on the verge of the clinical application of genetic information in drug therapy. This systematic review provides a comprehensive overview of the current knowledge on pharmacogenetics of all major drug classes currently used in the treatment of cardiovascular diseases.

Genome-wide significance and replication of the chromosome 12p11.22 locus near the PTHLH gene for peripartum cardiomyopathy

BACKGROUND

Peripartum (PP) cardiomyopathy (CM) is a rare condition of unknown etiology that occurs in late pregnancy or early postpartum. Initial evidence suggests that genetic factors may influence PPCM. This study evaluated and replicated genome-wide association of single nucleotide polymorphisms with PPCM.

METHODS AND RESULTS

Genome-wide single nucleotide polymorphisms in women with verified PPCM diagnosis (n=41) were compared separately with local control subjects (n=49 postmenopausal age-discordant women with parity ≥1 and no heart failure) and iControls (n=654 women ages 30 to 84 years with unknown phenotypes). A replication study of independent population samples used new cases (PPCM2, n=30) compared with new age-discordant control subjects (local2, n=124) and with younger control subjects (n=89) and obstetric control subjects (n=90). A third case set of pregnancy-associated CM cases not meeting strict PPCM definitions (n=29) was also studied. In the genome-wide association study, 1 single nucleotide polymorphism (rs258415) met genome-wide significance for PPCM versus local control subjects (P=2.06×10(-8); odds ratio [OR], 5.96). This was verified versus iControls (P=7.92×10(-19); OR, 8.52). In the replication study for PPCM2 cases, rs258415 (ORs are per C allele) replicated at P=0.009 versus local2 control subjects (OR, 2.26). This replication was verified for PPCM2 versus younger control subjects (P=0.029; OR, 2.15) and versus obstetric control subjects (P=0.013; OR, 2.44). In pregnancy-associated cardiomyopathy cases, rs258415 had a similar effect versus local2 control subjects (P=0.06; OR, 1.79), younger control subjects (P=0.14; OR, 1.65), and obstetric control subjects (P=0.038; OR, 1.99).

CONCLUSIONS

Genome-wide association with PPCM was discovered and replicated for rs258415 at chromosome 12p11.22 near PTHLH. This study indicates a role of genetic factors in PPCM and provides a new locus for further pathophysiological and clinical investigation.

Systems biology and heart failure: concepts, methods, and potential research applications

Dramatic advances in molecular biology dominated twentieth century biomedical science and delineated the function of individual genes and molecules in exquisite detail. However, biological processes cannot be fully understood based on the properties of individual genes and molecules alone, since these elements act in concert to enable the specific functions that make for living cells and organisms. The discipline of systems biology provides a novel conceptual framework for understanding biological phenomenon. Systems biology synthesizes information concerning the interactions of genes and molecules and allows characterization of the supramolecular networks and functional modules that represent the most essential aspects of cell organization and physiology.

Contribution of genetic factors to the pathogenesis of dilated cardiomyopathy: the cause of dilated cardiomyopathy: genetic or acquired? (genetic-side)

Dilated cardiomyopathy (DCM) is characterized by dilated ventricles and systolic dysfunction. Its etiology is not fully unraveled, but both extrinsic and intrinsic factors are considered to be involved. The intrinsic factors include genetic variations in the genes (ie, disease-causing mutations and disease-associated polymorphisms), which play key roles in controlling the susceptibility to the disease by affecting the performance, regulation, and/or maintenance of cardiac function. DCM can be classified into 2 types: hereditary and non-hereditary. The genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM can be found in various genes, especially those for sarcolemma elements, contractile elements, Z-disc elements, sarcoplasmic elements, and nuclear lamina elements of cardiomyocytes. On the other hand, disease-associated polymorphisms, which control the susceptibility to non-hereditary DCM, may be found in genes expressing not only in cardiomyocytes but also other non-cardiac cells involved in the immune system. Because functional alterations caused by these genetic variations can be classified into several categories, it is necessary to understand the pathogenesis and hence to develop diagnostic and therapeutic strategies for both hereditary and non-hereditary DCM from the viewpoint of genetic factors.

A meta-analysis of β1-adrenergic receptor gene polymorphisms in idiopathic dilated cardiomyopathy

Published data on the association between β1-adrenergic receptor gene polymorphisms and idiopathic dilated cardiomyopathy (IDCM) risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 12 case-control studies including 2642 cases and 3136 controls provided data on the association between β1-adrenergic receptor gene polymorphisms and susceptibility to IDCM. Overall, no significantly elevated risk was associated with Arg389Gly polymorphisms for all genetic models. In the subgroup analysis by ethnicity, no statistically increased risk was found for Gly389Gly versus Arg389Arg (OR 0.73; 95% CI 0.54-0.99; Ph=0.35) and Gly389Gly versus Arg389Arg+Arg389Gly (OR 0.75; 95% CI 0.55-1.01; Ph=0.52) among Europeans. Meanwhile, significantly increased risk was found among Asians based on the relatively small sample size. Further, significantly elevated IDCM risk was associated with Ser49Gly polymorphisms for all genetic models. When stratified by ethnicity, statistical association was found among Asians for Gly49Gly versus Ser49Ser (OR 4.56; 95% CI 1.36-15.23; Ph=0.10) and Gly49Gly versus Ser49Ser+Ser49Gly (OR 4.49; 95% CI 1.33-15.15; Ph=0.12), but not among Europeans. In summary, this meta-analysis suggests that no statistically increased risk was found between β1-adrenergic receptor gene polymorphisms and susceptibility to IDCM among Europeans.

Differential regulation of two palmitoylation sites in the cytoplasmic tail of the beta1-adrenergic receptor

S-Palmitoylation of G protein-coupled receptors (GPCRs) is a prevalent modification, contributing to the regulation of receptor function. Despite its importance, the palmitoylation status of the β(1)-adrenergic receptor, a GPCR critical for heart function, has never been determined. We report here that the β(1)-adrenergic receptor is palmitoylated on three cysteine residues at two sites in the C-terminal tail. One site (proximal) is adjacent to the seventh transmembrane domain and is a consensus site for GPCRs, and the other (distal) is downstream. These sites are modified in different cellular compartments, and the distal palmitoylation site contributes to efficient internalization of the receptor following agonist stimulation. Using a bioorthogonal palmitate reporter to quantify palmitoylation accurately, we found that the rates of palmitate turnover at each site are dramatically different. Although palmitoylation at the proximal site is remarkably stable, palmitoylation at the distal site is rapidly turned over. This is the first report documenting differential dynamics of palmitoylation sites in a GPCR. Our results have important implications for function and regulation of the clinically important β(1)-adrenergic receptor.

Age-related up-regulation of beta3-adrenergic receptor in heart-failure rats

Stimulation of beta1- and beta2-adrenergic receptors (ARs) in the heart results in positive inotropy. In contrast, it has been reported that the beta3-AR is also expressed in the heart and that its stimulation leads to negative inotropic effects. The aim of this study was to investigate the expression of beta3-AR in age-related heart-failure rats and its relevance to left ventricular dysfunction. Aging male Wistar rats were divided into young and aging groups according to age, and each group included sham-operation and heart-failure subgroups. Left ventricular end-diastolic pressure (LVEDP) and the ratio of left ventricular weight to body weight (LV/BW) were significantly higher for the aging heart-failure versus young heart-failure and the heart-failure versus sham-operation groups (P < 0.01, respectively). However, the left ventricular end-systolic pressure (LVESP) and the maximal rate of rise or fall of left ventricular pressure were all significantly lower for the aging heart-failure versus young heart-failure and the heart-failure versus sham-operation groups (P < 0.01, respectively). beta3-AR protein levels increased significantly when heart failure worsened in aging rats. These results suggest that beta3-AR expression in age-related heart-failure rats and left ventricular function were highly correlated.

Role of beta-adrenergic receptor gene polymorphisms in the long-term effects of beta-blockade with carvedilol in patients with chronic heart failure

BACKGROUND

Beta-blockers are mainstay of current treatment of heart failure (HF). Beta-adrenergic receptors (AR) single nucleotide gene polymorphisms (SNPs) may influence the sensitivity and density of beta-AR. We assessed the relation between three common beta-AR SNPs and the response to carvedilol administration.

METHODS AND RESULTS

We studied 183 consecutive patients with chronic HF due to ischemic or nonischemic cardiomyopathy, a LV ejection fraction (LVEF) < or = 0.35, not previously treated with beta-blockers. Each patient underwent gated-SPECT radionuclide ventriculography, cardiopulmonary exercise testing and invasive hemodynamic monitoring at baseline and after 12 months of carvedilol administration at maintenance dosages. The beta1-AR gene Arg389Gly and the beta2-AR gene Arg16Gly SNPs were not related to the response to carvedilol administration. Homozygotes for the Glu27Glu allele showed a greater increase in the LVEF, compared to the other patients (+13.0 +/- 12.2% versus +7.1 +/- 8.1% in the Gln27Gln homozygotes, and 8.3 +/- 11.4% units in the Gln27Glu heterozygotes; p = 0.022 by ANOVA). Glu27Glu homozygotes also showed a greater decline in the pulmonary wedge pressure both at rest and at peak exercise. Gln27Glu SNP was selected amongst the determinants of the LVEF response to carvedilol at multivariable analysis, in addition to the cause of cardiomyopathy, baseline systolic blood pressure and the dose of carvedilol administered.

CONCLUSION

Beta1-AR Arg389Gly and beta2-AR Arg16Gly SNPs are not related to the response to carvedilol therapy. In contrast, the Gln27Glu SNP is a determinant of the LVEF response to this agent in patients with chronic HF.

The Arg16Gly-β(2)-adrenoceptor single nucleotide polymorphism: exercise capacity and survival in patients with end-stage heart failure

Heart failure (HF) is characterized by impaired myocardial β-adrenergic signal transduction. Single nucleotide polymorphisms (SNPs) within the β(1)- (Ser49Gly, Arg389Gly) and β(2)-adrenoceptor (Arg16Gly, Gln27Glu, Thr164Ile) have been associated with alterations in adrenoceptor (AR) function sensitivity in vitro and in vivo and possibly contribute to HF progression. The present study evaluated the relation of those SNPs to morbidity and mortality in patients with end-stage HF. A total of 226 patients with end-stage HF (ejection fraction ≤35%) were genotyped for the two β(1)AR SNPs and the three β(2)AR SNPs. Outcome (death, heart transplantation (HTX)) was determined from May 2003 to June 2004. Heart rate, systolic and diastolic blood pressure, and peak oxygen uptake were measured during graded treadmill exercise. Left ventricular end-diastolic and end-systolic diameters, ejection fraction, and fractional shortening at rest were measured using two-dimensional echocardiography. Minor allele frequencies were 0.12 for Gly49 and 0.27 for Gly389 (β(1)AR) and 0.37 for Arg16, 0.43 for Glu27 and 0.01 for Ile164 (β(2)AR). During follow-up, 45 patients died (20%), and 27 patients underwent HTX (12%). No significant differences in the incidence or in the time-to-endpoint of death and HTX between genotypes of the different SNPs within the β(1)- and β(2)AR were detected. However, patients carrying the Arg16-β(2)AR tended to have lower exercise capacity and a higher probability for death/HTX within 45 months (survival proportion 46%) than patients carrying the Gly16Gly-β(2)AR (survival proportion 64%). In conclusion, the Arg16Gly-β(2)AR might impact on exercise capacity and outcome in end-stage heart failure.