The functional significance of genetic variation within the beta-adrenoceptor

Combining genetic proxies of drug targets and time-to-event analyses from longitudinal observational data to identify target patient populations

BACKGROUND

Human genetics is an important tool for identifying genes as potential drug targets, and the extensive genetic study of cardiovascular disease provides an opportunity to leverage genetics to match specific patient populations to specific drug targets to improve prioritization of patient selection for clinical studies.

METHODS

We selected well described genetic variants in the region of PCSK9 (rs11591147 and rs562556), ADRB1 (rs7076938), ACE (rs4968782 and rs4363), GLP1R (rs10305492) and ABCC8 (rs757110) for use as proxies for the effects of drugs. Time-to-event analyses were utilized to evaluate their effects on atrial fibrillation (AF) and heart failure (HF) death and/or re-hospitalization using real-world longitudinal dataset. To mitigate the effect of confounding factors for cardiovascular (CV) outcomes, we employed propensity score matching.

RESULTS

After matching, a genetic proxy for PCSK9 inhibition (rs11591147) improved survival from CV death/heart transplant in individuals following a diagnosis of ischemic heart disease (Hazard Ratio (HR) 0.78, P = 0.03). A genetic proxy for beta-blockade (rs7076938) improved freedom from rehospitalization or death in individuals with AF (HR 0.92, P = 0.001), and a genetic proxy of ACE inhibition (rs7076938) improved freedom from rehospitalization for HF or death (HR 0.8, P = 0.017) and AF (HR 0.85, P = 0.0014). A protective variant in GLP1R (rs10305492) showed decreased risk of developing HF or CV death after diagnosis of ischemic heart disease (HR = 0.82, P = 0.031) and a protective variant in ABCC8 (rs757110) showed decreased risk of CV mortality since ischemic disease diagnosis (HR = 0.88, P = 0.04) and decreased risk of AF in diabetic patients with ischemic heart disease (HR = 0.68, P = 0.001). Notably, despite smaller cohort sizes after matching, we often observed numerically smaller HRs and reduced P, indicating more pronounced effects and increased statistical association. However, not all genetic proxies replicated known treatment effects.

CONCLUSIONS

Genetic proxies for well-known drugs corroborate findings from clinical trials in cardiovascular disease. Our results demonstrate a useful analytical approach that leverages genetic evidence from a large cohort with longitudinal outcomes data to effectively select patient populations where specific drug targets may be most effective.

Clinical Pharmacogenetics Implementation Consortium Guideline (CPIC) for CYP2D6, ADRB1, ADRB2, ADRA2C, GRK4, and GRK5 Genotypes and Beta-Blocker Therapy

Beta-blockers are widely used medications for a variety of indications, including heart failure, myocardial infarction, cardiac arrhythmias, and hypertension. Genetic variability in pharmacokinetic (e.g., CYP2D6) and pharmacodynamic (e.g., ADRB1, ADRB2, ADRA2C, GRK4, GRK5) genes have been studied in relation to beta-blocker exposure and response. We searched and summarized the strength of the evidence linking beta-blocker exposure and response with the six genes listed above. The level of evidence was high for associations between CYP2D6 genetic variation and both metoprolol exposure and heart rate response. Evidence indicates that CYP2D6 poor metabolizers experience clinically significant greater exposure and lower heart rate in response to metoprolol compared with those who are not poor metabolizers. Therefore, we provide therapeutic recommendations regarding genetically predicted CYP2D6 metabolizer status and metoprolol therapy. However, there was insufficient evidence to make therapeutic recommendations for CYP2D6 and other beta-blockers or for any beta-blocker and the other five genes evaluated (updates at www.cpicpgx.org).

Binding kinetics drive G protein subtype selectivity at the β1-adrenergic receptor

G protein-coupled receptors (GPCRs) bind to different G protein α-subtypes with varying degrees of selectivity. The mechanism by which GPCRs achieve this selectivity is still unclear. Using 13C methyl methionine and 19F NMR, we investigate the agonist-bound active state of β1AR and its ternary complexes with different G proteins in solution. We find the receptor in the ternary complexes adopts very similar conformations. In contrast, the full agonist-bound receptor active state assumes a conformation differing from previously characterised activation intermediates or from β1AR in ternary complexes. Assessing the kinetics of binding for the agonist-bound receptor with different G proteins, we find the increased affinity of β1AR for Gs results from its much faster association with the receptor. Consequently, we suggest a kinetic-driven selectivity gate between canonical and secondary coupling which arises from differential favourability of G protein binding to the agonist-bound receptor active state.

Polymorphisms in common antihypertensive targets: Pharmacogenomic implications for the treatment of cardiovascular disease

The idea of personalized medicine came to fruition with sequencing the human genome; however, aside from a few cases, the genetic revolution has yet to materialize. Cardiovascular diseases are the leading cause of death globally, and hypertension is a common prelude to nearly all cardiovascular diseases. Thus, hypertension is an ideal candidate disease to apply tenants of personalized medicine to lessen cardiovascular disease. Herein is a survey that visually depicts the polymorphisms in the top eight antihypertensive targets. Although there are numerous genome-wide association studies regarding cardiovascular disease, few studies look at the effects of receptor polymorphisms on drug treatment. With 17,000+ polymorphisms in the combined target proteins examined, it is expected that some of the clinical variability in the treatment of hypertension is due to polymorphisms in the drug targets. Recent advances in techniques and technology, such as high throughput examination of single mutations, structure prediction, computational power for modeling, and CRISPR models of point mutations, allow for a relatively rapid and comprehensive examination of the effects of known and future polymorphisms on drug affinity and effects. As hypertension is easy to measure and has a plethora of clinically viable ligands, hypertension makes an excellent disease to study pharmacogenomics in the lab and the clinic. If the promises of personalized medicine are to materialize, a concerted effort to examine the effects polymorphisms have on drugs is required. A clinician with the knowledge of a patient's genotype can then prescribe drugs that are optimal for treating that specific patient.

Genetic Polymorphisms, Mediterranean Diet and Microbiota-Associated Urolithin Metabotypes can Predict Obesity in Childhood-Adolescence

Environmental and genetic factors are associated with pandemic obesity since childhood. However, the association of overweight-obesity with these factors, acting as a consortium, has been scarcely studied in children. We aimed here to assess the probabilities of being overweighed-obese in a randomly recruited cohort of Spanish children and adolescents (n = 415, 5−17 years-old) by estimating the odds ratios for different predictor variables, and their relative importance in the prediction. The predictor variables were ethnicity, age, sex, adherence to the Mediterranean diet (KIDMED), physical activity, urolithin metabotypes (UM-A, UM-B and UM-0) as biomarkers of the gut microbiota, and 53 single-nucleotide polymorphisms (SNPs) from 43 genes mainly related to obesity and cardiometabolic diseases. A proportional-odds logistic ordinal regression, validated through bootstrap, was used to model the data. While every variable was not independently associated with overweight-obesity, however, the ordinal logistic model revealed that overweight-obesity prevalence was related to being a young boy with either UM-B or UM-0, low KIDMED score and high contribution of a consortium of 24 SNPs, being rs1801253-ADRB1, rs4343-ACE, rs8061518-FTO, rs1130864-CRP, rs659366-UCP2, rs6131-SELP, rs12535708-LEP, rs1501299-ADIPOQ, rs708272-CETP and rs2241766-ADIPOQ the top-ten contributing SNPs. Additional research should confirm and complete this model by including dietary interventions and the individuals’ gut microbiota composition.

Effects of β-Adrenoceptor and Catechol-O-Methyl-Transferase (COMT) Polymorphism on Postoperative Outcome in Cardiac Surgery Patients

BACKGROUND There is a long-standing debate about the role of beta-adrenoceptor polymorphisms in the cardiovascular system. We wanted to elucidate whether β1-adrenoceptor-polymorphisms affects the postoperative catecholamine consumption and the length of intermediate care unit stay in patients undergoing cardiac surgery, and whether this might be enhanced or attenuated by catechol-O-methyl-transferase (COMT) polymorphism. MATERIAL AND METHODS We included 116 patients (63±1.2 years; 34% females; 81±1 kg) undergoing cardiac surgery. We assessed Arg389Gly and Ser49Gly-β1-adrenoceptor (B1AR) polymorphism together with Val158Met-COMT polymorphism by real-time PCR using fluorescence resonance energy transfer (PCR-FRET). The preoperative risk was assessed by EuroSCORE. In addition, we measured the endogenous preoperative epinephrine and norepinephrine plasma concentrations using an electrochemical HPLC method. RESULTS 84.6% were homozygous for Ser49Ser, 52.1% homozygous for Arg389Arg B1AR, and 32.5% for Val158Val-COMT, while 15.4% showed Ser49Gly B1AR, 38.5% Arg389Gly-B1AR, and 35.6% Val158Met-COMT. We found that the Gly49-variant, the Gly389-variant, and the Val158-COMT-variant were associated with higher postoperative norepinephrine consumption. All patients carrying the Val158-COMT allele exhibited higher preoperative norepinephrine concentrations. Moreover, we found that both β1-adrenoceptor polymorphisms were associated with a longer stay in hospital, which was modulated by the COMT polymorphism. CONCLUSIONS These data show that the β1-adrenoceptor polymorphisms, together with the COMT polymorphism, affect norepinephrine consumption and stay in hospital in a situation of enhanced cardiovascular stress, reflected here by the postoperative period after cardiac surgery. Moreover, we conclude that patients with the Val158-COMT genotype exhibit higher endogenous resting plasma norepinephrine levels.

The Polymorphisms of Ser49Gly and Gly389Arg in Beta-1-Adrenergic Receptor Gene in Major Depression

INTRODUCTION

It was reported that the genetic susceptibility of major depressive disorder (MDD) is related with genetic polymorphisms. The aim of this study was to investigate the possible association of the genotype and allele frequencies of Ser49Gly and Arg389Gly polymorphisms in MDD by comparing them with healthy subjects.

METHODS

A total of 144 patients with MDD diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria and 105 healthy controls were included in the study. Polymerase chain reaction (PCR) with restriction fragment length polymorphism (RFLP) was used for genotyping.

RESULTS

Of the 144 participants in the MDD group, 77 (53.5%) had homozygous wild type (AA), 57 (39.6%) had heterozygous type (AG), and 10 (6.9%) had mutant (GG) genotype for Ser49Gly, whereas 75 (52.1%) had homozygous wild type (GG), 59 (41.0%) had heterozygous (GC) type, and 10 (6.9%) had mutant homozygous (CC) genotype for Gly386Arg. There were no significant difference in the allele and genotype frequencies of the beta-1-adrenergic receptor (ADRB1) gene for Ser49Gly and Arg389Gly polymorphisms after comparing with healthy controls (p=0.626; p=0.863 and p=0.625; p=0.914).

CONCLUSION

The results of our study did not reveal a major effect of the polymorphism of Ser49Gly and Gly389Arg in the ADRB1 gene in MDD. Further studies with larger sample size are required to elucidate the role of other beta-1 adrenergic gene polymorphisms in MDD.

Relevance of G-quadruplex structures to pharmacogenetics

G-quadruplexes are non-canonical secondary structures formed within nucleic acids that are involved in modulating cellular processes such as replication, gene regulation, recombination and epigenetics. Within genes, there is mounting evidence of G-quadruplex involvement in transcriptional and post transcriptional regulation. We report the presence of potential G-quadruplex motifs within relevant sites of some important pharmacogenes and discuss the possible implications of this on the function and expression of these genes. Appreciating the location and potential functions of these motifs may be of value when considering the impacts of some pharmacogenetic variants. G-quadruplexes are also the focus of drug development efforts in oncology and we highlight the broader pharmacological implications of treatment strategies that may target G-quadruplexes.

Identification of DNA variants in the canine beta-1 adrenergic receptor gene

Beta-adrenergic receptor antagonists are utilized for the management of several cardiac diseases in the dog. In humans the beneficial effects of beta-adrenergic receptor antagonists are variable and are associated with a genetic variability in the beta one adrenergic receptor gene (ADRB1). To determine if DNA variants were present in the canine ADRB1 gene, DNA from five breeds of dogs was evaluated. Two deletions were identified within the region of the gene that encodes the cytoplasmic tail of ADRB1. The functions of this region are not well understood although it is important in differentiating subtypes of adrenergic receptors and may be associated with control of receptor downregulation. The functional consequences of these identified variants deserve further study.

Methylenetetrahydrofolate reductase (MTHFR) polymorphism A1298C (Glu429Ala) predicts decline in renal function over time in the African-American Study of Kidney Disease and Hypertension (AASK) Trial and Veterans Affairs Hypertension Cohort (VAHC)

BACKGROUND

Hyperhomocysteinemia is associated with increased venous thrombosis and cardiovascular disease (CVD). Mutations in the human methylenetetrahydrofolate reductase (MTHFR) gene have been associated with increased homocysteine levels and risks of CVD in various populations including those with kidney disease. Here, we evaluated the influence of MTHFR variants on progressive loss of kidney function.

METHODS

We analyzed 821 subjects with hypertensive nephrosclerosis from the longitudinal National Institute of Diabetes and Digestive and Kidney Diseases African-American Study of Kidney Disease and Hypertension (AASK) Trial to determine whether decline in glomerular filtration rate (GFR) over ∼4.2 years was predicted by common genetic variation within MTHFR at non-synonymous positions C677T (Ala222Val) and A1298C (Glu429Ala) or by MTHFR haplotypes. The effect on GFR decline was then supported by a study of 1333 subjects from the San Diego Veterans Affairs Hypertension Cohort (VAHC), followed over ∼4.5 years. Linear effect models were utilized to determine both genotype [single-nucleotide polymorphism (SNP)] and genotype (SNP)-by-time interactions.

RESULTS

In AASK, the polymorphism at A1298C predicted the rate of GFR decline: A1298/A1298 major allele homozygosity resulted in a less pronounced decline of GFR, with a significant SNP-by-time interaction. An independent follow-up study in the San Diego VAHC subjects supports that A1298/A1298 homozygotes have the greatest estimated GFR throughout the study. Haplotype analysis with C677T yielded concurring results.

CONCLUSION

We conclude that the MTHFR-coding polymorphism at A1298C is associated with renal decline in African-Americans with hypertensive nephrosclerosis and is supported by a veteran cohort with a primary care diagnosis of hypertension. Further investigation is needed to confirm such findings and to determine what molecular mechanism may contribute to this association.

Synopsis and data synthesis of genetic association studies in hypertension for the adrenergic receptor family genes: the CUMAGAS-HYPERT database

BACKGROUND

The adrenergic receptor (adrenoceptor) family genes have been extensively studied as candidate genes in hypertension but the results of individual genetic association studies (GAS) are controversial and inconclusive. To clarify these data, a systematic assessment of GAS for adrenoceptor family genes in hypertension was conducted.

METHODS

Data from 163 GAS involving 7 genes and 37 distinct genetic variants were analyzed and cataloged in CUMAGAS-HYPERT (Cumulative Meta-analysis of Genetic Association Studies-HYPERTension; a web-based information system, which allows the retrieval and synthesis of data from GAS in hypertension, available at http://biomath.med.uth.gr). Data from genome-wide association studies involving the adrenoceptor family genes were also systematically searched.

RESULTS

Individual GAS reported inconsistent associations and had limited power to detect modest genetic effects, with only 1.2% having power >80%. Thirteen variants were investigated by three or more studies and their results were subject to meta-analysis. In the main meta-analyses, significant results were shown for five variants (ADRB1 p.Arg389Gly, ADRB1 p.Ser49Gly, ADRB2 g.9368308A>G, ADRB3 p.Trp64Arg, and ADRA1A p.Cys347Arg) under the allelic contrast and/or the dominant model. Subgroup analyses by ethnicity and gender detected significant associations for three variants (ADRB1 p.Arg389Gly in east Asians, ADRB2 p.Gln27Glu in whites, and ADRB3 p.Trp64Arg in whites and in males). Heterogeneity ranged from none to high. No significant associations were recorded from genome-wide studies.

CONCLUSIONS

There is evidence to implicate adrenoceptor genes in hypertension, although future studies designed to investigate epistatic and gene-environment interactions would allow more solid conclusions to be drawn about the role of these genes in hypertension.

A pilot study of the pharmacodynamic impact of SSRI drug selection and beta-1 receptor genotype (ADRB1) on cardiac vital signs in depressed patients: a novel pharmacogenetic approach

OBJECTIVE

The adrenergic beta-1 receptor gene (ADRB1) Ser49Gly and Arg389Gly variants differentially affect blood pressure response to beta-blocker therapy. Binding site prediction results for fluoxetine and paroxetine in a bioinformatics model estimated that each of these particular selective serotonin reuptake inhibitors (SSRIs) have high receptor affinity as an "Adrenergic (beta) Blocker," which was confirmed in vitro. This pilot study was conducted to understand the relationship between these "beta-blocking" SSRIs (fluoxetine and paroxetine) and cardiac vital signs (systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR)), when subjects are stratified by ADRB1 genotype. Previously ascertained DNA and clinical data was examined from 122 subjects recruited for a cross-sectional study of health and well being during SSRI pharmacotherapy. A multivariate linear regression analysis was used to determine which variables affected cardiac vital signs. There was a significant interaction between Arg389Gly variant status and "beta-blocking" SSRIs [p = 0.0353] in relation to SBP. Specifically in homozygous Arg389 subjects, those receiving "beta-blocking" SSRIs had significantly lower SBP (mean 104 mmHg) compared to the group taking other SSRIs (mean 122 mmHg) [p = 0.0437]. In these same homozygous Arg389 subjects, those receiving "beta-blocking" SSRIs also had lower HR (mean 60 bpm) compared to the other SSRIs (mean 79 bpm) [p = 0.00877]. Future prospective studies of this phenomenon are necessary to identify all genetic markers that can predict SSRI-associated cardiovascular effects that may be related to the SSRI discontinuation syndrome and potentially influence pharmacotherapy decisions.

Adrenergic beta-1 receptor genetic variation predicts longitudinal rate of GFR decline in hypertensive nephrosclerosis

BACKGROUND

End-stage renal disease (ESRD) due to hypertension is common and displays familial aggregation in African Americans, suggesting genetic risk factors, including adrenergic activity alterations which are noted in both hypertension and ESRD.

METHODS

We analysed 554 hypertensive nephrosclerosis participants (without clinically significant proteinuria) from the longitudinal National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) African American Study of Kidney Disease and Hypertension (AASK) cohort to determine whether decline in glomerular filtration rate (GFR) over approximately 3.8 years was predicted by common genetic variation within the adrenergic beta-1 (ADRB1) receptor at non-synonymous positions Ser49Gly and Arg389Gly.

RESULTS

The polymorphism at Ser49Gly (though not Arg389Gly, in only partial linkage disequilibrium at r(2) = 0.18) predicted the chronic rate of GFR decline, with minimal decline in Gly(49)/Gly(49) (minor allele) homozygotes compared to Ser(49) carriers; concordant results were observed for haplotypes and diploid haplotype pairs at the locus. An independent replication study in 1244 subjects from the San Diego Veterans Affairs Hypertension Cohort confirmed that Gly(49)/Gly(49) homozygotes displayed the least rapid decline of eGFR over approximately 3.6 years.

CONCLUSION

We conclude that GFR decline rate in hypertensive renal disease is controlled in part by genetic variation within the adrenergic pathway, particularly at ADRB1. The results suggest novel strategies to approach the role of the adrenergic system in the risk and treatment of progressive renal disease.

Diverse evolutionary histories for beta-adrenoreceptor genes in humans

In humans, three genes--ADRB1, ADRB2 and ADRB3--encode beta-adrenoreceptors (ADRB); these molecules mediate the action of catecholamines in multiple tissues and play pivotal roles in cardiovascular, respiratory, metabolic, and immunological functions. Genetic variants in ADRB genes have been associated with widespread diseases and conditions, but inconsistent results have often been obtained. Here, we addressed the recent evolutionary history of ADRB genes in human populations. Although ADRB1 is neutrally evolving, most tests rejected neutral evolution for ADRB2 in European, African, and Asian population samples. Analysis of inferred haplotypes for ADRB2 revealed three major clades with a coalescence time of 1-1.5 million years, suggesting that the gene is either subjected to balancing selection or undergoing a selective sweep. Haplotype analysis also revealed ethnicity-specific differences. Additionally, we observed significant deviations from Hardy-Weinberg equilibrium (HWE) for ADRB2 genotypes in distinct European cohorts; HWE deviation depends on sex (only females are in disequilibrium), and genotypes displaying maximum and minimum relative fitness differ across population samples, suggesting a complex situation possibly involving epistasis or maternal selection. Overall, our data indicate that future association studies involving ADRB2 will benefit from taking into account ethnicity-specific haplotype distributions and sex-based effects. With respect to ADRB3, our data indicate that the gene has been subjected to a selective sweep in African populations, the Trp64 variant possibly representing the selection target. Given the previous association of the ancestral ADRB3 Arg64 allele with obesity and type 2 diabetes, dietary adaptations might represent the underlying selective force.

Effects of Polymorphism of the β1 Adrenoreceptor and CYP2D6 on the Therapeutic Effects of Metoprolol

Metoprolol is a lipophilic β1 selective adrenergic receptor antagonist used in antihypertensive therapy. It is metabolized by the protein product of the cytochrome P450 2D6 ( CYP2D6) gene. Few studies have been performed on the association between the β1 adrenoreceptor, CYP2D6 polymorphism and blood pressure. The one reported here is a prospective, observational, clinical study in Chinese Han hypertensive patients on the combined influences of CYP2D6 and β1 adrenoreceptor polymorphisms on the therapeutic effects of metoprolol in 300 out-patients with essential hypertension. The same dose of metoprolol achieved different therapeutic effects in patients with different CYP2D6 and β1 adrenoreceptor polymorphisms. Additionally, different doses of metoprolol could achieve the same therapeutic effects in patients with different CYP2D6 and β1 adrenoreceptor polymorphisms. Knowledge of the combination of CYP2D6 and β1 adrenoreceptor polymorphisms may be used to guide antihypertensive therapy using β1 adrenoreceptor antagonists.

Variation in the genes encoding vesicular monoamine transporter 2 and beta-1 adrenergic receptor and antidepressant treatment outcome

The identification of genetic variants regulating antidepressant response would allow for more individualized, rational, and successful drug treatments. We previously identified a region of mouse chromosome 19 that strongly influences citalopram response in an antidepressant model, the tail suspension test. By virtue of their location in this loci, expression in brain, and involvement in monoamine neurotransmission, we nominated SLC18A2 (encoding vesicular monoamine transporter 2, a.k.a. VMAT2) and ADRB1 (encoding beta-1 adrenergic receptor) as candidate genes for a human pharmacogenetic study. This study tested for an association between SLC18A2 and ADRB1 and treatment outcome in 873 major depressive disorder patients treated with the antidepressant citalopram in the Sequenced Treatment Alternatives to Relieve Depression study. Haplotype-tagging single nucleotide polymorphisms (four in SLC18A2 and two in ADRB1) were chosen to detect the common genetic variation. We failed to detect any significant association between treatment outcome and genotypes or allele frequencies at any of the markers studied. We did, however, detect ethnic differences in the allele frequencies of five out of six markers. These data do not rule out the possible involvement of SLC18A2 or ADRB1 in antidepressant treatment response as these genes may contribute a small effect size or interact epistatically with other genes.

Beta-1 and beta-2 adrenoceptor polymorphisms: functional importance, impact on cardiovascular diseases and drug responses

Beta-1 and beta-2 adrenoceptors (AR) play a pivotal role in regulation of the activity of the sympathetic nervous system and agonists and antagonists at both beta AR subtypes are frequently used in treatment of cardiovascular diseases. Both beta-1 and beta-2 AR genes have several polymorphisms that encode different amino acids. This review summarizes new insights into the functional importance of these polymorphisms, as well as their relationship to cardiovascular diseases and their impact on responses to adrenergic drug treatment. At present, it seems that, for cardiovascular diseases, beta-1 and beta-2 AR polymorphisms do not play a role as disease-causing genes; they might, however, be associated with disease-related phenotypes. In addition they could influence adrenergic drug responses. Thus, the Arg389Gly beta-1 AR polymorphism might predict responsiveness to beta-1 AR agonist and blocker treatment: patients homozygous for the Arg389 beta-1 AR polymorphism should be good responders, while patients homozygous for the Gly389 beta-1 AR polymorphism should be poor or nonresponders. Furthermore, the Arg16Gln27 beta-2 AR seems to have strong impact on long-term agonist-induced beta-2 AR desensitization. Thus, patients carrying this haplotype appear to suffer from rapid loss of therapeutic efficacy of chronic agonist treatment, as has been demonstrated in asthma patients. Moreover, the Arg16Gln27 beta-2 AR haplotype might have some predictive value for poor outcome of heart failure. Future large prospective studies have to replicate these findings in order to reach the final goal of pharmacogenomic research: to optimize and individualize drug therapy based on the patient's genetic determinants of drug efficacy.

In patients chronically treated with metoprolol, the demand of inotropic catecholamine support after coronary artery bypass grafting is determined by the Arg389Gly-β1-adrenoceptor polymorphism

In vitro, the Arg389Gly-beta(1)-adrenoceptor (AR) polymorphism exhibits decreased receptor signaling. In vivo, dobutamine infusion evoked smaller heart rate and/or contractility increases in subjects carrying Gly389Gly-beta(1)AR vs subjects carrying Arg389Arg-beta(1)AR. The aim of this study was to find out whether the Arg389Gly-beta(1)AR polymorphism might also determine demand of catecholamine-induced inotropic support in patients with low cardiac index (CI) after coronary artery bypass grafting (CABG) surgery with cardiopulmonary bypass (CPB). For this purpose, we assessed in 82 patients, who were preoperatively chronically treated with metoprolol, after CABG surgery with CPB, the dose and duration of adrenaline-induced inotropic support in relation to the Arg389Gly-beta(1)AR genotype. Patients homozygous for the Arg389-beta(1)AR variant (n = 45) required, in comparison to patients homozygous for the Gly389-beta(1)AR variant (n = 9), lower adrenaline doses (53 +/- 24 vs 164 +/- 39 ng/kg body weight/min, p < 0.05) to reach a stable and comparable hemodynamic status and a CI >or= 3.0 l/min/m(2). Moreover, the time necessary for inotropic support tended to be shorter in patients homozygous for the Arg389-beta(1)AR than in patients homozygous for the Gly389-beta(1)AR (10.5 +/- 6 vs 20.5 +/- 12 h). Values for patients heterozygous for the Arg389Gly-beta(1)AR (n = 28) were in between. We conclude that the Arg389Gly-beta(1)AR polymorphism appears to be a determinant of cardiac responses to catecholamine stimulation. Thus, by assessment of the Arg389Gly-beta(1)AR polymorphism, it might be possible to predict demand of and therapeutic responses to beta AR agonist treatment.