Effects of beta1-adrenoceptor genetic polymorphisms on resting hemodynamics in patients undergoing diagnostic testing for ischemia

The Effect of Genetically Guided Mathematical Prediction and the Blood Pressure Response to Pharmacotherapy in Hypertension Patients

Purpose:

The purpose of this study was to determine the effectiveness of a simple algorithm to mathematically predict a patients’ response to blood pressure (BP) therapy using functional genes in the 3 major organ systems involved in hypertension.

Methods:

Eighty-six patients with controlled hypertension completed 1 study visit consisting of a buccal swab collection, measurement of office BP, and a medical chart review for BP history. Genes in the analysis included 14 functional alleles in 11 genes. These genotypes were mathematically summed per organ system to determine whether a patient would likely respond to target therapy.

Results:

Patients recommended to and taking a diuretic had significantly higher rates of control (<120/<80) than patients recommended but not taking this drug class (0.2 ± 0.1 and 0.03 ± 0.03, respectively). Furthermore, there was a difference between patients genetically recommended and taking an angiotensin receptor blocker (ARB) vs patients recommended but not taking an ARB for the lowest diastolic blood pressure (DBP) and mean arterial pressure (MAP) recorded in the past 2 years (DBP = 66.2 ± 2.9 and 75.3 ± 1.7, MAP = 82.3 ± 2.8 and 89.3 ± 1.5, respectively). In addition, there was a nonsignificant trend for greater reductions in ΔSBP, ΔDBP, and ΔMAP in patients on recommended drug class for beta-blockers, diuretics, and angiotensin II receptor blockers vs patients not on these classes.

Conclusion:

The present study suggests that simple mathematical weighting of functional genotypes known to control BP may be ineffective in predicting control. This study demonstrates the need for a more complex, weighted, multigene algorithm to more accurately predict BP therapy response.

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.

Relationship between a Weighted Multi-Gene Algorithm and Blood Pressure Control in Hypertension

Hypertension (HTN) is a complex disease with interactions among multiple organ systems, including the heart, vasculature, and kidney with a strong heritable component. Despite the multifactorial nature of HTN, no clinical guidelines utilize a multi-gene approach to guide blood pressure (BP) therapy. Non-smokers with a family history of HTN were included in the analysis (n = 384; age = 61.0 ± 0.9, 11% non-white). A total of 17 functional genotypes were weighted according to the previous effect size in the literature and entered into an algorithm. Pharmacotherapy was ranked from 1–4 as most to least likely to respond based on the algorithmic assessment of individual patient’s genotypes. Three-years of data were assessed at six-month intervals for BP and medication history. There was no difference in BP at diagnosis between groups matching the top drug recommendation using the multi-gene weighted algorithm (n = 92) vs. those who did not match (n = 292). However, from diagnosis to nadir, patients who matched the primary recommendation had a significantly greater drop in BP when compared to patients who did not. Further, the difference between diagnosis to current 1-year average BP was lower in the group that matched the top recommendation. These data suggest an association between a weighted multi-gene algorithm on the BP response to pharmacotherapy.

Genetics of cardiovascular disease: Importance of sex and ethnicity

Sex differences in incidence and prevalence of and morbidity and mortality from cardiovascular disease are well documented. However, many studies examining the genetic basis for cardiovascular disease fail to consider sex as a variable in the study design, in part, because there is an inherent difficulty in studying the contribution of the sex chromosomes in women due to X chromosome inactivation. This paper will provide general background on the X and Y chromosomes (including gene content, the pseudoautosomal regions, and X chromosome inactivation), discuss how sex chromosomes have been ignored in Genome-wide Association Studies (GWAS) of cardiovascular diseases, and discuss genetics influencing development of cardiovascular risk factors and atherosclerosis with particular attention to carotid intima-medial thickness, and coronary arterial calcification based on sex-specific studies. In addition, a brief discussion of how ethnicity and hormonal status act as confounding variables in sex-based analysis will be considered along with methods for statistical analysis to account for sex in cardiovascular disease.

Floppy mitral valve/mitral valve prolapse syndrome: Beta-adrenergic receptor polymorphism may contribute to the pathogenesis of symptoms

BACKGROUND

Certain patients with floppy mitral valve (FMV)/mitral valve prolapse (MVP) may have symptoms that cannot be explained on the severity of mitral valvular regurgitation (MVR) alone; hypersensitivity to adrenergic stimulation has been suggested in this group defined as the FMV/MVP syndrome.

METHODS

Ninety-eight patients (75 men, 23 women) with mitral valve surgery for FMV/MVP were studied. Of those 41 (42%) had symptoms consistent with FMV/MVP syndrome [29 men (39%), 12 women (52%)]; median age of symptom onset was 30 years (range 10-63 years) and median duration of symptoms prior to valve surgery was 16 years (range 3-50 years). Ninety-nine individuals (70 men, 29 women) without clinical evidence of any disease were used as controls. Genotyping of β1 and β2 adrenergic receptors was performed.

RESULTS

β-Adrenergic receptor genotypes (β1 and β2) were similar between control and overall FMV/MVP patients. Subgroup analysis of patients, however, demonstrated that the genotype C/C at position 1165 resulting in 389 Arg/Arg of the β1 receptor was more frequent in women compared to those without FMV/MVP syndrome and to normal control women (p<0.025). This polymorphism may be related to hypersensitivity to adrenergic stimulation as reported previously in these patients.

CONCLUSION

This study shows a large proportion of patients with FMV/MVP, predominantly women, had symptoms consistent with the FMV/MVP syndrome for many years prior to the development of significant MVR, and thus symptoms cannot be attributed to the severity of MVR alone. Further, women with FMV/MVP syndrome, symptoms at least partially may be related to β1-adrenergic receptor polymorphism, which has been shown previously to be associated with a hyperresponse to adrenergic stimulation.

G protein-coupled receptor kinase 5 gene polymorphisms are associated with postoperative atrial fibrillation after coronary artery bypass grafting in patients receiving β-blockers

BACKGROUND

We hypothesized that genetic variations in the adrenergic signaling pathway and cytochrome P450 2D6 enzyme are associated with new-onset atrial fibrillation (AF) in patients who underwent coronary artery bypass grafting and were treated with perioperative β-blockers (BBs).

METHODS AND RESULTS

Two cohorts of patients who underwent coronary artery bypass grafting and received perioperative BBs at Duke University Medical Center were studied. In a discovery cohort of 563 individuals from the Perioperative Genetics and Safety Outcomes Study (PEGASUS), using a covariate-adjusted logistic regression analysis, we tested 492 single-nucleotide polymorphisms (SNPs) in 10 candidate genes of the adrenergic signaling pathway and cytochrome P450 2D6 for association with postoperative AF despite perioperative BB therapy. SNPs meeting a false discovery rate ≤0.20 (P<0.002) were then tested in the replication cohort of 245 individuals from the Catheterization Genetics biorepository. Of the 492 SNPs examined, 4 intronic SNPs of the G protein-coupled kinase 5 (GRK5) gene were significantly associated with postoperative AF despite perioperative BB therapy in the discovery cohort with additive odds ratios between 1.72 and 2.75 (P=4.78×10(-5) to 0.0015). Three of these SNPs met nominal significance levels in the replication cohort with odds ratios between 2.07 and 2.60 (P=0.007 to 0.016). However, meta-analysis of the 2 data sets cohorts suggested strong association with postoperative AF despite perioperative BB therapy in all 4 SNPs (meta-P values from 1.66×10(-6) to 3.39×10(-5)).

CONCLUSIONS

In patients undergoing coronary artery bypass grafting, genetic variation in GRK5 is associated with postoperative AF despite perioperative BB therapy.

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.

Clustering heart rate dynamics is associated with β-adrenergic receptor polymorphisms: analysis by information-based similarity index

Background

Genetic polymorphisms in the gene encoding the β-adrenergic receptors (β-AR) have a pivotal role in the functions of the autonomic nervous system. Using heart rate variability (HRV) as an indicator of autonomic function, we present a bottom-up genotype–phenotype analysis to investigate the association between β-AR gene polymorphisms and heart rate dynamics.

Methods

A total of 221 healthy Han Chinese adults (59 males and 162 females, aged 33.6±10.8 years, range 19 to 63 years) were recruited and genotyped for three common β-AR polymorphisms: β₁-AR Ser49Gly, β₂-AR Arg16Gly and β₂-AR Gln27Glu. Each subject underwent two hours of electrocardiogram monitoring at rest. We applied an information-based similarity (IBS) index to measure the pairwise dissimilarity of heart rate dynamics among study subjects.

Results

With the aid of agglomerative hierarchical cluster analysis, we categorized subjects into major clusters, which were found to have significantly different distributions of β₂-AR Arg16Gly genotype. Furthermore, the non-randomness index, a nonlinear HRV measure derived from the IBS method, was significantly lower in Arg16 homozygotes than in Gly16 carriers. The non-randomness index was negatively correlated with parasympathetic-related HRV variables and positively correlated with those HRV indices reflecting a sympathovagal shift toward sympathetic activity.

Conclusions

We demonstrate a bottom-up categorization approach combining the IBS method and hierarchical cluster analysis to detect subgroups of subjects with HRV phenotypes associated with β-AR polymorphisms. Our results provide evidence that β₂-AR polymorphisms are significantly associated with the acceleration/deceleration pattern of heart rate oscillation, reflecting the underlying mode of autonomic nervous system control.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Relationships of adrenoceptor polymorphisms with obesity

Obesity, hypertension, and type 2 diabetes are rapidly growing public health problems. Heightened sympathetic nerve activity is a well-established observation in obesity, hypertension, and type 2 diabetes. Human obesity, hypertension, and diabetes have strong genetic as well as environmental determinants. Reduced energy expenditure and resting metabolic rate are predictive of weight gain, and the sympathetic nervous system participates in regulating energy balance through thermogenesis. The thermogenic effects of catecholamines in obesity are mainly mediated via the β2, and β3-adrenergic receptors in humans. Further, β2-adrenoceptors importantly influence vascular reactivity and may regulate blood pressure. β-adrenoceptor polymorphisms have also been associated with adrenoceptor desensitization, increased adiposity, insulin resistance, and enhanced sympathetic nervous activity. Many epidemiological studies have shown strong relationships between adrenoceptor polymorphisms and obesity, but the observations have been discordant. This paper will discuss the current topics involving the influence of the sympathetic nervous system and β2- and β3-adrenoceptor polymorphisms in obesity.

Adrenergic signaling polymorphisms and their impact on cardiovascular disease

This review examines the impact of recent discoveries defining personal genetics of adrenergic signaling polymorphisms on scientific discovery and medical practice related to cardiovascular diseases. The adrenergic system is the major regulator of minute-by-minute cardiovascular function. Inhibition of adrenergic signaling with pharmacological beta-adrenergic receptor antagonists (beta-blockers) is first-line therapy for heart failure and hypertension. Advances in pharmacology, molecular biology, and genetics of adrenergic signaling pathways have brought us to the point where personal genetic differences in adrenergic signaling factors are being assessed as determinants of risk or progression of cardiovascular disease. For a few polymorphisms, functional data generated in cell-based systems, genetic mouse models, and pharmacological provocation of human subjects are concordant with population studies that suggest altered risk of cardiovascular disease or therapeutic response to beta-blockers. For the majority of adrenergic pathway polymorphisms however, published data conflict, and the clinical relevance of individual genotyping remains uncertain. Here, the current state of laboratory and clinical evidence that adrenergic pathway polymorphisms can affect cardiovascular pathophysiology is comprehensively reviewed and compared, with a goal of placing these data in the broad context of potential clinical applicability.

Beta1-adrenoceptor polymorphism predicts flecainide action in patients with atrial fibrillation

Background

Antiarrhythmic action of flecainide is based on sodium channel blockade. Beta₁-adrenoceptor (β₁AR) activation induces sodium channel inhibition, too. The aim of the present study was to evaluate the impact of different β₁AR genotypes on antiarrhythmic action of flecainide in patients with structural heart disease and atrial fibrillation.

Methodology/Principal Findings

In 145 subjects, 87 with atrial fibrillation, genotyping was performed to identify the individual β₁AR Arg389Gly and Ser49Gly polymorphism. Resting heart rate during atrial fibrillation and success of flecainide-induced cardioversion were correlated with β₁AR genotype. The overall cardioversion rate with flecainide was 39%. The Arg389Arg genotype was associated with the highest cardioversion rate (55.5%; OR 3.30; 95% CI; 1.34–8.13; p = 0.003) compared to patients with Arg389Gly (29.5%; OR 0.44; 95% CI; 0.18–1.06; p = 0.066) and Gly389Gly (14%; OR 0.24; 95% CI 0.03–2.07; p = 0.17) variants. The single Ser49Gly polymorphism did not influence the conversion rate. In combination, patients with Arg389Gly-Ser49Gly genotype displayed the lowest conversion rate with 20.8% (OR 0.31; 95% CI; 0.10–0.93; p = 0.03). In patients with Arg389Arg variants the heart rate during atrial fibrillation was significantly higher (110±2.7 bpm; p = 0.03 vs. other variants) compared to Arg389Gly (104.8±2.4 bpm) and Gly389Gly (96.9±5.8 bpm) carriers. The Arg389Gly-Ser49Gly genotype was more common in patients with atrial fibrillation compared to patients without atrial fibrillation (27.6% vs. 5.2%; HR 6.98; 95% CI; 1.99–24.46; p<0.001).

Conclusions

The β₁AR Arg389Arg genotype is associated with increased flecainide potency and higher heart rate during atrial fibrillation. The Arg389Gly-Ser49Gly genotype might be of predictive value for atrial fibrillation.

Association of beta-1 and beta-2 adrenergic receptor gene polymorphisms with myocardial infarction

Both beta(1)- and beta2-adrenergic receptors (beta(1)- and beta(2)-AR) have important roles in heart function mainly in response to catecholamines. Some specific polymorphisms in the beta(1)- and beta(2)-AR genes, named ADRB1 and ADRB2, respectively, have been implicated in several cardiovascular and noncardiovascular phenotypes. In this study, we aimed to investigate the possible relationship between Ser49Gly and Arg389Gly polymorphisms of the ADRB1 and Arg16Gly and Gln27Glu polymorphisms of the ADRB2 gene with ST elevation myocardial infarction (MI) in a Turkish population. One hundred patients with ST elevation MI and 100 healthy control subjects were genotyped using the PCR-RFLP method. Although the Arg389 allele of the ADRB1 gene was associated with an elevated risk of MI, the Glu27 allele of the ADRB2 gene was associated with a decreased risk of MI. Carriers of the ADRB1 Arg389 allele (heterozygotes+homozygotes) had an approximately 3.5-fold increased risk for MI than Gly389 homozygotes (OR=3.59, 95% CI=0.96-13.47, P=0.045). For the ADRB2 Gln27Glu polymorphism, subjects having one or two copies of the Glu27 allele showed a decreased risk of MI compared with Gln27 homozygote subjects (OR=0.48, 95% CI=0.24-0.94, P=0.03). Haplotype analysis of these polymorphisms showed no significant differences between groups. These results suggest that the Arg389Gly and Gln27Glu polymorphisms may be associated with an altered risk of MI in this Turkish population.

Single nucleotide polymorphisms in genes of circulatory homeostasis in surviving pediatric intensive care patients with meningococcal infection

OBJECTIVE

In the course of a meningococcal infection, invasive and severe disease occurs in a restricted number of individuals. The predominant mechanism of death in case of meningococcal septic shock is circulatory failure. Inotropic requirements between patients vary widely. We investigated whether polymorphisms in genes regulating the hemodynamic response influence the amount of inotropics required or the susceptibility to severe meningococcal disease.

DESIGN

Retrospective case control study.

SETTING

Single-center pediatric intensive care unit (PICU).

PATIENTS

Fifty-six cases (all consecutive patients admitted to the PICU between 1993 and 2001 with a proven meningococcal infection) and 136 controls. Patients were divided into two groups according to their inotropic requirements.

INTERVENTION

DNA analysis was performed to determine the polymorphisms of the beta-adrenergic receptor gene-1, beta-adrenergic receptor gene-2, alpha-adducin, angiotensin converting enzyme, and angiotensin II type-1 receptor-1 genes.

RESULTS

For the alpha-adducin gene a significant difference of the genotype distribution was found between the cases and controls. The odds ratio for admission to the PICU with meningococcal sepsis with or without meningitis, for carriers of the variant allele (Gly460Trp or Trp460Trp) was 2.1 (95% confidence interval 1.11-4.04; p < 0.02). Cases, homozygote for the wild-type allele of the beta-1 adrenergic receptor at locus 389, were more likely to have a low pediatric risk of mortality score on admission (odds ratio 3.6, 95% confidence interval 1.11-11.76). No difference was found in the distribution of the beta-adrenergic receptor gene-1, beta-adrenergic receptor gene-2, angiotensin converting enzyme, and angiotensin II type-1 receptor-1 polymorphisms between the two groups of patients or between cases and controls.

CONCLUSIONS

Among patients admitted to the PICU with a meningococcal infection, the variant allele of the alpha-adducin gene was more prevalent compared with controls. Patients with the variant allele of the beta-adrenergic receptor gene-1 at locus 389 were more likely to have a high pediatric risk of mortality score on admission. The mechanism and clinical relevance of these findings is unclear.

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

Heart Failure (HF) is a common disorder associated with substantial morbidity and mortality. beta adrenergic receptors (betaAR) are the primary pathway through which cardiac function is influenced. Chronic beta(1)AR activation is implicated in the pathogenesis of HF and betaAR blockade improves survival in left ventricular systolic dysfunction. Common functional polymorphisms in beta adrenergic receptor genes (ADRB) have been associated with HF phenotypes, and with pharmacogenetic interaction with beta adrenergic receptor blockers (beta blockers). However, these associations have not been consistently replicated. The evidence for ADRB variant involvement in pathogenesis, progression and response to beta blockers in HF is reviewed. In addition, a meta-analysis of three studies analysing the effect of ADRB1 Arg389Gly polymorphism on left ventricular remodelling with the use of beta blockers, demonstrating a 5% improvement in left ventricular ejection fraction in Arg389 homozygotes, is presented. There is now accumulating molecular evidence for a different functional response to beta blockers associated with this polymorphism. In the future, confirmed genotypic associations may enable patients to be identified who are either at greater risk of developing HF, whose HF may rapidly progress, or who are unlikely to benefit from beta blockers, and such patients may benefit from targeted aggressive therapy.

Genome-wide linkage scan for submaximal exercise heart rate in the HERITAGE family study

The purpose of this study was to identify regions of the human genome linked to submaximal exercise heart rates in the sedentary state and in response to a standardized 20-wk endurance training program in blacks and whites of the HERITAGE Family Study. A total of 701 polymorphic markers covering the 22 autosomes were used in the genome-wide linkage scan, with 328 sibling pairs from 99 white nuclear families and 102 pairs from 115 black family units. Steady-state heart rates were measured at the relative intensity of 60% maximal oxygen uptake (HR60) and at the absolute intensity of 50 W (HR50). Baseline phenotypes were adjusted for age, sex, and baseline body mass index (BMI) and training responses (posttraining minus baseline, Δ) were adjusted for age, sex, baseline BMI, and baseline value of the phenotype. Two analytic strategies were used, a multipoint variance components and a regression-based multipoint linkage analysis. In whites, promising linkages (LOD > 1.75) were identified on 18q21-q22 for baseline HR50 (LOD = 2.64; P = 0.0002) and ΔHR60 (LOD = 2.10; P = 0.0009) and on chromosome 2q33.3 for ΔHR50 (LOD = 2.13; P = 0.0009). In blacks, evidence of promising linkage for baseline HR50 was detected with several markers within the chromosomal region 10q24-q25.3 (peak LOD = 2.43, P = 0.0004 with D10S597). The most promising regions for fine mapping in the HERITAGE Family Study were found on 2q33 for HR50 training response in whites, on 10q25-26 for baseline HR60 in blacks, and on 18q21–22 for both baseline HR50 and ΔHR60 in whites.

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.

The Emerging Pharmacogenomics of the β‐Adrenergic Receptors

Beta-adrenergic signaling mechanisms are of central importance to cardiovascular health and disease. Modulation of these pathways represents an important pharmacologic approach to the treatment of heart failure and hypertension. Advances in molecular genetics have identified genetic polymorphisms in the human beta-adrenergic receptor genes; some of this variation predicts changes in protein sequence/structure, and potentially changes in function, of the b-adrenergic receptors. This article reviews the current state of knowledge and understanding of the genetic variation present in the three human beta-adrenergic receptor genes. Already, variation in these genes has been associated with observed differences in several cardiovascular phenotypes. This work has led to the demonstration of functional differences in activity between receptors with certain known polymorphisms and "wild-type" receptors. An understanding of these polymorphisms is key to the development of studies of how differences in drug response/effects may be mediated by these polymorphisms. Such studies are anticipated to provide a foundation for the development of novel pharmacologic approaches where selection of and dosing of cardiovascular therapy is tailored to individuals on the basis of each patient's specific genetic makeup.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Adrenergic Receptor Polymorphisms Associated with Resting Heart Rate: The HyperGEN Study

The association between polymorphisms in the beta1, beta2 and alpha2B adrenergic receptor (ADR) genes (ADRB1, ADRB2 and ADRA2B) and resting heart rate was examined in white and African-American participants of the HyperGEN Study. All analyses were adjusted for age, sex, body mass index, alcohol use, smoking status and daily exercise within strata of race, hypertension status and beta-blocker use. The Ser49Gly polymorphism of the beta1 ADR was associated with resting heart rate in hypertensive African-Americans and hypertensive whites taking beta-blockers, with carriers of the Gly allele having a higher mean resting heart rate by 2.7 and 4.4 beats per minute (bpm), respectively. The Arg389Gly polymorphism of the beta1 ADR was associated with lower heart rate in the normotensive African-American sample. A beta1 haplotype (Ser49Gly-Arg389Gly) was modestly associated with resting heart rate in the hypertensive African-Americans. The alpha2B C/A polymorphism was associated with heart rate in hypertensive whites, and both whites and African-Americans taking beta-blockers, with carriers of the A allele having a higher mean resting heart rate. In summary, each of the ADR gene polymorphisms was associated with heart rate in at least one stratum studied, but there was no consistent association from which one would infer a large genetic contribution to heart rate.

Influence of phenotype and pharmacokinetics on beta-blocker drug target pharmacogenetics

Two common polymorphisms in the beta1-adrenergic receptor gene, Ser49Gly and Arg389Gly, are associated with variable antihypertensive response to metoprolol. We sought to determine whether similar pharmacogenetic associations were present with the negative chronotropic response phenotype to metoprolol. Metoprolol was titrated in 54 untreated hypertensive patients to achieve blood pressure control. We found no association between either resting or exercise heart rate at baseline (untreated) or in response to metoprolol by codon 389 genotype. In contrast, when compared by codon 49 genotype, Ser49 homozygotes had significantly higher resting heart rates at baseline (untreated) than Gly49 carriers (82+/-10 versus 74+/-11 bpm, respectively, P=0.016). When corrected for plasma concentration, we found no difference in reduction in exercise heart rate in response to metoprolol between Ser49 homozygotes and Gly49 carriers (0.75+/-0.11 versus 0.57+/-0.17%/ng/ml, respectively, P=0.37). However, if one fails to account for plasma concentration, trends toward a significant difference in heart rate reduction are seen between Ser49 homozygotes and Gly49 carriers (31% reduction versus 25% reduction, P=0.05). Our data suggest that neither the beta1-adrenergic receptor Arg389Gly, nor the Ser49Gly polymorphisms are associated with variable negative chronotropic response to metoprolol. In addition, our data highlight the importance of measuring metoprolol concentration in order to account for variable pharmacokinetics and avoid misinterpretation of the data.

Pharmacogenetics of the human beta-adrenergic receptors

The beta-adrenergic receptors (ADRBs) are cell surface receptors that play central roles in the sympathetic nervous system. Pharmacological targeting of two of these receptors, ADRB1 and ADRB2, represents a widely used therapeutic approach for common and important diseases including asthma, hypertension and heart failure. Genetic variation in both ADRB1 and ADRB2 has been linked to both in vitro and clinical disease phenotypes. More recently, interest has shifted to studies that explore potential interaction between variation in ADRBs and medications directed at these important receptors. This paper reviews the current state of knowledge and understanding of ADRB genetic variation and explores the likely direction of future studies in this area.

Role of β1- and α2c-adrenergic receptor polymorphisms and their combination in heart failure: A case-control study

BACKGROUND

Adrenergic activation has a central role in the development of HF. The function of the beta1- and the alpha2C-adrenergic receptors is influenced by gene polymorphisms: the beta1Arg389 variant is associated with increased beta1-receptor sensitivity and the alpha2C-receptor Del322-325 variant is associated with decreased alpha2C receptor function and increased norepinephrine release. We hypothesised that these polymorphisms could influence the prevalence of heart failure.

METHODS

The role of the beta1- and alpha2C-adrenergic receptor gene polymorphisms as risk factors for heart failure (HF) was assessed in an Italian white Caucasian population using a case-control study design. Genomic DNA was analysed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RLFP).

RESULTS

We compared 260 Caucasian patients with HF and 230 normal subjects. The beta1Arg389 allele was frequent both in the patients with HF (69%) and in the normal subjects (73%). The alpha2CDel322-325 variant was rare in both groups (9% and 8%, respectively). Patients homozygotes for either the beta1Arg389 or the alpha(2C)Del322-325 alleles had no increased risk of HF (odds ratio [OR], 0.8; 95%CI: 0.5-1.2 and OR, 0.8; 95% CI: 0.4-1.8, respectively). Patients homozygotes for both the beta1Arg389 and the alpha(2C)Del322-325 alleles had no increased risk of HF as well (OR: 0.6; 95% CI: 0.2-2.1).

CONCLUSIONS

Beta1-ARs and alpha2C-ARs polymorphisms are not associated with an increased risk of HF in an Italian white Caucasian population.

Beta1-adrenergic receptor gene polymorphisms in Mexican patients with idiopathic dilated cardiomyopathy

The objective of the study was to evaluate the role of beta1-adrenergic receptor gene polymorphisms (Ser49Gly and Arg389Gly) as susceptibility markers for idiopathic dilated cardiomyopathy (IDC) in Mexican patients. The polymorphisms were analyzed in 47 patients with IDC and 93 ethnically matched healthy controls by polymerase chain reaction-restriction fragment length polymorphism. The Ser49Gly allele and genotype frequencies were similar in patients and healthy controls. On the other hand, the analysis of the Arg389Gly polymorphism showed an increased frequencies of the *Gly allele (pC = 0.022, OR = 2.16) and *Arg/*Gly genotype (pC = 0.027, OR = 2.70) in the group of IDC patients when compared to healthy controls. The data suggest that Arg389Gly polymorphism could be involved in the genetic susceptibility to develop IDC in Mexicans.

Effects of polymorphisms in β1-adrenoceptor and α-subunit of G protein on heart rate and blood pressure during exercise test. The Finnish Cardiovascular Study

We tested whether the Arg389Gly and Ser49Gly polymorphisms of the β1-adrenergic receptor gene ADRB1 and the T393C polymorphism of the G protein α-subunit gene GNAS1 modulate heart rate (HR) and blood pressure responses during an exercise stress test. The study population comprised 890 participants (563 men and 327 women, mean age 58.1 ± 12.6 yr) of the Finnish Cardiovascular Study. Their HR, systolic (SAP), and diastolic arterial pressures (DAP) at rest, during exercise, and 4 min after the test were measured and analyzed by repeated-measurement ANOVA (RANOVA). Genotypes were detected by TaqMan 5′ nuclease assay. In all subjects, and in men and women separately, the T393C of GNAS1 was the only polymorphism with genotype × time interaction in HR over the three study phases ( P = 0.04, RANOVA). None of the polymorphisms presented genotype × time interaction in SAP or DAP responses ( P > 0.10, RANOVA). In all subjects at rest, the Ser49Gly polymorphism of ADRB1 tended ( P = 0.06, ANOVA) to differentiate HR. Arg389Gly polymorphism of ADRB1 affected maximal SAP during exercise ( P = 0.04, ANOVA) and the change in SAP from rest to maximal ( P = 0.03, ANOVA). Arg389 homozygotes, particularly men, were less likely to have ventricular extrasystoles during the exercise (odds ratio = 0.68, 95% confidence interval = 0.51–0.91, P = 0.009, and odds ratio = 0.60, 95% confidence interval = 0.42–0.86, P = 0.006, respectively) than did Gly389 carriers. In conclusion, polymorphisms examined appear to have modulatory effects on hemodynamics in a clinical exercise test setting. However, the effects in absolute numbers were minor and clinically possibly insignificant.

Distributive characteristics of Ser49Gly and Gly389Arg genetic polymorphisms of beta1-adrenoceptor in Chinese Han and Dai populations

AIM

Genetic polymorphisms causing Ser49Gly and Gly389Arg mutants of beta(1)-adrenoceptor may result in significant changes in the function of this receptor. The aim of the present study was to investigate the frequencies of the Ser49Gly and Gly389Arg mutant alleles in healthy Chinese populations and to investigate the differences between 2 Chinese ethnic groups (Han and Dai populations) with respect to the frequencies of these alleles.

METHODS

A total of 225 Han Chinese and 175 Dai Chinese unrelated healthy volunteers were recruited for this study. Genomic DNA was extracted from peripheral blood leukocytes by using a standard manual chloroform-phenol extraction. Fragments spanning the 2 polymorphisms were amplified by using polymerase chain reaction with template genomic DNA and relevant primers. The DNA products including the polymorphic loci were subjected to restriction endonuclease digestion with Eco0109I and BcgI. Digested fragments were detected with an ultraviolet detector after electrophoresis (100 V for approximately 1.5 h).

RESULTS

The frequencies of the Gly49 and Arg389 alleles were, respectively, 16.2% and 76.4% in the Han population and 14.6% and 75.7% in the Dai population.

CONCLUSION

The polymorphisms causing the Ser49Gly and Gly389Arg mutations of the beta(1)-adrenoceptor existed in both healthy Han and Dai Chinese populations. The frequencies of the Ser49Gly and Gly389Arg mutant alleles were not significantly different in the Han and Dai populations. However, the frequency of the Gly389 variant seems to be significantly lower in these 2 populations than in an African-American population.

The functional significance of genetic variation within the beta-adrenoceptor

The beta-1 adrenoceptor is an archetypal G-coupled protein receptor that controls sympathetic responses in the heart, kidney and adipocytes. It has been widely exploited as a drug target with the development of antagonists to treat cardiovascular diseases such as hypertension, angina and heart failure. Signalling through the receptor is modulated by desensitization and beta1- adrenoceptor down-regulation. It is also affected by in vitro substitution of specific amino acid residues within the beta-1 adrenoceptor. Amino acid substitutions also occur naturally due to polymorphic variation within the human beta-1 adrenoceptor gene itself. Since these variants are common (typically being present in > 5% of the population), the pharmacogenetic implications are enormous. A number of these variants have been identified, although two have been the particular focus of recent publications: a serine to glycine substitution at position 49 (49S > G) and an arginine to glycine at position 389 (389R > G). The data on the in vitro behaviour of these two receptor variants is reviewed here, along with the evidence that they may affect both the risk of cardiovascular disease and the therapeutic response to beta-1 adrenoceptor antagonists.

The Arg389Gly beta1-adrenoceptor gene polymorphism determines contractile response to catecholamines

OBJECTIVES

Recently, the Arg389Gly beta1-adrenoceptor (beta1AR) gene polymorphism has been detected. The Arg variant exhibited increased responsiveness to agonist-induced stimulation in vitro. Functional studies in isolated human atrial muscle strips and in-vivo studies revealed contradictory results regarding the functional relevance of this polymorphism. We sought to characterize the functional consequences of the Arg389Gly beta1-AR polymorphism in 30 consecutive healthy male volunteers in vivo.

METHODS

beta1-AR genotype was determined by PCR and restriction analysis, which was confirmed by DNA sequencing. We compared heart rate, blood pressure, and contractile response of the various genotype carriers with a modified dobutamine stress echocardiography protocol.

RESULTS

Subjects homozygous for the Arg389 beta1AR showed a significantly higher increase in fractional shortening upon cumulative doses of dobutamine as compared to subjects carrying one or two copies of the Gly389 allele. A statistically significant difference was observed at a dobutamine dose of 10 microg/kg/min (46.5 +/- 1.3 vs. 41.8 +/- 1.0 %; P = 0.023) and was maximal at 40 microg/kg/min (61.9 +/- 1.4 vs. 52.8 +/- 1.6; P = 0.001). As a result, the systolic blood pressure response to dobutamine was significantly enhanced in individuals homozygous for the Arg389 allele, whereas the effect on heart rate did not differ between the two groups. Normalization for changing afterload conditions by calculating the pressure-dimension ratio revealed similar effects, indicating that the beta1AR-mediated effects are mainly a result of increased myocardial inotropy.

CONCLUSION

These data indicate that the Arg389Gly beta1AR polymorphism is functionally relevant in vivo and determines contractile responsiveness to catecholamines in humans.

Beta-adrenoceptor polymorphisms and heart failure

Many polymorphisms have been described for the genes encoding the beta 1, beta 2, and alpha 2c-adrenoceptors that result in altered signaling and/or regulatory properties of the receptors. Several studies have investigated whether these properties affect the cardiovascular function of these receptors in mice or in humans, but have yielded mixed results. Some studies suggest that adrenoceptor polymorphisms might alter the risk for heart failure and the response to treatment with beta-blockers. However, the complex haplotypes resulting from combinations of individual polymorphisms have not yet been investigated, and firm conclusions or recommendations cannot be made because of the low patient numbers in each of the study programs.

Autonomic Nervous System Pharmacogenomics: A Progress Report

Pharmacogenetics, the inherited basis for interindividual differences in drug response, has rapidly expanded with the advent of new molecular tools and the sequencing of the human genome, yielding pharmacogenomics. We review here recent ideas and findings regarding pharmacogenomics of components of the autonomic nervous system, in particular, neuronal nicotinic acetylcholine receptors, postsynaptic receptors with which the parasympathetic and sympathetic neurotransmitters, acetylcholine (ACh) and norepinephrine, respectively, interact. The receptor subtypes that mediate these responses, M(1-3) muscarinic cholinergic receptors (mAChRs), and alpha(1A,B,D)-, alpha(2A,B,C)-, and beta(1,2,3)-adrenergic receptors (AR), show highly variable expression of genetic variants; variants of mAChRs and alpha(1)-ARs are relatively rare, whereas alpha(2)-AR and beta-AR subtype variants are quite common. The largest amount of data is available regarding variants of the latter ARs and represents efforts to associate certain receptor genotypes, most commonly, single nucleotide polymorphisms, with particular phenotypes (e.g., cardiovascular and metabolic responses). In vitro and in vivo studies have yielded inconsistent results; definitive conclusions are limited. We identify several conceptual and methodological problems with available data: sample size, ethnicity, tissue differences, coding versus noncoding variants, limited studies of haplotypes, and interaction among variants. Thus, although progress has been made in identifying genetic variation that influences drug response fo autonomic nervous system components, we are still at the early stages of defining the most critical genetic determinants and their role in human physiology and pharmacology.

Beta-adrenergic receptor polymorphism in human cardiovascular disease

Beta-adrenoceptors are polymorphic. Two common polymorphisms in the beta1-adrenoceptor (Ser49Gly and Arg389Gly) and three in the beta2-adrenoceptor (Arg16Gly, Gln27Glu, and Thr164Ile) appear to influence receptor function. In vitro studies of agonist-stimulation have shown that the Gly49 beta1-adrenoceptor and the Gly16 beta2-adrenoceptors are more susceptible to down-regulation, while the Glu27 beta2-adrenoceptor variant seems to be resistant. Whereas the Arg389 beta1-adrenoceptor demonstrates increased responsiveness to agonist stimulation in vitro, the Ile164 beta2-adrenoceptor variant, on the other hand, exhibits a decreased responsiveness. Although several studies in humans (ex vivo and in vivo) do support those functional effects, the literature on the phenotypic consequences of these beta-adrenoceptor polymorphisms in vivo is still far from being conclusive. At present, it appears that these beta-adrenoceptor polymorphisms are very likely not disease-causing genes, but might be risk factors, might modify disease and/or might influence progression of disease.

What is the role of beta-adrenergic signaling in heart failure?

This review addresses open questions about the role of beta-adrenergic receptors in cardiac function and failure. Cardiomyocytes express all three beta-adrenergic receptor subtypes-beta1, beta2, and, at least in some species, beta3. The beta1 subtype is the most prominent one and is mainly responsible for positive chronotropic and inotropic effects of catecholamines. The beta2 subtype also increases cardiac function, but its ability to activate nonclassical signaling pathways suggests a function distinct from the beta1 subtype. In heart failure, the sympathetic system is activated, cardiac beta-receptor number and function are decreased, and downstream mechanisms are altered. However, in spite of a wealth of data, we still do not know whether and to what extent these alterations are adaptive/protective or detrimental, or both. Clinically, beta-adrenergic antagonists represent the most important advance in heart failure therapy, but it is still debated whether they act by blocking or by resensitizing the beta-adrenergic receptor system. Newer experimental therapeutic strategies aim at the receptor desensitization machinery and at downstream signaling steps.

Beta-adrenoceptor polymorphisms

There can be no doubt that beta(1)-, beta(2)- and beta(3)-adrenoceptor genes have genetic polymorphisms. Two single nucleotide polymorphisms have been described for the beta(1)- (Ser49Gly; Gly389Arg), three for the beta(2)- (Arg16Gly; Gln27Glu; Thr164Ile) and one for the beta(3)-adrenoceptor subtype (Trp64Arg) that might be of functional importance. The possibility that changes in expression or properties of the beta-adrenoceptors due to single nucleotide polymorphisms might have phenotypic consequences influencing their cardiovascular or metabolic function or may contribute to the pathophysiology of several disorders like hypertension, congestive heart failure, asthma or obesity is an idea that has attracted much interest during the last 10 years. At present, it appears that these beta-adrenoceptor polymorphisms are very likely not disease-causing genes, but might be risk factors, might modify disease and/or might influence progression of disease. The aim of this review is to provide an overview of the functional consequences of such beta-adrenoceptor polymorphisms in vitro, ex vivo and in vivo.

Cardiovascular pharmacogenomics: current status, future prospects

Pharmacogenomics is a field dedicated to exploring the contribution of genetics to interindividual variability in drug response. A goal of cardiovascular pharmacogenomics is to guide cardiovascular drug development and selection so as to optimize therapeutic benefit and minimize the potential for toxicity. Genetic-based differences in drug metabolism have long been recognized but just now are on the verge of wider clinical application. Differences in efficacy of cardiovascular drugs (independent of drug concentration) based on common genetic variations (polymorphisms) only recently have begun to be explored, but the potential for clinical application appears promising. Examples are presented of important pharmacodynamic effects of genetic variants on several drugs, including those in antiarrhythmic, reninangiotensin, beta-blocker, lipid-lowering, and antithrombotic classes. Principles of pharmacogenomics applied to drug metabolism are discussed that are relevant to drug development and clinical use, and examples are given for CYP450 phase I enzymes, phase II enzymes, and drug transporters. Challenges in establishing true pharmacogenetic associations are discussed, and current and future clinical potential is summarized. Rapid research progress and initial clinical applications with pharmacogenomics are foreseen in the near future.

Clinical importance of beta-adrenoceptor polymorphisms in cardiovascular disease

beta-Adrenoceptor antagonists play an important role in the treatment of cardiovascular disease and have been used for three decades in the treatment of hypertension and ischemic heart disease. More recently they have been demonstrated to improve survival in patients with mild to moderate congestive heart failure. The beneficial effects of beta-adrenoceptor antagonists stems from their ability to limit the deleterious effects of adrenergic stimulation, which in the cardiovascular system is primarily transmitted through two subclasses of receptor, beta(1) and beta(2). The advances of the Human Genome Project have led to an increased appreciation that variations in genetic background may underlie a substantial portion of the clinical heterogeneity apparent in cardiovascular disease. This review examines the molecular, functional, and clinical significance of the most common polymorphisms of the beta(1 and beta(2)-adrenoceptors. Initial research in adrenoceptor variation focused on the beta(2)-adrenoceptor. Three common polymorphisms appear to influence receptor function: Arg16-->Gly, Glu(27)-->Gln, and Thr(164)-->Ile. In in vitro studies of agonist stimulation, Gly(16) receptors demonstrate enhanced downregulation, while Glu(27) variants are resistant to downregulation. There is much controversy and conflict among various clinical studies regarding the effect of these variants on vasoreactivity and hypertensive risk. The Ile(164) variant demonstrates decreased responsiveness to agonist activity both in vitro and in animal models. In studies of patients with congestive heart failure, this variant has been associated with poor functional capacity and decreased survival. More recent investigations have focused on the two common polymorphisms of the beta(1)-adrenoceptor: Ser(49)-->Gly, and Arg(389)-->Gly. In vitro studies of Arg(389) receptors demonstrate a gain of function, as agonist stimulation results in significantly higher intracellular levels of cyclic adenosine monophosphate when compared with the Gly(389) variant. Consistent with the in vitro data, clinical studies demonstrate increased responsiveness to beta-agonist stimulation, and an increased risk of hypertension among Arg(389) homozygotes. Further investigation of the clinical implications of these common variants of beta(1)- and beta2)-adrenoceptors are needed. Importantly, the pharmacogenetic impact of these variants on the effectiveness of beta-adrenergic blockade remains unknown.

Beta-adrenergic receptor polymorphisms: cardiovascular disease associations and pharmacogenetics

The beta-adrenergic receptors (betaAR) play important roles in cardiovascular function and disease, and both agonists and antagonists are widely used in various settings for treatment of cardiovascular disease. Both the beta1AR and beta2AR genes have several polymorphisms that are common in the population and result in encoding of different amino acids. More importantly, in vitro functional studies suggest that these polymorphisms have functional significance. In this review we summarize the literature on the relationship between the betaAR polymorphisms and cardiovascular disease as well as the literature on the impact of these polymorphisms on drug response. Additionally, the polymorphisms in both the beta1AR and beta2AR genes are in linkage disequilibrium; thus, the relevance of single polymorphism vs. haplotype analysis is discussed. Further study of the betaAR genetic polymorphisms is likely to enhance our understanding of cardiovascular disease and improve our use of beta-agonists and beta-antagonists in treatment of cardiovascular disease.

Collection of genomic DNA by the noninvasive mouthwash method for use in pharmacogenetic studies

STUDY OBJECTIVE

To determine long-term stability, quantity, and quality of genomic DNA samples collected in buccal cells by the mouthwash method, for use in pharmacogenetic studies.

DESIGN

Prospective analysis.

SETTING

University pharmacogenomics center in Florida and medical centers in Puerto Rico and the United States participating in a multicenter international trial.

SUBJECTS

Ten volunteers at the pharmacogenomics center and 201 participants in the ongoing multicenter clinical trial.

INTERVENTION

Stability of genomic DNA was determined by measuring DNA yield from mouthwash samples obtained from six volunteers and stored at room temperature over 90 days and from 201 clinical trial samples that were stored and shipped at room temperature. Whether DNA yield was higher with three 5-ml mouthwash rinses versus one 10-ml rinse was evaluated in four volunteers. Quality of genomic DNA was assessed on 32 randomly selected samples from the six volunteers in the stability study, by determining the success rate of DNA amplification with polymerase chain reaction (PCR) testing and by genotyping.

MEASUREMENTS AND MAIN RESULTS

For the stability studies, the quantity of genomic DNA decreased over time with storage at room temperature (overall p < 0.01), with the largest declines occurring at 60 and 90 days. Median DNA recovery at 30 and 90 days was 59% and 28% of that at baseline, respectively. Mean +/- standard deviation, median, and range for recovery of genomic DNA from the 201 samples were 45.2 +/- 55 microg, 25.2 microg, and 1-330 microg, respectively. Median recoveries of DNA from the one-rinse and three-rinse methods were not statistically significantly different (9.1 vs 10.5 microg). All samples were amplified successfully by PCR and genotyped, indicating quality of the DNA samples.

CONCLUSION

The mouthwash method for collection of genomic DNA is a simple, inexpensive, and noninvasive method that poses less risk than venipuncture and may be used in a variety of settings. Genomic DNA in mouthwash is stable for prolonged periods at room temperature, and the quantity of DNA recovered from this method is more than sufficient for pharmacogenetic studies. Such an approach should be valuable to pharmacogenetic researchers and others who are conducting genetic research.

Pharmacogenetics, pharmacogenomics, and cardiovascular therapeutics: the way forward

The completion of sequencing of the human genome will be the vanguard for numerous advances in medicine. The first discernible application is likely to occur in pharmacogenomics, a field focused on the influence of genetic differences on the variability in patients' response to medications. While an inherited basis for drug response has been recognized for some time, it is the confluence of molecular biology, high-throughput genotyping, and bioinformatics that has made it practical to study the genetic basis of variability to medications on a large scale. Pharmacogenomics may enable clinicians to prospectively identify patients most likely to derive benefit from a drug, with minimal likelihood of adverse events. This DNA-based approach to predicting clinical drug efficacy and toxicity would shift the current prescribing paradigm from its empirical nature to a more patient-specific model, ushering in a new era of personalized medicine. Polymorphisms in drug metabolizing enzymes, drug targets, and disease pathogenesis genes are associated with therapeutic effect to cardiovascular pharmacotherapy. Moreover, pharmacogenomics and functional genomics are expected to have a profound impact on the process of drug discovery and development. Finally, pharmacogenomics is likely to transform the way clinical trials are conducted by allowing for the selection of a more homogeneous study population, thereby reducing the size and cost of clinical investigation.