beta-2 Adrenergic receptor variants affect resting blood pressure and agonist-induced vasodilation in young adult Caucasians

Macrophage polarization is involved in liver fibrosis induced by β 1-adrenoceptor autoantibody

Accumulating evidence suggests that liver injury can be induced by the over-expression of β ₁-adrenergic receptors (β ₁-ARs). High titers of autoantibodies specific to β ₁-adrenergic receptors (β ₁-AA) are detected in the sera of heart failure patients, potentially playing agonist-like roles. However, the role of β ₁-AA in liver function has not been characterized. In this study, we collect the sera of primary biliary cholangitis (PBC) patients, a condition which easily develops into liver fibrosis, and analyze the relationship between PBC and β ₁-AA. A passive immunization model is established to assess the effect of β ₁-AA on the liver. Subsequently, the effect of β ₁-AA on macrophages is investigated in vitro. Results show that PBC patients have a high titer and ratio of β ₁-AA, compared to controls. Liver injury and fibrosis are induced by β ₁-AA. In vitro experiments with ROS probe demonstrate that β ₁-AA induces macrophages to produce ROS and secrete TNFα. These effects can be partially reversed by metoprolol, a blocker for β ₁-AR. Results from the transwell and phagocytosis assays show that β ₁-AA promotes macrophage migration and phagocytosis. FCM tests suggest that β ₁-AA induces the alteration of M1 rather than M2 markers in macrophages. Finally, the Annexin V/PI assay indicates that macrophage culture supernatants stimulated by β ₁-AA cause hepatocyte apoptosis. Overall, these results suggest that β ₁-AA is involved in PBC. The β ₁-AA-induced activation, phagocytosis and phenotypic modification of macrophages may play an important role in the development of hepatic fibrosis and injury.

Genetic Predictors of Salt Sensitivity of Blood Pressure: The Additive Impact of 2 Hits in the Same Biological Pathway

[Figure: see text].

Association between ß2-adrenergic receptor gene polymorphisms and adverse events of ritodrine in the treatment of preterm labor: a prospective observational study

Background

Ritodrine, a tocolytic β2-agonist, has been used extensively in Europe and Asia despite its safety concerns. This study was designed to identify associations between β2-adrenergic receptor (ADRB2) polymorphisms and adverse drug events (ADEs) in patients with preterm labor treated with ritodrine.

Results

This follow-up study was prospectively conducted at Ewha Womans University Mokdong Hospital in Korea. Five single nucleotide polymorphisms (SNPs) of the ADRB2 gene (rs1042713, rs1042714, rs1042717, rs1042718, and rs1042719) were analyzed in 186 pregnant women with preterm labor. Patients with the AA genotype of rs1042717 had significantly lower incidence of ADEs compared to those with the G allele (p = 0.009). In multivariate analysis, one of the predictors of ADEs was the maximum infusion rate of ritodrine (AOR 4.47, 95% CI 1.31–15.25). Rs1042719 was also a significant factor for ritodrine-induced ADEs. The CC genotype carriers had 78% decreased risk of ADEs compared to those with other genotypes.

Conclusions

This study demonstrates that ADEs induced by ritodrine are associated with ADRB2 gene polymorphisms, as well as the infusion rate of ritodrine in pregnant women with preterm labor.

Population differences in associations of serotonin transporter promoter polymorphism (5HTTLPR) di- and triallelic genotypes with blood pressure and hypertension prevalence

Based on prior research finding the 5HTTLPR L allele associated with increased cardiovascular reactivity to laboratory stressors and increased risk of myocardial infarction, we hypothesized that the 5HTTLPR L allele will be associated with increased blood pressure (BP) and increased hypertension prevalence in 2 large nationally representative samples in the United States and Singapore.

METHODS

Logistic regression and linear models tested associations between triallelic (L'S', based on rs25531) 5HTTLPR genotypes and hypertension severity and mean systolic and diastolic blood pressure (SBP and DBP) collected during the Wave IV survey of the National Longitudinal Study of Adolescent to Adult Health (Add Health, N=11,815) in 2008-09 and during 2004-07 in 4196 Singaporeans.

RESULTS

In US Whites, L' allele carriers had higher SBP (0.9 mm Hg, 95% CI=0.26-1.56) and greater odds (OR=1.23, 95% CI=1.10-1.38) of more severe hypertension than those with S'S' genotypes. In African Americans, L' carriers had lower mean SBP (-1.27mm Hg, 95% CI=-2.53 to -0.01) and lower odds (OR = 0.78, 95% CI=0.65-0.94) of more severe hypertension than those with the S'S' genotype. In African Americans, those with L'L' genotypes had lower DBP (-1.13mm Hg, 95% CI=-2.09 to -0.16) than S' carriers. In Native Americans, L' carriers had lower SBP (-6.05mm Hg, 95% CI=-9.59 to -2.51) and lower odds of hypertension (OR = 0.34, 95% CI=0.13-0.89) than those with the S'S' genotype. In Asian/Pacific Islanders those carrying the L' allele had lower DBP (-1.77mm Hg, 95% CI=-3.16 to -0.38) and lower odds of hypertension (OR = 0.68, 95% CI=0.48-0.96) than those with S'S'. In the Singapore sample S' carriers had higher SBP (3.02mm Hg, 95% CI=0.54-5.51) and DBP (1.90mm Hg, 95% CI=0.49-3.31) than those with the L'L' genotype.

CONCLUSIONS

These findings suggest that Whites carrying the L' allele, African Americans and Native Americans with the S'S' genotype, and Asians carrying the S' allele will be found to be at higher risk of developing cardiovascular disease and may benefit from preventive measures.

The Gly16 Allele of the Gly16Arg Single-Nucleotide Polymorphism in the β₂-Adrenergic Receptor Gene Augments Perioperative Use of Vasopressors: A Retrospective Cohort Study

BACKGROUND

Arterial hypotension is frequent in patients undergoing anesthesia and may aggravate the outcome. Common genetic variations may influence the cardiovascular response to anesthesia. In this retrospective cohort study, we tested whether variation in the gene encoding the β2-adrenergic receptor (ADRB2) influences perioperative arterial blood pressure and consequently the use of vasopressors.

METHODS

Five hundred seventy-one Danish Caucasians undergoing neurosurgery were genotyped for 5 marker single-nucleotide polymorphisms (SNPs) within ADRB2 (Gly16Arg, Gln27Glu, Thr164Ile, Arg175Arg, and Gly351Gly). A pairwise tagging principle was used to identify ADRB2 haplotypes. Mean arterial blood pressure (MAP) was recorded in the supine awake state and, together with administration of vasopressors (ephedrine and/or phenylephrine), for 30 minutes after induction of general anesthesia (sevoflurane/remifentanil or propofol/remifentanil).

RESULTS

Four hundred thirteen (72%) patients received ephedrine and/or phenylephrine. Only baseline MAP (P < 0.001) and the Arg175Arg SNP (P = 0.01) were associated with nadir perioperative MAP. The Gly16Arg SNP but no other SNPs showed a trend toward an association with the amount of vasopressors used during anesthesia with Arg16 homozygotes receiving less ephedrine equivalents. The Arg16-Gln27-Thr164-Arg175-Gly351 haplotype was associated with approximately 13% lower vasopressor requirements than the most common Gly16-Glu27-Thr164-Arg175-Gly351 haplotype (P = 0.01).

CONCLUSIONS

Gly16 carriers received larger amounts of vasopressor compared with Arg16 homozygotes. This corresponds to previous studies demonstrating that the Gly16 allele in ADRB2 is associated with vasodilation and high cardiac output.

Roles of catecholamine related polymorphisms in hypertension

The objective of this review is to summarize current data obtained so far in catecholamine-essential hypertension (EH) relationships on a genetic basis. As the major elements driving the sympathetic system’s actions, catecholamines modulate a variety of physiological processes and mutations related to the system. This could generate serious disorders, such as severe mental illnesses, stress-induced disorders, or impaired control of blood pressure or motor pathways. EH is idiopathic, and the genetic basis of its causes and substantial interindividual discrepancies in response to different types of treatments are the focus of interest. Susceptibility to disease or efficacy of treatments are thought to reflect genomic variabilities among individuals. Therefore, outlining the available knowledge in functional genetic polymorphisms linked to EH will make the picture clearer and will help to establish future prospects in the field.

Ephedrine requirements during spinal anesthesia for cesarean delivery in Jordanian parturients: association with b2 adrenoceptor gene variants

BACKGROUND

Maternal hypotension after spinal anesthesia for cesarean delivery is common. Many studies performed on the b2-adrenoceptor (b2AR) gene variants and their association with vasopressor requirements during and after neuroaxial block have contradictory conclusions.

OBJECTIVES

The aim of the study was to evaluate the influence of the b2AR in codons 16 and 27 on the incidence of maternal hypotension and ephedrine consumption after spinal anesthesia for cesarean delivery in an Arab ethnic group.

DESIGN

A prospective gene association study.

SETTING

Jordan University Hospital from 1 July 2013 to 31 January 2014.

PATIENTS AND METHODS

We enrolled parturients who underwent cesarean delivery under spinal anesthesia. Spinal anesthesia was performed with 10 mg plain bupivacaine along with 25 micro g fentanyl. Hypotension was treated with ephedrine and the amount consumed in the first 30 minutes after spinal anesthesia was calculated. The b2AR genotype at codons 16 and 27 was determined. We studied the correlation between the b2AR genotype and the amount of ephedrine consumption after spinal anesthesia.

MAIN OUTCOME MEASURES

Amount of ephedrine used.

RESULTS

Of 250 patients enrolled in the study, genotype and clinical data were available for 234 cases. Ephedrine was used in 94% of patients. There was a significant effect of b2AR genotype on ephedrine dose in the first 30 minutes after spinal anesthesia in codon 16 and 27. Arg16 homozygotes received less ephedrine (14.0 [11.2] mg) than Gly16 homozygotes (38.6 [25.7] mg) and Arg16Gly heterozygotes (33.42 [22.70] mg) (P < .0001). Gln27 homozygotes received less ephedrine (18.2 [12.8] mg) than Glu 27 homozygotes (47.5 [27.0] mg) and Gln27Glu heterozygotes (48.2 [23.7] mg). (P < .0001).

CONCLUSION

In an Arab ethnic group, the b2AR gene has a role in maternal hypotension after spinal anesthesia. The Gly16 and Glu27 alleles have a higher incidence of arterial hypotension and required a greater amount of vasopressor to treat hypotension compared with homozygous Arg16 and Gln27 carriers.

LIMITATIONS

Fasting time and hydration protocol, the use of a fixed dose of ephedrine, and relatively small sample size.

Association of the ADRB2 Gly16Arg and Glu27Gln polymorphisms with athlete status

The β-adrenergic receptors (β-ARs) have known functional roles in cardiovascular and pulmonary responses as well as the appropriate substrate metabolism required for athletic ability. Thus, the β-AR genes are plausible candidates for the variations observed in strength/power and endurance performance levels. The aims of the present study were to compare the frequency distribution of the ADRB2 Gly16Arg and ADRB2 Glu27Gln polymorphisms among athletes of sports with different metabolic and cardiopulmonary demands (endurance vs. strength/power) and to test the association between the Gly16Arg and Glu27Gln genotypes and athlete status. The study was performed in a group of 223 Polish athletes of the highest nationally competitive standard (123 endurance-oriented athletes and 100 strength/power athletes). Control samples were prepared from 354 unrelated, sedentary volunteers. The χ² test of independence revealed that the frequencies of the Gly16 and Glu27 alleles were significantly higher in the strength/power athletes than in the controls (69.0% vs. 59.7%; df = 1, P = 0.017 and 51% vs. 41.5%; df = 1 P = 0.017, respectively). The study showed that ADRB2 Gly16Arg and Glu27Gln markers are associated with athlete status in Polish athletes. An excess of Gly16 and Glu27 alleles and the Gly16:Glu27 haplotype observed in the strength/power athlete subgroup suggests that the Gly16 and Glu27 alleles might increase the probability of becoming a strength/power athlete rather than an endurance-oriented athlete.

The complex interaction between overweight, hypertension, and sympathetic overactivity

There is ample evidence in the epidemiological and clinical literature that hypertension and overweight are closely and causally interrelated. Sympathetic nervous system (SNS) overactivity has been well documented in both hypertension and overweight, but it is not clear whether this is a coincidental finding or whether the association reflects a mechanistic role of SNS in these two interrelated clinical conditions. Whereas in this review we focus on the evidence for a primary role of SNS in the development of hypertension and overweight, it is clear that the process can be initiated from other starting points such as primary overeating or sleep apnea. After overweight evolves, hormones secreted by fat cells further accelerate SNS overactivity, weight gain, and blood pressure increase. The main thesis of this article is that regardless of where the process started, the same clinical picture of hypertension, overweight, and SNS overactivity will emerge. There is good evidence that in genetically prone individuals, prolonged SNS stimulation elicits a down regulation of beta-adrenergic receptors. This in turn decreases the ability to dissipate calories and diminishes the beta-adrenoceptor-mediated vasodilatation. We hypothesize that beta-adrenoceptor downregulation is the linchpin in the association of SNS with overweight and hypertension.

Stimulation of gastric slow waves with manual acupuncture at acupuncture points ST36 and PC6--a randomized single blind controlled trial

BACKGROUND

To investigate the effects of stimulated and non-stimulated manual acupuncture at ST36 and PC6 on gastric myoelectrical activity and autonomic function.

METHODS

A total of 65 healthy volunteers were randomly assigned to a 1: 1: 2 ratio to receive either 15 min of verum acupuncture (VA) with stimulation followed by 15 min of VA without stimulation (nsVA), or 15 min of nsVA followed by 15 min of VA with stimulation (sVA), or 30 min of sham acupuncture (SA). Measures of autonomic function included electrogastrogram, electrocardiogram, impedance cardiography and assessment of blood pressure, breathing frequency, and electrodermal activity. Outcome parameters were compared between VA and SA, and between sVA and nsVA. The percentage of regular gastric slow waves (normogastria) was defined as the primary outcome.

KEY RESULTS

The percentage of normogastria was not significantly different between VA and SA. Differences in secondary outcomes such as power spectrum of gastric slow waves and heart rate variability parameters were pronounced in the comparison of sVA and nsVA. During sVA, the percentage of normogastria was lower (P = 0.005), the percentage of bradygastria was higher (P = 0.003) and power ratio was higher (P < 0.001), systolic blood pressure was lower (P = 0.039) and RMSSD was higher (P < 0.001) as compared with nsVA.

CONCLUSIONS & INFERENCES

Our study suggests that manual stimulation of acupuncture needles at ST36 and PC6 affects gastric myoelectrical as well as cardiac activities in healthy volunteers. The effect of stimulation in acupuncture deserves further investigation.

Beta-2 adrenoreceptor gene polymorphisms and sympathetic outflow in humans

OBJECTIVES

Previous association studies suggested that common polymorphisms of the beta-2 adrenoreceptor gene leading to glycine for arginine substitution at position 16 or glutamic acid for glutamine substitution at position 27 affect blood pressure. We reasoned that measurements of resting sympathetic nerve traffic could increase the sensitivity of defining a gene phenotype relationship.

METHODS

We studied 111 Caucasian subjects (70 men, 41 women) with blood pressure<140/90 mmHg. We measured electrocardiogram, beat-by-beat finger blood pressure, brachial blood pressure, and muscle sympathetic nerve activity (MSNA) using microneurography. We genotyped the functionally relevant polymorphisms of the beta-2 adrenoreceptor gene by means of allele-specific polymerase chain reaction.

RESULTS

Sympathetic nerve traffic was similar regardless of genotypes. We obtained similar results when we quantified sympathetic nerve traffic as bursts/100 heart beats or as normalized burst area or when we adjusted resting sympathetic nerve traffic for gender, age, and blood pressure. The polymorphism at position 27 affects sympathetic regulation in men. Men with a Glu/Glu genotype had a significant positive correlation between blood pressure and MSNA.

INTERPRETATIONS

While our study was not sufficiently powered to detect subtle influences of genetic variability in the beta-2 adrenoreceptor gene on resting sympathetic nerve traffic, a large effect is unlikely. However the observation that beta-2 adrenoreceptor genotype may affect coupling between resting sympathetic nerve traffic and systolic blood pressure deserves to be tested in larger populations.

Genetic polymorphisms of the beta2-adrenergic receptor relate to guanosine protein-coupled stimulator receptor dysfunction in fibromyalgia syndrome

OBJECTIVE

To determine the genotype frequencies of ß(2)-adrenergic receptor (ß(2)AR) gene polymorphisms (Gly16Arg, Glu27Gln) in patients with fibromyalgia syndrome (FM) by comparison with unrelated healthy controls. We sought any clinical association with these polymorphisms and determined whether the polymorphisms would associate with a biologic guanosine protein-coupled stimulator receptor (Gs) dysfunction in FM.

METHODS

Study subjects included 97 clinically characterized patients with FM and 59 controls. The ß(2)AR polymorphisms at codons 16 and 27 were determined using polymerase chain reaction-restriction fragment length polymorphism. The Gs functions of peripheral blood mononuclear cells (PBMC) were tested using isoproterenol (ISO) as the adrenergic Gs ligand and measuring intracellular cyclic adenosine monophosphate (cAMP) levels.

RESULTS

The frequency of the ß(2)AR gene polymorphism Gly16Arg in FM (43.5%) was significantly lower than in controls (63.2%), suggesting that this genotype might have some effect on the risk of developing FM. The only clinical association in FM was with sleep dysfunction. Patients with FM who carried the ß(2)AR polymorphism Arg16Arg also exhibited significantly lower PBMC basal cAMP levels (p < 0.05) and lower ISO-stimulated cAMP levels (p < 0.05) than FM carrying Gly16Gly or Gly16Arg.

CONCLUSION

This confirms a relationship between ß(2)AR polymorphism and FM. It is the first study to demonstrate ß(2)AR polymorphism-related differences in intracellular cAMP responses of FM PBMC after ß(2)AR stimulation in vitro. These findings may explain some of the differences in responsiveness of FM subgroups to the adrenergic agonist medications currently approved for FM treatment.

Modulation of the BP response to diet by genes in the renin-angiotensin system and the adrenergic nervous system

BACKGROUND

Essential hypertension results from the interaction of several genetic and environmental factors. Identification of genetic factors that modulate blood pressure (BP) response to interventions can lead to improved strategies for prevention and control. The purpose of this study was to identify genes that modulate BP response to dietary interventions.

METHODS

We used data and samples collected in two randomized feeding studies to determine the extent to which genetic architecture is associated with the effect on BP of sodium intake and the Dietary Approaches to Stop Hypertension (DASH) dietary pattern. Participants in both trials were adults with above-optimal BP or unmedicated stage 1 hypertension. Genomic DNA was typed for several candidate genes.

RESULTS

The effect of sodium intake on BP differed by genotype at the angiotensinogen, β2-adrenergic receptor, and kallikrein loci. The effect of DASH dietary pattern on BP differed by genotype at the β2-adrenergic receptor locus.

CONCLUSIONS

These findings have implications for understanding the mechanism(s) through which diet affects BP, the heterogeneity of these effects, and the extent to which dietary interventions can modulate genetic predisposition.

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.

Roles of beta2- and beta3-adrenoceptor polymorphisms in hypertension and metabolic syndrome

Hypertension, diabetes mellitus (especially type 2 diabetes mellitus), metabolic syndrome and obesity are rapidly growing public health problems. Sympathetic nerve activation is observed in obesity, hypertension and diabetes mellitus, which 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 have been mainly mediated via the β2- and β3-adrenergic receptors in humans. Further, β2-adrenoceptors importantly influence vascular reactivity and may regulate blood pressure. Genetic polymorphistns of the β-adrenoceptor gene have been shown to alter the function of several adrenoceptor subtypes and thus to modify the response to catecholamine. β2-adrenoceptor polymorphisms (Arg16Gly, Gln27Glu, and Thr164Ile) have been studied in relation to hypertension. Genetic variations in the β3-adrenoceptor (i.e. Try64Arg variant) are also associated with both obesity and hypertension. However, the precise relationships of the polymorphisms of β2- and β3-adrenoceptor genes with sympathetic nervous system activity, hypertension, and metabolic syndrome have not been fully clarified. This paper will discuss the current topics involving the influence of the sympathetic nervous system and β2- and β3- adrenoceptor polymorphisms in hypertension and metabolic syndrome.

A high-fat meal impairs muscle vasodilatation response to mental stress in humans with Glu27 beta2-adrenoceptor polymorphism

Background

Forearm blood flow responses during mental stress are greater in individuals homozygous for the Glu27 allele. A high-fat meal is associated with impaired endothelium-dependent dilatation. We investigated the impact of high-fat ingestion on the muscle vasodilatory responses during mental stress in individuals with the Glu27 allele and those with the Gln27 allele of the β₂-adrenoceptor gene.

Methods

A total of 162 preselected individuals were genotyped for the Glu27Gln β₂-adrenoceptor polymorphism. Twenty-four individuals participated in the study. Fourteen were homozygous for the Gln27 allele (Gln27Gln, 40 ± 2 years; 64 ± 2 kg), and 10 were homozygous for the Glu27 allele (Glu27Glu, 40 ± 3 years; 65 ± 3 kg). Forearm blood flow was evaluated by venous occlusion plethysmography before and after ingestion of 62 g of fat.

Results

The high-fat meal caused no changes in baseline forearm vascular conductance (FVC, 2.2 ± 0.1 vs. 2.4 ± 0.2; P = 0.27, respectively), but reduced FVC responses to mental stress (1.5 ± 0.2 vs. 0.8 ± 0.2 units; P = 0.04). When volunteers were divided according to their genotypes, baseline FVC was not different between groups (Glu27Glu = 2.4 ± 0.1 vs. Gln27Gln = 2.1 ± 0.1 units; P = 0.08), but it was significantly greater in Glu27Glu individuals during mental stress (1.9 ± 0.4 vs. 1.0 ± 0.3 units; P = 0.04). High-fat intake eliminated the difference in FVC responses between Glu27Glu and Gln27Gln individuals (FVC, 1.3 ± 0.4 vs. 1.2 ± 0.4; P = 0.66, respectively).

Conclusion

These findings demonstrate that a high-fat meal impairs muscle vasodilatation responses to mental stress in humans. However, this reduction can be attributed to the presence of the homozygous Glu27 allele of the β₂-adrenoceptor gene.

beta2-Adrenoceptor gene variation and systemic vasodilatation during ganglionic blockade

Regional infusions of beta(2)-adrenoceptor (ADRB2) agonist have generally shown that individuals homozygous for Gly16 produces greater vasodilatation than those homozygous for Arg16. Systemic infusions have shown an opposite effect on systemic vascular resistance (SVR), possibly confounded by baroreflexes or interactions between single nucleotide polymorphism (SNP) positions 16 and 27. We tested the hypothesis that ADRB2 gene variation would influence the SVR response to ADRB2 agonist terbutaline (Terb) during ganglionic blockade. Forty healthy young adults were recruited according to the double homozygous haplotypes: Arg16 + Gln27 (n = 13), the rare Gly16 + Gln27 (n = 6), and Gly16 + Glu27 (n = 21). Arterial pressure was measured by brachial arterial catheter, and cardiac output by acetylene breathing. Lymphocytes were sampled for ex vivo analysis of ADRB2 density and binding conformation. Following baroreflex ablation with trimethaphan (3-7 mg min(1)), continuous phenylephrine was titrated to restore blood pressure to baseline. Terb was infused i.v. at 33 and 67 ng kg(1) min(1) for 15 min/dose. There was partial evidence to suggest a main effect of haplotype on the change in SVR (P = 0.06). For SNP position 16, the highest dose of Terb produced lower SVR in Gly16 (mean +/- s.e.m.: 7.5 +/- 0.4) vs. Arg16 (8.9 +/- 0.7 units; P = 0.03). Lymphocyte ADRB2 binding conformation was similar but receptor density was greater in Gly16 vs. Arg16 (P = 0.05). We conclude that during ganglionic blockade, the SVR response to systemic ADRB2 agonist is suggestive of augmented ADRB2 function in Gly16 + Glu27 homozygotes, with greater influence from Gly16, providing further evidence that ADRB2 gene variation influences vasodilatation.

Beta-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and beta-adrenergic receptor (beta-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between beta(1)-AR (Arg389Gly) and beta(2)-AR (Arg16Gly, Gln27Glu) gene variants and cardiovascular reactivity in 500 Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure reactivity were measured during cold and psychological stress. The Arg389Gly polymorphism in the beta(1)-AR was associated with preejection period reactivity in males but not in females. The Arg16Gly polymorphism in the beta(2)-AR was associated with diastolic blood pressure reactivity only during video game stress. An association between the Gln27Glu polymorphism in the beta(2)-AR and vascular reactivity depended on sex. Thus, specific patterns of associations emerged between genetic variations in beta-ARs and cardiovascular reactivity in young Blacks.

{beta}-Adrenoceptor gene variation and intermediate physiological traits: prediction of distant phenotype

Intermediate physiological phenotype is the genetic and environmental influence on functional physiological characteristics with direct prognostic relevance to distant, more complex phenotypes, such as cardiovascular and metabolic disease. Increasingly available and affordable genotyping techniques have created an explosion of information on candidate gene variation and its relationship to intermediate physiological traits. Variation in beta-adrenoceptor genes is an intense focus of investigation because beta-adrenoceptors are: (1) ubiquitous in organ system distribution; (2) integral to a multitude of physiological processes; (3) well described in cardiovascular and metabolic disease; and (4) major pharmacological treatment targets. Furthermore, knowledge of functional gene variants in these receptors predates the description of the human genome. This review highlights the influence of common gene variation in the three beta-adrenoceptor subtypes on intermediate physiological phenotype predictive of cardiovascular disease and obesity. Although further information is needed to replicate this information across populations, this review condenses and summarizes growing trends in specific pleiotropic effects of beta-adrenoceptor polymorphisms and suggests which variants may be predictive of distant phenotype.

Combination of polymorphisms in the beta2-adrenergic receptor and nitric oxide synthase 3 genes increases the risk for hypertension

OBJECTIVE

Hypertension is a major risk factor for cardiovascular disease. Polymorphism in the beta2-adrenergic receptor (ADRB2) and nitric oxide synthase 3 (NOS3) genes is associated with clinical cardiovascular phenotypes. The Arg16Gly and Glu298Asp polymorphisms of ADRB2 and NOS3 genes, respectively, have been reported to be associated with hypertension. We hypothesized that a combination of these two polymorphisms increases the risk for hypertension. Hence, we examined the effect of this combination of single-nucleotide polymorphisms on the risk for hypertension.

METHODS

Our cross-sectional study comprised 402 middle-aged and elderly human participants. We determined the genotypes of Arg16Gly and Glu298Asp single-nucleotide polymorphisms in ADRB2 and NOS3, respectively, by TaqMan PCR method; we also measured the resting blood pressure.

RESULTS

The odds ratio for the presence of hypertension in individuals having the Gly/Gly genotype of ADRB2 compared with those having the other genotypes (Arg/Arg and Arg/Gly) was 2.87. With regard to the Glu298Asp polymorphism in NOS3, the odds ratio for the presence of hypertension in individuals having the Glu/Glu genotype of NOS3 when compared with those having the other genotypes (Asp/Asp and Asp/Glu) was 2.79. Interestingly, the odds ratio was 7.64 for individuals having a combination of the Gly/Gly genotype of ADRB2 and Glu/Glu genotype of NOS3 when compared with those having a combination of Arg/Arg and Arg/Gly genotypes of ADRB2 and Asp/Asp and Asp/Glu genotypes of NOS3.

CONCLUSION

We revealed that a combination of the Arg16Gly and Glu298Asp polymorphisms in ADRB2 and NOS3, respectively, remarkably increased the risk for hypertension in middle-aged and elderly humans.

Prevalence of beta-2 adrenergic receptor (beta 2 AR) polymorphisms and its influence on a model used to assess endothelial function using pulse wave analysis (PWA)

BACKGROUND

Pulse wave analysis (PWA) combined with beta(2)-agonist challenge has recently been used to assess endothelial function. beta-2 adrenergic receptor (beta(2)AR) polymorphisms may affect response to beta(2)-agonist. We determined whether beta(2)AR polymorphisms influence endothelial response in our model using PWA and salbutamol.

METHODS

388 healthy Malay subjects (177 males, 211 females) were genotyped for 5 functionally important single nucleotide polymorphisms (SNPs) of beta(2)AR; 298 subjects proceeded with assessment of endothelial function. The parameter augmentation index (AIx) was recorded non-invasively using SphygmoCor. Recording of AIx at baseline was followed by administration of 500 microg sublingual glyceryl trinitrate (GTN). AIx recordings were repeated at 3, 5, 10, 15 and 20 min post-GTN. Subjects then inhaled 400 microg of salbutamol before AIx recordings at 5 min intervals up to 20 min. Maximum changes in AIx after GTN and salbutamol represented endothelium independent and endothelium dependent vasodilatation (EDV) respectively.

RESULTS

Allele frequencies of mutated Gly16, Glu27, Ile164, -20C and -47C were 47%, 6.8%, 0%, 30% and 9.3% respectively. No significant differences in EDV were noted between genotype groups of each studied SNPs.

CONCLUSIONS

Assessment of endothelial function using PWA and salbutamol was not influenced by beta(2)AR polymorphisms.

Arg347Cys polymorphism of alpha1A-adrenoceptor gene is associated with blood pressure response to nifedipine GITS in Chinese hypertensive patients

Our objectives were to evaluate whether polymorphisms in the alpha1A- and beta2-adrenoceptor genes influence blood pressure response to nifedipine gastrointestinal therapeutic system (GITS). Hypertensive patients received daily treatment with an oral dosage of 30 mg nifedipine GITS for 16 days. Genotypes of the Arg347Cys polymorphism in the alpha1A-adrenoceptor gene and the Arg16Gly and Gln27Glu polymorphisms in the beta2-adrenoceptor gene were determined by TaqMan single-nucleotide polymorphism genotyping assay. The sixteenth-day steady-state plasma concentration of nifedipine was measured using HPLC with UV detection. Multivariate linear regression was performed in a total of 447 patients to evaluate the effects of these polymorphisms on blood pressure response to nifedipine GITS. Patients carrying the Cys347 allele of the alpha1A-adrenoceptor gene had a greater systolic blood pressure reduction than did those carrying two Arg347 alleles of the alpha1A-adrenoceptor gene (32.5+/-14.0 versus 27.3+/-15.5 mm Hg, respectively, P=0.006). However, diastolic blood pressure reduction was not associated with the Arg347Cys polymorphism in the alpha1A-adrenoceptor gene. In addition, no significant associations were observed between blood pressure reduction and two polymorphisms in the beta2-adrenoceptor gene. Our data suggest that the Arg347Cys polymorphism in the alpha1A-adrenoceptor gene may be used to predict blood pressure response to nifedipine GITS in Chinese hypertensive patients.

Polymorphisms determine beta-adrenoceptor conformation: implications for cardiovascular disease and therapy

Beta(1)- and beta(2)-adrenoceptors are crucial regulators of cardiovascular function. Agonists and antagonists at these receptor subtypes are cornerstones in the treatment of cardiovascular disease. In humans, both of the genes encoding the beta(1)- and beta(2)-adrenoceptors carry frequent polymorphisms resulting in different variants of the receptor proteins. Whether the polymorphic nature of the receptors causes the clinically observed differences with respect to the response of the patients to therapeutic drugs is currently a matter of intense discussion. Here, we discuss recent progress regarding the determination of beta-adrenoceptor conformational changes and how these can help to clarify this issue. Specifically, novel optical methods enable us to directly assess the functional importance of beta-adrenoceptor polymorphisms on ligand-induced changes of receptor conformation. The ability to determine polymorphism-dependent differences in drug efficacy directly on the receptor level might develop into an important approach to establish individualized drug therapies based on the genetic determinants of the patients.

Identifying genes for primary hypertension: methodological limitations and gene-environment interactions

Hypertension segregates within families, indicating that genetic factors explain some of the variance in the risk of developing the disease; however, even with major advances in genotyping technologies facilitating the discovery of multiple genetic risk markers for cardiovascular and metabolic diseases, little progress has been made in defining the genetic defects that cause elevations in blood pressure. Several plausible explanations exist for this apparent paradox, one of which is that the risk conveyed by genes involved in the development of hypertension is context dependent. This notion is supported by a growing number of published animal and human studies, although none has yet provided unequivocal evidence that genetic and environmental factors interact to influence the risk of primary hypertension in humans. In this review, an assumption is made that common genetic variation contributes meaningfully to the development of primary hypertension. The review focuses on (i) several methodological limitations of genetic association studies and (ii) the roles that gene-environment interactions might play in the development of primary hypertension. The proceeding sections of the review examine the design features necessary for future studies to adequately test the hypothesis that genes for primary hypertension act in a context-dependent manner. Finally, an outline of how knowledge of gene-environment interactions might be used to optimize the prevention or treatment of primary hypertension is provided.

GENETIC VARIATION IN THE β(2)-ADRENERGIC RECEPTOR: IMPACT ON INTERMEDIATE CARDIOVASCULAR PHENOTYPES

Genetic variation in drug targets (e.g. receptors) can have pronounced effects on clinical responses to endogenous and exogenous agonists. Polymorphisms in the gene encoding the β(2)-adrenergic receptor (β(2)-AR) have been associated with altered expression, down-regulation, and altered cell signaling in vitro. Because β(2)-ARs play a crucial role in the regulation of the cardiovascular system, the functional importance of genetic variation in the β(2)-AR on cardiovascular responses to physiological or pharmacological stimuli has gained widespread attention. The objective of this review is to characterize these intermediate cardiovascular phenotypes and their influence on cardiovascular disease and adrenergic drug responses.Two common single nucleotide polymorphisms, encoded at codon 46 (Gly(16)Arg) and 79 (Gln(27)Glu) of the β(2)-AR gene, have been studied intensively. They have been shown to be associated with altered vasodilator responses to regional and systemic administration of β(2)-agonists, altered cardiovascular responses to sympathoexcitatory maneuvers, and altered myocardial function. Importantly, these intermediate physiological patterns may influence the development of and the outcomes associated with hypertension and other cardiovascular diseases. As recently reported, β(2)-AR gene variation can risk-stratify patients receiving β-blocker therapy and may predict β-blocker efficacy in patients post acute coronary syndrome or in patients with heart failure.Further studies will advance our understanding of the link between β(2)-AR genotypes, intermediate cardiovascular phenotypes, and clinical phenotypes. In the long term, reassessment of the benefits of β-blocker-therapy within genotype groups should be carried out with the ultimate goal to design the optimal therapeutic regimen for the individual patient.

A review of methods for assessment of coronary microvascular disease in both clinical and experimental settings

Obstructive disease of the large coronary arteries is the prominent cause for angina pectoris. However, angina may also occur in the absence of significant coronary atherosclerosis or coronary artery spasm, especially in women. Myocardial ischaemia in these patients is often associated with abnormalities of the coronary microcirculation and may thus represent a manifestation of coronary microvascular disease (CMD). Elucidation of the role of the microvasculature in the genesis of myocardial ischaemia and cardiac damage-in the presence or absence of obstructive coronary atherosclerosis-will certainly result in more rational diagnostic and therapeutic interventions for patients with ischaemic heart disease. Specifically targeted research based on improved assessment modalities is needed to improve the diagnosis of CMD and to translate current molecular, cellular, and physiological knowledge into new therapeutic options.

Childhood socioeconomic status and serotonin transporter gene polymorphism enhance cardiovascular reactivity to mental stress

OBJECTIVE

To test the hypothesis that low socioeconomic status (SES) and the 5HTTLPR L allele are associated with increased cardiovascular reactivity (CVR) to stress in a larger sample and that SES and 5HTTLPR genotypes interact to enhance CVR to stress. CVR to mental stress has been proposed as one mechanism linking stress to the pathogenesis of cardiovascular disease. The more transcriptionally efficient long (L) allele of a polymorphism of the serotonin transporter gene promoter (5HTTLPR) has been found associated with increased risk of myocardial infarction. We found the long allele associated with larger CVR to mental stress in a preliminary study of 54 normal volunteers.

METHODS

Subjects included 165 normal community volunteers stratified for race, gender, and SES, who underwent mental stress testing.

RESULTS

Childhood SES as indexed by Father's Education Level was associated with larger systolic blood pressure (SBP) (p < .05) and diastolic blood pressure (DBP) (p = .01) responses to mental stress. The L allele was associated with larger SBP (p = .04), DBP (p < .0001), and heart rate (p = .04) responses to mental stress compared with the short (S) allele. Subjects with the SS genotype and high Father's Education exhibited smaller SBP (5.2 mm Hg) and DBP (2.9 mm Hg) responses than subjects with LL genotype and low Father's Education (SBP = 13.3 mm Hg, p = .002; DBP = 9.7 mm Hg, p < .0001).

CONCLUSIONS

Both the 5HTTLPR long allele and low SES, particularly during childhood, are associated with increased CVR to mental stress, which could account, at least in part, for the increased cardiovascular disease risk associated with these characteristics. If confirmed in further research, these characteristics could be used to identify persons who might benefit from preventive interventions.

Interaction between beta2 adrenergic receptor polymorphisms determines the extent of isoproterenol-induced vasodilatation ex vivo

OBJECTIVES

Single nucleotide polymorphisms at nucleotides 46, 79 and 491 of the beta2 adrenergic receptor (beta2AR) gene modify its pharmacological properties and may alter the response to agonists. The purpose of this study was to evaluate the role played by beta2AR polymorphisms on isoproterenol-induced relaxation of internal mammary arteries ex vivo.

METHODS

Internal mammary leftover segments were collected from 96 patients undergoing coronary artery bypass operation. Vascular rings were allowed to reach equilibrium with physiological Krebs solution before precontraction with U46619. Using the organ bath technique, cumulative dose-response curve of isoproterenol was constructed and average EC50 calculated. beta2AR genotyping was performed using a PCR-RFLP analysis.

RESULTS

Arterial segments obtained from Gly16 homozygotes displayed reduced sensitivity to isoproterenol compared with carriers of Arg16 allele(s) [Mean (-log) EC50+/-SD, 6.42+/-0.24, 95% confidence interval (CI) 6.32-6.53 vs. 6.67+/-0.25, 95% CI 6.62-6.73, P<0.001]. Among Gly16 homozygotes, the presence of two Glu27 alleles restored vascular response to the level noted among Arg16 carriers (6.58+/-0.17, 95% CI 6.41-6.76). The least response to isoproterenol was noted in a single patient carrying the Gly16Gly-Gln27Glu-Thr164Ile combined genotype requiring almost six-fold higher isoproterenol concentration than carriers of the wild-type genotype to achieve half the maximal arterial dilatation (17.78 x 10(-7) vs. 3.01 x 10(-7) +/- 2.62 x 10(-7) mol/l).

CONCLUSIONS

Vascular dilatation by isoproterenol is determined by a complex interaction between polymorphisms at nucleotides 46, 79 and 491 of the beta2AR gene. Further studies are warranted to evaluate the effect of additional polymorphisms in the coding and noncoding regions on vascular reactivity.

A review of the genetics of essential hypertension

PURPOSE OF REVIEW

Essential hypertension affects more than 20% of the adult population, and has a multifactorial origin arising from an interaction between susceptibility genes and environmental factors. Several strategies have been used to identify hypertension susceptibility genes. This review highlights recent efforts in genetic dissection of essential hypertension.

RECENT FINDINGS

Recently, further chromosomal regions harboring blood pressure loci have emerged in genome-wide linkage studies. Findings from a new systematic two-dimensional genome scan are presented, as well as sex-specific loci linked to hypertension in inbred rodent models. Many case-control association studies have been carried out, but results so far have been equivocal. This review discusses some interesting studies combining linkage and association strategies using gene-gene interactions, and studies the use of haplotypes instead of SNPs. Two novel hypertension susceptibility genes are presented, and a short summary on new insights into genes of the renin-angiotensin and adrenergic systems is given.

SUMMARY

To date, linkage and association studies have not been convincing. Genome-wide association studies may prove to be an effective approach to the problems posed by complex traits. Combined with candidate gene approaches, it is hoped this strategy will yield convincing evidence for genes associated with essential hypertension.

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.

Adrenergic Receptor Genotype but Not Perioperative Bisoprolol Therapy May Determine Cardiovascular Outcome in At-risk Patients Undergoing Surgery with Spinal Block

Background:

Neuraxial blockade is used as primary anesthetic technique in one third of surgical procedures. The authors tested whether bisoprolol would protect patients at risk for cardiovascular complications undergoing surgery with spinal block.

Methods:

The authors performed a double-blinded, placebo-controlled, multicenter trial to compare the effect of bisoprolol with that of placebo on 1-yr composite outcome including cardiovascular mortality, nonfatal myocardial infarction, unstable angina, congestive heart failure, and cerebrovascular insult. Bisoprolol was given orally before and after surgery for a maximum of 10 days. Adrenergic receptor polymorphisms and safety outcome measures of bisoprolol therapy were also determined.

Results:

A total of 224 patients were enrolled. Spinal block could not be established in 5 patients. One hundred ten patients were assigned to the bisoprolol group, and 109 patients were assigned to the placebo group. The mean duration of treatment was 4.9 days in the bisoprolol group and 5.1 days in the placebo group. Bisoprolol therapy reduced mean heart rate by 10 beats/min. The primary outcome was identical between treatment groups and occurred in 25 patients (22.7%) in the bisoprolol group and 24 patients (22.0%) in the placebo group during the 1-yr follow-up (hazard ratio, 0.97; 95% confidence interval, 0.55–1.69; P = 0.90). However, carriers of at least one Gly allele of the β1-adrenergic receptor polymorphism Arg389Gly showed a higher number of adverse events than Arg homozygous (32.4% vs. 18.7%; hazard ratio, 1.87; 95% confidence interval, 1.04–3.35; P = 0.04).

Conclusions:

Perioperative bisoprolol therapy did not affect cardiovascular outcome in these elderly at-risk patients undergoing surgery with spinal block.

beta2- and beta3-Adrenoceptor polymorphisms relate to subsequent weight gain and blood pressure elevation in obese normotensive individuals

High blood pressure (BP) is a major determinant of cardiovascular events in obesity. The beta2- and beta3-adrenoceptor polymorphisms are associated with obesity and hypertension. In the present study, we examine the relationships of beta2- and beta3-adrenoceptor polymorphisms with further weight gain-induced BP elevation in obese subjects. Changes in BP, body weight, total body fat-mass, waist-to-hip ratio, plasma norepinephrine (NE) and leptin levels, and beta2(Arg16Gly)- and beta3(Trp64Arg)-adrenoceptor polymorphisms were measured periodically over a 5-year period in 55 entry obese (body mass index [BMI]> or =25.0 kg/m(2)) normotensive (BP<140/90 mmHg) men. BP elevation and weight gain were defined as > or =10% increases from entry levels over 5 years in mean BP or BMI. Obese subjects with weight gain, BP elevation or weight gain-induced BP elevation had higher frequencies of the Gly16 allele of Arg16GIy and Arg64 allele of Trp64Arg. Subjects carrying the Gly16 or Arg64 alleles had significantly greater total fat-mass and waist-to-hip ratio at entry and over a 5-year period compared to the subjects who did not carry these polymorphisms. Subjects carrying the Gly16 allele had similar levels of plasma NE, higher levels of plasma leptin and a lower slope of the regression lines between plasma leptin and NE levels. Those carrying the Arg64 allele had higher plasma NE levels at entry and over a 5-year period compared to the subjects without the Arg64 allele, but plasma leptin levels and slopes were similar. The findings demonstrate that the Arg64 allele of the beta3-adrenoceptor polymorphisms relates to weight gain-induced BP elevation accompanying high plasma NE (heightened sympathetic activity) in obese men. The Gly16 allele of the beta2-adrenoceptor polymorphisms links to weight gain-induced BP elevation associated with leptin resistance. beta2- and beta3-adrenoceptor polymorphisms could predict the future BP elevation and further weight gain-induced BP elevation in originally obese subjects.

Alpha- and beta-adrenergic receptor polymorphisms in hypertensive and normotensive offspring

BACKGROUND

The offspring of hypertensive families are characterized by higher arterial blood pressure values and a depressed autonomic control of heart rate. The present study aimed to verify whether these differences are associated with a different genotype distribution of functionally relevant polymorphisms of the alpha- and beta-adrenergic receptor (AR) genes.

METHODS

We selected 109 age- and sex-matched young normotensive subjects with (FH+, n = 56) and without (FH-, n = 53) a family history of hypertension who underwent evaluation of arterial pressure; 24-h electrocardiogram monitoring to assess time-domain parameters of autonomic heart rate control [i.e. mean RR interval (NN), SD of RR intervals (SDNN) and mean square root of the differences of consecutive RR intervals (rMSSD)]; spectral baroreflex sensitivity measurement; and echo-Doppler to assess diastolic function and left ventricular mass. They were also characterized for the following polymorphisms by means of polymerase chain reaction-restriction fragment polymorphism analysis: Arg492Cys in the alpha1a-AR; Del301-303 in the alpha2b-AR; Ser49Gly and Arg389Gly in the beta1-AR; and the 5' leader cistron Arg19Cys, Arg16Gly and Gln27Glu in the beta2-AR.

RESULTS

FH+ individuals showed a higher systolic pressure, a lower SDNN and a greater isovolumic relaxation time compared to normotensive offspring. No differences were found between the two groups when genotype distribution of the studied polymorphisms was considered. Subjects carrying alpha1a-AR Cys492 allelic variant showed lower values of NN, SDNN and rMSSD, independent of age, gender and body mass index.

CONCLUSIONS

The functionally relevant polymorphisms of alpha2b-, beta1- and beta2-AR genes are not associated with a family history of essential hypertension. The Arg492Cys polymorphism of the alpha1a-AR gene, although not associated with a family history of hypertension, was strongly related to autonomic control of heart rate.

beta2 adrenoceptor (ADRB2) pharmacogenetics and cardiovascular phenotypes during laryngoscopy and tracheal intubation

Pharmacogenetics is the study of genetic variations that cause a variable drug response characterized by alteration in drug metabolism or in pharmacodynamics. The polymorphisms in genes encoding receptors relevant to treatment cause variation in sensitivity to many drugs. beta2 Adrenoceptor genetic variation contributes to regulation of blood pressure and hemodynamic changes by mediating peripheral vasodilatation. Laryngoscopy and tracheal intubation associated with hemodynamic changes. Although there are four nonsynomic single-nucleotide polymorphisms (SNPs) of beta2 adrenoceptor gene, codon 16 (Arg16Gly) and codon 27 (Gln27Glu) SNPs are both common and functionally important. In this paper, the authors investigated the beta2 adrenoceptor Gly16 and Glu27 SNPs in response to drugs relevant to anesthesia and how these SNPs impacted upon the cardiovascular phenotypes. The authors measured arterial systolic and diastolic blood pressure, heart rate, and rate-pressure product before induction of anesthesia and 1 min following laryngoscopy and tracheal intubation. Genomic DNA was amplified and genotyped using allele-specific polymerase chain reaction (ASPCR) and restriction fragment length polymorphism (RFLP) assays, respectively. When the authors compared hemodynamic results according to genotypes, the patients with Gln homozygote allele at codon 27 exhibited significant increase of heart rate than patients with Glu allele after laryngoscope and tracheal intubation.

Pharmacogenetics of beta2-agonist drugs in asthma

Genetic variation in the structure of the beta2-adrenoceptor (ADRB2) is a potentially important source of variability in the response to beta2-agonist drugs. The relevant polymorphisms are common, with allele frequencies as high as 50% in some cases. "Nonsynonymous" variants result in amino acid substitutions in the receptor structure, of which substitution of Gly for Arg at position 16 and Glu for Gln at position 27 are the most clinically relevant. Other polymorphisms occur in the noncoding flanking regions of the gene and may be important in regulating ADRB2 expression, thus affecting individual drug responses. Linkage disequilibrium involving polymorphisms in both the coding and noncoding regions may explain the diversity of outcomes regarding functional in vitro studies. To date, analysis by haplotype, rather than genotype, has tended to confuse the issues. Functional in vitro studies provide the basis by which these polymorphisms are believed to be relevant in vivo. However, follow-up investigations have not substantiated the conventional wisdom that Gly-16 confers increased propensity to downregulation, whereas Glu-27 confers resistance. The in vivo picture is further complicated by the dynamic status of ADRB2s. Paradoxically, downregulation of receptors with exogenous beta2-agonist drugs may occur more readily in cells that are relatively resistant to downregulation with exposure to endogenous catecholamine. Numerous studies have highlighted that the Arg-16 variant is associated with an enhanced bronchodilator response in vivo, although the picture is not a consistent one. Outcomes during chronic treatment of asthma with beta2-agonists have been more consistent. In patients who are homozygous for Arg-16, reduced lung function and increased frequency of exacerbations occur during chronic treatment with short-acting beta2-agonists. With long-acting beta2-agonists, the overall clinical benefits may be worse for Arg-16 than for the Gly-16 genotype. Therefore, ADRB2 polymorphisms are an important consideration in assessing individual patients with difficult asthma that may be drug-induced for reasons of ADRB2 genotype. They are also relevant in the design of clinical trials involving beta2-agonist therapy.

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.

Reduced baroreflex sensitivity in acute alcohol withdrawal syndrome and in abstained alcoholics

Acute alcohol withdrawal is often associated with increased sympathetic activity, and a decreased baroreflex sensitivity (BRS) can be assumed. Parameters of heart rate variability (HRV), blood pressure variability (BPV), BRS as well as cardiac index (CI), left ventricular work index (LVWI) and total peripheral resistance (TPR) were investigated in 20 patients undergoing acute alcohol withdrawal and matched controls. Measures were obtained during the peak of withdrawal symptomatology prior to treatment as well as 2 and 24h under continuous clomethiazole treatment. Alcohol withdrawal scores were obtained and correlated with autonomic measures. In addition, parameters were assessed in 15 subjects who abstained from alcohol after long-term intake. We found a severe down-regulation of BRS during acute alcohol withdrawal and to a milder extent in abstained alcoholics. Furthermore, HRV and BPV did not unequivocally reveal signs of elevated sympathetic activity. Non-linear parameters of HRV and parameters of BRS correlated with the severity of AWS. The distinct decrease of BRS in AWS and in long-term abstained subjects described here is of importance since similar alterations have been identified as independent prognostic factors for cardiac mortality in other diseases.

Three major haplotypes of the beta2 adrenergic receptor define psychological profile, blood pressure, and the risk for development of a common musculoskeletal pain disorder

Adrenergic receptor beta(2) (ADRB2) is a primary target for epinephrine. It plays a critical role in mediating physiological and psychological responses to environmental stressors. Thus, functional genetic variants of ADRB2 will be associated with a complex array of psychological and physiological phenotypes. These genetic variants should also interact with environmental factors such as physical or emotional stress to produce a phenotype vulnerable to pathological states. In this study, we determined whether common genetic variants of ADRB2 contribute to the development of a common chronic pain condition that is associated with increased levels of psychological distress and low blood pressure, factors which are strongly influenced by the adrenergic system. We genotyped 202 female subjects and examined the relationships between three major ADRB2 haplotypes and psychological factors, resting blood pressure, and the risk of developing a chronic musculoskeletal pain condition-Temporomandibular Joint Disorder (TMD). We propose that the first haplotype codes for lower levels of ADRB2 expression, the second haplotype codes for higher ADRB2 expression, and the third haplotype codes for higher receptor expression and rapid agonist-induced internalization. Individuals who carried one haplotype coding for high and one coding for low ADRB2 expression displayed the highest positive psychological traits, had higher levels of resting arterial pressure, and were about 10 times less likely to develop TMD. Thus, our data suggest that either positive or negative imbalances in ADRB2 function increase the vulnerability to chronic pain conditions such as TMD through different etiological pathways that imply the need for tailored treatment options.

Dietary sodium restriction and beta2-adrenergic receptor polymorphism modulate cardiovascular function in humans

Dietary Na+ intake influences beta2-adrenergic receptor (beta2AR) responsiveness. While receiving a normal Na+ diet (150 mmol day(-1)), subjects homozygous for glycine at amino acid 16 (Gly16) have greater forearm beta2AR-mediated vasodilatation than subjects homozygous for arginine (Arg16), an effect that is mediated by endothelial NO. We tested the hypothesis that dietary Na+ restriction eliminates genotype differences in forearm and systemic beta2AR-mediated dilatation in these groups. We measured heart rate, mean arterial pressure and cardiac output (CO, acetylene breathing) responses to administration of intravenous terbutaline (TRB) before and after 5 days of low dietary Na+ intake (10 mmol day(-1)) in healthy Gly16 (n = 17; age, 31 +/- 7 year) and Arg16 homozygotes (n = 15; age, 29 +/- 8 year). After the low-Na+ diet, a catheter was placed in the brachial artery to measure forearm blood flow (FBF, plethysmography) responses to administration of isoprenaline (isoproterenol) before and after NO inhibition with NG-mono-methyl-L-arginine (L-NMMA). In the Gly16 group, the low-Na+ diet decreased baseline CO from 6.4 +/- 1.4 to 5.5 +/- 1.2 l min(-1) (P = 0.003, paired t test), tended to decrease stroke volume from 97.0 +/- 20.6 to 86.9 +/- 21.7 ml (P = 0.06) and increased peripheral resistance from 1106 +/- 246 to 1246 +/- 222 dynes s cm(-5) (P = 0.02); significant effects of the low-Na+ diet were not observed in Arg16 subjects. In a repeated measures ANOVA, the responses of all cardiovascular measures to systemic administration of TRB were not influenced by genotype or diet. Additionally, the FBF response to incremental doses of isoprenaline did not differ between genotype groups before or after administration of L-NMMA. We conclude that dietary Na+ restriction blunted the increased forearm NO-mediated beta2AR responsiveness in Gly16 homozygotes observed in a previous study after normal dietary Na+ intake, while baseline CO decreased and peripheral resistance increased in this group. This study provides evidence that dietary Na+ modulates effects of the Arg16Gly polymorphism on cardiovascular function.