Haplotype-based analysis of alpha 2A, 2B, and 2C adrenergic receptor genes captures information on common functional loci at each gene

Unraveling the relationships between alpha- and beta-adrenergic modulation and the risk of heart failure

Background

The effects of α and ß adrenergic receptor modulation on the risk of developing heart failure (HF) remains uncertain due to a lack of randomized controlled trials. This study aimed to estimate the effects of α and ß adrenergic receptors modulation on the risk of HF and to provide proof of principle for genetic target validation studies in HF.

Methods

Genetic variants within the cis regions encoding the adrenergic receptors α1A, α2B, ß1, and ß2 associated with blood pressure in a 757,601-participant genome-wide association study (GWAS) were selected as instruments to perform a drug target Mendelian randomization study. Effects of these variants on HF risk were derived from the HERMES GWAS (542,362 controls; 40,805 HF cases).

Results

Lower α1A or ß1 activity was associated with reduced HF risk: odds ratio (OR) 0.83 (95% CI 0.74-0.93, P = 0.001) and 0.95 (95% CI 0.93-0.97, P = 8 × 10-6). Conversely, lower α2B activity was associated with increased HF risk: OR 1.09 (95% CI 1.05-1.12, P = 3 × 10-7). No evidence of an effect of lower ß2 activity on HF risk was found: OR 0.99 (95% CI 0.92-1.07, P = 0.95). Complementary analyses showed that these effects were consistent with those on left ventricular dimensions and acted independently of any potential effect on coronary artery disease.

Conclusions

This study provides genetic evidence that α1A or ß1 receptor inhibition will likely decrease HF risk, while lower α2B activity may increase this risk. Genetic variant analysis can assist with drug development for HF prevention.

Signaling Pathways Associated with Chronic Wound Progression: A Systems Biology Approach

Previously we have shown that several oxidative stress-driven pathways in cutaneous chronic wounds are dysregulated in the first 48 h post-wounding. Here, we performed an RNASeq analysis of tissues collected up to day 20 after wounding, when we have determined full chronicity is established. Weighted Gene Correlation Network Analysis was performed in R segregating the genes into 14 modules. Genes in the modules significantly correlated (p < 0.05) to early and full chronicity were used for pathway analysis using pathfindR. In early chronicity, we observed enrichment of several pathways. Dysregulation of Ephrin/Eph signaling leads to growth cone collapse and impairs neuronal regeneration. Adra2b and Adra2a overexpression in early and full chronicity, respectively, decreased cAMP production and impaired re-epithelialization and granulation tissue formation. Several pathways involving a Smooth-muscle-actin (Acta1) were also enriched with Acta1 overexpression contributing to impaired angiogenesis. During full chronicity, the ‘JAK-STAT’ pathway was suppressed undermining host defenses against infection. Wnt signaling was also suppressed, impairing re-epithelialization and granulation tissue formation. Biomarkers of cancer such as overexpression of SDC1 and constitutive activation of ErbB2/HER2 were also identified. In conclusion, we show that during progression to full chronicity, numerous signaling pathways are dysregulated, including some related to carcinogenesis, suggesting that chronic wounds behave much like cancer. Experimental verification in vivo could identify candidates for treatment of chronic wounds.

Differential gene expression profiling of the goose pineal gland

1. The present study was conducted to obtain a better understanding of the molecular mechanisms underlying broodiness in a commercial breed, Tianfu geese, as little is known about the role of the pineal gland in this period. The aim was to identify genes which are differentially expressed in the pineal gland between the laying and broodiness periods by performing a transcriptome screen.2. After sequencing cDNA derived from the pineal gland and annotation of the results, a sequencing depth of 14.82 and 18.17 million mapped tags was obtained during the laying and broodiness periods, respectively, and a total of 120 differentially expressed genes were identified. Of these, 32 genes showing up-regulated expression and 88 genes showing down-regulated expression were identified in broodiness period vs. laying period libraries.3. Gene ontology (GO) analyses showed that these genes were related to the visual process, phototransduction, and lipoprotein metabolism. Kyoto Encyclopaedia of Genes and Genome (KEGG) analyses showed that phototransduction and tryptophan metabolism pathways exhibited the largest enrichment factors. The reliability of the RNA sequence data was confirmed by quantitative real-time PCR analysis of five genes, and the results were mostly consistent with those from the high-throughput RNA sequencing.4. The goose transcriptome and the identification of differentially expressed genes provided comprehensive gene expression information that enables a better understanding of the molecular mechanisms underlying the broodiness period of geese.

β2‑adrenergic receptor functionality and genotype in two different models of chronic inflammatory disease: Liver cirrhosis and osteoarthritis

The present study was designed to investigate the functional status of β2 adrenoceptors (β2AR) in two models of chronic inflammatory disease: liver cirrhosis (LC) and osteoarthritis (OA). The β2AR gene contains three single nucleotide polymorphisms at amino acid positions 16, 27 and 164. The aim of the present study was to investigate the potential influence of lymphocyte β2AR receptor functionality and genotype in LC and OA patients. Blood samples from cirrhotic patients (n=52, hepatic venous pressure gradient 13±4 mmHg, CHILD 7±2 and MELD 11±4 scores), OA patients (n=30, 84% Kellgren‑Lawrence severity 4 grade, 14% knee replacement joint) and healthy volunteers as control group (n=26) were analyzed. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood and basal and isoproterenol induced adenylate cyclase activity (isoproterenol stimulus from 10‑9 to 10‑4 mM), and β2AR allelic variants (rs1042713, rs1042714, rs1800888) were determined. β2AR functionality was decreased in the two different models of chronic inflammatory disease studied, OA (50% vs. control) and LC (85% vs. control). In these patients, the strength of the β2AR response to adrenergic stimulation was very limited. Adrenergic modulation of PBMC function through the β2AR stimulus is decreased in chronic inflammatory processes including LC and OA, suggesting that the adrenergic system may be important in the development of these processes.

Lack of Association Between Adrenoreceptor Genotype and the Vasoconstriction Response to Dexmedetomidine

An exaggerated vasoconstriction response to dexmedetomidine, an α-2 adrenergic agonist, has been associated with 2 genotypes: a deletion in the α-2B adrenoreceptor gene ( ADRA2B deletion) and SNP rs9922316 in the gene for protein kinase C type β ( PRKCB). We hypothesized that children with a marked systemic vascular resistance index (SVRI) increase following intravenous dexmedetomidine bolus would carry these genotypes. Following institutional review board approval, DNA samples from 16 children with transplanted hearts who participated in a study in the cardiac catheterization laboratory of hemodynamic responses to dexmedetomidine boluses underwent genotyping by polymerase chain reaction (PCR) amplification and PCR Sanger sequencing for the ADRA2B deletion and for PRKCB rs9922316. A wide range of SVRI (-12% to +76%, median 33%) and mean arterial blood pressure (MAP; -7% to +50%, median 26%) responses to dexmedetomidine was observed. The responses were not significantly different among genotype groups. An association between exaggerated SVRI or MAP responses and either ADRA2B deletion or PRKCB rs9922316 was not observed.

Noradrenergic modulation of emotional memory in aging

Interest in the role of the noradrenergic system in the modulation of emotional memories has recently increased. This study briefly reviews this timely line of research with a specific focus on aging. After having identified surprisingly few studies that investigated emotional memory in older adults from a neurobiological perspective, we found a significant interaction between noradrenergic activity and emotional memory enhancement in older adults. This pattern of data are explained both in terms of a top-down modulation of behavioral processes (e.g., changes in priority and individual goals) and in terms of greater activity of noradrenergic system during aging. Altogether, both behavioral and genetic variations studies (e.g., Alpha 2 B Adrenoceptor genotype) have shown that healthy older adults are able to circumvent or minimize the experience of negative emotions and stabilize or even enhance positive emotional experiences. Future studies are highly warranted to better clarify the relationship between noradrenaline and emotional memories in the aging brain.

Genetic, Epigenetic, and Environmental Factors Influencing Neurovisceral Integration of Cardiovascular Modulation: Focus on Multiple Sclerosis

Thought to be an autoimmune inflammatory CNS disease, multiple sclerosis (MS) involves multiple pathologies with heterogeneous clinical presentations. An impaired neurovisceral integration of cardiovascular modulation, indicated by sympathetic and parasympathetic autonomic nervous system (ANS) dysfunction, is among common MS clinical presentations. ANS dysfunction could not only enhance MS inflammatory and neurodegenerative processes, but can also lead to clinical symptoms such as depression, fatigue, sleep disorder, migraine, osteoporosis, and cerebral hemodynamic impairments. Therefore, factors influencing ANS functional activities, in one way or another, will have a significant impact on MS disease course. This review describes the genetic and epigenetic factors, and their interactions with a number of environmental factors contributing to the neurovisceral integration of cardiovascular modulation, with a focus on MS. Future studies should investigate the improvement in cardiovascular ANS function, as a strategy for preventing and minimizing MS-related morbidities, and improving patients' quality of life.

Interpatient variability in dexmedetomidine response: a survey of the literature

Fifty-five thousand patients are cared for in the intensive care unit (ICU) daily with sedation utilized to reduce anxiety and agitation while optimizing comfort. The Society of Critical Care Medicine (SCCM) released updated guidelines for management of pain, agitation, and delirium in the ICU and recommended nonbenzodiazepines, such as dexmedetomidine and propofol, as first line sedation agents. Dexmedetomidine, an alpha-2 agonist, offers many benefits yet its use is mired by the inability to consistently achieve sedation goals. Three hypotheses including patient traits/characteristics, pharmacokinetics in critically ill patients, and clinically relevant genetic polymorphisms that could affect dexmedetomidine response are presented. Studies in patient traits have yielded conflicting results regarding the role of race yet suggest that dexmedetomidine may produce more consistent results in less critically ill patients and with home antidepressant use. Pharmacokinetics of critically ill patients are reported as similar to healthy individuals yet wide, unexplained interpatient variability in dexmedetomidine serum levels exist. Genetic polymorphisms in both metabolism and receptor response have been evaluated in few studies, and the results remain inconclusive. To fully understand the role of dexmedetomidine, it is vital to further evaluate what prompts such marked interpatient variability in critically ill patients.

Genetic association of adrenergic receptor alpha 2A with obesity and type 2 diabetes

OBJECTIVE

The sympathetic nervous system (SNS) is linked to glucose, lipid, and protein metabolism. The α2A -adrenergic receptor (ADRA2A) is involved in the SNS and mediates inhibition of insulin secretion and lipolysis. The association of ADRA2A single-nucleotide polymorphisms (SNPs) with obesity and/or type 2 diabetes (T2D) was investigated.

DESIGN AND METHODS

Genotyping was performed in a case-control study of 1,177 Swedish individuals, including lean and obese subjects with normal glucose tolerance (NGT) and T2D patients. ADRA2A mRNA expression was measured in pancreatic islets isolated from T2D patients and nondiabetic subjects.

RESULTS

SNP rs553668 was associated with T2D in men (odds ratio [OR] = 1.47; 95% confidence interval [CI] = 1.08-2.01; P = 0.015) but this association was lost after adjusting for age and for body mass index (BMI). Associations were also detected when comparing obese NGT and lean NGT subjects (OR = 1.49; 95% CI = 1.07-2.07; P = 0.017), and in obese (OR = 1.62; 95% CI = 1.06-2.49; P = 0.026), but not in lean T2D. In women, multiple logistic regression regarding SNP rs521674 demonstrated an increased OR of 7.61 (95% CI = 1.70-34.17; P = 0.008) for T2D when including age as a covariant. Correcting for BMI removed the significant association. When age was included in the model, association also found when obese T2D patients were compared with lean NGT subjects (P = 0.041). ADRA2A mRNA expression in human pancreatic islets was detectable, but with no statistically significant difference between the diabetic and the control groups.

CONCLUSIONS

ADRA2A genetic polymorphisms are mainly associated with obesity and possibly with T2D in a Swedish population.

Norepinephrine genes predict response time variability and methylphenidate-induced changes in neuropsychological function in attention deficit hyperactivity disorder

Noradrenergic dysfunction may be associated with cognitive impairments in attention-deficit/hyperactivity disorder (ADHD), including increased response time variability, which has been proposed as a leading endophenotype for ADHD. The aim of this study was to examine the relationship between polymorphisms in the α-2A-adrenergic receptor (ADRA2A) and norepinephrine transporter (SLC6A2) genes and attentional performance in ADHD children before and after pharmacological treatment.One hundred one medication-naive ADHD children were included. All subjects were administered methylphenidate (MPH)-OROS for 12 weeks. The subjects underwent a computerized comprehensive attention test to measure the response time variability at baseline before MPH treatment and after 12 weeks. Additive regression analyses controlling for ADHD symptom severity, age, sex, IQ, and final dose of MPH examined the association between response time variability on the comprehensive attention test measures and allelic variations in single-nucleotide polymorphisms of the ADRA2A and SLC6A2 before and after MPH treatment.Increasing possession of an A allele at the G1287A polymorphism of SLC6A2 was significantly related to heightened response time variability at baseline in the sustained (P = 2.0 × 10) and auditory selective attention (P = 1.0 × 10) tasks. Response time variability at baseline increased additively with possession of the T allele at the DraI polymorphism of the ADRA2A gene in the auditory selective attention task (P = 2.0 × 10). After medication, increasing possession of a G allele at the MspI polymorphism of the ADRA2A gene was associated with increased MPH-related change in response time variability in the flanker task (P = 1.0 × 10).Our study suggested an association between norepinephrine gene variants and response time variability measured at baseline and after MPH treatment in children with ADHD. Our results add to a growing body of evidence, suggesting that response time variability is a viable endophenotype for ADHD and suggesting its utility as a surrogate end point for measuring stimulant response in pharmacogenetic studies.

Haplotype polymorphism in the alpha-2B-adrenergic receptor gene influences response inhibition in a large Chinese sample

Response inhibition refers to the suppression of inappropriate or irrelevant responses. It has a central role in executive functions, and has been linked to a wide spectrum of prevalent neuropsychiatric disorders. Increasing evidence from neuropharmacological studies has suggested that gene variants in the norepinephrine neurotransmission system make specific contributions to response inhibition. This study genotyped five tag single-nucleotide polymorphisms covering the whole alpha-2B-adrenergic receptor (ADRA2B) gene and investigated their associations with response inhibition in a relatively large healthy Chinese sample (N=421). The results revealed significant genetic effects of the ADRA2B conserved haplotype polymorphisms on response inhibition as measured by stop-signal reaction time (SSRT) (F(2, 418)=5.938, p=0.003). Individuals with the AAGG/AAGG genotype (n=89; mean SSRT=170.2 ms) had significantly shorter SSRTs than did those with either the CCAC/AAGG genotype (n=216; mean SSRT=182.4 ms; uncorrected p=0.03; corrected p=0.09) or the CCAC/CCAC genotype (n=116; mean SSRT=195.8 ms; corrected p<0.002, Cohen's d=0.51). This finding provides the first evidence from association research in support of a critical role of the norepinephrine neurotransmission system in response inhibition. A better understanding of the genetic basis of response inhibition would allow us to develop more effective diagnosis, treatment, and prevention of deficient or underdeveloped response inhibition as well as its related prevalent neuropsychiatric disorders.

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

Cardiovascular reactivity to stress and α-adrenergic receptor (α-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between α(1A) -AR (Arg492Cys), α(2A) -AR (-1291C/G), and α(2B) -AR (Ins/Del301-303) gene variants and cardiovascular reactivity in 500 normotensive Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure were measured during cold and psychological stress. The Arg492Cys polymorphism in the α(1A) -AR gene was associated with heart rate reactivity to stress, but the association depended on sex. The -1291C/G promoter polymorphism in the α(2A) -AR gene was associated with vascular reactivity to stress; vasoconstriction increased as a linear function of the number of copies of the variant G allele. Thus, specific associations emerged between genetic variations in α-Ars and cardiovascular reactivity in young Blacks.

Genetic variations in the α(2A)-adrenoreceptor are associated with blood pressure response to the agonist dexmedetomidine

BACKGROUND

α(2A)-Adrenoceptors (α(2A)-ARs) have important roles in sympathetic cardiovascular regulation. Variants of ADRA2A affect gene transcription and expression and are associated with insulin release and risk for type 2 diabetes. We examined whether ADRA2A variants are also associated with cardiovascular responses to the selective α(2)-AR-agonist dexmedetomidine.

METHODS AND RESULTS

Seventy-three healthy subjects participated in a placebo-controlled, single-blind study. After 3 infusions of placebo, subjects received 3 incremental infusions of dexmedetomidine (cumulative dose, 0.4 μg/kg). Primary outcomes were changes in systolic blood pressure (SBP) and plasma norepinephrine concentrations, measured as difference of the area-under-the-curve during placebo and dexmedetomidine infusions (ΔAUC). We used multiple linear regression analysis to examine the associations between 9 ADRA2A tagging variants and 5 inferred haplotypes and ΔAUC after adjustment for covariates. Homozygous carriers of rs553668 and the corresponding haplotype 4, previously associated with increased α(2A)-AR expression, had a 2.2-fold greater decrease in AUC(SBP) after dexmedetomidine (adjusted P=0.006); similarly, the maximum decrease in SBP was 24.7±8.1 mm Hg compared with 13.6±5.9 mm Hg in carriers of the wild-type allele (P=0.007). Carriers of haplotype 3, previously associated with reduced α(2A)-AR expression, had a 44% smaller decrease in AUC(SBP) (P=0.013). Haplotype information significantly improved the model predicting the decrease in SBP (P<0.001). There were similar but nonsignificant trends for diastolic blood pressure and heart rate. Genotypes were not significantly associated with norepinephrine responses.

CONCLUSIONS

Common ADRA2A variants are associated with the hypotensive response to dexmedetomidine. Effects of specific variants/haplotypes in vivo are compatible with their known effects on gene expression in vitro.

The role of the ADRA2A C1291G genetic polymorphism in response to dexmedetomidine on patients undergoing coronary artery surgery

The existence of interindividual drug response variability has been known for a long time. Individual susceptibility which might cause toxicity or inadequate treatment is important in drug therapy. Genetic polymorphisms in genes responsible for drug response are expected to be useful in keeping track of differences among individuals. Dexmedetomidine is a sedative drug, whose use in intensive care unit patients was confirmed by USA-Food Drug Administration (FDA) by the end of 1999. It was proven that dexmedetomidine shows its clinic effect via the α(2)-AR. However, to the best of our knowledge, to date, there is no investigation in clinic indicating the relation between dexmedetomidine and α(2A)-AR gene polymorphism. The aim of our study was to investigate the association between the effect of α(2A)-Adrenergic Receptor (ADRA2A) C-1291G gene polymorphism in the promoter region of the candidate gene and clinical effects (sedative and haemodynamics effects) of dexmedetomidine. One hundred and ten patients undergoing coronary artery surgery were prospectively studied. Anesthetic technique was standardized with fentanyl, midazolam and rocuronium bromide. Patients were monitorized with Bispectral Index (BIS) monitor in addition to the routine invasive haemodynamic monitorization in the operation room. The Ramsay Sedation Scale was also used in order to determine the sedation level just arriving to Intensive Care Unit (ICU). The genotyping of ADRA2A C1291G was done by Restriction Fragment Length Polymorphism-Polymerase Chain Reaction (RFLP-PCR). We found the frequencies of C1291C, C1291G and G1291G genotypes, as 43.6, 45.5 and 10.9%, respectively. Patients who carry variant genotype had higher BIS and Ramsay Sedation Scores, indicating a longer period for falling asleep. The results of our study are promising, considering the association between ADRA2A polymorphism and response to dexmedetomidine. However, further investigations on other ADRA2A locus or haplotypes might be useful to clarify the relation between this gene and dexmedetomidine activity.

Regional differences in cerebral perfusion associated with the alpha-2A-adrenergic receptor genotypes in attention deficit hyperactivity disorder

BACKGROUND

Neurobiologic studies have suggested that dysregulation of central noradrenergic systems may be involved in the pathophysiology of attention deficit hyperactivity disorder (ADHD), and it has been hypothesized that genetic changes in the norepinephrine pathways might contribute to dysfunction of the prefrontal cortex circuits in ADHD. We previously reported decreased cerebral blood flow in the right lateral prefrontal cortex and both orbitofrontal cortices in children with ADHD. Genetic investigations have shown that the alpha-2A-adrenergic receptor gene (ADRA2A) is associated with ADHD. Our aim was to examine whether the presence of a risk allele of the ADRA2A MspI polymorphism is associated with differences in regional cerebral blood flow in boys with ADHD.

METHODS

We recruited 21 Korean boys with ADHD (mean age 9.9, standard deviation [SD] 2.7 yr) and 11 age- and sex-matched controls (mean age 10.6 [SD 2.1] yr). Each participant underwent technetium-99m-hexamethylpropylene amine oxime ((99m)Tc-HMPAO) single-photon emission computed tomography. We performed image analyses with voxe-wise t statistics using SPM2.

RESULTS

We found regional hypoperfusion in the prefrontal regions, including the right orbitofrontal and right medial gyri, and the bilateral putamen and cerebellum in boys with ADHD relative to controls (p < 0.0005, uncorrected for multiple comparisons). Boys with ADHD who carried the C allele (n = 13) at the ADRA2A MspI polymorphism had reduced perfusion in the bilateral orbitofrontal regions compared with those without the C allele (n = 8) (p < 0.0005, uncorrected for multiple comparisons).

LIMITATIONS

This study was limited by the small sample size, and we did not obtain genetic data from the controls.

CONCLUSION

Our findings suggest that regional differences in cerebral perfusion in the orbitofrontal cortex represent an intermediate neuroimaging phenotype associated with the ADRA2A MspI polymorphism; these data support the validity of the noradrenergic hypothesis regarding the pathophysiology of ADHD.

Association of alpha 2A adrenergic receptor gene (ADRAlpha2A) polymorphism with irritable bowel syndrome, microscopic and ulcerative colitis

BACKGROUND

Alpha 2 adrenergic receptors (alpha2 ARs) play a central role in the regulation of systemic sympathetic activity. Prejunctional alpha 2A adrenoceptor regulates through negative feedback at presynaptic nerve ending. A-1291 C>G polymorphism located in alpha2-adrenergic receptor gene (ADRAlpha2A) has been identified. We investigated the possible association between 1291 C>G polymorphism in the promoter region of ADRAlpha2A in clinical subtypes of IBS, ulcerative and microscopic colitis patients.

METHODS

This prospective case control study included 92 patients with diarrhea predominant IBS (D-IBS), 44 with constipation predominant IBS (C-IBS), 15 with alternating diarrhea and constipation IBS (M-IBS), 75 ulcerative colitis (UC), 41 microscopic colitis (MC) and 100 healthy controls. The subjects were genotyped by using PCR amplification of the promoter region of ADRAlpha2A gene followed by digestion with the restriction enzyme MspI. The study was approved by the institute ethical committee.

RESULTS

A strong genotypic association was observed between alpha2A-1291 C>G polymorphism and D-IBS (chi2=6.38, df=2, p<0.05). There was no significant difference in alpha2A-1291 C>G genotype and allele frequency between C-IBS, M-IBS, UC, MC cases and control subjects.

CONCLUSIONS

A significant association was observed between alpha2A-1291C>G polymorphism and D-IBS. Thus, alpha2 AR gene may be a potential candidate involved in the pathophysiology of D-IBS.

Association of the α2A adrenergic receptor -1291C/G polymorphism and antipsychotic-induced weight gain in European–Americans

Aims: To investigate the -1291 C/G promoter polymorphism (rs1800544) of the adrenergic α-2A receptor (ADRA2A) with clozapine-/olanzapine-induced weight gain in European–Americans and African–Americans. The α-adrenergic receptors inhibit lipolysis in the adipose tissue and are involved in weight gain regulation. Moreover, two previous studies indicated an association with antipsychotic-induced weight gain with the same polymorphism in Asian populations. Materials & methods: We analyzed a relatively large (n = 129) and well-characterized group of patients and monitored them for a period of 6–14 weeks. Our refined sample consisted of 60 European–Americans and 39 African–Americans on clozapine or olanzapine, prospectively. Results: In European–Americans, we observed a significant difference in weight gain across the genotypic categories (p = 0.046). The carriers of the C allele gained more weight compared with the subjects homozygous for the GG allele (CC + CG vs GG; 3.73 ± 4.13 kg vs 0.23 ± 2.92 kg; p = 0.013). We did not find a significant association in African–Americans, although the sample size was probably too small. Conclusion: Our observations suggest a possible role of ADRA2A polymorphisms in clozapine-/olanzpaine-induced weight gain in subjects of European descent.

Association analysis between the C-1291G polymorphism in the promoter region of the adrenergic alpha2A receptor gene and polydipsia in schizophrenia

Several lines of studies have shown the existence of an important inhibitory mechanism for the control of water intake involving adrenergic alpha2A receptors (ADRA2A). A human study using patients with schizophrenia demonstrated an exacerbation of polydipsia by the administration of clonidine, an ADRA2A-agonist, and a relief of polydipsia by mianserin, an ADRA2A-antagonist, suggesting the involvement of the central adrenergic system in the drinking behavior of patients with schizophrenia. Based on these findings we examined a possible association between the C-1291G polymorphism in the promoter region of the ADRA2A gene and polydipsia in schizophrenia using a Japanese case-control sample. Our sample includes 348 patients with schizophrenia (DSM-IV) (84 with polydipsia and 264 without polydipsia). No significant association between the ADRA2A C-1291G polymorphism and polydipsia was found. Our result suggests that the ADRA2A C-1291G polymorphism may not confer susceptibility to polydipsia in schizophrenia in our sample. Further studies with larger samples are warranted.

Association between homozygosity of a G allele of the alpha-2a-adrenergic receptor gene and methylphenidate response in Korean children and adolescents with attention-deficit/hyperactivity disorder

BACKGROUND

Methylphenidate (MPH) blocks the norepinephrine transporter as well as the dopamine transporter. The alpha-2a-adrenergic receptor is a key component of the noradrenergic system. The aim of this study was to evaluate the association between the ADRA2A -1291 C>G polymorphism and the response to MPH treatment in Korean subjects with attention-deficit/hyperactivity disorder (ADHD).

METHODS

This study enrolled 114 ADHD children (mean age = 9.08 +/- 1.94 years) from a child psychiatric clinic in South Korea. Subjects who had an improvement of >/= 50% compared with the baseline ADHD rating scale (ARS) score or who had a Clinical Global Impression-improvement score of 1 or 2 points after treatment were defined as the "good response". We examined the relationship of the ADRA2A to MPH response.

RESULTS

We found that a good response to MPH treatment, measured by the ARS as assessed by the parents, was observed for 76.9% of the subjects carrying the G/G genotype but for only 46.0% and 41.7% of those with the C/G and C/C genotypes, respectively [chi(2)(2) = 11.929, p = .003]. We also found a significant difference in the change in total ARS scores between subjects with and without the G/G genotype [t(1) = 2.21, p = .029].

CONCLUSIONS

Our findings provide evidence of an association between the ADRA2A -1291 C>G genotype and response to MPH treatment in Korean subjects with ADHD. Nonetheless, the methodological limitation of not being a randomized placebo-controlled trial and primarily basing results on parent report to clinicians suggest that these results should be viewed as more preliminary.

Genetic variants in the alpha2C-adrenoceptor and G-protein contribute to ethnic differences in cardiovascular stress responses

OBJECTIVES

Cardiovascular responses to stressors are regulated by sympathetic activity, increased in black Americans, and associated with future cardiovascular morbidity. Our aim was to determine whether two functional variants in genes regulating sympathetic activity, a deletion in the alpha2C-adrenergic receptor (ADRA2C del322-325) and a G-protein beta3-subunit variant (GNB3 G825T), affect cardiovascular responses to physiologic stressors and contribute to their ethnic differences.

METHODS

We measured heart rate and blood pressure responses to a cold pressor test (CPT) in 79 healthy participants (40 blacks, 39 whites), aged 25.7+/-5.3 years, and determined genotypes for the ADRA2C and GNB3 variants. We examined the response variables (increase in heart rate and blood pressure) in multiple linear regression analyses adjusting first for baseline measures, ethnicity, and other covariates, and then additionally for genotypes.

RESULTS

Black participants had a greater heart rate response to CPT than whites [mean difference, 9.9 bpm; 95% confidence interval (CI), 4.1 to 15.6; P=0.001]. Both the ADRA2C del/del (15.8 bpm; 95% CI, 8.0-23.7; P<0.001) and GNB3 T/T genotypes (6.8 bpm; 95% CI, 0.9-12.7; P=0.026) were associated with greater heart rate response. After adjusting for genotypes, the ethnic difference was abrogated (1.3 bpm; 95% CI, -5.4-8.0; P=0.70), suggesting that the genetic variants contributed substantially to ethnic differences.

CONCLUSION

Variation in genes that regulate sympathetic activity affects hemodynamic stress responses and contributes to their ethnic differences. This study elucidates how genetic factors may in part explain ethnic differences in cardiovascular regulation.

Association of alpha2A-adrenergic receptor gene polymorphism with susceptibility to suicide in Japanese females

OBJECTIVES

It has been suggested that noradrenergic system abnormalities are involved in suicide. Postmortem brain studies have shown that molecular and functional alterations in alpha2A-adrenergic receptor-induced signal transduction are associated with suicide and depression. Recently, a single nucleotide polymorphism (SNP) within a coding region of the alpha2A-adrenergic receptor gene (ADRA2A), which results in an Asn-to-Lys change at amino acid 251 (N251K), has been implicated in susceptibility to suicide in Caucasians. The aim of our study is to determine whether genetic variants of the ADRA2A gene are also associated with suicide in a Japanese population.

METHODS

Three SNPs, C-1291G, N251K and rs3750625C/A, and one insertion/deletion polymorphism in the ADRA2A gene were genotyped in 184 completed suicides and 221 control subjects with the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Neither variation of the N251K SNP nor the insertion/deletion polymorphism was found in our Japanese samples. The C-1291G SNP in the promoter region was found to be significantly associated with suicide in females (P=0.043 and 0.013 for genotypic and allelic comparisons, respectively). One of the common haplotypes, CC of C-1291G and rs3750625C/A, was also associated with suicide in females (P=0.015). These associations were also significant in the female violent suicide victims (P=0.009 and 0.009 for allelic and CC haplotypic comparisons, respectively). Although the significance was nominal, it was maintained even after correction for multiple comparisons. By contrast, neither of these two SNPs showed any association with violent and/or non-violent suicide in males.

CONCLUSION

Our results raise the possibility that promoter genetic variation in the ADRA2A gene is associated with either suicide or violent suicide in females.

Associations between an alpha 2A adrenergic receptor gene polymorphism and adolescent personality

The aim of this study was to investigate the impact of the C-1291G polymorphism in the promoter region of the alpha 2A adrenoreceptor gene (ADRA2A) to the personality traits. In the present study, data of the younger cohort of the Estonian Children Personality Behaviour and Health Study was used (N = 419). Personality traits were assessed by 240-item (Estonian Personality Item Pool NEO (EPIP-NEO)). Restriction enzyme MspI was used after PCR amplification to genotype the subjects according to C-1291G polymorphism of the ADRA2A. There were no significant differences on the level of the Big Five personality domains between genotypes; however, there were three significant differences on the level of different subscales. The subjects with GG genotype had significantly higher scores on Depression and significantly lower scores on Morality and Orderliness compared to subjects with CC and CG genotypes. There was a significant interaction between sex and ADRA2A polymorphism regarding E1, Friendliness; E2, Gregariousness; and E6, Cheerfulness. With CC and CG genotypes girls had higher scores on extraversion scales than boys, but with GG genotype boys score higher than girls with GG genotype. It is concluded that the gene polymorphism in the ADRA2A has an influence on personality traits in adolescents.

Adrenergic alpha2A receptor gene and response to methylphenidate in attention-deficit/hyperactivity disorder-predominantly inattentive type

An association between ADRA2A -1291 C > G polymorphism and response to methylphenidate in inattentive symptoms was previously suggested in children with ADHD. No investigation specifically assessed this association in ADHD-inattentive type (ADHD-I). In this naturalistic pharmacogenetic study, 59 subjects with ADHD-I from a non-referred sample were treated with short-acting methylphenidate and genotyped for ADRA2A -1291 C > G polymorphism. The primary outcome measure was the inattentive subscale of the SNAP-IV applied by a child psychiatrist blinded to genotype at baseline and first month of treatment. Children and adolescents with the G allele showed significantly lower inattentive scores with MPH treatment at the first month of treatment than subjects without the G allele (n = 59; F = 6.14; p = 0.016). We extended to ADHD-I previous findings suggesting the influence of the G allele at the ADRA2A -1291 C > G polymorphism on the improvement of inattentive symptoms with methylphenidate in children with all ADHD subtypes.

Effect of the alpha2C-adrenoreceptor deletion322-325 variant on sympathetic activity and cardiovascular measures in healthy subjects

BACKGROUND

The alpha2C-adrenergic receptor plays an important role in the regulation of the sympathetic nervous system and, therefore, blood pressure and heart rate. A deletion polymorphism in its gene (ADRA2C del322-325), ten times more common in black than white Americans, has been associated with a loss of function in vitro and, under controlled study conditions, raised blood pressure and catecholamine secretion. We therefore examined the hypothesis that the ADRA2C deletion variant would alter sympathetic activity and contribute to ethnic differences in blood pressure.

METHODS

We measured resting plasma norepinephrine and epinephrine concentrations, blood pressure and heart rate in 224 healthy subjects (127 whites), and determined their ADRA2C del322-325 genotype. Additionally, we analyzed heart rate variability (HRV) in a subgroup of 50 black subjects.

RESULTS

Systolic (SBP) and diastolic blood pressure (DBP) were higher in blacks than whites [difference (95% confidence interval), 4.4 (1.5-7.4) mmHg, P = 0.003; and 2.7 (0.7-4.6) mmHg, P = 0.01, respectively]. Norepinephrine concentrations did not differ among subjects with 0, 1 and 2 copies of the deletion variant [median (interquartile range), 185.0 (147.5-269.8), 200.0 (154.9-257.0) and 173.8 (158.5-235.8) pg/ml, respectively; P = 0.54]. Similarly, none of the HRV parameters differed among the genotype groups. In multiple linear regression analyses adjusting for multiple covariates, the deletion genotype was not associated with SBP or DBP. In contrast, black ethnicity was associated with higher SBP (P = 0.001) and DBP (P = 0.005).

CONCLUSION

The ADRA2C deletion polymorphism had no effect on markers of resting sympathetic activity and cardiovascular measures, and did not account for ethnic differences in blood pressure.

Association analyses of adrenergic receptor polymorphisms with obesity and metabolic alterations

Genes involved in the regulation of catecholamine function may be important in obesity because of the role catecholamines play in energy expenditure and lipolysis. To determine if common single nucleotide polymorphisms (SNPs) in beta(1)-adrenergic receptor (ADRB1), beta(2)-adrenergic receptor (ADRB2), beta(3)-adrenergic receptor (ADRB3), and alpha(2)-adrenergic receptor (ADRA2A) genes associate with obesity and metabolic alterations, we recruited 74 healthy African American and 161 white men and women (age, 18-49 years) to participate in this case-control genetic association study. Genotypes were determined by polymerase chain reaction and restriction fragment length polymorphism. Associations between genotype and body mass index (BMI), percentage of body fat (by measuring skinfold thickness in 7 different sites), fasting (12-hour) plasma glucose, insulin, potassium concentrations, glycated hemoglobin, and insulin resistance (homeostasis model assessment [HOMA(IR)] score) were performed. Among whites, the ADRB1 Arg389-->Gly variant associated with insulin concentrations and HOMA(IR): mean +/- SD values for insulin and HOMA(IR) in Arg389 homozygotes and carriers of the Gly were 10 +/- 7.0 and 12 +/- 9.4 micro IU/mL (P = .02) and 2.1 +/- 1.7 and 2.6 +/- 2.2 (P = .057), respectively. Systolic blood pressure was higher in whites for carriers of the ADBR1 Ser49 compared to Gly49 homozygotes (124 +/- 12.6 vs 119 +/- 11.3 mm Hg, respectively; P = .02). Subsequent analysis revealed that these associations were attributable to a higher BMI among obese participants. The ADRA2A G1780A SNP associated with BMI and percentage of body fat in African Americans (P = .05). Interactions were detected between ADRA2A C-1291G and ADRB2 Gln27-->Glu variants for obesity in African Americans and between ADRA2A C-1291G SNP and ADBR1 haplotype for obesity in whites. We conclude that common SNPs in adrenergic receptor genes may be important susceptibility loci for obesity and related alterations. Because of the limited size of our populations, our results should be interpreted with caution and should be replicated in larger populations.

Tobacco smoking and the ADRA2A C-1291G polymorphism

The aim of the present study is to test for possible associations between the C-1291G polymorphism in the alpha2A-adrenergic receptor gene (ADRA2A) with tobacco smoking and alcohol dependence. The genotype and allele frequencies were compared in three groups of European-derived Brazilian males: individuals with co-occurrence of tobacco smoking and alcohol dependence (N = 110), with tobacco smoking (N = 121) and controls (N = 114). The frequency of the G allele was higher in the group with both conditions, intermediate among subjects with smoking, and lower among controls (chi(2) = 8.00; p = 0.02). The chi(2) partitioning did not reveal significant differences between the sample with the two conditions and the sample of smokers (chi(2) = 0.82; p = 0.36). Combining both groups, the difference to the non-smoking controls is higher than the one observed in the three-groups analysis (chi(2) = 7.18; p = 0.007). The results suggest a role for the ADRA2A C-1291G polymorphism, notably the G allele, in the predisposition to tobacco smoking. The influence of the ADRA2A gene in nicotine and other substance dependencies should be more extensively assessed in future studies.

Association between alpha-2a-adrenergic receptor gene and ADHD inattentive type

BACKGROUND

Previous investigations have demonstrated that an MspI polymorphism at the adrenergic alpha2A receptor gene (ADRA2A) is associated with severity of attention-deficit/hyperactivity disorder (ADHD) inattentive symptoms in clinical samples composed mainly of subjects with ADHD, combined type. This study aimed to investigate the association between this ADRA2A polymorphism and attention-deficit/hyperactivity disorder-inattentive type (ADHD-I) in a nonreferred sample.

METHODS

In a case-control study, we assessed a sample of 100 children and adolescents with ADHD-I and 100 non-ADHD controls. Cases and controls were matched by gender and age and were screened by using teacher reports in a revised version of the Swanson, Nolan, and Pelham rating scale at 12 schools. Psychiatric diagnoses were derived through structured diagnostic interviews.

RESULTS

Homozygous subjects for the G allele at the ADRA2A had significantly higher odds ratio (OR) for ADHD-I than did those with other genotypes (CC + CG genotypes), even after adjusting for potential confounders (p = .02; OR = 3.78; 95% confidence interval = 1.23-11.62). In family-based analyses, no significant associations were detected.

CONCLUSIONS

Our results suggest that the ADRA2A may be associated with ADHD-I, replicating previous findings from clinical samples that have suggested the importance of this gene for the dimension of inattention. In addition, these results support the role of the noradrenergic system in ADHD.

Alpha-adrenoceptor gene variants and autonomic nervous system function in a young healthy Japanese population

alpha(1A)-adrenergic receptor (alpha(1A)-AR) regulates the cardiac and peripheral vascular system through sympathetic activation, and alpha(2A)-AR and alpha(2C)-AR subtypes are essential for presynaptic feedback regulation of catecholamine release from the central and peripheral sympathetic nerve. Genetic variations in each human alpha-AR subtype gene have been identified and have been implicated in hypertension and cardiovascular disease. It is not yet clear whether these genetic variations actually have an effect on sympatho-vagal modulation. The aim of the present study was to evaluate the relation between the five representative genetic polymorphisms of alpha-AR subtypes (Arg347Cys of alpha(1A)-AR; C-1291G, Asn251Lys, and DraI RFLP of alpha(2A)-AR; and Del322-325 of alpha(2C)-AR) and autonomic nervous system (ANS) function in young and healthy Japanese males. One hundred forty-nine subjects were genotyped for each alpha-AR polymorphism, and underwent evaluation of ANS function by power spectral analysis of heart rate variability (HRV) during supine rest and in a standing position. In a supine position, the alpha(1A)-AR 347Cys allele was significantly associated with lower HRV sympathetic index (normalized low frequency power [LF(%)] and LF:HF ratio) and higher HRV parasympathetic index [HF(%)]. Meanwhile, subjects with the alpha(2C)-AR Del322-325 allele had markedly higher LF(%) and LF:HF ratio and lower HF(%) than noncarriers. Thus, the alpha(1A)-AR and alpha(2C)-AR genetic variations influence sympatho-vagal balance even in young and healthy normotensive states, which could be postulated to constitute an intermediate phenotype for future pathological episodes of various ANS dysfunction-related diseases.

Variation in the alpha2B-adrenergic receptor gene (ADRA2B) and its relationship to vascular response in vivo

The alpha2B-adrenergic receptor (ADRA2B) plays an important role in vasoconstriction and blood pressure regulation. One common variant in the ADRA2B gene (del 301--303) has been identified, and results in markedly decreased receptor desensitization in vitro but does not alter vascular sensitivity in vivo. Therefore, we fully characterized genetic variations in ADRA2B and related them to phenotype in vivo. We examined 5812 bp of contiguous sequence of ADRA2B (promoter, exonic, and 3'-untranslated region; 3'-UTR) using the polymerase chain reaction to amplify the genomic target followed by bidirectional sequencing (n=68). Haplotypes were inferred using an expectation maximization algorithm. Vasoconstriction in response to increasing doses of the highly selective alpha2-adrenergic receptor agonist, dexmedetomidine (0.01--1000 ng/min) was measured in the dorsal hand vein using a linear variable differential transformer. The dose that produced 50% (ED50) of maximum venoconstriction (Emax) was determined for each subject from the individual dose--response curves. ED50 and Emax were compared in subjects with and without variant alleles and haplotypes of interest. We identified 24 variable sites, 12 in the promoter region, five in the coding region (including two previously described as non-synonymous variants) and seven in the 3'-UTR region. Four haplotypes were inferred, representing approximately 95% of the cohort. One haplotype, characterized by two single nucleotide polymorphisms in the promoter region, and one in the 3'-UTR, occurred in seven of 38 African-Americans, and was associated with a lower Emax, 61.3% [95% confidence interval (CI) 39.5--83.0, n=7] compared to 78.1% (CI 73.8--82.5) in wild-types (n=61) (P=0.02). There was no association between the nine common variants and dexmedetomidine ED50. We have described novel variants and haplotypes of the ADRA2B gene. These do not alter sensitivity to a selective alpha2-adrenergic receptor agonist but some may decrease maximal venoconstriction in vivo.