A two-allele PstI RFLP for the alpha-1C adrenergic receptor gene (ADRA1C)

Vasovagal Syncope Is Associated with Variants in Genes Involved in Neurohumoral Signaling Pathways

Vasovagal syncope (VVS) is the most common cause of sudden loss of consciousness. VVS results from cerebral hypoperfusion, due to abnormal autonomic control of blood circulation, leading to arterial hypotension. It is a complex disease, and its development is largely associated with genetic susceptibility. Since abnormal neurohumoral regulation plays an important role in VVS development, we analyzed the association of VVS with polymorphic variants of ADRA1A, ADRB1, HTR1A, ADORA2A, COMT, and NOS3 genes, the products of which are involved in neurohumoral signaling, in patients with a confirmed VVS diagnosis (157 subjects) and individuals without a history of syncope (161 subjects). We were able to identify the associations between VVS and alleles/genotypes ADRA1A rs1048101, ADRB1 rs1801253, ADORA2A rs5751876, and COMT rs4680, as well as NOS3 rs2070744 in biallelic combination with COMT rs4680. Thus, we are the first to observe, within a single study, the role of the genes that encode α- and β-adrenergic receptors, catechol-O-methyltransferase, adenosine receptors and nitric oxide synthase in VVS development. These findings demonstrate that the genes involved in neurohumoral signaling pathways contribute to the formation of a genetic susceptibility to VVS.

Subtypes of alpha1-adrenoceptors in BPH: future prospects for personalized medicine

The alpha(1)-adrenoceptors (alpha(1)-ARs) are involved in regulation of prostatic smooth muscle tone, and are a critical mediator of lower urinary tract symptoms and pathophysiology in benign prostatic hyperplasia (BPH). As a result, alpha(1)-AR antagonists are now used as first-line medical treatment for BPH. Three alpha(1)-AR subtypes (alpha(1a)-AR, alpha(1b)-AR, alpha(1d)-AR) have been identified on the basis of results of pharmacological and molecular cloning studies; however, the precise physiological role of individual alpha(1)-AR subtypes remains elusive. The expression levels of alpha(1)-AR subtypes in the prostate differ between patients, and individual differences in the genetic background of patients with BPH might be associated with variation in responses to subtype-selective alpha(1)-AR antagonists. In addition, single nucleotide polymorphism and microarray-based gene expression profiling studies might provide an opportunity to identify markers that predict clinical response and therapeutic tolerance to alpha(1)-AR antagonists. Further genomic studies will refine our knowledge of the functions of alpha(1)-AR subtypes, lead to new strategies for the clinical management of BPH and, perhaps, enable personalized treatment of BPH in the future.

Association of alpha1a-adrenergic receptor polymorphism and blood pressure phenotypes in the Brazilian population

BACKGROUND

The alpha1A-adrenergic receptor (alpha1A-AR) regulates the cardiac and peripheral vascular system through sympathetic activation. Due to its important role in the regulation of vascular tone and blood pressure, we aimed to investigate the association between the Arg347Cys polymorphism in the alpha1A-AR gene and blood pressure phenotypes, in a large sample of Brazilians from an urban population.

METHODS

A total of 1568 individuals were randomly selected from the general population of the Vitória City metropolitan area. Genetic analysis of the Arg347Cys polymorphism was conducted by polymerase chain reaction/restriction fragment length polymorphism. We have compared cardiovascular risk variables and genotypes using ANOVA, and Chi-square test for univariate comparisons and logistic regression for multivariate comparisons.

RESULTS

Association analysis indicated a significant difference between genotype groups with respect to diastolic blood pressure (p = 0.04), but not systolic blood pressure (p = 0.12). In addition, presence of the Cys/Cys genotype was marginally associated with hypertension in our population (p = 0.06). Significant interaction effects were observed between the studied genetic variant, age and physical activity. Presence of the Cys/Cys genotype was associated with hypertension only in individuals with regular physical activity (odds ratio = 1.86; p = 0.03) or younger than 45 years (odds ratio = 1.27; p = 0.04).

CONCLUSION

Physical activity and age may potentially play a role by disclosing the effects of the Cys allele on blood pressure. According to our data it is possible that the Arg347Cys polymorphism can be used as a biomarker to disease risk in a selected group of individuals.

Performance of a neuro-fuzzy model in predicting weight changes of chronic schizophrenic patients exposed to antipsychotics

Artificial intelligence has become a possible solution to resolve the problem of loss of information when complexity of a disease increases. Obesity phenotypes are observable clinical features of drug-naive schizophrenic patients. In addition, atypical antipsychotic medications may cause these unwanted effects. Here we examined the performance of neuro-fuzzy modeling (NFM) in predicting weight changes in chronic schizophrenic patients exposed to antipsychotics. Two hundred and twenty inpatients meeting DSMIV diagnosis of schizophrenia, treated with antipsychotics, either typical or atypical, for more than 2 years, were recruited. All subjects were assessed in the same study period between mid-November 2003 and mid-April 2004. The baseline and first visit's physical data including weight, height and circumference were used in this study. Clinical information (Clinical Global Impression and Life Style Survey) and genotype data of five single nucleotide polymorphisms were also included as predictors. The subjects were randomly assigned into the first group (105 subjects) and second group (115 subjects), and NFM was performed by using the FuzzyTECH 5.54 software package, with a network-type structure constructed in the rule block. A complete learned model trained from merged data of the first and second groups demonstrates that, at a prediction error of 5, 93% subjects with weight gain were identified. Our study suggests that NFM is a feasible prediction tool for obesity in schizophrenic patients exposed to antipsychotics, with further improvements required.

Association of alpha1A adrenergic receptor gene variants on chromosome 8p21 with human stage 2 hypertension

OBJECTIVE AND DESIGN

We previously reported a significant linkage between human chromosome 8p22 with essential hypertension and systolic blood pressure levels. On the basis of this, we used an efficient age, sex and area-matched case-control scheme to test the association of the polymorphisms in the human alpha1A adrenergic receptor (ADRA1A) gene, located on chromosome 8p21-p11.2, with essential hypertension in a northern Han Chinese population.

METHODS

Seven polymorphisms were identified by direct sequencing of genomic DNA derived from 48 randomly recruited hypertensive and 48 healthy subjects. They were also examined for association with essential hypertension in 480 stage 2 hypertensive individuals and their individually matched controls.

RESULTS

We observed significantly higher frequencies of the 347Arg allele and 2547G alleles in the cases compared with their controls (P = 0.04 and 0.007, respectively). McNemar's test revealed that carriers of 2547G alleles were at a greater risk of essential hypertension with an odds ratio of 3.00 [95% confidence interval (CI) 1.23-8.35]. We then performed a conditional logistic regression to adjust the effects of conventional risk factors, revealing an odds ratio of 2.84 for carriers of the 2547G allele (95% CI 1.15-6.99). With the haplotypic probabilities estimated using PHASE software, we performed haplotype trend regression analysis, showing a significant association between haplotype 7 and essential hypertension (P = 0.02), after adjustment for conventional risk factors.

CONCLUSIONS

Our findings suggest that the genetic variations in the ADRA1A gene are significantly associated with essential hypertension, and may play an important role in the development of essential hypertension in this Chinese population.

Novel human alpha1a-adrenoceptor single nucleotide polymorphisms alter receptor pharmacology and biological function

We identified nine naturally-occurring human single nucleotide polymorphisms (SNPs) in the alpha(1a)-adrenoceptor (alpha(1a)AR) coding region, seven of which result in amino acid change. Utilizing rat-1 fibroblasts stably expressing wild type alpha(1a)AR or each SNP at both high and low levels, we investigated the effect of these SNPs on receptor function. Compared with wild type, two SNPs (R166K, V311I) cause a decrease in binding affinity for agonists norepinephrine, epinephrine, and phenylephrine, and also shift the dose-response curve for norepinephrine stimulation of inositol phosphate (IP) production to the right (reduced potency) without altering maximal IP activity. In addition, SNP V311I and I200S display altered antagonist binding. Interestingly, a receptor with SNP G247R (located in the third intracellular loop) displays increased maximal receptor IP activity and stimulates cell growth. The increased receptor signaling for alpha(1a)AR G247R is not mediated by altered ligand binding or a deficiency in agonist-mediated desensitization, but appears to be related to enhanced receptor-G protein coupling. In conclusion, four naturally-occurring human alpha(1a)AR SNPs induce altered receptor pharmacology and/or biological activity. This finding has potentially important implications in many areas of medicine and can be used to guide alpha(1a)AR SNP choice for future clinical studies.

Haplotype block and superblock structures of the alpha1-adrenergic receptor genes reveal echoes from the chromosomal past

A significant proportion of the human genome is contained within haplotype blocks across which pairwise linkage disequilibrium (LD) is very high. However, LD is also often high between markers at more remote distances, and within different haplotype blocks. Here, we evaluate the origins of haplotype block structure in the three genes for alpha1 adrenergic receptors (alpha1-AR) in the human genome ( ADRA1A, ADRA1B and ADRA1D) by genotyping dense single-nucleotide polymorphism (SNP) marker maps, and show that LD signals between distant markers are due to the presence of extended haplotype superblocks in individuals with ancient chromosomes which have escaped historic recombination. ARs mediate the physiological effects of epinephrine and norepinephrine, and are targets of many therapeutic drugs. This work has identified haplotype backgrounds of alpha1-AR missense variants, haplotype block structures in US Caucasians and African Americans, and haplotype tag SNPs for each block, and we present strong evidence for ancient haplotype block superstructure at these genes which has been partially disrupted by recombination, and evidence for reinstatement of linkage disequilibrium by subsequent recombination events. ADRA1A is comprised of four haplotype blocks in US Caucasians, while in African Americans Block 1 is split. ADRA1B has four blocks in US Caucasians, but in African Americans only the first two blocks are present. ADRA1D has two blocks in US Caucasians, and the first block is replaced by two smaller blocks in African Americans. For both ADRA1A and ADRA1B, haplotype superstructures may represent a novel, higher-level hierarchy in the human genome, which may reduce redundancy of testing by further aggregation of genotype data.

Pharmacology and physiology of human adrenergic receptor polymorphisms

Adrenergic receptors are expressed on virtually every cell type in the body and are the receptors for epinephrine and norepinephrine within the sympathetic nervous system. They serve critical roles in maintaining homeostasis in normal physiologic settings as well as pathologic states. These receptors are also targets for therapeutically administered agonists and antagonists. Recent studies have shown that at least seven adrenergic receptor subtypes display variation in amino acid sequence in the human population due to common genetic polymorphisms. Variations in potential regulatory domains in noncoding sequence are also present. Here, we review the consequences of these polymorphisms in terms of signaling, human physiology and disease, and response to therapy.

Association of the D8S282 marker near the lipoprotein lipase gene locus with systolic blood pressure in healthy Chinese subjects

OBJECTIVE

To investigate the association between the marker D8S282 near the lipoprotein lipase (LPL) gene locus, and blood pressure, anthropometric and biochemical parameters in 229 healthy Chinese subjects. METHOD Genotyping was performed using an automated DNA sequencer and the Base ImageIR software. Eight different alleles were identified (272-286 bp) resulting in 15 genotypes in our population. We investigated the association between the common (28.8%) 278 bp allele and the anthropometric and biochemical parameters.

RESULTS

In a tertile analysis, the frequency of the 278 bp allele increased linearly ( P = 0.003) with increasing systolic blood pressure (SBP). The relationship was most evident in the females ( n = 141); SBP was higher in homozygotes for the 278 bp allele (117 +/- 10 mmHg, = 12) than those without this allele (109 +/- 9 mmHg, = 77, 0.05) and was gene-dose dependent, and this difference was more significant after adjusting for age (P = 0.004). No relationship between the locus and the anthropometric or biochemical parameters investigated was observed.

CONCLUSION

The D8S282 marker near the LPL gene locus contributes to the variance of SBP in healthy Hong Kong Chinese subjects, particularly in females.

The molecular basis of hypertension

More than 50 million Americans display blood pressures outside the safe physiological range. Unfortunately for most individuals, the molecular basis of hypertension is unknown, in part because pathological elevations of blood pressure are the result of abnormal expression of multiple genes. This review identifies a number of important blood pressure regulatory genes including their loci in the human, mouse, and rat genome. Phenotypes of gene deletions and overexpression in mice are summarized. More detailed discussion of selected gene products follows, beginning with proteins involved in ion transport, specifically the epithelial sodium channel and sodium proton exchangers. Next, proteins involved in vasodilation/natriuresis are discussed with emphasis on natriuretic peptides, guanylin/uroguanylin, and nitric oxide. The renin angiotensin aldosterone system has an important role antagonizing the vasodilatory cyclic GMP system.

Alpha 1a-adrenoceptor polymorphism: pharmacological characterization and association with benign prostatic hypertrophy

1. Two restriction fragment length polymorphisms of the human alpha 1a-adrenoceptor gene digested with PstI restriction enzyme exist; the nucleotide change causes the substitution of C residue for T at nucleotide 1441, thereby Arg492 to Cys492 transition, which might confer an additional putative palmitoylation site in the carboxy-terminal segment of the alpha 1a-adrenoceptor. In the present study, we compared their pharmacological properties and examined whether this alpha 1a-adrenoceptor polymorphism is associated with benign prostatic hypertrophy (BPH). 2. The frequency of alpha 1a-adrenoceptor polymorphism was not differently distributed between patients with benign prostatic hypertrophy (BPH) and normal subjects in Japan; thus, the relative frequencies of the C and T alleles were 0.90 : 0.10 in normal male subjects (n = 45) and 0.87 : 0.13 in BPH patients (n = 222), respectively. However, the frequency distribution of this polymorphism was significantly different between the Japanese and U.S. populations; thus, C and T alleles were 0.34 and 0.66 in U.S. populations. 3. Utilizing Chinese hamster ovary (CHO) cells stably expressing the two polymorphic alpha 1a-adrenoceptors (Arg492 and Cys492), we compared their binding affinity and signal transduction. Radioligand binding studies with 2-[beta-(4-hydroxy-3[125I]-iodophenyl) ethylamino-methyl]tetralone ([125I]-HEAT) showed no marked difference in the antagonist or agonist binding affinities between the two receptors. Also, both receptors were found to be coupled to the calcium signaling, and the concentration-cytosolic Ca2+ concentrations ([Ca2+]i) response relationships for noradrenaline were similar for the two polymorphic receptors. Furthermore, the receptor-mediated [Ca2+]i response was markedly desensitized after a 2 h exposure of phenylephrine (10 microM), and the extent of the desensitization was not significantly different between the two receptors. 4. In summary, the results showed that the two alpha 1a-adrenoceptors generated by genetic polymorphism have similar pharmacological characteristics, and the receptor-mediated [Ca2+]i response can be desensitized in a similar manner. The study did not provide any evidence to support the hypothesis that alpha 1a-adrenoceptor gene polymorphism is associated with BPH.

Quantitative trait locus mapping of human blood pressure to a genetic region at or near the lipoprotein lipase gene locus on chromosome 8p22

Resistance to insulin-mediated glucose disposal is a common finding in patients with non-insulin-dependent diabetes mellitus (NIDDM), as well as in nondiabetic individuals with hypertension. In an effort to identify the generic loci responsible for variations in blood pressure in individuals at increased risk of insulin resistance, we studied the distribution of blood pressure in 48 Taiwanese families with NIDDM and conducted quantitative sib-pair linkage analysis with candidate loci for insulin resistance, lipid metabolism, and blood pressure control. We found no evidence for linkage of the angiotensin converting enzyme locus on chromosome 17, nor the angiotensinogen and renin loci on chromosome 1, with either systolic or diastolic blood pressures. In contrast, we obtained significant evidence for linkage or systolic blood pressure, but not diastolic blood pressure, to a genetic region at or near the lipoprotein lipase (LPL) locus on the short arm of chromosome 8 (P = 0.002, n = 125 sib-pairs, for the haplotype generated from two simple sequence repeat markers within the LPL gene). Further strengthening this linkage observation, two flanking marker loci for LPL locus, D8S261 (9 cM telomeric to LPL locus) and D8S282 (3 cM centromeric to LPL locus), also showed evidence for linkage with systolic blood pressure (P = 0.02 and 0.0002 for D8S261 and D8S282, respectively). Two additional centromeric markers (D8S133, 5 cM from LPL locus, and NEFL, 11 cM from LPL locus) yielded significant P values of 0.01 and 0.001, respectively. Allelic variation around the LPL gene locus accounted for as much as 52-73% of the total interindividual variation in systolic blood pressure levels in this data set. Thus, we have identified a genetic locus at or near the LPL gene locus which contributes to the variation of systolic blood pressure levels in nondiabetic family members at high risk for insulin resistance and NIDDM.