G-protein beta3 subunit 825T allele and hypertension

Cataloging the potential SNPs (single nucleotide polymorphisms) associated with quantitative traits, viz. BMI (body mass index), IQ (intelligence quotient) and BP (blood pressure): an updated review

Background

Single nucleotide polymorphism (SNP) variants are abundant, persistent and widely distributed across the genome and are frequently linked to the development of genetic diseases. Identifying SNPs that underpin complex diseases can aid scientists in the discovery of disease-related genes by allowing for early detection, effective medication and eventually disease prevention.

Main body

Various SNP or polymorphism-based studies were used to categorize different SNPs potentially related to three quantitative traits: body mass index (BMI), intelligence quotient (IQ) and blood pressure, and then uncovered common SNPs for these three traits. We employed SNPedia, RefSNP Report, GWAS Catalog, Gene Cards (Data Bases), PubMed and Google Scholar search engines to find relevant material on SNPs associated with three quantitative traits. As a result, we detected three common SNPs for all three quantitative traits in global populations: SNP rs6265 of the BDNF gene on chromosome 11p14.1, SNP rs131070325 of the SL39A8 gene on chromosome 4p24 and SNP rs4680 of the COMT gene on chromosome 22q11.21.

Conclusion

In our review, we focused on the prevalent SNPs and gene expression activities that influence these three quantitative traits. These SNPs have been used to detect and map complex, common illnesses in communities for homogeneity testing and pharmacogenetic studies. High blood pressure, diabetes and heart disease, as well as BMI, schizophrenia and IQ, can all be predicted using common SNPs. Finally, the results of our work can be used to find common SNPs and genes that regulate these three quantitative features across the genome.

Using literature-based discovery to identify candidate genes for the interaction between myocardial infarction and depression

Background

A multidirectional relationship has been demonstrated between myocardial infarction (MI) and depression. However, the causal genetic factors and molecular mechanisms underlying this interaction remain unclear. The main purpose of this study was to identify potential candidate genes for the interaction between the two diseases.

Methods

Using a bioinformatics approach and existing gene expression data in the biomedical discovery support system (BITOLA), we defined the starting concept X as “Myocardial Infarction” and end concept Z as “Major Depressive Disorder” or “Depressive disorder”. All intermediate concepts relevant to the “Gene or Gene Product” for MI and depression were searched. Gene expression data and tissue-specific expression of potential candidate genes were evaluated using the Human eFP (electronic Fluorescent Pictograph) Browser, and intermediate concepts were filtered by manual inspection.

Results

Our analysis identified 128 genes common to both the “MI” and “depression” text mining concepts. Twenty-three of the 128 genes were selected as intermediates for this study, 9 of which passed the manual filtering step. Among the 9 genes, LCAT, CD4, SERPINA1, IL6, and PPBP failed to pass the follow-up filter in the Human eFP Browser, due to their low levels in the heart tissue. Finally, four genes (GNB3, CNR1, MTHFR, and NCAM1) remained.

Conclusions

GNB3, CNR1, MTHFR, and NCAM1 are putative new candidate genes that may influence the interactions between MI and depression, and may represent potential targets for therapeutic intervention.

Single Nucleotide Polymorphisms in Chemosensory Pathway Genes GNB3, TAS2R19, and TAS2R38 Are Associated with Chronic Rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is a multifaceted disease with a significant genetic component. The importance of taste receptor signaling has recently been highlighted in CRS; single nucleotide polymorphisms (SNPs) of bitter tastant-responsive G-protein-coupled receptors have been linked with CRS and with altered innate immune responses to multiple bacterially derived signals.

OBJECTIVE

To determine in CRS the frequency of six SNPs in genes with known bitter tastant signaling function.

METHODS

Genomic DNA was isolated from 74 CRS volunteers in West Virginia, and allele frequency was determined and compared with demographically matched data from the 1,000 Genomes database.

RESULTS

For two SNPs in a gene recently associated with bitterant signaling regulation, RGS21, there were no associations with CRS (although the frequency of the minor allele of RGS21, rs7528947, was seen to increase with increasing Lund-Mackay CT staging score). Two TAS2R bitter taste receptor gene variants (TAS2R19 rs10772420 and TAS2R38 rs713598), identified in prior CRS genetics studies, were found to have similar associations in this study.

CONCLUSION

Unique to our study is the establishment of an association between CRS in this patient population and GNB3 SNP rs5443, a variation in an established G protein component downstream of bitterant receptor signal transduction.

Pathway-based gene-gene interaction network modelling to predict potential biomarkers of essential hypertension

Essential hypertension (EH) is a major risk factor for cardiovascular disease. Despite considerable efforts to elucidate the pathogenesis of EH, there is an imperious need for novel indicators of EH. This study aimed to develop a method to predict potential biomarkers of EH from the point of view of network. A pathway-based gene-gene interaction (GGI) network model was constructed and analyzed, containing 116 nodes and 1272 connections. The nodes represented EH-related genes, and that connections represented their interactions. The network showed a small-world property and uneven degree distribution, suggesting that a few highly interconnected hubs played a vital role in EH. An inherent hierarchy and assortative mixing pattern were also observed in the network. GNAS, GNB3, PF4 and PPBP showed the highest values of degrees and centrality indices, and were chosen as potential biomarkers of EH. A two-mode network model based on the potential biomarkers demonstrated that hemostasis and GPCR ligand binding pathway were key pathways contributing to EH. Results of this study improve our current understanding of the molecular mechanisms driving EH. The selected genes and pathways have the potential to be used in the diagnosis and treatment of EH. Moreover, the combination of pathway analysis and complex network methodology provides a novel strategy for searching new genetic indicators of complex diseases.

G protein beta 3(GNβ3) C825T polymorphism and irritable bowel syndrome susceptibility: an updated meta-analysis based on eleven case-control studies

Several studies have reported an association between GNβ3 C825T polymorphism and irritable bowel syndrome (IBS). However, the results remain inconclusive and controversial, particularly for the data derived from different ethnicities and IBS subtypes. Therefore, we performed an updated meta-analysis to evaluate this association. All eligible case-control studies that met the search criteria were retrieved from multiple databases, and eleven case-control studies were included for detailed evaluation. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated to assess the strengths of the association between GNβ3 C825T polymorphism and susceptibility to IBS and its subtypes. Our meta-analysis found no significantly associations of GNβ3 C825T polymorphism with IBS risk in all populations. Whereas the C allele was demonstrated to be a decreased risk factor for constipation predominant IBS (IBS-C) in allele model. Additionally, the CC genotype was found to be associated with increased diarrhea predominant IBS (IBS-D) risk in recessive model. Subgroup analysis by ethnicity revealed that these associations held true for the Asian subpopulation. In conclusion, this meta-analysis suggests the C allele of GNβ3 C825T might be associated with a decreased risk of IBS-C, and the CC genotype of GNβ3 might be associated with increased IBS-D risk.

Functional dyspepsia susceptibility is related to CD14, GNB3, MIF, and TRPV1 gene polymorphisms in the Greek population

BACKGROUND

Functional dyspepsia (FD) susceptibility might be influenced by polymorphisms of genes related to inflammation (CD14, macrophage migration inhibitory factor [MIF]), motor (GNB3), and sensory dysfunction (GNB3, TRPV1). We examined the association between CD14 rs2569190, GNB3 rs5443, MIF rs222747, and TRPV1 rs755622 gene polymorphisms with FD (Rome III criteria) in the Greek population.

METHODS

We genotyped 174 dyspeptics (115 with epigastric pain syndrome; 41% Helicobacter pylori positive) and 181 controls using polymerase chain reaction-based methods and we measured disease symptoms' burden with a modified Gastrointestinal Symptoms Related Scale.

KEY RESULTS

Homozygous for the TT genotype and the T allele of the CD14 gene were significantly associated (OR [95% CI]) with FD (2.65 [1.42-4.94] and 1.67 [1.23-2.26], respectively). The CT, TT genotypes, and T allele frequencies of GNB3 showed also significant association with FD (2.18 [1.35-3.54], 3.46 [1.30-9.23], and 2.18 [1.48-3.19]). While heterozygous GC MIF genotype was more common in dyspeptics (1.67 [1.07-2.60]), homozygous CC genotype and the C allele of TRPV1 gene were more prevalent in controls (0.47 [0.25-0.87] and 0.69 [0.51-0.92], respectively). None of the gene polymorphism was related either to dyspepsia clinical syndrome type or to the H. pylori infection. Among dyspeptics, CD14 TT genotype was related to lower epigastric pain burden score (p<.011); CD14 CT genotype was related to higher epigastric burning and nausea burden scores (p<.04) while belching score was lower (p=.027) in MIF CG dyspeptics.

CONCLUSION & INFERENCES

Functional dyspepsia susceptibility is related to CD14, GNB3, MIF, and TRPV1 gene polymorphisms, while CD14 and MIF gene variants are also associated with dyspepsia symptoms burden.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

GNB3 C825T Polymorphism and Myocardial Recovery in Peripartum Cardiomyopathy: Results of the Multicenter Investigations of Pregnancy-Associated Cardiomyopathy Study

BACKGROUND

Black women are at greater risk for peripartum cardiomyopathy (PPCM). The guanine nucleotide-binding proteins β-3 subunit (GNB3) has a polymorphism C825T. The GNB3 TT genotype more prevalent in blacks is associated with poorer outcomes. We evaluated GNB3 genotype and myocardial recovery in PPCM.

METHODS AND RESULTS

A total of 97 women with PPCM were enrolled and genotyped for the GNB3 T/C polymorphism. Left ventricular ejection fraction (LVEF) was assessed by echocardiography at entry, 6 and 12 months postpartum. LVEF over time in subjects with the GNB3 TT genotype was compared with those with the C allele overall and in black and white subsets. The cohort was 30% black, age 30+6, LVEF 0.34+0.10 at entry 31+25 days postpartum. The % GNB3 genotype for TT/CT/CC=23/41/36 and differed markedly by race (blacks=52/38/10 versus whites=10/44/46, P<0.001). In subjects with the TT genotype, LVEF at entry was lower (TT=0.31+0.09; CT+CC=0.35+0.09, P=0.054) and this difference increased at 6 (TT=0.45+0.15; CT+CC=0.53+0.08, P=0.002) and 12 months (TT=0.45+0.15; CT+CC=0.56+0.07, P<0.001.). The difference in LVEF at 12 months by genotype was most pronounced in blacks (12 months LVEF for GNB3 TT=0.39+0.16; versus CT+CC=0.53+0.09, P=0.02) but evident in whites (TT=0.50++0.11; CT+CC=0.56+0.06, P=0.04).

CONCLUSIONS

The GNB3 TT genotype was associated with lower LVEF at 6 and 12 months in women with PPCM, and this was particularly evident in blacks. Racial differences in the prevalence and impact of GNB3 TT may contribute to poorer outcomes in black women with PPCM.

The effect of angiotensin-converting enzyme polymorphism on hemodynamic response to endotracheal intubation in hypertensive patients

Endotracheal intubation elicits a hemodynamic response associated with increased heart rate and blood pressure that is influenced by the angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) genetic polymorphism which may be of importance also for the pressure response to anesthesia. A total of 337 patients underwent abdominal surgery in general anesthesia and 16% were D/D-homozygotes, 45% were I/D heterozygotes and 39% of the patients were I/I homozygotes. Before surgery most patients were in treatment for arterial hypertension. Systolic and diastolic pressure, heart rate and concentrations of catecholamines in blood were determined before and after induction of anesthesia and for up to 10 minutes following endotracheal intubation. Anesthesia decreased blood pressure and for patients presenting ID and DD, blood pressure and heart rate reached similar levels but compared to II-homozygotes, D-carriers demonstrated significantly higher levels for systolic pressure and heart rate before and after intubation (p < 0.05). The blood levels of catercholamines were similar in the three genotype groups. The incidence of ECG-determined myocardial ischemia was higher in D-allele carriers compared to I-allele homozygotes (DD 22%, ID 25% vs. II 5%). In response to anesthesia and intubation and independent of sympathetic nervous activity, D-allele carriers for ACE polymorphism increased blood pressure response and higher risk for development of cardiovascular complications compared to patients homozygous for the I-allele.

Molecular genetics of essential hypertension

Hypertension is a major public health problem in the developing as well as in developed countries due to its high prevalence and its association with coronary heart disease, renal disease, stroke, peripheral vascular disease, and related disorders. Essential hypertension (EH) is the most common diagnosis in this disease, suggesting that a monocausal etiology has not been identified. However, a number of risk factors associated with EH have also been identified such as age, sex, demographic, environmental, genetic, and vascular factors. Recent advances in molecular biological research had achieved clarifying the molecular basis of Mendelian hypertensive disorders. Molecular genetic studies have now identified mutations in several genes that cause Mendelian forms of hypertension in humans. However, none of the single genetic variants has emerged from linkage or association analyses as consistently related to the blood pressure level in every sample and in all populations. Besides, a number of polymorphisms in candidate genes have been associated with differences in blood pressure. The most prominent candidate has been the polymorphisms in the renin-angiotensin-aldosterone system. In total, EH is likely to be a polygenic disorder that results from inheritance of a number of susceptibility genes and involves multiple environmental determinants. These determinants complicate the study of blood pressure variations in the general population. The complex nature of the hypertension phenotype makes large-scale studies indispensable, when screening of familial and genetic factors was intended. In this review, recent genetic studies exploring the molecular basis of EH, including different molecular pathways, are highlighted.

G-protein beta-3 subunit genotype predicts enhanced benefit of fixed-dose isosorbide dinitrate and hydralazine: results of A-HeFT

OBJECTIVES

The purpose of this study was to evaluate the influence of the guanine nucleotide-binding proteins (G-proteins), beta-3 subunit (GNB3) genotype on the effectiveness of a fixed-dose combination of isosorbide dinitrate and hydralazine (FDC I/H) in A-HeFT (African American Heart Failure Trial).

BACKGROUND

GNB3 plays a role in alpha2-adrenergic signaling. A polymorphism (C825T) exists, and the T allele is linked to enhanced alpha-adrenergic tone and is more prevalent in African Americans.

METHODS

A total of 350 subjects enrolled in the genetic substudy (GRAHF [Genetic Risk Assessment of Heart Failure in African Americans]) were genotyped for the C825T polymorphism. The impact of FDC I/H on a composite score (CS) that incorporated death, hospital stay for heart failure, and change in quality of life (QoL) and on event-free survival were assessed in GNB3 genotype subsets.

RESULTS

The GRAHF cohort was 60% male, 25% ischemic, 97% New York Heart Association functional class III, age 57 ± 13 years, with a mean qualifying left ventricular ejection fraction of 0.24 ± 0.06. For GNB3 genotype, 184 subjects were TT (53%), 137 (39%) CT, and 29 (8%) were CC. In GNB3 TT subjects, FDC I/H improved the CS (FDC I/H = 0.50 ± 1.6; placebo = -0.11 ± 1.8, p = 0.02), QoL (FDC I/H = 0.69 ± 1.4; placebo = 0.24 ± 1.5, p = 0.04), and event-free survival (hazard ratio: 0.51, p = 0.047), but not in subjects with the C allele (for CS, FDC I/H = -0.05 ± 1.7; placebo = -0.09 ± 1.7, p = 0.87; for QoL, FDC I/H = 0.28 ± 1.5; placebo = 0.14 ± 1.5, p = 0.56; and for event-free survival, p = 0.35).

CONCLUSIONS

The GNB3 TT genotype was associated with greater therapeutic effect of FDC I/H in A-HeFT. The role of the GNB3 genotype for targeting therapy with FDC I/H deserves further study.

Interactions between the FTO and GNB3 genes contribute to varied clinical phenotypes in hypertension

BACKGROUND

The genes FTO and GNB3 are implicated in essential hypertension but their interaction remains to be explored. This study investigates the role of interaction between the two genes in the pathophysiology of essential hypertension.

METHODS/PRINCIPAL FINDINGS

In a case-control study comprising 750 controls and 550 patients, interaction between the polymorphisms of FTO and GNB3 was examined using multifactor dimensionality reduction (MDR). The influence of interaction on clinical phenotypes like systolic and diastolic blood pressure, mean arterial pressure and body mass index was also investigated. The 3-locus MDR model comprising FTO rs8050136C/A and GNB3 rs1129649T/C and rs5443C/T emerged as the best disease conferring model. Moreover, the interacted-genotypes having either 1, 2, 3, 4 or 5 risk alleles correlated with linearly increasing odds ratios of 1.91 (P = 0.027); 3.93 (P = 2.08E-06); 4.51 (P = 7.63E-07); 7.44 (P = 3.66E-08) and 11.57 (P = 1.18E-05), respectively, when compared with interacted-genotypes devoid of risk alleles. Furthermore, interactions among haplotypes of FTO (H1-9) and GNB3 (Ha-d) differed by >1.5-fold for protective-haplotypes, CTGGC+TC [H2+Ha] and CTGAC+TC [H4+Ha] (OR = 0.39, P = 0.003; OR = 0.22, P = 6.86E-05, respectively) and risk-haplotypes, AAAGC+CT [H3+Hc] and AAAGC+TT [H3+Hd] (OR = 2.91, P = 9.98E-06; OR = 2.50, P = 0.004, respectively) compared to individual haplotypes. Moreover, the effectiveness of gene-gene interaction was further corroborated with a 1.29-, 1.25- and 1.38-fold higher SBP, MAP and BMI, respectively, in patients having risk interacted-haplotype H3+Hc and 2.48-fold higher SBP having risk interacted-haplotype H3+Hd compared to individual haplotypes.

CONCLUSION

Interactions between genetic variants of FTO and GNB3 influence clinical parameters to augment hypertension.

Single nucleotide polymorphisms in G protein signaling pathway genes in preeclampsia

Preeclampsia is a pregnancy specific disorder and a risk factor for later cardiovascular disease. The cause and detailed pathophysiology remains unknown. G protein signaling is involved in a variety of physiological processes, including blood pressure regulation. We assessed whether distributions of 3 single nucleotide polymorphisms in genes coding for components of G protein signaling pathways that have been associated with hypertension differ between women with preeclampsia and normotensive pregnant women; the G protein β3 subunit gene (GNB3) C825T polymorphism (rs5443), the angiotensin II type 1 receptor gene (AGTR1) 3'UTR A1166C polymorphism (rs5186), and the regulator of G protein signaling 2 gene (RGS2) 3'UTR C1114G polymorphism (rs4606). Two separate Norwegian study populations were used; a large population based study and a smaller, but clinically well-described pregnancy biobank. A descriptive study of 43 women with eclampsia was additionally included. In the population-based study, an increased odds of preeclampsia (odds ratio, 1.21; [95% confidence interval, 1.05-1.40]; P=0.009) and recurrent preeclampsia (odds ratio, 1.43; [95% confidence interval, 1.06-1.92];, P=0.017) was found in women carrying the rs4606 CG or GG genotype. In early-onset preeclamptic patients with decidual spiral artery biopsies available (n=24), the rs4606 CG or GG genotype was more frequent in those with acute atherosis (resembling early stage of atherosclerosis) compared with those without: odds ratio, 15.0; (95% confidence interval, 2.02-111.2); P=0.004. No association was found between preeclampsia and the rs5443 or the rs5186. The genotype distribution in eclamptic women was not different from preeclamptic women. In conclusion, RGS2 rs4606 may affect the risk and progression of preeclampsia.

Lack of Association between Human G-Protein β3 Subunit Variant and Overweight in Japanese Workers*

We examined the association of the G-protein beta3 subunit gene (GNB3) C825T polymorphism with overweight in Japanese workers. This cross-sectional study used multivariate analysis to investigate whether a polymorphism in the C825T polymorphism was associated independently with overweight when factors such as age and lifestyle were taken into account. The study in 1453 men and 1172 women involved identifying subjects with the C825T genotype using the polymerase chain reaction, followed by restriction fragment-length polymorphism analysis. Overweight was defined as a BMI > or = kg/m(2). Genotype distributions for C825T in overweight men (CC = 80, CT = 162, TT = 80) and women (CC = 52, CT = 91, TT = 40) were not significantly different from normal-weight men (CC = 278, CT = 588, TT = 265) and women (CC = 242, CT = 549, TT = 198). The allele distributions were also not significantly different between either sex. The power of the study was estimated as 98% in men and 81% in women based on the allelic frequencies reported in a previous positive study in Chinese subjects. Multiple logistic regression analysis showed that the genotype was not significantly associated with overweight. In conclusion, this study indicated that the GNB3 C825T polymorphism is not a significant factor for overweight in Japanese people.

The C825T GNB3 polymorphism, independent of blood pressure, predicts cerebrovascular risk at a population level

BACKGROUND

The role of C825T polymorphism of the candidate GNB3 gene in predicting cerebrovascular outcome has been poorly explored in longitudinal setting at a population level.

METHODS

In an epidemiological setting, 1,678 men and women from general population were genotyped for C825T polymorphism of GNB3 gene and follow-up for 10 years to detect nonfatal and fatal cerebrovascular events (CE). Established cerebrovascular risk factors were used to adjust the multivariate Cox analysis for confounders.

RESULTS

Seventy-three nonfatal and 30 fatal CE were recorded. Incidence of CE was higher in TT than in C-carriers (fatal: 2.6 vs. 1.7%, P < 0.03; nonfatal: 7.8 vs. 3.9%, P < 0.03; fatal recurrences: 1.6 vs. 0.6%, P < 0.03). In Cox analysis, the TT genotype predicted nonfatal (hazard ratio 1.99, 95% confidence interval 1.05-3.79, P = 0.03), fatal (2.91, 1.05-8.12, P = 0.04), and fatal recurrent CE (6.82, 1.50-31.1, P = 0.02) also after adjustment for age, gender, systolic and diastolic blood pressure, body adiposity, atherogenetic blood lipids, serum uric acid, diabetes, calories, caffeine and ethanol intake, and coronary events at baseline. Further adjustment for historical CE made the association between TT genotype and incident fatal CE nonsignificant (hazard ratio 2.72, 95% confidence interval 0.96-7.22, P = 0.06).

CONCLUSIONS

The TT genotype of GNB3 gene predicts incident CE independent of blood pressure and other established risk factors at a population level. Further studies are needed to clarify the nature and pathways of this association.

Pharmacogenetics of antipsychotic-induced weight gain: review and clinical implications

Second-generation antipsychotics (SGAs), such as risperidone, clozapine and olanzapine, are the most common drug treatments for schizophrenia. SGAs presented an advantage over first-generation antipsychotics (FGAs), particularly regarding avoidance of extrapyramidal symptoms. However, most SGAs, and to a lesser degree FGAs, are linked to substantial weight gain. This substantial weight gain is a leading factor in patient non-compliance and poses significant risk of diabetes, lipid abnormalities (that is, metabolic syndrome) and cardiovascular events including sudden death. The purpose of this article is to review the advances made in the field of pharmacogenetics of antipsychotic-induced weight gain (AIWG). We included all published association studies in AIWG from December 2006 to date using the Medline and ISI web of knowledge databases. There has been considerable progress reaffirming previous findings and discovery of novel genetic factors. The HTR2C and leptin genes are among the most promising, and new evidence suggests that the DRD2, TNF, SNAP-25 and MC4R genes are also prominent risk factors. Further promising findings have been reported in novel susceptibility genes, such as CNR1, MDR1, ADRA1A and INSIG2. More research is required before genetically informed, personalized medicine can be applied to antipsychotic treatment; nevertheless, inroads have been made towards assessing genetic liability and plausible clinical application.

Serotonin transporter and G protein beta 3 subunit gene polymorphisms in Greeks with irritable bowel syndrome

BACKGROUND

Polymorphisms in the serotonin transporter (SERT) and G protein β3 subunit (GNB3) genes might contribute to the pathophysiology of irritable bowel syndrome (IBS). Association studies of SERT and GNB3 polymorphisms and IBS have shown diverse results among different populations, which might be due to subject composition differences.

AIMS

The aim of the study was to assess the potential association between SERT and GNB3 polymorphisms and IBS in Greeks.

METHODS

A total of 124 patients with IBS diagnosed according to the Rome III criteria and 238 healthy individuals were included in the study. SERT and GNB3 gene polymorphisms were genotyped using polymerase chain reaction-based methods.

RESULTS

It was shown that the frequencies of the SS genotype and S allele of the serotonin transporter polymorphism were significantly associated with IBS (P = 0.0314 and P = 0.019, respectively). TT genotype and T allele frequencies of G protein β3 subunit showed also significant difference between the IBS patients and healthy controls IBS (P = 0.0163 and P = 0.0001, respectively). None of the clinical symptoms analyzed was significantly associated with the polymorphisms tested.

CONCLUSIONS

The results suggest that SERT and GNB3 gene polymorphisms might be associated with irritable bowel syndrome predisposition in Greeks.

Altered neural and vascular mechanisms in hypertension

Essential hypertension is a multifactorial disorder which belongs to the main risk factors responsible for renal and cardiovascular complications. This review is focused on the experimental research of neural and vascular mechanisms involved in the high blood pressure control. The attention is paid to the abnormalities in the regulation of sympathetic nervous system activity and adrenoceptor alterations as well as the changes of membrane and intracellular processes in the vascular smooth muscle cells of spontaneously hypertensive rats. These abnormalities lead to increased vascular tone arising from altered regulation of calcium influx through L-VDCC channels, which has a crucial role for excitation-contraction coupling, as well as for so-called "calcium sensitization" mediated by the RhoA/Rho-kinase pathway. Regulation of both pathways is dependent on the complex interplay of various vasodilator and vasoconstrictor stimuli. Two major antagonistic players in the regulation of blood pressure, i.e. sympathetic nervous system (by stimulation of adrenoceptors coupled to stimulatory and inhibitory G proteins) and nitric oxide (by cGMP signaling pathway), elicit their actions via the control of calcium influx through L-VDCC. However, L-type calcium current can also be regulated by the changes in membrane potential elicited by the activation of potassium channels, the impaired function of which was detected in hypertensive animals. The dominant role of enhanced calcium influx in the pathogenesis of high blood pressure of genetically hypertensive animals is confirmed not only by therapeutic efficacy of calcium antagonists but especially by the absence of hypertension in animals in which L-type calcium current was diminished by pertussis toxin-induced inactivation of inhibitory G proteins. Although there is considerable information on the complex neural and vascular alterations in rats with established hypertension, the detailed description of their appearance during the induction of hypertension is still missing.

Impaired 3',5'-cyclic adenosine monophosphate-mediated signaling in immediate early responsive gene X-1-deficient vascular smooth muscle cells

Gene-targeted deletion of the immediate early responsive gene X-1 (IEX-1) results in a significant increase in systemic arterial blood pressure, but the underlying mechanism is not understood. Studies of arterial reactivity in isolated aortas revealed normal endothelium-dependent and -independent vasorelaxation and vasoconstriction but reduced cAMP-dependent vasorelaxation in the absence of IEX-1. This defect in cAMP signaling was also evident in endothelium-denuded aortic rings, consistent with the enhancement of mitochondrial O2·- production only in IEX-1-deficient vascular smooth muscle cells, not in endothelial cells. Excessive production of reactive oxygen species at mitochondria augmented the expression of Gα(i2), suppressing cAMP production in vascular smooth muscle cells. The role of mitochondrial reactive oxygen species in the upregulation of Gα(i2) leading to the development of hypertension was supported by the ability of antioxidant or pertussis toxin to restore the cAMP-dependent vasorelaxation to a normal level and reverse established hypertension in IEX-1 homozygous knockout mice. Our results suggest that hypertension in IEX-1 knockout mice may arise primarily from impaired cAMP signaling induced by overproduction of mitochondrial reactive oxygen species in vascular smooth muscle cells and demonstrate a causal relationship between mitochondrial dysfunction and cAMP-dependent vasorelaxation.

Pharmacogenetics of antipsychotic-induced side effects

Currently available antipsychotic drugs (APDs) carry significant, though highly variable, liability to neurologic and metabolic side effects. Pharmacogenetics approaches offer the possibility of identifying patient-specific biomarkers for predicting risk of these side effects. To date, a few single nucleotide polymorphisms (SNPs) in a handful of genes have received convergent support across multiple studies. The primary focus has been on SNPs in dopamine and serotonin receptor genes: persuasive meta-analytic evidence exists for an effect of the dopamine D2 and D3 receptor genes (DRD2 and DRD3) in risk for tardr inesia (TD) and for an effect of variation at the receptor gene (HTR2C) for liability to APD-inducec gain. However, effect sizes appear to be modest, and pharmacoeconomic considerations have not been sufficiently studied, thereby limiting clinical applicability at this time. Effects of these genes and others on risk for TD, extrapyramidal side effects, hyperprolactinemia, and weight gain are revieved in this article.

Role of C825T Polymorphism of GNβ3 Gene in Preeclampsia

OBJECTIVE

The main objective of the study was to understand the role of C825T polymorphism that generates a splice variant in the beta3 subunit of heterotrimeric G-protein in preeclampsia.

RESULTS

We analyzed genomic DNA of 151 women with preeclampsia (72 Caucasians and 79 African-Americans) and 198 women with normal delivery (102 Caucasians and 96 African-Americans) for C825T polymorphism of GNbeta3 gene. The T-allele frequency in Caucasian women with preeclampsia was 0.42 as compared to 0.25 in normal pregnant women (p = 0.0004) and in African-American women with preeclampsia was 0.82 as compared to 0.68 in normal pregnant women (p = 0.0028).

CONCLUSIONS

Results of these experiments show that the allele frequency of C825T polymorphism is significantly different in women with preeclampsia compared with women with normal delivery in Caucasian as well as African-American population.

G-protein beta3 Subunit Gene 825C/T Polymorphism Is Not Associated with Olanzapine-Induced Weight Gain in Korean Schizophrenic Patients

OBJECTIVE

Weight gain is a possible adverse effect of the use of antipsychotics, and is an important factor for long-term health and treatment compliance. Olanzapine is an atypical antipsychotic known to cause considerable weight gain. A relationship between weight gain and the G protein beta3 subunit gene (GNB3) 825C/T polymorphism has been reported. We therefore examined this possible association in a Korean schizophrenic patient group receiving olanzapine treatment.

METHODS

Weight and height measurements were obtained prior to starting olanzapine and measured again after long-term treatment. Genotyping for the 825C/T polymorphism was performed using a PCR-based method.

RESULTS

We found that long-term treatment with olanzapine resulted in mean gains in weight and body mass index (BMI) of 5.2 kg and 1.93 kg/m(2), respectively. There was a no significant difference in the mean body weight change from baseline to the endpoint after olanzapine treatment between the genotype groups (p=0.796). There were also no significant differences in genotype or allele frequencies between the severe weight-gain (more than 10%) and minimal weight-gain (less than 10%) groups (chi(2)=0.037, p=0.98; chi(2)=0.020, p=0.89).

CONCLUSION

The finding from this study thus does not support a relationship between the GNB3 825C/T polymorphism and weight gain in Korean schizophrenic patients receiving olanzapine treatment.

Relationship between G-protein beta-3 subunit C825T polymorphism and mirtazapine responses in Korean patients with major depression

AIMS

This study aimed to determine the relationship between the C825T polymorphism in the G-protein beta 3 subunit (GNB3) gene and the response to mirtazapine in a Korean population with major depressive disorder (MDD).

METHOD

Mirtazapine was administered for 8 weeks to the 101 MDD patients who completed this study. All subjects were examined using the Structured Clinical Interview for DSM-IV, and the severity of depression was assessed using the 21-item Hamilton Depression Rating (HAMD-21) scale.

RESULTS

There was a significant main effect of time on the decrease in the HAMD-21 score during the 8-week study period. However, a main effect of or an interaction of genotype with time on the decrease in the HAMD-21 score during the 8-week study period was not found. ANOVA revealed no significant effects of the GNB3 C825T polymorphism on the decrease in the HAMD-21 score at each time period.

CONCLUSION

Although the C825T polymorphism of the GNB3 gene may affect the pathogenesis of MDD, our results do not support the hypothesis that this polymorphism is involved in the therapeutic response to mirtazapine in Korean patients with MDD.

A genetic association study of 5-HTT LPR and GNbeta3 C825T polymorphisms with irritable bowel syndrome

A pharmacogenetic study suggests the 5-HTT LPR polymorphism predicts response to alosetron, and another study describes a possible association of the GNbeta3 C825T polymorphism with IBS in patients with dyspepsia. We performed a case-control association study to determine whether these polymorphisms are associated with irritable bowel syndrome (IBS). The study aim was to compare allele and genotype frequencies between cases and controls for the 5-HTT LPR and the GNbeta3 C825T polymorphism. Cases were 50 GI outpatients; controls were 53 General Medicine outpatients matched to cases for age, gender and race at a major medical centre. Participants completed a questionnaire and donated blood. DNA was genotyped using polymerase chain reaction based assays. Eighty-two per cent of cases met Rome II criteria for IBS: 12% constipation-, 46% diarrhoea-, and 42% mixed-IBS. Genotype and allele frequencies for both polymorphisms did not differ between cases and controls. However, the allele frequency of the short (S) allele of the 5-HTT LPR polymorphism was greater in those with mixed-IBS compared with controls (68%vs 45%, P < 0.05). This study suggests that the 5-HTT LPR polymorphism may be associated with mixed-IBS, but not IBS overall. No association was observed for the GNbeta3 C825T polymorphism with IBS overall or subtypes.

APOC3 promoter polymorphisms C-482T and T-455C are associated with the metabolic syndrome

BACKGROUND

Despite the growing epidemic of the metabolic syndrome (MetS), few studies have evaluated genetic polymorphisms associated with the MetS phenotype. One candidate, APOC3, modulates lipid and lipoprotein metabolism and the promoter polymorphisms C-482T/T-455C are associated with loss of insulin downregulation.

METHODS

One hundred twenty two consecutive MetS cases were matched by age, sex and race in a 1:1 case-control design to evaluate the prevalence of common polymorphisms in the following candidate genes: APOC3, APOE, B3AR, FABP2, GNB3, LPL, and PPARalpha and PPARgamma.

RESULTS

Compared to controls, MetS subjects exhibited a greater prevalence of APOC3 promoter polymorphisms. Specifically, the frequency of the variant C-482T and T-455C alleles was 70.5 and 81.9% of cases compared to 43.4 and 54.1% in controls, respectively (p <0.0001). Overall, APOC3 promoter variants were associated with a greater likelihood of MetS compared to wild type [C-482T (OR: 4.3; 95% CI: 2.2, 8.6 [p <0.0001]), T-455C (OR: 3.6; 95% CI: 2.0, 6.7 [p <0.0001])]. No material differences were identified between the other genetic variants tested and prevalence of MetS.

CONCLUSIONS

These data, therefore, suggest that the APOC3 promoter polymorphisms C-482T and T-455C are associated with the MetS.

The GNB3 C825T polymorphism and essential hypertension: a meta-analysis of 34 studies including 14,094 cases and 17,760 controls

OBJECTIVES

The C825T single nucleotide polymorphism of the G-protein beta3 (GNB3) has been implicated in susceptibility to essential hypertension, through the expression of an alternatively spliced truncated variant. In an effort to clarify earlier inconclusive results, we performed a meta-analysis of population-based case-control genetic association studies.

METHODS

Random-effects methods were applied on summary data in order to combine the results of the individual studies.

RESULTS

We identified in total 34 studies, including 14,094 hypertensive cases and 17,760 controls. The TT versus CC + CT contrast yielded an overall odds ratio (OR) of 1.08 [95% confidence interval (CI): 1.01, 1.15], the contrast of TT + CT versus CC, an OR of 1.17 (95% CI: 1.06, 1.29), whereas that of the T allele versus C allele yielded a non-significant OR of 1.05 (95% CI: 0.98, 1.13). There was moderate evidence for a publication bias in the latter two contrasts, which was eliminated after excluding studies not in Hardy-Weinberg equilibrium and those performed on non-normal populations (those with a diagnosis of diabetes, obesity and myocardial infarction). Subgroup analyses revealed that non-significant estimates arose from studies on Asian populations, as opposed to the Caucasian ones. Furthermore, the frequency of the T allele was lower in Caucasians and these populations were found to inhabit higher latitudes.

CONCLUSIONS

The findings are in agreement with a recently proposed causal model for systolic blood pressure, which correlates it with the T allele and the absolute latitude. Further studies are needed in order to fully address questions about the aetiological mechanism of the particular association, as well as to study the effect in populations of African descent.

Contribution of several candidate gene polymorphisms in the determination of adiposity changes: results from the Québec Family Study

BACKGROUND

Several candidate genes have been associated with obesity, but very few studies have tested more than one gene simultaneously.

METHODS

In this study, 15 polymorphisms in 10 candidate genes of obesity were tested for association with changes in adiposity measured over a period of 6-10 years in a maximum of 332 adult subjects with a wide range of adiposity (17.5<body mass index (BMI)<55.6 kg/m2) from the Québec Family Study. Stepwise regression models were used to identify the combination of genes explaining changes in adiposity after adjustment for age (initial value), gender, initial value of the adiposity variable and duration of follow-up. Analyses were carried out in the whole sample and repeated while stratifying on age (<40 and>or=40 years).

RESULTS

In the whole sample, the variance in age-related adiposity changes explained by the candidate gene polymorphisms ranged from 3.1% (BMI, P<0.05) to 8.5% (fat mass (FM), P<or=0.0005). The genes retained in the prediction model for changes in FM were leptin (P<or=0.05), guanine nucleotide binding protein beta3 (P<or=0.05), adrenergic receptor beta3 (P<or=0.05), neuromedin beta (P<or=0.05) and peroxisome proliferator-activated receptor-gamma2 (P<or=0.10). The effects of the genes were significant in both age groups, but the genes contributing to adiposity changes were different and their effects were stronger in the younger than in the older age group.

CONCLUSION

This study suggests that models including genetic information from several candidate gene polymorphisms can significantly contribute to the changes in adiposity over time, that different genes may act at different ages and that genetic information could be useful for the identification of individuals at high risk for gaining body fat over time.

G-protein beta3 subunit variant C825T is a risk factor for hypertension in Japanese females--a prospective cohort study over 5 years

The relationship between the G-protein beta3 subunit variant C825T and risk of hypertension was examined in a prospective cohort study of Japanese workers. This study included observations over a 5-year period from 1997 to 2002 on 878 males and 692 females who were normotensive at entry. Hypertension was defined as systolic blood pressure > or =140 mmHg and/or diastolic blood pressure > or =90 mmHg, or taking antihypertensive medication. Pooled logistic regression analyses were performed using C825T genotype, age, body mass index, lifestyle, and the result of blood chemistries as the covariates. Multivariate pooled logistic regression analysis showed the risk of hypertension was 2.31 times higher in females with the TT genotype than in females with the CC genotype (95% confidence interval: 1.07-4.96), after adjustment for the effects of other potential covariates. In contrast, no significant risk of hypertension was observed with the TT genotype in male subjects. This study indicates that the 825T allele is an independent risk factor for hypertension in Japanese females, and suggests that this polymorphism may be a beneficial prognostic marker for hypertension in the general Japanese female population.

G-protein beta-3 subunit C825T polymorphism, sodium and arterial blood pressure: a community-based study of Japanese men and women

Epidemiological evidence on gene-environment effects of the G-protein beta-3 subunit C825T polymorphisms and sodium on blood pressure in the free-living general population is limited. We examined the associations between the C825T polymorphism and blood pressure levels, stratified by the sodium variables estimated by 24-h urinary sodium excretion and a dietary questionnaire, among 1,471 men and women aged 30-74 from a community in Japan. Our a priori hypothesis was that individuals with the 825T allele have elevated blood pressure among subjects with a high sodium intake. Among the whole group, the systolic blood pressure level was +2.2 mmHg (p = 0.10) higher in TT than CC genotype individuals after adjustment for sex, age, antihypertensive medication use, body mass index, and alcohol consumption. This difference was more evident among individuals with low sodium excretion (+4.5 mmHg, p = 0.01), low present sodium intake (+3.2 mmHg, p = 0.11), and low past sodium intake (+4.8 mmHg, p = 0.02). No associations were observed among those with high sodium variables. Our results indicate that the G-protein beta-3 subunit C825T polymorphism is associated with higher systolic blood pressure levels in a large free-living Japanese population, and more specifically in women with a low sodium intake. This finding helps to explain part of the discrepancy between the previously reported genetic association among different ethnic groups.

Clinical application of pharmacogenetics in gastrointestinal diseases

As knowledge of the human genome grows, there will be a direct impact on the management of specific diseases. Within gastroenterology and hepatology, there has been a change in the understanding of how variations or mutations in genes involved in drug metabolism or disease pathophysiology affect response to therapy. This review discusses the application of clinical pharmacogenetics to the following diseases and disorders: inflammatory bowel disease, Helicobacter pylori infections, gastroesophageal reflux disease, irritable bowel syndrome, functional dyspepsia, liver transplantation and colon cancer. Although only a few genotyping tests are regularly used in clinical practice, it is anticipated that studies will propel the routine use of many of the tests described in this review, in the future.

G-protein beta 3 subunit polymorphism C1429T and low-density lipoprotein receptor-related protein 5 polymorphism A1330V are risk factors for hypercholesterolemia in Japanese males--a prospective study over 5 years

We examined the relationship between the C825T, C1429T, and A-350G variants in the G-protein beta 3 subunit (GNB3) gene, the A1330V and Q89R variants in the low-density lipoprotein receptor-related protein 5 (LRP5) gene, and the risk of hypercholesterolemia in a prospective study in Japanese workers. This study included observations over a 5-year period from 1997 to 2002 on 936 males and 662 females who were not hypercholesterolemic on entry. Hypercholesterolemia was defined as a serum total cholesterol level of 240 mg/dL or higher. Pooled logistic regression analyses were performed using either of the gene variants with age, body mass index, smoking, alcohol consumption, and habitual exercise as the covariates. The risk of the development of hypercholesterolemia was 2.27 times higher in males with the TT genotype of GNB3/C1429T than in males with the CC genotype (95% confidence interval, 1.04-4.94), after adjustment for the effects of other potential covariates. Simultaneously, the risk was 1.49 times higher in males with the AV genotype of LRP5/A1330V than in males with the AA genotype (95% confidence interval, 1.04-2.12) after adjustment for the effects of other potential covariates. This study indicates the GNB3/C1429T and LRP5/A1330V are independent risk factors for hypercholesterolemia in Japanese males and suggests that targeting these polymorphisms may be beneficial when attempting to prevent hypercholesterolemia in the general Japanese male population.

G-protein beta3 subunit gene variant is unlikely to have a significant influence on serum uric acid level in Japanese workers

The C825T variant of the G-protein beta3 subunit (GNB3) gene has attracted renewed attention as a candidate gene for obesity, hypertension and hyperuricemia. The main role of G-protein is to translate signals from the cell surface into a cellular response. The 825T allele is associated with a splice variant of GNB3 protein and enhanced G-protein activation. We examined the relationship between this variant and the risk of hyperuricemia in Japanese workers. The study subjects were 1,452 men and 1,169 women selected from 3,834 men and 2,591 women in 1997. On the basis of common clinical criteria, hyperuricemia I was defined as serum uric acid >or= 7.0 mg/dl in men and 6.0 mg/dl in women or taking antihyperuricemic medication. The hyperuricemia I group consisted of 186 men and 20 women and its control of 1,266 men and 1,149 women. Hyperuricemia II was defined as serum uric acid > 5.7 mg/dl (median) in men and 3.9 mg/dl (median) in women or taking antihyperuricemic medication. The hyperuricemic II group consisted of 684 men and 570 women and its control of 768 men and 599 women. To replicate previous significant results in young Caucasian men, we selected these criteria because the authors of the study in young Caucasian men adopted the median in their subjects as a cut-off. The statistical power was estimated as 99% based on the significant results in Caucasians. Genotype and allele distributions in men and women with hyperuricemia I and II were not significantly different from those in the corresponding control groups. Logistic regression analysis on hyperuricemia I and II, and multiple regression on serum uric acid level demonstrated no significant effect of the C825T genotype. Despite the sufficient statistical power, this study could not demonstrate the significant influence of C825T on hyperuricemia or serum uric acid. The targeting of this polymorphism is unlikely to be beneficial in the prevention of hyperuricemia in the general Japanese population.

G-protein beta3 subunit gene variant (C825T) is unlikely to have a significant influence on serum total cholesterol level in Japanese workers

We investigated the association between hypercholesterolemia or serum total cholesterol level and the C825T polymorphism in the G-protein ss3 subunit gene in Japanese workers using multivariate analysis to control possible confounding factors. The study subjects were 1,452 males and 1,169 females selected from 3,834 males and 2,591 females. Hypercholesterolemia was classified as either a total serum cholesterol $5.7 mmol/L (220 mg/dL) or taking lipid-lowering medication. The statistical power of the study was estimated as 99.9% based on total cholesterol levels of previous significant studies in Caucasians and Japanese. The genotype distributions in males with hypercholesterolemia (CC = 78, CT = 154, TT = 78) and females (CC = 60, CT = 137, TT = 52) were not significantly different from normal males (CC = 280, CT = 595, TT = 267) or females (CC = 234, CT = 501, TT = 185). Allele distributions also were not significantly different in either sex. Logistic regression analysis of hypercholesterolemia data and analysis of variance, t-test and multiple regression of serum total cholesterol data demonstrated no significant relationship with the C825T genotype. Despite sufficient statistical power, this study did not demonstrate a significant influence of C825T on hypercholesterolemia or serum total cholesterol level. The targeting of this polymorphism therefore is unlikely to be beneficial in preventing hypercholesterolemia in the general Japanese population.

Single-Nucleotide Polymorphisms for Diagnosis of Salt-Sensitive Hypertension

Background: Salt-sensitive (SS) hypertension affects &gt;30 million Americans and is often associated with low plasma renin activity. We tested the diagnostic validity of several candidate genes for SS and low-renin hypertension.

Methods: In Japanese patients with newly diagnosed, untreated hypertension (n = 184), we studied polymorphisms in 10 genes, including G protein–coupled receptor kinase type 4 (GRK4), some variations of which are associated with hypertension and impair D1 receptor (D1R)-inhibited renal sodium transport. We used the multifactor dimensionality reduction method to determine the genotype associated with salt sensitivity (≥10% increase in blood pressure with high sodium intake) or low renin. To determine whether the GRK4 genotype is associated with impaired D1R function, we tested the natriuretic effect of docarpamine, a dopamine prodrug, in normotensive individuals with or without GRK4 polymorphisms (n = 18).

Results: A genetic model based on GRK4 R65L, GRK4 A142V, and GRK4 A486V was 94.4% predictive of SS hypertension, whereas the single-locus model with only GRK4 A142V was 78.4% predictive, and a 2-locus model of GRK4 A142V and CYP11B2 C-344T was 77.8% predictive of low-renin hypertension. Sodium excretion was inversely related to the number of GRK4 variants in hypertensive persons, and the natriuretic response to dopaminergic stimulation was impaired in normotensive persons having ≥3 GRK4 gene variants.

Conclusions: GRK4 gene variants are associated with SS and low-renin hypertension. However, the genetic model predicting SS hypertension is different from the model for low renin, suggesting genetic differences in these 2 phenotypes. Like low-renin testing, screening for GRK4 variants may be a useful diagnostic adjunct for detection of SS hypertension.

HYPERTENSION, OBESITY AND GNB3 GENE VARIANTS

The polymorphism C825T of the gene encoding the G-protein beta 3-subunit (GNB3) was found to be associated with an increased prevalence of hypertension in a number of studies. The aim of the present study was to investigate the association between this polymorphism and blood pressure phenotypes in an urban, large and ethnically mixed population of Brazil. 2. Individuals (n=1,568) were randomly selected from the general population of the Vitória City metropolitan area. The GNB3 C825T polymorphism was genotyped in each individual. Baseline cardiovascular risk factors were collected for all participants. Cardiovascular risk variables and genotypes were compared using anova and the Chi-squared test for univariate comparisons and logistic regression for multiple comparisons. 3. A statistically significant interaction between the 825T allele and obesity was observed for systolic blood pressure (SBP; P=0.02). In fact, the C825T genotype was predictive of SBP only in individuals with increased body mass index (P=0.02). In addition, in a multiple logistic regression model conducted in the obese population and adjusted for age, sex, ethnicity, diabetes, triglycerides and total cholesterol, the presence of the T allele was significantly associated with a 1.5-fold (95% confidence interval 1.04--2.26) increased risk of hypertension. Lack of statistical power does not explain the absence of other positive gene-environment interactions. 4. The present results suggest that an important gene yen environment interaction may take place between bodyweight regulation and the GNB3 gene. This finding provides further evidence for a role of the 825T allele in hypertension susceptibility and may be used for better disease stratification.

Polymorphisms in four candidate genes in young patients with essential hypertension

AIM

To determine whether four potential genetic factors (polymorphisms in genes for alpha-adducin, beta-adducin, the G-protein beta-3 subunit and nitric oxide synthase) are important for the development of essential hypertension (EH) in Slovenian children and young adults with EH.

METHODS

Both a nuclear families approach and case-control study have been performed. Genotyping of common polymorphisms in these genes using polymerase chain reaction was carried out in 104 nuclear families (an affected child, both parents) and in 200 control patients.

RESULTS

Using the transmission disequilibrium test, no statistically significant differences were found between the frequencies of transmitted and non-transmitted alleles in nuclear families for all four investigated polymorphisms. In addition, the distributions of genotypes and alleles for the four polymorphisms did not differ significantly between our children and 200 healthy control patients. The allele frequencies of all polymorphisms were concordant with those observed in some other Caucasian populations.

CONCLUSION

We found no association between the investigated gene variants and EH, so we conclude that they do not confer a significantly increased risk of the development of EH in the Slovenian population of hypertensive children.

The C allele of theGNB3 C825T polymorphism of the G protein β3-subunit is associated with an increased risk for the development of oncocytic thyroid tumours

Carriers of the C allele of the common C825T polymorphism in the GNB3 gene of the G protein have been associated with the development of follicular thyroid adenomas. Since the C allele of this polymorphism is related to a lower signalling capacity, it was speculated whether the C825T polymorphism may play a particular role in oncocytic thyroid tumours, which are recognized for their reduced ability to synthesize thyroid-specific proteins and hormones, although they possess an intact thyroid-stimulating hormone receptor-adenylyl cyclase system. Using pyrosequencing, both the genotype distribution and the allele frequency of the C825T polymorphism were investigated in a series of 104 patients with oncocytic thyroid tumours of follicular cell origin [58 adenomas, 41 follicular thyroid carcinomas (FTCs), and five papillary thyroid carcinomas (PTCs)]; the results were compared with those obtained from 321 age and gender-matched healthy blood donors and a series of 327 non-oncocytic thyroid tumours of follicular cell origin (119 adenomas, 80 FTCs, and 186 PTCs). Analysis of the genotype distribution (comparing oncocytic with non-oncocytic tumours of the present series) revealed a significantly increased odds ratio (OR) for CC versus TT (OR = 4.22; p = 0.011) and CC versus CT (OR = 1.62; p = 0.049) carriers to develop an oncocytic thyroid tumour; ORs to develop an oncocytic thyroid tumour were also increased comparing the genotype distribution between the group of oncocytic tumours and healthy controls for CC versus TT (OR = 3.73; p = 0.017) and CC versus all T carriers (OR = 1.56; p = 0.034). Oncocytic thyroid tumours as a group showed a statistically significant increase of the C-allele frequency when compared with all non-oncocytic tumours (p = 0.0039) as well as healthy blood donors (p = 0.017). The results strongly suggest that the C allele of the GNB3 C825T polymorphism of the G protein beta3-subunit is associated with an increased risk for the development of oncocytic thyroid tumours. This polymorphism may thus be considered a (co)factor favouring the development of oncocytic thyroid tumours, although the biological mechanism(s) underlying this association remain obscure.

Update on G-protein polymorphisms in hypertension

The classic candidate gene approach continues to be the most prevalent tool in the search for the genetic basis of essential hypertension. With the list of candidate genes for this disorder steadily increasing, the pertussis toxin-sensitive inhibitory G protein (Gi) protein beta3 subunit (GNB3) gene has remained "sizzling," challenging the domination of the renin-angiotensin system. Is the genetic variability of GNB3 a causative factor underlying the pathogenesis of essential hypertension? Is the "functional" polymorphism, C825T, only "another" of the countless single nucleotide polymorphisms (SNP) for this disorder after all? As such, does its presence merely reinforce our confidence that essential hypertension is indeed polygenic? Should the C825T polymorphism be used in clinical practice and individualized antihypertensive treatment? Currently, there are still more questions than answers. In this review, in conjunction with our own research, we bring readers up to date on the latest developments of GNB3 polymorphisms in the field of hypertension.

Differential susceptibility to hypertension is due to selection during the out-of-Africa expansion

Hypertension is a leading cause of stroke, heart disease, and kidney failure. The genetic basis of blood pressure variation is largely unknown but is likely to involve genes that influence renal salt handling and arterial vessel tone. Here we argue that susceptibility to hypertension is ancestral and that differential susceptibility to hypertension is due to differential exposure to selection pressures during the out-of-Africa expansion. The most important selection pressure was climate, which produced a latitudinal cline in heat adaptation and, therefore, hypertension susceptibility. Consistent with this hypothesis, we show that ecological variables, such as latitude, temperature, and rainfall, explain worldwide variation in heat adaptation as defined by seven functional alleles in five genes involved in blood pressure regulation. The latitudinal cline in heat adaptation is consistent worldwide and is largely unmatched by latitudinal clines in short tandem repeat markers, control single nucleotide polymorphisms, or non-functional single nucleotide polymorphisms within the five genes. In addition, we show that latitude and one of these alleles, GNB3 (G protein beta3 subunit) 825T, account for a major portion of worldwide variation in blood pressure. These results suggest that the current epidemic of hypertension is due to exposures of the modern period interacting with ancestral susceptibility. Modern populations differ in susceptibility to these new exposures, however, such that those from hot environments are more susceptible to hypertension than populations from cold environments. This differential susceptibility is likely due to our history of adaptation to climate.

The genetics of irritable bowel syndrome

Because of the heterogeneity in symptoms and diagnostic findings, patients with irritable bowel syndrome (IBS) remain a challenge to treat and to study. This difficulty stems from lack of understanding of the pathophysiology of this disorder. Environmental factors likely play an important role in the pathogenesis and clinical manifestations of IBS. Several recent studies suggest a genetic basis for IBS, either in etiology or predicting response to therapy. Because of interest in studying the genetic contributors to this and other functional gastrointestinal disorders, we review the literature on genetic risk factors that might explain the familial clustering of IBS. Familial aggregation studies and twin studies suggest a modest contribution of genetics to the development of IBS. Pharmacogenomic and association studies provide stronger, although far from conclusive, evidence for genetic variants that affect expression of IBS. Together, these studies suggest that a multidisciplinary approach with clinical and psychological tools, epidemiologic methods, and genetic techniques might help elucidate the molecular components leading to the common symptoms of IBS and result in better treatments for those with IBS.

Suggestive association between the C825T polymorphism of the G-protein beta3 subunit gene (GNB3) and clinical improvement with antipsychotics in schizophrenia

G-proteins are composed of alpha, beta and gamma subunits. Once activated, these subunits play a major role in the conversion of external receptor activation into intracellular signals. The functional C825T polymorphism of the beta3 subunit gene (GNB3) has recently been shown to modulate antidepressant response, with the T-allele conferring an increased signaling and being associated with favorable antidepressant response. We hypothesized that this polymorphism may be associated with response to antipsychotics in a population of 145 chronic schizophrenic patients deriving from two study-samples and being mainly treated with clozapine for up to 6 months. Overall, the C/C genotype was significantly associated with relative clinical improvement as measured by Brief Psychiatric Rating Scale (BPRS) change scores after 6 and 12 weeks (p<0.01 and p=0.03, respectively), with estimated effect sizes ranging from 4.8 to 7%. Our results further suggest that this effect is only attributable to Caucasians when compared to African-Americans. Moreover, our findings point to the role of intracellular mechanisms in antipsychotic response.

The 825C/T polymorphism of G-protein beta3 subunit gene and risk of ischaemic stroke

In this study, we investigated the association of G protein beta3 subunit gene (GNB 3) C825T polymorphism with ischaemic stroke and its subtypes in the Chinese Han population in a large case-control study. A total of 990 ischemic stroke patients and 1124 controls were recruited from six medical centres in China. Genotype was determined by polymerase chain reaction and restriction fragment length polymorphism (RFLP) assay. Logistic regression analysis was performed to identify the independent risk factors for stroke. The frequency of 825T carriers is significantly higher in cerebral thrombosis in male subjects (OR=1.35, 95% CI, 1.01-1.82, P=0.046). After further adjustment with traditional risk factors to stroke, the association is not significant. In conclusion, the GNB3 825T allele is not an independent risk factor to ischaemic stroke in the Chinese population.

Genetic variations related to hypertension: a review

Hypertension is a complex multifactorial disorder with genetic, environmental and demographic factors contributing to its prevalence. The genetic element contribution to blood pressure variation ranges from 30 to 50%. Therefore, identifying hypertension susceptibility genes will help understanding the pathophysiology of the disease. In addition to the potential impact of genomic information in selecting antihypertensive drug therapy, it may also help in recognizing those at risk of developing the disease, which may lead to new preventive approaches. Several strategies and methods have been used to identify hypertension susceptibility genes. Currently, genetic analysis of such data produced complex results, which makes it difficult to draw final conclusion on the use of genomic data in management of hypertension. This review attempts to summarize present known genetic variations that may be implicated in the pathogenesis of hypertension and to discuss various research strategies used to identify them. It also highlights some of the opportunities and challenges, which may be encountered in interpreting the value of these genetic variations to improve management of hypertension.

Obesity reveals an association between blood pressure and the G-protein beta3-subunit gene: a study of female dizygotic twins

The 825C>T polymorphism of the G-protein beta3-subunit gene (GNB3) has been associated with hypertension, although results are not entirely consistent. In a sample of 282 female Caucasian dizygotic twins aged 21-80 years, we aimed to investigate the associations between blood pressure and five single nucleotide polymorphisms (SNPs) including the 825C>T and haplotypes of the GNB3 gene. The polymorphisms (-350A>G, 657A>T, 814G>A, 825C>T and 1429C>T) were genotyped by polymerase chain reaction-restriction enzyme assays. Regular association tests did not show a significant effect on blood pressure for any of the five SNPs. However, strongly significant interactions between the -350A>G, 825C>T and 1429C>T loci and adiposity (both body mass index and waist circumference) were observed for systolic blood pressure (Ps < 0.01) as well as diastolic blood pressure (Ps < 0.05), suggesting increases in adiposity amplify the effects of the SNPs on blood pressure. Haplotype analyses confirmed the effects of the GNB3 gene-obesity interaction on hypertension risk. Additionally, sib-transmission disequilibrium tests (sib-TDTs) showed significant associations with blood pressure for the 825C>T and 1429C>T loci. In summary, the presence of obesity reveals an association between blood pressure and the GNB3 gene in White females. Our data suggest that adiposity is a final pathway through which gene-lifestyle interactions may exert their effects on the development of hypertension. Our results from the combined SNP, haplotype and sib-TDT analyses also support the hypothesis that the 825C>T is a susceptibility locus for hypertension, whereas effects of other loci on blood pressure may result from their strong linkage disequilibrium with the 825C>T locus.