G protein beta3 subunit variant and essential hypertension in Taiwan - a case-control study

G-protein beta 3 subunit polymorphisms and essential hypertension: a case-control association study in northern Han Chinese

OBJECTIVE

To explore the association between the three polymorphisms [ C825T, C1429T and G(-350)A] of the gene encoding the G protein beta 3 subunit (GNB3) and hypertension by performing a case-control study in the northern Han Chinese population.

METHODS

We recruited 731 hypertensive patients and 673 control subjects (the calculated power value was > 0.8). Genotyping was performed to identify C825T, C1429T and G(-350)A polymorphisms using the TaqMan assay. Comparisons of allelic and genotypic frequencies between cases and controls were made by using the chi-square test. Logistic regression analyses were performed to investigate the relationships between the three polymorphisms of GNB3 gene under different genetic models (additive, dominant and recessive models).

RESULTS

The genotype distribution and allele frequencies of C825T, C1429T and G(-350)A polymorphisms did not differ significantly between hypertensive patients and control subjects, either when the full sample was assessed, or when the sample was stratified by gender. No significant association was observed between C825T, C1429T and G(-350)A polymorphisms and the risk of essential hypertension in any genetic model. Linkage disequilibrium was only detected between C825T and C1429T polymorphisms. Haplotype analyses observed that none of the three estimated haplotypes significantly increased the risk of hypertension.

CONCLUSIONS

Our study suggested that the GNB3 gene polymorphisms [C825T, C1429T and G(-350)A] were not significantly associated with essential hypertension in northern Han Chinese population.

The C825T polymorphism of the G-protein β3 subunit gene and its association with hypertension and stroke: an updated meta-analysis

OBJECTIVE

Several epidemiological studies have evaluated the association between the GNB3 C825T polymorphism and hypertension or stroke. The results of these studies were inconsistent; therefore, we performed a meta-analysis to clarify these discrepancies.

METHODS

We systematically searched the PubMed, Embase, Web of Science, CNKI, and CBM databases, and manually searched reference lists of relevant papers, meeting abstracts, and relevant journals. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for dominant, recessive, and allelic models. A fixed or random effects model was separately adopted depending on study heterogeneity. Subgroup and sensitivity analyses were performed to detect study heterogeneity and examine result stability, respectively. Publication bias was tested using funnel plots, the Egger's regression test, and Begg's test.

RESULTS

We screened 66 studies regarding hypertension and eight concerning stroke. A combined analysis showed that only the allelic model found a marginal association with hypertension (OR = 1.07, 95% CI = 1.01-1.13) and female gender (OR = 1.11, 95% CI = 0.99-1.24). However, no comparison models found an association with stroke (allelic model: OR = 1.11, 95% CI = 0.94-1.32; dominant model: OR = 1.16, 95% CI = 0.92-1.48; and recessive model: OR = 1.05, 95% CI = 0.97-1.14). Sensitivity analysis suggested that all models did not yield a relationship to hypertension or stroke among Asians. Besides, there was a lack of statistical association with hypertension in Caucasians, which maybe due to a small sample size. When we restricted the included studies to normal populations according to the Hardy-Weinberg equilibrium, no association was found.

CONCLUSIONS

There was no evidence indicating that the 825T allele or TT genotype was associated with hypertension or stroke in Asians or hypertension in Caucasians. However, further studies regarding Africans and other ethnicities are needed to identify further correlations.

A two-stage matched case-control study on multiple hypertensive candidate genes in Han Chinese

BACKGROUND

Hypertension affects about 1/3 of adults worldwide, ~3.8 million in Taiwan, 160 million in China, and 1 billion worldwide. It is a major risk factor leading to stroke, cardiovascular disease, and end-stage renal disease. In each year, more than 13.5 million deaths are due to hypertension-related diseases worldwide.

METHODS

We performed a two-stage association study of hypertension using genotype data of single-nucleotide polymorphisms (SNPs) from 992 young-onset hypertensive cases and 992 matched controls of Han Chinese in Taiwan. A total of 238 SNPs of 36 highly replicated hypertension candidate genes with functional importance were investigated. Association analysis was carried out using conditional logistic regression.

RESULTS

We identified two SNPs that were strongly associated with hypertension in both the first and the second stages. The first SNP (rs2301339) is located at guanine nucleotide-binding protein β3 subunit (GNB3) and the other one (rs17254521) is located at insulin receptor (INSR).

CONCLUSIONS

SNP rs2301339 is perfectly linked in linkage disequilibrium (LD) with C825T (rs5443) which has been associated with hypertension in Caucasian, but inconsistent in Asian populations. However, we found that in our sample this SNP has an opposite effect with the previous findings. In summary, this study identified one novel SNP in GNB3 and one novel SNP in INSR that are strongly associated with young-onset hypertension. Due to relatively small sample size, the results should still be interpreted with caution and need to be replicated in other studies.

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.

Interaction between GNB3 C825T and ACE I/D polymorphisms in essential hypertension in Koreans

Essential hypertension (EH) is considered a typical polygenic disease, so the evaluation of gene-gene interactions rather than the determination of single gene effects is crucial to understanding any genetic influences. The G-protein beta3-subunit (GNB3) 825T allele, associated with enhanced G-protein signalling, is a strong candidate for interactions with polymorphisms, such as insertion/deletion (I/D) polymorphism of angiotensin I-converting enzyme (ACE) gene. We investigated whether there is an association between GNB3 C825T and ACE I/D polymorphisms for the development of EH. We carried out a case-control study of 688 hypertensive and 924 normotensive subjects recruited from South Korea. The GNB3 C825T and ACE I/D genotypes were determined by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism methods, respectively. The distributions of alleles and genotypes for the GNB3 C825T and ACE I/D polymorphisms were not found to be significantly associated with hypertensive status in either males or females. Logistic regression analysis indicated that the GNB3 825T allele carriers were positively associated with EH in males (odds ratio (OR) for TT/CT, 1.459; 95% confidence interval (CI), 1.048-2.033, P=0.0255). In analysis of gene-gene interaction, we found that there was a significant interaction between the GNB3 825T and ACE D alleles (P<0.05). OR for EH was significantly higher in 825T allele carriers with ACE D allele (OR, 1.490; 95% CI, 1.117-1.987, P=0.0067). A significant interaction between the GNB3 825T and the ACE D alleles may contribute to the predisposing effect for the development of EH in Koreans.

Studies of the association of the GNB3 825C>T polymorphism with components of the metabolic syndrome in white Danes

AIMS/HYPOTHESIS

The 825C>T polymorphism in the gene encoding the G protein beta3 subunit (GNB3) causes enhanced G protein activation and increased in vitro cell proliferation. This polymorphism is also repeatedly associated with an increased risk of hypertension and has been studied in relation to obesity with divergent results. Only a few association studies have investigated whether this polymorphism is related to type 2 diabetes or the metabolic syndrome. We estimated the impact of the GNB3 825C>T polymorphism in relatively large-scale association studies of common phenotypes of the metabolic syndrome.

MATERIALS AND METHODS

The GNB3 825C>T polymorphism was genotyped in 7,518 white Danish subjects using mass spectrometry analysis of PCR products. Case-control studies were undertaken for obesity, hypertension, type 2 diabetes and the metabolic syndrome, and a meta-analysis including data from the present study and previous studies of hypertension was performed. Quantitative trait studies of metabolic variables were carried out in 4,387 glucose-tolerant subjects.

RESULTS

We observed minor differences in 825C>T genotype distributions for type 2 diabetes (CC/CT/TT 49/41/10% (control) vs 46/46/9% (cases), respectively, p=0.007); however, after correction for multiple testing, these were not statistically significant. No association was found with hypertension, obesity or the metabolic syndrome. Curiously, the T allele was associated with nominally lower systolic and diastolic blood pressure levels-a finding in contrast with most previous studies-but not with other metabolic variables. Meta-analysis demonstrated a high degree of heterogeneity between study populations of different ethnic origin. Although there was a tendency towards an increased risk of hypertension among 825T allele carriers, this was not statistically significant.

CONCLUSIONS/INTERPRETATION

The present study suggests no major involvement of the GNB3 825C>T polymorphism in components of the metabolic syndrome.

G Protein β3 Subunit Gene Variants and Essential Hypertension in the Northern Chinese Han Population

Recently a novel C825T polymorphism in the G protein beta3 subunit gene was identified that showed an association with hypertension in a German population; the results of studies in other populations have been inconsistent. To examine the contribution of GNB3 polymorphisms to the development of hypertension in the northern Chinese Han population, we conducted a case-control study consisting of 501 hypertensive cases and 503 controls using the G(-350)A, C825T and C1429T polymorphisms. Genotypes of samples were determined by PCR and restriction digestion. Single locus analysis showed a significant association between G(-350)A and hypertension (P = 0.01) but no association for C825T or C1429T. The three polymorphisms were in tight linkage disequilibrium (D'=-1 for G(-350)A-C825T, D'= 0.92 for C825T-C1429T) and a total of 7 haplotypes were observed in the entire population. Haplotype A-C-C was found to be significantly related to hypertension (P = 0.032) and A-C-C carriers had a more than two-fold higher risk of hypertension than non-carriers, after adjustment for BMI and glucose. In conclusion, our study suggests that G(-350)A is a potential functional polymorphism that may be related to hypertension, whereas the C825T and C1429T polymorphisms are not associated with hypertension in the northern Chinese Han population.

Genetics of human hypertension

Hypertension is a complex genetic disorder caused by interplay between several "risk" genes and environmental factors (genetic heritability approximately 30%). Most genetic studies of hypertension use a candidate gene approach and two conclusions have been made: there is no association or linkage with the genes studied, or the hypertension phenotype is heterogeneous and subgroups with hypertension related to certain polymorphisms cannot be identified because of background noise. Studies using intermediate phenotypes suggest the latter is most likely. Another problem is the reliability of gene structure assessment: usually only one or two gene polymorphisms are assessed. The use of intermediate phenotypes and dense mapping of candidate genes would provide a better approach for identifying genotype-phenotype correlations, which might enable the use of genotypes to identify more-specific therapeutic and preventative measures for hypertensives.

GNB3 gene C825T and ACE gene I/D polymorphisms in essential hypertension in a Kazakh genetic isolate

The Kazakh inhabitants living in Barkol pasture of northeast China belong to a genetic isolate characterized by ethnically homogeneous and a communal pastoral lifestyle. To investigate whether the polymorphisms in the G-protein beta-3 subunit (GNB3) gene and angiotensin-converting enzyme (ACE) gene are associated with essential hypertension (EH), we carried out a case-control study of 290 hypertensive subjects and 244 normotensive (NT) controls randomly selected from Kazakh populations of Barkol. A previous medical history of diabetes and hypertension, and body mass index (BMI) was recorded. Plasma glucose, triglyceride, and cholesterol were measured. The insertion/deletion (I/D) polymorphism of the ACE gene and the C825T polymorphism of the GNB3 gene were determined by the polymerase chain reaction (PCR) technique. The distributions of genotypes and alleles for the two polymorphisms did not differ significantly between the case and control populations, and odds ratio of EH related to the ACE gene D allele and GNB3 gene T allele was not significantly different from 1.0. Logistic regression analysis shows the variation at the GNB3 and ACE did not have any statistically significant synergistic effect on blood pressure (BP). Stratification of NT and untreated hypertensives according to I/D polymorphism of ACE gene and C825T polymorphism of GNB3 gene disclosed no significant difference across genotypes with respect to BMI, glucose, triglyceride, cholesterol, systolic and diastolic BP. In conclusion, the polymorphisms in the GNB3 gene and ACE gene, solely or combined, did not confer a significantly increased risk for the development of EH in the Kazakh isolate of northeast China.

Lack of association of human G-protein ??3 subunit variant with hypertension in Japanese workers

OBJECTIVE

To examine the association between hypertension and the C825T polymorphism in the G-protein beta 3 subunit gene in Japanese workers.

METHODS

This study used logistic regression analysis and multiple regression analyses to investigate whether the C825T polymorphism was associated independently with hypertension or blood pressure when factors such as age, body mass index, blood chemistry and lifestyle were taken into consideration. The target subjects were 1452 male and 1169 female workers selected from 3834 male and 2591 female workers in a single company. Hypertension was defined as a systolic blood pressure > or = 140 mmHg and/or diastolic blood pressure > or = 90 mmHg, or taking antihypertensive medication. The power of the study was estimated as 83% for males and 41% for females based on allelic frequencies in Caucasians.

RESULTS

Genotype distributions for C825T in hypertensive males (CC = 58, CT = 135, TT = 63) and females (CC = 20, CT = 36, TT = 20) were not significantly different from normotensive males (CC = 300, CT = 614, TT = 282) or females (CC = 274, CT = 602, TT = 217), respectively. Allele distributions were not significantly different in either sex. Multiple logistic regression analysis showed that genotype was not associated significantly with hypertension, whereas there was a significant relationship between hypertension and age, family history of hypertension, body mass index, hematocrit, platelet count, gamma-glutamyl transpeptidase (gamma-GTP) and uric acid. Data analysis using one-way analysis of variance and multiple regression showed that the C825T allele had no significant influence on either systolic, diastolic or mean blood pressure.

CONCLUSIONS

This study indicates that the C825T polymorphism is not a significant factor for hypertension or blood pressures in Japanese people. Targeting of this polymorphism is therefore unlikely to be beneficial when attempting to prevent hypertension in the general Japanese population.

G-protein beta3 subunit 825T allele and hypertension

The G-protein beta3 subunit (GNB3) C825T polymorphism was detected through a classical candidate gene approach using cell lines with enhanced G-protein activation from patients with essential hypertension. The 825T allele is associated with the expression of a shortened, functionally active splice variant of the G-protein beta3 subunit and enhanced intracellular signal transduction. Independent studies have confirmed an association of the 825T allele with hypertension in whites. Potential pathogenetic mechanisms comprise an increased susceptibility for obesity in 825T allele carriers and, potentially, increased responsiveness to vasoactive hormones. Both phenomena appear to be strongly influenced by lifestyle in the sense of a gene-environment interaction. Whether hypertensive 825T allele carriers are at increased risk for stroke and left ventricular hypertrophy remains controversial. Current studies try to define optimal therapy strategies for hypertensive 825T allele carriers.

G-protein beta3 subunit C825T polymorphism: no association with risk for hypertension and obesity

OBJECTIVE

Several recent studies have indicated that a C825T polymorphism in the gene encoding the G-protein beta3 subunit is a significant risk factor for hypertension and obesity. In this study, we tested whether this polymorphism is associated with hypertension and obesity in white men.

DESIGN

Population-based prospective cohort study.

METHODS

We followed a cohort of 903 men, aged 42-61 years at baseline, for an average time of 4.2 years. Genotyping was performed by polymerase chain reaction.

RESULTS

The genotype distribution was in Hardy-Weinberg equilibrium: 514 (57%) had the CC genotype, 49 (5%) had the TT genotype and 340 (38%) were heterozygous (T:C = 0.24:0.76). There was no statistically significant difference between the genotype groups in respect to baseline and end of follow-up risk for hypertension or obesity, systolic or diastolic blood pressure, or body mass index.

CONCLUSION

We conclude that the C825T polymorphism of the G-protein beta3 subunit gene does not notably contribute to the development of hypertension or obesity, and is not a significant determinant for blood pressure and body mass index in white men.