An epidemiological study of blood pressure and metabolic phenotypes in relation to the Gbeta3 C825T polymorphism

Single-Nucleotide Polymorphism in Genes Encoding G Protein Subunits GNB3 and GNAQ Increase the Risk of Cardiovascular Morbidity among Patients Undergoing Renal Replacement Therapy

Single-nucleotide polymorphisms in G protein subunits are linked to an increased risk of cardiovascular events among the general population. We assessed the effects of GNB3 c.825C > T, GNAQ -695/-694GC > TT, and GNAS c.393C > T polymorphisms on the risk of cardiovascular events among 454 patients undergoing renal replacement therapy. The patients were followed up for a median of 4.5 years after the initiation of dialysis. Carriers of the TT/TT genotype of GNAQ required stenting because of coronary artery stenosis (p = 0.0009) and developed cardiovascular events involving more than one organ system (p = 0.03) significantly earlier and more frequently than did the GC/TT or GC/GC genotypes. Multivariate analysis found that the TT/TT genotype of GNAQ was an independent risk factor for coronary artery stenosis requiring stent (hazard ratio, 4.5; p = 0.001), cardiovascular events (hazard ratio, 1.93; p = 0.04) and cardiovascular events affecting multiple organs (hazard ratio, 4.9; p = 0.03). In the subgroup of male patients left ventricular dilatation with abnormally increased LVEDD values occurred significantly more frequently in TT genotypes of GNB3 than in CT/CC genotypes (p = 0.007). Our findings suggest that male dialysis patients carrying the TT genotype of GNB3 are at higher risk of left ventricular dilatation and that dialysis patients carrying the TT/TT genotype of GNAQ are prone to coronary artery stenosis and severe cardiovascular events.

GNB3 c.825C>T (rs5443) Polymorphism and Risk of Acute Cardiovascular Events after Renal Allograft Transplant

The c.825C>T single-nucleotide polymorphism (rs5443) of the guanine nucleotide-binding protein subunit β3 (GNB3) results in increased intracellular signal transduction via G-proteins. The present study investigated the effect of the GNB3 c.825C>T polymorphism on cardiovascular events among renal allograft recipients posttransplant. Our retrospective study involved 436 renal allograft recipients who were followed up for up to 8 years after transplant. The GNB3 c.825C>T polymorphism was detected with restriction fragment length polymorphism (RFLP) polymerase chain reaction (PCR). The GNB3 TT genotype was detected in 43 (10%) of 436 recipients. Death due to an acute cardiovascular event occurred more frequently among recipients with the TT genotype (4 [9%]) than among those with the CC/CT genotypes (7 [2%]; p = 0.003). The rates of myocardial infarction (MI)−free survival (p = 0.003) and acute peripheral artery occlusive disease (PAOD)−free survival (p = 0.004) were significantly lower among T-homozygous patients. A multivariate analysis showed that homozygous GNB3 c.825C>T polymorphism exerted only a mild effect for the occurrence of myocardial infarction (relative risk, 2.2; p = 0.065) or acute PAOD (relative risk, 2.4; p = 0.05) after renal transplant. Our results suggest that the homozygous GNB3 T allele exerts noticeable effects on the risk of MI and acute PAOD only in the presence of additional nonheritable risk factors.

GWAS of longitudinal trajectories at biobank scale

Biobanks linked to massive, longitudinal electronic health record (EHR) data make numerous new genetic research questions feasible. One among these is the study of biomarker trajectories. For example, high blood pressure measurements over visits strongly predict stroke onset, and consistently high fasting glucose and Hb1Ac levels define diabetes. Recent research reveals that not only the mean level of biomarker trajectories but also their fluctuations, or within-subject (WS) variability, are risk factors for many diseases. Glycemic variation, for instance, is recently considered an important clinical metric in diabetes management. It is crucial to identify the genetic factors that shift the mean or alter the WS variability of a biomarker trajectory. Compared to traditional cross-sectional studies, trajectory analysis utilizes more data points and captures a complete picture of the impact of time-varying factors, including medication history and lifestyle. Currently, there are no efficient tools for genome-wide association studies (GWASs) of biomarker trajectories at the biobank scale, even for just mean effects. We propose TrajGWAS, a linear mixed effect model-based method for testing genetic effects that shift the mean or alter the WS variability of a biomarker trajectory. It is scalable to biobank data with 100,000 to 1,000,000 individuals and many longitudinal measurements and robust to distributional assumptions. Simulation studies corroborate that TrajGWAS controls the type I error rate and is powerful. Analysis of eleven biomarkers measured longitudinally and extracted from UK Biobank primary care data for more than 150,000 participants with 1,800,000 observations reveals loci that significantly alter the mean or WS variability.

Investigating the Relations Between Caffeine-Derived Metabolites and Plasma Lipids in 2 Population-Based Studies

OBJECTIVE

To investigate the relations between caffeine-derived metabolites (methylxanthines) and plasma lipids by use of population-based data from 2 European countries.

METHODS

Families were randomly selected from the general population of northern Belgium (FLEMENGHO), from August 12, 1985, until November 22, 1990, and 3 Swiss cities (SKIPOGH), from November 25, 2009, through April 4, 2013. We measured plasma concentrations (FLEMENGHO, SKIPOGH) and 24-hour urinary excretions (SKIPOGH) of 4 methylxanthines-caffeine, paraxanthine, theobromine, and theophylline-using ultra-high-performance liquid chromatography-tandem mass spectrometry. We used enzymatic methods to estimate total cholesterol, high-density lipoprotein cholesterol, and triglyceride levels and the Friedewald equation for low-density lipoprotein cholesterol levels in plasma. We applied sex-specific mixed models to investigate associations between methylxanthines and plasma lipids, adjusting for major confounders.

RESULTS

In both FLEMENGHO (N=1987; 1055 [53%] female participants) and SKIPOGH (N=990; 523 [53%] female participants), total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels increased across quartiles of plasma caffeine, paraxanthine, and theophylline (total cholesterol levels by caffeine quartiles in FLEMENGHO, male participants: 5.01±0.06 mmol/L, 5.05±0.06 mmol/L, 5.27±0.06 mmol/L, 5.62±0.06 mmol/L; female participants: 5.24±0.06 mmol/L, 5.15±0.05 mmol/L, 5.25±0.05 mmol/L, 5.42±0.05 mmol/L). Similar results were observed using urinary methylxanthines in SKIPOGH (total cholesterol levels by caffeine quartiles, male participants: 4.54±0.08 mmol/L, 4.94±0.08 mmol/L, 4.87±0.08 mmol/L, 5.27±0.09 mmol/L; female participants: 5.12±0.07 mmol/L, 5.21±0.07 mmol/L, 5.28±0.05 mmol/L, 5.28±0.07 mmol/L). Furthermore, urinary caffeine and theophylline were positively associated with high-density lipoprotein cholesterol in SKIPOGH male participants.

CONCLUSION

Plasma and urinary caffeine, paraxanthine, and theophylline were positively associated with plasma lipids, whereas the associations involving theobromine were less clear. We postulate that the positive association between caffeine intake and plasma lipids may be related to the sympathomimetic function of methylxanthines, mitigating the overall health-beneficial effect of caffeine intake.

Lack of association between the GNB3 rs5443, HIF1A rs11549465 polymorphisms, physiological and functional characteristics

The aim was to examine the association between the hypoxia-inducible factor-1α (HIF1A) gene and the guanine nucleotide binding protein beta polypeptide 3 (GNB3) gene polymorphisms and the endurance/power athlete status and relative aerobic capacity. Another goal of this study was to reveal the connection between GNB3, blood pressure (BP), body composition and body mass index (BMI). Two hundred thirty-eight people participated in this study: 148 elite athletes (men = 107, women = 41) and 90 controls (men = 51, women = 39). The athletes were divided into two groups: the power and the endurance athletes. BMI and body fat percentage (fat%) were calculated. Fifty of the athletes underwent an incremental treadmill test to exhaustion; BP was monitored before and after the test. There were differences in the genotype frequencies of HIF1A between the endurance and the control group (ProPro: 64% vs.79%, ProSer: 27% vs.19%, SerSer: 9% vs. 2%; p = .0351); in the allele prevalences among the three groups (Pro: 87% vs. 77% vs. 88%; Ser: 13% vs. 23% vs. 12%; p = .0103) and between the endurance and control group (p = .0049) as well. The GNB3 allele proportions differed in the three groups (C: 74% vs. 61% vs. 71%, T: 26% vs. 39% vs. 29%; p = .0436). There were no connections between the genotypes and the relative aerobic capacity and neither between GNB3 genotypes and BP, BMI and fat%. The connection of GNB3 T allele to the endurance performance still remained contradictable.

The relationship among GNB3 rs5443, PNPLA3 rs738409, GCKR rs780094 gene polymorphisms, type of maternal gestational weight gain and neonatal outcomes (STROBE-compliant article)

The gestational weight gain is determined by food habits, environmental and genetic factors.The aims of this paper were to establish relationships between maternal gene polymorphisms (patatin-like phospholipase domain-containing protein 3 rs738409 [PNPLA3 rs738409], glucokinase regulatory protein rs780094 [GCKR rs780094], and guanine nucleotide-binding protein rs5443 [GNB3 rs5443]) and mothers' gestational weight gain, but also neonatal outcomes (birth weight, length, and ponderal index [PI]).We performed a cross-sectional study in a sample of 158 mothers and their product of conception' in an Obstetrics-Gynecology Clinic from Romania. We divided the pregnant women according to the Institute of Medicine recommendations into 3 subgroups: (1) insufficient gestational weight gain; (2) normal gestational weight gain; and (3) excessive gestational weight gain.The gestational weight gain among pregnant women included in this study was classified as insufficient (10.1%), normal (31%), and excessive (58.9%). We found a tendency towards statistical significance for mothers that were overweight or obese before pregnancy to present an excessive gestational weight gain as compared to the normal weight ones. Similarly, we identified a tendency for statistical significance regarding the association between the variant genotype of GNB3 rs5443 and excessive gestational weight gain. We noticed differences that tended to be statistical significant concerning aspartate aminotransferase values between the 3 subgroups, mothers with excessive gestational weight gain having higher values than mothers with normal gestational weight gain (median, IQR: 22.89[17.53; 31.59] for mothers with excessive gestational weight gain versus 22.71[18.58; 27.37] for mothers with normal gestational weight gain). In mothers with excessive gestational weight gain, we found a significant association between the variant genotype of PNPLA3 rs738409 polymorphism and neonatal PI noticing a decrease of this index in case of newborns from mothers carrying the variant genotype.Excessive gestational weight gain was noticed in pregnant women that were obese and overweight before pregnancy. We found a positive association between the variant genotype of GNB3 rs5443 polymorphism and excessive gestational weight gain. Similarly, the presence of variant genotype of PNPLA3 rs738409 in mothers was associated with a lower PI in their newborns. Our study pointed out the most important factors that influence gestational weight gain and related birth outcomes.

A method to account for covariate-specific treatment effects when estimating biomarker associations in the presence of endogenous medication use

In the modern era, cardiovascular biomarkers are often measured in the presence of medication use, such that the observed biomarker value for the treated participants is different than their underlying natural history value. However, for certain predictors (e.g. age, gender, and genetic exposures) the observed biomarker value is not of primary interest. Rather, we are interested in estimating the association between these predictors and the natural history of the biomarker that would have occurred in the absence of treatment. Nonrandom medication use obscures our ability to estimate this association in cross-sectional observational data. Structural equation methodology (e.g. the treatment effects model), while historically used to estimate treatment effects, has been previously shown to be a reasonable way to correct endogeneity bias when estimating natural biomarker associations. However, the assumption that the effects of medication use on the biomarker are uniform across participants on medication is generally not thought to be reasonable. We derive an extension of the treatment effects model to accommodate effect modification. Based on several simulation studies and an application to data from the Multi-Ethnic Study of Atherosclerosis, we show that our extension substantially improves bias in estimating associations of interest, particularly when effect modifiers are associated with the biomarker or with medication use, without a meaningful cost of efficiency.

Cardiovascular diseases-related GNB3 C825T polymorphism has a significant sex-specific effect on serum soluble E-selectin levels

Background

The C825T polymorphism (rs5443) of the Guanine Nucleotide-Binding protein subunit β3 (GNB3) gene has been associated with obesity, essential hypertension, atherosclerosis, coronary diseases, and cerebrovascular events, but with some sex-specific effects. Its association with inflammatory mediators such as cell adhesion molecules has not been studied, although they are heavily involved in cardiovascular diseases’ (CVDs) processes. The aim of our study was then to investigate a possible sex-specific effect of the GNB3 C825T polymorphism on serum soluble cell adhesion molecules such as E, P and L-selectins (sE, sP and sL-selectins).

Results

Participants were from the STANISLAS Family Study and were free of chronic disease as CVDs or cancer. We included in total 771 subjects aged 6 to 58 years (391 males (50.71%) and 380 females (49.29%)). No significant association of rs5443 was observed in the whole population with serum sE, sP and sL-selectins after adjusting for age, sex, body mass index, systolic blood pressure, anti-inflammatory drugs and hormonal drugs consumption. A significant interaction of rs5443 was observed with sex for sE-selectin (p < 0.001), but not for sP and sL-selectins. After adjusting for covariables, the T allele was significantly associated with an additive increase effect on serum sE-selectin levels in males (β = 5.03 ± 2.18; p = 0.020), while a significant additive decrease effect was observed in females (β =−4.46 ± 2.06; p = 0.030). These associations stayed significant after correction for multiple tests (p = 0.045 in males and in females). The additive phenotypic variance was 21.54% in males versus 1.91% in females.

Conclusions

In our Caucasian population, the GNB3 C825T polymorphism showed a significant sex-specific effect on serum sE-selectin levels, with a disadvantage for males, as increased sE-selectin levels has been associated with CVDs outcomes. The T allele has been previously associated with the same CVDs as increased sE-selectin, but more often in males. The link we observed between this polymorphism and E-selectin is then consistent with previous findings, and helps to better understand the deleterious effect of the GNB3 825 T allele on CVDs outcomes in males. We revealed in this study an important pathway through which the GNB3 gene induces CVDs’ outcomes.

A longitudinal study of the association between the GNB3 C825T polymorphism and metabolic disturbance in bipolar II patients treated with valproate

This longitudinal study aimed to investigate the associations between the polymorphisms of guanine nucleotide-binding protein subunit β-3 (GNB3) C825T and metabolic disturbance in bipolar II disorder (BP-II) patients being treated with valproate (VPA). A 100 BP-II patients received a 12-week course of VPA treatment, and their body weight and metabolic indices were measured. At baseline, the GNB3 C825T polymorphisms were associated with the triglyceride level (P=0.032) in BP-II patients. During the VPA treatment course, the polymorphisms were not only associated with body mass index (BMI) and waist circumference (P-values=0.009 and 0.001, respectively), but also with total cholesterol, triglyceride, low-density lipoprotein and leptin levels (P-values=0.004, 0.002, 0.031 and 0.015, respectively). Patients with the TT genotype had a lower BMI, smaller waist circumference, and lower levels of lipids and leptin than those with the CT or CC genotypes undergoing the VPA treatment course.

Evaluating the treatment effects model for estimation of cross-sectional associations between risk factors and cardiovascular biomarkers influenced by medication use

PURPOSE

In cross-sectional observational data, evaluation of biomarker-to-exposure associations is often complicated by nonrandom medication use. Traditional approaches often lead to biased estimates, consistent with known results involving confounding by indication. More sophisticated, yet easy to implement approaches such as inverse probability weighting and censored normal regression can address medication use in certain settings but have poor performance when medication use depends on off-medication biomarker values. More sophisticated approaches are necessary.

METHODS

Heckman's treatment effects model resembles the process that gives rise to cross-sectional data. In this study, we conduct a variety of simulation studies to illustrate why traditional approaches are inappropriate when medication use depends on underlying biomarker values. We illustrate how Heckman's model can accommodate this feature. We also apply the models to data from the Multi-Ethnic Study of Atherosclerosis.

RESULTS

Inverse probability weighting and censored normal regression are sensitive to how strongly medication use is associated with untreated biomarker values (the untreated value acts as an unmeasured predictor of medication use in this context). Heckman's model can often adequately remove bias and is robust to certain forms of model misspecification but relies on knowing important predictors of medication use, even when they are independent of the biomarker. The advantages of Heckman's model can be negated if the effect of medication on biomarker values is proportionate to the underlying biomarker.

CONCLUSIONS

If predictors of medication use are measured, data are cross-sectional, and effects are approximately additive, then Heckman's model is more accurate relative to alternative approaches.

[Genetic aspects of erectile dysfunction]

BACKGROUND

Erectile dysfunction (ED) is a common disorder in man that influences the quality of life of the patient and his partner. Known risk factors for ED comprise diabetes, coronary artery disease, hypertension but also lifestyle modifications such as smoking, diminished physical activity as well as obesity. In this manuscript the current scientific literature about genetics and erectile dysfunction is reviewed.

MATERIALS AND METHODS

A literature search using the databank PubMed covering the topics genetics and erectile dysfunction was performed and relevant papers selected for presentation.

RESULTS

Several aspects of genetics and ED are described in the current literature. Association studies of candidate polymorphisms and ED risk in comparison to healthy controls is a major area of research. Another topic is the genome-wide search for candidate polymorphisms with erectile dysfunction. The paper closes with the presentation of the pharmacogenomic analysis of treatment response to phosphodiesterase-5 inhibitors.

DISCUSSION

The heterogeneous results of genetic association studies are possibly due to small sample sizes of the study population and/or due to ethnic differences of the analyzed populations. This underlines the need for validation of this data in larger prospective multinational multicenter studies.

G-Protein β3-Subunit Gene C825T Polymorphism and Cardiovascular Risk: An Updated Review

Hypertension is a common disorder of multifactorial origin that constitutes a major risk factor for cardiovascular events such as stroke and myocardial infarction. The subunits of the heterotrimeric G proteins are attractive candidate gene products for susceptibility to hypertension, obesity and insulin resistance syndrome. A polymorphism (825C/T) in exon 10 of the GNB3 gene, encoding for the Gβ3 subunit, has been described. The 825T allele is associated with alternative splicing of the gene and formation of a truncated but functionally active β3 subunit. Many studies have investigated whether carriers of the 825T allele are at increased risk for hypertension, obesity, insulin-resistance and left ventricular hypertrophy with apparently conflicting results. The present review demonstrates that GNB3 825T allele is a useful genetic marker for better defining the risk profile of hypertensive patients, as it is associated with increased risk of stroke and myocardial infarction in longitudinal studies in Caucasians.

GNB3 gene 825 TT variant predicts hard coronary events in the population-based Heinz Nixdorf Recall study

OBJECTIVE

The C825T polymorphism of the gene encoding the human G protein beta-3 subunit (GNB3) is associated with hypertension and obesity. Moreover, genotypes of the GNB3 polymorphism have been associated with development of coronary artery disease, and the 825T allele is thought to influence the process of atherosclerosis. However, the potential of the C825T polymorphism to predict coronary events has been poorly explored in a longitudinal setting at the population level.

METHODS

In 4159 Caucasian subjects from the Heinz Nixdorf Recall study cohort (age: 45-75 years, 48% male), genotypes of the GNB3 C825T polymorphism (rs5443) were determined and associated with fatal and non-fatal myocardial infarction (hard coronary events). Established cardiovascular risk factors were used to adjust for confounders.

RESULTS

The median follow-up time was 9.9 years (1st/3rd quartiles 9.5/10.2). 148 subjects (3.6%) experienced a hard coronary event. The 10-year event-free survival rate was CC, 96.1%; CT 96.9%, TT, 93.7% (p = 0.018). Multivariable analysis showed that the TT genotype is a significant risk factor for hard coronary events (hazard ratio (HR) = 1.9 (95% confidence interval (CI) 1.2-2.9); p = 0.008) after adjustment for age, sex, diabetes, systolic blood pressure, body mass index, high-density lipoprotein, and coronary artery calcification as determined by electron beam computed tomography at baseline. While prognosis in females was independent of GNB3 genotypes, analysis in males even elevated the HR for TT versus C-allele to 2.6 (95% CI 1.6-4.2; p < 0.001).

CONCLUSION

The GNB3 825 TT genotype is a significant and independent risk factor for hard coronary events independent of other established cardiovascular risk factors at a population level in males.

Imputing observed blood pressure for antihypertensive treatment: impact on population and genetic analyses

BACKGROUND

Elevated blood pressure (BP), a heritable risk factor for many age-related disorders, is commonly investigated in population and genetic studies, but antihypertensive use can confound study results. Routine methods to adjust for antihypertensives may not sufficiently account for newer treatment protocols (i.e., combination or multiple drug therapy) found in contemporary cohorts.

METHODS

We refined an existing method to impute unmedicated BP in individuals on antihypertensives by incorporating new treatment trends. We assessed BP and antihypertensive use in male twins (n = 1,237) from the Vietnam Era Twin Study of Aging: 36% reported antihypertensive use; 52% of those treated were on multiple drugs.

RESULTS

Estimated heritability was 0.43 (95% confidence interval (CI) = 0.20-0.50) and 0.44 (95% CI = 0.22-0.61) for measured systolic BP (SBP) and diastolic BP (DBP), respectively. We imputed BP for antihypertensives by 3 approaches: (i) addition of a fixed value of 10/5mm Hg to measured SBP/DBP; (ii) incremented addition of mm Hg to BP based on number of medications; and (iii) a refined approach adding mm Hg based on antihypertensive drug class and ethnicity. The imputations did not significantly affect estimated heritability of BP. However, use of our most refined imputation method and other methods resulted in significantly increased phenotypic correlations between BP and body mass index, a trait known to be correlated with BP.

CONCLUSIONS

This study highlights the potential usefulness of applying a representative adjustment for medication use, such as by considering drug class, ethnicity, and the combination of drugs when assessing the relationship between BP and risk factors.

The AGT and the GNB3 polymorphisms and insulin resistance in prehypertension

OBJECTIVE

This study surveyed the frequencies of single nucleotide polymorphisms (SNPs) M235T AGT and C825T GNB3, and their association with insulin resistance, other biochemical markers and qualitative variables in subjects with high normal blood pressure and/or prehypertension in the Greek population.

DESIGN

330 men and women of Greek origin were divided into 3 groups: a) hypertensive, b) prehypertensive and c) control group. These groups were genetically tested for these polymorphisms and insulin resistance with the HOMA index.

RESULTS

No statistically significant differences were found among the polymorphisms of the compared groups. However, the ? allele carriers (CT/TT vs. CC) of the C825T polymorphism were associated with an increased BMI in all 3 groups (p=0.004). The HOMA index was higher in the hypertensive (p=0.006) and prehypertensive (p=0.016) versus the control group, and similar results were found for insulin (hypertensive vs. control p=0.012, prehypertensive vs. control p=0.001) without statistical significance between the first 2 groups (p=0.522). Additionally, there was a statistically significant difference between the control group and the hypertensive and prehypertensive groups regarding cholesterol (control vs. hypertensive p=0.001, control vs. prehypertension p=0.018) and triglycerides (control vs. hypertensive p=0.0001, control vs. prehypertension p=0.007). Differences were also noted between the control and the hypertensive group regarding the value of HDL (p=0.005) and LDL (p=0.013).

CONCLUSION

This study failed to demonstrate a correlation between specific SNPs, blood pressure and insulin resistance in the 3 groups. However, T allele carriers of the polymorphism C825T were found to have an increased BMI. Similarly, increased insulin resistance and lipidemia were more common in the hypertensive and prehypertensive populations.

Methods for a longitudinal quantitative outcome with a multivariate Gaussian distribution multi-dimensionally censored by therapeutic intervention

In longitudinal studies, a quantitative outcome (such as blood pressure) may be altered during follow-up by the administration of a non-randomized, non-trial intervention (such as anti-hypertensive medication) that may seriously bias the study results. Current methods mainly address this issue for cross-sectional studies. For longitudinal data, the current methods are either restricted to a specific longitudinal data structure or are valid only under special circumstances. We propose two new methods for estimation of covariate effects on the underlying (untreated) general longitudinal outcomes: a single imputation method employing a modified expectation-maximization (EM)-type algorithm and a multiple imputation (MI) method utilizing a modified Monte Carlo EM-MI algorithm. Each method can be implemented as one-step, two-step, and full-iteration algorithms. They combine the advantages of the current statistical methods while reducing their restrictive assumptions and generalizing them to realistic scenarios. The proposed methods replace intractable numerical integration of a multi-dimensionally censored MVN posterior distribution with a simplified, sufficiently accurate approximation. It is particularly attractive when outcomes reach a plateau after intervention due to various reasons. Methods are studied via simulation and applied to data from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications study of treatment for type 1 diabetes. Methods proved to be robust to high dimensions, large amounts of censored data, low within-subject correlation, and when subjects receive non-trial intervention to treat the underlying condition only (with high Y), or for treatment in the majority of subjects (with high Y) in combination with prevention for a small fraction of subjects (with normal Y).

Cognitive Functions across the GNB3 C825T Polymorphism in an Elderly Italian Population

To verify whether the C825T polymorphism of the GNB3 influences the response to neuropsychological tests, mini-mental state examination, digit span (DS), immediate and delayed prose memory, memory with interference at 10 and 30 seconds (MI 10 and 30), trail making tests (TMTs) A and B, abstraction task, verbal fluency (VF) test, figure drawing and copying, overlapping figures test and clock test were performed in 220 elderly men and women free from clinical dementia and from neurological and psychiatric diseases randomly taken from the Italian general population and analysed across the C825T polymorphism. The performance of DS, immediate and delayed prose memory, VF, and TMTs was worse in subjects who were TT for the polymorphism in comparison to the C-carriers. The performance of all tests declined with age. In the case of DS, immediate and delayed prose memory, MI 10 and VF, this trend was maintained in the C-carriers but not in TT. In the case of prose memory, of memory with interference, and of VF, schooling reduced the detrimental interaction between age and genotype. The C825T polymorphism of GNB3 gene therefore influences memory and verbal fluency, being additive to the effects of age and partially mitigated by schooling.

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.

Common genetic variants in ARNTL and NPAS2 and at chromosome 12p13 are associated with objectively measured sleep traits in the elderly

STUDY OBJECTIVES

To determine the association between common genetic variation in the clock gene pathway and objectively measured acti-graphic sleep and activity rhythm traits.

DESIGN

Genetic association study in two population-based cohorts of elderly participants: the Study of Osteoporotic Fractures (SOF) and the Osteoporotic Fractures in Men (MrOS) study.

SETTING

Population-based.

PARTICIPANTS

SOF participants (n = 1,407, 100% female, mean age 84 years) and MrOS participants (n = 2,527, 100% male, mean age 77 years) with actigraphy and genotype data.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Common genetic variation in 30 candidate genes was captured using 529 single nucleotide polymorphisms (SNPs). Sleep and activity rhythm traits were objectively measured using wrist actigraphy. In a region of high linkage disequilibrium on chromosome 12p13 containing the candidate gene GNB3, the rs1047776 A allele and the rs2238114 C allele were significantly associated with higher wake after sleep onset (meta-analysis: rs1047776 PADD = 2 × 10(-5), rs2238114 PADD = 5 × 10(-5)) and lower LRRC23 gene expression (rs1047776: ρ = -0.22, P = 0.02; rs2238114: ρ = -0.50, P = 5 × 10(-8)). In MrOS participants, SNPs in ARNTL and NPAS2, genes coding for binding partners, were associated with later sleep and wake onset time (sleep onset time: ARNTL rs3816358 P2DF = 1 × 10(-4), NPAS2 rs3768984 P2DF = 5 × 10(-5); wake onset time: rs3816358 P2DF = 3 × 10(-3), rs3768984 P2DF = 2 × 10(-4)) and the SNP interaction was significant (sleep onset time PINT = 0.003, wake onset time PINT = 0.001). A SNP association in the CLOCK gene replicated in the MrOS cohort, and rs3768984 was associated with sleep duration in a previously reported study. Cluster analysis identified four clusters of genetic associations.

CONCLUSIONS

These findings support a role for common genetic variation in clock genes in the regulation of inter-related sleep traits in the elderly.

CITATION

Evans DS; Parimi N; Nievergelt CM; Blackwell T; Redline S; Ancoli-Israel S; Orwoll ES; Cummings SR; Stone KL; Tranah GJ. Common genetic variants in ARNTL and NPAS2 and at chromosome 12p13 are associated with objectively measured sleep traits in the elderly. SLEEP 2013;36(3):431-446.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

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.

Pilot genome-wide association search identifies potential loci for risk of erectile dysfunction in type 1 diabetes using the DCCT/EDIC study cohort

PURPOSE

We identified genetic predictors of diabetes associated erectile dysfunction using genome-wide and candidate gene approaches in a cohort of men with type 1 diabetes.

MATERIALS AND METHODS

We examined 528 white men with type 1 diabetes, including 125 with erectile dysfunction, from DCCT (Diabetes Control and Complications Trial) and its observational followup, the EDIC (Epidemiology of Diabetes Interventions and Complications) study. Erectile dysfunction was identified from a single International Index of Erectile Function item. A Human1M BeadChip (Illumina®) was used for genotyping. A total of 867,125 single nucleotide polymorphisms were subjected to analysis. Whole genome and candidate gene approaches were used to test the hypothesis that genetic polymorphisms may predispose men with type 1 diabetes to erectile dysfunction. Univariate and multivariate models were used, controlling for age, HbA1c, diabetes duration and prior randomization to intensive or conventional insulin therapy during DCCT. A stratified false discovery rate was used to perform the candidate gene approach.

RESULTS

Two single nucleotide polymorphisms located on chromosome 3 in 1 genomic loci were associated with erectile dysfunction with p <1 × 10(-6), including rs9810233 with p = 7 × 10(-7) and rs1920201 with p = 9 ×10(-7). The nearest gene to these 2 single nucleotide polymorphisms is ALCAM. Genetic association results at these loci were similar on univariate and multivariate analysis. No candidate genes met the criteria for statistical significance.

CONCLUSIONS

Two single nucleotide polymorphisms, rs9810233 and rs1920101, which are 25 kb apart, are associated with erectile dysfunction, although they do not meet the standard genome-wide association study significance criterion of p <5 × 10(-8). Other studies with larger sample sizes are required to determine whether ALCAM represents a novel gene in the pathogenesis of diabetes associated erectile dysfunction.

Association of the C825T polymorphism in the GNB3 gene with obesity and metabolic phenotypes in a Taiwanese population

The relationship between obesity and a single nucleotide polymorphism (SNP), rs5443 (C825T), in the guanine nucleotide binding protein beta polypeptide 3 (GNB3) gene is currently inconsistent. In this study, we aimed to reassess whether the GNB3 rs5443 SNP could influence obesity and obesity-related metabolic traits in a Taiwanese population. A total of 983 Taiwanese subjects with general health examinations were genotyped. Based on the criteria defined by the Department of Health in Taiwan, the terms "overweight" and "obesity" are defined as 24 ≦ BMI < 27 and BMI ≧ 27, respectively. Compared to the carrier of the combined CT + TT genotypes of the GNB3 rs5443 polymorphism, triglyceride was significantly higher for the carrier of CC genotype in the complete sample population (128.2 ± 93.2 vs. 114.3 ± 79.1 mg/dl; P = 0.041). In addition, the carriers of CC variant had a higher total cholesterol than those with the combined CT + TT variants (194.5 ± 36.8 vs. 187.9 ± 33.0 mg/dl; P = 0.019) in the complete sample population. In the normal controls, both triglyceride (P = 0.018) and total cholesterol (P = 0.011) were also significantly higher in the CC homozygotes than in the combined CT + TT genotypes. However, the GNB3 rs5443 SNP did not exhibit any significant association with obesity or overweight among the subjects. Our study indicates that the CC genotype of the GNB3 rs5443 SNP may predict higher obesity-related metabolic traits such as triglyceride and total cholesterol in non-obese Taiwanese subjects (but not in obese subjects).

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.

The GNB3 C825T polymorphism as a pharmacogenetic marker in the treatment of hypertension, obesity, and depression

Heterotrimeric guanine-binding proteins (G proteins) transmit signals from the cell surface to intracellular signal cascades. The β3-subunit encoded by the gene GNB3 is widely expressed and, therefore, involved in various physiological and pathophysiological processes. A C825T polymorphism located in exon 10 of GNB3 was described in 1998 and the T allele was associated with alternative splicing and with increased signal transduction in human cells and tissues. In several disease-association studies, the 825T allele could be linked to hypertension, obesity, and depression. Meta-analysis available for hypertension and depression confirmed association with these phenotypes. On the basis of these findings, subsequent studies investigated whether the C825T polymorphism serves as a pharmacogenetic marker. Most pharmacogenetic investigations have focused on the treatment of hypertension, obesity, and depression. In this study, we will comprehensively describe and discuss these studies.

Clinically silent adrenal adenomas - their relation to the metabolic syndrome and to GNB3 C825T gene polymorphism

OBJECTIVES

Aim of the study was to assess the prevalence of C825T GNB3 gene polymorphism in patients with adrenal incidentaloma (AI) as well as its relation to the metabolic syndrome (MS) and cortisol status.

SUBJECT AND METHODS

Alltogether 82 subjects (50 patients with AI, mean age 57.9 + 15 years and 32 subjects without AI, mean age 53.8 + 6.9 years) were included in this study. Parameters of glucose and lipid metabolism, serum adiponectin and the single nucleotide polymorphism C825T in GNB3 gene using PCR-RFLP method were examined. To detect subclinical Cushing syndrome an overnight dexamethason test was performed in all patients with AI.

RESULTS

Patients with AI had signifcantly higher BMI, HOMA, triacylglycerols (p < 0.05) and significantly lower serum adiponectine (p < 0.05) than controls. There were no significant differences in metabolic parameters between group with and without subclinical Cushing syndrome (SCS). The prevalence of T allele of GNB3 gene in patients with AI was not significantly higher as compared with control group (32% vs. 47%). No significant differences in serum glucose and lipids between carriers of T and C alleles were detected. However carriers of T allele had significantly lower serum adiponectin than those with allele C (p < 0.01).

CONCLUSION

We conclude that patients with AI had significantly higher cardiovascular risk factors that is not related to the presence of SCS. Moreover patients with AI and TC or TT genotype have significantly lower serum adiponectin which may be an early symptom of metabolic syndrome in patients with AI.

SNPs in genes encoding G proteins in pharmacogenetics

Heterotrimeric guanine-binding proteins (G proteins) transmit signals from the cell surface to intracellular signal cascades and are involved in various physiological and pathophysiological processes. Polymorphisms in the genes GNB3 (encoding the Gβ3 subunit), GNAS (encoding the Gαs subunit) and GNAQ (encoding the Gαq subunit) have been the primary focus of investigation. Polymorphisms in these genes could be associated with different complex phenotypes underlining that alterations in G-protein signaling can cause multiple disorders. G proteins present a point of convergence or ‘bottleneck’ between various receptors and effectors, thus making them a sensible tool for pharmacogenetic studies. The pharmacogenetic studies performed to date mostly demonstrate an association between G-protein polymorphisms and response to therapy or occurrence of adverse drug effects. Therefore, polymorphisms in genes encoding G-protein subunits may help to individualize drug treatment in various diseases with regard to both efficacy and safety.

Pharmacogenetic interactions and their potential effects on genetic analyses of blood pressure

BACKGROUND

In observational studies, analyses of blood pressure (BP) typically require some correction for the use of antihypertensive medications by study participants. Different approaches to correcting for treatment have been compared, but the impact of pharmacogenetic interactions that influence the efficacy of antihypertensive treatments on estimates of genetic main effects has not been considered. This work demonstrates the potential influence of pharmacogenetic interactions in genetic analyses of BP.

METHODS

A simulation study is conducted to test the influence of pharmacogenetic interactions on approaches to the analysis of BP. Results from three plausible scenarios are presented.

RESULTS

Informative BP approaches (Fixed Treatment Effect, Non-parametric adjustment, Censored Normal Regression) perform well when there is no pharmacogenetic interaction, but yield biased estimates of the main effects of particular genetic variants when pharmacogenetic interactions exist. Substitution approaches (Binary Trait, Fixed Substitution, Random Substitution, Median Method) are unaffected by pharmacogenetic interactions, but consistently perform sub-optimally.

CONCLUSIONS

We recommend that the Informative BP approaches remain the most appropriate methods to use in practice, but stress that caution is required in the interpretation of their results-especially when an interaction between treatment and a genetic variant of interest is suspected. We make some suggestions as to how to check for possible interactions and confirm the results from genetic analyses of BP, but warn that these should be reviewed when data on real pharmacogenetic interactions become available.

Association between the G protein β3 subunit C825T polymorphism and the occurrence of cardiovascular disease in hypertensives: The Nord-Trøndelag Health Study (HUNT)

BACKGROUND

Several studies examining the C825T polymorphism of the G protein β3 subunit (GNB3) have shown inconsistent results regarding susceptibility to hypertension. With twice the length of earlier studies, the aim of our study was to further investigate this association with a cross-sectional design over an 11.5-year follow-up period in a Norwegian population.

METHODS

Two randomized selected population samples from the Nord-Trøndelag Health Study 1995-1997 (HUNT 2) were genotyped. One sample included individuals reporting use of antihypertensive medication (n = 969), and the other did not report use of antihypertensive medication, cardiovascular disease (CVD), or diabetes (n = 1,867). Of those genotyped, 2,254 participants (79.5%) also attended HUNT 1 in 1984-1986.

RESULTS

There was no significant higher prevalence of hypertension (blood pressure ≥140/90 mm Hg and/or antihypertensive medication) in T-allele carriers than in C allele carriers. However, TT homozygous men with treated hypertension showed statistical significant association with self-reported CVD compared to the CC genotype (odds ratio (OR) 3.19, P = 0.001). No statistical significant association between hypertension and the C825T polymorphism was found during the follow-up.

CONCLUSIONS

No association was found between the C285T polymorphism of the GNB3 and hypertension. However, CVD was more common among treated hypertensive men with the TT genotype compared to men with the CC genotype. Thus, further studies are needed to explore whether this finding could be caused by other mechanisms than elevated blood pressure.

C825T polymorphism of the GNB3 gene on valproate-related metabolic abnormalities in bipolar disorder patients

BACKGROUND

Valproate (VPA) is a mood stabilizer for treating patients with bipolar disorder (BD). It may cause metabolic abnormalities in certain bipolar patients. However, the genetic factors that influence the susceptibility remain unclear. Genetic polymorphism of the G-protein β3 subunit (GNB3) is reported to be associated with metabolic phenotypes. In the current study, we investigated the possible associations between the GNB3 variation and VPA-induced metabolic abnormalities.

METHODS

Subjects (n = 96) who met the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for BD were recruited from the National Cheng Kung University Hospital. Their metabolic indices were measured.

RESULTS

The variation of GNB3 C825T showed an association with higher plasma total cholesterol (P = 0.037), triglyceride (P = 0.014), and leptin (P < 0.001) levels in BD patients treated with VPA. After adjusting for age, sex, types of BDs, and serum concentration of VPA, the variation of GNB3 C825T remained significantly associated with the levels of serum leptin and body mass index (BMI; P < 0.001 and P = 0.030, respectively). In addition, the GNB3 C825T showed significant drug-single-nucleotide polymorphism interactions with insulin levels (P = 0.033), triglyceride levels (P = 0.013), leptin levels (P = 0.013), and BMI (P = 0.018). These results indicated that the T allele may be associated with lower serum leptin levels and BMI in BD patients treated with VPA.

CONCLUSIONS

The current study provides evidence that BD patients who are T allele carriers of the GNB3 C825T polymorphism have a lower risk for VPA-induced metabolic abnormalities. Further studies about the underlying mechanisms of G protein in VPA-induced metabolic abnormalities are warranted.

Association of antipsychotic induced weight gain and body mass index with GNB3 gene: a meta-analysis

It has been reported that C825T variant in the gene encoding the G-protein subunit beta3 (GNB3) is associated with antipsychotic-induced weight gain and obesity. We investigated the association of the GNB3 and antipsychotic-induced weight gain as well as body mass index (BMI) using meta-analytical techniques. Our analysis of 402 schizophrenia subjects showed a trend (p=0.072) only under a fixed-model. As it was observed heterogeneity among the studies (p=0.007), we re-analyzed using a random-effects framework and no significance was found (p=0.339). No evidence for bias publication was reported (p=0.868). Our analysis of 18,903 subjects showed a trend (p=0.053) associating CC and lower BMI under a fixed model. Although no significant association was found, the same pattern (CC and lower antipsychotic-induced weight gain) was observed. Our meta-analysis indicates that firmly establishing the role of pharmacogenetics in clinical psychiatry requires much larger sample sizes that have been reported.

Association of insulin sensitivity and glucose tolerance with the c.825C>T variant of the G protein beta-3 subunit gene

The risk of macrovascular complications of diabetes mellitus is greatly enhanced by the presence of high blood pressure. In addition, hypertension and diabetes share insulin resistance as a common pathophysiological mechanism. Despite evidence for a common molecular genetic background of insulin resistance, glucose intolerance, and hypertension, few candidate genes have been shown to influence all of these features simultaneously. We examined the association of insulin sensitivity with the c.825C>T variant of the g-protein beta-3 subunit (GNB3), a candidate gene of hypertension, in families of Mexican-American hypertensive patients.

METHODS

One hundred eighty subjects enrolled in a family study of Mexican-American hypertensive patients were recruited from hypertension clinics in Los Angeles. Subjects underwent pretreatment blood pressure recording, an oral glucose tolerance test, euglycemic hyperinsulinemic clamp, and anthropometric measurements. DNA from peripheral blood leukocytes was genotyped by polymerase chain reaction and restriction enzyme digest with BseD1 (GNB). Statistical analysis was performed by transmission disequilibrium testing.

RESULTS

In carriers of the T-allele, blood glucose was significantly lower [(mean+S.D.) fasting: 96.7+22.9 vs. 106.7+51.7mg/dl, P=.009; oral glucose tolerance test (oGTT) 120 min: 131.7+48.7 vs. 137.8+64.9 mg/dl, P=.036], and insulin sensitivity was significantly higher (229.0+108.7 vs. 188.5+94.2 mg/kg per minute, P=.037) than in homozygous carriers of the C-allele. Blood pressure did not differ significantly between the phenotypes.

CONCLUSION

In a Mexican-American hypertensive population, we found evidence for higher insulin sensitivity in carriers of the T allele of the c.825C>T variant of GNB3.

No evidence for association between BMI and 10 candidate genes at ages 4, 7 and 10 in a large UK sample of twins

Background

Over the last decade, associations between Body Mass Index (BMI) and a variety of candidate genes have been reported, but samples have almost all been limited to adults. The purpose of the present study was to test the developmental origins of some of these associations in a large longitudinal sample of children.

Methods

For 10 single-nucleotide polymorphisms (SNPs) in candidate genes reported to be associated with BMI in adults, we examined associations with BMI in a sample of 5000 children (2500 twin pairs) with BMI data at 4, 7 and 10 years. Association analyses were performed using the Quantitative Transmission Disequilibrium Test and we corrected for multiple testing using the False Discovery Rate.

Results

Despite having 80% power to detect associations that account for as little as 0.2% of the variance of BMI, none of the 10 SNPs were significantly associated with BMI at any age, although two SNPs showed trends in the expected direction.

Conclusion

The lack of association for these ten previously reported associations, despite our large sample size, is typical of associations between candidate genes and complex traits. However, some of the reported SNP associations with BMI might emerge as we continue to follow the sample into adolescence and adulthood. This report highlights the importance of developmentally appropriate candidate genes.

Obesity and polymorphisms in genes regulating human adipose tissue

Obesity is the result of an imbalance between food intake and energy expenditure resulting in the storing of energy as fat. Adipose tissue contains the largest store of energy in the body and plays important roles in regulating energy partitioning. Developments in genomics, in particular microarray-based expression profiling, have provided scientists with a number of new candidate genes whose expression in adipose tissue is regulated by obesity. Integrating expression profiles with genome-wide linkage and/or association analyses is a promising strategy to identify new genes underlying susceptibility to obesity. This article provides a comprehensive review of adipose-tissue-expressed genes implicated in predisposition to human obesity. The authors consider the following genes of particular interest: peroxisome proliferator-activated receptor gamma and, potentially, INSIG2 acting in adipogenesis; the adrenoreceptors beta 2 and 3, as well as hormone-sensitive lipase acting on lipolysis; uncoupling protein 2 acting in mitochondria energy expenditure; and among secreted molecules the cytokine tumor necrosis factor alpha and the hormone leptin. With the rapid development in genome research, we predict that additional alleles in genes regulating adipose tissue function will be established as risk factors for common obesity in the coming years. This has important implications for the prevention of obesity and may also offer new therapeutic targets.

-391 C to G substitution in the regulator of G-protein signalling-2 promoter increases susceptibility to the metabolic syndrome in white European men: consistency between molecular and epidemiological studies

BACKGROUND

The regulator of G-protein signalling-2 (RGS2) is a key factor in adipogenesis. We hypothesized that the metabolic syndrome, of which obesity is an important component, might be related to genetic variation in RGS2.

METHODS AND RESULTS

We screened the human RGS2 gene. We tested the functionality of a common genetic variant in vitro, ex vivo, and in epidemiological study involving six European populations. The C to G substitution at position -391 in the RGS2 promoter was associated with enhanced RGS2 expression in vitro in transfected 3T3-L1 adipocytes and Chinese hamster cells and ex vivo in adipocytes from male, but not female, volunteers. In 2732 relatives from 512 families and 348 unrelated individuals, randomly recruited from six European populations, the prevalence of GG homozygosity was 54.1%. The metabolic syndrome score, a composite of six continuous traits making up this clinical entity, was 0.27 standardized units higher (P < 0.001) in 795 GG homozygous men compared with 683 men carrying the C allele. Transmission of the -391 G allele to male offspring was associated with a 0.20 unit increase in the score (P=0.039). These epidemiological relations were not significant in 1602 women.

CONCLUSIONS

The C to G substitution at position -391 in the RGS2 promoter increases RGS2 expression in adipocytes and is associated with the metabolic syndrome in white European men. Further experimental and clinical research should establish whether this common polymorphism might be a target for preventive or therapeutic intervention.

Intra-erythrocyte cation concentrations in relation to the C1797T beta-adducin polymorphism in a general population

Genetic variability in the ADD1 (Gly460Trp) and ADD2 (C1797T) subunits of the cytoskeleton protein adducin plays a role in the pathogenesis of hypertension, possibly via changes in intracellular cation concentrations. ADD2 1797CC homozygous men have decreased erythrocyte count and hematocrit. We investigated possible association between intra-erythrocyte cations and the adducin polymorphisms. In 259 subjects (mean age 47.7 years), we measured intra-erythrocyte Na(+) [iNa], K(+) [iK] and Mg(2+) [iMg], serum cations and adducin genotypes. Genotype frequencies (ADD1: GlyGly 61.5%, Trp 38.5%; ADD2: CC 80.4%, T 19.6%) complied with Hardy-Weinberg proportions. In men, ADD2 CC homozygotes (n=100) compared to T-carriers (n=23) had slightly lower iK (85.8 versus 87.5 mmol/l cells; P=0.107), higher iMg (1.92 versus 1.80 mmol/l cells; P=0.012), but similar iNa (6.86 versus 6.88 mmol/l cells; P=0.93). In men, iK, iMg and iNa did not differ according to ADD1 genotypes. In men, iK (R(2)=0.128) increased with age and serum Na(+), but decreased with serum total calcium and the daily intake of alcohol. iMg (R(2)=0.087) decreased with age, but increased with serum total calcium. After adjustment for these covariates (P<or=0.04 for all), findings in men for iK (CC versus T: 85.8 versus 87.3 mmol/l; P=0.14) and iMg (1.91 versus 1.82 mmol/l; P=0.03) remained consistent. In 136 women, none of the phenotype-genotype relations reached significance. Changes in intra-erythrocyte cations in ADD2 1797CC homozygous men might lead to osmotic fragility of erythrocytes, but to what extent they reflect systemic changes or are possibly involved in blood pressure regulation remains unknown.

Gene-environment interaction and the GNB3 gene in the Atherosclerosis Risk in Communities study

OBJECTIVE

The purpose of this study was to investigate the interaction between the G-protein beta-3 (GNB3) 825C>T polymorphism and physical activity in relation to prevalent obesity and hypertension.

RESEARCH METHODS AND PROCEDURES

The GNB3 825C>T genotype was measured in a sample of 14,716 African Americans (AAs) and whites from the Atherosclerosis Risk in Communities (ARIC) study, and logistic regression was used to test for genetic effects and gene-environment interactions.

RESULTS

The GNB3 825C>T variant was not independently associated with prevalent obesity or hypertension in either AA or whites. However, we observed a significant interaction (P<0.001) between this variant and physical activity in predicting obesity status in AAs. In AAs who were active, each 825T allele was associated with a 20% lower prevalence of obesity (odds ratio (OR)=0.80, 95% confidence interval (CI)=0.689-0.937, P=0.005), whereas each 825T allele was associated with a 23% greater prevalence of obesity for low-active individuals (OR=1.23, 95% CI=1.06-1.44, P=0.008). We also found a significant interaction between the GNB3 825C>T polymorphism, obesity status and physical activity in predicting hypertension in the AA subjects. AA homozygotes for the 825T allele who were both obese and had a low activity level were 2.7 times more likely to be hypertensive, compared to non-obese, active 825C homozygotes (OR=2.71, 95% CI=1.19-6.17, P<0.02).

DISCUSSION

Our findings suggest that the variation within the GNB3 gene may interact with physical activity level to influence obesity status and, together with obesity and physical activity, the GNB3 825C>T variant may influence hypertension prevalence in AAs.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

Association of the C825T polymorphism of the G-protein beta3 subunit gene with hypertension, obesity, hyperlipidemia, insulin resistance, diabetes, diabetic complications, and diabetic therapies among Japanese

A C825T polymorphism of the gene encoding the G-protein beta3 subunit (GNB3) is associated with increased intracellular signal transduction. We know that this C825T polymorphism may influence hypertension and obesity. In whites, the C825T polymorphism has been reported to induce hypertension, obesity, and diabetic nephropathy. Thus, we investigated how genetic variation in the GNB3 gene is associated with hypertension, obesity, insulin resistance, diabetes, diabetic complications, and diabetic therapies in 427 Japanese subjects with type 2 diabetes mellitus and in 368 Japanese subjects who underwent general health examinations. The frequency of the GNB3 gene polymorphism was 0.48 and 0.47 in subjects with diabetes and in those who had general health examinations, respectively. The amount of hyperlipidemia of the CT allele was significantly lower than the amount in the CC allele in the Japanese subjects with diabetes. Our results suggest that the C825T polymorphism influences lipid metabolism and is not associated with hypertension, obesity, insulin resistance, diabetes, diabetic complications, or diabetic therapies.

Impact of variation in ADRB2, ADRB3, and GNB3 genes on body mass index and waist circumference in a Brazilian population

The potential effect of variants in three catecholaminergic pathway genes (ADRB2, ADRB3, and GNB3) on obesity-related traits was investigated in an European-derived Brazilian population. Three-hundred and thirty-five individuals were screened for the ADRB2 Arg16Gly and Gln27Glu, ADRB3 Trp64Arg, and GNB3 814G-->A and 825C-->T polymorphisms using PCR-based methods. The association of the polymorphisms with quantitative variables was tested separately in each sex by analysis of covariance using general linear models, including age as a covariate. Only the ADRB2 Arg16Gly polymorphism was associated with higher body mass index and waist circumference. This association was restricted to the male sample. As the number of studies increases, it becomes clear that the genetic bases of obesity are complex, with sex-specific effects a playing an important role in its etiology. In the context of this European-derived population, the ADRB2 gene accounts for a significant part of obesity-related phenotypes in males.

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.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.