HYPERTENSION, OBESITY AND GNB3 GENE VARIANTS

Platform introducing individually tailored variability in nerve stimulations and dietary regimen to prevent weight regain following weight loss in patients with obesity

Prevention of weight regain following successful weight loss is a major challenge in the treatment of obesity, irrespective of the weight reduction method used. The majority of individuals regain the lost weight over time; thus, achieving long-term sustainability in weight loss remains an unresolved issue. A compensatory adaptation to the weight loss methods occurs in several body organs and partly explains the lack of sustainable effect. Variability is inherent in many biological systems, and patterns of variability constitute a body mechanism that is active at several levels, starting from the genes and cellular pathways through to the whole-organ level. This study aimed to describe a platform that introduces individually tailored variability in vagal nerve stimulation and dietary regimen to ensure prolonged and sustainable weight loss and prevent weight regain. The platform is intended to provide a method that can overcome the body's compensatory adaptation mechanisms while ensuring a prolonged beneficial effect.

Mutation in the beta3 subunit of Guanine nucleotide-binding protein (GNB3) gene is not associated with Type II diabetes mellitus risk: a case-control study of a North Indian population

CONTEXT

Genetics play a major role in development and pathophysiology of Type 2 diabetes mellitus (T2DM).

OBJECTIVE

To asses the association of Guanine nucleotide-binding protein (GNB3) (C825T) gene's polymorphism with T2DM.

MATERIALS AND METHODS

A case-control study including 400 North Indians was performed using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) approach to analyze genetic polymorphism.

RESULTS

No significant difference was observed in genotype and allele frequencies of GNB3 gene on comparing cases with controls.

DISCUSSION

Our study is in agreement with studies on Polish, Japanese, Hispanic-American and Danish populations who observed no significant association between GNB3 (C825T) polymorphism and T2DM.

CONCLUSION

GNB3 (C825T) polymorphism is not associated with T2DM.

Transcriptional networks in rodent models support a role for gut-brain communication in neurogenic hypertension: a review of the evidence

Hypertension (HTN) is the most prevalent condition observed in primary health care. Hypertension shows complex etiology, and neuroinflammation, overactive sympathetic drive, and the microbiome are each associated with the disease. To obtain mechanistic perspective into neurogenic HTN, we first constructed a framework for transcriptional regulators of the disease using the Comparative Toxicogenomics Database. This approach yielded a core group of 178 transcripts that are prevalent in studies of HTN, including leptin and neuropeptide Y. We then conducted a meta-analysis for transcriptome data generated in brain tissue from HTN studies. Eight expression studies were reanalyzed, in which transcriptomics was conducted in hypertensive animal models [spontaneously hypertensive rats (SHR) and high blood pressure (BPH/2J) Schlager mice] (140 microarrays). Most strikingly, a gut-brain connection was a dominant theme in both rodent models of HTN. The transcriptomic data in the rat CNS converged on processes that included gastrointestinal motility and appetite, among others. In the mouse model, pathways converged on gastrointestinal transit. Thus, our data provide a powerful review of current molecular evidence of the interplay between gut and brain in HTN. Analyses of meta-genome data also suggested that transcriptome networks related to natriuresis, thermoregulation, reproduction (lactation and pregnancy), and vasoconstriction were associated to HTN, supporting physiological observations in independent studies by others. Lastly, we present novel transcriptome networks that may contribute to a neurogenic origin of HTN. Using this framework, new therapeutic targets can be proposed and investigated in treatment strategies.

Correction of the Pathogenic Alternative Splicing, Caused by the Common GNB3 c.825C>T Allele, Using a Novel, Antisense Morpholino

The very common GNB3 c.825C>T polymorphism (rs5443) is present in approximately half of all human chromosomes. Significantly, the presence of the GNB3 825T allele has been strongly associated with predisposition to essential hypertension. Paradoxically the presence of the GNB3 825T allele, in exon 10, introduces a pathogenic alternative RNA splice site into the middle of exon 9. To attempt to correct this pathogenic aberrant splicing, we, therefore, bioinformatically designed, using a Gene Tools(®) algorithm, a GNB3-specific, antisense morpholino. It was hoped that this morpholino would behave in vitro as either a potential splice blocker and/or exon skipper, to both bind and inhibit/reduce the aberrant splicing of the GNB3 825T allele. On transfecting a human lymphoblast cell line homozygous for the 825T allele, with this antisense morpholino, we encouragingly observed both a significant reduction (from ∼58% to ∼5%) in the production of the aberrant smaller GNB3 transcript, and a subsequent increase in the normal GNB3 transcript (from ∼42% to ∼95%). Our results demonstrate the potential use of a GNB3-specific antisense morpholino, as a pharmacogenetic therapy for essential hypertension.

GNB3 and FTO Polymorphisms and Pregnancy Weight Gain in Black Women

BACKGROUND

Gestational weight gain (GWG) is a modifiable risk factor for obesity in women. Black women have the greatest prevalence of high body mass, which predisposes them to excessive GWG. Increased understanding of genetic influences on GWG has implications for the health of women. The purpose of this study was to explore the associations of GNB3 and FTO risk alleles in pregnant women with prepregnancy body mass index (BMI), GWG, and postpartum and infant birth weights.

RESEARCH DESIGN AND METHODS

This was an observational, prospective candidate gene association study. Pregnant, low-income Black women (N = 97) were enrolled in early pregnancy and followed until 6 months postpartum.

RESULTS

GWG differed depending on number of FTO risk alleles. The mean 6-month postpartum BMI differed, although not significantly, by 4 kg/m(2) between homozygous women. There was an interaction between the FTO risk allele and prepregnancy BMI (p = .022), with obese homozygote AA women having significantly higher mean GWG than obese TT women. When controlling for age and smoking, the FTO gene and physical activity predicted GWG (p = .032). Although not statistically significant, women who carried the GNB3 T risk allele gained 6 pounds more than noncarriers, and mean 6-month postpartum BMI differed by 2.2 kg/m(2) between homozygous women. Neither the GNB3 nor FTO gene predicted prepregnancy BMI, infant birth weight, or postpartum weight.

CONCLUSION

Obese women homozygous for the FTO risk allele were at greater risk of excessive GWG compared to nonrisk allele homozygous obese women or nonobese women. This study provides evidence of the FTO gene's effect on GWG in Black women.

G-protein β3 subunit gene 825C/T polymorphism and its association with the presence, severity, and duration of vasculogenic erectile dysfunction

OBJECTIVE

To investigate the association between G-protein β3 (GNB3) subunit gene 825C/T polymorphism and vasculogenic ED (VED).

DESIGN

Case-control study.

SETTING

Private urology and andrology clinic.

PATIENT(S)

The study included 246 patients with VED and 492 healthy controls, Caucasians of Iranian descent.

INTERVENTION(S)

Typing of the polymorphism was performed using the polymerase chain reaction restriction fragment length polymorphism technique.

MAIN OUTCOME MEASURE(S)

To test the hypothesis of whether the presence of the 825T allele of the GNB3 gene is associated with an increased risk of VED.

RESULT(S)

The CT genotype was more prevalent in VED patients relative to healthy controls (adjusted odds ratio [OR] = 2.34; 95% confidence interval [CI], 1.10-4.26). Interaction between T allele carriership and VED was significant. The dominant model CT + TT variant was associated with a 3.74-fold increase in the adjusted risk (OR = 3.74; 95% CI, 1.11-12.4) for the occurrence of VED. Our results indicate that the GNB3 polymorphism is associated with higher systolic blood pressure, higher dyslipidemia, and higher body mass index. The 825TT genotype was associated with a more than five-fold increased risk of severe VED compared with the 825CC genotype (OR = 5.62; 95% CI, 3.54-9.25). Significantly different onset of age of VED was not found between the genotypes for the GNB3 polymorphism.

CONCLUSION(S)

The GNB3 polymorphism is an independent risk factor for VED in Iranian males. Our findings confirm a role of GNB3 in the genetic susceptibility of VED and suggest that GNB3 polymorphism should be taken into consideration to improve the assessment of an individual's risk of VED.

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.

Mutations in the human phospholamban gene in patients with heart failure

BACKGROUND

Phospholamban (PLN) is a crucial Ca(2+) cycling protein and a primary mediator of the β-adrenergic effects resulting in enhanced cardiac output. Mutations in the gene encoding PLN have been associated with idiopathic dilated cardiomyopathy; however, no systematic search for PLN mutations in heart failure has been conducted.

METHODS

We screened a cohort of 1,014 Brazilian patients with heart failure for mutations in the PLN gene. Molecular modeling studies of the mutations found were developed. Different disease etiologies were present in our sample: idiopathic, ischemic, Chagas, valvular, hypertensive, and others.

RESULTS

We identified 4 unrelated patients with PLN mutations (prevalence of 0.4%), 3 of them in the same amino acid residue (R9). Two patients presented a G-T missense mutation at the G26 nucleotide, which encodes an Arg-Leu substitution at codon 9 (R9L). One patient presented a G-A missense mutation at the same nucleotide, which encodes an Arg-His substitution at codon 9 (R9H). The fourth affected patient presented a T-G nonsense mutation at the nucleotide 116, substituting a termination codon for Leu-39 (L39stop). Molecular modeling studies suggested that R9L and R9H mutations might affect the region involved in protein kinase A docking and probably affect the mechanism modulating the release of phosphorylated PLN from the substrate binding site of protein kinase A.

CONCLUSIONS

Mutations in the PLN gene are a rare cause of heart failure, present almost exclusively in patients with dilated cardiomyopathy etiology. The Arg9 and Leu39 residues are the leading location of mutations described at this locus to date. Despite the few mutated residues described to date, the clinical spectrum of presentation appears to vary considerably.

Predictors of weight loss and maintenance in patients treated with antiobesity drugs

BACKGROUND

The prevalence of obesity and related diseases has increased enormously in the last few decades, becoming a very important medical and social issue. Because of the increasing number of people who need weight loss therapies and the high costs associated with these, the search for reliable predictors of success for weight loss and weight maintenance treatments has become a priority.

OBJECTIVE

A literature review was undertaken to identify possible predictors of outcome of weight loss and weight maintenance in patients treated with antiobesity drugs.

RESULTS

For the majority of variables, published data are not sufficient to define their role on final outcomes. Among all considered factors, only early response to treatment appeared to be a reliable positive predictor, and diabetes a negative predictor of weight loss and maintenance.

CONCLUSION

To date, no definitive results have been obtained. Due to the great benefits of reliable predictors of outcome associated to currently available antiobesity drugs and those under development, identifying these predictors has to be supported and encouraged.

PTPN11 and KRAS gene analysis in patients with Noonan and Noonan-like syndromes

Noonan and Noonan-like syndromes are disorders of dysregulation of the rat sarcoma viral oncogene homolog (RAS)-mitogen-activated protein kinase signaling pathway. In Noonan syndrome (NS), four genes of this pathway (PTPN11, SOS1, RAF1, and KRAS) are responsible for roughly 70% of the cases. We analyzed PTPN11 and KRAS genes by bidirectional sequencing in 95 probands with NS and 29 with Noonan-like syndromes, including previously reported patients already screened for PTPN11 gene mutations. In the new patients with NS, 20/46 (43%) showed a PTPN11 gene mutation, two of them novel. In our total cohort, patients with NS and a PTPN11 mutation presented significantly higher prevalence of short stature (p = 0.03) and pulmonary valve stenosis (p = 0.01), and lower prevalence of hypertrophic cardiomyopathy (p = 0.01). Only a single gene alteration, of uncertain role, was found in the KRAS gene in an NS patient also presenting a PTPN11 gene mutation. We further analyzed the influence in clinical variability of three frequent polymorphisms found in the KRAS gene and no statistically significant difference was observed among the frequency of clinical findings regarding the studied polymorphisms.

The effect of nutrition on blood pressure

The incidence and severity of hypertension are affected by nutritional status and intake of many nutrients. Excessive energy intake and obesity are major causes of hypertension. Obesity is associated with increased activity of the renin-angiotensin-aldosterone and sympathetic nervous systems, possibly other mineralcorticoid activity, insulin resistance, salt-sensitive hypertension and excess salt intake, and reduced kidney function. High sodium chloride intake strongly predisposes to hypertension. Increased alcohol consumption may acutely elevate blood pressure. High intakes of potassium, polyunsaturated fatty acids, and protein, along with exercise and possibly vitamin D, may reduce blood pressure. Less-conclusive studies suggest that amino acids, tea, green coffee bean extract, dark chocolate, and foods high in nitrates may reduce blood pressure. Short-term studies indicate that specialized diets may prevent or ameliorate mild hypertension; most notable are the Dietary Approaches to Stop Hypertension (DASH) diet, which is high in fruits, vegetables, and low-fat dairy products, and the DASH low-sodium diet. Long-term compliance to these diets remains a major concern.

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.

Weight loss and body fat reduction under sibutramine therapy in obesity with the C825T polymorphism in the GNB3 gene

The relationship between weight reduction after sibutramine treatment and a single nucleotide polymorphism, 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 single nucleotide polymorphism could influence weight reduction and body composition change under sibutramine therapy in 131 obese Taiwanese patients. By comparing the sibutramine and placebo groups with analysis of covariance, our data showed a strong effect of sibutramine on weight reduction (7.4+/-1.4 vs. 3.4+/-1.2 kg; P<0.001) and on body fat percentage loss (4.2+/-0.1 vs. 2.1+/-0.1%; P<0.001) in the combined TT+TC carriers. In contrast, sibutramine caused no significant additional effect on weight loss (P = 0.078) or on body fat percentage loss (P = 0.441) in homozygous C allele carriers.

Interaction of serotonin-related genes affects short-term antidepressant response in major depressive disorder

BACKGROUND

Four serotonin-related genes including guanine nucleotide binding protein beta polypeptide 3 (GNB3), 5-hydroxytryptamine receptor 1A (HTR1A; serotonin receptor 1A), 5-hydroxytryptamine receptor 2A (HTR2A; serotonin receptor 2A), and solute carrier family 6 member 4 (SLC6A4; serotonin neurotransmitter transporter) have been suggested to be candidate genes for influencing antidepressant treatment outcome. The aim of this study was to explore whether interaction among these genes could contribute to the pharmacogenomics of short-term antidepressant response in a Taiwanese population with major depressive disorder (MDD).

METHODS

Included in this study were 101 MDD patients who were treated with antidepressants, 35 of whom were rapid responders and 66 non-responders after 2weeks of treatment. We genotyped four single nucleotide polymorphisms (SNPs), including GNB3 rs5443 (C825T), HTR1A rs6295 (C-1019G), HTR2A rs6311 (T102C), and SLC6A4 rs25533, and employed the generalized multifactor dimensionality reduction (GMDR) method to investigate gene-gene interactions.

RESULTS

Single-locus analyses showed the GNB3 rs5443 polymorphism to be associated with short-term antidepressant treatment outcome (P-value=0.029). We did not correct for multiple testing in these multiple exploratory analyses. Finally, the GMDR approach identified a significant gene-gene interaction (P-value=0.025) involving GNB3 and HTR2A, as well as a significant 3-locus model (P-value=0.015) among GNB3, HTR2A, and SLC6A4.

CONCLUSIONS

These results support the hypothesis that GNB3, HTR2A, and SLC6A4 may play a role in the outcome of short-term antidepressant treatment for MDD in an interactive manner. Future research with independent replication using large sample sizes is needed to confirm the functions of the candidate genes identified in this study as being involved in short-term antidepressant treatment response.

Genetic variation in female BMI increases with number of children born but failure to replicate association between GNbeta3 variants and increased BMI in parous females

Objective:As post-pregnancy weight retention in women is a risk factor for obesity later in life, we assessed the changes in magnitude of genetic and environmental variation in BMI due to parity in an Australian female sample, comprising 11,915 female twins and their sisters.Results:Total variance of BMI increased with parity, primarily driven by an increase in nonadditive genetic variance. This finding was of particular interest given Gutersohn et al's (2000) report of recessive association between post-partum weight retention and the 825T allele of theGNβ3gene (rs5443) at 12p13.31. Hence, we attempted to replicate this association and test an additional three SNPs also located near or onGNβ3(rs10744716 (upstream), rs5442 (exon 10), rs5446 (exon 11)) in a sample of 3131 females and 1693 males from 2585 twin families. No association was found between these SNPs among females, even when allowing for a genotype by parity effect. However, a significant association was observed among males for rs10744716 (χ22= 10.22,p= 0.006; effect size = 0.47kg/m2), representing a novel association between a region upstream ofGNβ3and male BMI.

Implications of gene-behavior interactions: prevention and intervention for obesity

A vast body of research exists to demonstrate that obesity is a complex disorder with a strong genetic basis and a multifactorial etiology. Yet despite the overwhelming evidence that genes play an important role in the development of obesity, many people argue that the increasing prevalence of obesity is simply due to an abundance of palatable food and a dearth of opportunities for physical exercise. While activity and eating behaviors contribute substantially to the development of obesity, considering these to be the only etiologic factors is directly contradictory to what is now known about how eating and energy balance are regulated. Our understanding of the molecular processes controlling eating behavior, in particular, has accelerated exponentially in the last 10 years, and this is one area in which obesity genetics has made great progress. Our challenge is to understand more fully how genetic variation may interact with behavioral factors to influence the regulation of body weight and adiposity. Although exercise and diet strategies are used routinely for obesity treatment, there is a huge variability in how individuals respond to these interventions. There is also a substantial amount of evidence that such responses may also be regulated by genes. Understanding gene-response relationships is the key to developing more efficacious intervention and prevention programs for obesity.

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.

Implications of gene-behavior interactions: prevention and intervention for obesity

A vast body of research exists to demonstrate that obesity is a complex disorder with a strong genetic basis and a multifactorial etiology. Yet despite the overwhelming evidence that genes play an important role in the development of obesity, many people argue that the increasing prevalence of obesity is simply due to an abundance of palatable food and a dearth of opportunities for physical exercise. While activity and eating behaviors contribute substantially to the development of obesity, considering these to be the only etiologic factors is directly contradictory to what is now known about how eating and energy balance are regulated. Our understanding of the molecular processes controlling eating behavior, in particular, has accelerated exponentially in the last 10 years, and this is one area in which obesity genetics has made great progress. Our challenge is to understand more fully how genetic variation may interact with behavioral factors to influence the regulation of body weight and adiposity. Although exercise and diet strategies are used routinely for obesity treatment, there is a huge variability in how individuals respond to these interventions. There is also a substantial amount of evidence that such responses may also be regulated by genes. Understanding gene-response relationships is the key to developing more efficacious intervention and prevention programs for obesity.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

Differential use of available genetic tests among primary care physicians in the United States: results of a national survey

PURPOSE

This study assesses primary care physicians' experience ordering and referring patients for genetic testing, and whether minority-serving physicians are less likely than those serving fewer minorities to offer such services.

METHODS

Survey of a random sample of 2000 primary care physicians in the United States (n = 1120, 62.3% response rate based on eligible respondents) conducted in 2002 to assess what proportion have (1) ever ordered a genetic test in general or for select conditions; (2) ever referred a patient for genetic testing to a genetics center or counselor, a specialist, a clinical research trial, or to any site of care.

RESULTS

Nationally, 60% of primary care physicians have ordered a genetic test and 74% have referred a patient for genetic testing. Approximately 62% of physicians have referred a patient for genetic testing to a genetics center/counselor or to a specialist, and 17% to a clinical trial. Minority-serving physicians were significantly less likely to have ever ordered a genetic test for breast cancer, colorectal cancer, or Huntington disease, or to have ever referred a patient for genetic testing relative to those serving fewer minorities.

CONCLUSIONS

Reduced utilization of genetic tests/referrals among minority-serving physicians emphasizes the importance of tracking the diffusion of genomic medicine and assessing the potential impact on health disparities.

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.