G Protein beta3 Subunit Polymorphism and Long-Term Prognosis of Functional Dyspepsia

BACKGROUND/AIMS: A link between G protein beta3 (GNB3) polymorphism and functional dyspepsia (FD) has been suggested. The aim of this study was to determine the role of GNB3 polymorphism in the long-term prognosis of FD in Koreans. METHODS: FD patients and normal healthy controls were recruited from patients who visited our center between December 2006 and June 2007. All of the subjects completed Rome III questionnaires before undergoing upper gastrointestinal endoscopy and colonoscopy. Genomic DNA was extracted for GNB3 genotyping. After 5 years, the subjects were reevaluated using the same questionnaires. RESULTS: GNB3 825T carrier status was significantly related to FD in Koreans (p=0.04). After 5 years, 61.0% of the initial FD patients and 12.2% of the initial normal subjects were diagnosed with FD (odds ratio [OR], 11.7; 95% confidence interval [CI], 4.3 to 31.1; p<0.001). Regardless of the GNB3 genotype (p=0.798), female sex was strongly correlated with FD after 5 years (OR, 3.3; 95% CI, 1.2 to 9.1; p=0.017). CONCLUSIONS: The T allele of GNB3 is linked to FD in Koreans but does not predict long-term prognosis. Female sex is related to a higher prevalence of FD after 5 years.

G-Protein Beta3 Subunit C825T Polymorphism in Patients With Overlap Syndrome of Functional Dyspepsia and Irritable Bowel Syndrome

BACKGROUND/AIMS: Guanine nucleotide binding protein (G-protein) beta polypeptide 3 (GNB3) C825T polymorphism alters intracellular signal transduction, which may lead to motor or sensory abnormalities of the gastrointestinal tract. The aim of the present study was to evaluate the association of the GNB3 C825T polymorphism with susceptibility to overlap syndrome of functional dyspepsia (FD) and irritable bowel syndrome (IBS) in a Korean population. METHODS: One hundred sixty-seven patients with FD alone, 60 patients with IBS alone, 85 patients with the overlap of FD and IBS, and 434 asymptomatic healthy subjects participated in the study. Genotyping for GNB3 C825T polymorphism was performed using their blood samples. RESULTS: No association of GNB3 genotypes in patients with FD alone, IBS alone or overlap phenotype, when compared to genotypes in controls, was detected. The frequency of CT and TT genotypes relative to the CC genotype for the phenotypes of FD alone, IBS alone and the coexistence of FD and IBS did not significantly differ. Comparison of the TT genotype with the CC/CT genotype showed no significant association for each phenotype group. CONCLUSIONS: There is no apparent association of the GNB3 C825T polymorphism with the susceptibility to FD, IBS or the overlap of FD and IBS. Larger-scale studies and further investigation on other candidate genes are required.

Combined Action of ACE Gene I/D and GNB3 Gene C825T Polymorphisms on Essential Hypertension in Northern Han Chinese / 生物化学与生物物理进展

Essential hypertension (EH), a complex polygenic disease, is considered to the result of the genetic interaction of multiple gene alterations in concert with environmental factors. Evidences showed that angiotensin-converting enzyme (ACE) gene and G protein beta3 subunit (GNB3) gene are both important susceptibility genes for EH, and that there exists putative biological connection between the two genes in developing hypertension. To investigate whether hypertension was affected by gene-gene interaction between the two genes in the northern Chinese Han population, a case-control association study including 502 hypertensive cases and 490healthy controls was conducted, selecting the ACE gene I/D polymorpinsm and the GNB3 gene C825T polymorphism. Linkage disequilibrium analysis revealed a significant nonrandom distribution only in male hypertensives, indicating that interaction between ACE gene and GNB3 gene may predispose males to the occurrence of hypertension. Multivariate stepwise logistic regression in single locus analysis, with adjustment for common risk factors for hypertension, demonstrated that the OR for DD/ID versus Ⅱ for hypertension among men was significant (OR 1.57; 95% CI, 1.09 ～2.27; P = 0.016) in dominant genetic model. In combination analysis stratified with respect to gender, slightly significant ORs were found after adjustment in males: OR for TT vs CC, 0.11; 95%CI, 0.01 ～0.99; P = 0.049 within ACE DD genotype; OR for DD/ID vs Ⅱ, 1.52; 95% CI, 1.01 ～2.29; P = 0.047 within GNB3 CC+CT genotype. The results suggest that ACE, or a nearby gene, is a male-specific susceptible gene for hypertension, and that there may exist epistatic gene-gene interaction between ACE D allele and GNB3 825C allele.