Haplotypes of the beta2-adrenergic receptor gene are associated with essential hypertension in a Singaporean Chinese population.

OBJECTIVE: To investigate the relation between the gene encoding the beta2-adrenergic receptor (B2AR) and essential hypertension in a Singaporean Chinese cohort. METHODS: Three single nucleotide polymorphisms (SNPs) were genotyped in 190 cases and 323 controls, and eight haplotypes were determined and tested for association using the likelihood test statistic. RESULTS: We observed a significant difference in haplotype frequency distributions between the cases and the controls (P <0.00001). A logistic regression model fitted to the data supported this finding. CONCLUSION: The results suggest that variants at the B2AR locus may play a role in the pathophysiology of hypertension in this population.

Genetic variation at CHRNA5-CHRNA3-CHRNB4 interacts with smoking status to influence body mass index.

BACKGROUND: Cigarette smoking is associated with lower body mass index (BMI), and a commonly cited reason for unwillingness to quit smoking is a concern about weight gain. Common variation in the CHRNA5-CHRNA3-CHRNB4 gene region (chromosome 15q25) is robustly associated with smoking quantity in smokers, but its association with BMI is unknown. We hypothesized that genotype would accurately reflect smoking exposure and that, if smoking were causally related to weight, it would be associated with BMI in smokers, but not in never smokers. METHODS: We stratified nine European study samples by smoking status and, in each stratum, analysed the association between genotype of the 15q25 SNP, rs1051730, and BMI. We meta-analysed the results (n = 24,198) and then tested for a genotype × smoking status interaction. RESULTS: There was no evidence of association between BMI and genotype in the never smokers {difference per T-allele: 0.05 kg/m(2) [95% confidence interval (95% CI): -0.05 to 0.18]; P = 0.25}. However, in ever smokers, each additional smoking-related T-allele was associated with a 0.23 kg/m(2) (95% CI: 0.13-0.31) lower BMI (P = 8 × 10(-6)). The effect size was larger in current [0.33 kg/m(2) lower BMI per T-allele (95% CI: 0.18-0.48); P = 6 × 10(-5)], than in former smokers [0.16 kg/m(2) (95% CI: 0.03-0.29); P = 0.01]. There was strong evidence of genotype × smoking interaction (P = 0.0001). CONCLUSIONS: Smoking status modifies the association between the 15q25 variant and BMI, which strengthens evidence that smoking exposure is causally associated with reduced BMI. Smoking cessation initiatives might be more successful if they include support to maintain a healthy BMI.

High-resolution HLA genotyping and severe cutaneous adverse reactions in lamotrigine-treated patients.

BACKGROUND: Severe cutaneous adverse reactions (SCARs) are associated with over 200 medicines including lamotrigine, an antiepileptic drug. Previous studies have suggested the involvement of immune mechanisms in the development of drug-induced SCARs. METHODS: High-resolution HLA genotyping was performed for 65 patients of European ancestry treated with lamotrigine (22 cases with lamotrigine-induced SCARs and 43 controls on lamotrigine without SCAR-related symptoms). Association of HLA genetic variants with SCARs in these patients were evaluated by contrasting allele frequencies between the cases and the controls for each of 112 HLA four-digit alleles. RESULTS: Five alleles were observed with higher frequencies in the cases compared with the treated controls with exact P values less than 0.05. These include B*5801 (P = 0.037), previously reported to be associated with allopurinol-induced SCARs. Marginal association evidence was also observed for alleles Cw*0718 and DQB1*0609, both of which were strongly correlated with B*5801. Other alleles identified were A*6801 (P = 0.012) and DRB1*1301 (P = 0.045). In contrast to the study of carbamazepine-induced Stevens-Johnson syndrome in Han Chinese patients, none of the cases carried B*1502. Accounting for the large number of hypothesis tests conducted, none of the associations identified were statistically significant. CONCLUSION: No single major HLA-related genetic risk factor was identified for lamotrigine-induced SCARs in patients of European origin. Only suggestive evidence was obtained for B*5801, A*6801, Cw*0718, DQB1*0609, and DRB1*1301. Confirmation of these results in a larger, independent sample is needed to determine whether any of the HLA alleles identified are truly associated with the development of lamotrigine-induced SCARs.