Our data suggest that individuals homozygous for the Arg389 allele of the beta(1)-adrenergic receptor gene are at increased risk to develop hypertension.

A SNP upstream of the INSIG2 gene, rs7566605, was recently found to be associated with obesity as measured by body mass index (BMI) by Herbert and colleagues. The association between increased BMI and homozygosity for the minor allele was first observed in data from a genome-wide association scan of 86,604 SNPs in 923 related individuals from the Framingham Heart Study offspring cohort. The association was reproduced in four additional cohorts, but was not seen in a fifth cohort. To further assess the general reproducibility of this association, we genotyped rs7566605 in nine large cohorts from eight populations across multiple ethnicities (total n = 16,969). We tested this variant for association with BMI in each sample under a recessive model using family-based, population-based, and case-control designs. We observed a significant (p < 0.05) association in five cohorts but saw no association in three other cohorts. There was variability in the strength of association evidence across examination cycles in longitudinal data from unrelated individuals in the Framingham Heart Study Offspring cohort. A combined analysis revealed significant independent validation of this association in both unrelated (p = 0.046) and family-based (p = 0.004) samples. The estimated risk conferred by this allele is small, and could easily be masked by small sample size, population stratification, or other confounders. These validation studies suggest that the original association is less likely to be spurious, but the failure to observe an association in every data set suggests that the effect of SNP rs7566605 on BMI may be heterogeneous across population samples.

Abstract-Gitelman's syndrome is an autosomal recessive disorder characterized by electrolyte disturbances and low blood pressure. The disease is caused by homozygous or compound heterozygous inactivating mutations in the thiazidesensitive NaCl-cotransporter gene leading to reduced renal sodium reabsorption. We report 4 patients with Gitelman's syndrome from southern Sweden, all in whom we identified compound heterozygous mutations in the thiazide-sensitive NaCl-cotransporter gene (Gly439Ser, Gly731Arg, Gly741Arg, Thr304Pro, and 2745insAGCA), of which the latter 2 have not been described before. We hypothesized that such mutations in their heterozygous form protect against primary hypertension in the general population and that the gene may also harbor activating mutations that increase the risk for primary hypertension. Accordingly, the gene was screened for mutations in 20 patients with primary hypertension and in 20 normotensive subjects by single-strand conformation polymorphism and direct DNA sequencing. The Arg904Gln, Gly264Ala, and C1420T variants, found in the mutation screening of subjects without Gitelman's syndrome, were studied further. Population genotype frequencies were determined in 292 unrelated patients with primary hypertension and 264 unrelated normotensive subjects from southern Sweden. Gln904 homozygotes were overrepresented in hypertensive patients compared with normotensive subjects (5 of 292 versus 0 of 264; Pϭ0.03). In conclusion, we confirm that Gitelman's syndrome is caused by mutations in the thiazide-sensitive NaCl-cotransporter gene. Our results further suggest that subjects homozygous for the Gln904 variant have an increased risk for development of primary hypertension. (Hypertension. 2000;36:389-394.)

Abstract-The aim of this study was to investigate whether polymorphisms in the ␤ 2 -adrenergic receptor gene (5ЈLC-Arg19Cys, Arg16Gly, Gln27Glu) are associated with hypertension in patients with or without type 2 diabetes and with the blood pressure levels in normotensive sib pairs. The association study included 291 hypertensive patients without type 2 diabetes, 124 hypertensive patients with type 2 diabetes, and 265 healthy control subjects from Sweden. In addition, normotensive sib pairs that were discordant for the Arg16Gly (72 pairs) and Gln27Glu (40 pairs) polymorphisms were identified in type 2 diabetes families from Finland. Genotyping was performed using polymerase chain reaction-restriction fragment-length polymorphism analysis. Homozygous carriers of the Arg16 allele had a significantly increased odds ratio (OR) for hypertension in patients with type 2 diabetes (OR 2.14; 95% confidence interval [CI], 1.05 to 4.33), particularly among lean (body mass indexϽ27 kg/m 2 ) patients (OR 3.47; 95% CI, 1.06 to 11.33). The Gln27 allele showed a weaker association to hypertension (OR 1.55; 95% CI, 1.00 to 2.41) and was found to be in linkage disequilibrium with the Cys19 allele of the 5ЈLC-Arg19Cys polymorphism. In the paired-sibling analysis, siblings with at least 1 copy of the Arg16 allele had higher systolic blood pressure (Pϭ0.049), and nondiabetic siblings had a higher body mass index (Pϭ0.026) than siblings homozygous for the Gly16 allele. These results indicate that the Arg16 allele of the ␤ 2 -adrenergic receptor gene confers an increased risk for hypertension in subjects with type 2 diabetes and is associated with higher blood pressure levels and higher body mass index in sib pairs who are discordant for the polymorphism.