Hypertension
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Few studies have examined to what extent genetic variants of the beta2-adrenoceptor (ADRB2) are involved in the development of hypertension with age, although beta2-adrenergic receptor responsiveness declines in older subjects. To investigate this, 10 common single-nucleotide polymorphisms (SNPs) in the promoter and coding regions of the ADRB2 gene were genotyped in an unrelated population consisting of 2 ethnic groups: European American (EA; n=610) and African American (AA; n=420). ADRB2 haplotypes were estimated by expectation maximization (EM) algorithm-based methods. ⋯ This age-specific effect was further supported by the observations that young subjects carrying > or =1 copy of haplotype 1 had significantly lower diastolic blood pressure and nearly 2-fold higher ADRB2 binding density than the noncarriers (P<0.05). With aging, their ADRB2 numbers decreased to the level of the noncarriers, along with increased body mass index (7%; P<0.05) and decreased heart rate (7%; P<0.001). Our study suggests that age is an important modifier for the effects of ADRB2 polymorphisms on ADRB2 function and the development of hypertension.