β ₂- and β ₃-Adrenergic receptor polymorphisms and exercise hemodynamics in postmenopausal women

We sought to determine whether common genetic variations at the β ₂ (β ₂-AR, Gln27Glu) and β ₃ β ₃-AR, Trp64Arg) adrenergic receptor gene loci were associated with cardiovascular (CV) hemodynamics during maximal and submaximal exercise. CV hemodynamics were assessed in 62 healthy postmenopausal women (20 sedentary, 22 physically active, and 20 endurance athletes) during treadmill exercise at 40, 60, 80, and 100% maximal O ₂ uptake using acetylene rebreathing to quantify cardiac output. The β ₂-AR genotype and habitual physical activity (PA) levels interacted to significantly associate with arteriovenous O ₂ difference (a-vDO ₂) during submaximal exercise (P = 0.05), with the highest submaximal exercise a-vDO ₂ in sedentary women homozygous for the β ₂-AR Gln allele and no genotype-dependent differences in submaximal exercise a-vDO ₂ in physically active and athletic women. The β ₂-AR genotype also was independently associated with a-vDO ₂ during submaximal (P = 0.004) and ∼100% maximal O ₂ uptake exercise (P = 0.006), with a 1.2-2 ml/100 ml greater a-vDO ₂ in the Gln/Gln than in the Glu/Glu genotype women. The β ₃-AR genotype, independently or interacting with habitual PA levels, was not significantly associated with any CV hemodynamic variables during submaximal or maximal exercise. Thus it appears that the β ₂-AR genotype, both independently and interacting with habitual PA levels, is significantly associated with a-vDO ₂ during exercise in postmenopausal women, whereas the β ₃-AR genotype does not appear to be associated with any maximal or submaximal exercise CV hemodynamic responses in postmenopausal women.