Alpha-adrenoceptor gene variants and autonomic nervous system function in a young healthy Japanese population

α_1A-adrenergic receptor (α_1A-AR) regulates the cardiac and peripheral vascular system through sympathetic activation, and α_2A-AR and α_2C-AR subtypes are essential for presynaptic feedback regulation of catecholamine release from the central and peripheral sympathetic nerve. Genetic variations in each human α-AR subtype gene have been identified and have been implicated in hypertension and cardiovascular disease. It is not yet clear whether these genetic variations actually have an effect on sympatho-vagal modulation. The aim of the present study was to evaluate the relation between the five representative genetic polymorphisms of α-AR subtypes (Arg347Cys of α_1A-AR; C-1291G, Asn251Lys, and DraI RFLP of α_2A-AR; and Del322-325 of α_2C-AR) and autonomic nervous system (ANS) function in young and healthy Japanese males. One hundred forty-nine subjects were genotyped for each α-AR polymorphism, and underwent evaluation of ANS function by power spectral analysis of heart rate variability (HRV) during supine rest and in a standing position. In a supine position, the α_1A-AR 347Cys allele was significantly associated with lower HRV sympathetic index (normalized low frequency power [LF(%)] and LF:HF ratio) and higher HRV parasympathetic index [HF(%)]. Meanwhile, subjects with the α_2C-AR Del322-325 allele had markedly higher LF(%) and LF:HF ratio and lower HF(%) than noncarriers. Thus, the α_1A-AR and α_2C-AR genetic variations influence sympatho-vagal balance even in young and healthy normotensive states, which could be postulated to constitute an intermediate phenotype for future pathological episodes of various ANS dysfunction-related diseases.