The β₁- and β₂-adrenergic receptors (ARs) coexist in the human heart and control sympathetic responses. Several functional genetic variations in the β-AR genes (ADRB1 or ADRB2) have been identified and implicated as causes of hypertension and cardiovascular disease. We assessed the relationship between 4 representative genetic polymorphisms of β-AR (Ser49Gly and Arg389Gly in β₁-AR, Arg16Gly and Gln27Glu in β₂-AR) and autonomic nervous system (ANS) function in healthy young Japanese males.

One hundred forty-nine subjects were genotyped for each β-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. The low-frequency (LF; <0.15 Hz) and high-frequency (HF; >0.15 Hz) components of HRV were quantified by frequency domain analysis and expressed in absolute and normalized units.

The β₂-AR Arg16 homozygous group had a significantly lower diastolic and mean blood pressure than the Gly16 group in both Arg16Gly individual and Gln27Glu polymorphism combined diplotype-based analyses. In a supine rest position, subjects homozygous for the β₂-AR Arg16 allele had significantly lower HRV sympathetic indices (LF [%] and LF/HF ratio) but higher HRV parasympathetic indices (HF [%]) than the Gly16 allele carriers. Meanwhile, the β₂-AR Glu27 allele was significantly associated with higher HRV LF power than were Gln27 homozygous subjects. In the analysis of gene-gene interaction, the effects of the β₂-AR Arg16 homozygotes on HRV were more apparent in the presence of the β₁-AR Gly389allele. No independent associations were observed between the β₁-AR Ser49Gly or Arg389Gly genotypes and HRV indices.

The Arg16Gly polymorphism of the β₂-AR is related to the modulation of sympathovagal balance, and β₂-AR Glu27 allele carriers potentially have increased autonomic activity. Thus, β-AR genotype-related differences in basic receptor function cause phenotypic differences in cardiac ANS function.