α2B-Adrenergic receptor deletion polymorphism and cardiac autonomic nervous system responses to exercise in obese women

Abstract

To investigate the association of short form (Glu9/Glu9) of the 12Glu9 deletion polymorphism of the alpha2B-adrenergic receptor (alpha2B-AR) gene polymorphism with the cardiac autonomic responsiveness during sustained isometric handgrip exercise. Cross-sectional clinical study. In all, 97 normotensive obese women (body mass index (BMI) = 33.2 kg/m2). Of these, 78 (80.41%) were genotyped as Glu12/Glu12, 13 (13.40%) as Glu12/Glu9 and six (6.19%) as Glu9/Glu9 form. The sympathovagal balance was assessed by means of power spectral analysis of heart rate variability at rest and during sustained isometric handgrip exercise at 30% of maximal voluntary handgrip contraction for 3 min. Two spectral components were analysed: low-frequency component reflecting sympathetic efferent activity and high-frequency power (HFnu) reflecting parasympathetic modulation. In addition, a normalized low-frequency power (LFnu) and HFnu were analysed. Genotypes were determined by polymerase chain reaction followed by agarose gel electrophoresis. There were no differences in baseline measurements among groups. The absolute level of LFnu throughout handgrip exercise was significantly lower in Glu9/Glu9 subjects compared with other genotypes, while the decline of absolute HFnu was significantly smaller compared with Glu12/Glu12 genotype. These findings suggest that 12Glu9 deletion polymorphism of the alpha2B-AR gene (Glu9/Glu9 genotype) might result in reduced autonomic responsiveness by altering cardiac sympathetic and vagal function during sustained handgrip exercise in normotensive obese women.