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

Abstract

Objective: To investigate the association of short form (Glu 9 /Glu 9 ) of the 12Glu9 deletion polymorphism of the a 2B -adrenergic receptor (a 2B -AR) gene polymorphism with the cardiac autonomic responsiveness during sustained isometric handgrip exercise. Design: Cross-sectional clinical study. Subjects: In all, 97 normotensive obese women (body mass index (BMI) ¼ 33.2 kg/m 2 ). Of these, 78 (80.41%) were genotyped as Glu 12 /Glu 12 , 13 (13.40%) as Glu 12 /Glu 9 and six (6.19%) as Glu 9 /Glu 9 form. Measurements: 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. Results: There were no differences in baseline measurements among groups. The absolute level of LFnu throughout handgrip exercise was significantly lower in Glu 9 /Glu 9 subjects compared with other genotypes, while the decline of absolute HFnu was significantly smaller compared with Glu 12 /Glu 12 genotype. Conclusion: These findings suggest that 12Glu9 deletion polymorphism of the a 2B -AR gene (Glu 9 /Glu 9 genotype) might result in reduced autonomic responsiveness by altering cardiac sympathetic and vagal function during sustained handgrip exercise in normotensive obese women.

Day–night pattern of autonomic nervous system modulation in patients with heart failure with and without sleep apnea

“…Cardiac autonomic nervous modulation was assessed by R-R interval power spectral analysis computed by an autoregressive algorithm. Details of this analysis have been previous described [24]. Briefly, the power was expressed in both absolute and in normalized units (nu).…”

Regular physical exercise improves cardiac autonomic and muscle vasodilatory responses to isometric exercise in healthy elderly

“…Therefore, it is important to evaluate the integrity of the cardiovascular system by using a sympathetic excitatory maneuver by isometric exercise (handgrip maneuver), which stimulates the central command through the mechanoreceptors and metaboreceptors localized in the peripheral muscles 12. Handgrip exercise activity activates the β-adrenergic system, which stimulates the release of neuromediated nitric oxide, thus increasing muscle vasodilation 13.…”

Chromosome 2q12, the ADRA2B I/D polymorphism and metabolic syndrome

“…In nondiabetic men with the D/D genotype, the general autonomic tone is depressed (lower total and low-frequency power values) and vagal activity becomes impaired with time [21]. The absolute level of low frequency in heart variability throughout handgrip exercise was significantly lower in D/D individuals as compared with other genotypes, whereas the decline of absolute high frequency was significantly smaller compared with I/I genotype in normotensive obese women [49]. These findings suggest that the ADRA2B deletion polymorphism might result in metabolic disorder by altering autonomous nervous system function.…”