title: Alpha2B-adrenergic receptor deletion polymorphism and cardiac autonomic nervous system responses to exercise in obese women.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Cross-sectional clinical study.
  
  
  METHODS
  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.
  
  
  METHODS
  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 Glu9/Glu9 subjects compared with other genotypes, while the decline of absolute HFnu was significantly smaller compared with Glu12/Glu12 genotype.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Heart Institute (InCor), Medical School, University of São Paulo, São Paulo, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Ueno
authors.forename: E S T
authors.initials: ES
authors.lastname: Frazzatto
authors.forename: L T
authors.initials: LT
authors.lastname: Batalha
authors.forename: I C
authors.initials: IC
authors.lastname: Trombetta
authors.forename: M
authors.initials: M
authors.lastname: do Socorro Brasileiro
authors.forename: C
authors.initials: C
authors.lastname: Irigoyen
authors.forename: P C
authors.initials: PC
authors.lastname: Brum
authors.forename: S M F
authors.initials: SM
authors.lastname: Villares
authors.forename: C E
authors.initials: CE
authors.lastname: Negrão
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology*; D004587:Electrophoresis, Agar Gel; D015444:Exercise / Q000502:physiology*; D005260:Female; D005838:Genotype; D018737:Hand Strength; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D007537:Isometric Contraction; D009765:Obesity / Q000235:genetics* / Q000503:physiopathology; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics*; D012815:Signal Processing, Computer-Assisted
chemical_list: C547771:ADRA2B protein, human; D018341:Receptors, Adrenergic, alpha-2