title: Arg64 beta3-adrenoceptor variant and the components of energy expenditure.
abstract: OBJECTIVE
  To determine Trp64Arg beta(3)-adrenoceptor genotype-specific differences in the components of energy expenditure.
  
  
  OBJECTIVE
  We hypothesized that resting metabolic rate (RMR) and physical activity levels would be lower and that thermic effect of feeding (TEF) would be higher in those with the Arg64 allele.
  
  
  METHODS
  RMR and TEF were measured by indirect calorimetry, physical activity by questionnaire, and total energy expenditure by the doubly labeled water method. Genotype-specific measures were compared using ANOVA and analysis of covariance (ANCOVA).
  
  
  RESULTS
  RMR in Arg64 homozygotes was significantly lower than in Trp64 homozygotes [Arg64, 1373 +/- 259 kcal/d (n = 15) vs. Trp64Arg, 1538 +/- 238 kcal/d (n = 25) vs. Trp64, 1607 +/- 290 kcal/d (n = 22); p < 0.01]. TEF was significantly higher in Arg64 homozygotes compared with Trp64 homozygotes (Arg64, 359 +/- 28 kcal/d; Trp64Arg, 322 +/- 22 kcal/d; and Trp64, 279 +/- 23 kcal/d; p < 0.05). No differences were identified between genotypes in physical activity or in total energy expenditure.
  
  
  CONCLUSIONS
  Our results suggest that the Arg64 beta(3)-adrenoceptor allele contributes significantly to the genetic variability in both RMR and TEF.
authors.affiliation: Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. jwalston@jhmi.edu
authors.forename: Jeremy
authors.initials: J
authors.lastname: Walston
authors.forename: Ross E
authors.initials: RE
authors.lastname: Andersen
authors.forename: Michael
authors.initials: M
authors.lastname: Seibert
authors.forename: Heather
authors.initials: H
authors.lastname: Hilfiker
authors.forename: Brock
authors.initials: B
authors.lastname: Beamer
authors.forename: Jacob
authors.initials: J
authors.lastname: Blumenthal
authors.forename: Eric T
authors.initials: ET
authors.lastname: Poehlman
mesh_terms: D000328:Adult; D001120:Arginine / Q000235:genetics*; D001481:Basal Metabolism / Q000235:genetics; D002153:Calorimetry, Indirect; D004734:Energy Metabolism / Q000235:genetics*; D005260:Female; D005502:Food; D005787:Gene Frequency; D014644:Genetic Variation; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D009765:Obesity / Q000235:genetics*; D022702:Receptors, Adrenergic, beta-3 / Q000235:genetics*; D014364:Tryptophan / Q000235:genetics
chemical_list: D022702:Receptors, Adrenergic, beta-3; D014364:Tryptophan; D001120:Arginine