title: Effect of aging on beta-adrenergically mediated thermogenesis in men.
abstract: The age-dependent alterations in beta-adrenergically mediated thermogenesis were investigated in 11 young (mean +/- SE age: 21.9 +/- 0.5 yr) and 9 older (52.9 +/- 2.1 yr) men during intravenous infusion of the nonselective beta-agonist isoprenaline (Iso). The older men had higher basal plasma norepinephrine (327.7 +/- 35.8 vs. 159.0 +/- 18.2 pg/ml, P < 0.001) and epinephrine (75.1 +/- 18.1 vs. 29.1 +/- 5.3 pg/ml, P < 0.05) concentrations than the young. The beta-adrenergically mediated thermogenesis was diminished in the older men, as reflected by the significantly higher plasma Iso concentration needed to increase resting energy expenditure by 15% (236.1 +/- 51.0 vs. 107.6 +/- 11.4 pg/ml, P < 0.05). Additionally, both dose (39.4 +/- 6.6 vs. 19.1 +/- 1.5 ng . kg fat-free mass-1 . min-1, P < 0.01) and plasma concentration (332.2 +/- 59.1 vs. 119.3 +/- 14.0 pg/ml, P < 0.01) of Iso needed to increase resting heart rate by 25 beats/min were higher in older than in younger subjects, suggesting that the age-related decline in beta-adrenergic sensitivity is a generalized defect not related to a specific tissue or response. In conclusion, aging is associated with a diminished beta-adrenergically mediated thermogenesis. This blunted thermogenic response may contribute to a positive energy balance and thus promote increased fat storage and obesity.
authors.affiliation: Department of Human Biology, Maastricht University, 6200 MD Maastricht, The Netherlands.
authors.forename: D A
authors.initials: DA
authors.lastname: Kerckhoffs
authors.forename: E E
authors.initials: EE
authors.lastname: Blaak
authors.forename: M A
authors.initials: MA
authors.lastname: Van Baak
authors.forename: W H
authors.initials: WH
authors.lastname: Saris
mesh_terms: D000273:Adipose Tissue; D000318:Adrenergic beta-Agonists; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001481:Basal Metabolism; D001823:Body Composition; D001833:Body Temperature Regulation / Q000502:physiology*; D004734:Energy Metabolism; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
chemical_list: D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine