In:
Journal of Endocrinology, Bioscientifica, Vol. 206, No. 3 ( 2010-07-1), p. 307-315
Abstract:
Sedentary behavior is associated with an attenuated thermogenic response to β-adrenergic receptor (β-AR) stimulation, an important regulator of energy expenditure (EE) in humans. Chronic stimulation of β-ARs, via heightened activity of the sympathoadrenal system, leads to diminished β-AR function. We have investigated the hypothesis that the thermogenic response of sedentary adults to β-AR stimulation will be increased during short-term sympathoadrenal inhibition. Using a randomly ordered, repeated measures study design, resting EE (REE; indirect calorimetry, ventilated hood technique) and the % increase in EE above REE (%ΔEE) during acute i.v. isoproterenol administration (nonselective β-AR agonist; 6, 12, and 24 ng/kg fat-free mass per min) were determined in 16 sedentary adults (nine females and seven males, 25±1 years, body mass index: 26.1±0.9 kg/m 2 , maximal oxygen uptake: 40±2 ml/kg per min (mean± s.e.m. )) in the basal state and on the 6th day of transdermal clonidine administration (centrally acting α2-AR agonist; 0.2 mg/day). Relative to baseline, clonidine inhibited sympathoadrenal activity, as evidenced by decreased plasma norepinephrine concentration (1.04±0.13 vs 0.34±0.03 nmol/l; P 〈 0.001), skeletal muscle sympathetic nerve activity (22.5±3.8 vs 8.5±1.9 bursts/min; P =0.003), and resting heart rate (63±2 vs 49±1 beats/min; P 〈 0.001). Sympathoadrenal inhibition decreased REE (6510±243 vs 5857±218 kJ/day; P 〈 0.001), increased respiratory exchange ratio (0.84±0.01 vs 0.86±0.01; P =0.03), and augmented the thermogenic response to β-AR stimulation (%ΔEE: 11±2, 16±2, and 24±2 vs 14±1, 20±2, and 31±2; P =0.04). These data demonstrate that in sedentary humans, short-term inhibition of sympathoadrenal activity increases the thermogenic response to β-AR stimulation, an important determinant of EE and hence energy balance.
Type of Medium:
Online Resource
ISSN:
0022-0795
,
1479-6805
Language:
Unknown
Publisher:
Bioscientifica
Publication Date:
2010
detail.hit.zdb_id:
1474892-7
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