title: Chronic sympathetic attenuation and energy metabolism in autonomic failure.
abstract: The sympathetic nervous system regulates thermogenesis and energy homeostasis in humans. When activated it increases energy expenditure, particularly resting energy expenditure. Most human studies used acute infusion of β-blockers as a model to eliminate sympathetic stimulation and to examine the contribution of the sympathetic nervous system to energy metabolism and balance. Clinically, however, it is also important to assess the effect of chronic sympathetic attenuation on energy metabolism. In this context, we hypothesized that resting energy expenditure is decreased in patients with autonomic failure who, by definition, have low sympathetic tone. We measured 24-hour energy expenditure using whole-room indirect calorimeter in 10 adults with chronic autonomic failure (6 women; age, 64.9±9.1 years; body mass index, 25.2±4.4 kg/m(2)) and 15 sedentary healthy controls of similar age and body composition (8 women; age, 63.1±4.0 years; body mass index, 24.4±3.9 kg/m(2)). In 4 patients, we eliminated residual sympathetic activity with the ganglionic blocker trimethaphan. We found that, after adjusting for body composition, resting energy expenditure did not differ between patients with autonomic failure and healthy controls. However, resting energy expenditure significantly decreased when residual sympathetic activity was eliminated. Our findings suggest that sympathetic tonic support of resting energy expenditure is preserved, at least in part, in pathophysiological models of chronic sympathetic attenuation.
authors.affiliation: Division of Clinical Pharmacology and Autonomic Dysfunction Center, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. cyndya.shibao@vanderbilt.edu
authors.forename: Cyndya
authors.initials: C
authors.lastname: Shibao
authors.forename: Maciej S
authors.initials: MS
authors.lastname: Buchowski
authors.forename: Kong Y
authors.initials: KY
authors.lastname: Chen
authors.forename: Chang
authors.initials: C
authors.lastname: Yu
authors.forename: Italo
authors.initials: I
authors.lastname: Biaggioni
mesh_terms: D000368:Aged; D000886:Anthropometry; D015992:Body Mass Index; D002153:Calorimetry, Indirect; D016022:Case-Control Studies; D002908:Chronic Disease; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism; D009765:Obesity / Q000503:physiopathology; D010084:Oxidation-Reduction; D054970:Pure Autonomic Failure / Q000150:complications / Q000175:diagnosis*; D012016:Reference Values; D012146:Rest / Q000502:physiology; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D009638:Norepinephrine