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Metabolic effects of an increase of sympathetic activity in healthy humans
L Tappy1, K Girardet, N Schwaller
1Institute of Physiology, Faculty of Medicine, Lausanne University, Switzerland.
Objective:
To determine the metabolic effects of catecholamines released at sympathetic nerves ending in the postabsorptive and postprandial states.
Design:
Sympathetic activity was acutely increased by lower body negative pressure (LBNP; -15 mmHg) on two occasions in a group of eight healthy volunteers: (1) in the postabsorptive state; and (2) after glucose ingestion.
Measurements:
Plasma norepinephrine concentrations were determined by HPLC and energy expenditure and substrate oxidation rates were assessed with indirect calorimetry.
Results:
After glucose, LBNP increased plasma norepinephrine by 27% and lipid oxidation by 72% and decreased glucose oxidation by 14%. Energy expenditure was not altered. In the postabsorptive state, LBNP increased plasma norepinephrine by 34%, but had no significant effect on energy or substrate metabolism.
Conclusions:
In healthy humans, LBNP-induced activation of the sympathetic nervous system decreases glucose oxidation and increases lipid oxidation after oral glucose, but does not quantitatively affect energy expenditure.