Abstract
The effect of an infusion of norepinephrine (0.42 nmol.kg-1.min-1) on energy metabolism in the whole body (using indirect calorimetry and the arteriovenous forearm catheterization techniques in eight healthy young male adults. The activity of the triglyceride-fatty acid cycle, which mainly operates in nonmuscular tissues, was also assessed by measuring glycerol turnover using [2H5]glycerol (to indicate lipolysis) and indirect calorimetry (to indicate net fat oxidation). Norepinephrine increased whole body oxygen consumption by almost 10% (P <0.01), but the estimated oxygen consumption of muscles tended to decrease. Muscle blood flow (measured by 133Xe) and forearm blood flow (measured by strain-gauge plethysmography) were not significantly affected by norepinephrine, but the rate of uptake of nonesterified fatty acids and beta-hydroxybutyrate increased severalfold (P <0.05), whereas that of glucose did not. The activity of the triglyceride-fatty acid cycle increased fourfold after norepinephrine administration, having a marginal effect on resting energy expenditure (approximately 1.5%) but accounting for approximately 15% of the increase in whole body energy expenditure. This study provides no evidence that skeletal muscle is an important site for norepinephrine-induced thermogenesis and suggests that an increase in the activity of the triglyceride-fatty acid cycle contributes to the norepinephrine-induced increase in energy expenditure of nonmuscular tissues.
Original language | English |
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Pages (from-to) | E877-84 |
Number of pages | 8 |
Journal | American Journal of Physiology: Endocrinology and Metabolism |
Volume | 266 |
Issue number | 6 |
Publication status | Published - 1 Jun 1994 |
Keywords
- Adult
- Body Temperature
- Body Temperature Regulation
- Energy Metabolism
- Fatty Acids
- Fatty Acids, Nonesterified
- Forearm
- Glycerol
- Humans
- Male
- Muscles
- Norepinephrine
- Regional Blood Flow
- Skin Temperature