Epinephrine mediates facultative carbohydrate-induced thermogenesis in human skeletal muscle.
The thermic effect of carbohydrate has a component mediated by the sympathoadrenal system but of unknown anatomical localization. We have studied the contribution of skeletal muscle to the thermic effect of a carbohydrate-rich natural meal (115 g of carbohydrate, approximately 80% of energy) by means of the forearm technique on two occasions, with and without intravenous beta-blockade with propranolol. The meal-induced thermogenesis was reduced from 9.6 to 7.1% by beta-blockade (P less than 0.04), the major difference was found 90 to 240 min after the meal. The postprandial increments in plasma glucose and lactate did not change by beta-blockade, but there was a trend toward a decreased insulin response (P = 0.06). The carbohydrate-induced increase in forearm oxygen consumption was reduced by 23% after beta-blockade (P less than 0.05), the entire difference being present 90-180 min postprandially and coinciding with the peak in arterial epinephrine. The present study provides evidence of a facultative thermogenic component in skeletal muscle, mediated by epinephrine via beta 2-adrenoreceptors. However, it also points to a nonmuscle component mediated through beta 1-adrenoceptors by norepinephrine released from the sympathetic nervous system. Consequently, the sympathoadrenal system seems to play a physiological role in the daily energy balance.
Astrup
A
A
Research Department of Human Nutrition, Royal Veterinary and Agricultural University, Frederiksberg, Copenhagen.
Simonsen
L
L
Bülow
J
J
Madsen
J
J
Christensen
N J
NJ
D000328:Adult; D001833:Body Temperature Regulation / Q000187:drug effects*; D002241:Carbohydrates / Q000494:pharmacology*; D004837:Epinephrine / Q000378:metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000378:metabolism / Q000502:physiology
D002241:Carbohydrates; D004837:Epinephrine