AJP - Endocrinology and Metabolism, Vol 257, Issue 2 E185-E192, Copyright © 1989 by American Physiological Society
Epinephrine's effect on metabolic rate is independent of changes in plasma insulin or glucagon
M. A. Staten, D. E. Matthews, P. E. Cryer and D. M. Bier
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Epinephrine's effect to increase metabolic rate is accompanied by changes
in the plasma concentrations of insulin, glucagon, and metabolic
substrates. Because both glucagon and insulin have been reported to affect
thermogenesis, these hormones might contribute to or modify the thermogenic
response to epinephrine. To determine if the epinephrine-induced increase
in metabolic rate is secondary to changes in glucagon or insulin or to
changes in the fuels modulated by these hormones, metabolic rate was
measured by indirect calorimetry in five normal weight post-absorptive
young men on three occasions: study A, an intravenous epinephrine infusion
alone; study B, a 4-h "islet clamp" consisting of somatostatin infusion
with basal insulin and glucagon replacement; and study C, an intravenous
epinephrine infusion combined with the islet clamp. A 1-h base-line period
preceded 2 h of epinephrine infusion. During the 4-h islet clamp (study B),
metabolic rate and plasma concentrations of epinephrine, insulin, glucagon,
and glucose remained unchanged. During the infusion of epinephrine alone
(study A), metabolic rate and concentrations of glucagon, free fatty acids,
and C-peptide increased as expected. Also as expected, the glycemic
response to epinephrine infusion was much larger when insulin and glucagon
levels were fixed with the islet clamp (study C). In contrast, the
metabolic rate and the free fatty acid concentration responded similarly to
epinephrine infusion when insulin and glucagon were fixed (study C) and
when they were changing (study A). We conclude that epinephrine increases
metabolic rate independently of physiological changes in plasma glucagon or
insulin or the circulating fuels they modulate.
