Adrenergic Modulation of Glucagon and Insulin Secretion in Obese and Lean Humans

Abstract

The adrenergic modulation of immunoreactive insulin (IRI) and glucagon (IRG) secretion was studied in 5 massively obese subjects. Epinephrine was infused alone or in combination with propranolol, a .beta. adrenergic blocking drug, or with phentolamine, an .alpha. adrenergic blocking drug. Epinephrine infusion produced a significant (P < 0.02) rise in IRG levels which was blocked by addition of either phentolamine or propranolol. Pure .alpha. adrenergic stimulation with propranolol-epinephrine infusion inhibited IRG secretion (P < 0.02). IRI levels decreased with propranolol-epinephrine infusion (P < 0.02), increased with phentolamine-epinephrine infusion, and were not affected by infusion of epinephrine alone. Glucose concentrations rose with all 3 infusions but were less with phentolamine-epinephrine. A control group of 4 lean outpatients on an ad lib diet demonstrated a similar pattern but the changes of IRG secretion were smaller than in the obese subjects and were not statistically significant. In obese humans IRI secretion is increased by .beta. adrenergic stimulation, is decreased by .alpha. adrenergic stimulation, and is unaffected by combined .alpha. and .beta. adrenergic stimulation. IRG secretion is stimulated by combined .alpha. and .beta. adrenergic stimulation, is inhibited by pure .alpha. adrenergic stimulation, and is unaffected by pure .beta. adrenergic stimulation.