Lipolytic responsiveness to epinephrine in nondiabetic and diabetic humans

To determine whether the sensitivity of adipose tissue lipolysis to catecholamines is increased in poorly controlled insulin-dependent diabetes, the lipolytic response to epinephrine was measured in seven nondiabetic volunteers and seven poorly controlled diabetic subjects with use of[1-C-14]palmitate as a tracer. Subjects received sequential l-h infusions of epinephrine, which produced epinephrine concentrations of similar to 1,000, similar to 1,750, similar to 3,500, and similar to 6,000 pmol/l. A pancreatic clamp was used to maintain constant plasma hormone levels. Concentration-response curves were constructed for each subject from the integrated lipolytic response during each epinephrine infusion. There was no difference in maximal lipolytic response (117 +/- 19 vs. 152 +/- 11 mu mol.kg(-1).h(-1)) or in maximally effective (3,171 +/- 267 vs. 3,357 +/- 349 pmol/l) or half-maximally effective (1,081 +/- 109 vs. 1,015 +/- 120 pmol/l) epinephrine concentrations between nondiabetic and diabetic subjects, respectively (all P = NS). In control subjects, maximum beta-hydroxybutyrate concentrations were achieved at lower epinephrine concentrations than those required for a maximum lipolytic effect. Thus, under pancreatic clamp conditions, the lipolytic response to epinephrine in nondiabetic and diabetic subjects was similar.