Changes in lipolytic sensitivity following repeated epinephrine infusion in humans

The lipolytic response to epinephrine is increased in lean but not obese subjects during conditions of increased circulating catecholamines such as starvation and critical illness. We evaluated the effect of repeated epinephrine treatment (0.03 μg · kg^-1 · min^-1 for 30 min thrice daily) on basal lipolysis and the lipolytic response to epinephrine in lean and obese subjects. Lipolytic rates were determined using [²H₅]glycerol during basal conditions and 60 min of epinephrine infusion before and after 6 days of repeated epinephrine treatment. Basal lipolysis and the lipolytic response to epinephrine were higher in obese (2.47 ± 0.51 pmol · kg^-1 · min^-1 and 106 ± 21 μmol/kg, respectively) than lean (1.45 ± 0.15 μmol · kg^{- 1} · min^-1 and 70 ± 12 μmol/kg, respectively; P = 0.08 obese vs. lean) subjects. Repeated epinephrine treatment decreased basal glycerol rate of appearance and the lipolytic response to epinephrine in lean and obese subjects. Plasma insulin concentration increased after repeated epinephrine treatment in both obese (14.3 ± 0.6 to 18.2 ± 1.6 μU/ml; P < 0.05) and lean (8.4 ± 1.3 to 11.1 ± 1.5 μU/ml; P < 0.01) subjects. Repeated epinephrine treatment suppresses basal and epinephrine-stimulated lipolysis. Increased plasma insulin concentration may be the mechanism.