EFFECTS OF PULSATILE DELIVERY OF BASAL GROWTH-HORMONE ON LIPOLYSIS INHUMANS

Growth hormone (GH) excess stimulates lipolysis, but its role in the h ierarchy of lipolysis regulation is not clear. We studied whether puls atile GH delivery is required for its lipolytic effect. With use of th e pancreatic clamp, eight subjects were randomized to three protocols: protocol A, GH deficiency; protocol B, constant GH infusion; protocol C, pulsatile GH delivery (same total GH as protocol B). Pulsatile GH was given in four consecutive bursts, with symmetric peak width (60 mi n), amplitude of 10.7 (men) and 15 (women) ng . kg(-1). min(-1), and p eak width at half-height of 15 min. Palmitate flux (PF) was measured a t baseline and in the last hour of each study with [H-3]palmitate. GH (ng/ml) decreased from similar to 3.5 to 2.0 in protocol A (P < 0.05), it remained between 3.2 and 4.0 in protocol B (P < 0.05), but in prot ocol C it fluctuated between similar to 2.7 and similar to 5.0 (P < 0. 05). Palmitate concentration (in mu mol/l) was similar to 150 at basel ine; it did not change in protocols A and B (137 +/- 17 and 136 +/- 12 , respectively) but increased to 198 +/- 16 (P < 0.05) in protocol C. PF (mu mol . kg(-1). min(-1)) was similar to 2.7 at baseline and did n ot change in protocol B (2.4 +/- 0.2); it decreased to 2.2 +/- 0.1 in protocol A (P < 0.05); it increased to 3.1 +/- 0.3 (P < 0.05) in proto col C. These experiments provide evidence that pulsatile secretion of GH is required for its lipolytic effect.