Enhanced lipolysis from broiler adipocytes pretreated with pancreatic polypeptide

Broiler adipocytes in culture were used to determine whether prolonged preincubation with an antilipolytic hormone, pancreatic polypeptide, enhances lipolysis by inducing desensitization of lipolysis inhibition. Preincubation of broiler adipocytes with pancreatic polypeptide resulted in a dose-response and time-dependent enhancement (P < .05) of basal and glucagon-stimulated lipolysis. Lipolysis was enhanced at 4 and 24 h but not at .5 h of pretreatment. Acute inhibition of basal lipolysis was unaffected by long-term (24 h) exposure of adipocytes to a maximally effective dose (12 nM) of pancreatic polypeptide. Thus, desensitization of lipolysis inhibition cannot explain the enhanced lipolysis from pancreatic polypeptide-treated adipocytes. However, preincubation with 12 nM pancreatic polypeptide for 24 h reduced (P < .05) pancreatic polypeptide and somatostatin inhibition of lipolysis stimulated by glucagon. Moreover, basal lipolysis and submaximal lipolysis were enhanced to a similar extent (27 vs 29 nmol/h) but to a greater (P < .05) extent (27 vs 13 nmol/h) than maximal lipolysis when adipocytes were exposed to 12 nM pancreatic polypeptide for 24 h. These results suggest that the enhanced lipolysis induced by prolonged exposure of adipocytes to pancreatic polypeptide resulted from increased activity of hormone-sensitive lipase and activators of this enzyme and not from attenuation of lipolysis inhibition.