The intestinal peptide PEC-60 inhibits insulin secretion in the mouse and the rat

The newly discovered 60-amino-acid porcine intestinal peptide, PEC-60, shows a structural similarity to pancreatic secretory trypsin inhibitor. PEC-60 was recently demonstrated to inhibit glucose-stimulated insulin secretion from the perfused rat pancreas. We examined in this study whether the peptide affects basal and stimulated insulin secretion in vivo. Purified porcine PEC-60 was injected intravenously in mice at 1 or 8 nmol/kg alone or together with glucose (2.8 mmol/kg) or the cholinergic agonist carbachol (0.16 mumol/kg). PEC-60 was found to inhibit glucose- and carbachol-induced insulin secretion (p less than 0.01 and p less than 0.05, respectively) at 8 nmol/kg, whereas at 1 nmol/kg, the peptide had no effect. In contrast, basal plasma insulin levels were not affected by PEC-60. In a second experimental series, PEC-60 was infused intravenously in rats at 17 or 68 pmol/min alone or together with glucose (56 mumol/min). At 68 pmol/min (p less than 0.01), but not at 17 pmol/min, PEC-60 inhibited glucose-stimulated insulin secretion. The peptide had no influence on basal plasma insulin levels. It is concluded that the newly isolated intestinal peptide, PEC-60, inhibits stimulated insulin secretion under in vivo conditions both in the mouse and in the rat without affecting basal insulin secretion.