Effect of glicentin-related peptides on glucagon secretion in anaesthetized dogs

Recent studies have demonstrated that glicentin is released during nutrient ingestion. However, the biological function of glicentin remains unclear. In order to clarify the role of glicentin in the enteroinsular axis, the effect of glicentin-related peptides was investigated using in vivo local circulation of canine pancreas. Peaks I and II of gut glucagon-like immunoreactivity, partially purified from porcine intestinal extract by affinity chromatography and gel filtration, synthesized hexadecapeptide of N-terminal glicentin (1-16) and synthesized octapeptide of C-terminal glicentin (62-69) were administered for 10 min into the pancreaticoduodenal artery of canine pancreas. Blood samples were then drawn from the pancreaticoduodenal vein. The administration of peak I of glucagon-like immunoreactivity during arginine infusion in a dosage of 20 ng reduced the glucagon secretion by 42 pmol/l (p less than 0.05), whereas peak II of glucagon-like immunoreactivity (20 ng) slightly increased the plasma level of insulin, although not significantly. The administration of glicentin (1-16) in a dosage of 400 ng during saline infusion did not alter the plasma insulin level, but reduced the plasma glucagon level in the pancreaticoduodenal vein by 29 pmol/l (p less than 0.05). In addition, glicentin [62-69] in a dosage of 400 ng exerted a decrease in both the plasma insulin (40 mU/l, p less than 0.05) and glucagon level (27 pmol/l, p less than 0.05). The present study demonstrates the suppression of pancreatic glucagon release during the infusion of peak I glucagon-like immunoreactivity and N- or C-terminal glicentin-related peptide. Therefore, it is suggested that glicentin released during nutrient intake might inhibit the secretion of glucagon.