Responses of vasoactive intestinal polypeptide, secretin, and human pancreatic polypeptide to glucose during fasting.

The plasma concentrations of vasoactive intestinal polypeptide (VIP) and secretin and the serum concentration of human pancreatic polypeptide (hPP) were measured in nine healthy subjects during a 4-day fast. The fast induced a considerable increase in the concentrations of VIP and secretin but only a small increase in the concentration of hPP. The intravenous infusion of 50 g glucose and the oral ingestion of 50 g glucose temporarily suppressed the high concentrations of VIP and secretin. Conversely, hPP responded with a slight decrease in blood concentration after the intravenous infusion and with a modest increase after the oral ingestion. The study shows that glucose suppresses the high blood concentrations of VIP and secretin during starvation independent of the route of glucose administration. In addition, the results indicate that the blood concentration of hPP is not directly related to the blood glucose concentration during prolonged fasting.