Candidate GI Hormone: Enteroglucagon
Enteroglucagon is secreted by intestinal mucosal cells, with the highest concentrations occuring in the distal small bowel and colon. Pancreatic glucagon is a 29-amino acid peptide secreted by the alpha cells of the pancreas. Enteroglucagon is a larger molecule. It has 37 amino acids and differs from pancreatic glucagon in having a C-terminal octapeptide extension. A possible hormonal role is suggested by the observation that it is released following ingestion of a mixed meal. Intraluminal glucose and fat cause its release, with glucose being the more potent stimulus. It has the same metabolic effects as pancreatic glucagon, ie, stimulation of glycogenolysis and gluconeogenesis, lypolysis, and ketogenesis, but it is much less potent than the pancreatic form. Neither pancreatic glucagon nor enteroglucagon have been clearly demonstrated to have physiologic effects on GI function. It may play a role in inhibiting gastrin release and gastric acid secretion and in regulating intestinal cell turnover, but a physiologic role for these actions has not been established.