Annu Rev Physiol. 1997;59:257-71. doi: 10.1146/annurev.physiol.59.1.257.


The gene encoding proglucagon, the biosynthetic precursor of glucagon, is expressed not only in the pancreatic islets but also in endocrine cells of the gastrointestinal mucosa. The proglucagon (PG)-derived peptides from the gut include glicentin (corresponding to PG 1-69); smaller amounts of oxyntomodulin (PG 33-69) and glicentin-related pancreatic polypeptide (GRPP, PG 1-30); glucagon-like peptide-1 (GLP-1, PG 78-107 amide); intervening peptide-2 (IP-2, PG 111-122 amide); and glucagon-like peptide-2 (GLP-2, PG 126-158). All are secreted into the blood in response to ingestion of carbohydrates and lipids. Only oxyntomodulin and GLP-1 have proven biological activity; oxyntomodulin possibly because it interacts (but with lower potency) with GLP-1 and glucagon receptors. GLP-1 is the most potent insulinotropic hormone known and functions as an incretin hormone. It also inhibits glucagon secretion and, therefore, lowers blood glucose. This effect is preserved in patients with non-insulin-dependent diabetes mellitus, in whom infusions of GLP-1 may completely normalize blood glucose. However, GLP-1 also potently inhibits gastrointestinal secretion and motility, and its physiological functions include mediation of the "ileal-brake" effect, i.e. the inhibition of upper gastrointestinal functions elicited by the presence of unabsorbed nutrients in the ileum. As such it may serve to regulate food intake.

Publication types

  • Review

MeSH terms

  • Animals
  • Glicentin
  • Glucagon / metabolism
  • Glucagon / physiology
  • Glucagon-Like Peptide 1
  • Glucagon-Like Peptide 2
  • Glucagon-Like Peptides / physiology*
  • Humans
  • Intestinal Mucosa / metabolism
  • Oxyntomodulin
  • Peptide Fragments / metabolism
  • Peptide Fragments / physiology
  • Peptides / physiology
  • Proglucagon
  • Protein Precursors / metabolism
  • Protein Precursors / physiology


  • Glucagon-Like Peptide 2
  • Oxyntomodulin
  • Peptide Fragments
  • Peptides
  • Protein Precursors
  • Proglucagon
  • Glucagon-Like Peptides
  • Glicentin
  • glicentin-related pancreatic peptide
  • Glucagon-Like Peptide 1
  • Glucagon