incretin hormones

Last reviewed 01/2018

• a potential role for intestinal peptides in the regulation of postprandial insulin secretion was based on the observation that insulin responses to an oral glucose load exceeded those measured after intravenous administration of an equivalent amount of glucose - this was termed the 'incretin effect'
• the 'incretin effect' is attributed to the insulinotropic action of gut hormones
  • especially glucagon-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) - these hormones are secreted by specialised enteroendocrine cells in response to a meal
  • studies have shown that type 2 diabetes exhibit significant reductions in the levels of meal-stimulated, circulating GLP-1 compared to healthy individuals
  • glucoregulatory effects in patients with type 2 diabetes has been achieved via the exogenous administration of GLP-1 - however the short plasma half-life (< 2 minutes) limits the potential of subcutaneous GLP-1 - GLP-1 is rapidly degradaded by the ubiquitous aminopeptidase enzyme, dipeptidyl peptidase-IV
    
    
• incretin hormones promote insulin secretion and inhibit glucagon secretion when blood glucose is high; when blood glucose is low then insulin secretion is inhibited and glucagon secretion is promoted

Reference:

1. Perley M, Kipnis DM. Plasma insulin responses to oral and intravenous glucose: studies in normal and diabetic subjects. J Clin Invest 1967;46: 1954-62