Physiology and pathophysiology of glucagon-like peptide-1 (GLP-1): the role of GLP-1 in the pathogenesis of diabetes mellitus, obesity, and stress.

Glucagon-like peptide-1 (GLP-1) is produced both in the human and rat intestine and brain. The release of GLP-1 into the blood is mediated by factors of neural and hormonal origin and is stimulated by the presence of nutrients in the digestive tract, while the enzyme dipeptidyl peptidase IV and the kidneys are responsible for, respectively, the rapid degradation and excretion of the hormone. Peripherally secreted GLP-1 enhances insulin synthesis and release and maintains the normal anatomical status of pancreatic islets. Diminished GLP-1 response to ingested food, associated with attenuated insulin release and glucose intolerance, was found in non-insulin-dependent diabetes mellitus. GLP-1 replacement in diabetic subjects normalized these parameters, thus indicating a role for this peptide in the pathogenesis of type 2 diabetes. GLP-1 might also be involved in the pathophysiology of obesity and stress to some extent. Both peripheral and central GLP-1 are probably involved in the control of feeding centers as an anorexic agent. GLP-1 affects the activity of the hypothalamo-pituitary-adrenal axis both under basal and stress conditions, including taste aversion learning. Hence, GLP-1-dependent pathophysiological mechanisms may participate in the pathogenesis of the most common metabolic and behavioral disorders.