GLP-1, a powerful physiological incretin: an update

Food intake, especially carbohydrates, release incretin, which is an endocrine transmitter. Among the various endocrine modulators, Glucagon-like peptide 1 (GLP-1) is more effective in stimulating the release of insulin and more powerful regulator of physiological functions. Mainly (GLP-1) receptors are expressed in lungs, α and β cells of pancreatic islets and the nervous system. Peripheral tissues, gastrointestinal tract and extra pancreatic tissues i.e., vascular smooth muscle, kidney and heart, also contain high affinity receptors for GLP-1. The aim of this systematic review was to gather the available published evidence of the functions performed by GLP-1 through the activation of its receptor in various organs. This review suggest that GLP-1 receptor signaling helps prevent beta cell apoptosis and conserve function and morphology of human islet. The effect of GLP-1 signaling in weight loss in diabetic patients was proved by previous studies. The long term use of GLP-1 receptor agonists reduces cardiovascular and renal complications in diabetic patients. Significant evidence was found in previous literature for its effect on pancreatic secretions. The secretions of many enzymes and hormones, such as trypsin, lipase and glucagon, inhibited significantly while the increase in levels of insulin and somatostatin was reported in many studies. GLP-1 has a prominent role in cardiac functioning and increases the heart rate considerably. Based on the vast impact of GLP-1 on physiological functions, many GLP-1 receptor agonists can be made that can increase the healthy life span.