Abstract
Incretin hormones are peptides that are secreted from endocrine cell of gastrointestinal tract after nutrient ingestion and stimulate insulin secretion. Glucosodependent Insulinotropic Peptide - GIP is released from K-cells of duodenum and proximal jejunum, recently GIP synthesis has been proved in pancreatic alfa cells.
Besides the incretin effect causes GIP increased lipogenesis and decreased lipolysis in fat tissue, increased bone formation and decreased resorption and has protective and proliferative effect on CNS neurons. Both GIP agonists and antagonists are being study.
Another incretin hormone is derived in intestinal L-cells by posttranslational processing of proglucagon - glucagon-like peptides 1 and 2. GLP-1 stimulates insuline production and inhibits glucagon secretion, exerts proliferative and antiapoptotic effect on beta-cells.
Via receptors on vagal nerve and central mechanisms decreases food intake and decreases body weight. By deceleration of gastric emptying is attenuates increases in meal-associated blood glucose levels.
It exerts cardioprotective effects. GLP-1 receptors have been proved in liver recently but decrease liver glucose production and increased glucose uptake by liver and muscle are mediated indirectly by altering insulin and glucagon levels.
GLP-2 stimulates enterocytes proliferation, up-regulates intestinal nutrient transport, improves intestinal barrier function, and inhibits gastric and intestinal motility. GLP-2 also reduces bone resorption.