Incretins are intestinal peptides that are released after food intake and stimulate insulin secretion. Important examples include glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). In patients with type 2 diabetes mellitus, this incretin effect is reduced or completely absent.
The action of the enzyme GLP-1 consists of glucose-dependent stimulation of insulin secretion, delayed gastric emptying, and inhibition of glucagon release, which suppresses appetite and leads to weight loss (Herold 2020). The glucose-regulating and appetite-suppressing effects of GIP and GLP-1 have led to the development of incretin-based therapies for the treatment of type 2 diabetes and obesity; see also underGLP-1 receptor agonists.
Incretins act not only in the gut and on the pancreas, but also on the brain, the cardiovascular and immune systems, the kidneys, and adipose tissue, since incretin hormone receptors (GIPR and GLP-1R) are also present in these tissues. Immunologically, incretins act on macrophages, monocytes, B cells, and T lymphocytes, such as regulatory T cells, Th17 cells, CD8+ T cells, and NK cells. The resulting anti-inflammatory effect is significant for inflammatory skin conditions.