Incretin: Difference between revisions

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{{Short description|Group of gastrointestinal hormones}}

[[Image:Incretins and DPP 4 inhibitors.svg|thumb|350px|right|GLP-1 and DPP-4 inhibitors]]

'''Incretins''' are a group of [[metabolic]] [[hormone]]s that stimulate a decrease in blood glucose levels. Incretins are released after eating and augment the secretion of [[insulin]] released from pancreatic [[beta cells]] of the [[islets of Langerhans]] by a [[blood glucose|blood-glucose]]–dependent mechanism.

Some incretins ([[GLP-1]]) also inhibit [[glucagon]] release from the [[alpha cell]]s of the [[islets of Langerhans]]. In addition, they slow the rate of absorption of nutrients into the blood stream by reducing gastric emptying and may directly reduce food intake. The two main candidate peptides that fulfill criteria for an incretin are the intestinal [[peptide]]s [[glucagon-like peptide-1]] (GLP-1) and [[gastric inhibitory peptide]] (GIP, also known as: glucose-dependent insulinotropic polypeptide). GIP is produced and secreted into the blood circulation by [[Enteroendocrine cell#K cell|K cells]], i.e., single cells located in the mucosa of the [[upper gastrointestinal tract]]'s [[duodenum]] and upper [[jejunum]] while GLP1 is produced and secreted into the blood by [[Enteroendocrine cell#L cell|L cells]] located in the mucosa of the [[lower gastrointestinal tract]]s [[small intestine|small]] and [[large intestine]]s. [[Short-chain fatty acids]] (primarily [[acetic acid|acetic]], [[propionic acid|propionic]], and [[butyric acid]]s), which [[Microbiota|microganisms]] form in the intestines, bind to the [[FFAR2]] and [[FFAR3]] receptors on K cells and L cells to stimulate their respective production and secretion of GIP and GLP-1. Both GLP-1 and GIP are rapidly inactivated by the enzyme [[dipeptidyl peptidase-4]] (DPP-4) and are members of the glucagon peptide superfamily.

[[Medication]]s based on incretins are used in the treatment of [[diabetes mellitus type 2]].

Several long-lasting [[Glucagon-like peptide-1 receptor agonist|GLP-1 analogs]] having insulinotropic activity have been developed, and several, including [[dulaglutide]] (Trulicity), [[exenatide]] (Byetta), [[liraglutide]] (Victoza), [[semaglutide]] (Ozempic, Wegovy and Rybelsus) and exenatide extended-release (Bydureon), have been approved for use in the U.S.

Another approach is to inhibit [[dipeptidyl peptidase-4|DPP-4]], the enzyme that inactivates GLP-1 and GIP. Several [[DPP-4 inhibitors]] that can be taken orally as tablets have been developed.

The incretin effect describes the phenomenon whereby oral glucose intake elicits a higher insulin response compared to intravenously introduced glucose that produces the same levels of serum glucose levels.

In 1932, [[Belgians|Belgian]] [[physiologist]] Jean La Barre used the word "incretin" for a [[Gastrointestinal hormone|gut hormone]], which stimulates the [[Pancreatic islets|endocrine pancreas]] including [[insulin]] release. He also proposed that such incretins could be used as a treatment for diabetes mellitus.

* [[Secretin family]]

{{二次利用|date=3 March 2024}}

[[Category:Peptide hormones]]