Summary of peptides for gastrointestinal studies

1. Motilin

Motilin is a 22-amino-acid hormone, released by the enteroendocrine M cells of the duodenum and proximal jejunum.

2. Gastrin

Gastrin is produced by G cells located in the gastric antrum and is the primary endocrine regulator of the secretory phase of a protein meal. The main function of gastrin is to stimulate gastric acid secretion, promote gastrointestinal motility, and participate in the maintenance of iron homeostasis. At the same time, gastrin can also stimulate the secretion of the pancreas, bile, and intestinal juice, and further decompose the food in the small intestine, which is beneficial to the absorption of nutrients in the small intestine.

3. Bombesin

Bombesin (BBS) is a 14-amino-acid peptide first isolated from the skin of the frog, Bombina bombina, in 1970 by Erspamer. It stimulates the release of gastrin and pancreatic enzymes and causes contraction of the gallbladder.

4. Tachykinin

The tachykinins are a family of small peptides sharing a common C-terminal sequence, Phe-Xaa-Gly-Leu-Met-NH2, whose main members are SP, neurokinin A, and neurokinin B.

5. Somatostatin

Somatostatin belongs to the expanding family of small regulatory peptides which exert a variety of actions in different organ systems throughout the body.

6. Vasoactive intestinal peptide (VIP) and related peptides

The vasoactive intestinal polypeptide (VIP) is a member of a family of homologous neuro- and endocrine peptides which has three separate groups distinguished by the receptors which recognize them.

7. Neurotensin

Neurotensin is a 13–amino acid peptide originally detected in the bovine hypothalamus. Neurotensin can protect the airway from gastric mucosal injury caused by cold stimulation and can inhibit gastric acid secretion.

8. Cholecystokinin

Cholecystokinin is secreted by cells of the upper small intestine. Its secretion is stimulated by the introduction of hydrochloric acid, amino acids, or fatty acids into the stomach or duodenum.

9. Secretin

Secretin is a gastrointestinal peptide and a member of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily Sherwood et al.

10. Pancreatic polypeptide

Pancreatic polypeptide (PP) is a 36–amino acid, 4.2-kDa polypeptide secreted by the islet F cells. PP belongs to the peptide YY/neuropeptide Y family of polypeptides.

11. Peptide YY

Peptide YY (PYY) is a 36-amino-acid gut hormone released by L cells of the ileum/colon in proportion to ingested calories. PYY is functionally related to NPY and binds to the Y family of receptors, Y1R–Y6R.

12. Neuropeptide Y

Neuropeptide Y (NPY) is a vasoconstricting peptide that is released together with NE from sympathetic nerve endings.

13. Opioid peptide

Opioid peptides are the endogenous ligands at opioid receptors.

14. Gastric Inhibitory Polypeptide

GIP is a 42-amino-acid peptide hormone encoded by a single gene. GIP mRNA is expressed only in the gut, specifically in the K cells, the majority of which are located in the proximal duodenum.