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GIP(Gastric Inhibitory Polypeptide)

A. Structure

Like VIP, GIP is a peptide having 43 amino acids.


B.
Site

It is produced by K cells in the duodenum and jejunum in the presence of glucose and fat.

 

C. Actions

  • inhibits gastric juice secretion and motility; hence called GIP. However, this action of GIP is seen only in high (supraphysiological) doses stimulates insulin secretion.
  • Response to oral glucose
  • On giving oral glucose, GIP gets secreted and in turn causes release of insulin from the beta cells of the pancreas. For this reason, GIP is also called as glucose-dependent insulinotropic polypeptide
  • the hormones gastrin, CCK, secretin, and glucagons) are also known to release insulin; however, on giving oral glucose, they do not get secreted in enough amounts to cause insulin release
  • the hormone called GLP –1 (7 –36) is a glucagon derivative. In response to oral glucose, it gets secreted from GIT; in turn it causes release of insulin. Its action in releasing insulin is more potent than that of GIP. 

MCQ Tip
The GIT hormones, which release significant insulin on giving oral glucose are GIP and GLP-1 (7-36)

 
D. Motilin
  1.  Structure: Motilin is a polypeptide having 22 amino acids.
  2. Site: It is secreted by enterochromaffin cells and Mo cells in the stomach, small intestine and colon.

C. Action

  1. contraction of the smooth muscles of the stomach and intestine
  2. it is the main regulator of the migrating motor complexes (MMCs); MMCs control the gastrointestinal motility between meals (i.e. in the inter-digestive phase). The blood level of motilin increases at intervals of about 100 minutes in the inter-digestive phase.

MCQ tip
The GIT hormones, which release significant insulin on giving oral glucose are GIP and GLP-1 (7-36)





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