Glucose-dependent insulinotropic peptide

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Glucose-dependent insulinotropic peptide
Identifiers
Symbol(s)	GIP
Entrez	2695
OMIM	137240
RefSeq	NM_004123
UniProt	P09681
Other data
Locus	Chr. 17 q21.3-q22

Glucose-dependent insulinotropic peptide (GIP) is a member of the secretin family of hormones. GIP is derived from a 153-amino acid proprotein encoded by the GIP gene and circulates as a biologically active 42-amino acid peptide. It is synthesized by K cells, which are found in the mucosa of the duodenum and the jejunum of the gastrointestinal tract. Like all hormones, it is transported by blood. GIP receptors are seven-transmembrane proteins found on beta-cells in the pancreas.

GIP, along with glucagon-like peptide-1 (GLP-1), belong to a class of molecules referred to as incretins.

It was formerly called gastrointestinal inhibitory peptide or gastric inhibitory peptide and was believed to neutralize stomach acid to protect the small intestine from acid damage, reduce the rate at which food is transferred through the stomach, and inhibit the GI motility and secretion of acid. However, it was discovered that these effects are only achieved with higher-than-normal physiological level, and that these results naturally occur in the body through a similar hormone, secretin.

It is now believed that the function of GIP is to induce insulin secretion, which is primarily stimulated by hyperosmolarity of glucose in the duodenum. After this discovery, it was given the new name of glucose-dependent insulinotropic peptide, but retained the acronym "GIP." The amount of insulin secreted is greater when glucose is administered orally than intravenously.

GIP is also thought to have significant effects on fatty acid metabolism through stimulation of lipoprotein lipase activity in adipocytes.

[edit] Research Conducted

It has been found that Type 2 diabetics are not responsive to GIP. In a research involving knockout mice, it was found that absence of the GIP receptors correlates with resistance to obesity.