Alternative names for glucose-dependent insulinotropic peptide

GIP; incretin; gastric inhibitory polypeptide; glucose-dependent insulinotropic polypeptide

What is glucose-dependent insulinotropic peptide?

Glucose-dependent insulinotropic peptide is a hormone released from the small intestine that enhances the release of insulin following the intake of food. It is a member of the family of hormones known as the incretins of which the other main member is the hormone glucagon-like peptide 1.

Glucose-dependent insulinotropic peptide is made and secreted mainly from the upper section of the small intestine from a specific type of cell known as the K cell. Its main action occurs in the pancreas where it targets beta cells, which produce insulin. Glucose-dependent insulinotropic peptide stimulates the release of insulin from the beta cells in the pancreas in order to maintain low blood sugar levels after eating. It also increases the production of these cells and reduces the rate at which they break down.

Although this is the main function of glucose-dependent insulinotropic peptide, receptors for glucose-dependent insulinotropic peptide are also found in other organs of the body where it has several other effects:

• In the brain – glucose-dependent insulinotropic peptide stimulates the growth of cells that have the ability to divide and eventually develop into nerve cells.
   
• In bone – glucose-dependent insulinotropic peptide increases the formation of bone whilst decreasing bone breakdown.
   
• Fat tissue – glucose-dependent insulinotropic peptide is known to increase the amount of fat in the body by increasing the formation of fat cells.

How is glucose-dependent insulinotropic peptide controlled?

The main trigger for glucose-dependent insulinotropic peptide release is food, in particular fatty foods or those foods that are rich in sugar. Once released into the bloodstream, levels of glucose-dependent insulinotropic peptide do not remain high for very long. It is broken down quite quickly (after about seven minutes) and therefore does not remain in the circulating blood for long. Glucose-dependent insulinotropic peptide release is prevented by the hormone somatostatin, produced in the pancreas and gastrointestinal tract.

What happens if I have too much glucose-dependent insulinotropic peptide?

There are currently no known direct causes of too much glucose-dependent insulinotropic peptide. However, increased levels of glucose-dependent insulinotropic peptide have been linked to both type 2 diabetes mellitus and obesity. In type 2 diabetes mellitus, some patients have increased levels of glucose-dependent insulinotropic peptide but it is not known whether this is a cause or consequence of the condition. In type 2 diabetes mellitus, glucose-dependent insulinotropic peptide does not function as well as it should so it is less efficient at stimulating insulin release. This means patients have high blood sugar (hyperglycaemia), which worsens their existing type 2 diabetes mellitus. 

With obesity, scientists believe that by eating too much fatty foods there is an over-production of glucose-dependent insulinotropic peptide meaning that more fat tissue is produced.

What happens if I have too little glucose-dependent insulinotropic peptide?

Currently there are no known consequences of having too little glucose-dependent insulinotropic peptide.