GLP-1; incretin; glucagon-like peptide
Glucagon-like peptide 1 belongs to a family of hormones called the incretins, so-called because they enhance the secretion of insulin due to factors derived from the gut. Glucagon-like peptide 1 is a product of a molecule called pre-proglucagon, a polypeptide (i.e. chain of amino acids, which are organic compounds that make up proteins) that is split to produce many hormones, including glucagon. Because they come from the same source, these hormones share some similarities, so are called ‘glucagon-like’. Cells found in the lining of the small intestine (called L-cells) are the major source of glucagon-like peptide 1, although it is also secreted in smaller quantities by the pancreas and the central nervous system. Glucagon-like peptide 1 encourages the release of insulin from the pancreas, increases the volume of cells in the pancreas that produce insulin (beta cells) and reduces the release of glucagon. Glucagon-like peptide 1 also increases the feeling of fullness during and between meals by acting on appetite centres in the brain and by slowing the emptying of the stomach.
Food is the main stimulus of glucagon-like peptide 1 release, with increased hormone levels detectable after 10 – 15 minutes of starting to eat and remaining raised in the blood circulation for several hours after that. Apart from food, stimulation of nerve activity and other hormones can affect glucagon-like peptide release. The hormone somatostatin reduces the production of glucagon-like peptide 1. Glucagon-like peptide 1 is rapidly broken down by an enzyme called dipeptidyl peptidase-4.
There are no known cases of too much glucagon-like peptide 1. Drugs have been developed to behave like glucagon-like peptide 1 in the blood circulation to improve the control of glucose levels in type-2 diabetes. These drugs are known as GLP-1 analogues. Levels of glucagon-like peptide 1 are also naturally increased after some types of weight-related surgery, which is thought to contribute to the observed weight loss and improvement of type-2 diabetes in patients who have had these types of surgery. Recently one of these GLP-1 analogues (Liraglutide) has been approved for the treatment of obesity in the UK and other countries. Research studies are investigating other GLP-1 analogues, and these may also be approved for the treatment of obesity in the future.
It has been suggested that too little glucagon-like peptide 1 released after a meal may increase the likelihood of, or worsen, obesity. Since glucagon-like peptide 1 reduces appetite after a meal, if the body releases less of this hormone, individuals may eat more during a meal and are more likely to snack between meals.
Last reviewed: Jan 2022