Maintaining proper blood sugar levels is an essential function of a healthy body. Glucagon-like peptide-1 (GLP-1) is a molecule consisting of a short chain of 30 amino acids that assists the body in this process. Primarily, this peptide hormone is made in specialized gut cells called intestinal L cells. Not only does GLP-1 play an important role in daily functioning, but it also may be useful as a basis for diabetes treatments.
When nutrients such as proteins and carbohydrates are available in the small intestine, L cells begin to produce GLP-1. Initially, glucagon-like peptide-1 is manufactured in an inert form called proglucagon. The active form is available only after having part of proglucagon's amino acid chain cleaved by the cell.
Once these cells have produced GLP-1 and released it into the bloodstream, this compound acts quickly to cause certain changes in the cells of the pancreas. GLP-1 causes cells to produce insulin, a hormone that causes cells to take up sugars to use for energy. Additionally, glucagon-like peptide-1 deters cells from producing glucagon, another hormone that impels cells to release sugars into the bloodstream. The net effect of these actions is to decrease blood glucose levels, and to prevent the body from experiencing hyperglycemia, a condition caused by an over-abundance of glucose circulating in the body.
Several other actions of GLP-1 contribute to lower blood glucose levels, including increasing some cells' sensitivity to insulin. It also promotes a feeling of fullness, or satiety, in the brain, and prevents the stomach from emptying into the intestines. These actions also serve to lower overall blood sugar levels, albeit in a more indirect fashion than the actions promoting insulin production.
Monitoring blood sugar levels and keeping them stable is an ongoing activity that requires the ability to rapidly respond to sudden changes. For this reason, the GLP-1 peptide has a simple, compact structure allowing it to be easily produced and degraded, as needed. After being secreted, glucagon-like peptide-1 is broken down by another enzyme within about two minutes. The short half-life of this peptide allows the body to respond to constant changes in glucose levels, and prevents feedback loops of decreasing blood glucose.
People with type II diabetes have smaller amounts of glucagon-like peptide-1. Researchers believe that this peptide's actions make it a useful starting point for treating this disease. Clinical trials using a compound called exendin, which exhibits similar effects as GLP-1, has shown this to be effective at maintaining lower blood glucose levels.