Incretins are a group of gastrointestinal hormones that are naturally released in the body after eating. They stimulate the amount of insulin produced by the pancreas and also regulate other hormones involved in feeding and blood sugar control. The name Incretin seems weird but in fact the name has a long history dating back many decades when scientists were trying to isolate the gut hormones which regulate the pancreas. The name Incretin was proposed for a hormone extracted from the upper gastrointestinal tract and which increased insulin secretion and lowered blood sugar.
In the 1970’s the explosion of research on these so-called ‘gut hormones’ resulted in the discovery of one specific chemical messenger called GLP-1. Its action was very specifically to increase pancreatic insulin secretion. It therefore became the top target for drug researchers looking to develop a possible therapy for diabetes. Nowadays these Incretin based therapies have become one of the most commonly used drugs in diabetes treatment.
The group of drugs that have emerged over the years can be generally split into two distinct subgroups. Either they mimic the actions of GLP-1 (GLP-1 agonists) or they block the natural destruction of GLP-1 in the body (DPP-4 inhibitors). Either way the action of the drugs will be to increase GLP-1 hormone levels and this is their helpful function in diabetes therapy.
GLP-1 is an abbreviation for Glucagon Like Peptide-1. It is an intestinal hormone that developed its strange name after chemical analysis showed it to be related in structure to the hormone glucagon. It is released in the gut after eating and helps the pancreas secrete insulin for the control of blood glucose. This action needs to be timely and of short duration and we therefore have enzymes to chew up the GLP-1 after it has done its job.
The main enzyme is called DPP-4, this being an abbreviation for dipeptidyl peptidase-4. Since GLP-1 levels are reduced in Type 2 diabetes there has been an attempt to boost levels by blocking the natural DPP-4 action with enzyme inhibitors. The inhibition of this natural process raises the amount of GLP-1 available to stimulate the pancreas. Alternatively GLP-1 can be boosted by drugs that mimic the action of GLP-1, these are the so called GLP-1 agonists.
The GLP-1 agonists are protein hormones so they have to be injected just like insulin. The DPP-4 inhibitors are tablets just like all the other oral hypoglycaemic agents used to treat diabetes.