What is GLP-2?

GLP-2 stands for glucagon-like peptide 2. It is a short chain of 33 amino acids released by enteroendocrine cells in the lining of the small and large intestine after a meal. Its effects are almost entirely on the gut itself: it makes the lining grow, it helps the bowel absorb more of what passes through it, and it slows things down on the way. It is the reason a drug class exists for short bowel syndrome, a rare condition in which too little working intestine is left to absorb food and water.

It is also not GLP-1, and it does not do what GLP-1 drugs do. That distinction has its own page, GLP-2 vs GLP-1. And if you arrived here because someone online called tirzepatide "GLP-2", the slang page explains why that label is wrong.

Where it is made

GLP-2 comes from the same precursor protein as GLP-1, called proglucagon. In the pancreas, proglucagon is cut one way and produces glucagon. In the gut, specialised cells called L cells cut it another way and release GLP-1 and GLP-2 together, in the same moment, from the same cell. L cells are most dense in the last part of the small intestine (the terminal ileum) and the colon, which is why GLP-2 output rises after food reaches the lower gut.

That location matters clinically. People who have lost their terminal ileum and colon to surgery have little or no rise in GLP-2 after eating. In a 2001 study of eight such patients, the authors described them as having "no postprandial secretion of GLP-2". The missing gut peptide is part of why their remaining bowel struggles to adapt.

The 1996 discovery

For years GLP-2 was a peptide without a known function. The clue came from tumours. Some people with rare glucagon-producing tumours were found to have an unusually overgrown small bowel. In 1996, Daniel Drucker's group in Toronto showed that nude mice carrying proglucagon-producing tumours had marked growth of the small intestinal lining, traced the effect to GLP-2, and then gave GLP-2 itself to mice. Within four days it increased bowel weight, villus height in the jejunum and ileum, and crypt cell proliferation. The paper, in the Proceedings of the National Academy of Sciences, called GLP-2 an intestinal peptide that stimulates small bowel epithelial growth.

The receptor

In 1999 the same field cloned the GLP-2 receptor. It is a G protein-coupled receptor, closely related to the glucagon and GLP-1 receptors, and it is expressed mainly in the gut. Cells carrying it responded to GLP-2 but not to GLP-1 or other related peptides. That selectivity is the single most important fact on this page: GLP-1 and GLP-2 are siblings from the same gene, but they talk to different receptors.

The receptor is not on the dividing crypt cells that actually build new lining. It sits on other cell types in and under the gut wall, including enteric neurons and cells beneath the epithelium, and GLP-2 works largely through messengers those cells release. In mice, the growth effect needs IGF-1: mice lacking IGF-1 did not grow their small bowel in response to a standard GLP-2 dose. The blood flow and anti-inflammatory effects have been traced to nerve signals in the gut wall and nitric oxide. Most of this mechanism work is animal research.

What it does in the gut

• Grows the lining. Taller villi and deeper crypts mean more absorptive surface. In the 2001 human study, crypt depth and villus height increased in five and six of the eight patients.
• Improves absorption. In the same study, 35 days of GLP-2 injections raised energy absorption from 49.9% to 53.4% and wet weight absorption from 25% to 36%.
• Slows the stomach. Time to 50% gastric emptying of solids rose from 89 to 119 minutes.
• Increases intestinal blood flow and reduces gastric acid secretion, both listed in the teduglutide label's description of GLP-2.

Why the natural peptide cannot be a drug

Native GLP-2 is cut by the enzyme DPP-4 almost as soon as it enters the blood. In healthy volunteers, intact GLP-2 had an elimination half-life of 7.2 minutes. The inactive fragment, GLP-2 (3-33), lasted longer at about 27 minutes. A peptide that disappears in minutes needs repeated injections to work at all.

The fix was a one amino acid change. Teduglutide swaps the alanine at position 2 for glycine, which makes it resistant to DPP-4. Its half-life is about 2 hours in healthy people and 1.3 hours in people with short bowel syndrome, according to the FDA label, which is long enough for once daily dosing. Newer analogues, glepaglutide and apraglutide, are engineered to last long enough for twice weekly and once weekly injections.

What GLP-2 does not do

It is not an appetite peptide. In a randomised, blinded crossover study of 18 healthy adults, a 4.5 hour infusion of GLP-2 at physiological levels did not change hunger ratings or how much people ate at a buffet meal. In short bowel patients the direction of weight change is the opposite of a GLP-1 drug: in the 2001 study body weight rose 1.2 kg and lean mass 2.9 kg over 35 days, because more of the food eaten was being absorbed.

Timeline

Where to go next

The short bowel syndrome page explains the condition the drugs are made for and how trials measure success. The GLP-2 research page covers bone, gut barrier and other areas still under study. The GLP-2 hub lists every page in this section, and what are peptides covers the basics of the molecule class.

Keeping a record

If you are on a GLP-2 analogue, your care team will be tracking parenteral support volumes, weight, urine output and blood tests. A personal log of the daily injection, injection site, intake and weight on one timeline makes those reviews easier. Peptide AI's dose log, injection site rotation and bloodwork tracking keep those in one place.