GLP-2 and GIP both increase intestinal blood flow in rats, but not through the expected nitric oxide or VIP pathways, pointing to an unknown mechanism.
Independent of NO and VIPThe intestinal blood flow increase from GLP-2 and GIP persisted even when the two most likely signaling pathways were blocked
What the researchers found
Both GLP-2 and GIP independently increased blood flow through the superior mesenteric artery (the main blood vessel feeding the intestines) in anesthetized rats. Surprisingly, this effect did not depend on nitric oxide or vasoactive intestinal peptide — two of the most commonly assumed mediators of gut blood flow. Combining the two peptides or using a novel dual GIP/GLP-2 co-agonist did not produce a synergistic (greater-than-additive) effect. The GLP-2 receptor antagonist GLP-2(3-33) successfully blocked GLP-2's blood flow effect, confirming it acts through the GLP-2 receptor.
Why it matters
After you eat a meal, blood flow to your intestines increases dramatically to help absorb nutrients. GLP-2 and GIP are gut hormones released after eating that were suspected of driving this response, but the mechanism wasn't clear. This study confirms both peptides boost intestinal blood flow and — importantly — rules out two of the most obvious pathways (nitric oxide and VIP), meaning there's an unknown mechanism at work. Understanding this could be relevant for conditions like short bowel syndrome, where GLP-2 analogs are already used as drugs.
How the study worked
Researchers used anesthetized male Sprague-Dawley rats with transit-time flow probes surgically placed on the superior mesenteric artery to directly measure blood flow in real time. They administered GLP-2, GIP, or a novel dual co-agonist and measured acute blood flow changes. To test potential mechanisms, they pre-treated rats with a nitric oxide synthase inhibitor (L-NAME) or a VIP receptor antagonist before giving the peptides. They also tested the GLP-2 receptor antagonist GLP-2(3-33).
Who was studied
Male Sprague-Dawley rats (animal study)
What this study cannot tell us
This was an animal study in anesthetized rats, which may not fully reflect how these peptides work in awake animals or humans. Anesthesia itself can affect cardiovascular responses. The study used male rats only, so sex-specific differences weren't explored. The doses used were pharmacological rather than physiological, and the acute timeframe doesn't capture longer-term vascular adaptations.
How to read the evidence
This is a well-controlled animal physiology study with direct blood flow measurement. It provides strong mechanistic evidence in rats but is preclinical — the findings need to be confirmed in humans before clinical conclusions can be drawn.
When this study was published
Published in 2025, this is very recent research that adds new mechanistic understanding to GLP-2 and GIP biology. The finding about NO-independent blood flow regulation challenges prevailing assumptions in the field.
The bigger picture
GLP-2 is already the basis of an FDA-approved drug — teduglutide (Gattex) — used to treat short bowel syndrome by promoting intestinal growth and nutrient absorption. Understanding how GLP-2 increases blood flow to the gut adds another piece to the puzzle of how this peptide works therapeutically. The finding that the mechanism is independent of nitric oxide is particularly surprising, since NO-mediated vasodilation is one of the best-understood pathways in vascular biology. Identifying the actual mechanism could lead to better-targeted therapies for gut diseases.
Questions still open
- What is the actual molecular pathway by which GLP-2 and GIP increase intestinal blood flow if not through NO or VIP?
- Does this blood flow effect contribute to the therapeutic benefit of teduglutide in short bowel syndrome patients?
- Would these findings differ in female rats or in conscious (non-anesthetized) animals?
Common questions
What is GLP-2 and how is it different from GLP-1?
Why does it matter that nitric oxide isn't involved?
Read the original research
GLP-2 and GIP acutely increase superior mesenteric artery blood flow in male rats, and the effect is independent of nitric oxide and vasoactive intestinal peptide.
Physiological reports, 13(23), e70699
Citation
Galsgaard, Katrine D; Hartmann, Bolette; Rosenkilde, Mette M; Holst, Jens J; Gasbjerg, Lærke S; Sørensen, Charlotte M. (2025). GLP-2 and GIP acutely increase superior mesenteric artery blood flow in male rats, and the effect is independent of nitric oxide and vasoactive intestinal peptide.. Physiological reports, 13(23), e70699. https://doi.org/10.14814/phy2.70699