Mouse study finds blocking GIP receptors depends on GLP-1 signaling, unlike tirzepatide's GIP activation
The mouse findings explain how two opposite approaches to the same receptor can both reduce weight, but no human data on GIP receptor blockers exist and nothing changes for people taking approved medicines.
A study in male mice published in Nature Metabolism reports that blocking the GIP receptor lowers body weight and food intake through a different mechanism than activating the same receptor, and that the blocking effect requires a working GLP-1 receptor [1].
GIP stands for glucose-dependent insulinotropic polypeptide. Drugs such as tirzepatide (Mounjaro, Zepbound) activate both the GIP receptor and the GLP-1 receptor; that dual activation is the basis of the co-agonism strategy used to treat obesity and type 2 diabetes [1]. GIP receptor antagonists do the opposite: they block the receptor. Earlier work in diet-induced obese mice and in non-human primates found that antagonists also lower body weight and food intake, particularly when combined with a GLP-1 receptor agonist [1].
The new experiments tested whether antagonism works the way agonism does. It does not. The body weight and food intake effects of GIP receptor antagonism disappeared in mice with a global loss of either the Gipr gene or the Glp-1r gene [1]. But when the researchers removed Gipr only from GABAergic neurons in the central nervous system, or from peripherin-expressing neurons in the peripheral nervous system, the effects remained [1]. That is the reverse of the pattern seen with GIP receptor agonists, which act through GABAergic GIPR neurons without needing the GLP-1 receptor [1].
The researchers then used single-nucleus RNA sequencing to compare gene activity in the dorsal vagal complex, a brainstem region involved in feeding control. Agonism and antagonism produced opposing patterns. Antagonism, but not agonism, closely resembled the pattern produced by GLP-1 receptor signaling in that region [1]. Both GIP receptor antagonism and GLP-1 receptor agonism also regulated genes implicated in synaptic plasticity, the ability of nerve connections to change [1].
All of the experiments were done in male mice [1]. The paper carries a publisher correction published on 13 May 2025 [1]. Results in animals often do not carry over to people, and the study reports no human testing of GIP receptor antagonists for weight loss [1].
Why it matters for patients
The findings help explain why two opposite approaches to the same receptor can both reduce weight. Tirzepatide works by activating the GIP receptor and the GLP-1 receptor, while the experimental approach in this study blocks the GIP receptor and leaves GLP-1 signaling intact [1].
One practical implication from the mouse data is that a GIP receptor antagonist may depend on the body's own GLP-1 signaling to work, since the effect vanished when the GLP-1 receptor was missing [1]. That has not been tested in people, and the study does not show that any approved medicine acts through this route. Nothing in the results changes how currently approved GLP-1 or dual GIP/GLP-1 medicines are used, and the paper reports no human weight-loss results, side effects or dosing for a GIP receptor antagonist [1].
What happens next
No human trials of a GIP receptor antagonist for weight loss are described in the paper, and no timeline for such studies has been disclosed [1].
Images from the sources
Sources
Semaglutides.org provides information only, not medical advice. Talk to a licensed provider about your own care before making changes. Some telehealth links are affiliate links and are labeled where they appear.