Cambridge study explains how opposite approaches to the same GIP receptor both aid weight loss in mice
A mouse study explains why activating and blocking the same GIP receptor can both promote weight loss, pointing to combinations that researchers hope will work better with fewer side effects.
Researchers at the University of Cambridge have worked out how two opposite ways of targeting the same brain receptor can each produce weight loss, at least in mice. Activating the receptor in the brainstem reduced appetite, while blocking it in the hypothalamus removed a kind of "brake" on fullness signals [1]. The mouse study appeared in the journal Nature Metabolism and was described by the university in August 2026 [1].
The receptor is GIPR, short for glucose-dependent insulinotropic polypeptide receptor. It has been an unusual puzzle for obesity researchers: some drugs activate it and others block it, yet both approaches can help promote weight loss [1]. Wegovy and Ozempic (semaglutide) act on a different target, the GLP-1 receptor. Mounjaro and Zepbound (tirzepatide) act on both GLP-1R and GIPR and activate the GIP receptor, while MariTide blocks GIPR and activates GLP-1R and is in phase 3 clinical trials [1].
To find out where each approach acts, the Cambridge team, based at the Institute of Metabolic Science, used genetically engineered mice with GIPR removed from specific brain areas. One group lacked the receptor in the brainstem, the region at the base of the brain just above the spinal cord that is involved in appetite and nausea. A second group lacked it in the hypothalamus, which helps regulate hunger and body weight. A third group of unmodified mice served as controls [1]. The animals received combinations of a GIPR agonist (which activates the receptor), a GIPR antagonist (which blocks it) and a GLP-1 drug, and researchers tracked food consumption, body weight, fat mass, blood sugar control and brain activity [1].
Agonists worked mainly through the brainstem, cutting appetite and lowering body weight. Antagonists worked through the hypothalamus, where GIPR appears to act as a brake that limits how strongly the brainstem responds to signals that the body is full. Blocking the receptor released that brake, letting fullness signals have a stronger effect [1].
The team also reported evidence that blocking GIPR could strengthen medicines that target the amylin receptor, a separate class of obesity drug candidates [1]. Both approaches increased weight loss when paired with certain GLP-1-based medicines, the university said [1].
Dr. Jo Lewis, the study's first author, said: "Understanding which brain circuits respond to these medications - and how they do so - could help us design better drugs that produce more weight loss with fewer side effects, and which might work in combination with other obesity medicines to even greater effect." [1] She added that the work strengthens the idea that the brain is central to obesity treatment, and that these drugs act on specific, identifiable brain circuits rather than only on the gut or pancreas [1]. The research was funded by the Medical Research Council and Wellcome [1].
Why it matters for patients
More than a billion people worldwide live with obesity, a condition that raises the risk of type 2 diabetes, cardiovascular disease and cancer [1].
For patients, the value of this work is explanatory rather than immediate. It helps account for why drugs with opposite effects on the same receptor - tirzepatide activating GIPR, MariTide blocking it - can both produce weight loss [1]. It also points toward combinations, including pairing a GIP-targeting drug with a GLP-1 medicine, or a GIPR blocker with a drug aimed at the amylin receptor [1].
Two limits matter. All of the experiments were in mice; the approach has not been tested in people, and no human weight-loss, dose or side-effect results have been reported [1]. Researchers have said the goal is more weight loss with fewer side effects, and the brainstem is involved in nausea as well as appetite [1], but whether targeting these circuits reduces nausea in people has not been established.
What happens next
MariTide, which combines GIPR blockade with GLP-1 receptor activation, is already in phase 3 clinical trials [1]. When those trials will report results has not been reported. Whether the specific brain-region strategies described in the mouse study move into human testing has not been announced.
Sources
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