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<\/a>Study: Glucose-dependent insulinotropic polypeptide receptor signaling in oligodendrocytes increases the weight-loss action of GLP-1R agonism<\/a>. Image Credit:\u00a0Juan Gaertner\u00a0\/ Shutterstock<\/p>\nIn a recent study published in the journal\u00a0Cell Metabolism<\/a>, a group of researchers tested whether glucose-dependent insulinotropic polypeptide receptor (GIPR) signaling in oligodendrocytes (OLs) increases brain access and weight-loss efficacy of<\/a> glucagon-like peptide-1 receptor (GLP-1R) agonists.<\/p>\n Background<\/p>\n One in eight adults lives with obesity, and many now use incretin drugs that can cut weight by over 20%. Incretins act through GIPR and GLP-1R, but why combining them helps remains unclear. The median eminence (ME), an interface where blood signals meet neurons, may be a gate.<\/p>\n OLs, long known for making myelin, also remodel this gate in response to diet. Clarifying whether glucose-dependent insulinotropic polypeptide (GIP) signaling in OLs boosts brain entry and the effects of glucagon-like peptide-1 (GLP-1) therapies could guide stronger treatments; further research is needed.<\/p>\n About the study<\/p>\n The researchers used adult mice to test whether GIPR signaling in OLs shapes brain access and efficacy of GLP-1R agonists. They generated inducible OL knockouts by crossing proteolipid protein 1-Cre recombinase-estrogen receptor T2 (Plp1-CreERT2) with Gipr floxed mice, triggered recombination with tamoxifen at postnatal day 60, and induced obesity with a 60% high-fat diet. A long-acting GIPR agonist (LAGIPRA) and a long-acting GLP-1R agonist (LAGLP-1RA; liraglutide) were administered alone or together.<\/p>\n To map drug entry, a short-acting GLP-1R agonist labeled with IR800 (IR800-Exendin-4) was injected; brains were cleared and imaged by light-sheet microscopy. Oligodendrogenesis and myelination were quantified by fluorescent in situ hybridization and immunostaining for myelin basic protein, breast carcinoma amplified sequence 1, and bone morphogenetic protein 4, with a 5-ethynyl-2\u2032-deoxyuridine pulse-chase.<\/p>\n Vascular permeability was assessed by vascular endothelial growth factor<\/a> A (VEGF-A) expression, vascular endothelial growth factor (VEGF) immunoreactivity, and mouse endothelial cell antigen 32 (MECA32)-positive fenestrated capillaries. Metabolic readouts included energy expenditure, food intake, and glucose and insulin tolerance.<\/p>\n Finally, an adeno-associated virus encoding the inhibitory human muscarinic M4 receptor engineered for activation by designer drugs (hM4Di) targeted paraventricular hypothalamus (PVH) arginine vasopressin (AVP) neurons in arginine vasopressin promoter-Cre (Avp-Cre) mice; deschloroclozapine was administered to activate hM4Di and suppress these neurons during liraglutide tests.<\/p>\n Study results<\/p>\n In the ME, GIPR was enriched in mature OLs, with rare expression in OL progenitor cells; high-fat feeding increased OL density and the number of GIPR-positive OLs specifically in this region. This effect was not observed in white matter tracts such as the corpus callosum, indicating a localized role.<\/p>\n OL-specific GIPR deletion reduced adult oligodendrogenesis and OL survival in the ME and lowered myelin basic protein, while major white-matter tracts showed little change, indicating a localized role at the brain\u2019s metabolic gateway. Mice lacking OL GIPR showed reduced energy expenditure and intake, preserved oral glucose tolerance, impaired insulin tolerance, and shifts in branched-chain\u2013related metabolites, consistent with altered substrate handling during obesity.<\/p>\n Pharmacologic activation produced complementary effects. In lean mice, a long-acting GIPR agonist increased OL lineage cells and myelin in the ME. In diet-induced obesity (DIO), the same agonist increased new OL production and restored turnover, while raising vascular access signals: VEGF-A transcripts and VEGF immunoreactivity increased, and MECA32-marked fenestrated capillaries became denser, indicating enhanced vascular permeability.<\/p>\n Pre-treating obese mice with the GIPR agonist increased the brain uptake of an IR800-labeled short-acting GLP-1R agonist in the ME and adjacent arcuate nucleus of the hypothalamus (ARH), indicating enhanced access across the ME-ARH border. Crucially, this uptake increase required OL GIPR; it was absent after OL GIPR deletion.<\/p>\n Efficacy mirrored entry, as in wild-type mice, long-acting GLP-1R agonism lowered food intake and body weight, and co-administration with the GIPR agonist amplified both outcomes; in OL GIPR knockouts, the GIPR agonist no longer potentiated GLP-1R-driven weight loss or anorexia, indicating that OL GIPR signaling is required for full synergy.<\/p>\n Imaging showed that peripherally dosed short-acting GLP-1R agonists accumulated along myelinated axon bundles in the ME, colocalizing with myelin basic protein; revealing a novel mechanism: peripherally administered GLP-1R agonists access the brain via myelinated AVP axons in the ME, bypassing the blood-brain barrier (BBB).<\/p>\n Super-resolution microscopy localized GLP-1R on AVP axons and at nodes labeled by contactin-associated protein (CASPR). Finally, chemogenetic silencing of PVH AVP neurons with deschloroclozapine prevented liraglutide-induced hypophagia and weight loss, demonstrating that these neurons are necessary for the systemic drug\u2019s weight-loss action.<\/p>\n Conclusions<\/p>\n To summarize, this study connects incretin pharmacology to a concrete brain entry mechanism: signaling through GIPRs in ME OLs increases vascular permeability via VEGF-A induction and increased capillary fenestration and enables GLP-1R agonists to reach appetite-regulating AVP axons.<\/p>\n The requirement for this pathway may help explain why GIPR\/GLP-1R co-agonists show greater efficacy than single agents, and offer a mechanistic basis for their enhanced clinical performance. Clinically, the mechanism helps interpret the potency of co-agonists used for obesity and type 2 diabetes and points to biomarkers, such as VEGF-A induction or imaging of ME access, to guide dosing or combinations while limiting side effects.<\/p>\n However, the authors note several limitations: the OL Gipr knockout model achieved only partial deletion; the experiments primarily assessed liraglutide rather than other GLP-1R agonists; and the behavioural outcomes, while informative, were not exhaustive. These caveats temper the conclusions and highlight the need for further research to confirm generalizability and clinical relevance.<\/p>\n Why does Zepbound (tirzepatide) lead to more weight loss than Ozempic (semaglutide<\/a>)? \u2014 Eric Topol (@EricTopol) August 13, 2025<\/a><\/p>\n Journal reference:<\/p>\n \tHansford, R., Buller, S., Tsang, A. H., Benoit, S., Roberts, A. G., Erskine, E., Brown, T., Pirro, V., Reimann, F., Harada, N., Inagaki, N., Samms, R. J., Broichhagen, J., Hodson, D. J., Adriaenssens, A., Park, S., & Blouet, C. (2025). Glucose-dependent insulinotropic polypeptide receptor signaling in oligodendrocytes increases the weight-loss action of GLP-1R agonism. Cell Metabolism. DOI: 10.1016\/j.cmet.2025.07.009,\u00a0https:\/\/www.cell.com\/cell-metabolism\/fulltext\/S1550-4131(25)00355-9<\/a><\/p>\n
The dual receptor (GLP-1+ GIP) has more pronounced effects in the brainhttps:\/\/t.co\/1aLDifDS2o<\/a> pic.twitter.com\/wS81Pf5cXf<\/a><\/p>\n