Hypothalamic and dorsal vagal glucose-dependent insulinotropic polypeptide receptor (GIPR) neurons employ distinct mechanisms to affect feeding
Central glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) signalling is critical for GIP-based therapeutics to lower body weight, but pathways leveraged by GIPR agonism pharmacology in the brain remain incompletely understood. We explored the role of Gipr neurons in the hypothalamus and dorsal vagal complex (DVC)—brain regions critical to the control of energy balance. Hypothalamic expression of Gipr expression was not necessary for the synergistic effect of GIPR/ agonism combined with GLP-1R co-agonism on body weight. While chemogenetic stimulation of both hypothalamic and DVC Gipr neurons suppressed food intake, activation of DVC Gipr neurons reduced ambulatory activity and induced conditioned taste avoidance, while there was no effect of a short-acting GIPR agonist (SAGIPRA). Within the DVC, Gipr neurons of the nucleus tractus solitarius (NTS), but not the area postrema (AP), projected to the parabrachial nucleus and paraventricular hypothalamic nucleusdistal brain regions. ScRNAseq and FISH analysis showed that Gipr neurons in the NTS and AP Gipr neurons were transcriptomically distinct. Peripherally-dosed fluorescent GIPR agonists (GIPRAs) revealed that GIPRA access was restricted to circumventricular organs in the CNS. Together tThese data demonstrate that while the hypothalamus, AP and NTS are key sites for Gipr expression, these subpopulations of Gipr neurons in the hypothalamus, AP and NTS differ in their connectivity, transcriptomic profile, peripheral accessibility to peripherally administered GIPRAs, and the appetite controlling pathways they employ. These results highlight the heterogeneity of the central GIPR signalling axis, and suggest that studies aimed at understandinginto the effects of GIP pharmacology on feeding behaviour should consider the interplay of multiple regulatory pathways. Overall design: Gipr- or Glp1r-expressing cells were isolated from the hindbrain of either GiprEYFP or Glp1rEYFP mice, respectively, by Fluorescence-activated cell sorting (FACS) according to the presence or absence of EYFP signal and analyzed using scRNAseq.