Probes for GLP1R

Sensory neurons relay gut-derived signals to the brain, yet the molecular and functional organization of distinct populations remains unclear. Here, we employed intersectional genetic manipulations to probe the feeding and glucoregulatory function of distinct sensory neurons. We reconstruct the gut innervation patterns of numerous molecularly defined vagal and spinal afferents and identify their downstream brain targets. Bidirectional chemogenetic manipulations, coupled with behavioral and circuit mapping analysis, demonstrated that gut-innervating, glucagon-like peptide 1 receptor (GLP1R)-expressing vagal afferents relay anorexigenic signals to parabrachial nucleus neurons that control meal termination. Moreover, GLP1R vagal afferent activation improves glucose tolerance, and their inhibition elevates blood glucose levels independent of food intake. In contrast, gut-innervating, GPR65-expressing vagal afferent stimulation increases hepatic glucose production and activates parabrachial neurons that control normoglycemia, but they are dispensable for feeding regulation. Thus, distinct gut-innervating sensory neurons differentially control feeding and glucoregulatory neurocircuits and may provide specific targets for metabolic control.

The hypothalamus plays a key role in coordinating fundamental body functions. Despite recent progress in single-cell technologies, a unified catalog and molecular characterization of the heterogeneous cell types and, specifically, neuronal subtypes in this brain region are still lacking. Here, we present an integrated reference atlas, 'HypoMap,' of the murine hypothalamus, consisting of 384,925 cells, with the ability to incorporate new additional experiments. We validate HypoMap by comparing data collected from Smart-Seq+Fluidigm C1 and bulk RNA sequencing of selected neuronal cell types with different degrees of cellular heterogeneity. Finally, via HypoMap, we identify classes of neurons expressing glucagon-like peptide-1 receptor (Glp1r) and prepronociceptin (Pnoc), and validate them using single-molecule in situ hybridization. Collectively, HypoMap provides a unified framework for the systematic functional annotation of murine hypothalamic cell types, and it can serve as an important platform to unravel the functional organization of hypothalamic neurocircuits and to identify druggable targets for treating metabolic disorders.

Therapies based on glucagon-like peptide-1 receptor (GLP-1R) agonism are highly effective in treating type 2 diabetes and obesity, but the localization of GLP-1Rs mediating the antidiabetic and other possible actions of GLP-1 is still debated. The purpose with this study was to identify sites of GLP-1R mRNA and protein expression in the mouse gastrointestinal system by means of GLP-1R antibody immunohistochemistry, Glp1r mRNA fluorescence in situ hybridization, and 125I-exendin (9-39) autoradiography. As expected, GLP-1R staining was observed in almost all β-cells in the pancreatic islets, but more rarely in α- and δ-cells. In the stomach, GLP-1R staining was found exclusively in the gastric corpus mucous neck cells, known to protect the stomach mucosa. The Brunner glands were strongly stained for GLP-1R, and pretreatment with GLP-1 agonist exendin-4 caused internalization of the receptor and mucin secretion, while pretreatment with phosphate-buffered saline or antagonist exendin (9-39) did not. In the intestinal mucosa, GLP-1R staining was observed in intraepithelial lymphocytes, lamina propria lymphocytes, and enteroendocrine cells containing secretin, peptide YY, and somatostatin, but not cholecystokinin. GLP-1R staining was seen in nerve fibers within the choline acetyl transferase- and nitric oxide-positive myenteric plexuses from the gastric corpus to the distal large intestine being strongest in the mid- and hindgut area. Finally, intraperitoneal administration of radiolabeled exendin (9-39) strongly labeled myenteric fibers. In conclusion, this study expands our knowledge of GLP-1R localization and suggests that GLP-1 may serve an important role in modulating gastrointestinal health and mucosal protection.

Neuropeptide FF (NPFF) group peptides belong to the evolutionary conserved RF-amide peptide family. While they have been assigned a role as pain modulators, their roles in other aspects of physiology have received much less attention. NPFF peptides and their receptor NPFFR2 have strong and localized expression within the dorsal vagal complex that has emerged as the key centre for regulating glucose homeostasis. Therefore, we investigated the role of the NPFF system in the control of glucose metabolism and the histochemical and molecular identities of NPFF and NPFFR2 neurons.We examined glucose metabolism in Npff-/- and wild type (WT) mice using intraperitoneal (i.p.) glucose tolerance and insulin tolerance tests. Body composition and glucose tolerance was further examined in mice after 1-week and 3-week of high-fat diet (HFD). Using RNAScope double ISH, we investigated the neurochemical identity of NPFF and NPFFR2 neurons in the caudal brainstem, and the expression of receptors for peripheral factors in NPFF neurons.Lack of NPFF signalling in mice leads to improved glucose tolerance without significant impact on insulin excursion after the i.p. glucose challenge. In response to an i.p. bolus of insulin, Npff-/- mice have lower glucose excursions than WT mice, indicating an enhanced insulin action. Moreover, while HFD has rapid and potent detrimental effects on glucose tolerance, this diet-induced glucose intolerance is ameliorated in mice lacking NPFF signalling. This occurs in the absence of any significant impact of NPFF deletion on lean or fat masses, suggesting a direct effect of NPFF signalling on glucose metabolism. We further reveal that NPFF neurons in the subpostrema area (SubP) co-express receptors for peripheral factors involved in glucose homeostasis regulation such as insulin and GLP1. Furthermore, Npffr2 is expressed in the glutamatergic NPFF neurons in the SubP, and in cholinergic neurons of the dorsal motor nucleus of the vagus (DMV), indicating that central NPFF signalling is likely modulating vagal output to innervated peripheral tissues including those important for glucose metabolic control.NPFF signalling plays an important role in the regulation of glucose metabolism. NPFF neurons in the SubP are likely to receive peripheral signals and mediate the control of whole-body glucose homeostasis via centrally vagal pathways. Targeting NPFF and NPFFR2 signalling may provide a new avenue for treating type 2 diabetes and obesity.