Research ArticleObesity

GABA neurons in the nucleus tractus solitarius express GLP-1 receptors and mediate anorectic effects of liraglutide in rats

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Science Translational Medicine  04 Mar 2020:
Vol. 12, Issue 533, eaay8071
DOI: 10.1126/scitranslmed.aay8071

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The pulse of weight loss

Liraglutide is an approved medication that is prescribed in part for its ability to lower food intake and body weight. Liraglutide is a known glucagon-like peptide-1 receptor (GLP-1R) agonist; however, how the drug affects the central nervous system to promote satiety is not fully elucidated. Fortin et al. identified a subset of GABAergic neurons in the nucleus tractus solitarius (NTS) that expressed GLP-1Rs and helped mediate the anorectic and weight-reducing effects of liraglutide in male rats. Knockdown of NTS Glp1r in the rats abrogated the food intake– and body weight–reducing effects of both acutely and chronically administered liraglutide.

Abstract

The glucagon-like peptide-1 receptor (GLP-1R) agonist liraglutide is approved for the treatment of obesity; however, there is still much to be learned regarding the neuronal sites of action that underlie its suppressive effects on food intake and body weight. Peripherally administered liraglutide in rats acts in part through central GLP-1Rs in both the hypothalamus and the hindbrain. Here, we extend findings supporting a role for hindbrain GLP-1Rs in mediating the anorectic effects of liraglutide in male rats. To dissociate the contribution of GLP-1Rs in the area postrema (AP) and the nucleus tractus solitarius (NTS), we examined the effects of liraglutide in both NTS AAV-shRNA–driven Glp1r knockdown and AP-lesioned animals. Knockdown of NTS GLP-1Rs, but not surgical lesioning of the AP, attenuated the anorectic and body weight–reducing effects of acutely delivered liraglutide. In addition, NTS c-Fos responses were maintained in AP-lesioned animals. Moreover, NTS Glp1r knockdown was sufficient to attenuate the intake- and body weight–reducing effects of chronic daily administered liraglutide over 3 weeks. Development of improved obesity pharmacotherapies requires an understanding of the cellular phenotypes targeted by GLP-1R agonists. Fluorescence in situ hybridization identified Glp1r transcripts in NTS GABAergic neurons, which when inhibited using chemogenetics, attenuated the food intake– and body weight–reducing effects of liraglutide. This work demonstrates the contribution of NTS GLP-1Rs to the anorectic potential of liraglutide and highlights a phenotypically distinct (GABAergic) population of neurons within the NTS that express the GLP-1R and are involved in the mediation of liraglutide signaling.

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