Glucagon-like peptide-1 receptors in the gustatory cortex influence food intake

The gustatory region of the insular cortex (GC) processes taste information in manners important for taste-guided behaviors, including food intake itself. In addition to oral gustatory stimuli, GC activity is also influenced by physiological states including hunger. The specific cell-types and molecular mechanisms that afford with GC with such influences on food intake are unclear. Glucagon-like peptide 1 (GLP-1) is produced by neurons in the brain whereafter it can act upon GLP-1 receptor-expressing (GLP-1R+) neurons found in several brain regions. In these brain regions, GLP-1R agonism suppresses homeostatic food intake and dampens the hedonic value of food. Here, we report in mice of both sexes that cells within the GC express GLP-1R mRNA and further, by ex vivo brain slice recordings, that GC GLP-1R+ neurons are depolarized by the selective GLP-1R agonist, exendin-4 (Ex-4). Next we found that chemogenetic stimulation of GLP-1R+ neurons, and also pharmacological stimulation of GC-GLP-1Rs themselves, both reduced homeostatic food intake. When maintained on a high-fat diet, obese mice exhibited impaired food intake responses when Ex-4 was administered into the GC. Yet, when obese mice were switched to a low-fat diet, the effect of GC Ex-4 was restored - indicating that GC GLP-1R influences may depend upon palatability of the food. Together, these results provide evidence for a specific cell population in the GC which may hold roles in both homeostatic and hedonic food intake.