Choroid Plexus-Derived Insulin Inhibits Feeding via Direct Signaling through Arcuate Nucleus

The choroid plexus is an important source of trophic factors for the developing and mature brain. Recently we described the expression and production of mature insulin in epithelial cells of the choroid plexus, and how its secretion can be modulated by serotonin through Htr2c, a metabotropic receptor that signals via Gq. To understand the function of this choroid plexus-derived insulin, here we describe a way to genetically target epithelial cells of the choroid plexus using a viral vector. With this, we modulated insulin expression and evaluated behavior. Insulin overexpression in the choroid plexus of wild type mice led to an inhibition in feeding, whereas insulin knockdown in choroid plexus of Ins1-/-Ins2fl/fl mice promoted discrete increases in food intake, especially after a period of fasting. Insulin overexpression in choroid plexus induced roust transcriptomic changes in the hypothalamus, most of which related to axonal growth and synapse-related processes. Finally, activation of Gq signaling in insulin-overexpressing choroid plexuses led to acute AKT phosphorylation in neurons of the arcuate nucleus, suggesting a direct action, through the CSF, of choroid plexus-derived insulin on the hypothalamus. Taken together our findings prove that the choroid plexus is a relevant source of insulin in the central nervous system, with physiological implications in feeding behavior. We believe that choroid plexus-derived insulin has to be taken into consideration in future work pertaining insulin actions in the brain. Comparative gene expression profiling and analysis of RNA-Seq data from the choroid plexus (CP) and hypothalamus (HT) of mice with overexpression of Ins2 gene in the CP.