AAV5-mediated manipulation of insulin expression in choroid plexus has long-term metabolic and behavioral consequences.

The choroid plexus (CP) is a source of trophic factors for the developing and mature brain. Insulin is produced in epithelial cells of the CP (EChPs), and its secretion is stimulated by Htr2c-mediated signaling. We modulated insulin expression in EChPs with intracerebroventricular injections of AAV5. Insulin overexpression in CP decelerates food intake, whereas its knockdown has the opposite effect. Insulin overexpression also results in reduced anxious behavior. Transcriptomic changes in the hypothalamus, especially in synapse-related processes, are also seen in mice overexpressing insulin in CP. Last, activation of Gq signaling in CP leads to acute Akt phosphorylation in neurons of the arcuate nucleus, indicating a direct action of CP-derived insulin on the hypothalamus. Taken together, our findings signify that CP is a relevant source of insulin in the central nervous system and that CP-derived insulin should be taken into consideration in future work pertaining to insulin actions in the brain.

Physiology of the tongue with emphasis on taste transduction.

The tongue is a complex multifunctional organ that interacts and senses both interoceptively and exteroceptively. Although it is easily visible to almost all of us, it is relatively understudied and what is in the literature is often contradictory or is not comprehensively reported. The tongue is both a motor and a sensory organ: motor in that it is required for speech and mastication, and sensory in that it receives information to be relayed to the central nervous system pertaining to the safety and quality of the contents of the oral cavity. Additionally, the tongue and its taste apparatus form part of an innate immune surveillance system. For example, loss or alteration in taste perception can be an early indication of infection as became evident during the present global SARS-CoV-2 pandemic. Here, we particularly emphasize the latest updates in the mechanisms of taste perception, taste bud formation and adult taste bud renewal, and the presence and effects of hormones on taste perception, review the understudied lingual immune system with specific reference to SARS-CoV-2, discuss nascent work on tongue microbiome, as well as address the effect of systemic disease on tongue structure and function, especially in relation to taste.