FRI001 Tanycytic Thyroid-stimulating Hormone Receptor Activation Increases Blood-Hypothalamus Barrier Permeability And Induces Appetite In Female Mice

Abstract Disclosure: H.S. Kannangara: None. B. Jocoll: None. S. Miyashita: None. A. Gumerova: None. F. Korkmaz: None. R. Witztum: None. S. Sims: None. U. Cheliadinova: None. G. Pevnev: None. O. Moldavski: None. T. Frolinger: None. T. Yuen: None. V. Ryu: None. M. Zaidi: None. In addition to its well-known action to trigger thyroid hormone production, thyroid-stimulating hormone (TSH) is released in the brain, and its receptor (TSHR) has been found in brain sites, including the tanycytes of the third ventricle, that regulate ingestive behavior and convey metabolic information across the blood-hypothalamus barrier (BHB). Our recent work highlights largely undiscovered role for TSHRs in the tanycytes. Here, we tested the hypothesis that tanycytic TSHR activation triggers rapid remodeling of BHB vascular permeability inducing appetite. We compared hypothalamic vascular permeability of food deprived (FD) and ad libitum fed (AL) Tshr+/- and their wild type (WT) counterparts exploiting transmission electron microscopy studies and immunofluorescence for constitutive tight junction protein Claudin-1 and homodimer glycoprotein MECA-32, primarily expressed in tanycytes and endothelial cells, respectively. Fasting significantly increased the organization of tanycytic honeycomb pattern of Claudin-1 and fenestral MECA-32-associated diaphragms in the median eminence and arcuate nucleus implying decreased BHB vascular permeability in Tshr+/- mice. Transmission electron microscopy confirmed immunofluorescence results. In a separate gain-of-function experiment, TSHR activation by the small molecule MS438 increased BHB vascular permeability as evidenced by decreased Claudin-1 and MECA-32 immunostaining. Tanycytic TSHR activation significantly increased both food foraging and intake as during one-hour refeeding after FD. Surprisingly, refeeding restored neuronal activation marker c-Fos expression in the paraventricular nucleus of the hypothalamus, parabrachial nucleus and nucleus of the solitary tract, though failed to do so in the paraventricular nucleus and nucleus of the solitary tract of MS438-injected mice. Collectively, these data infer that modulation of tanycytic TSHRs plays an important role in BHB plasticity in relation with ingestive behavior. Presentation: Friday, June 16, 2023