Hypothalamic ependymal-glial cells express the glucose transporter GLUT2, a protein involved in glucose sensing

Authors


Address correspondence and reprint requests to Dr Francisco Nualart, Laboratorio de Neurobiología Celular, Departamento de Histología y Embriología, Facultad de Ciencias Biológicas, Universidad de Concepción, casilla 160C, Chile. E-mail: fnualart@udec.cl

Abstract

The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as an integral part of the glucose-sensing mechanism in the pancreatic islet β cells. The expression of GLUT2 and K-ATP channels in the hypothalamic region suggest that they are also involved in a sensing mechanism in this area. The hypothalamic glial cells, known as tanycytes α and β, are specialized ependymal cells that bridge the cerebrospinal fluid and the portal blood of the median eminence. We used immunocytochemistry, in situ hybridization and transport analyses to demonstrate the glucose transporters expressed in tanycytes. Confocal microscopy using specific antibodies against GLUT1 and GLUT2 indicated that both transporters are expressed in α and β tanycytes. In addition, primary cultures of mouse hypothalamic tanycytes were found to express both GLUT1 and GLUT2 transporters. Transport studies, including 2-deoxy-glucose and fructose uptake in the presence or absence of inhibitors, indicated that these transporters are functional in cultured tanycytes. Finally, our analyses indicated that tanycytes express the K-ATP channel subunit Kir6.1 in vitro. As the expression of GLUT2 and K-ATP channel is linked to glucose-sensing mechanisms in pancreatic β cells, we postulate that tanycytes may be responsible, at least in part, for a mechanism that allows the hypothalamus to detect changes in glucose concentrations.

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