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

Abstract

The GLUT2 glucose transporter is expressed in pancreatic islet β cells participating in glucose sensing mechanisms. In addition to glucose, GLUT2 is required in the transport of fructuose. In situ hybridization analyses of GLUT2 gene expression suggested that this transporter is present in hypothalamic regions responsible for glucose sensing. The hypothalamic glial cells, known as α and β tanycytes, are specialized ependymal cells that bridge the CSF and the blood. We used immunocytochemistry and transport analyses to demonstrate that GLUT1 and GLUT2 are expressed in tanycytes and are directly involved in the uptake of glucose and fructose. We also demonstrated that GLUT1 expression is elevated in β‐1 tanycytes, as compared to neurons and astrocytes. In addition, confocal microscopy analysis using anti‐GLUT2 indicated that GLUT2 was specifically expressed in β‐1 and β‐2 tanycytes. A newly developed primary culture of mouse hypothalamic tanycytes was found to express both GLUT1 and GLUT2. Analyses of 2‐deoxy‐d‐glucose and fructose uptake in cultured tanycytes revealed the presence of two transporters with transport Kms and sensitivity to inhibitors consistent with the functional properties of GLUT1 and GLUT2. Therefore, we conclude that mouse hypothalamic tanycytes express functional GLUT1 and GLUT2. Because the expression of GLUT2 is linked to glucose sensing mechanisms, we postulate that glial cells participate, at least in part, in glucose sensing mechanisms.Acknowledgements: Supported by Grands FONDECYT 1010843 and DIUC‐GIA 201.034.006–1.4 from Concepción University.