Glial glucokinase expression in adult and post-natal development of the hypothalamic region.
It has recently been proposed that hypothalamic glial cells sense glucose levels and release lactate as a signal to activate adjacent neurons. GK (glucokinase), the hexokinase involved in glucose sensing in pancreatic beta-cells, is also expressed in the hypothalamus. However, it has not been clearly determined if glial and/or neuronal cells express this protein. Interestingly, tanycytes, the glia that cover the ventricular walls of the hypothalamus, are in contact with CSF (cerebrospinal fluid), the capillaries of the arcuate nucleus and adjacent neurons; this would be expected for a system that can detect and communicate changes in glucose concentration. Here, we demonstrated by Western-blot analysis, QRT-PCR [quantitative RT-PCR (reverse transcription-PCR)] and in situ hybridization that GK is expressed in tanycytes. Confocal microscopy and immuno-ultrastructural analysis revealed that GK is localized in the nucleus and cytoplasm of beta1-tanycytes. Furthermore, GK expression increased in these cells during the second week of post-natal development. Based on this evidence, we propose that tanycytes mediate, at least in part, the mechanism by which the hypothalamus detects changes in glucose concentrations.
Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.
Carola
C
Millán
Fernando
F
Martínez
Christian
C
Cortés-Campos
Isabel
I
Lizama
Maria Jose
MJ
Yañez
Paula
P
Llanos
Karin
K
Reinicke
Federico
F
Rodríguez
Bruno
B
Peruzzo
Francisco
F
Nualart
Maria Angeles
MA
García
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D005941:Glucokinase / Q000096:biosynthesis* / Q000235:genetics; D007031:Hypothalamus / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D009457:Neuroglia / Q000166:cytology / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D005941:Glucokinase