title: Photoperiodic regulation of glycogen metabolism, glycolysis, and glutamine synthesis in tanycytes of the Siberian hamster suggests novel roles of tanycytes in hypothalamic function.
abstract: The objective of this study is to investigate the impact of photoperiod on the temporal and spatial expression of genes involved in glucose metabolism in the brain of the seasonal mammal Phodopus sungorus (Siberian hamster). In situ hybridization was performed on brain sections obtained from male hamsters held in long photoperiod (high body weight and developed testes) or short photoperiod (reduced body weight with testicular regression). This analysis revealed upregulation in expression of genes involved in glycogen and glucose metabolism in short photoperiod and localized to the tanycyte layer of the third ventricle. On the basis of these data and a previously identified photoperiod-dependent increase in activity of neighboring hypothalamic neurons, we hypothesized that the observed expression changes may reflect alteration in either metabolic fuel or precursor neurotransmitter supply to surrounding neurons. Gene expression analysis was performed for genes involved in lactate and glutamate transport. This analysis showed that the gene for the lactate transporter MCT2 and glutamate transporter GLAST was decreased in the tanycyte layer in short photoperiod. Expression of mRNA for glutamine synthetase, the final enzyme in the synthesis of the neuronal neurotransmitter precursor, glutamine, was also decreased in short photoperiod. These data suggest a role for tanycytes in modulating glutamate concentrations and neurotransmitter supply in the hypothalamic environment.
authors.affiliation: Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Kanishka
authors.initials: K
authors.lastname: Nilaweera
authors.forename: Annika
authors.initials: A
authors.lastname: Herwig
authors.forename: Matei
authors.initials: M
authors.lastname: Bolborea
authors.forename: Gill
authors.initials: G
authors.lastname: Campbell
authors.forename: Claus D
authors.initials: CD
authors.lastname: Mayer
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Morgan
authors.forename: Francis J P
authors.initials: FJ
authors.lastname: Ebling
authors.forename: Perry
authors.initials: P
authors.lastname: Barrett
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000502:physiology; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D004805:Ependyma / Q000166:cytology* / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000096:biosynthesis*; D006003:Glycogen / Q000378:metabolism*; D006019:Glycolysis / Q000502:physiology*; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D017403:In Situ Hybridization; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D019581:Neuropil / Q000378:metabolism; D017111:Phodopus; D017440:Photoperiod; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D005973:Glutamine; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D006003:Glycogen; D005947:Glucose