title: Hypothalamic thyroid hormone catabolism acts as a gatekeeper for the seasonal control of body weight and reproduction.
abstract: Seasonal adaptations in physiology exhibited by many animals involve an interface between biological timing and specific neuroendocrine systems, but the molecular basis of this interface is unknown. In this study of Siberian hamsters, we show that the availability of thyroid hormone within the hypothalamus is a key determinant of seasonal transitions. The expression of the gene encoding type III deiodinase (Dio3) and Dio3 activity in vivo (catabolism of T(4) and T(3)) is dynamically and temporally regulated by photoperiod, consistent with the loss of hypothalamic T(3) concentrations under short photoperiods. Chronic replacement of T(3) in the hypothalamus of male hamsters exposed to short photoperiods, thus bypassing synthetic or catabolic deiodinase enzymes located in cells of the ependyma of the third ventricle, prevented the onset of short-day physiology: hamsters maintained a long-day body weight phenotype and failed to undergo testicular and epididymal regression. However, pelage moult to a winter coat was not affected. Type II deiodinase gene expression was not regulated by photoperiod in these hamsters. Collectively, these data point to a pivotal role for hypothalamic DIO3 and T(3) catabolism in seasonal cycles of body weight and reproduction in mammals.
authors.affiliation: Rowett Research Institute, Greenburn Road, Buckburn, Aberdeen AB21 9SB, United Kingdom. P.Barrett@Rowett.ac.uk
authors.forename: Perry
authors.initials: P
authors.lastname: Barrett
authors.forename: Francis J P
authors.initials: FJ
authors.lastname: Ebling
authors.forename: Sandrine
authors.initials: S
authors.lastname: Schuhler
authors.forename: Dana
authors.initials: D
authors.lastname: Wilson
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Ross
authors.forename: Amy
authors.initials: A
authors.lastname: Warner
authors.forename: Preeti
authors.initials: P
authors.lastname: Jethwa
authors.forename: Anita
authors.initials: A
authors.lastname: Boelen
authors.forename: Theo J
authors.initials: TJ
authors.lastname: Visser
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Ozanne
authors.forename: Zoe A
authors.initials: ZA
authors.lastname: Archer
authors.forename: Julian G
authors.initials: JG
authors.lastname: Mercer
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Morgan
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001835:Body Weight / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D006224:Cricetinae; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D006197:Hair / Q000502:physiology; D007031:Hypothalamus / Q000201:enzymology / Q000502:physiology*; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism; D008297:Male; D008660:Metabolism; D010641:Phenotype; D017111:Phodopus; D017440:Photoperiod; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D007453:Iodide Peroxidase; D013974:Thyroxine; D014284:Triiodothyronine; D000097564:Iodothyronine Deiodinase Type II; C117274:iodothyronine deiodinase type III