Effects of manipulating hypothalamic triiodothyronine concentrations on seasonal body weight and torpor cycles in Siberian hamsters

Murphy, Michelle; Jethwa, Preeti H.; Warner, Amy; Barrett, Perry; Nilaweera, Kanishka N.; Brameld, John M.; Ebling, Francis J.P.

Abstract

Siberian hamsters display photoperiodically regulated annual cycles in body weight, appetite, and reproduction. Previous studies have revealed a profound up-regulation of type 3 deiodinase (DIO3) mRNA in the ventral ependyma of the hypothalamus associated with hypophagia and weight loss in short-day photoperiods. DIO3 reduces the local availability of T 3, so the aim of this study was to test the hypothesis that decreased hypothalamic T 3 availability underlies the short-day-induced catabolic state. The experimental approach was to determine whether a local increase in T 3 in the hypothalamus of hamsters exposed to short days could reverse the behavioral and physiological changes induced by this photoperiod. In study 1, microimplants releasing T 3 were placed bilaterally into the hypothalamus. This treatment rapidly induced a long-day phenotype including increased appetite and body weight within 3 wk of treatment and increased fat mass and testis size by the end of the 10-wk study period. In study 2, hypothalamic T 3 implants were placed into hamsters carrying abdominal radiotelemetry implants. Again body weight increased significantly, and the occurrence of winter torpor bouts was dramatically decreased to less than one bout per week, whereas sham-implanted hamsters entered torpor up to six times a week. Our findings demonstrate that increased central T 3 induces a long-day metabolic phenotype, but in neither study was the molt cycle affected, so we infer that we had not disrupted the initial detection of photoperiod. Weconclude that hypothalamic thyroidhormoneavailability plays a key role in seasonal regulation of appetite, body weight, and torpor. Copyright © 2012 by The Endocrine Society.

Citation

Murphy, M., Jethwa, P. H., Warner, A., Barrett, P., Nilaweera, K. N., Brameld, J. M., & Ebling, F. J. (2012). Effects of manipulating hypothalamic triiodothyronine concentrations on seasonal body weight and torpor cycles in Siberian hamsters. Endocrinology, 153(1), 101-112. https://doi.org/10.1210/en.2011-1249

• Journal Article Type: Article
• Acceptance Date: Oct 4, 2011
• Online Publication Date: Jan 1, 2012
• Publication Date: Jan 1, 2012
• Deposit Date: Feb 9, 2021
• Journal: Endocrinology
• Print ISSN: 0013-7227
• Electronic ISSN: 1945-7170
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 153
• Issue: 1
• Pages: 101-112
• DOI: https://doi.org/10.1210/en.2011-1249
• Public URL: https://nottingham-repository.worktribe.com/output/3158374