Effects of Manipulating Hypothalamic Triiodothyronine Concentrations on Seasonal Body Weight and Torpor Cycles in Siberian Hamsters
Effects of Manipulating Hypothalamic Triiodothyronine Concentrations on Seasonal Body Weight and Torpor Cycles in Siberian Hamsters
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DOI：
10.1210/en.2011-1249
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发表时间：
2012-01-01
期刊：
影响因子：
4.8
通讯作者：
Ebling, Francis J. P.
中科院分区：
文献类型：
--
作者：
Murphy, Michelle;Jethwa, Preeti H.;Ebling, Francis J. P.
西伯利亚仓鼠显示光周期调节的体重，食欲和繁殖的年周期。先前的研究已经揭示了下丘脑腹侧室管膜中3型脱碘酶（DIO 3）mRNA的显著上调与短日照下的摄食减少和体重减轻相关。DIO 3降低了T-3的局部可用性，因此本研究的目的是检验下丘脑T-3可用性降低是短日照诱导的分解代谢状态的基础这一假设。实验方法是确定是否局部增加T-3在仓鼠下丘脑暴露于短的日子可以扭转这种光周期引起的行为和生理变化。在研究1中，将释放T-3的微植入物置于双侧下丘脑中。该处理迅速诱导长日照表型，包括在处理3周内食欲和体重增加，以及在10周研究期结束时脂肪量和睾丸大小增加。在研究2中，将下丘脑T-3植入物置于携带腹部无线电遥测植入物的仓鼠中。体重再次显著增加，冬季麻痹发作的发生率显著降低至每周不到一次，而假植入仓鼠每周进入麻痹多达六次。我们的研究结果表明，增加中央T-3诱导长日照代谢表型，但在这两项研究中，蜕皮周期的影响，所以我们推断，我们没有破坏光周期的初始检测。我们的结论是，下丘脑甲状腺激素的可用性起着关键作用，在季节性调节食欲，体重，和麻木。（内分泌学153：101-112，2012）
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. We conclude that hypothalamic thyroid hormone availability plays a key role in seasonal regulation of appetite, body weight, and torpor. (Endocrinology 153: 101-112, 2012)