The role of hypothalamic tri-iodothyronine availability in seasonal regulation of energy balance and body weight.
The role of hypothalamic tri-iodothyronine availability in seasonal regulation of energy balance and body weight.
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DOI：
10.4061/2011/387562
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发表时间：
2011
影响因子：
2.1
通讯作者：
Ebling FJ
中科院分区：
文献类型：
--
作者：
Murphy M;Ebling FJ
体重的季节性循环提供了一个自然的模型系统，以了解能量平衡的中央控制。对西伯利亚仓鼠的这种周期的研究表明，甲状腺激素的下丘脑可用性的变化是每年体重调节的关键决定因素。甲状腺激素从外周循环摄取到下丘脑主要是通过第三脑室内的伸展细胞表达的特异性单羧酸转运蛋白。伸长细胞是表达II型和III型脱碘酶的主要脑细胞类型，因此它们控制T4、T3和非活性代谢物的局部浓度。III型脱碘酶mRNA在伸长细胞是光周期性上调短光周期。预计这将通过促进非活性代谢物如rT3的产生来减少下丘脑中T3的可用性。实验性T3直接微植入下丘脑在短日促进长日表型通过增加食物摄入量和体重，而不影响外周甲状腺轴。因此，甲状腺激素在大脑中发挥合成代谢作用，在体重的季节性调节中发挥关键作用。了解甲状腺激素在大脑中的确切作用可能会为长期药理学操纵体重确定新的目标。
Seasonal cycles of body weight provide a natural model system to understand the central control of energy balance. Studies of such cycles in Siberian hamsters suggest that a change in the hypothalamic availability of thyroid hormone is the key determinant of annual weight regulation. Uptake of thyroid hormone into the hypothalamus from the peripheral circulation occurs largely through a specific monocarboxylate transporter expressed by tanycyte cells lining the third ventricle. Tanycytes are the principal brain cell type expressing type II and type III deiodinases, so they control the local concentrations of T4, T3, and inactive metabolites. Type III deiodinase mRNA in tanycytes is photoperiodically upregulated in short photoperiod. This would be expected to reduce the availability of T3 in the hypothalamus by promoting the production of inactive metabolites such as rT3. Experimental microimplantation of T3 directly into the hypothalamus during short-days promotes a long-day phenotype by increasing food intake and body weight without affecting the peripheral thyroid axis. Thus, thyroid hormone exerts anabolic actions within the brain that play a key role in the seasonal regulation of body weight. Understanding the precise actions of thyroid hormone in the brain may identify novel targets for long-term pharmacological manipulation of body weight.