Supplementary Material for: Administration of Thyrotropin-Releasing Hormone in the Hypothalamic Paraventricular Nucleus of Male Rats Mimics the Metabolic Cold Defense Response

<b><i>Background:</i></b> Cold exposure increases thyrotropin-releasing hormone (TRH) expression primarily in the hypothalamic paraventricular nucleus (PVN). The PVN is a well-known hypothalamic hub in the control of energy metabolism. TRH terminals and receptors are found on PVN neurons. We hypothesized that TRH release in the PVN plays an important role in the control of thermogenesis and energy mobilization during cold exposure. <b><i>Methods:</i></b> Male Wistar rats were exposed to a cold environment (4°C) or TRH retrodialysis in the PVN for 2 h. We compared the effects of cold exposure and TRH administration in the PVN on plasma glucose, corticosterone, and thyroid hormone concentrations, body temperature, locomotor activity, as well as metabolic gene expression in the liver and brown adipose tissue. <b><i>Results:</i></b> Cold exposure increased body temperature, locomotor activity, and plasma corticosterone concentrations, but blood glucose concentrations were similar to that of room temperature control animals. TRH administration in the PVN also promptly increased body temperature, locomotor activity and plasma corticosterone concentrations. However, TRH administration in the PVN markedly increased blood glucose concentrations and endogenous glucose production (EGP) compared to saline controls. Selective hepatic sympathetic or parasympathetic denervation reduced the TRH-induced increase in glucose concentrations and EGP. Gene expression data indicated increased gluconeogenesis in liver and lipolysis in brown adipose tissue, both after cold exposure and TRH administration. <b><i>Conclusions:</i></b> We conclude that TRH administration in the rat PVN largely mimics the metabolic and behavioral changes induced by cold exposure indicating a potential link between TRH release in the PVN and cold defense.

**研究背景**：寒冷暴露主要会促进下丘脑室旁核（hypothalamic paraventricular nucleus, PVN）中促甲状腺激素释放激素（thyrotropin-releasing hormone, TRH）的表达。下丘脑室旁核是调控能量代谢的经典下丘脑调控中枢，其神经元上存在促甲状腺激素释放激素的轴突终末与受体。本研究推测，寒冷暴露时下丘脑室旁核内的促甲状腺激素释放激素释放，在产热调控与能量动员过程中发挥重要作用。
**研究方法**：将雄性Wistar大鼠置于4℃寒冷环境中，或对其下丘脑室旁核进行2小时的促甲状腺激素释放激素逆向微透析给药。本研究对比了寒冷暴露与下丘脑室旁核给予促甲状腺激素释放激素，对大鼠血浆葡萄糖、皮质酮、甲状腺激素水平，体温、运动活性，以及肝脏与棕色脂肪组织中代谢相关基因表达的影响。
**研究结果**：寒冷暴露可提升大鼠体温、运动活性与血浆皮质酮水平，但血糖水平与室温对照组大鼠无显著差异。下丘脑室旁核给予促甲状腺激素释放激素，同样可快速提升大鼠体温、运动活性与血浆皮质酮水平。但与生理盐水对照组相比，下丘脑室旁核给予促甲状腺激素释放激素可显著升高血糖水平与内源性葡萄糖生成（endogenous glucose production, EGP）量。选择性对肝脏进行交感或副交感神经切除，可削弱促甲状腺激素释放激素诱导的血糖与内源性葡萄糖生成量升高幅度。基因表达数据分析显示，无论是寒冷暴露还是下丘脑室旁核给予促甲状腺激素释放激素处理，大鼠肝脏内糖异生作用与棕色脂肪组织内脂解作用均显著增强。
**研究结论**：本研究得出结论：对大鼠下丘脑室旁核给予促甲状腺激素释放激素，可在很大程度上模拟寒冷暴露诱导的代谢与行为变化，这提示下丘脑室旁核内促甲状腺激素释放激素的释放与寒冷防御机制之间存在潜在关联。