热中性区漂移对黑线仓鼠最大持续能量收支限制的影响及生理机制研究

Thermal neutral zone (TNZ), one of the most important physiological and ecological characteristics, plays a key role in coping with ambient temperature and improving the capacity of survival and adaptation. The sustained energy intake / metabolic rate (SusEI/MR) plays an important role in influencing geographical distribution, survival and adaptation, as well as reproductive success. SusEI/MR usually reaches a ceiling in small mammals; however the factors and mechanisms of limitation remain uncertain. Ambient temperature is known to be the main environmental factor, but the characteristics of TNZ shift with temperature and the mechanisms underpinning the relationships between TNZ shift and SusEI/MR limitation are far from clear. In this project, striped hamsters will be exposed to upper and lower point of TNZ, subjected to supplement of uncoupler and prolactin. Energy metabolism, thermal conductance, TNZ, tissue mitochondrial protein oxygen consumption, serum prolactin, as well as mRNA and protein expression of hypothalamic neuropeptides associated food intake regulation and tissue uncoupling proteins (UCPs) will be examined. This project is aimed to explore the characteristics and mechanisms of TNZ shift, and elucidate the link between heat dissipation limitation and SusEI/MR. The heat dissipation limitation hypothesis will be further examined, providing an insight into the SusEI/MR limitation. Finally, the findings from this project will be a great help to elucidate adaptive significance and survival mechanisms in response to ambient temperature changes in small mammals.

热中性区（TNZ）是小型哺乳动物的重要生理生态学特征之一，对其应对环境温度变化、提高生存适应能力具有重要意义。最大持续能量收支（SusEI/MR）在决定物种的地理分布、生存适应、繁殖成功等方面发挥具有作用。动物SusEI/MR均存在瓶颈，但限制因素和机制尚不清楚。温度是影响SusEI/MR的主要环境因子，但TNZ随温度漂移的特征与SusEI/MR之间的联系及内在机制尚不明确。本项目拟通过TNZ上下临界温度驯化、添加解耦联剂、外源催乳素处理等实验内容，研究黑线仓鼠能量代谢、热传导率、TNZ、组织线粒体呼吸耗氧速率、血清催乳素、下丘脑与摄食调控相关神经肽和组织解偶联蛋白（UCPs）表达等，旨在探讨不同环境温度下TNZ的漂移规律与机理，阐明热耗散限制与SusEI/MR的内在联系，进一步检验“热耗散限制假说”，深入理解SusEI/MR限制机理，揭示小型哺乳动物应对温度变化的生存机制和适应意义。

热中性区（TNZ）是小型哺乳动物的重要生理生态学特征之一，对其应对环境温度变化、提高生存适应能力具有重要意义。最大持续能量收支（SusEI/MR）在决定物种的地理分布、生存适应、繁殖成功等方面发挥具有作用。本项目研究了TNZ上下临界温度驯化、添加解耦联剂、外源催乳素处理对黑线仓鼠能量摄入和繁殖输出的影响，测定了能量代谢、热传导率、组织线粒体呼吸耗氧速率、血清催乳素、下丘脑与摄食调控相关神经肽和组织解偶联蛋白（UCPs）表达等。结果发现，TNZ受环境温度的影响, 随温度降低向下漂移，褐色脂肪组织（BAT）、肝脏和骨骼肌线粒体蛋白细胞色素c氧化酶活性显著增加。TNZ下临界温度组BAT 解偶联蛋白1（ucp1）mRNA表达显著上调。TNZ上临界温度使哺乳期摄食量、摄入能、消化能显著减少，乳腺泌乳能量支出显著减少，胎仔重量显著降低。上临界温度组热传导率显著降低，BAT ucp1表达、下丘脑神经肽Y（NPY）表达显著下调。哺育更多胎仔数的黑线仓鼠受上临界温度的影响更显著。解偶联剂（DNP）使热传导率显著降低、体温显著升高、哺乳期能量摄入降低、泌乳能量支出和胎仔重显著降低、血清催乳素显著降低，使BAT ucp1表达显著下调。外源催乳素注射对哺乳期能量摄入和泌乳支出的影响不显著。研究表明，黑线仓鼠TNZ范围广和漂移使其应对环境温度变化的能力增强，低温下代谢产热增加，代谢活性器官氧化磷酸化效率增强，UCP1表达显著上调是TNZ漂移的主要生理机制。当环境温度达到TNZ上临界点时发生SusEI/MR限制。进一步揭示了哺乳期热耗散限制与SusEI/MR的内在联系，暖温（上临界点温度）热传导率降低、下丘脑与摄食调控相关的神经肽表达下调是热耗散限制的神经内分泌机制之一。进一步阐明了小型哺乳动物应对低温和暖温的能量学策略和适应意义。