Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA; Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA; Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.
Department of Biology, University of Wisconsin-Oshkosh, 800 Algoma Boulevard, Oshkosh, WI 54901, USA.
Curr Biol. 2022 Apr 25;32(8):1822-1828.e4. doi: 10.1016/j.cub.2022.02.032. Epub 2022 Mar 3.
Adequate nutrition is essential for normal reproductive function, which is vital for species to survive. In humans and other mammals, starvation and undernutrition deplete fat reserves and cause weight loss, attenuating the function of the reproductive axis and causing hypogonadism. Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) spend 7 months of every year in hibernation without food and water. Hibernating squirrels alternate between periods of torpor and interbout arousal (IBA), when animals temporarily return to an active-like state. The physiological significance of IBA is unclear, but it is thought to be essential for hibernation in animals that drop their body temperature to 2°C-4°C during torpor. Here, we report that juvenile male ground squirrels initiate reproductive maturation during their first hibernation season, despite prolonged undernutrition and profound weight loss. We show that the hypothalamic reproductive axis undergoes activation during interbout arousals in the middle of hibernation, triggering production of luteinizing hormone and testosterone, and promoting testicular growth. Initiation of sexual maturation is circannually entrained and is independent of physiological state, ambient temperature, and food availability. Our study suggests a role for interbout arousals during hibernation and uncovers the neurophysiological mechanism of reproductive axis activation during conditions of extreme negative energy balance. VIDEO ABSTRACT.
充足的营养对于正常的生殖功能至关重要，而正常的生殖功能对于物种的生存至关重要。在人类和其他哺乳动物中，饥饿和营养不良会耗尽脂肪储备，导致体重减轻，从而削弱生殖轴的功能并导致性腺功能减退。十三线地松鼠（Ictidomys tridecemlineatus）每年有 7 个月处于不进食不饮水的冬眠状态。冬眠的地松鼠会在蛰伏期和间歇觉醒期（IBA）之间交替，在这期间动物会暂时恢复到活跃状态。IBA 的生理意义尚不清楚，但人们认为它对于那些在蛰伏期间体温降至 2°C-4°C 的动物的冬眠是必不可少的。在这里，我们报告说，幼年雄性地松鼠在第一个冬眠季节就开始了生殖成熟，尽管它们经历了长时间的营养不良和明显的体重减轻。我们发现，在下丘脑生殖轴在冬眠中期的间歇觉醒期会被激活，从而触发黄体生成素和睾酮的产生，并促进睾丸生长。性成熟的启动是按照年周期进行的，与生理状态、环境温度和食物供应无关。我们的研究表明，在冬眠期间间歇觉醒可能起到了作用，并揭示了在极端负能量平衡条件下生殖轴激活的神经生理机制。视频摘要。
