Institute of Neurobiology, Ulm University, Ulm, Germany.
Data Sciences International, St. Paul, Minnesota, United States.
Am J Physiol Regul Integr Comp Physiol. 2023 Oct 1;325(4):R359-R379. doi: 10.1152/ajpregu.00040.2023. Epub 2023 Jul 31.
Djungarian hamsters use daily torpor to save energy during winter. This metabolic downstate is part of their acclimatization strategy in response to short photoperiod and expressed spontaneously without energy challenges. During acute energy shortage, torpor incidence, depth, and duration can be modulated. Torpor induction might rely on glucose availability as acute metabolic energy source. To investigate this, the present study provides the first continuous in vivo blood glucose measurements of spontaneous daily torpor in short photoperiod-acclimated and fasting-induced torpor in long photoperiod-acclimated Djungarian hamsters. Glucose levels were almost identical in both photoperiods and showed a decrease during resting phase. Further decreases appeared during spontaneous daily torpor entrance, parallel with metabolic rate but before body temperature, while respiratory exchange rates were rising. During arousal, blood glucose tended to increase, and pretorpor values were reached at torpor termination. Although food-restricted hamsters underwent a considerable energetic challenge, blood glucose levels remained stable during the resting phase regardless of torpor expression. The activity phase preceding a torpor bout did not reveal changes in blood glucose that might be used as torpor predictor. Djungarian hamsters show a robust, circadian rhythm in blood glucose irrespective of season and maintain appropriate levels throughout complex acclimation processes including metabolic downstates. Although these measurements could not reveal blood glucose as proximate torpor induction factor, they provide new information about glucose availability during torpor. Technical innovations like in vivo microdialysis and in vitro transcriptome or proteome analyses may help to uncover the connection between torpor expression and glucose metabolism.
沙鼠在冬季通过每日蛰伏来节省能量。这种代谢状态是它们对短光照周期适应策略的一部分，且无需能量挑战即可自发表现出来。在急性能量短缺时，蛰伏的发生率、深度和持续时间可以被调节。蛰伏的诱导可能依赖于葡萄糖作为急性代谢能量源的可用性。为了研究这一点，本研究首次提供了在短光照周期适应和长光照周期适应的沙鼠在禁食诱导的蛰伏中自发性每日蛰伏的连续体内血糖测量。两种光照周期下的血糖水平几乎相同，且在休息阶段下降。在自发性每日蛰伏进入时，血糖进一步下降，与代谢率平行，但在体温下降之前，而呼吸交换率上升。在觉醒时，血糖有升高的趋势，在蛰伏结束时达到预蛰伏值。尽管限食的沙鼠经历了相当大的能量挑战，但在休息阶段血糖水平仍然保持稳定，无论是否表现出蛰伏。在蛰伏发作前的活动阶段，血糖没有变化，这些变化可能无法作为蛰伏的预测因子。沙鼠表现出强大的、昼夜节律的血糖，无论季节如何，在包括代谢状态下降在内的复杂适应过程中都能维持适当的水平。尽管这些测量无法揭示血糖作为直接诱导蛰伏的因素，但它们提供了有关蛰伏期间葡萄糖可用性的新信息。像体内微透析和体外转录组或蛋白质组分析等技术创新可能有助于揭示蛰伏表达和葡萄糖代谢之间的联系。
