Department of Biology, University of Western Ontario, London, ON, Canada, N6A 5B8
J Exp Biol. 2014 Jun 15;217(Pt 12):2032-6. doi: 10.1242/jeb.092973.
Hibernation evolved in some small mammals that live in cold environments, presumably to conserve energy when food supplies are low. Throughout the winter, hibernators cycle spontaneously between torpor, with low metabolism and near-freezing body temperatures, and euthermia, with high metabolism and body temperatures near 37°C. Understanding the mechanisms underlying this natural model of extreme metabolic plasticity is important for fundamental and applied science. During entrance into torpor, reductions in metabolic rate begin before body temperatures fall, even when thermogenesis is not active, suggesting active mechanisms of metabolic suppression, rather than passive thermal effects. Mitochondrial respiration is suppressed during torpor, especially when measured in liver mitochondria fuelled with succinate at 37°C in vitro. This suppression of mitochondrial metabolism appears to be invoked quickly during entrance into torpor when body temperature is high, but is reversed slowly during arousal when body temperature is low. This pattern may reflect body temperature-sensitive, enzyme-mediated post-translational modifications of oxidative phosphorylation complexes, for instance by phosphorylation or acetylation.
冬眠是在一些生活在寒冷环境中的小型哺乳动物中进化而来的，可能是为了在食物供应不足时节省能量。在整个冬季，冬眠动物会在蛰伏（代谢率低，体温接近冰点）和正常体温（代谢率高，体温接近 37°C）之间自发地循环。了解这种极端代谢灵活性的自然模型背后的机制对于基础科学和应用科学都很重要。在进入蛰伏状态时，即使产热不活跃，代谢率的降低也会在体温下降之前开始，这表明存在主动的代谢抑制机制，而不是被动的热效应。在蛰伏期间，线粒体呼吸受到抑制，尤其是在体外以琥珀酸为燃料、在 37°C 下测量肝线粒体呼吸时。这种线粒体代谢的抑制似乎在体温较高时快速进入蛰伏时被触发，但在体温较低时缓慢逆转。这种模式可能反映了体温敏感的、酶介导的氧化磷酸化复合物的翻译后修饰，例如通过磷酸化或乙酰化。
