Nespolo Roberto F, Mejias Carlos, Bozinovic Francisco
Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile.
Millenium Nucleus of Patagonian Limit of Life (LiLi) and Millennium Institute for Integrative Biology (iBio), Santiago, Chile.
Proc Biol Sci. 2022 Apr 27;289(1973):20220456. doi: 10.1098/rspb.2022.0456.
Hibernation is a natural state of suspended animation that many mammals experience and has been interpreted as an adaptive strategy for saving energy. However, the actual amount of savings that hibernation represents, and particularly its dependence on body mass (the 'scaling') has not been calculated properly. Here, we estimated the scaling of daily energy expenditure of hibernation (DEE), covering a range of five orders of magnitude in mass. We found that DEE scales isometrically with mass, which means that a gram of hibernating bat has a similar metabolism to that of a gram of bear, 20 000 times larger. Given that metabolic rate of active animals scales allometrically, the point where these scaling curves intersect with DEE represents the mass where energy savings by hibernation are zero. For BMR, these zero savings are attained for a relatively small bear (approx. 75 kg). Calculated on a per cell basis, the cellular metabolic power of hibernation was estimated to be 1.3 × 10 ± 2.6 × 10 W cell, which is lower than the minimum metabolism of isolated mammalian cells. This supports the idea of the existence of a minimum metabolism that permits cells to survive under a combination of cold and hypoxia.
冬眠是许多哺乳动物都会经历的一种自然的假死状态，被视为一种节省能量的适应性策略。然而，冬眠所代表的实际能量节省量，尤其是其对体重的依赖性（“标度关系”）尚未得到恰当计算。在此，我们估算了冬眠每日能量消耗（DEE）的标度关系，涵盖了五个数量级的体重范围。我们发现DEE与体重呈等比例缩放，这意味着一克冬眠的蝙蝠与2万倍于其体重的熊具有相似的新陈代谢。鉴于活跃动物的代谢率呈异速生长标度关系，这些标度曲线与DEE的交点所对应的体重，就是冬眠节省能量为零的体重。对于基础代谢率（BMR）而言，一只相对较小的熊（约75千克）就达到了这种零能量节省状态。按每个细胞计算，冬眠时细胞的代谢功率估计为1.3×10±2.6×10瓦/细胞，低于分离的哺乳动物细胞的最低代谢水平。这支持了存在一种最低代谢水平的观点，该水平能使细胞在寒冷和缺氧的组合条件下存活。
