Zagkle Elisavet, Grosiak Marta, Bauchinger Ulf, Sadowska Edyta T
Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Krakow, Poland.
Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
Front Physiol. 2020 Dec 9;11:575060. doi: 10.3389/fphys.2020.575060. eCollection 2020.
In endotherms, growth, reproduction, and survival are highly depended on energy metabolism. Maintenance of constant body temperature can be challenging for endotherms under continuously changing environmental conditions, such as low or high ambient temperatures or limited food. Thus, many birds may drop body temperature below normothermic values during the night, known as rest-phase hypothermia, presumably to decrease energy metabolism. Under the assumption of the positive link between aerobic metabolism and reactive oxygen species, it is reasonable to suggest that low body temperature, a proxy of energy metabolism, will affect oxidative stress of the birds. Aging may considerably affect behavior, performance and physiology in birds and still requires further investigation to understand age-specific changes along the lifespan of the organism. Until today, age-specific rest-phase hypothermic responses and their effect on oxidant-antioxidant status have never been investigated. We exposed 25 zebra finches () of three age classes, 12 young birds (1.1-1.3 years old), 8 middle-aged (2.4-2.8 years old), and 5 old birds (4.2-7.5 years old) to day-long food deprivation or provided them normal access to food under thermoneutral conditions. We compared night-time body temperature, measured through implanted data loggers, and quantified plasma oxidative status (uric acid, antioxidant capacity, and d-ROM assay) the following morning. We found age-related differences in night-time body temperature following a day-long food deprivation while all three age groups remained normothermic in the night following a day with access to food. The lowest minimum body temperature (LSM ± SE: 36.6 ± 0.2°C) was observed in old individuals during rest-phase hypothermia. Surprisingly, these old birds also revealed the highest levels of plasma oxidative damage, while young and middle-aged birds maintained higher night-time body temperature and showed lower values of oxidative damage. These results lead us to propose a novel hypothesis on how aging may lead to an accumulation of oxidative damage; the impaired physiological capacity to thermoregulate with advancing age does increase the risk of oxidative stress under challenging conditions. When energy is limited, the risk to encounter oxidative stress is increasing via a compensation to defend normothermic body temperatures.
在恒温动物中，生长、繁殖和生存高度依赖能量代谢。在不断变化的环境条件下，如低温或高温环境温度或食物有限时，维持恒定体温对恒温动物来说可能具有挑战性。因此，许多鸟类在夜间可能会将体温降至正常体温以下，即所谓的休息期低温，大概是为了降低能量代谢。基于有氧代谢与活性氧之间存在正相关的假设，有理由认为低温作为能量代谢的一个指标，会影响鸟类的氧化应激。衰老可能会显著影响鸟类的行为、性能和生理机能，仍需要进一步研究以了解生物体一生中特定年龄的变化。直到今天，特定年龄的休息期低温反应及其对氧化还原状态的影响从未被研究过。我们将25只三个年龄组的斑胸草雀（），12只幼鸟（1.1 - 1.3岁）、8只中年鸟（2.4 - 2.8岁）和5只老年鸟（4.2 - 7.5岁）置于全天食物剥夺状态，或在热中性条件下让它们正常获取食物。我们通过植入的数据记录器测量夜间体温，并在第二天早晨量化血浆氧化状态（尿酸、抗氧化能力和d-ROM检测）。我们发现，在全天食物剥夺后，夜间体温存在年龄相关差异，而在有食物供应的一天后的夜间，所有三个年龄组均保持正常体温。在休息期低温期间，老年个体的最低体温最低（最小二乘均值±标准误：36.6±0.2°C）。令人惊讶的是，这些老年鸟还表现出最高水平的血浆氧化损伤，而幼鸟和中年鸟则保持较高的夜间体温，并表现出较低的氧化损伤值。这些结果使我们提出了一个关于衰老如何导致氧化损伤积累的新假设；随着年龄增长，体温调节生理能力受损确实会增加在具有挑战性条件下氧化应激的风险。当能量有限时，通过补偿以维持正常体温，遭遇氧化应激的风险会增加。
