State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Comp Biochem Physiol C Toxicol Pharmacol. 2019 Feb;216:101-109. doi: 10.1016/j.cbpc.2018.11.016. Epub 2018 Nov 23.
Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T) in small mammals. Here, we hypothesized that T affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different Ts (5 °C, 23 °C and 37 °C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5 °C but decreased at 37 °C compared to the control (23 °C). Protein carbonyls increased in liver at 37 °C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T. After the effects of different Ts on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different Ts.
氧化损伤是小型哺乳动物季节性适应空气温度 (T) 时体温调节的潜在生理代价。在这里，我们假设 T 会影响血清甲状腺激素水平，而这些激素可以调节代谢率和氧化损伤的变化。我们将蒙古沙鼠（Meriones unguiculatus）在 5°C、23°C 和 37°C 下分别适应 3 周。与对照组（23°C）相比，血清三碘甲状腺原氨酸 (T3) 水平在 5°C 时升高，但在 37°C 时降低。与对照组相比，37°C 时肝脏中的蛋白质羰基增加，但血清和肝脏中的脂质损伤（丙二醛，MDA）与 T 无关。在确定不同 T 对甲状腺激素水平和氧化损伤标志物的影响后，我们进一步研究甲状腺激素是否介导代谢率和氧化损伤。另一组沙鼠接受了 0.0036% L-甲状腺素（甲状腺功能亢进）、0.04% Methylimazol（甲状腺功能减退）或水（对照组）。甲状腺功能减退组的静息代谢率（RMR）降低了 34%，MDA 和肝蛋白羰基分别增加了 42%和 26%，而甲状腺功能亢进组的 RMR、肝质量和超氧化物歧化酶（SOD）均高于对照组。血清 T3 或 T3/T4 水平与 RMR、肝质量和 SOD 呈正相关，与 MDA 和解偶联蛋白 2 (UCP2) 呈负相关。我们得出结论，高 T 诱导甲状腺功能减退，降低 RMR 并增加氧化损伤，而低 T 诱导甲状腺功能亢进，增加 RMR 且氧化损伤不变。这些数据支持我们的假设，即甲状腺激素可以作为调节不同 T 下代谢率和氧化与抗氧化活动不同方面的线索。
