Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.
Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany.
Front Endocrinol (Lausanne). 2024 Mar 19;15:1329083. doi: 10.3389/fendo.2024.1329083. eCollection 2024.
About 10% of all rodent species have evolved a subterranean way of life, although life in subterranean burrows is associated with harsh environmental conditions that would be lethal to most animals living above ground. Two key adaptations for survival in subterranean habitats are low resting metabolic rate (RMR) and core body temperature (T). However, the upstream regulation of these traits was unknown thus far. Previously, we have reported exceptionally low concentrations of the thyroid hormone (TH) thyroxine (T4), and peculiarities in TH regulating mechanisms in two African mole-rat species, the naked mole-rat and the Ansell's mole-rat.
In the present study, we treated Ansell's mole-rats with T4 for four weeks and analyzed treatment effects on the tissue and whole organism level with focus on metabolism and thermoregulation.
We found RMR to be upregulated by T4 treatment but not to the extent that was expected based on serum T4 concentrations. Our data point towards an extraordinary capability of Ansell's mole-rats to effectively downregulate TH signaling at tissue level despite very high serum TH concentrations, which most likely explains the observed effects on RMR. On the other hand, body weight was decreased in T4-treated animals and T was upregulated by T4 treatment. Moreover, we found indications of the hypothalamus-pituitary-adrenal axis potentially influencing the treatment effects.
Taken together, we provide the first experimental evidence that the low serum T4 concentrations of Ansell's mole-rats serve as an upstream regulator of low RMR and Tb. Thus, our study contributes to a better understanding of the ecophysiological evolution of the subterranean lifestyle in African mole-rats.
大约 10%的啮齿动物物种已经进化出了地下生活方式，尽管地下洞穴的生活与对大多数生活在地面上的动物来说致命的恶劣环境条件有关。在地下栖息地生存的两个关键适应是低静息代谢率（RMR）和核心体温（T）。然而，这些特征的上游调节至今尚不清楚。此前，我们报道了两种非洲鼹形鼠（裸鼹鼠和安塞尔氏鼹鼠）甲状腺激素（TH）甲状腺素（T4）浓度异常低，以及 TH 调节机制的特殊性。
在本研究中，我们用 T4 治疗 Ansell's mole-rats 四周，并分析了治疗对组织和整体生物体水平的影响，重点是代谢和体温调节。
我们发现 RMR 被 T4 治疗上调，但上调幅度与血清 T4 浓度预期的不符。我们的数据表明，尽管血清 TH 浓度非常高，但 Ansell's mole-rats 具有非凡的能力，可以有效地在组织水平下调 TH 信号，这很可能解释了观察到的 RMR 效应。另一方面，T4 处理动物的体重下降，T4 处理使 T 上调。此外，我们发现下丘脑-垂体-肾上腺轴可能影响治疗效果的迹象。
综上所述，我们提供了第一个实验证据，表明 Ansell's mole-rats 的低血清 T4 浓度是低 RMR 和 Tb 的上游调节剂。因此，我们的研究有助于更好地理解非洲鼹形鼠地下生活方式的生态生理进化。
