Water–fat MRI in a hibernator reveals seasonal growth of white and brown adipose tissue without cold exposure
Water–fat MRI in a hibernator reveals seasonal growth of white and brown adipose tissue without cold exposure
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冬眠者中的水脂肪 MRI 显示白色和棕色脂肪组织的季节性生长，无需寒冷暴露
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
J. F. Staples
中科院分区：
文献类型：
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作者：
Amanda D. V. MacCannell;Kevin J. Sinclair;Lannette Friesen;C. McKenzie;J. F. Staples
专性冬眠动物，如地松鼠，即使在恒定的实验室条件下，也表现出每年循环一次的模式，这表明它们是由内源性节律调节的。棕色脂肪组织（BAT）在冬眠中周期性觉醒时，当核心体温自发地从5°C上升到37°C时，对产热很重要。在大多数小型真核动物中，BAT的生长需要几个星期的低温暴露。我们假设，在冬眠动物十三纹地松鼠（Ictidomys tridecemlineatus）中，BAT的生长在一定程度上受到内源性节律的调节，我们预测这种生长将在没有寒冷暴露的冬眠季节之前发生。我们在一年多的时间里（包括冬眠季节）反复使用水脂肪磁共振成像来测试这一预测。从春季到秋季，即使动物被安置在~22°C的环境中，胸部BAT储存库的体积也在增加。随后的低温暴露（5°C）进一步扩大了胸椎BAT。该组织的脂肪部分在生长高峰期间显著下降，表明非甘油三酯成分（可能是线粒体或脉管系统）相对增加。我们还发现，由白色脂肪组织（WAT）组成的身体比例从春季到秋季稳步增加，并在整个冬眠期间下降，反映了体重的变化。与BAT不同，WAT脂肪含量全年保持不变（接近90%）。未来的研究将评估光周期和冷暴露对这些组织生长的意义。我们还在头部靠近眼睛的地方发现了具有BAT特征的脂肪部分组织，这是一个潜在的新发现，需要进一步证实。
Obligate hibernators, such as ground squirrels, display circannual patterns which persist even under constant laboratory conditions, suggesting that they are regulated by endogenous rhythms. Brown adipose tissue (BAT) is important for thermogenesis during periodic arousals from hibernation when core body temperature rises spontaneously from 5 to 37 °C. In most small eutherians BAT growth requires several weeks of cold exposure. We hypothesized that in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), a hibernator, BAT growth is regulated, in part, by an endogenous rhythm and we predicted that this growth would precede the hibernation season without cold exposure. We tested this prediction using repeated water–fat magnetic resonance imaging over a year, including the hibernation season. Thoracic BAT depots increased in volume from spring through autumn even though animals were housed at ~22 °C. Subsequent cold exposure (5 °C) enlarged the thoracic BAT further. The fat fraction of this tissue fell significantly during the period of peak growth, indicating relative increases in non-triglyceride components, perhaps mitochondria or vasculature. We also found that the proportion of the body consisting of white adipose tissue (WAT) increased steadily from spring through autumn, and fell throughout hibernation, mirroring changes in body mass. Unlike BAT, WAT fat fractions remained constant (near 90%) throughout the year. Future studies will evaluate the significance of photoperiod and cold exposure on the growth of these tissues. We also found tissue with a fat fraction characteristic of BAT in the head near the eyes, a potentially novel discovery that requires further confirmation.
影响因子：
19.7
作者：
Hines, Catherine D. G.;Yu, Huanzhou;Reeder, Scott B.
通讯作者：
Reeder, Scott B.
影响因子：
2.8
作者：
Runcie, Rosa M.;Dewar, Heidi;Dickson, Kathryn A.
通讯作者：
Dickson, Kathryn A.