Yudasaka Masako, Okamatsu-Ogura Yuko, Tanaka Takeshi, Saeki Kumiko, Kataura Hiromichi
Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8565, Japan.
Graduate School of Science and Technology, Meijo University, Nagoya 468-8502, Japan.
Acta Histochem Cytochem. 2021 Oct 29;54(5):131-141. doi: 10.1267/ahc.21-00030. Epub 2021 Oct 6.
Thermogenesis fatty acid-induced uncoupled mitochondrial respiration is the primary function of brown adipose tissue (BAT). In response to changes in ambient temperatures, the weight and specific gravity of BAT change, depending on the quantity of lipid droplets stored in brown adipocytes (BA). Such conditions should result in the reconstruction of connective tissue skeletons, especially of collagen fiber networks, although the mechanisms have not been clarified. This study showed that, within 4 hr of exposing mice to a cold environment, collagen fibers in the extracellular matrix (ECM) of BAT became discontinuous, twisted, emancipated, and curtailed. Surprisingly, the structure of collagen fibers returned to normal after the mice were kept at room temperature for 19 hr, indicating that the alterations in collagen fiber structures are physiological processes association with adaptation to cold environments. These dynamic changes in connective tissue skeletons were not observed in white adipose tissues, suggesting that they are unique to BAT. Interestingly, the vascular permeability of BAT was also augmented by exposure to cold. Collectively, these findings indicate that dynamic changes in ECM collagen fibers provide high flexibility to BAT, enabling the adjustment of tissue structures and the regulation of vascular permeability, resulting in adaptation to changes in ambient temperatures.
产热 脂肪酸诱导的解偶联线粒体呼吸是棕色脂肪组织（BAT）的主要功能。响应环境温度的变化，BAT的重量和比重会发生变化，这取决于棕色脂肪细胞（BA）中储存的脂滴数量。尽管其机制尚未阐明，但这种情况应该会导致结缔组织骨架，尤其是胶原纤维网络的重建。本研究表明，在将小鼠暴露于寒冷环境的4小时内，BAT细胞外基质（ECM）中的胶原纤维变得不连续、扭曲、松解并缩短。令人惊讶的是，在将小鼠置于室温19小时后，胶原纤维的结构恢复正常，这表明胶原纤维结构的改变是与适应寒冷环境相关的生理过程。在白色脂肪组织中未观察到结缔组织骨架的这些动态变化，表明它们是BAT所特有的。有趣的是，暴露于寒冷也会增加BAT的血管通透性。总的来说，这些发现表明ECM胶原纤维的动态变化为BAT提供了高度的灵活性，使其能够调整组织结构并调节血管通透性，从而适应环境温度的变化。
