While it has been hypothesized that brown adipocytes responsible for mammalian thermogenesis are absent in birds, the existence of beige fat has yet to be studied directly. The present study tests the hypothesis that beige fat emerges in birds as a mechanism of physiological adaptation to cold environments. Subcutaneous neck adipose tissue from cold-acclimated or triiodothyronine (T₃)-treated chickens exhibited increases in the expression of avian uncoupling protein (avUCP, an ortholog of mammalian UCP2 and UCP3) gene and some known mammalian beige adipocyte-specific markers. Morphological characteristics of white adipose tissues of treated chickens showed increased numbers of both small and larger clusters of multilocular fat cells within the tissues. Increases in protein levels of avUCP and mitochondrial marker protein, voltage-dependent anion channel, and immunohistochemical analysis for subcutaneous neck fat revealed the presence of potentially thermogenic mitochondria-rich cells. This is the first evidence that the capacity for thermogenesis may be acquired by differentiating adipose tissue into beige-like fat for maintaining temperature homeostasis in the subcutaneous fat ‘neck warmer’ in chickens exposed to a cold environment.

虽然有人假设鸟类中不存在负责哺乳动物产热的棕色脂肪细胞，但尚未直接研究米色脂肪的存在。本研究检验了鸟类中出现的米色脂肪是对寒冷环境的生理适应机制的假设。来自冷驯化或三碘甲状腺原氨酸 (T ₃ ) 处理的鸡的皮下颈部脂肪组织表现出禽类解偶联蛋白（avUCP，哺乳动物 UCP2 和 UCP3 的直向同源物）的表达增加) 基因和一些已知的哺乳动物米色脂肪细胞特异性标记物。处理过的鸡的白色脂肪组织的形态特征显示组织内多房脂肪细胞的小簇和大簇数量增加。avUCP 和线粒体标记蛋白、电压依赖性阴离子通道和皮下颈部脂肪的免疫组织化学分析的蛋白质水平的增加揭示了潜在的富含产热线粒体的细胞的存在。这是第一个证据表明，可以通过将脂肪组织分化为米色样脂肪来维持暴露于寒冷环境的鸡的皮下脂肪“颈部加热器”中的温度稳态，从而获得产热能力。