Abd Eldaim M A, Hashimoto O, Ohtsuki H, Yamada T, Murakami M, Onda K, Sato R, Kanamori Y, Qiao Y, Tomonaga S, Matsui T, Funaba M
J Anim Sci. 2016 Dec;94(12):5097-5104. doi: 10.2527/jas.2016-0726.
Uncoupling protein 1 (Ucp1) is predominantly expressed in brown/beige adipocytes in mammals. Although myogenic cells have been suggested to commit to a brown adipocyte lineage through the induction of Prdm16 expression, Prdm16 is also expressed in skeletal muscle. Thus, we examined expression of Ucp1 in bovine myogenic cells. Considering that Ucp1 is a principle molecule that induces energy expenditure in brown/beige adipocytes, expression of Ucp1 is not preferable in beef cattle because of potential decrease in energy (fattening) efficiency. The RT-PCR analyses revealed the expression of Ucp1 in the skeletal muscle of cattle; expression levels were markedly lower than those in the brown fat of calves. Immunohistochemical analyses showed that Ucp1 surrounded muscle fibers, but not adipocytes residing in skeletal muscle. Myosatellite cells cultured in myogenic medium showed an increase in the expression levels of myogenic regulatory factors ( < 0.05), while those in cells cultured in adipogenic medium were decreased ( < 0.05). The Ucp1 expression was also detected in myosatellite cells; expression levels were greater in cells after myogenic culture for 12 d than in those after myogenic culture for 6 d ( < 0.05) and were decreased when cells were cultured in adipogenic medium ( < 0.05). The Prdm16 expression was not affected by culture conditions, suggesting that the expression of Ucp1 is not regulated by that of Prdm16. The results of the present study provide an insight into the unexpected expression of Ucp1 in bovine skeletal muscle, which suggests the necessity for further studies on Ucp1-mediated energy expenditure in bovine skeletal muscle.
解偶联蛋白1（Ucp1）主要在哺乳动物的棕色/米色脂肪细胞中表达。尽管有研究表明，通过诱导Prdm16的表达，成肌细胞可分化为棕色脂肪细胞系，但Prdm16在骨骼肌中也有表达。因此，我们检测了牛成肌细胞中Ucp1的表达。鉴于Ucp1是诱导棕色/米色脂肪细胞能量消耗的主要分子，Ucp1在肉牛中的表达可能会降低能量（育肥）效率，因此并不理想。逆转录聚合酶链反应（RT-PCR）分析显示，牛骨骼肌中存在Ucp1的表达；其表达水平明显低于犊牛棕色脂肪中的表达水平。免疫组织化学分析表明，Ucp1环绕着肌纤维，但不环绕骨骼肌中的脂肪细胞。在成肌培养基中培养的肌卫星细胞，其成肌调节因子的表达水平有所增加（<0.05），而在脂肪生成培养基中培养的细胞，其成肌调节因子的表达水平则降低（<0.05）。在肌卫星细胞中也检测到了Ucp1的表达；成肌培养12天的细胞中Ucp1的表达水平高于成肌培养6天的细胞（<0.05），而在脂肪生成培养基中培养时，Ucp1的表达水平则降低（<0.05）。Prdm16的表达不受培养条件的影响，这表明Ucp1的表达不受Prdm16的调控。本研究结果为牛骨骼肌中Ucp1的意外表达提供了见解，这表明有必要进一步研究Ucp1介导的牛骨骼肌能量消耗。
