Seo Kangmin, Suzuki Takahiro, Kobayashi Ken, Nishimura Takanori
Laboratory of Cell and Tissue Biology, Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
Anim Sci J. 2019 Mar;90(3):423-434. doi: 10.1111/asj.13145. Epub 2018 Dec 25.
The development of adipose tissue in skeletal muscle is important for improving meat quality. However, it is still unclear how adipocytes grow in the proximity of muscle fibers. We hypothesized that adipocytes would suppress muscle cell growth so as to grow dominantly within muscle. In this study, we investigated the effect of adipocytes on the differentiation of muscle cells in a co-culture system. The fusion index of C2C12 myoblasts co-cultured with 3T3-L1 adipocytes was significantly lower than that of the control. The expression of myogenin and myosin heavy chain in C2C12 muscle cells co-cultured with 3T3-L1 adipocytes was significantly lower than in the control. Furthermore, the expression of Atrogin-1 and MuRF-1 was higher in C2C12 muscle cells co-cultured with 3T3-L1 adipocytes than the control. These results suggest that 3T3-L1 adipocytes suppress the differentiation of C2C12 myoblasts. In addition, 3T3-L1 adipocytes induced the expression and secretion of IL-6 in C2C12 muscle cells. The fusion index and myotube diameter were higher in C2C12 muscle cells co-cultured with 3T3-L1 cells in medium containing IL-6-neutralizing antibody than the control. Taken together, there is a possibility that adipocyte-induced IL-6 expression in muscle cells could be involved in the inhibition of muscle cell differentiation via autocrine.
骨骼肌中脂肪组织的发育对改善肉质很重要。然而，脂肪细胞如何在肌纤维附近生长仍不清楚。我们推测脂肪细胞会抑制肌肉细胞生长，以便在肌肉内占主导地位生长。在本研究中，我们在共培养系统中研究了脂肪细胞对肌肉细胞分化的影响。与3T3-L1脂肪细胞共培养的C2C12成肌细胞的融合指数显著低于对照组。与3T3-L1脂肪细胞共培养的C2C12肌肉细胞中肌细胞生成素和肌球蛋白重链的表达显著低于对照组。此外，与3T3-L1脂肪细胞共培养的C2C12肌肉细胞中Atrogin-1和MuRF-1的表达高于对照组。这些结果表明3T3-L1脂肪细胞抑制C2C12成肌细胞的分化。此外，3T3-L1脂肪细胞诱导C2C12肌肉细胞中IL-6的表达和分泌。在含有IL-6中和抗体的培养基中，与3T3-L1细胞共培养的C2C12肌肉细胞的融合指数和肌管直径高于对照组。综上所述，脂肪细胞诱导肌肉细胞中IL-6表达有可能通过自分泌参与肌肉细胞分化的抑制。
