Nakano Shin-ichi, Nakamura Katsuyuki, Teramoto Naomi, Yamanouchi Keitaro, Nishihara Masugi
Department of Veterinary Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Anim Sci J. 2016 Jan;87(1):99-108. doi: 10.1111/asj.12397. Epub 2015 Jul 8.
Intramuscular adipose tissue (IMAT) formation is a hallmark of marbling in cattle. IMAT is considered to originate from skeletal muscle progenitor cells with adipogenic potential. However, the mechanism involved in IMAT formation from these progenitor cells in vivo remains unclear. In the present study, among the growth factors tested, which were known to be expressed in skeletal muscle, we found only basic fibroblast growth factor (bFGF) has a pro-adipogenic effect on skeletal muscle derived adipogenic progenitor clone, 2G11 cells. Pre-exposure of 2G11 cells to bFGF did not affect initial gene expressions of CCAAT/enhancer-binding protein (C/EBP)β and C/EBPδ, while resulting in an enhancement of subsequent expressions of C/EBPα and proliferator-activated receptor gamma (PPARγ) during adipogenesis, indicating that bFGF is acting on the transcriptional regulation of C/EBPα and PPARγ. In addition, the effect of bFGF is mediated via two types of FGF receptor (FGFR) isoforms: FGFR1 and FGFR2 IIIc, and both receptors are prerequisite for bFGF to express its pro-adipogenic effect. These results suggest that bFGF plays an important role as a key trigger of IMAT formation in vivo.
肌内脂肪组织（IMAT）的形成是牛大理石花纹的一个标志。IMAT被认为起源于具有成脂潜力的骨骼肌祖细胞。然而，这些祖细胞在体内形成IMAT所涉及的机制仍不清楚。在本研究中，在测试的已知在骨骼肌中表达的生长因子中，我们发现只有碱性成纤维细胞生长因子（bFGF）对骨骼肌来源的成脂祖细胞克隆2G11细胞具有促脂肪生成作用。将2G11细胞预先暴露于bFGF不会影响CCAAT/增强子结合蛋白（C/EBP）β和C/EBPδ的初始基因表达，而在脂肪生成过程中会导致C/EBPα和增殖激活受体γ（PPARγ）后续表达的增强，这表明bFGF作用于C/EBPα和PPARγ的转录调控。此外，bFGF的作用是通过两种成纤维细胞生长因子受体（FGFR）亚型介导的：FGFR1和FGFR2 IIIc，并且这两种受体都是bFGF发挥其促脂肪生成作用的先决条件。这些结果表明，bFGF作为体内IMAT形成的关键触发因素起着重要作用。
