Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX.
J Anim Sci. 2018 Jun 29;96(7):2763-2776. doi: 10.1093/jas/sky155.
All-trans retinoic acid (ATRA) has been associated with various physiological phenomenon in mammalian adipose tissue and skeletal muscle. We hypothesized that ATRA may affect skeletal muscle fiber type in bovine satellite cell culture through various transcriptional processes. Bovine primary satellite cell (BSC) culture experiments were conducted to determine dose effects of ATRA on expression of genes and protein levels related to skeletal muscle fiber type and metabolism. The semimembranosus from crossbred steers (n = 2 steers), aged approximately 24 mo, were used to isolate BSC for 3 separate assays. Myogenic differentiation was induced using 3% horse serum upon cultured BSC with increasing doses (0, 1, 10, 100, and 1,000 nM) of ATRA. After 96 h of incubation, cells were harvested and used to measure the gene expression of protein kinase B (Akt), AMP-activated protein kinase alpha (AMPK), glucose transporter 4 (GLUT4), myogenin, lipoprotein lipase (LPL), myosin heavy chain (MHC) I, MHC IIA, MHC IIX, insulin like growth factor-1 (IGF-1), Peroxisome proliferator activated receptor gamma (PPARγ), PPARδ, and Smad transcription factor 3 (SMAD3) mRNA relative to ribosomal protein subunit 9 (RPS9). The mRNA expression of LPL was increased (P < 0.05) with 100 and 1,000 nM of ATRA. Expression of GLUT4 was altered (P < 0.05) by ATRA. The treatment of ATRA (1,000 nM) also increased (P < 0.05) mRNA gene expression of SMAD3. The gene expression of both PPARδ and PPARγ were increased (P < 0.05) with 1,000 nM of ATRA. Protein level of PPARδ was also affected (P < 0.05) by 1,000 nM of ATRA and resulted in a greater (P < 0.05) protein level of PPARδ compared to CON. All-trans retinoic acid (10 nM) increased gene expression of MHC I (P < 0.05) compared to CON. Expression of MHC IIA was also influenced (P < 0.05) by ATRA. The mRNA expression of MHC IIX was decreased (P < 0.05) with 100 and 1,000 nM of ATRA. In muscle cells, ATRA may cause muscle fibers to transition towards the MHC isoform that prefers oxidative metabolism, as evidenced by increased expression of genes associated with the MHC I isoform. These changes in MHC isoforms appeared to be brought about by changing PPARδ gene expression and protein levels.
全反式视黄酸（ATRA）与哺乳动物脂肪组织和骨骼肌中的各种生理现象有关。我们假设 ATRA 可能通过各种转录过程影响牛卫星细胞培养中的骨骼肌纤维类型。进行了牛原代卫星细胞（BSC）培养实验，以确定 ATRA 对与骨骼肌纤维类型和代谢相关的基因和蛋白质水平的剂量效应。使用来自杂交公牛（n = 2 头公牛）的半膜肌，年龄约为 24 个月，用于分离用于 3 个单独测定的 BSC。在培养 BSC 时，使用 3％马血清诱导肌发生分化，并使用 0、1、10、100 和 1,000 nM 的 ATRA 增加剂量。孵育 96 小时后，收获细胞并用于测量蛋白激酶 B（Akt）、AMP 激活的蛋白激酶α（AMPK）、葡萄糖转运蛋白 4（GLUT4）、肌生成素、脂蛋白脂肪酶（LPL）、肌球蛋白重链（MHC）I、MHC IIA、MHC IIX、胰岛素样生长因子-1（IGF-1）、过氧化物酶体增殖物激活受体γ（PPARγ）、PPARδ 和 Smad 转录因子 3（SMAD3）相对于核糖体蛋白亚基 9（RPS9）的 mRNA 表达。LPL 的 mRNA 表达增加（P <0.05），ATRA 为 100 和 1,000 nM。GLUT4 的表达受 ATRA 影响（P <0.05）。ATRA（1,000 nM）处理还增加了 SMAD3 的 mRNA 基因表达（P <0.05）。PPARδ 和 PPARγ 的基因表达均增加（P <0.05），ATRA 为 1,000 nM。1,000 nM 的 ATRA 还影响了 PPARδ 的蛋白水平，导致 PPARδ 的蛋白水平高于 CON（P <0.05）。全反式视黄酸（10 nM）与 CON 相比，增加了 MHC I 的基因表达（P <0.05）。MHC IIA 的表达也受 ATRA 影响（P <0.05）。MHC IIX 的 mRNA 表达减少（P <0.05），ATRA 为 100 和 1,000 nM。在肌肉细胞中，ATRA 可能导致肌肉纤维向更偏爱氧化代谢的 MHC 同工型转变，这可以通过与 MHC I 同工型相关的基因表达增加来证明。MHC 同工型的这些变化似乎是通过改变 PPARδ 基因表达和蛋白水平引起的。
