Department of Biological Sciences, Dana and David Dornsife College of Arts, Letters and Sciences, University of Southern California, Los Angeles, CA 90089-652, USA.
Exp Physiol. 2013 Feb;98(2):514-25. doi: 10.1113/expphysiol.2012.068833. Epub 2012 Aug 23.
The role of the nuclear co-repressor receptor-interacting protein 140 (RIP140) in metabolic regulation, gene and protein expression and insulin signalling in skeletal muscle cells remains to be delineated. To study this question, L6 myotubes were treated with or without an RNA interference oligonucleotide sequence to downregulate RIP140 expression and incubated with or without insulin (1 μM). Downregulation of RIP140 increased (P < 0.05) basal palmitate uptake (by 20%) and decreased (P < 0.05) basal palmitate oxidation (by 38%). In control small interfering RNA-treated cells, insulin increased (P < 0.05) glucose (by 31%) and palmitate uptake (by 20%) and decreased (P < 0.05) palmitate oxidation (by 35%). However, in RIP140 small interfering RNA-treated cells, insulin did not affect (P > 0.05) palmitate uptake and increased (P < 0.05) palmitate oxidation (by 79%). In insulin-mediated conditions, downregulation of RIP140 decreased (P < 0.05) Akt(Ser473) and atypical protein kinase C-ζ(Thr403/410) phosphorylation. As expected, downregulation of RIP140 was accompanied by an increase (P < 0.05) in cytochrome c oxidase subunit 4 isoform 1 and peroxisome proliferator-activated receptor receptor γ coactivator-1α mRNA content. Downregulation of RIP140 increased (P < 0.05) fatty acid transport protein 1 mRNA content and carnitine palmitoyltransferase 1b protein content and decreased (P < 0.05) medium chain acyl-CoA dehydrogenase mRNA content in basal conditions. In insulin-mediated conditions, downregulation of RIP140 increased (P < 0.05) carnitine palmitoyltransferase 1b, fatty acid transport protein 1 and fibroblast growth factor 21 mRNA content and decreased (P < 0.05) medium chain acyl-CoA dehydrogenase mRNA content and plasma membrane fatty acid translocase/cluster of differentiation 36 protein content. Our data show that, in skeletal muscle cells, RIP140 expression significantly impacts palmitate uptake and oxidation and that alterations in gene expression and Akt-atypical protein kinaseC-ζ signalling can partly explain these changes.
核共受体抑制蛋白 140（RIP140）在代谢调节、基因和蛋白质表达以及胰岛素信号转导中的作用在骨骼肌细胞中仍有待阐明。为了研究这个问题，用 RNA 干扰寡核苷酸序列下调 RIP140 表达的 L6 肌管在有或没有胰岛素（1 μM）的情况下孵育。下调 RIP140 增加了（P<0.05）基础棕榈酸摄取（增加 20%）并降低了（P<0.05）基础棕榈酸氧化（减少 38%）。在对照小干扰 RNA 处理的细胞中，胰岛素增加（P<0.05）葡萄糖（增加 31%）和棕榈酸摄取（增加 20%）并降低（P<0.05）棕榈酸氧化（减少 35%）。然而，在 RIP140 小干扰 RNA 处理的细胞中，胰岛素不影响（P>0.05）棕榈酸摄取并增加（P<0.05）棕榈酸氧化（增加 79%）。在胰岛素介导的条件下，下调 RIP140 降低了（P<0.05）Akt（Ser473）和非典型蛋白激酶 C-ζ（Thr403/410）磷酸化。如预期的那样，下调 RIP140 伴随着细胞色素 c 氧化酶亚基 4 同工型 1 和过氧化物酶体增殖物激活受体γ共激活剂-1α mRNA 含量的增加（P<0.05）。下调 RIP140 增加了（P<0.05）脂肪酸转运蛋白 1 和肉毒碱棕榈酰转移酶 1b mRNA 含量和肉毒碱棕榈酰转移酶 1b 蛋白含量，并降低了（P<0.05）基础条件下的中链酰基辅酶 A 脱氢酶 mRNA 含量。在胰岛素介导的条件下，下调 RIP140 增加了（P<0.05）肉毒碱棕榈酰转移酶 1b、脂肪酸转运蛋白 1 和成纤维细胞生长因子 21 mRNA 含量，并降低了（P<0.05）中链酰基辅酶 A 脱氢酶 mRNA 含量和质膜脂肪酸转运蛋白/分化簇 36 蛋白含量。我们的数据表明，在骨骼肌细胞中，RIP140 表达显著影响棕榈酸摄取和氧化，并且基因表达和 Akt-非典型蛋白激酶 C-ζ 信号的改变可以部分解释这些变化。
