Silva Jose L T, Giannocco Gisele, Furuya Daniela T, Lima Guilherme A, Moraes Paulo A C, Nachef Sara, Bordin Silvana, Britto Luiz R G, Nunes Maria T, Machado Ubiratan F
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil.
Mol Cell Endocrinol. 2005 Aug 30;240(1-2):82-93. doi: 10.1016/j.mce.2005.05.006.
The GLUT4 gene transcriptional activity has a profound impact on the insulin-mediated glucose disposal and it is, therefore, important to understand the mechanisms underlying it. Insulin and exercise modulate GLUT4 expression in vivo, but the net control and involved mechanisms of each one have not been established yet. This paper sought to discriminate, in soleus muscle, the effects of insulin and muscle contraction on GLUT4 gene expression, and the involvement of transcriptional factors: myocite enhancer factor 2 (MEF2 A/C/D), hypoxia inducible factor 1-a (HIF1-a) and nuclear factor-kappa B (NF-kappaB). The GLUT4 mRNA was reduced by fasting (40%), and increased by in vitro incubation with insulin (25%) or insulin plus glucose (40%), which was accompanied by opposite regulations of NF-kappaB mRNA. Differently, in vitro, muscle contraction led to a rapid increase (35-80%) in GLUT4, MEF2A, MEF2D and HIF1-a mRNAs. Additionally, electrophoretic mobility shift assay confirmed changes in the binding activity of nuclear proteins to consensus NF-kappaB, GLUT4-Ebox and GLUT4-AT-rich element probes, parallel to the mRNA changes of their respective transcriptional factors NF-kappaB, HIF1-a and MEF2s. Concluding, insulin- and contraction-induced regulation of GLUT4 expression involves distinct transcriptional factors.
GLUT4基因转录活性对胰岛素介导的葡萄糖代谢有深远影响，因此了解其潜在机制很重要。胰岛素和运动在体内调节GLUT4表达，但各自的净调控及相关机制尚未明确。本文旨在区分比目鱼肌中胰岛素和肌肉收缩对GLUT4基因表达的影响，以及转录因子：肌细胞增强因子2（MEF2 A/C/D）、缺氧诱导因子1-α（HIF1-α）和核因子-κB（NF-κB）的作用。禁食使GLUT4 mRNA减少（40%），体外与胰岛素（25%）或胰岛素加葡萄糖（40%）孵育使其增加，同时NF-κB mRNA呈现相反的调节。不同的是，体外肌肉收缩导致GLUT4、MEF2A、MEF2D和HIF1-α mRNA迅速增加（35 - 80%）。此外，电泳迁移率变动分析证实核蛋白与共有NF-κB、GLUT4-Ebox和GLUT4-富含AT元件探针的结合活性发生变化，与各自转录因子NF-κB、HIF1-α和MEF2s的mRNA变化平行。结论是，胰岛素和收缩诱导的GLUT4表达调控涉及不同的转录因子。
