Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes
Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes
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DOI：
10.1152/ajpendo.00194.2006
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发表时间：
2006-10-01
影响因子：
5.1
通讯作者：
Kanzaki, Makoto
中科院分区：
文献类型：
--
作者：
Nedachi, Taku;Kanzaki, Makoto
C2 C12肌管中胰岛素和细胞外葡萄糖对葡萄糖转运蛋白的调节。美国生理学杂志内分泌代谢291：E817 - E828，2006年。首次发布于2006年5月30日; doi：10.1152/ajpendo。00194.2006. - 已经确定，胰岛素刺激骨骼肌细胞中葡萄糖摄取是通过GLUT 4从细胞内储存位点易位至细胞表面介导的。然而，据报道，除L 6肌细胞外，已建立的骨骼肌细胞系显示出最小的胰岛素依赖性葡萄糖摄取和GLUT 4易位。使用C2 C12肌细胞表达外表面-MycGLUT 4-增强的青色荧光蛋白，我们在此显示分化的C2 C12肌管配备有基本的GLUT 4易位机制，其可以通过胰岛素刺激激活（类似于通过抗Myc抗体摄取和免疫染色测定评估的3倍增加）。然而，由于通过其他葡萄糖转运蛋白的基础葡萄糖摄取显著升高，因此难以用传统的2-脱氧葡萄糖摄取试验证明胰岛素刺激GLUT 4易位。有趣的是，C2 C12肌管中的基础葡萄糖转运活性似乎在5分钟内通过与病理生理学高水平的细胞外葡萄糖（25 mM）预孵育而被急性抑制。与此相反，这种活性增强了急性葡萄糖剥夺通过一个未知的机制，是独立的GLUT 4易位，但依赖于磷脂酰肌醇3-激酶活性。总之，这些发现表明，在分化的C2 C12肌管中促进葡萄糖转运系统的调节可以通过葡萄糖转运蛋白活性的令人惊讶的急性葡萄糖依赖性调节来实现，这显然有助于模糊由GLUT 4易位引起的葡萄糖摄取的胰岛素增强。我们在此还描述了几种监测C2 C12肌管中胰岛素依赖性葡萄糖摄取的方法，并提出该细胞系是用于分析骨骼肌中GLUT 4易位的有用模型。
Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes. Am J Physiol Endocrinol Metab 291: E817 - E828, 2006. First published May 30, 2006; doi: 10.1152/ajpendo. 00194.2006. - It is well established that insulin stimulation of glucose uptake in skeletal muscle cells is mediated through translocation of GLUT4 from intracellular storage sites to the cell surface. However, the established skeletal muscle cell lines, with the exception of L6 myocytes, reportedly show minimal insulin-dependent glucose uptake and GLUT4 translocation. Using C2C12 myocytes expressing exofacial-MycGLUT4-enhanced cyan fluorescent protein, we herein show that differentiated C2C12 myotubes are equipped with basic GLUT4 translocation machinery that can be activated by insulin stimulation (similar to 3-fold increase as assessed by anti-Myc antibody uptake and immunostaining assay). However, this insulin stimulation of GLUT4 translocation was difficult to demonstrate with a conventional 2-deoxyglucose uptake assay because of markedly elevated basal glucose uptake via other glucose transporter(s). Intriguingly, the basal glucose transport activity in C2C12 myotubes appeared to be acutely suppressed within 5 min by preincubation with a pathophysiologically high level of extracellular glucose (25 mM). In contrast, this activity was augmented by acute glucose deprivation via an unidentified mechanism that is independent of GLUT4 translocation but is dependent on phosphatidylinositol 3-kinase activity. Taken together, these findings indicate that regulation of the facilitative glucose transport system in differentiated C2C12 myotubes can be achieved through surprisingly acute glucose- dependent modulation of the activity of glucose transporter(s), which apparently contributes to obscuring the insulin augmentation of glucose uptake elicited by GLUT4 translocation. We herein also describe several methods of monitoring insulin-dependent glucose uptake in C2C12 myotubes and propose this cell line to be a useful model for analyzing GLUT4 translocation in skeletal muscle.