Ruhr-University Bochum, Diabetes Center, Heart and Diabetes Center NRW, Bad Oeynhausen, Germany.
PLoS One. 2013 May 23;8(5):e65195. doi: 10.1371/journal.pone.0065195. Print 2013.
Methylglyoxal (MG), a highly reactive α-dicarbonyl metabolite of glucose degradation pathways, protein and fatty acid metabolism, plays an important role in the pathogenesis of diabetic complications. Hyperglycemia triggers enhanced production of MG and increased generation of advanced glycation endproducts (AGEs). In non-enzymatic reactions, MG reacts with arginine residues of proteins to form the AGEs argpyrimidine and hydroimidazolone. Glyoxalase 1 (GLO1), in combination with glyoxalase 2 and the co-factor glutathione constitute the glyoxalase system, which is responsible for the detoxification of MG. A GLO1 specific knock down results in accumulation of MG in targeted cells. The aim of this study was to investigate the effect of intracellularly accumulated MG on insulin signaling and on the translocation of the glucose transporter 4 (GLUT4). Therefore, L6 cells stably expressing a myc-tagged GLUT4 were examined. For the intracellular accumulation of MG, GLO1, the first enzyme of the glyoxalase pathway, was down regulated by siRNA knock down and cells were cultivated under hyperglycemic conditions (25 mM glucose) for 48 h. Here we show that GLO1 knock down augmented GLUT4 level on the cell surface of L6 myoblasts at least in part through reduction of GLUT4 internalization, resulting in increased glucose uptake. However, intracellular accumulation of MG had no effect on GLUT4 concentration or modification. The antioxidant and MG scavenger NAC prevented the MG-induced GLUT4 translocation. Tiron, which is also a well-known antioxidant, had no impact on MG-induced GLUT4 translocation.
甲基乙二醛（MG）是葡萄糖降解途径、蛋白质和脂肪酸代谢的一种高度反应性α-二羰基代谢物，在糖尿病并发症的发病机制中起着重要作用。高血糖会引发 MG 的产生增加和晚期糖基化终产物（AGEs）的生成增加。在非酶反应中，MG 与蛋白质的精氨酸残基反应，形成 AGEs 精氨酸嘧啶和羟咪唑啉酮。醛糖酶 1（GLO1）与醛糖酶 2 和辅助因子谷胱甘肽结合构成了醛糖酶系统，负责 MG 的解毒。GLO1 的特异性敲低会导致靶细胞中 MG 的积累。本研究旨在研究细胞内积累的 MG 对胰岛素信号转导和葡萄糖转运蛋白 4（GLUT4）易位的影响。因此，研究了稳定表达 myc 标记 GLUT4 的 L6 细胞。为了使 MG 在细胞内积累，通过 siRNA 敲低下调糖酵解途径的第一酶 GLO1，并在高糖条件（25 mM 葡萄糖）下培养细胞 48 小时。研究结果表明，GLO1 敲低至少部分通过减少 GLUT4 内化来增加 L6 成肌细胞表面的 GLUT4 水平，从而增加葡萄糖摄取。然而，MG 的细胞内积累对 GLUT4 浓度或修饰没有影响。抗氧化剂和 MG 清除剂 NAC 可防止 MG 诱导的 GLUT4 易位。Tiron 也是一种著名的抗氧化剂，对 MG 诱导的 GLUT4 易位没有影响。
