de Carvalho Papa Paula, Vargas Alessandra Martins, da Silva José Luciano Tavares, Nunes Maria Tereza, Machado Ubiratan F
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Professor Lineu Prestes, 1524, São Paulo (SP), 05508-900,, Brazil.
Life Sci. 2002 Sep 6;71(16):1917-28. doi: 10.1016/s0024-3205(02)01948-3.
The aim of the present study was to investigate the GLUT4 protein expression during the development of obesity in monosodium glutamate- (MSG) treated mice. Control (C) and neonatally MSG-treated 2-month-old (2-mo), 4-month-old (4-mo) and 7-month-old (7-mo) mice were analyzed. Anthropometric data, basal glycemia and insulinemia were measured; and the GLUT4 protein was assessed by Western blotting in white adipose tissue (WAT), skeletal muscle gastrocnemius (SM) and heart (H). Compared to age-matched C mice, the 2-mo and 4-mo MSG mice were already obese, but metabolically they showed increased or preserved whole-body insulin sensitivity, respectively. At these ages they showed unchanged total GLUT4 content in SM and H. However, in plasma membrane fraction from WAT, the MSG showed increased GLUT4 content at both 2- (by 60%) and 4-month (by 45%) of age. When the GLUT4 protein was expressed by unit of adipocyte surface area the protein amount was increased by 36 and 220% in 2-mo and 4-mo MSG mice, respectively. At 7 months of age, obesity was fully established in MSG mice, showing a strongly insulin resistant condition. Additionally, in the 7-mo MSG-mice the GLUT4 protein was reduced in SM (by 40%), H (by 28%), PM and M fractions of WAT (by approximately 70%), and PM expressed by unit of adipocyte surface area (by 92%). The data demonstrate that early, during the accelerated development of obesity in MSG-treated mice, the GLUT4 content was increased in WAT, and that may play a key role in the development of obesity. Later on, when obesity is fully established, the GLUT4 protein was reduced in SM, heart and WAT, and that may be involved in the insulin resistance present in this condition.
本研究的目的是调查在味精（MSG）处理的小鼠肥胖发生过程中葡萄糖转运蛋白4（GLUT4）的蛋白表达情况。对对照组（C）以及新生期经MSG处理的2月龄、4月龄和7月龄小鼠进行了分析。测量了人体测量数据、基础血糖和胰岛素水平；通过蛋白质免疫印迹法评估白色脂肪组织（WAT）、腓肠肌骨骼肌（SM）和心脏（H）中的GLUT4蛋白。与年龄匹配的C组小鼠相比，2月龄和4月龄的MSG处理小鼠已经肥胖，但在代谢方面，它们分别表现出全身胰岛素敏感性增加或保持不变。在这些年龄段，它们的SM和H中GLUT4总含量没有变化。然而，在WAT的质膜部分，MSG处理组在2月龄（增加60%）和4月龄（增加45%）时GLUT4含量增加。当以脂肪细胞表面积单位表达GLUT4蛋白时，2月龄和4月龄的MSG处理小鼠中蛋白量分别增加了36%和220%。7月龄时，MSG处理小鼠完全肥胖，表现出强烈的胰岛素抵抗状态。此外，在7月龄的MSG处理小鼠中，SM中的GLUT4蛋白减少了40%，H中减少了28%，WAT的质膜和微粒体部分减少了约70%，以脂肪细胞表面积单位表达的质膜减少了92%。数据表明，在MSG处理小鼠肥胖加速发展的早期，WAT中GLUT4含量增加，这可能在肥胖发展中起关键作用。后来，当肥胖完全形成时，SM、心脏和WAT中的GLUT4蛋白减少，这可能与这种情况下存在的胰岛素抵抗有关。
