Kuo Chia-Hua, Hwang Hyonson, Lee Man-Cheong, Castle Arthur L, Ivy John L
Department of Kinesiology and Health Education, University of Texas at Austin, Austin, Texas 78712, USA.
J Appl Physiol (1985). 2004 Feb;96(2):621-7. doi: 10.1152/japplphysiol.00830.2003. Epub 2003 Oct 10.
The purpose of this study was to investigate the role of insulin on skeletal muscle GLUT-4 protein expression and glycogen storage after postexercise carbohydrate supplementation. Male Sprague-Dawley rats were randomly assigned to one of six treatment groups: sedentary control (Con), Con with streptozocin (Stz/C), immediately postexercise (Ex0), Ex0 with Stz (Stz/Ex0), 5-h postexercise (Ex5), and Ex5 with Stz (Stz/Ex5). Rats were exercised by swimming (2 bouts of 3 h) and carbohydrate supplemented immediately after each exercise session by glucose intubation (1 ml of a 50% wt/vol). Stz was administered 72-h before exercise, which resulted in hyperglycemia and elimination of the insulin response to the carbohydrate supplement. GLUT-4 protein of Ex0 rats was 30% above Con in fast-twitch (FT) red and 21% above Con in FT white muscle. In Ex5, GLUT-4 protein was 52% above Con in FT red and 47% above Con in FT white muscle. Muscle glycogen in FT red and white muscle was also increased above Con in Ex5 rats. Neither GLUT-4 protein nor muscle glycogen was increased above Con in Stz/Ex0 or Stz/Ex5 rats. GLUT-4 mRNA in FT red muscle of Ex0 rats was 61% above Con but only 33% above Con in Ex5 rats. GLUT-4 mRNA in FT red muscle of Stz/C and Stz/Ex0 rats was similar but significantly elevated in Ex5/Stz rats. These results suggest that insulin is essential for the increase in GLUT-4 protein expression following postexercise carbohydrate supplementation.
本研究的目的是调查运动后补充碳水化合物后胰岛素对骨骼肌葡萄糖转运蛋白4（GLUT-4）蛋白表达和糖原储存的作用。雄性Sprague-Dawley大鼠被随机分为六个治疗组之一：久坐对照组（Con）、链脲佐菌素处理的对照组（Stz/C）、运动后即刻组（Ex0）、链脲佐菌素处理的运动后即刻组（Stz/Ex0）、运动后5小时组（Ex5）和链脲佐菌素处理的运动后5小时组（Stz/Ex5）。通过游泳（2次，每次3小时）使大鼠运动，并在每次运动后立即通过葡萄糖插管（1毫升50%重量/体积）补充碳水化合物。在运动前72小时给予链脲佐菌素，这导致了高血糖并消除了对碳水化合物补充的胰岛素反应。Ex0组大鼠的GLUT-4蛋白在快肌（FT）红色肌中比Con组高30%，在FT白色肌中比Con组高21%。在Ex5组中，GLUT-4蛋白在FT红色肌中比Con组高52%，在FT白色肌中比Con组高47%。Ex5组大鼠FT红色和白色肌中的肌肉糖原也比Con组增加。在Stz/Ex0或Stz/Ex5组大鼠中，GLUT-4蛋白和肌肉糖原均未比Con组增加。Ex0组大鼠FT红色肌中的GLUT-4 mRNA比Con组高61%，但在Ex5组大鼠中仅比Con组高33%。Stz/C和Stz/Ex0组大鼠FT红色肌中的GLUT-4 mRNA相似，但在Ex5/Stz组大鼠中显著升高。这些结果表明，胰岛素对于运动后补充碳水化合物后GLUT-4蛋白表达的增加至关重要。
