Interaction of exercise training and clenbuterol on GLUT-4 protein in muscle of obese Zucker rats.
Interaction of exercise training and clenbuterol on GLUT-4 protein in muscle of obese Zucker rats.
复制标题
运动训练和克伦特罗对肥胖 Zucker 大鼠肌肉 GLUT-4 蛋白的相互作用。
作者：
C. Kuo;Z. Ding;J. Ivy
长期服用克仑特罗，一种β 2-肾上腺素能激动剂，减弱运动训练诱导的肥胖Zucker大鼠肌肉胰岛素抵抗的改善。本研究旨在确定克仑特罗是否也能减弱运动训练时肌肉中谷氨酸-4蛋白的增加，以及克仑特罗的作用是否与其下调β -肾上腺素能受体的能力有关。雌性肥胖Zucker大鼠随机分为4组：对照组（CON, n = 7）、瘦肉精组（CL, n = 8）、运动训练组（TR, n = 8）和瘦肉精加运动训练组（CL+TR, n = 8）。被分配到训练组的大鼠在啮齿类动物驱动的跑步机上跑步6-7周。服用盐酸克仑特罗的大鼠每天在跑步前30分钟插管0.8 mg/kg体重。TR大鼠红四头肌（RQ）和白四头肌（WQ） GLUT-4蛋白浓度显著高于CON和CL+TR大鼠。CL+TR大鼠RQ GLUT-4蛋白浓度显著高于CON大鼠，WQ大鼠无此差异。CON大鼠和CL大鼠的GLUT-4蛋白浓度无显著差异。RQ和WQ的GLUT-4 mRNA表达模式与其各自的GLUT-4蛋白相似。每天注射β -肾上腺素能受体拮抗剂心得安（30毫克/千克体重）的大鼠，经过6周的运动训练后，RQ或WQ中GLUT-4蛋白没有增加。这些结果表明：1)瘦肉精可以降低肌肉中与运动训练相关的谷氨酸-4蛋白的增加；2)这种作用可能是通过下调β -肾上腺素能受体介导的。
Chronic administration of clenbuterol, a beta 2-adrenergic agonist, attenuates the exercise training-induced improvement in muscle insulin resistance of the obese Zucker rat. The present study was conducted to determine whether clenbuterol also attenuates the increase in muscle GLUT-4 protein that occurs with exercise training and whether the action of clenbuterol is related to its ability to downregulate the beta-adrenergic receptors. Female obese Zucker rats were randomly assigned to one of the following four groups: control (CON, n = 7), clenbuterol (CL, n = 8), exercise training (TR, n = 8), and clenbuterol with exercise training (CL+TR, n = 8). Rats assigned to the training groups were run on a rodent motor-driven treadmill for 6-7 wk. Rats receiving clenbuterol were intubated with 0.8 mg/kg body weight 30 min before running each day. Red quadriceps (RQ) and white quadriceps (WQ) GLUT-4 protein concentrations of TR rats were significantly greater than those of CON and CL+TR rats. The RQ GLUT-4 protein concentration of the CL+TR rats was significantly greater than that of CON rats, but this difference did not occur in the WQ. GLUT-4 protein concentrations were not different between the CON and CL rats. The patterns of RQ and WQ GLUT-4 mRNA were similar to those of their respective GLUT-4 proteins. Rats receiving daily injections of propranolol (30 mg/kg body wt), a beta-adrenergic receptor antagonist, demonstrated no increase in GLUT-4 protein in RQ or WQ after 6 wk of exercise training. These results indicate that 1) clenbuterol can attenuate the increase in muscle GLUT-4 protein associated with exercise training and 2) this effect is likely mediated by a downregulation of the beta-adrenergic receptors.