Suer Miranda K, Crane Justin D, Trappe Todd A, Jemiolo Bozena, Trappe Scott W, Harber Matthew P
Ball State University, Muncie, IN 47306, USA.
Aviat Space Environ Med. 2013 Jul;84(7):669-74. doi: 10.3357/asem.3379.2013.
Exercise and nutritional interventions have been examined independently as countermeasures to offset the loss of skeletal muscle mass with unloading, yet a protocol to completely preserve the soleus has not been identified. Little is known regarding the combined effect of exercise and nutrition on factors regulating skeletal muscle growth. The purpose of this investigation was to evaluate the influence of amino acid (AA) infusion on myogenic (MRF-4, MyoD, and Myogenin), proteolytic (MuRF-1, Atrogin-1, FOXO3A, Calpain-1, Calpain-2, Caspase-3, Cathepsin L1), and cytokine (IL-6, IL-8, and IL-15) mRNA transcripts in two skeletal muscles that respond distinctly to microgravity unloading.
Muscle biopsies were obtained from the vastus lateralis (VL) and soleus of eight male subjects prior to and after 4 h of AA infusion for analysis of mRNA expression. All subjects performed a standardized exercise bout (45-min treadmill run) 24 h prior to the AA infusion.
In the VL, proteolytic factors MuRF-1 and FOXO3A were reduced (44 +/- 9 and 28 +/- 6%, respectively) in response toAA infusion. In the soleus, mRNA transcripts of myogenic factor MRF-4 (91 +/- 36%) and cytokines IL-6, IL-8, and IL-15 were elevated while the proteolytic marker FOXO3A mRNA was reduced by 19 +/- 9%.
These data suggest that the expression of genes related to skeletal muscle remodeling is altered during acute AA infusion 24 h post-exercise. It appears that increased amino acid availability in concert with exercise may create an intramuscular environment favorable for the prevention of muscle atrophy associated with unloading, which may be particularly beneficial for the soleus.
运动和营养干预已分别作为抵消失重导致的骨骼肌质量损失的对策进行了研究，但尚未确定完全保留比目鱼肌的方案。关于运动和营养对调节骨骼肌生长的因素的联合作用知之甚少。本研究的目的是评估氨基酸（AA）输注对两块对微重力卸载反应不同的骨骼肌中肌源性（MRF-4、MyoD和肌细胞生成素）、蛋白水解（MuRF-1、Atrogin-1、FOXO3A、钙蛋白酶-1、钙蛋白酶-2、半胱天冬酶-3、组织蛋白酶L1）和细胞因子（IL-6、IL-8和IL-15）mRNA转录本的影响。
在8名男性受试者输注AA 4小时前后，从股外侧肌（VL）和比目鱼肌获取肌肉活检样本，用于分析mRNA表达。所有受试者在输注AA前24小时进行了标准化运动（45分钟跑步机跑步）。
在VL中，输注AA后蛋白水解因子MuRF-1和FOXO3A减少（分别减少44±9%和28±6%）。在比目鱼肌中，肌源性因子MRF-4的mRNA转录本（91±36%）以及细胞因子IL-6、IL-8和IL-15升高，而蛋白水解标志物FOXO3A的mRNA减少19±9%。
这些数据表明，运动后24小时急性输注AA期间，与骨骼肌重塑相关的基因表达发生了改变。似乎氨基酸可用性增加与运动协同作用可能会创造一个有利于预防与卸载相关的肌肉萎缩的肌肉内环境，这对比目鱼肌可能特别有益。
