Department of Molecular Medicine, University of Pavia, Italy.
Int J Immunopathol Pharmacol. 2013 Jul-Sep;26(3):673-80. doi: 10.1177/039463201302600310.
Using an in vitro assay we assessed whether the acute exposure of soleus muscle of adult and aged rats to essential amino acid enriched mixture (EAAem) activates mTOR signaling pathway (mTOR and p70S6K) even after prolonged supplementation with the same mixture. A total of 20 adult (9 months of age at the end of treatment) and 20 aged (18 months of age at the end of treatment) male Wistar rats were used. Ten of each group were treated with EAAem (1.5 gr/kg/day in tap water) for 6 months. At the end of treatment the rats were grouped (n = 5 each group) as follows: adult (AD) and aged (AG) untreated controls; adult (AD_EAAem) and aged (AG_EAAem) chronically supplemented with EAAem; adult (AD+EAAem) and aged (AG+EAAem) acutely incubated with EAAem (soleus in 1 percent EAAem for 30 min); AD_EAAem+ and AG_EAAem+ acutely incubated with EAAem. Following treatment the activation level of mTOR and p70S6K was measured by Western blot. The basal level of mTOR and p70S6K activation appeared to be higher in AD compared with AG. In AG+EAAem a significant change in the level of p70S6K activation, unlike mTOR, was observed whereas no change was observed in AD+EAAem. In AD_EAAem muscles the basal level of p70S6K activation, unlike mTOR, was significantly lower than in AD and the acute exposure to EAAem produced a significant reduction of mTOR activation. Contrarily to AG, in AG_EAAem+ the acute exposure to EAAem produced a significant activation of mTOR, unlike p70S6K. Results in the adults indicated a higher basal level of activation and a lower responsiveness of the pathway to acute and chronic exposure to EAA-enriched mixture. On the contrary, in the aged, a lower basal level of activation was associated with a higher responsiveness to EAAem. In particular, although with a different timing, acute exposure to EAAem activated mTOR signaling even following prolonged supplementation.
使用体外分析方法，我们评估了成年和老年大鼠比目鱼肌在急性接触富含必需氨基酸混合物（EAAem）后，即使长期补充相同混合物，mTOR 信号通路（mTOR 和 p70S6K）是否会被激活。总共使用了 20 只成年（治疗结束时 9 个月大）和 20 只老年（治疗结束时 18 个月大）雄性 Wistar 大鼠。每组 10 只大鼠用 EAAem（1.5 gr/kg/天，溶于自来水中）处理 6 个月。治疗结束时，将大鼠分为以下几组（每组 5 只）：成年（AD）和老年（AG）未处理对照组；成年（AD_EAAem）和老年（AG_EAAem）慢性补充 EAAem；成年（AD+EAAem）和老年（AG+EAAem）急性孵育 EAAem（1% EAAem 孵育 30 分钟）；AD_EAAem+和 AG_EAAem+急性孵育 EAAem。治疗后，通过 Western blot 测定 mTOR 和 p70S6K 的激活水平。与 AG 相比，AD 中 mTOR 和 p70S6K 激活的基础水平似乎更高。在 AG+EAAem 中，p70S6K 的激活水平发生了显著变化，而 mTOR 则没有发生变化，而在 AD+EAAem 中则没有观察到变化。在 AD_EAAem 肌肉中，p70S6K 激活的基础水平与 mTOR 不同，明显低于 AD，急性暴露于 EAAem 会导致 mTOR 激活显著降低。与 AG 不同，AG_EAAem+ 中，急性暴露于 EAAem 会显著激活 mTOR，而不会激活 p70S6K。成年人的结果表明，mTOR 信号通路对急性和慢性接触富含必需氨基酸混合物的基础激活水平较高，反应性较低。相反，在老年人中，较低的基础激活水平与对 EAAem 的更高反应性相关。特别是，尽管有不同的时间安排，急性接触 EAAem 甚至在长期补充后也能激活 mTOR 信号。
