Time Course Changes of the Expression of IGF-I, Phosphorylated Akt and Phosphorylated mTOR in Myofibers of the Early Stage of Functionally Overloaded Skeletal Muscle

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概要

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• The time course of changes of the expression of insulin-like growth factor-I (IGF-I) and activated IGF-I-related signaling molecules during the early stage of functional overload hypertrophying adult skeletal muscles are not fully understood. We have examined the time course of changes of the expression patterns of IGF-I, phosphorylated Akt (P-Akt), and phosphorylated mammalian target of rapamycin (mTOR) (P-mTOR) proteins in during the early stage of functionally overloaded plantaris muscles using immunohistochemical techniques. The time course of changes in immunohistochemical staining intensities for IGF-I was measured over 14 days. The content of IGF-I rapidly increased and reached a peak at day 5 post-surgery (p<0.05). However, the IGF-I content rapidly decreased and returned to control values by day 7 post-surgery. Activation of Akt in myofibers of overloaded muscles peaked at day 5 post-surgery (p<0.05) and was subsequently maintained throughout the experiment period (p<0.05). Likewise, activation of mTOR in myofibers of overloaded muscles gradually increased and peaked at day 5 after overload (p<0.05). Significantly elevated activation of mTOR was subsequently maintained throughout the experiment (p<0.05).Therefore, in the present study it was demonstrated that the content of IGF-I protein and activation of Akt and mTOR gradually increased and coincidentally peaked at day 5 post-surgery. Furthermore, we showed that the activation of both Akt and mTOR, but not the expression of IGF-I protein content, were significantly increased throughout the experimental period. Our findings suggest that promotion of protein synthesis via Akt/mTOR signaling pathways activated by ligand(s) as well as IGF-I may play an important role in the early stages of skeletal muscle hypertrophy.

• 日本運動生理学会の論文

著者

• Kasuga Norikatsu

  Department Of Public Health-health Information Dynamics Field Of Social Life Science Nagoya Universi

• Kasuga Norikatsu

  Departments Of Physical Education Aichi University Of Education

• Kasuga Norikatsu

  Department Of Health Science Aichi University Of Education

• Masuhara Mitsuhiko

  Graduate School Of Sport And Exercise Science Osaka University Of Health And Sport Sciences

• ISHIDO Minenori

  Graduate School of Sport and Exercise Science, Osaka University of Health and Sport Sciences

• Ishido Minenori

  Graduate School Of Sport And Exercise Science Osaka University Of Health And Sport Sciences

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