Decrease of PKB/Akt Phosphorylation is Partially Mediated by SAPK/JNK Activation in Serum-free L6 Myoblasts Starved with Low Glucose

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[Purpose] Studies have been using cell cultures of muscle cells to mimic atrophy in in vivo and in vitro tests. However, changes in the activation of atrophy-related PKB/Akt is not fully understood in serum-free starved skeletal muscle cells. The purpose of the present study was to determine the change of PKB/Akt phosphorylation in L6 myoblasts under serum-free starvation conditions. [Methods] We used western blotting to examine PKB/Akt expression and phosphorylation in atrophied L6 myoblasts. [Results] The phosphorylation of PKB/Akt was significantly lower in L6 myoblasts under serum-free starvation than that of the control group. Serum-free starvation for 6, 12, 24, 36, 48, 72, 96, and 120 hours significantly decreased the phosphorylation of PKB/Akt. Furthermore, the decrease of PKB/Akt phosphorylation under serum-free starvation was partially restored by SP600125, an inhibitor of SAPK/JNK. [Conclusion] These results suggest that decrease of PKB/Akt phosphorylation due to serum-free starvation with low glucose is partially related to the activity of SAPK/JNK in L6 myoblasts.