Skeletal Muscle Response to Endurance Training in IL-6-/- Mice

We examined effects of moderate-intensity endurance training on muscle COX/CS activities and V'O-2max in control WT and IL-6(-/-) mice. Animals were exercised for 10 weeks on treadmill for 1 h, 5 days a week at velocity of 6 m.min(-1) which was increased by 0.5 m.min(-1) every 2 weeks up to 8 m.min(-1). Training triggered an increase of enzyme activities in soleus muscle of WT mice (COX: 480.3+/-8.9U.g(-1) in sedentary group vs. 773.3+/-62.6U.g(-1) in trained group, P<0.05 and CS: 374.0+/-6.0U.g(-1) in sedentary group vs. 534.2+/-20.5U.g(-1) in trained group, P<0.01, respectively) whereas no changes were observed in soleus of IL6(-/-) mice. Moreover, in mixed gastrocnemius muscle of trained IL-6(-/-) mice enzyme activities tended to be lower (COX: 410.7+/-48.4U.g(-1) for sedentary vs. 277.0+/-36.5U.g(-1) for trained group and CS: 343.8+/-24.6U.g(-1) for sedentary vs. 251.7+/-27.1U.g(-1) for trained group). No changes in V'O-2max were observed in WT and IL-6(-/-) mice after training. Concluding, moderate-velocity endurance training-induced increase in COX and CS activities in muscles of WT mice only which suggests that IL-6 regulates training-induced skeletal muscle responses to exercise.