The effect of endurance training and downhill running on the expression of IL-1β, IL-6, and TNF-α and HSP72 in rat skeletal muscle

- Myokines are cytokines, e.g. IL-6, produced by skeletal muscle fibers.
- Endurance training increased muscle levels of IL-6 and IL-1β.
- Endurance training reduced muscle levels of TNF-ɑ.
- Endurance training attenuated increases of HSP72 in response to downhill running.
- Endurance training did not reduced increases of IL-6 in response to downhill running.

This study investigated changes in the myokines IL-1β, IL-6, and TNF-α, as well as HSP72, after endurance training and after a session of downhill running. Twenty-eight rats were allocated to four different groups: 1. Eight weeks of endurance training at 65-70% VO2max (Trained); 2. Endurance training and a single session of downhill running on a 16° slope (Trained plus downhill); 3. A single session of downhill running (Sedentary plus downhill); and 4. Sedentary (Control, no exercise). Soleus and extensor digitorum longus (EDL) muscles were harvested 48 h after training and/or a single session of downhill running and protein levels of IL-1β, IL-6, TNF-α, and HSP72 were measured and compared to the levels in the control animals. Creatine kinase (CK) was measured in plasma.Endurance training augmented intramuscular levels of HSP72 and IL-6 in both soleus and EDL muscles (p < 0.05). Endurance training elevated IL-1β and decreased TNF-α significantly only in EDL (P < 0.05). IL-6 increased in both sedentary and trained rats after downhill running (P < 0.05), while HSP72 increased only in the previously sedentary rats. CK was lower in trained than sedentary rats after downhill running.In conclusion, endurance training for 8 weeks elevated muscular HSP72 protein levels, which might have preconditioned the muscles for a single session of downhill running, as indicated by the CK and HSP72 responses. Interestingly, IL-6 was augmented by endurance training and further increased by downhill running. IL-1β, along with IL-6, was increased by endurance training, and these myokines thus appear to be differently regulated than TNF-α.