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.

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 48h 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 8weeks 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.