Background: Irisin, Bdnf and IL-6 Are Exercise-induced Myokines Which Exert Their Effects in Driving Brown-Fat-Like Development (Irisin) and Regulating Fat Oxidation. However, Their
Dynamic Expression in Response to Exercise Is Not Fully Known. Here We Examined the Level of Irisin, Bdnf and IL-6 As Well As the Activation of AMPK and Akt at Different Time Points following
Exercise, in Order to Explore the Pattern of Their Expression and Biological Functions.
Methods: Sprague-Dawley Rats Were Subjected to Downhill Running at 17m/Min for 90 Minutes. Serum Creatine Kinase (CK) Activity Was Tested at Day 1, 3, 5, 7, and 14 following Exercise
to Evaluate Skeletal Muscle Injury. the Serum Level and Skeletal Expression of Bdnf, IL-6 and Irisin Were Measured by Elisa and Real-Time RT-PCR, Respectively. The Activation of AMPK and Akt Signaling
Pathway Was Confirmed by Western Blot. To Compare the Difference Between Two Groups, T-Test Was Employed using SPSS Software and p < 0.05 Was Considered Statistically Significant.
Results: An Increase of CK Activity Was Observed at Day 3 and Day 5 following Exercise, Confirming Exercise-Related Skeletal Muscle Injury. We Didn’t Find Any Increase of IL-6 in the
Rats following Exercise Compared to Sedentary Group, Although It Is Reported that IL-6 Level Is Elevated Dramatically during Exercise. The Level of Irisin and Bdnf Was Increased Both in the Serum and
in the Skeletal Muscle in Day 1 and Day 3 following Downhill Running; Then, While Irisin Level Returned to the Baseline, Serum Bdnf Level Was Continuously Elevated. Besides, AMPK Activation Was Found
at Day 1 and Day 3, but Akt Was Kept Activated Over All the Time Points.
Conclusions: Although IL-6, Irisin and Bdnf Are All Exercise-Induced Myokines, Their Expression Is Regulated Differently. Irisin and Bdnf Are Both Reported to Be Involved in the
Activation of AMPK Signaling Pathway. However, We Found That the Increase of Irisin Was in Accordance with AMPK Activation, While Bdnf Increase Is in Accordance with Akt Activation. Our Results
Suggest that Bdnf May Participate in Skeletal Muscle Regeneration via Akt-Mediated Pathway in Addition to Fat Oxidation. Therefore, Exercise-Induced Myokines Are Regulated Precisely and Sequentially,
Which in Turn Exert Different Functions at Different Time following Exercise.