Irisin Improves Differentiation through Preserved Mitochondrial Function in Mouse C2C12 Skeletal Muscle Cells

PURPOSE In response to muscle contraction, irisin, a myokine released by skeletal muscle and white adipose tissue (WAT), is cleaved from the transmembrane protein fibronectin type III domain‐containing protein 5 (FNDC5) and has been shown to upregulate expression of uncoupling of protein 1 (UCP 1), inducing the browning of WAT. Prior research has demonstrated the protective role of irisin against insulin resistance, ischemic injury, and inflammation. We aimed to investigate the effects of Irisin on the differentiation of skeletal muscle myocytes. METHODS Mouse C2C12 skeletal muscle cells were incubated in Dulbecco’s Modified Eagle Medium (DMEM) until cell confluency reached 60%. Once the plates reached 60% confluency, 2% Horse Serum was added to the medium to induce differentiation. The cells were incubated at 37 degrees C. and 5% CO2 for three days. Cells were then incubated in medium containing irisin at differing concentrations: 0 ng/mL, 10 ng/mL, and 20 ng/mL for an additional three days. Significance was established at p < 0.05. The number of myotubes were compared days three and six in each group. Immunofluorescent staining of actinin, myosin heavy chain, myocyte enhancing factor‐2C (MEF2C), and mitochondrial capture was performed for each group. RESULTS The average number of myotubes per field for the no‐irisin group was 8.95 (+/‐ 7.85), compared to 13.6 myotubes (+/‐ 11.02 myotubes) in the 10 ng/mL irisin group and 30.5 myotubes (+/‐ 9.92 myotubes) in the 20 ng/mL irisin group. There was no statistical significance between the no‐irisin group and the 10 ng/mL group, however the number of myotubes in the 20 ng/mL group was statistically greater than both the no‐irisin group and the 10 ng/mL irisin group at p < 0.05. CONCLUSION Treatment of C2C12 myocytes with irisin at 20 ng/mL concentration induced increased myotube differentiation. Irisin appears to play a significant role in muscle regeneration and growth.