AMPK activation is required for improvement of mitochondrial function using NR in PA-treated skeletal muscle cells. (A) Representative Western blot results for Sirt1, p-AMPKα, AMPKα and PGC-1α in C2C12 myotube cells and the quantitative results for WB. α-Tubulin served as a loading control. (B) JC-1 staining, the microscope magnification is 200×. (C) MitoSOX staining, the microscope magnification is 200×. Compound C means that the C2C12 myotube cells were treated with 10μM Compound C for 8 h before adding PA and NR. * p < 0.05 compared with the CON group; # p < 0.05 comparing PA group vs. PA + NR group. Abbreviations: Compound C—6-[4-(2-Piperidin-1-ylethoxy) phenyl]-3-pyridin-4-ylpyrazolo [1,5-a] pyrimidine.