Figure 9. Plasma irisin levels and expression of FNDC5 in muscle tissue of WT and mutant mice (DW, GKO, LKO, MKO and FKO). (A) Irisin content was measured by ELISA assay on plasma samples of 24-week-old WT and mutant mice model (DW, GKO, LKO, MKO and FKO). Data are shown as mean ± SEM for each group (n = 6). *P < 0.05 versus WT. (B) Cell lysate was prepared from gastrocnemius muscle of 24-week-old WT and mutant mice (DW, GKO, LKO, MKO and FKO), and protein levels of FNDC5 were measured by western blotting. Representative gel images are shown. (C) Relative protein expression was normalized to β-actin levels. Values are mean ±SEM (n = 4). *P < 0.05 versus WT.