RNA-seq and real-time quantitative PCR (RT-qPCR) analysis showed that elevated Mstn and decreased Fndc5 were observed at gene levels in the quadriceps femoris of patients with COPD from GEO (GSE 100281) (Willis-Owen et al., 2018) (Figure 3A) and in the gastrocnemius muscle from CS-exposed mice (Figures 3B,C). The gene discussed is FNDC5; the disease is chronic obstructive pulmonary disease.