To explore these mechanisms, Zhang et al. [15] conducted experiments in COPD mice using myostatin inhibitors TEW-7197 (a selective transforming growth factor-β receptor LK4/ALK5 inhibitor) and SIS3 (which inhibits Smad3 phosphorylation) to restore PGC-1α and Fndc5 levels in skeletal muscles. The gene discussed is FNDC5; the disease is chronic obstructive pulmonary disease.