Furthermore, the secretion of FGF21 from human skeletal muscle is strongly induced upon exercise or in pathophysiological conditions including in mitochondrial myopathies and aging, suggesting the involvement of muscle-derived FGF21 in both healthy and pathological conditions (Hanks et al., 2015; Tanimura et al., 2016; Villarroya et al., 2018; Tezze et al., 2019). Here, FGF21 is linked to Mitochondrial myopathy.