FNDC5 and acute respiratory distress syndrome: Irisin improves endothelial barrier function and lung permeability as well as attenuates lung edema and inflammation in ALI, possibly through the AMPK/SIRT1 signaling pathway and inhibition of p-Src/myosin light-chain kinase/β-linker protein, activation of AMPK-Ras-related C3 botulinum toxin substrate 1/cell division control protein 42 homolog, and protection of mitochondrial function (Chen et al., 2017; Li et al., 2019; Bi et al., 2020).