FOXO3 and sarcopenia: Age-related dysbiosis—which, in sarcopenia, is characterized by the loss of short-chain fatty acid (SCFA)-producing species, expansion of Proteobacteria, and increased intestinal permeability—allows translocation of lipopolysaccharide into circulation, fueling chronic low-grade inflammation, oxidative stress, and activation of catabolic adenosine monophosphate protein-kinase (AMPK)–FoxO3–Atrogin-1/MuRF1 pathways.