CTSB and cancer: We identified Cathepsin B (Ctsb), a lysosomal cysteine protease, that has been primarily studied in pathological contexts—where it is linked to cancer progression, exacerbation of brain injury, and equivocally to AD (Mueller‐Steiner et al. 2006; Ni et al. 2022)—as a novel myokine (Moon et al. 2016).