CAT and diabetes mellitus: This is perhaps best exemplified by the observations that 1) inherited catalase deficiency is associated with oxidative stress-related disorders, such as neoplasms, atherosclerosis, and diabetes (Góth and Nagy, 2013), and 2) a gain-of-function mutation (N237S) in acyl-CoA oxidase 1 (ACOX1), a peroxisomal enzyme that oxidizes very-long-chain fatty acids and produces H2O2 as a byproduct, causes oxidative damage associated with severe Schwann cell loss and myelination defects in humans (Chung et al., 2020).