A preclinical mouse study published in Nature Metabolism demonstrates that the myokine irisin, released during aerobic activity, directly mitigates neuronal loss across spinal cord, hippocampus, and retina in an experimental autoimmune encephalomyelitis model of multiple sclerosis. Unlike observational human data linking exercise to reduced MS fatigue, this work isolates irisin's mechanism: restoration of a neuroprotective gene program and preservation of synapses without suppressing peripheral autoimmunity. The research builds on Wrann's earlier Alzheimer's findings where irisin similarly curbed neuroinflammation, suggesting a shared pathway across protein-misfolding and demyelinating diseases. Limitations are clear—this is not an RCT but a controlled animal experiment with modest group sizes typical of EAE studies, and no conflicts were disclosed beyond institutional affiliations at Mass General Brigham and UKE. The original coverage underplays how irisin deletion fully abolishes exercise benefits, a finding that reframes exercise prescriptions as potentially irisin-dependent rather than merely adjunctive. Future translation will require pharmacokinetic data on recombinant irisin and phase I safety trials in progressive MS cohorts.