Myokines, Microbiota, and Neuroinflammation: Physical Activity Modulates the Gut–Brain Axis

BACKGROUND: Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis are increasingly recognized as disorders influenced not only by intrinsic neural pathology but also by systemic physiological networks, including the gut-brain axis. Emerging evidence highlights physical activity as a potent modulator of this bidirectional communication system, with muscle-derived signals particularly myokines, metabolites, and extracellular vesicles playing a central role. METHODS: This narrative review synthesizes current knowledge on how exercise-induced molecular mediators influence gut microbiota composition, intestinal barrier integrity, immune signaling, and neuroinflammatory pathways. Findings were integrated across the disciplines of neuroscience, microbiology, and exercise physiology to evaluate mechanistic links between muscle-secreted factors and gut-mediated responses. RESULTS: Mechanistic links exist between muscle-secreted factors such as irisin, cathepsin B, BDNF-inducing pathways, and lactate with microbial metabolites including short-chain fatty acids. These interacting pathways demonstrate a combined impact on neuroprotection, synaptic plasticity, and the modulation of disease progression in neurodegenerative conditions. CONCLUSION: Physical activity represents a promising non-pharmacological strategy for modulating the gut-brain axis in neurodegenerative conditions. Understanding the interplay between muscle-derived signals and gut-mediated pathways may open new avenues for targeted interventions aimed at slowing or preventing neurodegenerative decline.