The Emerging Role of the Brain–Gut Axis in Amyotrophic Lateral Sclerosis: Pathogenesis, Mechanisms, and Therapeutic Perspectives

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Although genetic and environmental factors are established contributors, recent research has highlighted the critical role of the gut–brain axis (GBA) in ALS pathogenesis. The GBA is a bidirectional communication network involving neural, immune, and endocrine pathways that connect the gut microbiota with the central nervous system. Dysbiosis in ALS disrupts this axis, leading to increased intestinal permeability, neuroinflammation, and excitotoxicity. Notably, reductions in butyrate-producing bacteria, alterations in microbial metabolites, and enhanced NLRP3 inflammasome activation have been observed in patients with ALS. These changes may precede motor symptoms, suggesting a potential causative role. Interventions targeting the microbiome, such as dietary modulation, have shown promise in delaying disease onset and reducing inflammation. However, the clinical evidence remains limited. Given that gut dysbiosis may precede neurological symptoms, microbiota-targeted therapies offer a novel and potentially modifiable approach to ALS treatment. Understanding the role of GBA in ALS will open new avenues for early diagnosis and intervention. Further clinical trials are required to clarify the causal links and evaluate the efficacy of microbiome-based interventions. Understanding the brain–gut–microbiota axis in ALS could lead to new diagnostic biomarkers and therapeutic strategies.