THE GUT-MICROBIOTA-BRAIN AXIS IN NEURODEGENERATIVE DISORDERS: MOLECULAR MECHANISMS, IMMUNE INTERACTIONS, AND THERAPEUTIC OPPORTUNITIES

Neurodegenerative diseases (NDDs), such as Alzheimer’s disease, Parkinson’s disease, Huntingtons disease, and Amyotrophic Lateral Sclerosis (ALS) are an increasing global health concern with progressive neuronal loss and inadequate curable treatments.In recent years scientists have discovered a pathway connecting neurodegeneration and the gut microbiota–brain axis (GMBA).This review examines how gut microbiota dysbiosis-characterized by low microbial diversity due to depletion of beneficial bacteria and overgrowth of pathogenic species-favours disease progression. Dysbiosis has been associated with intestinal barrier integrity disruption, consequent permeability and systemic translocation of microbial products, including lipopolysaccharides (LPS) triggering pro inflammatory cytokine release, and neuro inflammation.These inflammatory processes are linked to an impaired blood-brain barrier, activated microglia, and neuronal injury. Moreover, a reduction in the production of short-chain fatty acids (SCFAs), particularly butyrate, impairs immune regulation, and neuroprotection, while disrupted microbial metabolism affects neurotransmitter synthesis and signaling. There are several modulatory factors that influence gut microbial taxonomy like diet, aging, medication use, and lifestyle. The review further explores therapeutic techniques and their possibilities which include dietary interventions, probiotics, prebiotics, fecal microbiota transplantation, and some new psychobiotics approaches.