Gut Microbiota Dysbiosis in Alzheimer's Disease and Possible Therapeutic Options.

Human microbiota consists of trillions of microbial cells dominated by bacteria, which live in the human body, while the term microbiome refers to the collective genetic material of microorganisms. Among them, the gut microbiota has emerged as pivotal, producing its own metabolites, neurotransmitter precursors, and immune mediators that affect brain development and function. These signals function via the complex, bidirectional Gut-Brain Axis (GBA). This is a communication network that connects the gastrointestinal tract to the central nervous system. This axis plays an important role in the regulation of gastrointestinal homeostasis, neurodevelopment, emotional regulation, and cognitive processes. Increasing evidence suggests that microbial dysbiosis within the gastrointestinal tract is involved in the pathogenesis and progression of several neurological and neurodegenerative disorders, including mood disorders, schizophrenia, autism spectrum disorder, Alzheimer's Disease (AD), Parkinson's Disease (PD), and Huntington's Disease. These insights have opened new therapeutic possibilities, and multiple microbiota-targeted interventions, such as dietary modification, prebiotics, probiotics, postbiotics, psychobiotics, antibiotics, and Fecal Microbiota Transplantation (FMT), are now being explored for their therapeutic value, especially in Alzheimer's disease.