Unraveling the gut microbiota-brain axis: Mechanisms, pathophysiology, and therapeutic opportunities

The gut microbiota-brain axis constitutes a dynamic, bidirectional communication network that integrates neural, endocrine, immune, and metabolic pathways to regulate host physiology and behavior. Accumulating evidence indicates that disturbances within this axis have been consistently associated with metabolic, autoimmune, and neuropsychiatric disorders; however, much of the current evidence, particularly from human studies, remains largely correlative, and causal relationships are still under active investigation, highlighting its systemic relevance to health and disease. This review synthesizes current understanding of the structural and functional components of the gut microbiota-brain axis, including microbial community dynamics, neural signaling pathways, and key endocrine and immune mediators. We examine mechanistic insights into how microbial-derived metabolites influence brain function, cognition, mood regulation, stress responses, and disease pathogenesis. In addition, we discuss emerging therapeutic strategies targeting the gut microbiota-brain axis, including psychobiotics and fecal microbiota transplantation, while acknowledging dietary approaches, such as prebiotic supplementation, fiber-rich diets, and fermented food consumption, as complementary strategies that modulate microbiota composition that may indirectly support gut-brain axis function. By integrating mechanistic, clinical, and translational perspectives, this review aims to clarify current knowledge gaps and highlight future directions for leveraging the gut microbiota-brain axis in personalized approaches to neuropsychiatric disease management.