Is <i>Fusobacterium nucleatum</i> the key mediator between oral infections and systemic diseases? Mechanistic insights and therapeutic implications

Fusobacterium nucleatum has emerged as a pathobiont that associates oral dysbiosis with systemic diseases through coaggregation, hematogenous dissemination, and immune modulation. This review provides molecular insights through which they are involved in systemic diseases such as colorectal cancer, adverse pregnancy outcomes, cardiovascular diseases, neurodegenerative disorders, and diabetes mellitus. Key virulence factors include the adhesins of FadA, Fap2, and RadD, lipopolysaccharides, and outer membrane vesicles, which mediate epithelial invasion and endothelial permeafbility and facilitate immune suppression through TLR4-NF-κB, β-catenin/Wnt, and MAPK signaling pathways. These interactions result in impaired tissue homeostasis, propagate chronic inflammation, and promote oncogenic and metabolic modulation. Systemic pleiotropy of F. nucleatum is further substantiated by its involvement in chemoresistance, placental dysfunction, vascular inflammation, and neuronal injury, substantiating its systemic pleiotropy. Emerging therapeutic strategies, such as blocking adhesins, neutralizing outer membrane vesicles, microbiome manipulation, and using CRISPR-based clearance, provide precision techniques for mitigating diseases. Therefore, this review identifies F. nucleatum as the primary microbial mediator of oral-systemic pathology and its translational significance in the development of targeted antimicrobial and host-directed therapies.