Unravelling the Critical Interplay of Oral and Gut Microbiota in Disease Development

The oral microbiota, comprising bacteria, fungi, and viruses, plays a critical role in initiating food digestion, serving as the first defense against pathogenic invasion and maintaining oral homeostasis. In contrast, the gut microbiota, consisting of trillions of microorganisms, functions as a barrier protection, modulating the immune system and facilitating the absorption of nutrients. Although they have distinct anatomical locations, these ecosystems are highly interconnected and play a pivotal role in human health and disease. The most common routes of interaction between the oral and gut microbiota are the enteral, the hematogenous, and the immune cell migration routes. Many oral pathogens interact with intestinal microbes, activating the host's mechanisms that establish dysbiosis and pave the way for the development of various diseases, ranging from inflammatory bowel disease and colorectal cancer to metabolic and neurodegenerative disorders. In this review, we delineate the mechanisms underlying these ecosystems to offer novel insights into disease pathogenesis while also unveiling new avenues for preventive and therapeutic interventions. Although current therapeutic approaches include the administration of antibiotics, prebiotics, and probiotics, novel personalized therapeutic approaches have also emerged. Fecal microbiota transplantation (FMT), gut bacteria engineering, nanomedicine-based techniques, and the use of miRNA to foster microbiota balance in both compartments hold great promise and may prove critical for the prevention and management of systemic diseases.