The Gut Nexus: Unraveling Microbiota-Mediated Links Between Type 2 Diabetes and Colorectal Cancer

Background/Objectives: Colorectal cancer (CRC) and type 2 diabetes mellitus (T2DM) are two of the most rapidly rising chronic diseases globally. Despite appearing distinct, an emerging body of literature identifies shared etiopathogenic mechanisms mediated by gut microbiota. This review synthesizes 38 peer-reviewed studies to evaluate the compositional, metabolic, immune, and translational intersections of gut dysbiosis in the pathogenesis of T2DM-associated CRC. Methods: This narrative literature review examined 38 primary research articles (human and animal studies) retrieved from PubMed, Scopus, and Embase. Studies were selected based on relevance to the microbiota-mediated mechanisms linking T2DM and CRC, with a focus on compositional analysis, metabolomic shifts, immune activation, and therapeutic interventions. Results: The findings highlight a mechanistically rich overlap between T2DM and CRC through shared dysbiosis, characterized by depletion of SCFA-producing taxa (e.g., Faecalibacterium, Roseburia, Butyricicoccus), enrichment of pathobionts (e.g., Fusobacterium nucleatum, Peptostreptococcus), and the disruption of mucosal immunity and epithelial integrity. Metabolic shifts include reduced butyrate and increased toxic bile acids (e.g., deoxycholic acid), TMAO, and oxidative metabolites, while immune dysregulation features elevated LPS, IL-1β, CXCL3, and NF-κB signaling. Therapeutically, microbiota modulation via diet, metformin, and probiotics shows promise. Conclusions: Gut microbiota lies at the nexus of T2DM and CRC, functioning as a modifiable mediator rather than a passive bystander. Future research should prioritize longitudinal, multi-omic, and intervention-driven studies to enable personalized prevention and treatment strategies.