Ketogenic Diet Alleviates Colorectal Cancer by Attenuating Macrophage <scp>M2</scp> Polarisation Triggered by Oncometabolite <scp>MMA</scp> Derived From the Gut Microbiota

Proposed mechanism of the ketogenic diet-microbiota-MMA-immune axis in CRC. (Part 1) A ketogenic diet remodels gut microbiota homeostasis by depleting MMA-producing bacteria, thereby reducing the accumulation of the oncometabolite (MMA). (Part 2) At the molecular level, MMA acts as a ligand that binds to Rap1, activating the downstream MAPK/ERK signalling cascade. This signalling event drives the transcriptional reprogramming of TAMs towards the pro-tumorigenic M2 phenotype. (Part 3) Clinically, elevated serum MMA in CRC patients correlates with increased M2 macrophage infiltration in the tumour microenvironment and poor prognosis.