Fasting-mimicking diet counteracts gut microbial dysbiosis in experimental Lynch syndrome

The development of colorectal cancer (CRC) is largely influenced by hereditary factors, with up to one-third of cases linked to genetic predisposition. In parallel, environmental factors such as diet and intestinal microbiota play a significant role. Lynch syndrome (LS), the most common form of hereditary CRC, is due to mutations in DNA mismatch repair genes. Diet interventions such as calorie restriction (CR) can modify the course of the disease, altering nutrient supply and promoting beneficial microbial populations. Fasting-mimicking diets (FMD) are plant-based CR regimens that showed promise in modulating the gut microbiota and suppressing CRC progression in pre-clinical ectopic cancer models. In this study, Villin-Cre/Msh2-floxed (VCM) mice, modelling LS, were subjected to periodic FMD cycles for 10 months. Although not impacting on macroscopic tumor development, FMD influenced animal weight in a sexually dimorphic manner. Moreover, shotgun metagenomic sequencing revealed that FMD mitigated the dysbiotic longitudinal changes associated with cancer onset, preserving beneficial species, such as Lactobacillus johnsonii, and reducing adverse species, such as Escherichia coli. Metabolic pathway analysis also showed significant differences, with FMD preventing the upregulation of pathways involved in amino acid and nucleotide synthesis, potentially promoting tumor growth. Overall, the findings suggest that periodic FMD may be adopted as an adjuvant therapy in LS management, counteracting gut microbiota alterations.