The gut microbiota, bacterial metabolites and colorectal cancer

Dietary intake has an important effect on the gut environment, much of which is mediated by the metabolic activities of the intestinal microbiota on dietary compounds. Different microbial metabolites have the potential to promote and protect against colorectal cancer (CRC).Accumulating evidence suggests that microbial-derived short chain fatty acids control inflammation and regulatory T cell populations. This involves the inhibition of host histone deacetylases and interactions with cell surface receptors.Multiple species in the gut microbiota have complex roles in releasing and converting diet-derived phytochemicals and host-derived bile acids and glycoconjugates, all of which influence the overall microbial metabolome.Alterations in the composition of the gut microbiota can be detected both in faecal samples and in tumour-associated communities that are associated with CRC. Although many of these changes may be consequential, some specific pathogens seem to contribute to causation and disease progression.It is unlikely that the aetiology of CRC can be ascribed to the presence and activities of single pathogenic species, and it is proposed that the cumulative effects of microbial metabolites should be considered to better predict and prevent cancer progression.