Fig. 3. Dietary fiber, microbiota, butyrate, and tumorigenesis.
Metabolism of fiber by colonic microbes results in generation of butyric acid. When genetic mutations in Msh2 and Apc are present, butyrate increases cell proliferation and enhances tumorigenesis. Data from another model of colorectal carcinogenesis indicate the opposite outcome: Neoplastic colonocytes engage in glycolysis for cellular energy, unlike healthy colonocytes (which favor fatty acid oxidation). As a result, butyrate accumulates in the nucleus of neoplastic cells, engaging tumor-suppressive pathways and apoptosis.