Probiotic Rice Bran Inhibits Colorectal Cancer in AOM-DSS-Induced Mice via Enhanced Bioavailability of Anticancer Metabolites

Objectives: Recent studies are showing that incidents of colorectal cancer (CRC) among younger individuals are on the rise maybe due to poor dietary habits. A higher intake of fiber from whole grains (e.g. brown rice) has demonstrated efficacy in reducing neoplastic lesions and polyps. Rice bran (RB) is a consumable by-product of rice production that is a nutrient-rich source of prebiotics and phytochemicals that modulate gut microbiome metabolism. Methods: This study explored these effects by supplementing the diet of cancer-free and cancer-induced mice (azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colitis-associated colon carcinogenesis) for 14 weeks with RB, one-step fermentation with yeast (FRB1), or double-step FRB2 (yeast followed by a probiotics cocktail). While we observed a significant reduction in colonic neoplastic lesions, the use of non-targeted liquid chromatography coupled with mass spectrometry (LC-MS) indicated the bioavailability of the RB, FRB1, and FRB2's metabolites in the colon and small intestine. Results: RB metabolites (e.g., Benzoides, ferulates, and vitamins) were also found to be more absorbed in the small intestine and colon of both the cancer-free and cancer-induced mice. Vitamin B6 metabolites (known for their protective effect against CRC) were shown to be absorbed in the colons of cancer-induced animals with FRB 1 and 2 diets. Supplementation with either fermented RB resulted in a higher ratio absorption of some benzoides, catechol-sulfates, in the small intestine as well. The cancer-induced animals with FRB1 and 2 exhibited other benzoids (hydrocinnamates) to be highly absorbed in their colon compared to their small intestine. Ferulate and dihydroferulates, a phytochemical known for their anticancer potential, were found to be mainly absorbed in the distal section of the small intestine and colon, while ferulic sulfate and feruglycine were more bioavailable in the proximal section of the small intestine. Conclusions: These findings suggest the potential role of fermented RB as a novel food ingredient for CRC control and prevention in human. Funding Sources: NIH.