Black rice diet alleviates colorectal cancer development through modulating tryptophan metabolism and activating AHR pathway

Consumption of dietary fiber and anthocyanin has been linked to a lower incidence of colorectal cancer (CRC). This study scrutinizes the potential antitumorigenic attributes of a black rice diet (BRD), abundantly rich in dietary fiber and anthocyanin. Our results demonstrate notable antitumorigenic effects in mice on BRD, indicated by a reduction in both the size and number of intestinal tumors and a consequent extension in life span, compared to control diet-fed counterparts. Furthermore, fecal transplants from BRD-fed mice to germ-free mice led to a decrease in colonic cell proliferation, coupled with maintained integrity of the intestinal barrier. The BRD was associated with significant shifts in gut microbiota composition, specifically an augmentation in probiotic strains Bacteroides uniformis and Lactobacillus. Noteworthy changes in gut metabolites were also documented, including the upregulation of indole-3-lactic acid and indole. These metabolites have been identified to stimulate the intestinal aryl hydrocarbon receptor pathway, inhibiting CRC cell proliferation and colorectal tumorigenesis. In summary, these findings propose that a BRD may modulate the progression of intestinal tumors by fostering protective gut microbiota and metabolite profiles. The study accentuates the potential health advantages of whole-grain foods, emphasizing the potential utility of black rice in promoting health. Black rice diet can regulate gut microbial homeostasis in the colorectal cancer (CRC) mice model, enhance the abundance of beneficial bacteria, create aromatic hydrocarbon receptor ligand metabolites, activate the intestinal aryl hydrocarbon receptor (AHR) pathway, and suppress the development of CRC.Highlightsimage The black rice diet (BRD) can slow down the development of colorectal tumors in ApcMin/+ and azoxymethane/dextran sulfate sodium (AOM/DSS) colorectal cancer (CRC) model mice.The BRD increases the abundance of intestinal probiotics, such as Bacteroides uniformis and Lactobacillus, while reducing potential intestinal pathogens.The upregulated metabolites indole and indole-3-lactic acid in BRD are ligands of the aryl hydrocarbon receptor (AHR) pathway, which slow down the development of CRC by activating intestinal AHR receptor gene expression.A moderate consumption of BRD is expected to become a potential strategy for the prevention and treatment of CRC by improving gut microbiota and metabolites.