Abstract
Methionine, an essential amino acid, is abundant in animal protein. High dietary methionine intake is associated with the promotion of colorectal cancer (CRC); however, the mechanisms remain unclear. This study aimed to investigate the underlying mechanisms of high dietary methionine promoting CRC and evaluate the effect of high dietary methionine on healthy intestine. Our results demonstrated that high dietary methionine intake exhibited a higher incidence and invasion of tumors in AOM/DSS-induced mice. Meanwhile, the gut microbiota were disturbed, consequently fostering the metabolism of secondary bile acids. The contents of lithocholic acid (LCA) and deoxycholic acid (DCA) significantly increased (P < 0.01), which further activated the bile acid membrane receptors TGR5, and then the activated TGR5 promoted tumor proliferation through STAT3 and YAP pathways. Pseudo-germ-free mice validate the role of gut microbiota and secondary bile acids in promoting CRC by high dietary methionine. Notably, similar disturbances in gut microbiota and bile acid metabolism were observed in the intestine of healthy mice with high dietary methionine intake. In conclusion, dysregulation of bile acid metabolism and activation of the corresponding receptor TGR5 were mechanisms promoting CRC associated with high dietary methionine intake.
