Intestinal <i>Lactobacillus murinus</i> -derived small RNAs target porcine polyamine metabolism

Gut microbiota plays a vital role in host metabolism; however, the influence of gut microbes on polyamine metabolism is unknown. Here, we found germ-free models possess elevated polyamine levels in the colon. Mechanistically, intestinal <i>Lactobacillus murinus</i>-derived small RNAs in extracellular vesicles down-regulate host polyamine metabolism by targeting the expression of enzymes in polyamine metabolism. In addition, <i>Lactobacillus murinus</i> delays recovery of dextran sodium sulfate-induced colitis by reducing polyamine levels in mice. Notably, a decline in the abundance of small RNAs was observed in the colon of mice with colorectal cancer (CRC) and human CRC specimens, accompanied by elevated polyamine levels. Collectively, our study identifies a specific underlying mechanism used by intestinal microbiota to modulate host polyamine metabolism, which provides potential intervention for the treatment of polyamine-associated diseases.