α-Defensin 5 gene expression is regulated by gut microbial metabolites

alpha-Defensin 5 is important to both maintenance of a gut microbiota and host immunity. While previous reports have shown that gut bacteria are able to upregulate alpha-defensin 5 through Toll-like receptor signaling, we demonstrate here that alpha-defensin 5 expression can also be regulated by microbial metabolites. Among these, lactate appeared to significantly suppress alpha-defensin 5 gene transcription. Actually, fractions of <3kD compounds obtained from the ceca of SPF mice were suppressed alpha-defensin 5 gene transcription at specific concentrations. Our results also suggest that cecal content may include as yet unidentified factors that can enhance alpha-defensin 5 expression. Our data point to a novel function for the gut microbial metabolites in controlling the expression of antimicrobial peptides in the intestine.