Gut microbiota promotes production of aromatic metabolites through degradation of barley leaf fiber

Barley leaf (BL) contains abundant plant fibers, which are important substrates for the metabolism and degradation by the gut microbiota. Here we show that mice fed a diet supplemented with BL exhibited altered gut bacterial composition characterized by the enrichment of fiber-degrading bacteria Lachnospiraceae and Prevotella. Gut microbiota-mediated BL degradation promoted butyrate and propionate production. Metabolomic analysis showed increased aromatic metabolites such as ferulic acid, 3-phenylpropanoic acid, 3-hydroxyphenylacetic acid and 3-hydroxyphenylpropionic acid in feces of mice fed with BL. Finally, antibiotic treatment and anaerobic fermentation confirmed the obligate role of gut microbiota in the production of aromatic metabolites during BL degradation. Together, these findings provide insights into a gut microbiota-mediated degradation process of BL fiber components, which results in the production of microbial-associated metabolites that may exert potential active effects on host physiology.