Microbial liberation of N-methylserotonin from orange fiber in gnotobiotic mice and humans

Plant fibers in byproduct streams produced by non-harsh food processing methods represent biorepositories of diverse naturally occurring physiologically active biomolecules. To demonstrate one approach for their characterization, mass-spectrometry of intestinal contents from gnotobiotic mice, plus in vitro studies, revealed liberation of N-methylserotonin from orange fibers by human gut microbiota members including Bacteroides ovatus. Functional genomic analyses of B. ovatus strains grown under permissive and non-permissive N-methylserotonin 'mining' conditions revealed members of polysaccharide utilization loci that target pectins whose expression correlate with strain-specific liberation of this compound. N-methylserotonin, orally administered to germfree mice, reduced adiposity, altered liver glycogenesis, shortened gut transit time, and changed expression of genes that regulate circadian rhythm in liver and colon. In human studies, dose-dependent, orange fiber-specific fecal accumulation of N-methylserotonin positively correlated with levels of microbiome genes encoding enzymes that digest pectic glycans. Identifying this type of microbial mining activity has potential therapeutic implications.