(P19-023-25) Beyond Butyrate – Xenometabolomics Reveals Hundreds of Metabolites and Fiber Type-Specific Signatures in Human Stool Cultures

Objectives: Historically, studies of gut microbe metabolism of dietary fibers have focused on short-chain fatty acids (SCFAs) as established fermentation metabolites, GPCR ligands, and colon tissue fuels. SCFAs are associated with normal gut barrier function, dampened inflammation, and maintenance of an anaerobic environment to support a healthy microbiome. However, gut microbial metabolism extends beyond SCFAs to include thousands of xenometabolites. Major knowledge gaps include xenometabolites associated with specific fiber substrates and their contributions to health.

Methods: To comprehensively catalog metabolites that are altered by dietary fiber, metabolomics were applied to human stool cultures derived from 3 healthy adults (3 anerobic culture lineages/each sampled after 7 days of culture) using soluble/insoluble fiber pairs of wheat bran, sorghum bran, wheat arabinoxylan [AX], and sorghum AX as fiber substrates, representing diverse polysaccharide structures and matrices. Culture supernatants (n=9/treatment) were subjected to RP-LC-HRMS/MS complex lipid analysis (triacylglycerides [TGs], diacylglycerides [DG], phospholipids [PLs], sphingolipids, ceramides, fatty acids [FAs]). Our aims were to identify xenolipids produced by gut bacterial communities consuming fiber and to test the hypothesis that specific multiple xenolipid metabolites discriminate fiber type.

Results: Partial Least-Squares Discriminant Analysis (PLS-DA) highlighted that microbial lipid metabolism is significantly altered depending on the nature of the fiber. For example, variance in 59 metabolites enabled the discrimination between wheat AX vs. sorghum AX:  57 metabolites (e.g., 12 ceramides, 35 TGs, 6 PLs, 3 FAs, 1 DG) were higher in wheat AX cultures and 2 metabolites (2 FAs) were higher in sorghum AX cultures.

Conclusions: Preliminary data support the idea that the gut microbial metabolism of different fibers can lead to remarkable metabolic shifts in complex lipid profiles. Additional platforms to be discussed include biogenic amines and other primary metabolites. These experiments will provide a comprehensive characterization of gut bacterial metabolism in response to dietary fibers, shedding light on potential molecular mechanisms that drive health effects.

Funding Sources: This work was funded in part by NIH-NIDDK.