Atlas of one-carbon metabolism in conventional and germ-free mice reveals folate as a key determinant of biochemical pathways.

Folates participate in the one-carbon metabolism (OCM) cycle, supporting many biochemical pathways. Existing methods to profile folate are limited in the diversity of vitamers they measure and the samples they profile. Here we present a metabolomics workflow for stable extraction, separation and measurement of folates, along with precursors and products of OCM-associated pathways. We profile these metabolites in 37 mouse tissues to chart an interactive 'OCM atlas' ( https://chaudharilab.com/folate-atlas/ ), revealing vast heterogeneity across organs and an uncharacterized folate derivative. We discover that, in adult mice, the gut microbiota is a consumer of folate and folate polyglutamylation in the host is not regulated by folate availability. Germ-free mice show tissue-specific shifts in methyl donor abundances relative to conventionally raised mice, indicative of altered DNA methylation. Correlation analyses uncover the central roles of folates in potentially modulating other biochemical pathways in tissues, thus linking microbial folate consumption directly to its global impacts on host metabolism.