Multi-omic evaluation of metabolic alterations in multiple sclerosis identifies shifts in aromatic amino acid metabolism

The circulating metabolome provides unique insights into multiple sclerosis (MS) pathophysiology, but existing studies are relatively small or characterized limited metabolites. We test for differences in the metabolome between people with MS (PwMS; n = 637 samples) and healthy controls (HC; n = 317 samples) and assess the association between metabolomic profiles and disability in PwMS. We then assess whether metabolic differences correlate with changes in cellular gene expression using publicly available scRNA-seq data and whether identified metabolites affect human immune cell function. In PwMS, we identify striking abnormalities in aromatic amino acid (AAA) metabolites (p = 2.77E−18) that are also strongly associated with disability (p = 1.01E−4). Analysis of scRNA-seq data demonstrates altered AAA metabolism in CSF and blood-derived monocyte cell populations in PwMS. Treatment with AAA-derived metabolites in vitro alters monocytic endocytosis and pro-inflammatory cytokine production. We identify shifts in AAA metabolism resulting in the reduced production of immunomodulatory metabolites and increased production of metabotoxins in PwMS. [Display omitted] •Significant alterations in the circulating metabolome are noted in multiple sclerosis•Aromatic amino acid (AAA) metabolite levels are linked to disease severity•Expression of AAA metabolism genes is altered in MS blood and CSF immune cells•AAA metabolites alter human monocyte cytokine production and endocytosis Fitzgerald et al. identify alterations in circulating aromatic amino acid (AAA) metabolites in multiple sclerosis that are related to disease severity. They also demonstrate changes in AAA metabolism-related gene expression in blood and cerebrospinal fluid immune cells, and that treatment with AAA metabolites alters monocyte pro-inflammatory cytokine production and endocytosis.