title: Bacterial lipodipeptide, Lipid 654, is a microbiome-associated biomarker for multiple sclerosis.
abstract: Multiple sclerosis (MS) is an autoimmune disease of unknown etiology. Infectious agents have been suggested to have a role as environmental factors in MS, but this concept remains controversial. Recently, gastrointestinal commensal bacteria have been implicated in the pathogenesis of autoimmune diseases, but mechanisms underlying the relationship of human systemic autoimmunity with the commensal microbiome have yet to be identified. Consistent with the lack of understanding of pathogenic mechanisms and relevant environmental factors in MS, no blood biomarkers have been identified that distinguish MS patients from healthy individuals. We recently identified a unique gastrointestinal and oral bacteria-derived lipodipeptide, Lipid 654, which is produced by commensal bacteria and functions as a human and mouse Toll-like receptor 2 ligand. Using multiple-reaction-monitoring mass spectrometry, a critical approach in targeted lipidomics, we now report that Lipid 654 can be recovered in the serum of healthy individuals. Most interestingly, we find that Lipid 654 is expressed at significantly lower levels in the serum of patients with MS compared with both healthy individuals and patients with Alzheimer's disease. These results thus identify for the first time a potential mechanism relating the gastrointestinal and oral commensal microbiome to a human systemic autoimmune disease. In addition, these results also identify a potential etiologic environmental factor and novel clinically relevant serum biomarker for MS.
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, CT, USA.
authors.forename: Vahid
authors.initials: V
authors.lastname: Farrokhi
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, CT, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Nemati
authors.affiliation: Department of Oral Health and Diagnostic Sciences, University of Connecticut School of Dental Medicine , Farmington, CT, USA.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Nichols
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, CT, USA.
authors.forename: Xudong
authors.initials: X
authors.lastname: Yao
authors.affiliation: Department of Immunology, University of Connecticut School of Medicine, University of Connecticut Health Center , Farmington, CT, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Anstadt
authors.affiliation: Department of Immunology, University of Connecticut School of Medicine, University of Connecticut Health Center , Farmington, CT, USA.
authors.forename: Mai
authors.initials: M
authors.lastname: Fujiwara
authors.affiliation: Department of Community Medicine and Health Care, University of Connecticut School of Medicine , Farmington, CT, USA.
authors.forename: James
authors.initials: J
authors.lastname: Grady
authors.affiliation: Department of Community Medicine and Health Care, University of Connecticut School of Medicine , Farmington, CT, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Wakefield
authors.affiliation: Department of Neurology, University of Connecticut School of Medicine , Farmington, CT, USA.
authors.forename: Wanda
authors.initials: W
authors.lastname: Castro
authors.affiliation: Department of Neurology, University of Connecticut School of Medicine , Farmington, CT, USA.
authors.forename: James
authors.initials: J
authors.lastname: Donaldson
authors.affiliation: Department of Immunology, University of Connecticut School of Medicine, University of Connecticut Health Center , Farmington, CT, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Clark
keywords: TLR2; autoimmunity; biomarker; commensal bacteria; microbiome; multiple sclerosis