Metabolomics technology has emerged as a tool to study small molecules influenced by age, sex, genetics, lifestyle, and disease processes. Correlating metabolites in cerebrospinal fluid (CSF) with established and developing Alzheimer’s disease (AD) CSF biomarkers may elucidate additional changes that are associated with early AD pathology and enhance our knowledge of the disease.

The relative abundance of untargeted metabolites was assessed via Metabolon’s UHPLC/MS platform in 161 non‐Hispanic white, cognitively unimpaired individuals from the Wisconsin Registry for Alzheimer’s Prevention (WRAP). A metabolome‐wide association study (MWAS) was conducted between 269 known CSF metabolites and CSF biomarkers, which were measured with the exploratory Roche NeuroToolKit assays, a panel of automated robust prototype immunoassays (Roche Diagnostics International Ltd): phosphorylated tau (P‐tau), total tau (T‐tau), amyloid β (Aβ42), Aβ42/40, neurofilament light protein (NFL), neurogranin, chitinase‐3‐like protein 1 (YKL‐40), S100b, glial fibrillary acidic protein (GFAP), interleukin‐6 (IL‐6), soluble triggering receptor expressed on myeloid cells 2 (sTREM2), and α‐synuclein. Linear mixed‐effects regression analyses were performed with random intercepts for individual and family adjusting for age, gender, body mass index, and years of education. The metabolome‐wide significance was determined by a false discovery rate (FDR)‐corrected p<0.05. The significant metabolites from WRAP were subsequently tested in 154 non‐Hispanic white, cognitively unimpaired individuals from the Wisconsin Alzheimer’s Disease Research Center (ADRC). Using single nucleotide polymorphisms (SNP) associated with the top metabolites, we applied linear mixed‐effects models to perform mediation analyses.

The MWAS results for each NeuroToolKit biomarker from WRAP are shown in Figure 1. Metabolites were significantly associated with all biomarkers except Ab42/40 and IL‐6. Top metabolites that were associated with multiple NeuroToolKit CSF biomarkers are shown in Table 1. Significant mediation effects of stearoyl sphingomyelin(d18:1/18:0)(SM(d18:1/18:0)) were detected for P‐tau and sTREM2 (Figure 2).

This study provides evidence that CSF metabolites are associated with AD‐related pathology through most AD CSF biomarkers and may be influenced by upstream genetic variation. The significant results for Aβ42 and Aβ40, but nonsignificant results for Aβ42/40 indicate that the metabolites associated with Aβ42 and Aβ40 may influence production of amyloid in general versus clearance of the pathological form, Aβ42.