A global HILIC-MS approach to measure polar human cerebrospinal fluid metabolome: Exploring gender-associated variation in a cohort of elderly cognitively healthy subjects.

Cerebrospinal fluid (CSF) is a key body fluid that maintains the homeostasis in central nervous system (CNS). As a biofluid whose content reflects the brain metabolic activity, the CSF has been profiled in the context of neurological diseases to provide novel insights into the disease mechanisms. However, a global high-throughput approach to measure a broad diversity of polar metabolites present in CSF is lacking. Although still perceived as challenging and less reproducible, hydrophilic interaction liquid chromatography (HILIC) has recently evolved to offer the unprecedented coverage capacity of water-soluble metabolome. Here, we present a global HILIC high-resolution mass spectrometry-based (HRMS) approach that combines the profiling in acidic pH ESI (+) and basic pH ESI (-) mode to extend the coverage of CSF polar metabolome. This approach allowed us to annotate and measure a broad range of central carbon metabolites (implicated in glycolysis, TCA cycle, nucleotide, amino acid and fatty acid metabolism) in CSF collected from cognitively healthy elderly volunteers (n = 32), using a single extraction method. Metabolite annotation was achieved using the accurate mass, RT and MS/MS criteria, allowing for the characterization of 146 measurable metabolites. Exploration of characterized individual CSF profiles allowed for a discovery of intriguing gender-associated differences, with significantly higher acylcarnitine levels in men and higher taurine levels women. With this case study, we demonstrate the value of combined HILIC ESI ± HRMS profiling to assess CSF metabolome in clinical research studies

Additional file 1: Supplementary Methods. of Alzheimer disease pathology and the cerebrospinal fluid proteome

Table S1. Demographics and clinical characteristics of subjects removed from the statistical analyses. Table S2. Non-AD versus AD CSF biomarker profile group comparison after selection in all subjects of 26 proteins with LASSO. Table S3. Non-AD versus AD CSF biomarker profile group comparison after selection in subjects with cognitive impairment of 18 proteins with LASSO. Table S4. Correlation of CSF proteins with CSF Aβ1-42. Table S5. Correlation of CSF proteins with CSF tau. Table S6. Correlation of CSF proteins with CSF P-tau181. Table S7. Group comparisons of CSF protein measurements for AD versus non-AD CSF biomarker profiles in all subjects. Table S8. Group comparisons of CSF protein measurements for AD versus non-AD CSF biomarker profiles in subjects with cognitive impairment. Figure S1. Box-plots of CSF proteins (selected with LASSO analyses) for positive and negative CSF profiles of AD pathology in all subjects and subjects with cognitive impairment. Figure S2. Pairwise correlation heatmap of the 26 CSF proteins selected with LASSO for classification of non-AD versus AD CSF biomarker profiles for all subjects. Figure S3. Pairwise correlation heatmap of the 18 CSF proteins selected with LASSO for classification of non-AD versus AD CSF biomarker profiles for subjects with cognitive impairment. Figure S4. Correlations of CSF neurogranin and neuromodulin with CSF tau and P-tau181. Figure S5. Chord diagram of the relationships of 59 CSF proteins with CSF tau, P-tau181, and/or Aβ1-42. Figure S6. Venn diagrams of CSF proteins with significant group comparison differences between AD versus non-AD CSF biomarker profiles and those correlating with CSF Aβ1-42, tau, and P-tau181. Figure S7. Venn diagrams of CSF proteins selected with LASSO to classify non-AD versus AD CSF biomarker profiles and those correlating with CSF Aβ1-42, tau, and P-tau181. (DOCX 2575 kb