Metabolomics identifies shared lipid pathways in independent amyotrophic lateral sclerosis cohorts.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease lacking effective treatments. This is due, in part, to a complex and incompletely understood pathophysiology. To shed light, we conducted untargeted metabolomics on plasma from two independent cross-sectional ALS cohorts versus control participants to identify recurrent dysregulated metabolic pathways. Untargeted metabolomics was performed on plasma from two ALS cohorts (cohort 1, n = 125; cohort 2, n = 225) and healthy controls (cohort 1, n = 71; cohort 2, n = 104). Individual differential metabolites in ALS cases versus controls were assessed by Wilcoxon, adjusted logistic regression, and partial least squares-discriminant analysis, while group lasso explored sub-pathway level differences. Adjustment parameters included age, sex, and body mass index. Metabolomics pathway enrichment analysis was performed on metabolites selected by the above methods. Additionally, we conducted a sex sensitivity analysis due to sex imbalance in the cohort 2 control arm. Finally, a data-driven approach, differential network enrichment analysis (DNEA), was performed on a combined dataset to further identify important ALS metabolic pathways. Cohort 2 ALS participants were slightly older than controls (64.0 vs. 62.0 years, p = 0.009). Cohort 2 controls were over-represented in females (68%, p < 0.001). The most concordant cohort 1 and 2 pathways centered heavily on lipid sub-pathways, including complex and signaling lipid species and metabolic intermediates. There were differences in sub-pathways that enriched in ALS females versus males, including in lipid sub-pathways. Finally, DNEA on the merged metabolite dataset of both ALS and control cohorts identified nine significant subnetworks; three centered on lipids and two encompassed a range of sub-pathways. In our analysis, we saw consistent and important shared metabolic sub-pathways in both ALS cohorts, particularly in lipids, further supporting their importance as ALS pathomechanisms and therapeutics targets.