Proximity extension assay reveals serum inflammatory biomarkers in two amyotrophic lateral sclerosis cohorts

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disease with both clinical and hereditary heterogeneity. Inflammation has been suggested to play an important role in ALS pathophysiology. In this study, we aimed to identify serum inflammatory alterations and develop effective inflammatory biomarkers to assist in the diagnosis of ALS. Through proximity extension assay (PEA), we investigated serum inflammatory alterations in two ALS cohorts compared with healthy controls (HCs), including sporadic ALS patients and genetic ALS patients. We found that CHIT1, OSM, SIRT2, CDCP1 and 5 other factors were significantly increased in sporadic ALS patients in both cohorts and that SIRT2, CDCP1 and 6 other factors were different between genetic ALS patients and HCs. Using XGBoost and binary logistic regression analysis, we developed a two-serum protein diagnostic panel (CHIT1 and CDCP1), and the area under the curve (AUC) was 0.904 in the original cohort and 0.907 in the replication cohort. Based on Mendelian Randomization (MR), OSM and SIRT2 are significantly associated with the risk of ALS. In conclusion, our study revealed a consistent and replicable serum inflammatory profile and developed a biomarker panel that can differentiate ALS patients from HCs in two cohorts, which may play an important role in advancing our current understanding of the inflammatory process and identifying novel therapeutic strategies for ALS patients.