Systemic dysregulation of apolipoproteins in amyotrophic lateral sclerosis serum

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron degeneration. Increasing evidence implicates systemic lipid perturbation in ALS pathogenesis. However, the extent and nature of apolipoprotein changes underlying lipid perturbations in ALS remain largely unknown. To address this, we performed a comprehensive analysis of major apolipoproteins involved in lipid metabolism and examined their association with lipoprotein membrane lipids in sporadic ALS (n = 32) and age-matched healthy controls (n = 32), using ELISA and liquid chromatography-mass spectrometry. Compared with controls, serum levels of apoB, apoCI, apoCII, apoCIII and apoE were significantly elevated in ALS, whereas apoAI and apoAII were unchanged. Distributional analyses demonstrated a relative decrease in apoAI and an increase in apoB in ALS, resulting in an elevated apoB/apoAI ratio, a marker of atherogenic risk, alongside a reduced apoAI/apoE ratio. Correlation analyses revealed strengthened interrelationships among apolipoproteins in ALS, suggesting altered regulatory coordination. At the lipid level, phosphatidylcholine (PC) was increased, whereas sphingomyelin (SM) was reduced in ALS serum. Notably, the strong associations of apoB to both PC and SM observed in controls were absent in ALS. Biomarker analyses identified apoE as the strongest discriminator between ALS and control groups. Collectively, these findings demonstrate a coordinated disruption of apolipoproteins and lipoprotein-associated lipids in ALS serum, with likely functional consequences for lipoprotein metabolism. This study provides new insights into lipid dysregulation in ALS pathobiology and supports the emerging view that ALS encompasses not only neurodegenerative processes but also systemic metabolic reprogramming.