Osteopontin levels in the serum reflect anatomical disease progression in patients with amyotrophic lateral sclerosis

Background: Amyotrophic lateral sclerosis (ALS) lacks biomarkers for diagnosis, prognostic stratification, and evaluation of response to potential treatments. Previous research supported the role of serum osteopontin (OPN) levels as a potential biomarker in ALS. However, the associations of OPN serum levels with clinical features and their trend over the disease course have not been explored yet. Methods: We measured OPN serum levels in a retrospective cohort of 110 well-characterized patients with ALS, using a commercial ELISA kit, and analyzed their association with demographic and clinical features, as well as with other serum biomarkers. For a subset of patients, longitudinal measurements were available. Results: OPN serum levels differed significantly between patients with ALS and a cohort of 45 age and sex-matched healthy controls. However, when considering potential differential diagnoses, elevated OPN serum levels were not specific for ALS. Patients with an advanced disease stage (King’s stage 3 or 4) exhibited significantly higher OPN serum levels compared to patients at earlier disease stages, whereas we did not observe any correlation with ALSFRS-R and progression rate. We observed an inverse correlation between OPN serum levels and BMI at diagnosis. Higher OPN serum levels predicted a shorter survival time and a shorter time to King’s stage 4. No significant association between serum OPN and serum neurofilament light or glial fibrillary acid protein levels was observed. OPN serum levels were substantially stable over a 9-month observation time. Conclusion: Our findings indicate that serum OPN is an informative biomarker in ALS, providing valuable prognostic insights, potentially reflecting the extent of disease, and demonstrating potential applications in clinical trials.