Association of serum Spp1 levels with disease progression in ALS and SBMA

Objective: In comparison with amyotrophic lateral sclerosis (ALS), the contribution of neuroinflammation in spinobulbar muscular atrophy (SBMA) has been less explored. We investigated the role of neuroinflammation in the pathogenesis of ALS and SBMA by analyzing systemic inflammatory markers and osteopontin (Spp1).

Methods: This study involved 105 ALS, 77 SBMA, and 55 healthy controls. We measured their systemic inflammatory markers, serum Spp1, and cytokine levels (interferon-γ, interleukin [IL]-1β, IL-6, IL-8, IL-10, tumor necrosis factor-α, and IL-17A), investigated correlations between Spp1 levels and clinical features, and evaluated ALS survival rates according to Spp1 levels.

Results: In the ALS group, systemic inflammatory markers were significantly higher than in the control and SBMA groups. Spp1 levels were observed to be higher in ALS patients, but the difference was not statistically significant among the study groups. Cytokine profiles were comparable. In ALS, higher Spp1 levels were correlated with lower ALS Functional Rating Scale-Revised (ALSFRS-R) scores (r = -0.25, p = 0.02) and faster disease progression rate (r = 0.37, p < 0.001). After adjusting for other prognostic indicators, high Spp1 levels were independently associated with shorter survival in ALS patients (hazard ratio 13.65, 95% confidence interval 2.57-72.53, p < 0.01).

Interpretation: Neuroinflammation does not appear to be a primary contributor to the pathogenesis of SBMA. Serum Spp1 levels may serve as a reliable biomarker for disease progression and prognosis in ALS. These findings expand our understanding of these two distinct motor neuron disorders and offer a potential biomarker for future studies.