Serum zonulin levels in newly diagnosed multiple sclerosis patients: associations with disease phenotype and activity. Results from the Promising study

Introduction: The breakdown of the intestinal barrier has been linked with MS pathophysiology. Blood biomarkers of intestinal permeability, like zonulin, have been associated with MS, although their correlation with disease activity remains controversial. Objectives/Aims: This study aims to assess serum zonulin con- centrations in newly diagnosed, treatment-naïve MS patients, and to explore potential association with disease phenotype and inflammatory activity. Methods: Serum samples were collected from 78 MS patients (63 with relapsing MS and 15 with progressive MS) who referred to the MS Centre of the University Hospital of Ferrara and diagnosed between October 2020 and May 2024. Exclusion criteria included age less than 18 years, concomitant inflamma- tory bowel disease or irritable bowel syndrome, and treatment with high-dose corticosteroids in the previous month. Demographic and clinical data including EDSS, the occurrence of relapses within 2 months before serum sampling and baseline MRI activity were collected. Non parametric tests were used to assess the association between zonulin levels and disease characteristics. Results: Zonulin levels were higher in relapsing MS patients compared to the progressive ones after adjustment for sex (5.88 ng/mL vs 2.96 ng/mL, p=0.031); however, this difference lost significance when age and EDSS were also included as covari- ates. Although zonulin levels tended to be higher in patients with baseline MRI activity and in those who had a recent MS relapse, this difference did not reach statistical significance. Zonulin negatively correlated with EDSS (p=0.006, Rho -0.307), while it was not associated with age at the study time and with sex. Conclusion: This cross-sectional study on newly diagnosed MS patients suggests that zonulin levels are higher in patients with relapsing-onset MS compared to those with progressive-onset MS, indicating a possible association with disease presentation. Zonulin concentrations were also inversely associated with EDSS scores, while no significant differences emerged in rela- tion to recent disease activity. Further studies are required to clarify the clinical relevance and potential predictive role of this biomarker