Serum zonulin levels and intestinal permeability in Behçet's syndrome: a cross-sectional study

Increased intestinal permeability has been implicated in the pathogenesis of autoimmune and inflammatory conditions, including Behçet syndrome (BS). Zonulin, an endogenous regulator of intestinal tight junctions, serves as a biomarker for assessing intestinal barrier integrity. We aimed to evaluate intestinal permeability in patients with BS using serum zonulin levels, a novel and validated biomarker for intestinal barrier dysfunction.

A total of 173 participants were enrolled: 87 patients with BS, 20 patients with Crohn's disease (CD), and 66 healthy controls. Patients with active gastrointestinal symptoms, risk factors or using medications known to affect intestinal permeability, were excluded. Serum zonulin levels were measured using ELISA. High levels indicate increased intestinal permeability. Behçet Disease Current Activity Form and Crohn's Disease Activity Index were used to assess disease activities.

Median serum zonulin level was significantly lower in BS patients (24 ng/mL, IQR: 18-43) compared to CD patients (112 ng/mL, IQR: 22-204) and healthy controls (109 ng/mL, IQR: 36-226) (p<0.01). Multivariate logistic regression analysis identified female sex as the only independent predictor of elevated zonulin levels (OR=13.5, 95% CI: 2.5-72). Immunosuppressives, disease duration, age, and major organ involvement were not significantly associated with serum zonulin levels.

In this cross-sectional study, patients with BS did not exhibit increased intestinal permeability. Longitudinal studies, including treatment-naive patients, are required to better understand the role of intestinal permeability and gut microbiota alterations in the pathogenesis and disease activity of BS.