Serum Zonulin Is a Biomarker for Severe Asthma

Zonulin is a regulator of epithelial and endothelial barrier function. It regulates intestinal permeability through disrupting tight junctions. Defective epithelial barrier function is a hallmark of airway inflammation in asthma. This study aimed to investigate the role of zonulin in the pathogenesis of severe asthma. We enrolled 56 adult patients with asthma (29 severe asthma and 27 mild-to-moderate asthma) and 33 normal controls. The clinical data, sera, and lung tissues of the patients were provided by the Cohort for Reality and Evolution of adult Asthma in Korea (COREA) and the Biobank of Soonchunhyang University Bucheon Hospital, South Korea. Serum zonulin levels were estimated using an enzyme-linked immunosorbent assay, and zonulin expression in the bronchial tissue was evaluated by immunohistochemical staining. The serum zonulin levels were significantly higher in patients with severe asthma (51.98 ± 19.66 ng/mL) than in those with mild-to-moderate asthma and normal controls (26.35 ± 13.70 vs. 17.26 ± 10.29 ng/mL, P < 0.001). They significantly correlated with percent predicted forced expiratory volume in one second (%FEV1) (r = -0.35, P = 0.009). The zonulin expression in the bronchial epithelium was greater in patients with severe asthma. A serum zonulin cutoff value to distinguish between severe and mild-to-moderate asthmatics was 38.83 ng/mL. Zonulin may play an important role in the pathogenesis of severe asthma, and serum zonulin could be a potential biomarker for severe asthma.