Fecal Zonulin as a Noninvasive Biomarker of Intestinal Permeability in Pediatric Patients with Inflammatory Bowel Diseases—Correlation with Disease Activity and Fecal Calprotectin

Background: Recent data indicate that increased intestinal permeability plays a key role in the pathogenesis of inflammatory bowel diseases (IBD) and correlates with disease flare. Since zonulin related proteins (ZRP) are the proteins that increase permeability in the epithelial layer of the small intestine by reversibly modulating the intercellular tight junctions, they may serve as a new, noninvasive biomarker of disease activity. The aim of this study was to investigate fecal ZRP in pediatric IBD patients as well as its correlation with disease activity and fecal calprotectin (FCP). Methods: Ninety-four individuals: 47 Crohn’s disease (CD) patients, 41 ulcerative colitis (UC) patients, and 6 healthy controls were examined for fecal ZRP. Values were correlated to IBD type, disease activity for IBD patients, and FCP for all children included in the study. A stool specimen was collected the day before the visit to the hospital, then fecal ZRP and FCP were tested using the ELISA test. Non-parametric statistical tests were used for data analysis. Results: The level of fecal ZRP was higher among IBD patients compared to the control group (CG): medians for CD—113.3 (53.6–593.6) ng/mL; UC—103.6 (50.7–418.3) ng/mL; and CG—46.9 (31.8–123.0) ng/mL (p < 0.05). No difference in fecal ZRP concentration was observed between children with CD and those with UC (p = 0.55). A slight correlation between disease activity (PCDAI for CD and PUCAI for UC) and the fecal ZRP level was found for CD (p = 0.03/R = 0.33), but not UC (p = 0.62/R = 0.08), patients. A correlation between fecal ZRP and FCP was observed (R = 0.73, p = 0.00). Conclusions: Fecal ZRP levels are increased among those with IBD, are associated with CD activity, and strongly correlate with FCP. Further research into the role of intestinal permeability in IBD and the clinical usefulness of ZRP in IBD is warranted.