Serum zonulin in patients with inflammatory bowel disease: a pilot study

BACKGROUND: In recent years it has been supposed that impaired intestinal permeability represents an early event preceding the onset of inflammatory bowel disease (IBD). Since zonulin has been proposed as a biomarker of intestinal permeability, we investigated its role in patients with IBD and the correlation between serum and fecal zonulin. METHODS: A total of 118 IBD patients (86 Crohn's disease [CD] and 32 ulcerative colitis [UC]) and 23 healthy controls (HC) were prospectively enrolled. A serum sample was collected for all the subjects included in the study. A stool specimen collected in the same day of blood drawing was available for a subgroup of 33 IBD patients. Serum and fecal zonulin were tested by ELISA. Non-parametric statistical tests were used for data analysis. RESULTS: Serum zonulin concentration was higher in IBD patients compared to HC (34.5 [26.5-43.9] ng/mL vs. 8.6 [6.5-12.0] ng/mL, P<0.001) showing an area under the curve of 0.98 for their discrimination. No difference in serum zonulin concentration was observed between patients with CD and those with UC (P=0.074). An inverse correlation was observed between serum zonulin concentration and disease duration (r(s)=-0.30, P=0.001); no correlation was observed between serum and fecal zonulin (r(s)=0.15, P=0.394). CONCLUSIONS: Serum zonulin is highly sensitive for the evaluation of intestinal permeability in IBD patients. There is no correlation between zonulin values in serum and feces.