ObjectivesHuman zonulin is a protein that increases permeability in the epithelial layer of the small intestine by reversibly modulating the intercellular tight junctions. There is not sufficient information available about zonulin's participation in inflammatory bowel diseases (IBD). The aim of this study was therefore to investigate fecal and serum zonulin in IBD patients and its relation to the disease localization, behavior and smoking status.Design and methodsForty IBD patients and forty healthy persons were examined for fecal and serum zonulin concentrations by competitive ELISA (DRG International Inc). Values were correlated to IBD type, localization and behavior, and smoking.ResultsSerum and fecal zonulin were significantly higher in patients with Crohn’s disease compared to ulcerative colitis (p = 0.038 for fecal zonulin, and p = 0.041 for serum zonulin concentrations). No association of serum or fecal zonulin was found with respect to IBD localization and behavior. The only difference was found with respect to smoking. Both the IBD cohort and healthy smokers showed significantly higher fecal zonulin levels (median 203 ng/mL) compared to non-smokers (median 35.8 ng/mL), p < 0.001.ConclusionsFecal and serum zonulin levels are elevated in patients with active Crohn’s disease but not with ulcerative colitis. High fecal zonulin levels in smokers irrespective of IBD point to the significant and undesirable up-regulation of gut permeability in cigarette smokers.

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