The role of serum zonulin level in diagnosis and disease activation in inflammatory bowel diseases

Aim: Inflammatory bowel diseases are an important health problem affecting the quality of life of patients with serious comorbidities in a significant part of the world. Many immunological, environmental, microbial and genetic factors are held responsible for its etiopathogenesis. Increased intestinal permeability is also one of the mechanisms held responsible in the etiopathogenesis. Intestinal permeability occurs in two different ways: transcellular and paracellular. The protein that provides the physiological regulation of paracellular permeability in the body is the protein Zonulin. Zonulin increases intestinal permeability via the paracellular pathway by causing the reversible decomposition of Tight Junction complexes between epithelial cells in the gastrointestinal tract. Therefore, it was thought that Zonulin protein may be responsible for the pathogenesis at the time of diagnosis and during the activation period in IBD patients. In our study, we aimed to investigate the place of serum Zonulin level as a clinical marker during the activation period in IBD patients. Material and Methods: The volunteer population was selected among the patients who applied to Ondokuz Mayıs University Faculty of Medicine, Department of Gastroenterology between January 2023 and March 2023. Inclusion criteria in our study; It was determined that the patients were older than 18 years of age, were diagnosed with IBD, and were in the disease activation period. Those under the age of 18, those who did not give their consent to participate in the study, those with a diagnosis of IBD and in remission, those with concomitant celiac disease and colorectal cancer were not included in the study. 70 volunteers were included in our study. Of the volunteers, 29 were UC patients in the disease activation period, 21 were Crohn's patients in the activation period, and 20 were healthy control group. Serum Zonulin level was studied in entire study population. Serum Zonulin concentrations were studied with the commercially available Human Zonulin ELISA kit in the Research Laboratory of Ondokuz Mayıs University Faculty of Medicine, Department of Medical Biochemistry, using the double-antibody sandwich method enzyme immunosorbent assay method. The data obtained between 3 different groups determined as Crohn's, UC and control groups were compared statistically. SPSS 25.0 program was used in the statistical data evaluation phase. Results: Significantly higher serum Zonulin levels were found in IBD patients compared to the control group (p ˂0.001). Significantly higher serum Zonulin levels were found in Crohn's and Uc patient groups compared to the control group (p ˂0.001, p ˂0.001). Serum Zonulin levels were found to be significantly higher in the UC patient group compared to the CD patient group (p = 0.012). No correlation was found between CDAI and Zonulin level in Crohn's patients, and there was no correlation between Truelove-witts index and Zonulin level in Uc patients. An inverse correlation was found between disease activation time and serum Zonulin levels (p = 0.021, r = -0.326 ) Conclusion: There is a need for easily applicable, inexpensive and highly specific markers to be used in the diagnosis and activation period of IBD. Serum Zonulin is a promising marker in this respect. Our study and studies in the literature support that the serum Zonulin level is clinically valuable in the diagnosis of IBD. The reverse correlation between activation time and Zonulin level shows that Zonulin level is affected by activation time. No correlation was found between activation severity and Zonulin level in our study, but this may be related to the small number of patients in the study. Larger-scale studies are needed on the role of Zonulin protein, one of the intestinal permeability indicators, in the diagnosis and follow-up of IBD.