{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T14:48:44Z","timestamp":1792162124641,"version":"4.4.0"},"reference-count":34,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2024,9,26]],"date-time":"2024-09-26T00:00:00Z","timestamp":1727308800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical University of Silesia","award":["BNW-1-001\/N\/4\/I"],"award-info":[{"award-number":["BNW-1-001\/N\/4\/I"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Background: Considering the increasing worldwide prevalence of inflammatory bowel disease (IBD), the early diagnosis of this disease is extremely important. However, non-invasive diagnostic methods remain limited, while invasive techniques are the most commonly used in daily practice. Therefore, there is a serious need to find new non-invasive biomarkers of IBD. Methods: The serum profiles of occludin, claudin-2, and zonulin were assessed in IBD patients using the ELISA method. The levels of the analyzed biomarkers were measured before and after a year of anti-inflammatory treatment, which was a tumor necrosis factor \u03b1 (TNF-\u03b1) inhibitor (adalimumab) in patients with ulcerative colitis (UC) and conventional therapy in patients with Crohn\u2019s disease (CD). Results: In IBD patients, the serum level of occludin (p &lt; 0.001) decreased compared to healthy individuals, while the level of claudin-2 (p &lt; 0.001) increased. Additionally, zonulin (p &lt; 0.01) concentration increased in CD patients compared to the control group. The highest diagnostic ability was presented by occludin measurements with the area under the curve (AUC) of 0.959 (95% CI 0.907\u20131) in UC and 0.948 (95% CI 0.879\u20131) in CD. Claudin-2 also demonstrated very good ability in diagnosing UC and CD with AUC values of 0.864 (95% CI 0.776\u20130.952) and 0.896 (95% CI 0.792\u20130.999), respectively. The ability of zonulin to diagnose CD was estimated as good with an AUC of 0.74 (95% CI 0.598\u20130.881). Moreover, a significant correlation was identified between C-reactive protein (CRP), claudin-2 (r = \u22120.37; p &lt; 0.05), and zonulin (r = \u22120.44; p &lt; 0.05) in UC patients. Treatment with adalimumab improved the level of occludin, claudin-2, and zonulin in UC patients, while anti-inflammatory conventional therapy decreased the concentration of zonulin in CD. Conclusions: Occludin and claudin-2 measurements present significant utility in diagnosing both UC and CD, while zonulin assessments may be useful in CD diagnosis. Additionally, claudin-2 and zonulin measurements may be helpful in evaluating the intensity of the inflammatory process. Anti-TNF-\u03b1 treatment improved the value of occludin, claudin-2, and zonulin, indicating its beneficial effect on the integrity of tight junctions in UC.<\/jats:p>","DOI":"10.3390\/molecules29194577","type":"journal-article","created":{"date-parts":[[2024,9,26]],"date-time":"2024-09-26T09:46:20Z","timestamp":1727343980000},"page":"4577","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":55,"title":["Biochemical Modulators of Tight Junctions (TJs): Occludin, Claudin-2 and Zonulin as Biomarkers of Intestinal Barrier Leakage in the Diagnosis and Assessment of Inflammatory Bowel Disease Progression"],"prefix":"10.3390","volume":"29","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9818-9221","authenticated-orcid":false,"given":"Aleksandra","family":"G\u00f3recka","sequence":"first","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Agnieszka","family":"Jura-P\u00f3\u0142torak","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4502-0828","authenticated-orcid":false,"given":"Ewa M.","family":"Ko\u017ama","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8445-2490","authenticated-orcid":false,"given":"Anna","family":"Szeremeta","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5833-2628","authenticated-orcid":false,"given":"Krystyna","family":"Olczyk","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2307-5884","authenticated-orcid":false,"given":"Katarzyna","family":"Komosi\u0144ska-Vassev","sequence":"additional","affiliation":[{"name":"Department of Clinical Chemistry and Laboratory Diagnostics, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,9,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7247238","DOI":"10.1155\/2019\/7247238","article-title":"A Comprehensive Review and Update on the Pathogenesis of Inflammatory Bowel Disease","volume":"2019","author":"Guan","year":"2019","journal-title":"J. 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