TJP1 and irritable bowel syndrome: Research has identified junctional molecules such as claudins, occludin, zonula occludens-1 (ZO-1), and regulatory proteins like secretory IgA (sIgA) and zonulin as potential biomarkers for several pathological conditions, including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), food allergy, metabolic diseases, and leaky gut syndrome [20–23].