In particular, the colonic mucosa of IBS patients displays low occludin expression.(7) Another report indicates that occludin and claudin-1 protein levels are lower in IBS-D compared to constipation-predominant IBS (IBS-C) or IBS with mixed bowel habits (IBS-M), even though the expression of occludin and claudin-1 is similar in IBS-C, IBS-M and healthy subjects.(8) Although these data indicate changes in the expression of genes encoding for TJ proteins in IBS patients, these studies only investigated specific intestinal regions of the intestines. Here, OCLN is linked to irritable bowel syndrome.