Gut changes
Understanding of the role of the enteric nervous system (ENS) and the links between the gut, the brain and the gut microbiome in IBS is increasing. With so many potential factors involved, much of the research currently shows association between elements but more work is needed on causation and possible pathways.10
Evidence that immune activation is an important cause of IBS is increasing, with researchers identifying autoimmune responses and visceral hypersensitivity linked to changes in gut motility.
Immunological changes in people with IBS can include increased mast cell levels in the small and large intestines, compared to the general population. Increased levels of cytokines such as interleukin-1 (IL-1), IL-6, IL-8 and tumour necrosis factor-alpha, but lower IL-10 levels are also found in IBS. Infections may also alter the ratio of Th1 and Th2 T-helper cells.11
One aspect common to the different types of IBS is an increased intestinal permeability, affecting the intestinal barrier function. This has been associated in changes in the tight junction (the continuous intercellular barrier between epithelial cells) which is related in turn to intestinal mucosal mast cell activation and psychological stress.12