Zonulin is a protein that is involved in intestinal barrier function. It regulates the permeability of tight junctions between epithelial cells of the digestive tract and has been highlighted as a potential marker of so called "leaky gut" syndrome.
Zonulin is a human analogue of the Vibrio cholerae enterotoxin zonula occludens (ZOT). In disease, ZOT causes dysregulation of the tight junctions leading to increased intestinal permeability and diarrhoea.
Zonulin is a human protein that binds to a specific receptor on the surface of intestinal epithelia and triggers a cascade of biochemical events which induces tight junction disassembly. As a result the permeability of the intestinal epithelium increases allowing some substances to cross the barrier and trigger immune reactions.
A. Fasano et al discovered that the zonulin-zonulin-receptor system is more activated in coeliac disease and type 1 diabetes mellitus patients. Patients with active coeliac disease showed higher levels of zonulin and anti-zonulin antibodies compared to non-coeliac patients and patients in remission.
In addition, it has been reported that many people who suffer from coeliac disease also suffer from other autoimmune disorders. It is suggested that increased levels of zonulin are a contributing factor to the development of coeliac disease and other autoimmune disorders such as insulin dependent diabetes, multiple sclerosis and rheumatoid arthritis.