Zonulin

Zonulin is an inflammatory protein that regulates intestinal permeability by opening or closing the tight junctions between cells in the lining of the digestive tract. Zonulin is uncleaved haptoglobin.

Disease risk
In normal physiology, it provides protection against gut infection. Zonulin is antimicrobial and antimilarial. However, it has been linked increased risk of type 1 diabetes, Crohn's disease, inflammatory disease, primary sclerosing cholangitis, and susceptibility to idiopathic Parkinson's disease.

Gluten sensitivity
Gliadin (glycoprotein present in wheat) activates zonulin, leading to increased intestinal permeability to macromolecules. Zonulin expression is increased in individuals who have gluten sensitivity, whether or not they have celiac disease. Increased expression may be a risk factor for autoimmune disease.

Learn more

 * Zonulin, Wikipedia
 * A Protein In The Gut May Explain Why Some Can't Stomach Gluten, NPR, December 9, 2015