HP and Diarrhea: Increased intestinal permeability is associated with pathogenesis of various diseases, especially in cholera-induced watery diarrhea.1 Dr. Fasano and his colleagues found that cells in the human intestine produce a protein that is almost identical to the zonula occludens toxin, a toxin related to pathogenesis of cholera, and they named it Zonulin.2-4 Zonulin is a protein, synthesized in intestinal and liver cells, that reversibly regulates intestinal permeability.