A remarkable body of evidence links the zonulin-induced loss in small intestinal barrier function with diabetes mellitus, as elevated serum or fecal zonulin levels may predict the onset of the disease and shows correlation with poor glycaemic control in type 1 (T1D) [137,138,139] and type 2 (T2D) diabetes patients [69,140]. The gene discussed is HP; the disease is type 1 diabetes mellitus.