AOC1 and Parkinson disease: In this regard, independent studies report no differences in serum IL-6, C-reactive protein, TNF-α, fecal zonulin, colonic ZO-1 and in the gut mucosal integrity marker serum diamine oxidase in samples obtained from PD patients compared to controls [130,134,145], and no changes in intestinal permeability were observed in mice treated with the PD-inducing compound rotenone, a well-known pesticide [152].