While PD-related gut microbiota dysbiosis has been associated with the impairment of the short-chain fatty acids (SCFAs) producing process, lipid metabolism, immunoregulatory function, and intestinal permeability [468], it has been shown that meth exposure decreases the expression of tight junction proteins zonula occludens-1 (ZO-1) and epithelial cell adhesion molecule (EpCAm) in the intestinal tissue of mice, where the presence of fatty acid-binding protein 1 (FABP-1) in sera further suggests disruption of the gut wall [469]. Here, FABP1 is linked to Parkinson disease.