TLR2 and Parkinson disease: In addition, genome-wide association studies have identified numerous genetic risks that increase susceptibility to sporadic PD, and several genes are related to gut microbial regulation and intestinal inflammation, including pattern recognition receptors TLR1 and TLR2, peptidoglycan recognition protein, and MUC2, a component of the mucosal layer that protects the intestinal epithelial barrier [174].