GCG and Parkinson disease: Clostridium butyricum treatment also ameliorates motor deficits, dopaminergic neuronal loss, synaptic dysfunction and microglial activation in mice with MPTP-induced PD, and these effects are associated with restoration of the gut microbiome and reduced levels of colonic glucagon-like peptide-1 (GLP-1), colonic G-protein-coupled receptor 41/42 and cerebral GLP-1 receptor [132].