More recently, previous studies conducted with PD patients have shown evidence of an altered intestinal microbiota, systemically releasing endotoxins such as lipopolysaccharides and metabolic products facilitating their entry into the CNS promoting the activation of the microglia inducing inflammatory responses, such as the release of pro-inflammatory cytokines (IL1-α, IL-β, IL-6 and TNF-α), leading to the degeneration of dopaminergic neurons [66,67]. Here, IL1A is linked to Parkinson disease.