Recent data suggest that the brain-gut axis, chronic intestinal inflammation and microbiome may contribute to the pathogenesis of neurodegenerative diseases with alfa-synucleinopathy, which include Parkinson's disease (PD) and Multiple system atrophy (MSA). Environmental factors e.g. diets, microbiome, metabolites and immune mechanisms may play important role in pathogenesis of these diseases. In the human arm of this project, the investigators will address effects of an anti-inflammatory gluten-free diet (GFD) on motor and non-motor symptoms as well as its effects on immune and metabolomic characteristics in patients with PD and MSA. In the mouse arm, the investigations will focus on the effects of GFD in chronic MPTP-induced mouse model of PD in various settings (e.g. in young or aged animals, with respect to the lengths of exposure to GFD). The chronic MPTP model will be used to assess the effects of GFD on adaptive and immune characteristics, and metabolic signatures. Using germ-free animals, the microbiome-dependency of the GFD-mediated effects may be determined. The anti-inflammatory gluten-free diet and its related mechanisms represent novel, promising and relatively straightforward approach in a search to improve symptoms of PD as well as MSA or even in their prevention.