The mycobiota-gut-brain axis in Parkinson's disease: A review on what we know and what paths we can still take to advance this field of study

The microbiota-gut-brain axis is a bidirectional pathway that acts in different neurodegenerative diseases, such as sporadic Parkinson's disease. However, most studies have evaluated only the gut bacterial ecology of Parkinson's disease patients. Here, the aim was to explore gut microbiota's role in Parkinson's disease. The findings suggest that molds and yeasts, or their secondary metabolites, could not only protect but also induce the leading clinical Parkinson's disease symptoms. Nevertheless, there is still no cause-effect about the gut mycobiota and sporadic Parkinson's disease onset and progression. Throughout this review, fungi are highlighted as a possible key piece in Parkinson's disease etiology. Furthermore, the different experimental approaches that might be useful to investigate the mycobiota-gut-brain axis are proposed.