Faecal microbiota transplant for Parkinson's disease: promises and future directions.

There is considerable evidence linking alterations in gut microbiome composition with Parkinson's disease, leading to several recent randomized controlled faecal microbiota transplantation (FMT) trials in patients with Parkinson's disease targeting gut dysbiosis with the aim to modulate the gut-brain axis. Some FMT trials have observed motor and non-motor symptoms improvements in patients with Parkinson's disease, possibly through microbiota linked enhanced short-chain fatty acid or other metabolite effects and reduced systemic inflammation. While the findings are exciting and can potentially open a new treatment paradigm, crital questions on donor selection, the optimal screening and selection of the donor microbiome, delivery routes and the timing and frequency of transplantation need to be addressed. We suggest that future FMT trials should incorporate blood, metabolites, urine and functional neuroimaging biological markers and to control for dietary, lifestyle comorbidities, medication intake and/or other potential variables to ensure optimal evaluation of interactions between the gut microbes and brain outcomes prospectively over a longer time frame.