Therapeutic Targets of Probiotics in Parkinson Disease: A Systematic Review of Randomized Controlled Trials.

Introduction: Parkinson disease is the world's second most prevalent neurological disease. In this disease, intracytoplasmic neuronal inclusions are observed in enteric neurons in the gastrointestinal tract, and the composition of the intestinal microbiome is altered. These changes correlate with the motor phenotype. A systematic review was conducted to determine the effect of using probiotics in Parkinson disease.

Methods: Scopus, PubMed, Web of Science, the Cochrane Library, ScienceDirect, and Ovıd-LWW were searched until April 2021. A total of 27395 records were found according to inclusion and exclusion criteria with the following outcomes: Parkinson disease rating, oxidative stress, and gastrointestinal system markers. Data search, article selection, and data extraction assessments were performed according to the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. The Jadad scale was used to rate the evidence's quality.

Results: Our study information was gathered from 5 randomized controlled trials involving 350 individuals with Parkinson disease receiving probiotic supplements. Parkinson disease rating and non-motor symptoms test were performed in the samples. Also, oxidative stress (glutathione, malondialdehyde) and gastrointestinal system symptoms (bowel opening frequency, gut transit time, complete bowel movement, spontaneous bowel movements) were evaluated during 4-12 weeks of using probiotics in these patients.

Conclusion: While all high-quality studies demonstrate improvement in disease symptoms of the patients, currently sufficient data are not available to recommend the use of probiotics for people with Parkinson disease in clinical practice.