Gut Microbiota Across Early Stages of Synucleinopathy: From High-risk Relatives, REM Sleep Behavior Disorder to Early Parkinson's Disease

All subjects will undergo standard mechanical bowel preparation with 4 liters of polyethylene glycol (Klean-Prep, Norgine Ltd., Middlesex, UK). Total colonoscopy will be performed by experienced endoscopists under conscious sedation with intravenous benzodiazepines and narcotics. A conventional intermediate-length colonoscope (Olympus Corporation, Tokyo, Japan) will be used. One mucosal biopsy will be taken in the descending colon. Biopsies will be performed using standard biopsy forces without needle (Olympus Corporation, Tokyo, Japan). Half of the samples will be immersed in 4 oC normal saline solution. All samples will be immediately sent to pathology department and will be stored in a -80 oC freeze for processing of microbiota analyses.