ADL	activity of daily living
ANA	antinuclear antibodies
BID	bis in die,’ two times a day’
BMs	number of bowel movements.
BSFS	Bristol stool form scale
BSS	Bristol stool scale
CagA	cytotoxin-associated gene A
CFU	colony-forming unit
CI	confidence interval
CNS	central nervous system
ENS	enteric nervous system
FMT	fecal microbiota transplantation
FOS	fructooligosaccharides
GABA	gamma-aminobutyric acid
GBT	glucose breath test
GI	gastrointestinal
GTT	gut transit time
HAMA	Hamilton anxiety scale
HAMD-17	Hamilton depression rating scale (HDRS)
HP	Helicobacter pylori
HS-CRP	high-sensitivity C-reactive protein
H-Y	Hoehn–Yahr
IBS	irritable bowel syndrome
IL	interleukin
LBT	lactulose breath tests
MALT	mucosa-associated lymphoid tissue
MDA	malondialdehyde
MDS-UPDRS	Movement Disorder Society Unified Parkinson’s Disease Rating Scale
NMSS	Non-Motor Symptoms Scale
NMSS	Non-Motor Symptoms Scale for PD
NfL	neurofilament light-chain protein
OR	odds ratio
PAC-QOL	patient assessment of constipation
PAC-SYM	patient assessment of constipation symptoms
PD	Parkinson’s disease
PDQ-39	Parkinson’s disease questionnaire
PPIs	proton pump inhibitors
QID	quater in die, ‘four times a day’
RCT	randomized controlled trial
SBM	spontaneous bowel movements
SCFA	short-chain fatty acid
SIBO	small-intestinal bacterial overgrowth
SMD	standard mean difference
TGF	transforming growth factor
TID	ter in die, ‘three times a day’
TLR	toll-like receptor
TNF	tumor necrosis factor
UBT	urea breath test
VacA	vacuolating cytotoxin A