AD	Alzheimer’s disease
BCAA	branched chain amino acid
BMI	body-mass-index
CE-FTMS	capillary electrophoresis Fourier transform mass spectrometry
CSF	cerebrospinal fluid
FT-ICR-MS	Fourier transform ion cyclotron resonance mass spectrometry
GC-MS	gas chromatography mass spectrometry
LC-MS	liquid chromatography mass spectrometry
LC-MS/MS	liquid chromatography tandem mass spectrometry
MCI	mild cognitive impairment
MRI	magnetic resonance imaging
NMR	nuclear magnetic resonance
PD	Parkinson’s disease
PET	positron emission tomography
SCFA	short-chain fatty acid
TMAO	trimethylamine-N-oxide