TABLE 4.

Significant metabolic pathways involved in the five neurodegenerative diseases.

Traits	Metabolites pathway	Involved metabolites	P-value	Database
AD	Urea cycle	Urea, L-Glutamine	0.0364	SMPDB
AD	Arginine biosynthesis	Urea, L-Glutamine	0.0040	KEGG
AD	Purine metabolism	Guanosine, L-Glutamine	0.0093	KEGG
AD	D-Glutamine and D-glutamate metabolism	L-Glutamine	0.0421	KEGG
ALS	Phenylalanine, tyrosine and tryptophan biosynthesis	L-Phenylalanine	0.0459	KEGG
FTD	Carnitine synthesis	L-Lysine, Oxoglutaric acid	0.0441	SMPDB
MS	Phenylalanine, tyrosine and tryptophan biosynthesis	L-Tyrosine	0.0232	KEGG

AD, Alzheimer’s disease; ALS, amyotrophic lateral sclerosis; FTD, frontotemporal dementia; MS, multiple sclerosis; KEGG, Kyoto encyclopedia of genes and genomes; SMPDB, small molecule pathway database.