Table 2. Key urinary metabolites responsible for the discrimination of MDD patients and HCs.

Metabolites	VIP	p-value	Adjusted p-value	Fold change	Platform
Young
Homovanillic acid	1.15	0.014	0.045	1.76	GC-MS
L-Leucine	1.17	0.014	0.046	1.65	GC-MS
4-Deoxythreonic acid	1.06	8.49E-06	0.00018	1.64	GC-MS
4-Deoxyerythronic acid	1.09	0.000075	0.0011	1.61	GC-MS
Methylmalonic acid	1.04	0.0039	0.015	1.54	GC-MS
L-Cysteine	1.11	0.0024	0.011	1.44	GC-MS
Formic acid	1.23	0.005	0.019	0.68	NMR
Azelaic acid	1.06	0.000057	0.001	0.17	GC-MS
Young/Middle-aged
1-Methylinosine	1.22/1.31	0.00034/0.00025	0.0027/0.0013	2.15/1.99	GC-MS
Citric acid	1.23/1.23	0.00027/0.002	0.002/0.0072	0.68/0.72	NMR
Ethanolamine	1.29/1.24	0.011/0.00098	0.038/0.0043	2.02/1.89	GC-MS
Hypoxanthine	1.22/1.64	2.79E-10/1.09E-08	2.45E-07/4.83E-06	3.79/3.59	GC
Indoxyl sulfate	1.29/1.34	0.00011/0.000039	0.0012/0.00028	2.06/1.76	GC
L-Tyrosine	1.17/1.56	2.96E-06/0.0015	8.6E-05/0.006	2.39/2.95	GC
Oxoglutaric acid	1.74/1.06	0.008/4.97E-07	0.03/7.28E-06	0.75/0.86	NMR
Pseudouridine	1.21/1.48	0.00013/0.00023	0.0013/0.0012	2.2/2.29	GC
Quinolinic acid	1.15/1.41	0.00054/0.0034	0.0036/0.011	1.94/1.96	GC
Uracil	1.24/1.39	0.0026/0.0023	0.011/0.0077	1.9/1.71	GC
Middle-aged
N-Methylnicotinamide	1.83	0.001	0.0042	2.08	NMR
L-Phenylalanine	1.32	0.01	0.028	1.52	GC-MS
L-Lactic acid	1.21	1.12E-06	0.000014	0.8	NMR
Succinic acid	1.05	0.000015	0.00015	0.86	NMR
3-Hydroxyphenylacetic acid	1.03	0.0046	0.013	1.94	GC-MS

^ap-value was obtained from the nonparametric Mann-Whitney U test.

^badjusted p-value was obtained using Benjamini and Hochberg False Discovery Rate.

^cvalues less than 1.0 indicated significantly lower levels in MDD patients; values higher than 1.0 indicated significantly higher levels in MDD patients.