Table 2.

Differential Serum Metabolites between CRC Patients and Healthy Controls in the Learning Group

no.	metabolites	metabolic pathway	FCc	P-valued	VIPe
1	5-hydroxytryptaminea	tryptophan metabolism	−23.76	7.96 × 10−21	3.45
2	LysoPC(14:0)	phospholipid metabolism	−3.58	1.78 × 10−18	2.71
3	LysoPC(16:1(9Z))	phospholipid metabolism	−2.65	3.77 × 10−18	2.60
4	2-oxobutanoic acid	glutathione metabolism	3.92	4.45 × 10−16	1.92
5	fumaratea	tca cycle	−2.30	1.24 × 10−15	2.51
6	aspartatea	urea cycle	−1.76	6.39 × 10−15	2.42
7	β-hydroxybutyratea	fatty acid metabolism	8.59	9.87 × 10−15	1.63
8	4-hydroxystyrene	others	−8.44	3.05 × 10−14	1.63
9	phenylalaninea,b	phenylalanine metabolism	−1.35	1.30 × 10−13	1.98
10	tetrahydrogestrinone	others	4.18	7.16 × 10−13	1.84
11	LysoPC(20:0)	phospholipid metabolism	−2.32	1.33 × 10−12	2.23
12	glycerola	fatty acid metabolism	2.61	3.14 × 10−12	2.22
13	glyceric acida	glucose metabolism	−1.55	3.37 × 10−12	2.30
14	cis-aconitatea	TCA cycle	−2.60	3.37 × 10−12	1.57
15	tryptophana,b	tryptophan metabolism	−1.45	7.31 × 10−12	2.17
16	phenol	tyrosine metabolism	−2.85	9.33 × 10−12	1.59
17	octenedioate	fatty acid metabolism	34.75	1.37 × 10−11	2.40
18	threitola	carbohydrates metabolism	−1.30	1.74 × 10−11	1.85
19	indoleacrylic acid	gut flora metabolism	−1.44	3.55 × 10−11	2.21
20	sphinganine	phospholipid metabolism	4.08	6.29 × 10−11	1.35
21	2-hydroxybutyric acida,b	glutathione metabolism	2.09	7.43 × 10−11	2.04
22	LPA(18:0/0:0)	others	−1.65	1.14 × 10−10	2.20
23	indoxyl sulfate	tryptophan metabolism	−2.85	3.46 × 10−10	1.79
24	histidinea,b	histidine metabolism	−1.28	5.82 × 10−9	1.91
25	2-aminobutanoic acida	glutathione metabolism	1.61	1.29 × 10−8	1.86
26	alaninea,b	alanine, aspartate, and glutamate metabolism	−1.39	1.68 × 10−8	1.66
27	6-phosphogluconic acida,b	pentose phosphate pathway	−1.42	6.05 × 10−8	1.68
28	ribitol	nucleic acid metabolism	−1.49	8.45 × 10−8	1.62
29	4-hydroxyprolinea	proline metabolism	−1.8	3.18 × 10−7	1.67
30	benzaldehyde	others	−1.38	6.12 × 10−7	1.33
31	hydroquinonea	tyrosine metabolism	−4.87	1.25 × 10−6	1.55
32	ureaa	urea cycle	−1.37	1.65 × 10−6	1.58
33	trihydroxycoprostanoic acid	others	−3.25	2.76 × 10−6	1.49
34	cholic acida	bile acid metabolism	−4.27	2.90 × 10−6	1.04
35	LysoPC(P-18:1(9Z))	phospholipid metabolism	−3.62	3.53 × 10−6	1.76
36	ubiquinone	oxidative phosphorylation	−1.59	4.07 × 10−6	1.38
37	3,4,5-trimethoxycinnamic acid	others	−1.57	4.59 × 10−6	1.20
38	ornithinea	urea cycle	−1.27	5.43 × 10−6	1.20
39	indoxyl	tryptophan metabolism	−2.61	5.83 × 10−6	1.20
40	trimethylamine N-oxidea	choline metabolism	−3.39	6.71 × 10−6	1.01
41	oleamidea,b	fatty acid metabolism	2.55	7.91 × 10−6	1.68
42	oleic acida,b	fatty acid metabolism	1.55	9.31 × 10−6	1.58
43	inositol	carbohydrates metabolism	−1.28	9.31 × 10−6	1.40
44	chenodeoxycholic acida	bile acid metabolism	−3.54	1.17 × 10−5	1.10
45	serinea	glycine, serine, and threonine metabolism	−1.18	1.41 × 10−5	1.43
46	methioninea,b	cysteine and methionine metabolism	−1.19	1.69 × 10−5	1.30
47	asparaginea	alanine, aspartate, and glutamate metabolism	−1.22	2.52 × 10−5	1.46
48	2-hydroxy-3-methylpentanoic acid	L-isoleucine metabolism	−8.96	3.21 × 10−5	1.63
49	erythrotetrofuranose	carbohydrates metabolism	−1.32	6.67 × 10−5	1.32
50	carnitine (18:1)	fatty acid metabolism	1.23	7.40 × 10−5	1.25
51	linolic acida	fatty acid metabolism	1.43	7.56 × 10−5	1.34
52	creatininea,b	arginine and proline metabolism	1.30	8.75 × 10−5	1.43
53	β-aspartylserine	glycine, serine, and threonine metabolism	−1.81	9.12 × 10−5	1.20
54	12a-hydroxy-3-oxocholadienic acid	bile acid metabolism	−2.14	1.05 × 10−4	1.18
55	CPA(18:0/0:0)	phospholipid metabolism	2.54	1.35 × 10−4	1.25
56	acetyl carnitinea	fatty acid metabolism	1.30	1.82 × 10−4	1.11
57	allantoic acid	others	−1.20	2.05 × 10−4	1.07
58	elaidic acida	fatty acid metabolism	1.42	2.97 × 10−4	1.33
59	decanoyl carnitine	fatty acid metabolism	−1.39	3.88 × 10−4	1.01
60	xanthosine	purine nucleotide synthetic	27.12	3.95 × 10−4	1.34
61	glutamatea,b	glutathione metabolism	−1.29	4.95 × 10−4	1.02
62	adeninea	purine nucleotide synthetic	1.17	5.14 × 10−4	1.11
63	α-aminoadipic acid	lysine metabolism	−1.93	7.70 × 10−4	1.20
64	pyruvatea	TCA cycle	1.30	1.10 × 10−3	1.15
65	3-oxodecanoic acid	fatty acid metabolism	1.37	1.53 × 10−3	1.09
66	cystinea	cysteine and methionine metabolism	1.12	2.38 × 10−3	1.05
67	palmitic acida	fatty acid metabolism	1.24	2.46 × 10−3	1.09
68	allyl isothiocyanate	others	1.15	2.85 × 10−3	1.10
69	N-acetyl-5-hydroxytryptamine	tryptophan metabolism	−2.49	3.87 × 10−3	1.01
70	proline betaine	others	4.46	7.96 × 10−3	1.30
71	allisoleucine	valine, leucine, and isoleucine degradation	1.29	1.08 × 10−2	1.06
72	glycolaldehyde	vitamin B6 metabolism	2.25	2.36 × 10−2	1.11

^aMetabolites validated by reference standards.

^bMetabolites that can be identified by GC–TOFMS and UPLC–QTOFMS.

^cThe fold change (FC) was calculated by the average value of CRC group to that of control group. FC with a value larger than 1.0 indicates a significantly higher level of the serum metabolite in patients while a FC value lower than 1.0 indicates a lower level, compared to healthy controls.

^dP values were calculated from a nonparametric Mann–Whitney U test.

^eVariable importance in the projection (VIP) was obtained from OPLS-DA with a threshold of 1.0.