Alteration of fecal tryptophan metabolism correlates with shifted microbiota and may be involved in pathogenesis of colorectal cancer

Table 1 Demographic and clinical information of participants included in the study

Feature	HCs (n = 38)	ADA patients (n = 33)	CRC patients (n = 46)	P value
Age (yr)	56.85 ± 10.99	61.18 ± 8.53	63.63 ± 11.39	0.095
Gender (male:female)	24:14	23:10	32:14	0.799
BMI (kg/m2)	23.86 ± 3.84	24.817 ± 3.31	23.66 ± 2.88	0.676
Smoking history (%)	10 (26.3)	15 (45.5)	17 (37.0)	0.241
Drinking history (%)	14 (36.8)	9 (27.3)	12 (26.1)	0.522
CRC of FDRs (%)	6 (21.4)	8 (24.2)	8 (17.4)	0.753

The data are presented as the mean ± SD. HC: Healthy control; ADA: Colorectal adenoma; CRC: Colorectal cancer; BMI: Body mass index; FDR: False discovery rate.

Table 2 Concentrations of tryptophan and tryptophan metabolites in patients and healthy controls

Metabolite (nmol/L)	Controls (n = 28)	ADA patients (n = 24)	CRC patients (n = 39)	Intergroup comparisons (P value)
				HC/ADA	HC/CRC	ADA/CRC
Trp	196.67 (125.10, 353.30)	289.46 (206.2, 393.72)	241.88 (165.98, 429.16)	0.081	0.118	0.611
KYN	0.81 (0.64, 1.57)	0.94 (0.66, 2.25)	1.51 (0.70, 3.46)	0.627	0.036	0.140
Indole	252.00 (170.00, 545.00)	251.00 (66.50, 366.75)	356.00 (128.50, 729.25)	0.213	0.878	0.170
Skatole	210.00 (172.00, 223.00)	137.00 (115.00, 206.00)	231.00 (147.50, 265.50)	0.111	0.495	0.019
IAA	6.56 (1.25, 20.59)	6.63 (3.35, 18.82)	7.61 (1.85, 16.1)	0.401	0.943	0.876
IPA	10.67 (6.36, 15.48)	7.75 (4.55, 10.38)	7.65 (4.19, 13.11)	0.025	0.025	0.348
IALD	8.00 (4.25 15.50)	19.50 (8.25, 31.75)	37.00 (13.00, 63.00)	0.044	0	0.024
I3CA	1.13 (0.81, 1.71)	1.10 (0.74, 2.11)	3.64 (1.79, 8.15)	0.971	0.011	0.028
Indoles	428.24 (276.45, 963.95)	325.50 (179.82, 504.33)	547.87 (247.97, 823.64)	0.100	0.955	0.044
Indoles/Trp ratio	2.46 (1.25, 4.10)	1.48 (0.58, 1.97)	1.34 (0.70, 2.63)	0.003	0.029	0.413
KYN/Trp ratio (× 10-3)	5.23 (1.86, 7.99)	3.73 (1.99, 11.39)	7.39 (4.12, 11.72)	0.845	0.032	0.105

The data are presented as the median (Q1, Q3). HC: Healthy control; ADA: Colorectal adenoma; CRC: Colorectal cancer; BMI: Body mass index; Trp: Tryptophan; KYN: Kynurenine; IAA: Indole-3-acid-acetic; IPA: Indole-3-propionic acid; IALD: Indole-3-aldehyde; I3CA: Indole-3-carboxylic acid.