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

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.