Volume 153, Issue 6, Pages 1504-1516.e2 (December 2017) Increased Tryptophan Metabolism Is Associated With Activity of Inflammatory Bowel Diseases  Susanna Nikolaus, Berenice Schulte, Natalie Al-Massad, Florian Thieme, Dominik M. Schulte, Johannes Bethge, Ateequr Rehman, Florian Tran, Konrad Aden, Robert Häsler, Natalie Moll, Gregor Schütze, Markus J. Schwarz, Georg H. Waetzig, Philip Rosenstiel, Michael Krawczak, Silke Szymczak, Stefan Schreiber  Gastroenterology  Volume 153, Issue 6, Pages 1504-1516.e2 (December 2017) DOI: 10.1053/j.gastro.2017.08.028 Copyright © 2017 AGA Institute Terms and Conditions

Figure 1 TRP levels in active and inactive disease in comparison with healthy controls. TRP serum levels were highly associated with active disease (“active disease” defined as CRP or symptomatic activity). For a separation between biochemical and symptomatic definition of disease activity see Supplementary Figure 3. CD: control vs inactive CD: n = 490, P = .016; control vs active CD: n = 511, P < .001; active vs inactive CD n = 114, P = .01; UC: control vs inactive UC: n = 428, P = .772; control vs active UC: n = 420, P < .001; active vs inactive UC: n = 65, P = .068). Data are presented as box plots. Statistical analysis: Bootstrap analysis using all active and inactive time points per patient; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. Gastroenterology 2017 153, 1504-1516.e2DOI: (10.1053/j.gastro.2017.08.028) Copyright © 2017 AGA Institute Terms and Conditions

Figure 2 Regulation of mRNA levels of TDO2, SLC6A19/B0AT1, and IDO1 in the colonic mucosa of patients with active UC or CD. Relative messenger RNA expression of TDO2 (A), BOAT1 (B), and IDO1 (C) in IBD patients with active (a) and nonactive (na) disease and control individuals (n = 60 CD patients; n = 60 UC patients; n = 45 disease control [DC] patients with non-IBD intestinal inflammation; n = 30 hospitalized normals [HN] without pathologic findings) are shown. Expression levels were determined via TaqMan real-time polymerase chain reaction, normalized to β-actin using the standard curve method. Box plots represent 25th, 50th, and 75th percentile, while whiskers show the 5th and 95th percentile. Stars indicate significant differences as determined by the Mann-Whitney U test (−, not significant; ∗P ≤ 5 × 10−2; ∗∗P ≤ 5 × 10−4; ∗∗∗P ≤ 5 × 10−6). Gastroenterology 2017 153, 1504-1516.e2DOI: (10.1053/j.gastro.2017.08.028) Copyright © 2017 AGA Institute Terms and Conditions

Figure 3 High activity of the kynurenine pathway in active and inactive CD and UC. In CD (n = 81) and UC (n = 67), TRP was extensively metabolized via KYN to QUI. The KYN/TRP ratio indicates an enhanced degradation of TRP (CD: active vs control P = 6.2e−7, inactive vs control P = .024, active vs inactive P = 6.1e−6; UC: active vs control P = 6e−6, inactive vs control P = .026, active vs inactive P = .1). QUI serum levels were strongly increased (CD: active vs control P = 7.7e−28, inactive vs control P = 8.4e−25, active vs inactive P = .051; UC: active vs control P = 7.5e−17, inactive vs control P = 2.3e−14, active vs inactive P = .16). Anthranilic acid was only increased in active CD (CD: active vs control P = .0019, inactive vs control P = .75, active vs inactive P = .5; UC: active vs control P = .24, inactive vs control P = .14, active vs inactive P = .049). Kynurenic acid (KYA) serum levels (CD: active vs control P = 9.4e−6, inactive vs control P = .00054, active vs inactive P = .81; UC: active vs control P = .66, inactive vs control P = .69, active vs inactive P = .11) and PIC serum levels were reduced only in CD (CD: active vs control P = 2e−7, inactive vs control P = 1.8e−7, active vs inactive P = .39; UC: active vs control P = .1, inactive vs control P = .12, active vs inactive P = 1). Xanthurenic acid (XAN) (CD: inactive vs control P = .0015) and quinaldic acid (QUD) (UC: active vs control 0.042) seemed to be less regulated. IL22 levels (CD: n = 17; UC: n = 11; a subpopulation of the metabolic pathway cohort) were significantly elevated in active IBD (CD: P = .012, IL22/TRP ratio: P = .0003; UC: P = .4, IL22/TRP ratio: P = .0085). ANT, anthranilic acid; ATP, adenosine triphosphate; 3-HAA, 3-hydroxyanthranilic acid; 3-HK, 3-hydroxykynurenine. Data are presented as box plots. Statistical analysis: Wilcoxon rank sum tests (active or inactive vs controls) and signed rank tests (active vs inactive) using the most extreme active and inactive time points per patient, as paired analysis. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. Gastroenterology 2017 153, 1504-1516.e2DOI: (10.1053/j.gastro.2017.08.028) Copyright © 2017 AGA Institute Terms and Conditions

Figure 4 Restitution of TRP levels in responders to infliximab. (A) Analysis of responders to infliximab. Data from CD and UC have been combined. IBD (n = 46): 2 wk: P = .00024; 6 wk: P = .0037; 14 wk: P = .011; 6 mo: P = .00068. CD (n = 31): 2 wk: P = .00012; 6 wk: P = .041; 14 wk: P = .009; 6 mo: P = .006. UC (n = 15): 2 wk: P = .130; 6 wk: P = .042; 14 wk: P = .463; 6 mo: P = .057; data not shown. (B) Combined analysis of IBD nonresponders to therapy with infliximab (n = 17; 2 wk: P = .018; 6 wk: P = .249; 14 wk: P = .297; 6 mo: P = .655). (C) No change in TRP levels was seen during therapy with vedolizumab as first-line biologic therapy (n = 25). Data are presented as box plots. Statistical analysis: paired t tests comparing each time point with baseline; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. Gastroenterology 2017 153, 1504-1516.e2DOI: (10.1053/j.gastro.2017.08.028) Copyright © 2017 AGA Institute Terms and Conditions

Figure 5 Low TRP levels precede intestinal resection. Receiver operator characteristic curves for evaluation of TRP as a biomarker for prediction of surgery within (A) 100 and (B) 200 days (100 days: P = 3.19 × 10−3, n = 27; 200 days: P = 5.6 × 10−3, n = 28) are shown. In addition, a dichotomized version of TRP (0: values below the first quartile, 1: values above the third quartile) is analyzed for prediction (sensitivity and specificity are denoted with a cross). Evaluation of TRP levels for prediction resulted in an area under the curve (AUC) of 0.76 (95% CI, 0.63−0.89) and 0.73 (95% CI, 0.59−0.87). Surgeries were ileocoecal or colonic resections, new ileostomies, and proctocolectomies. Gastroenterology 2017 153, 1504-1516.e2DOI: (10.1053/j.gastro.2017.08.028) Copyright © 2017 AGA Institute Terms and Conditions