Introduction
Chronic fatigue is a debilitating symptom and has major impacts on the quality of life of patients with chronic inflammatory conditions. In IBD, an estimated 50% of patients suffer from persistent fatigue despite successful treatment of intestinal inflammation. During active disease flares, this number jumps to 80% (Borren et al. 2018). Tryptophan metabolites are not only associated with disease activity in UC and CD, but also with chronic fatigue (Kavyani et al. 2022). Thus, our aims are (1) to characterize the relationship between fatigue and tryptophan derivatives and (2) to understand the metabolic dynamics arising when fatigue symptoms improve following therapeutic intervention.
Aims & Methods
In a prospective open label cohort of patients with moderate-to-severe Crohn’s disease (CD, n = 71) and ulcerative colitis (UC, n = 94) assigned to biologics therapy or JAK inhibitors, fatigue was assessed by the fatigue subscale of the Functional Assessment of the Chronic Illness Therapy – Fatigue (FACIT-F) questionnaire at therapy induction and 2 and 14 weeks thereafter. A FACIT-F score of <30.1 was considered severe fatigue while a score of >40 was considered no relevant fatigue. Clinical response at week 14 was defined as Crohn’s Disease Activity Index (CDAI) <150 and reduction of Partial Mayo Clinical Score (PMCS) >50% vs. baseline, respectively. We used targeted mass spectrometry to quantify the levels of 13 tryptophan derivatives and neopterin in a subset of patient serum in the weeks following therapy induction (at 0, 2, and 14 weeks, n = 120 individuals).
Results
Half of the recruited patients had severe fatigue at baseline (50.3%). Of the 120 patients who reached week 14 and had FACIT-F scores available, severe fatigue was experienced by 45.9% of the patients who did not respond to therapy and the rate was reduced to 13.2% in therapy responders. We found 8 metabolites positively associated with FACIT-F: tryptophan, kynurenic acid, kynurenine, picolinic acid, xanthurenic acid, serotonin, indole-3-proprionic acid, and quinaldic acid, while neopterin was negatively associated (FDR < 0.05). Four of these metabolites changed dynamically as a function of the extent of fatigue improvement: tryptophan, kynurenine, xanthurenic acid, and serotonin (FDR < 0.05). In all cases, the rate of change of these metabolites increased as a function of fatigue improvement.
Conclusion
Fatigue is linked to a diverse array of tryptophan metabolites. Notably, all of the significantly associated tryptophan derivatives were positively associated with FACIT-F, meaning that as fatigue symptoms improve, tryptophan metabolite levels increase. Many of these metabolites have previously been linked to symptom severity in IBD: for example, tryptophan, kynurenic acid and xanthurenic acid all tend to increase with symptom alleviation (Nikolaus et al. 2017, Michaudel et al. 2022). While the kynurenine-to-tryptophan ratio is elevated in active IBD (Nikolaus et al. 2017), this ratio did not convey a specific, fatigue-related signature. Considering that some patients continue to suffer from persistent fatigue even during disease quiescence, further work is needed to disentangle the impact of tryptophan metabolism on therapy response from its role on fatigue improvement.
Disclosure
F. Tran receives scientific funding from Sanofi, received consulting fee's from LEK Consulting and speaker's fees from Lilly, Janssen, Falk, Abbvie, Celltrion, onkowissen.de, CED Service GmbH. S. Schreiber reports consulting fees from Abbvie, Arena, BMS, Biogen, Celltrion, Celgene, IMAB, Gilead, MSD, Mylan, Pfizer, Fresenius, Janssen, Takeda, Theravance, Prevention Bio, Protagonist and Falk.