P237 Proteomic analyses do not reveal subclinical inflammation in fatigued patients with quiescent Inflammatory Bowel Disease
Bourgonje, A.R.(1);Wichers, S.J.(1);Hu, S.(1,2);van Dullemen, H.M.(1);Visschedijk, M.C.(1);Faber, K.N.(1);Festen, E.A.M.(1);Dijkstra, G.(1);Samsom, J.N.(3);Weersma, R.K.(1);Spekhorst, L.M.(1,4);
(1)University of Groningen- University Medical Center Groningen, Gastroenterology and Hepatology, Groningen, The Netherlands;(2)University of Groningen- University Medical Center Groningen, Genetics, Groningen, The Netherlands;(3)Erasmus University Medical Center, Pediatrics- Division of Gastroenterology, Groningen, The Netherlands;(4)Medisch Spectrum Twente, Gastroenterology and Hepatology, Enschede, The Netherlands;
Background
Fatigue is a common and clinically challenging symptom in patients with inflammatory bowel diseases (IBD). While fatigue occurs most often in patients with active disease, up to 50% of patients with quiescent disease still report significant fatigue of unknown aetiology. Here, we aimed to investigate whether fatigue in patients with quiescent IBD is reflected by circulating inflammatory proteins, that in turn might reflect ongoing subclinical inflammation.
Methods
Ninety-two (92) different inflammation-related proteins were measured in plasma of 350 patients with quiescent IBD (188 Crohn’s disease [CD]; 162 ulcerative colitis [UC]). Quiescent IBD was defined as clinical (Harvey-Bradshaw Index [HBI] <5 or Simple Clinical Colitis Activity Index [SCCAI] <2.5) and biochemical remission (C-reactive protein [CRP] <5 mg/L) at time of sampling. Fatigue severity was assessed on a visual analogue scale (VAS).
Results
None of the analysed plasma proteins were differentially abundant between mildly (1st quartile, Q1) or severely (4th quartile, Q4) fatigued patients under a false discovery rate of 10%. Considering nominal significance (P<0.05), however, leukemia inhibitory factor receptor (LIF-R) concentrations were inversely associated with severe fatigue, also after adjustment for confounding factors (P <0.05) (Figure 1). Although solely LIF-R showed weak ability to discriminate between mild (Q1) and severe (Q4) fatigue (area under the curve [AUC]=0.61, 95% CI: 0.53-0.69, P<0.05), a combined set of the top seven (7) fatigue-associated proteins (LIF-R, vascular endothelial growth factor-A [VEGF-A], glial-derived neurotrophic factor [GDNF], interleukin-20 receptor subunit alpha [IL-20RA], Delta and Notch-like epidermal growth factor-related receptor [DNER], T-cell surface glycoprotein CD5 [CD5], and extracellular newly identified receptor for advanced glycation end-products binding protein [EN-RAGE], also known as protein S100-A12, all P<0.10) was observed to have reasonable discriminative performance (AUC=0.82 [95% CI: 0.74-0.91], P<0.01). 
Conclusion
Fatigue in patients with IBD is not clearly reflected by distinct circulating inflammatory protein signatures, which suggests that subclinical immune activation as defined by the studied panel of inflammatory proteins could not be detected. Reduced shedding of the LIF-R protein could be related to fatigue in IBD through modification of the oncostatin-M (OSM) signaling pathway, or through induction of pro-inflammatory phenotypes of T-cells, macrophages, or neural cells. Future studies are warranted to investigate other proteomic or metabolic markers that may accurately reflect fatigue in quiescent IBD, which might represent alternative pathophysiological pathways.