Niklas Nyström: Metabolomic features and viral infections in paediatric inflammatory bowel disease

Abstract

Background: Up to 25% of patients with inflammatory bowel disease have a paediatric onset (PIBD). The pathophysiological processes underlying PIBD are complex and largely unknown.  

Aims: To investigate a hypothesized role for human enterovirus B (HEV-B) in Crohn’s disease (CD) (I). To map and compare the mucosal and plasma metabolomes in new-onset PIBD patients and controls (II). To search for a new blood-based diagnostic biomarker for PIBD (III). To investigate the effect of exclusive enteral nutrition (EEN) treatment on the mucosal and plasma metabolomes in CD patients (IV). 

Methods: Immunohistochemistry and chromogen in situ hybridisation were used to search for HEV-B in surgical specimens from patients who had undergone surgery for stricturing ileocecal CD, and from volvulus patients as controls. Ultra-high-performance liquid chromatography mass spectrometry were used on biopsies and plasma from patients in the Uppsala PIBD inception cohort for metabolomic (II and IV) and lipidomic analyses (III). Patients were stratified by phenotypic subtypes and treatment responses. Symptomatic patients without PIBD were used as non-IBD controls. In Study III, two other independent PIBD inception cohorts were used for validation and confirmation. 

Results: I: HEV-B was detected in epithelial cells and neuronal ganglia of the enteric nervous system, and the specific cellular Coxsackie and adenovirus receptor (CAR) was expressed in both the intestinal epithelium and the enteric nervous system. II: Alterations in two metabolic compound classes were seen: decreased levels of lysophospholipids in inflamed ileum of CD patients and altered levels of sphingolipids in inflamed ileum and colon in both CD and ulcerative colitis, as compared with non-IBD controls. III: Discovery, validation and confirmation in three independent PIBD inception cohorts of a blood-based diagnostic two-lipid signature of PIBD. IV: A generalised downregulation of the non-inflamed ileal lipid metabolism after successful remission induction with EEN, as compared with baseline, and also as compared with non-IBD controls. Reduction of several lysophospholipids was a characteristic feature of the post-EEN ileal metabolome.

Conclusions: The demonstrated presence of HEV-B supports, but does not confirm, its hypothesised role in CD. The CD-associated downregulation of mucosal metabolism both at disease onset and after successful EEN-induced inflammation resolution indicates a central role for the ileal mucosal lipid metabolism in CD, including lysophospholipids. The blood-based two-lipid signature has the potential of becoming a diagnostic tool in the clinical work-up of suspected PIBD.