Metabolomic analysis of the interleukin-10-deficient mouse model of Crohn's disease

Abstract

Crohn’s disease is an inflammatory disorder of the bowel, arising from the dysregulation of intestinal mucosal immunity. The interleukin-10-deficient (IL10-/-) mouse develops intestinal inflammation with similar characteristics to Crohn’s disease, due to the loss of immune tolerance towards intestinal microbiota. Metabolomic analysis is the study of small molecule metabolites, involving the measurement of large numbers of metabolites in biological samples. The aim of the research was to study the urinary metabolite profile of IL10-/- mice by gas chromatography-mass spectrometry metabolomic analysis. A metabolite profile of intestinal inflammation, consisting of 15 metabolites, was discovered by comparing the urinary metabolite profiles of IL10-/- and wildtype C57BL/6 mice. Xanthurenic acid and fucose were identified as the main urinary metabolites associated with the early stage of intestinal inflammation. Their levels were increased in IL10-/- mice relative to wildtype. Xanthurenic acid levels were attributed to increased tryptophan catabolism which produces kynurenine metabolites that may induce immune tolerance of T-cells towards intestinal microbiota. Plasma levels of kynurenine and 3-hydroxykynurenine were confirmed to be elevated in IL10-/- mice. The increased fucose levels may be due to abnormal fucosylation of plasma or intestinal mucosal proteins involved in leukocyte trafficking. Comparisons of the urinary metabolite profiles of IL10-/- and wildtype mice also revealed eleven metabolite differences that were unaffected by inflammation severity in IL10-/- mice. The main metabolites were glutaric acid, 2-hydroxyglutaric acid and 2-hydroxyadipic acid, which were decreased in IL10-/- mice. These eleven metabolite differences may be associated with residual genes from embryonic stem cells of the 129P2 mouse strain used to create the IL10-/- mouse, or novel functions of IL10 that are unrelated to inflammation. The metabolite profile of inflammation was not altered in IL10-/- mice fed with kiwifruit extracts, consistent with other measures of inflammation which showed that intestinal inflammation was not attenuated by the dietary intervention. The urinary levels of some kiwifruit metabolites differed between IL10-/- and wildtype mice, suggesting differences in absorption or intestinal microbial metabolism of these metabolites. Overall, the research demonstrates that metabolomic analysis of IL10-/- mice can identify potential biomarkers of intestinal inflammation and provide new insights into the metabolic effects of IL10-deficiency.