Rapid fecal lipidome profiling in inflammatory bowel disease: A novel approach for exploratory disease molecular characterization and therapeutic monitoring.

Characterizing fecal molecular perturbations associated with diagnosis and treatment may facilitate the development of novel non-invasive biomarkers for better clinical management of inflammatory bowel disease (IBD). Here, we employed rapid untargeted lipidomics, combined with various lipid data mining methods, to investigate alterations in the fecal lipidome associated with IBD, disease activity, and body mass index (BMI) levels. Machine learning modeling with a robust nested cross-validation procedure was employed to identify fecal-based potential biomarkers across three clinically meaningful scenarios. A total of 719 fecal lipids of 65 treated IBD patients were annotated, with lipid alterations analyzed at different levels, from subclasses to individual species. Univariate analysis revealed significant differences in the abundances of ceramides, fatty acids, triglycerides (TGs), ether-linked diacylglycerols (DG(O-)), and microbiota-associated lipids - fatty acid esters of hydroxy fatty acids (FAHFAs), between ulcerative colitis (UC) and Crohn's disease (CD). Significant alterations in lipid-related gene functions between UC and CD were linked to the sphingolipid signaling pathway, ether lipid metabolism, sphingolipid metabolism, and cholesterol metabolism. Interestingly, no significant fecal lipidome alterations were associated with disease activity, fecal calprotectin levels, or BMI. Partial least squares-discriminant analysis and support vector machine models achieved satisfactory classification performance, with an area under the receiving operating characteristic curve ≥ 0.80. FAHFA, TG, and DG(O-) were consistently identified as the top potential predictors to differentiate between UC and CD. Altogether, our findings provide better insights into the lipidome of IBD undertreatment and suggest that fecal lipids are potential non-invasive biomarkers to aid in IBD diagnosis.