Abstract
Acute graft-versus-host disease (GVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Reliable early, noninvasive biomarkers for GVHD prediction remain limited. We conducted targeted fecal metabolomic profiling using liquid chromatography-tandem mass spectrometry in 77 allo-HSCT recipients at two time points: before conditioning (S1) and immediately after conditioning but prior to donor T-cell engraftment (S2). We assessed changes in metabolite profiles and their association with subsequent GVHD development. A multivariate logistic regression model and receiver-operating characteristic analysis were used to evaluate predictive performance. Conditioning induced significant alterations in neurotransmitters, bile acids, purine metabolism, tryptophan pathways, and phospholipase A2 (PLA2) activity. Post-conditioning, patients who developed GVHD showed elevated xanthine synthesis, reduced indoleamine 2,3-dioxygenase activity, and increased PLA2 metabolites. Reflecting the metabolic balance between anti-inflammatory omega-3 and pro-inflammatory omega-6 fatty acids, the eicosapentaenoic acid to arachidonic acid and docosahexaenoic acid to arachidonic acid ratios were consistently higher in the GVHD group. A five-metabolite-ratio panel demonstrated moderate discriminatory ability (area under the curve: 0.752, 95% confidence interval: 0.584-0.909). Early fecal metabolomic profiling after conditioning may capture metabolic patterns associated with later GVHD risk. This noninvasive approach shows potential to aid early risk stratification and improve preventative strategies in allo-HSCT patients.