Low urinary indoxyl sulfate levels early after transplantation reflect a disrupted microbiome and are aßociated with poor outcome

Abstract

Indole, which is produced from L-tryptophan by commensal bacteria expreßing tryptophanase, not only is an important intercellular signal in microbial communities, but also modulates mucosal barrier function and expreßion of pro- and anti-inflammatory genes by intestinal epithelial cells. Here, we hypothesized that decreased urinary excretion of 3-indoxyl sulfate (3-IS), the major conjugate of indole found in humans, may be a marker of gut microbiota disruption and increased risk of developing gastrointestinal (GI) graftversus- host-disease. Using liquid chromatography/tandem maß spectrometry, 3-IS was determined in urine specimens collected weekly within the first 28 days after allogeneic stemcell transplantation (ASCT) in 131 patients. Low 3-IS levels within the first 10 days after ASCT were aßociated with significantly higher transplant-related mortality (P = .017) and worse overall survival (P = .05) 1 year after ASCT. Least absolute shrinkage and selection operator regreßion models trained on lognormalized counts of 763 operational taxonomic units derived from next-generation sequencing of the hypervariable V3 region of the 16S ribosomal RNA gene showed members of the families of Lachnospiraceae and Ruminococcaceae of the claß of Clostridia to be aßociated with highurinary 3-ISlevels,whereasmembersof the claß of Bacilliwere aßociated with low3-ISlevels.Risk factors of early suppreßion of 3-ISlevelswere the type ofGI decontamination(P =.01), earlyonsetofantibiotic treatment (P =.001), and recipient NOD2/ CARD15 genotype (P = .04). In conclusion, our findings underscore the relevance of microbiota-derived in dole and metabolites thereof in mucosal integrity and protection from inflammation.