Gut microbiota and metabolites related intra-patient variability of tacrolimus pharmacokinetics predicted adverse one-year outcomes following kidney transplantation.

Kidney transplantation (KT) is an effective treatment for end-stage renal disease, with over 90 % of recipients requiring lifelong tacrolimus (Tac). However, The Tac pharmacokinetics exhibit high intra-patient variability (IPV), posing significant challenges. This study included 102 KT recipients at our center from October 2022 to December 2023. Patients were stratified into high- and low-IPV groups based on the median coefficient of variation of the the Tac trough concentration-to-dose ratio during the first post-transplant month. Fecal samples were collected for 16S rRNA sequencing and untargeted metabolomics analysis, while clinical outcomes within the first year were assessed for associations with the Tac IPV. Microbiome analysis revealed significant beta diversity differences (p = 0.0451) and 19 differential taxa, including g__Clostridia_vadinBB60_group enriched in high-IPV patients and g__Clostridia_UCG_014 in the low-IPV group. Metabolomics identified 1298 differential metabolites, with 729 enriched in high-IPV patients. Network analysis highlighted cholesterol and unsaturated fatty acid biosynthesis as central pathways, while both microbial functional predictions and metabolic enrichment analyses emphasized bile secretion. A random forest model validated the classification potential of these biomarkers, and associations between differential taxa and metabolites were observed. Clinical correlation analysis indicated the high Tac IPV as an independent protective factor against post-transplant hyperuricemia but a positive predictor of new-onset diabetes. This study is the first to link the Tac IPV, gut microbiota, metabolism, and one-year outcomes, offering novel insights into personalized care and the mechanisms underlying the Tac IPV.