Molecular Marker Strategies Supporting The Novartis US92 Study-A Metabolite Biomarker Discovery Study in Plasma From Renal Transplant Patients.

Purpose. Vascular endothelial dysfunction is a major risk factor after renal transplantation. We assessed endothelial function in the plasma of a subset of renal transplant patients enrolled in the Novartis US92 trial using a comprehensive combined targeted and non-targeted metabolomics strategy to assess changes in metabolite patterns. Methods. Plasma was collected longitudinally (baseline, 1, 2, 4 and 6 months) from 116 patients. In addition to ADMA, SDMA, arginine, homcysteine, methionine, cysteine, glutathione, 8-isoprostanes, amino acid profiles, fatty acid profiles and a plasma metabolomics panel (HPLC-MS/MS and GC-MS), plasma concentrations of endothelial dysfunction markers (S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) (n=457) and sixteen bioactive lipid mediators (hydroxyoctadecadienoic acid/ hydroxyeicosatetraenoic acid/hydroxyeicosapentaenoic acid (HODE/HETE/HEPE) n=470) were analyzed using HPLC-MS/MS. Results. SAM and SAH concentrations decreased (ANOVA p< 0.05) with improvement in GFRs. Comparison of SAM and SAH concentrations during episodes of biopsy proven acute rejection (BPAR) and periods of normal renal function, defined as GFR ≥ 90 mL/min per 1.73m2, showed significant elevations (p< 0.05) of both analytes. Interestingly, SAH was already elevated before BPAR was diagnosed (p < 0.05, Tukey HSD post hoc test), while creatinine in serum and GFRs remained unchanged. Four out of 16 bioactive lipids were changed (12-HETE, 20-HETE, 12-HEPE, and 18-HEPE; ANOVA p< 0.05) when correlated to GFR. Significant increases were observed in 18-HEPE and 12-HETE concentrations not only in samples collected during BPAR episodes (p< 0.05), but 12-HETE was also elevated in samples collected preceding BPAR (p< 0.05, Tukey HSD). Again, these changes were observed before there were any relevant changes in creatinine and GFR. Summary. Although a comprehensive profiling approach including a total of 609 metabolites was used, the data consistently pointed towards the transmethylation pathway (SAM and SAH) and the arachidonic acid bioactive lipid pathway (18-HEPE and 12 HETE) as the most important markers. Conclusions. These markers had already significantly changed prior to GFR and creatinine changes and should further be studied to validate their potential predictive value. DISCLOSURES:Ingle, G.: Employee, Novartis. Patel, D.: Employee, Novartis. Christians, U.: Grant/Research Support, Novartis.