Background and Objectives: Recent technological advancements in liquid chromatography coupled with high resolution mass spectrometry have facilitated clinical biomarker discovery, verification and validation. Targeted metabolic profiling refers to the precise quantitative measurements of metabolites for validation of markers identified via untargeted metabolomics. Specifically, multiple reaction monitoring mass spectrometry has enabled the reliable quantification of biomarkers in hundreds of samples, in a multiplexed manner. Methods: In this clinical study we have employed SID-MRM-MS (stable isotope dilution - multiple reaction monitoring - mass spectrometry) to quantify different classes of endogenous metabolites including intermediates of TCA cycle and lipids, on a triple quadrupole mass spectrometer. NPRP funded project enabled us to recruit a total of 169 controls and T2DM (type 2 diabetes mellitus) patients at the Hamad Medical Corporation in Doha, Qatar. Based on the discovery mode metabolomics profiling experiments, ten target molecules were chosen for biomarker validation using a cohort of 72 (control and diabetic) urine and plasma samples spiked with a known concentration of stable isotope labeled standard for each metabolite. The normalized peak area ratios were used to calculate the levels of deregulated metabolites in the T2DM cohort. We also performed extensive quality control experiments to check for retention time variation, matrix effects and metabolite degradation during sample processing. Statistical analysis was performed using GraphPad Prism (v5.0). ROC curves and interactive plots with a stringency cut-off of P ≤0.05 were plotted to test biomarker specificity and sensitivity. The cut-off values were selected to maximize the Youden index. Results: Statistically significant downregulation of succinate, xanthurenic acid, α-ketoglutaric acid and kynurenic acid were observed in the T2DM group while the concentrations of serotonin, PG (18:0/18:1), PC, sphingosine-1-phosphate and pyruvate were determined to be significantly higher in the diabetic group. The OPLS-DA model for the target metabolites had two orthogonal components and the R2 and Q2 were 0.88 and 0.87 respectively. Conclusions Our results underscore the clinical and translational utility of the MRM-MS approach. Further validation and characterization with larger cohorts, is likely to provide valuable insights into clinical potential of these markers and their correlation with T2DM associated complications.


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