Determination of four forms of plasma thiol amino acids in individuals with chronic kidney disease by UPLC-MS/MS

The study introduces a robust analytical method based on UPLC-MS/MS for quantifying thiol amino acids, including cysteine (Cys), cysteinylglycine (CG), homocysteine (Hcy), and glutathione (GSH), in their total and total free forms within human plasma. An optimized blank matrix was employed for accurate quantification of endogenous compounds. The method exhibited excellent linearity, precision, accuracy, recovery, and stability, making it highly suitable for plasma analysis. Distinct differences in plasma levels of GSH, Cys, Hcy, and CG across various forms (total, total free, native prototype, and symmetrical oxidation) were observed between healthy individuals and chronic kidney disease (CKD) patients. Comprehensive correlation and receiver operating characteristic (ROC) analyses revealed disrupted thiol amino acid metabolism in CKD, accompanied by heightened oxidative stress. Notably, various forms of Cys and Hcy correlated significantly with renal function markers and demonstrated high diagnostic efficacy in ROC evaluation, with Cys, particularly Cys (F), outperforming others. Hcy further complements Cys in assessing renal function impairment severity.