LC–MS/MS for the simultaneous determination of polar endogenous ADMA and CML in plasma and urine from diabetics

Preparation of thiol-free amino acid plasma matrix for quantification of thiol amino acids and their oxidized forms in human plasma by UPLC-MS/MS

Thiol amino acids, with great physiological significance, are unstable, and have small molecular weights, as well as very low endogenous concentrations. Therefore, to quantitatively and directly analyze them using liquid chromatography-tandem mass spectrometry is difficult. To overcome these problems, we aimed to prepare a thiol-free amino acid plasm matrix as blank sample to reduce the background for the first time. Using compounds with maleimide group that react with classical thiols to generate water-insoluble products. Reducing agents Tris(2-carboxyethyl)phosphine (TCEP) was applied to cooperate with bismaleimide (DM) for elimination of thiol amino acids from plasma 10 min at room temperature and pH 7. Further, the residual TCEP from plasma were removed using an anion exchange resin within 10 min. Methodological validation analysis revealed good performance in linearity, precision, extraction recovery (≥ 82 %), and stability (except oxidized glutathione). This quantitative analysis was successfully applied to blood samples of 9 people in good health. This study provides a foundation for the development of accurate and rigorous quantitative analysis methods targeting thiol amino acids in different body fluids or tissues. Moreover, it paves the way toward realizing several clinical applications.

ADMA: a specific biomarker for pathologic progress in diabetic microvascular complications?

BACKGROUND

This study highlights the role of glycated hemoglobin (HbA1c), asymmetric demethylargine (ADMA) and N-ϵ-(carboxymethyl)-lysine (CML) in different periods of progress in Type 2 diabetes, and identifies a pathomechanism-based biomarker that is linked not only to the metabolic progresses but also to the underlying angiopathic progresses.

METHODS

Peripheral blood samples from 100 healthy volunteers, 227 subjects with prediabetes, 173 subjects with Type 2 diabetes and 92 subjects with early diabetic microvascular complications were collected and analyzed for HbA1c, ADMA and CML.

RESULTS

Compared to HbA1c and CML, ADMA is the strongest independent predictor and a significantly discriminative receiver operating characteristics profile, clearly distinguishing those with early diabetic microvascular complications.

CONCLUSIONS

ADMA maybe serve as a pathomechanism-based biomarker, predicting the progression of microvascular complications.