The application of multiple reaction monitoring to assess ApoA-I methionine oxidations in diabetes and cardiovascular disease

•Methionine (M148) of apolipoprotein A-I is critical for LCAT function on HDL.•We developed a method to monitor modified M148 on HDL using multiple reaction monitoring (MRM).•An increase in oxidized M148 relative to the native peptide was observed in HDL isolated from research participants with diabetes and evidence of past cardiovascular disease.•Monitoring of M148 oxidations using MRM can serve as a potential biomarker for diabetes complications.

The oxidative modification of apolipoprotein A-I’s methionine148 (M148) is associated with defective HDL function in vitro. Multiple reaction monitoring (MRM) is a mass spectrometric technique that can be used to quantitate post-translational modifications. In this study, we developed an MRM assay to monitor the abundance ratio of the peptide containing oxidized M148 to the native peptide in ApoA-I. Measurement of the oxidized-to-unoxidized-M148 ratio was reproducible (CV < 5%). The extent of methionine M148 oxidation in the HDL of healthy controls, and type 2 diabetic participants with and without prior cardiovascular events (CVD) were then examined. The results suggest a significant increase in the relative ratio of the peptide containing oxidized M148 to the unmodified peptide in the HDL of participants with diabetes and CVD (p < 0.001), compared to participants without CVD. Monitoring the abundance ratio of the peptides containing oxidized and unoxidized M148 by MRM provides a means of examining the relationship between M148 oxidation and vascular complications in CVD.

Graphical abstractM148 Oxidation Monitored By MRM: a potential biomarker for diabetes and cardiovascular disease.Figure optionsDownload full-size imageDownload as PowerPoint slide