Comprehensive Quantification of Carboxymethyllysine-Modified Peptides in Human Plasma

Abstract

A prolonged hyperglycemic condition in diabetes mellitus results in glycation of plasma proteins. N(ε)-Carboxymethyllysine (CML) is a well-known protein advanced glycation end product, and one of its mechanisms of formation is through further oxidation of Amadori compound modified lysine (AML). Unlike enrichment of AML peptides using boronate affinity, biochemical enrichment methods are scarce for comprehensive profiling of CML-modified peptides. To address this problem, we used AML peptide sequence and site of modification as template library to identify and quantify CML peptides. In this study, a parallel reaction monitoring workflow was developed to comprehensively quantify CML modified peptides in Type 1 diabetic subjects' plasma with good and poor glycemic control (n = 20 each). A total of 58 CML modified peptides were quantified, which represented 57 CML modification sites in 19 different proteins. Out of the 58 peptides, five were significantly higher in poor glycemic control samples with the area under the receiver operating characteristic curve ≥0.83. These peptides could serve as promising indicators of glycemic control in Type 1 diabetes management.

Plasma/Serum Proteomics based on Mass Spectrometry

“…Enrichment of glycated peptides/glycopeptides prior to LC-MS/MS analysis is important because of their relatively low abundance. Borate/boronate affinity purification is popular for glycated peptides, and dozens to hundreds of glycated proteins have been identified in human serum and plasma [ 108 - 110 ]. Recently, AGE antibodies have been produced, providing an exciting way to analyze plasma protein AGEs [ 111 ].…”

Recent Advances in Mass Spectrometry-Based Glycomic and Glycoproteomic Studies of Pancreatic Diseases

“…This study quantified 58 modified peptides from 19 proteins with 57 sites. Five modified peptides were significantly higher in poor glycemic control compared to good control (Korwar and Zhang, 2021). In a different study on T1D, another AGE, modification with glyoxal (also shown in Figure 4), was studied on histones.…”