Lipid oxidation plays a role in the pathophysiology of several diseases, including diabetes. Patients with type 2 diabetes show abnormally high plasma levels of phosphatidylcholine hydroperoxide (PCOOH). However, little is known about the biochemical processes that increase plasma PCOOH in diabetes. We hypothesized that "glycated lipid moieties" may form in diabetic plasma and cause oxidative stress resulting in PCOOH formation. To evaluate this hypothesis, liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were developed to analyze Amadori-glycated phosphatidylethanolamine (Amadori-PE, an early stage Maillard product), as well as the advanced glycation end products (AGE) carboxymethyl-PE (CM-PE) and carboxyethyl-PE (CE-PE). The product ion scan, neutral loss scanning, and multiple reaction monitoring provide useful structural and quantitative information about Amadori-PE, CM-PE, and CE-PE in diabetic plasma and erythrocytes. We found that plasma and erythrocyte Amadori-PE concentrations were significantly higher in diabetic patients (757 ± 377 nM plasma, 2793 ± 989 nM packed cells) than in normal subjects (165 ± 66 nM plasma, 712 ± 52 nM packed cells), and that Amadori-PE concentrations were positively correlated with PCOOH. By contrast, no significant differences were observed in blood AGE-PE concentrations between diabetic patients (CM-PE: 7.7 ± 3.5 nM plasma, 528 ± 83 nM packed cells; CE-PE: 2.5 ± 1.1 nM plasma, 82 ± 24 nM packed cells) and normal subjects (CM-PE: 6.6 ± 3.1 nM plasma, 705 ± 533 nM packed cells; CE-PE: 4.2 ± 1.5 nM plasma, 68 ± 16 nM packed cells). These results suggest that Amadori-PE is more prone to accumulation in the blood with diabetes than CM-PE or CE-PE. This review describes the involvement of blood lipid glycation and lipid oxidation in the development of diabetes.
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