Oxidized ldl

All the blood samples were centrifuged at −4°C, and the supernatant was collected and stored at −20°C and −80°C. All the metabolic assays of each subject were run in a single batch to minimize interassay variability. The serum glucose levels were measured by the glucose oxidase method (model 2300; YSI Life Sciences, Yellow Springs, OH). Serum insulin and C-peptide levels were measured by standard radioimmunoassay techniques. The coefficients of variation were 6% and 10%, respectively. The lower limit of the C-peptide assay was 0.1 ng/mL, and the intra-assay and interassay coefficients of variation were 7% and 13%, respectively. The A1C level was measured by the cationic, microcolumn chromatographic technique (Bayer, Inc.). The normal reference range was 4.0–5.6% (20.2–37.7 mmol/mol). The serum levels of cholesterol, HDL-C, and TGs were measured using enzymatic methods. LDL-C was calculated using the Friedwald equation, as follows: LDL-C = total cholesterol − HDL-C − TGs/5 for serum TGs <400 mg/dL. apoAl and apoBl00 levels were measured using nuclear magnetic resonance (LipoScience, Raleigh, NC). Adiponectin (Quantikine; R&D Systems, Minneapolis, MN) and oxidized LDL (Mercodia, Uppsala, Sweden) were measured using ELISA. CRP was measured using nephelometry (Synchron LX Systems).