Susceptibility to copper-enhanced autoxidation of VLDL+LDL fractions from diabetic patients.

We describe a simplified method for studying the susceptibility to in vitro autoxidation of lipoproteins containing apolipoprotein B. It comprises copper induced autoxidation of VLDL+LDL plasma fractions and an assay for thiobarbituric acid reactive soluble substances. We studied autoxidation of VLDL+LDL in a population of 30 healthy subjects and a population of 30 diabetic patients. No significant difference in susceptibility to autoxidation could be detected. Protection afforded by ascorbic acid amounted to more than 95% at concentrations easily attainable in vivo by oral supplementation. Thiobarbituric acid reactive substances were higher in plasma from diabetic patients: 0.51 +/- 0.25 mumol/l vs 0.35 +/- 0.07 mumol/l for control subjects (p < 0.001). Our data confirm the presence of higher levels of lipid peroxides in diabetic patients, but fail to demonstrate any difference in susceptibility to oxidation of apolipoprotein B containing particles between control and diabetic subjects.