Effect of oxidized lipids in the diet on oxidized lipid levels in postprandial serum chylomicrons of diabetic patients

OBJECTIVE - To determine whether humans with type 2 diabetes have increased levels of oxidized fatty acids in their serum chylomicron fraction after t he ingestion of dietary oxidized fatty acids. RESEARCH DESIGN AND METHODS - The study was performed on 31 male type 2 dia betic patients and 24 age-matched control subjects. Among the diabetic pati ents, 22 had poor glycemic control, defined as HbA(1) >10% (normal value <7 .7%). Nine patients had good glycemic control (HbA(1) less than or equal to 10). Heated corn oil containing low or high levels of oxidized fatty acids was used as a test meal. At 2.5 h after the test meal, 50-ml blood samples were obtained from all subjects, and the chylomicron fraction (S-integral >1,000) was isolated. The degree of oxidation in chylomicrons was determine d by measuring conjugated dienes. For determining the postprandial levels o f triglycerides and of oxidized lipids in serum chylomicrons over an extend ed time period, blood samples were obtained at 0, 2.5, 5.0, and 7.5 h for i solation of chylomicrons and determination of fatty acid oxidation. RESULTS - We found that at 2.5 h after the consumption of the test meal con taining either a low or high oxidized fatty acid content, conjugated dienes in serum chylomicrons in diabetic subjects in poor glycemic control were i ncreased compared with those in control subjects. Diabetic patients in good glycemic control had similar levels of oxidized lipid in their chylomicron s when compared with control subjects. Additionally in diabetic patients in poor glycemic control, the levels of oxidized lipids in chylomicrons remai ned elevated for an extended postprandial period. CONCLUSIONS - In diabetic subjects with poor glycemic control, dietary oxid ized lipids induce an exaggerated and sustained increase in the levels of o xidized lipids in chylomicrons when compared with either control subjects o r diabetic patients with good glycemic control. These increased postprandia l levels of potentially atherogenic oxidized lipids may contribute to the a ccelerated atherosclerosis associated with diabetes.