LDL oxidative modifications in well- or moderately controlled type 2 diabetes.

BACKGROUND: The aim of the study was to examine, by measurement of specific indicators of free radical-mediated oxidation of LDL, whether there is evidence of increased in vivo oxidation of LDL in type 2 diabetic patients, and to investigate their associations with carotid intima media thickness (IMT).
METHODS: In native LDL, we quantified five different products of LDL oxidation reflecting various stages of LDL oxidative modification in 38 individuals with well- or moderately controlled type 2 diabetes (HbA(1c) </= 8.5%) and 38 gender-matched subjects with normal glucose metabolism. Baseline conjugated dienes (BCD), 7-OH-glycero-phosphocholine (7-OH-GPC), lyso-phosphatidylcholine (lyso-PC), and ketocholesterol were determined in LDL, and circulating in vivo oxidized apolipoprotein B100 (Ox-apoB) was measured in plasma. The IMT of the carotid artery was measured by ultrasound.
RESULTS: Borderline higher carotid IMT values were observed in individuals with diabetes (0.88 +/- 0.14 vs 0.83 +/- 0.11 mm, p = 0.06). LDL-ketocholesterol (45.5 +/- 19.4 vs 37.1 +/- 13.8 nmol/mmol LDL-cholesterol, p < 0.05) and Ox-apoB (25.3 +/- 5.5 vs 22.2 +/- 5.8 U/mmol LDL-cholesterol, p < 0.05) were significantly increased in diabetic patients. The concentration of BCD, 7-OH-GPC and lyso-PC in LDL did not differ between diabetic patients and control subjects. No significant correlations were demonstrated between the measured indicators of LDL oxidation and carotid IMT.
CONCLUSION: Levels of BCD, 7-OH-GPC and lyso-PC, that is, intermediary products of LDL oxidation, were not significantly elevated, but ketocholesterol and Ox-apoB, that is, stable end products of the oxidation process, were increased in diabetic patients. We conclude that in vivo oxidation of LDL is increased, even in subjects with well- or moderately controlled type 2 diabetes. Copyright 2004 John Wiley & Sons, Ltd.