Baseline diene conjugation in LDL lipids from newly diagnosed type 2 diabetic patients

Background: To determine whether the susceptibility of low-density lipoproteins (LDL) to oxidation was altered in subjects with newly diagnosed type 2 diabetes mellitus and impaired glucose tolerance using the measurement of LDL baseline diene conjugation (LDL-BDC) as an indicator of circulating mildly oxidized LDL in vivo. Methods: LDL was isolated from sera of 26 newly diagnosed patients with type 2 diabetes mellitus (type 2 OM), 43 subjects with impaired glucose tolerance (IGT), and 67 subjects with normal glucose tolerance (NGT), who were matched for age, gender, body mass index and serum lipids. Twenty-seven healthy subjects with normal body mass index and normal values of lipids served as a control group. In all groups the LDL-BDC was compared with the production of conjugated dienes after copper-induced LDL oxidation, and with total antioxidative status. Results: The LDL-BDC levels (mumol/l; mean +/- SD) were similar in the three glucose tolerance categories (NGT 66.5 +/- 6.9; IGT 67.9 +/- 6.5; type 2 DM, 68.1 +/- 7.1 p = 0.52) and there was no difference in comparison with the control group (68.9 +/- 4.2 mumol/l). Also, no significant differences between the groups were observed in the susceptibility to LDL oxidation in vitro or total antioxidative status. There was no correlation between glycemia and mildly oxidized LDL in vivo, nor with any of the parameters of the LDL oxidation in vitro. Conclusions: In the examined population of newly diagnosed diabetic patients with mild hyperglycemia, as evidenced by the level of glycated haemoglobin (HbA(1c)), a lack of changes in the susceptibility of LDL to oxidation both in vivo and in vitro was established.