Relation of Lipid Peroxides to Macrovascular Disease in Type 2 Diabetes

Lipid peroxides are thought to be formed by free radicals and may play an important role in the development of atheromatous vascular disease. We have investigated the relationship between lipids, lipoproteins, coagulation factors, and lipid peroxides (measured as thiobarbituric acid reacting species (TBARS)) in Type 2 diabetic patients with macrovascular disease. Eighteen diabetic and 20 non‐diabetic subjects with clinical evidence of ischaemic heart disease and/or peripheral vascular disease were investigated, together with 28 healthy subjects without evidence of vascular disease. TBARS concentrations in non‐diabetic (mean 5.0 (95% CI 4.5–5.7) μmol I−1) and diabetic groups (5.6 (5.1–6.0) μmol I−1) with macrovascular disease were not significantly different although values were higher in both groups of patients with vascular disease by comparison with control subjects (2.7 (2.4–3.1) (μmol I−1, p < 0.001). Significant univariate correlations between TBARS concentrations and measures of blood glucose control (fructosamine, blood glucose and HbA,) were found for all 66 subjects (r = 0.35–0.42, p < 0.01–p < 0.001), although no independent association between these parameters and TBARS was demonstrated in multiple regression analysis. In addition, TBARS levels were significantly correlated in univariate analysis with the apolipoprotein (apo) Al:apoB ratio (r = −0.56, p< 0.001), total cholesterol:high density lipoprotein cholesterol ratio (r = 0.52, p < 0.001), apoB (r = 0.51, p < 0.001), low density lipoprotein cholesterol (r = 0.40, p < 0.001), serum total triglyceride (r = 0.46, p < 0.001), apoAl (r = −0.35, p < 0.01) and serum total cholesterol (r = 0.39, p < 0.001). Multiple regression analysis of continuous variables showed that apoB (p < 0.001), age (p < 0.001), and apoAl (p = 0.008) were independently associated with serum TBARS although these associations disappeared if macrovascular disease was added to the regression equation as a categorical variable. Our data support previous studies which demonstrate increased serum concentrations of TBARS in subjects with macrovascular disease but suggest that levels are similarly elevated in diabetic and non‐diabetic subjects.