Very low density lipoprotein subfractions in Type II diabetes mellitus: Alterations in composition and susceptibility to oxidation

Abstract

Aims/hypothesis. Type II (non-insulin-dependent) diabetes mellitus is associated with raised triglycerides and increased very low density lipoprotein cholesterol. The aim of this study was to assess if very low density lipoprotein subfraction composition and potential to oxidise were altered in this condition. Methods. Very low density lipoprotein was separated into four subfractions (A → D) by a novel, rapid ultracentrifugation procedure. Analysis of each subfraction included lipid and fatty acid composition. Preformed peroxides were measured spectrophotometrically and conjugated dienes were used as an indicator of in vitro lipid oxidation. Results. In all results we compared patient and control subfractions. Mean fasting plasma glucose was 8.9 ± 2.0 mmol/l in patients vs 5.1 ± 0.4 mmol/l in control subjects (p < 0.001); patient HbA(1c) was 7.6 ± 1.4%. Patient total lipid standardised for apo B was higher than controls in subfractions A, B and C; A, 201 vs 60; B, 191 vs 40; C, 63 vs 21; D, 29 vs 34 μmol lipid per mg apo B (p < 0.05). Preformed peroxides were higher in all patient subfractions compared wit controls: A, 340 vs 48; B, 346 vs 42; C, 262 vs 28; D, 54 vs 16 nmol per mg apo B (p < 0.001). Patient subfractions A and D were more susceptible to in vitro oxidation. Monounsaturated fatty acids were lower in patients subfractions, 35.2 vs 36.7; B, 35.1 vs 38.7; C, 34.4 vs 36.5; D, 33.0 vs 35.5 as per cent total (p < 0.05). Conclusions/interpretation. These results indicate abnormalities in very low density lipoprotein subfraction composition and oxidation profile in Type II diabetic subjects, which are characteristic of more atherogenic particles and that may contribute to the development of cardiovascular disease in these patients.