Susceptibility of low- and high-density lipoproteins from diabetic subjects to in vitro oxidative modification.

Abstract

To investigate the hypothesis that lipid peroxidation of both low-density lipoproteins (LDL) and high-density lipoproteins (HDL) is important in the development of atherosclerosis. We have investigated whether LDL and HDL from patients with Type 1 diabetes mellitus (DM, n = 16) and Type 2 DM (n = 15) is more susceptible to Cu2+ -induced lipid peroxidation than LDL and HDL from a similar number of nondiabetic controls matched for age, gender and serum cholesterol. The vitamin E content of LDL and HDL from both groups of diabetic patients was not significantly different from controls. The LDL from Type 2 diabetic patients and HDL from both diabetic groups were significantly richer in triglyceride than controls. Phospholipid was decreased in LDL from Type 2 diabetic patients and protein was decreased in HDL in Type 1 DM, but otherwise the composition of LDL and HDL in diabetic subjects was similar to controls. No significant differences were observed in the generation of conjugated dienes or lipid peroxides in either LDL or HDL when the two groups were compared with each other or with their respective controls. Increased lipid peroxidation occurring in vivo in diabetes is unlikely to be the result of increased susceptibility of lipoproteins to lipid peroxidation, but rather to increased generation of free radicals, to oxidation of lipids other than those present in serum lipoproteins or to decreases in antioxidant systems other than the fat-soluble antioxidants present in lipoproteins.