Effect of LDL plus VLDL oxidizability and hyperglycemia on blood cholesterol, phospholipid and triglyceride levels in Type-I diabetic patients

Oxidative modification of low-density lipoproteins has been implicated in i mpaired lipid metabolism and its deposition in the arterial wall, and ather osclerosis. This study was carried out to determine the relationship betwee n the in vitro oxidizability of low-density lipoprotein (LDL) and very-low- density lipoprotein (VLDL) and the cholesterol, phospholipid and triglyceri de (TG) levels in the blood of Type-I diabetic patients. LDL + VLDL was iso lated using a micro-affinity column from serum of diabetic patients (n = 34 ) and age-matched normal individuals (n = 22). The oxidative susceptibility of LDL + VLDL was determined by treatment with 25 mu M CuCl2 for 1.5 h. Th e levels of total-, LDL-, and HDL-cholesterol, phospholipids and triglyceri des, as well as glycated hemoglobin (HbA(t)), were measured in the blood us ing standard methods. The diabetics had significantly higher levels of trig lycerides and phospholipids, but cholesterol levels were similar between Ty pe-I diabetics and age-matched normals. However, among diabetics, there was a significant correlation between the in vitro oxidation of LDL + VLDL at 1.5 h and total cholesterol (r = 0.49, P < 0.002), and LDLcholesterol (r = 0.54, P < 0.001) and TG (r = 0.34, P < 0.05) levels. The level of in vitro oxidizability of LDL + VLDL did not have any correlation with HDL-cholester ol or phospholipid levels. The level of glycemic control (HbA(1)) did not h ave any correlation with levels of LDL- or HDL-cholesterol or triglycerides , but was significantly correlated with phospholipid levers (r = 0.48, P < 0.005). This study suggests that the levels of LDL-cholesterol and triglyce rides in the blood are directly related to the degree of in vitro oxidative susceptibility of low-density lipoproteins in Type-1 diabetic patients. (C ) 2000 Elsevier Science Ireland Ltd. All rights reserved.