INCREASED SUSCEPTIBILITY TO LIPID OXIDATION OF LOW-DENSITY LIPOPROTEINS AND ERYTHROCYTE-MEMBRANES FROM DIABETIC-PATIENTS

The aim of the present study was to determine if low-density lipoprote ins (LDLs) and red blood cell (RBC) membranes from diabetic patients p resent an increased susceptibility to lipoperoxidation, which might be related to the increased incidence of atherosclerosis in diabetes. LD Ls and RBC membranes were isolated from 11 insulin-dependent (IDDM) an d 18 non-insulin-dependent diabetic (NIDDM) patients and exposed to a peroxidative stress by incubation with phenylhydrazine. The susceptibi lity to peroxidation was determined by measuring the production of thi obarbituric acid-reactive substances (TEARS) after the incubation. The following parameters were also evaluated: plasma glucose, triglycerid es (TG), phospholipids (pi.), total and high-density lipoprotein (HDL) cholesterol, apolipoprotein (ape) A-I, apo B, hemoglobin A(1c) (HbA(1 c)), LDL PL and cholesterol, LDL fatty acid composition, and RBC membr ane PL and cholesterol. Although they were apparently normolipidemic, diabetic patients showed an increased susceptibility to peroxidation i n LDLs and erythrocyte membranes as compared with control subjects. Th e amount of arachidonic acid in LDLs and the PL concentration of RBC m embranes from diabetic patients were significantly higher than in norm al subjects. The increased lipoperoxidability of both RBC membranes an d LDLs might play a central role in the pathogenesis of the vascular c omplications of diabetes mellitus.