Formation of 9-hydroxy linoleic acid as a product of phospholipid peroxidation in diabetic erythrocyte membranes

The increased production of oxygen-derived free radicals (OFR) and lipid peroxidation may contribute to vascular complications in diabetes. Some lipid peroxidation products have already been reported to be formed via glucose-induced oxidative stress. We have identified 9-hydroxy linoleic acid (9-OH-C18:2) in the red cell membrane phospholipid of diabetic subjects. We hypothesized that 9-OH-C18:2 would be formed in hydroxyl radical reactions to linoleic acid (C18:2) during glucose-induced oxidative stress, and confirmed that the formation of 9-OH-C18:2 was induced by ultraviolet (UV)-C irradiation to the synthetic C18:2, UV-C light generates highly reactive hydroxy radicals. C18:2 is confirmed to be the precursor of 9-OH-C18:2. To estimate the degree of oxidative damage to red cell membrane phospholipids, we developed a selective ion monitoring gas chromatography-mass spectrometric measurement for C18:2 and 9-OH-C18:2. following methanolysis of red cell membrane phospholipids. The relative peak height ratio of C18:2. to 9-OH-C18:2 (9-OH-C18:2/C18:2) was measured in phospholipid extracts of red cell membranes from healthy (n = 29, 3.1 +/- 1.9%) and diabetic (n = 27, 20.9 +/- 16.1%) subjects. It was confirmed that 9-OH-C18:2/C18:2 is significantly (P < 0.001) elevated in patients with diabetes. The measurement of 9-OH-C18:2/C18:2 in red cell membranes should be useful for assessing oxidative damage to membrane phospholipids in diabetes. (C) 1999 Elsevier Science B.V. All rights reserved.