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 pe roxidation 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 hypot hesized that 9-OH-C18:2 would be formed in hydroxyl radical reactions to li noleic acid (C18:2) during glucose-induced oxidative stress, and confirmed that the formation of 9-OH-C18:2 was induced by ultraviolet (UV)-C irradiat ion to the synthetic C18:2, UV-C light generates highly reactive hydroxy ra dicals. C18:2 is confirmed to be the precursor of 9-OH-C18:2. To estimate t he degree of oxidative damage to red cell membrane phospholipids, we develo ped a selective ion monitoring gas chromatography-mass spectrometric measur ement 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-O H-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%) s ubjects. 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 i n red cell membranes should be useful for assessing oxidative damage to mem brane phospholipids in diabetes. (C) 1999 Elsevier Science B.V. All rights reserved.