INCREASED SUSCEPTIBILITY OF LDL TO IN-VITRO OXIDATION IN PATIENTS ON MAINTENANCE HEMODIALYSIS - EFFECTS OF FISH-OIL AND VITAMIN-E ADMINISTRATION

Oxidized low-density lipoproteins (LDL) play an important role in the pathogenesis of atherosclerosis. An increased sensitivity of red blood cell membranes to lipid peroxidation has been previously demonstrated in patients with chronic renal failure, suggesting that the antioxida nt defence of lipoproteins might be impaired. Fish oil supplementation has been proposed in dialysis patients, but it is still unclear if th e positive effects of fish oil depend only on its polyunsaturated fatt y acid content or on other factors, such as the usually added antioxid ants. Moreover, the increased concentration of highly peroxidable n-3 polyunsaturated fatty acids induced by fish oil in LDL particles could favour LDL oxidation and possibly the development of atherosclerosis. The present study was designed to evaluate the susceptibility of LDL to in vitro oxidation (lag phase) and the rate of lipid peroxidation ( propagation phase) by fluorescence development during copper exposure in 14 hemodialysis patients. A further aim was to compare the effects on lipid metabolism and LDL oxidation of fish oil supplementation (20 ml containing vitamin E 20 IU as antioxidant) for 30 days and of vitam in E administration (50 IU) for another 30 days. The length of the lag phase and Vitamin E concentration were significantly reduced (p < 0.0 1) in hemodialysis patients and increased significantly (p < 0.01) aft er administration of both fish oil and vitamin E. Fish oil supplementa tion also reduced plasma lipids significantly (p < 0.01) and increased the propagation phase (p < 0.01). Our results demonstrate that the su sceptibility of LDL to oxidation is enhanced in hemodialysis patients, suggesting a possible relationship between excessive LDL peroxidation and accelerated atherosclerosis. The increased susceptibility of LDL to in vitro oxidation can be explained, at least partially, by a reduc ed LDL vitamin E concentration. Since fish oil increased the lag phase to the same extent as vitamin E supplementation, the positive effect of fish oil could be partly explained by its antioxidant content.