Ex vivo low-density lipoprotein oxidizability and in vivo lipid peroxidation in patients on CAPD

Background. Chronic renal failure is associated with accelerated atheroscle rosis and a high incidence of cardiovascular disease. Oxidative modificatio n of low-density lipoprotein (LDL) is considered a key event in atherogenes is. Methods. We studied the ex vivo oxidizability of LDL exposed to Cu2+ ions ( lag time, rate of propagation, maximum conjugated diene formation) and its relationship with LDL density, fatty acids, and antioxidants, along with pl asma malon-dialdehyde (MDA) and autoantibodies against Cu2+-, MDA-, and hyp ochlorous acid-modified LDL and plasma antioxidants in 17 continuous ambula tory peritoneal dialysis (CAPD) patients and 21 healthy control subjects. Results. LDL alpha- and gamma -tocopherol and total polyunsaturated fatty a cid (PUFA) concentrations were significantly higher in the CAPD patients. L DL density was shifted to small, dense LDL. LDL oxidizability was comparabl e to that of healthy subjects. Lag time correlated positively with LDL alph a -tocopherol and inversely with both total PUFA concentrations and density ; the rate of oxidation and LDL density correlated positively with total PU FA and total fatty acid concentrations, respectively. Ratios of autoantibod y titers against oxidized to native LDL did not differ between the two grou ps. While plasma alpha -and gamma -tocopherol concentrations and tocopherol to cholesterol ratios were significantly higher, vitamin C concentrations were very low in the CAPD patients. MDA concentrations were 1.7 times highe r than in healthy subjects. Conclusions. (I) Ex vivo LDL oxidizability is normal in CAPD patients as a result of efficient protection by LDL-associated lipophilic antioxidants. a lthough the LDL composition is altered toward high oxidizability; and (2) t he plasma antioxidant screen is insufficient due to impaired vitamin C stat us.