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.