Le. Schreier et al., LOW-DENSITY-LIPOPROTEIN COMPOSITION AND OXIDABILITY IN ATHEROSCLEROTIC CARDIOVASCULAR-DISEASE, Clinical biochemistry, 29(5), 1996, pp. 479-487
Objectives: To characterize low-density lipoprotein (LDL) chemical com
position and oxidability in normolipidemic and dyslipidemic patients w
ith atherosclerotic cardiovascular disease, as compared with matched c
ontrol subjects. To evaluate LDL susceptibility to oxidation, we deter
mined the cutoff points of thiobarbituric reactive substances (TBARS)
in LDL after oxidative stress, as well as its resistance to oxidation.
Design and methods: LDL (density 1.019-1.063 g/mL) of 24 men with ath
erosclerotic cardiovascular disease (12 normolipidemic and 12 dyslipid
emic patients) and 18 age-matched healthy control men. LDL chemical co
mposition was determined and apo B/cholesterol ratio was calculated. T
BARS in native LDL and after 60 and 120 min of LDL oxidation with copp
er were measured. The conjugated diene production kinetics during LDL
incubation with copper were also studied, lag time being an oxidation
resistance marker. Cutoff points for the positivity criterion of apoB/
cholesterol ratio in LDL and TBARS in native and oxidized LDL were eva
luated using the receiver operator characteristic (ROC) graphic method
. Results: LDL were triglyceride-enriched, the apoB/cholesterol ratio
being higher in patients than in controls, without differences between
normolipidemic and dyslipidemic subgroups. We have established the fo
llowing cutoff values to differentiate between patients and controls:
0.43 mg/mg for the apo B/cholesterol ratio in LDL; 3.0 nmol malondiald
ehyde/mg protein for TBARS in native LDL; 22 and 80 nmol malondialdehy
de/mg protein after 60- and 120-min postoxidative stress, respectively
. We did not find differences in the conjugated diene production kinet
ics between patients and controls. Conclusions: The enrichment in trig
lycerides and the high apoB/cholesterol ratio suggest the presence of
an abnormal LDL particle in normolipidemic and dyslipidemic patients.
This LDL particle was more susceptible to oxidation. In the ROC analys
is, the TBARS plot at 120 min exhibited greater accuracy and better pe
rformance than the other LDL oxidability markers.