Ta. Mori et al., ANALYSIS OF NATIVE AND OXIDIZED LOW-DENSITY-LIPOPROTEIN OXYSTEROLS USING GAS-CHROMATOGRAPHY MASS-SPECTROMETRY WITH SELECTIVE ION MONITORING, Redox report, 2(1), 1996, pp. 25-34
Cholesterol oxidation products have been demonstrated to possess a wid
e variety of biological properties and have been implicated in playing
an important role in the development of atherosclerosis, We have deve
loped an analytical method using capillary gas chromatography-mass spe
ctrometry (CC-MS) for the analysis of cholesterol oxidation products i
n low-density lipoprotein (LDL), The method uses programmed multiple s
elected ion monitoring (SIM), providing enhanced sensitivity and accur
acy of peak detection over full-scan mass spectra, The major oxidation
products of cholesterol in oxidized LDL were identified as 7 beta-hyd
roxy-cholesterol and 7-keto-cholesterol, Minor products included 4 bet
a-hydroxy-cholesterol, 6 beta-hydroxy-cholesterol and cholesterol-5 al
pha,6 alpha-epoxide, Native LDL contains 7-lathosterol, which is a bio
synthetic precursor of cholesterol, as well as low levels of 7 beta-hy
droxy-cholesterol and 7-keto-cholesterol, 7-Lathosterol was not detect
ed in oxidized LDL, A time course oxidation of native LDL with 8 mu M
CuCl2 demonstrated a rapid increase in 7 beta-hydroxy-cholesterol and
7-keto-cholesterol over the first 4 h, Cholesterol -5 alpha,6 alpha-ep
oxide, and beta 4-hydroxy- and 6 beta-hydroxy-cholesterol levels incre
ased gradually, while 7-lathosterol decreased over the same period, Th
is method was used to measure the levels of 7-lathosterol and choleste
rol oxides in the LDL of 20 healthy subjects in order to establish the
mean concentration and a reference range, This method can be used for
the characterization and quantitation of oxysterols in native and oxi
dized LDL and may afford an additional index of oxidative modification
of plasma lipoproteins.