Susceptibility of serum lipids to copper-induced peroxidation correlates with the level of high density lipoprotein cholesterol

As a first step in evaluating the significance of our recently developed me thod of monitoring the kinetics of copper-induced oxidation in unfractionat ed serum, we recorded the kinetics of lipid oxidation in the sera of 62 hyp erlipidemic patients and analyzed the correlation between oxidation and lip id composition of the sera [high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides]. We used six fac tors to characterize the kinetics of oxidation, namely, the maximal absorba nce of oxidation products (ODmax), the maximal rate of their production (V- max), and the time at which the rate was maximal (t(max)) at two wavelength s (245 nm, where 7-ketocholesterol and conjugated dienic hydroperoxides abs orb intensely, and 268 nm, where the absorbance is mostly due to dienals). The major conclusions of our analyses are that: (i) Both ODmax and V-max co rrelate positively with the sum of concentrations of the major oxidizable l ipids, cholesterol, and cholesteryl esters. (ii). The value of t(max), whic h is a measure of the lag preceding oxidation and therefore reflects the re sistance of the serum lipids to copper-induced oxidation, exhibits a negati ve correlation with HDL cholesterol. Although this finding accords with the observation of shorter lags for HDL than for LDL, it is apparently inconsi stent with the role of HDL as an antirisk factor in coronary heart diseases .