Effect of caffeine on oxidation susceptibility of human plasma low density lipoproteins

The effect of caffeine on oxidation susceptibility of low density lipoproteins (LDL) has been studied. LDL oxidation was induced by copper ions and an azo initiator. The conjugated dienes formation was followed spectrophotometrically and indicated the LDL oxidation status. Changes in LDL protein moiety during the lag phase, studied only in the experiments of copper induced oxidation, were followed using the intrinsic fluorescence spectroscopy. The decay of LDL fluorescence signal during initial stages of oxidation was slower in the presence of caffeine. Supported by the fluorescence quenching and polarization measurements, these results may indicate the protective role of caffeine against LDL oxidation in vitro. The results also indicate that the production of conjugated dienes in the propagation and decomposition phase of LDL oxidation is lower in the presence of caffeine, regardless of the initiation mechanism. These findings may have implications for the effect of caffeine on LDL in vivo.