Effect of genistein against copper-induced lipid peroxidation of human high density lipoproteins (HDL)

Several studies have demonstrated that the isoflavone genistein exerts a protective effect against lipid peroxidation of low density lipoproteins (LDL). Aim of our study was to investigate whether genistein protects high density lipoproteins (HDL), isolated from normolipemic subjects, against Cu++-induced lipid peroxidation. Our results demonstrated that genistein exerts an inhibitory effect against Cu++-induced lipid peroxidation of HDL, as shown by the lower increase in the levels of conjugated dienes in lipoproteins oxidized after preincubation with different concentrations of genistein (0.5–2.5 μM). Moreover the analysis of fluorescence emission spectra of tryptophan (Trp) and Laurdan (6-dodecanoyl-2-dimethyl-aminonaphthalene) demonstrated that genistein prevents the alterations of apoprotein structure and physico-chemical properties, associated with Cu++-triggered lipid peroxidation of lipoproteins. The protective effect exerted by genistein against oxidative damage of lipoproteins was realized at concentrations similar to those observed in plasma of human subjects consuming a traditional soy diet or receiving a soy supplement. Therefore, we suggested that antioxidant activity exerted by genistein against lipid peroxidation of HDL in vitro could be of physiological relevance.