SOD2 converts superoxide to H2O2 and mitochondrial glutathione peroxidase GPx1 catalyzes the reduction of H2O2 to H2O. Hydroxyl radical is another extremely harmful reactive free radical in mitochondria, formed by combination of superoxide and H2O2. GPx1 could be another crucial antioxidant enzyme in CE cells. This evidence concerns the gene GPX1 and cholesteryl ester measurement.