Increased levels of malondialdehyde and 4-hydroxy-2-nonenal have been detected in brain tissue and cerebrospinal fluid (CSF) samples of AD patients [27,28], together with high plasma levels of AGEs and protein carbonyls in male patients [29], while the levels of antioxidant enzymes, such as glutathione peroxidase, catalase, or superoxide dismutase were reduced in areas of the brain affected by AD pathology [30]. This evidence concerns the gene CAT and Alzheimer disease.