Furthermore, increased levels of Al, Fe, Hg, and Ca decreased polyunsaturated fatty acids, increased oxidation of protein and DNA and lipid peroxidation, and the presence of oxidation products such as carbonyls, malondialdehyde, heme oxygenase-1, and peroxynitrite, which are initiators of free radicals, could trigger AD [146]. This evidence concerns the gene HMOX1 and Alzheimer disease.