OS markers identified so far that are involved in AD are aryl hydrocarbon receptor (AHR)/AHR-nuclear translocator (ARNT) system, nuclear factor-erythroid 2-related factor-2 transcription factor (NRF2), myeloperoxidase (MPO) level/paraoxonase (PON)-1 activity [11]. The gene discussed is MPO; the disease is Alzheimer disease.