Other studies show increased OGG1 mRNA levels in brain tissue from the hippocampus, parahippocampal gyri and middle temporal gyri of patients with preclinical stages of AD compared to HC [18], suggesting that the elevation represents a compensatory increase in protein expression to moderate loss of activity due to posttranslational modification in response to increased oxidative DNA damage. This evidence concerns the gene OGG1 and Alzheimer disease.