HDAC1 and Alzheimer disease: Similarly, in urine samples of AD and controls, there is a significant difference in the 8OHG and 8OHG/2dG (2′-deoxyguanosine) levels [42] Histone deacetylases (HDAC1) are enzymes that modulate transcription, chromatin remodeling, and DNA repair, including modulation of 8OHdG repair in the brain.