MAPT and Alzheimer disease: NAD+ levels are reduced in animal models of AD, and elevation of cellular NAD+ levels by treatment with NAD+ precursors such as nicotinamide, nicotinamide mononucleotide, and nicotinamide riboside attenuates Aβ and tau pathologies, improves SIRT3 function, increases mitochondrial resistance to ROS, enhances mitophagy and prevents cognitive dysfunction, likely by upregulating the activity of the CREB transcription factor (Gong et al., 2013; Liu et al., 2013).