APP and Alzheimer disease: Nicotinamide and/or nicotinamide mononucleotide also counteract amyloid toxicity, by reducing expression of AD-related genes (amyloid precursor protein and presenilin 1) and reactive oxygen species (ROS) generation, and by improving neuron survival: both in vitro (organotypic hippocampal slice cultures) and in vivo (AD model rats) studies have indeed underlined the protective effects of vitamin B3 against Aβ-induced neurotoxicity [140,141].