BDNF and Huntington disease: Several studies, indeed, have put forward a beneficial effect of vitamin B3 in HD (Table 1): for example, nicotinamide is protective against toxicity of polyQ proteins in Drosophila HD models [158], while, in transgenic mouse models, it restores brain-derived neurotrophic factor (BDNF) protein levels, increases acetylated peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), a master regulator of mitochondrial biogenesis, and improves motor deficits [159].