ATF4 and Alzheimer disease: Moreover, SIRT1 regulates mitochondrial biogenesis and function by directly controlling the activity of proliferator-activated receptor gamma coactivator 1alpha (PGC-1α) through phosphorylation and deacetylation (60), whereas quercetin cause a reduction in the phosphorylation of the eukaryotic initiation factor 2 alpha (eIF2α), as well as activate the expression of transcription factor 4 (ATF4) through the GADD34 induction in the brain, leading to memory improvement in aged mice and delayed memory deterioration at the early stage of APP23 AD model mice (61).