SIRT1 and Alzheimer disease: PGC-1α, a crucial regulator of mitochondrial biogenesis, is suppressed in both AD models and patients (Qin et al., 2009; Sheng et al., 2012); SIRT1 expression and activity are also found to be reduced in the brains of AD patients (Julien et al., 2009; Lalla and Donmez, 2013).