SIRT1 and Alzheimer disease: In sharp contrast, the SIRT1 expression levels in AD LCLs were dramatically down-regulated compared with centenarian LCLs (FD = −8.4; P = 1.2E-07) as well as compared with the LCLs from healthy donors aged 56–82 years (FD = −4.0; P = 0.001) or 21–35 years (FD = −6.8; P = 0.001; Fig. 1a).