Altered SIRT1 and CD38 immunoreactivity with age. Representative Western blot images for SIRT1 (A) and CD38 (C) in brain homogenates isolated from NTG and AD-Tg mice (3–12 months). (B) Significantly increased SIRT1 levels (ratio SIRT1:GAPDH) are observed in AD-Tg homogenates of 6 months compared to 3 months; and 9 months compared to both 3 and 6 months. (D) Significant increases in CD38 levels are observed at 3 and 12 months in AD-Tg homogenates compared to NTG mice. Significant decrease in CD38 levels are observed at 6 months in AD-Tg homogenates compared to 3 months AD-Tg mice. Data are presented as the average SIRT1 or CD38 ± SE. N = 3 separate animals per age group. **p < 0.05; *p < 0.01; a: AD-Tg significantly different from NTG; b: 6 months AD-Tg significantly different from 3 months AD-Tg.