The effect of Sirt1 genetic ablation on circadian gene expression was confirmed with pharmacological treatments using SIRT1 inhibitors (splitomicin and NAM) (Figure 3A), which had no effect on the Sirt1−/− MEFs (not shown). Analysis of dbp expression levels in WT MEFs treated with either inhibitors revealed a pattern highly similar to the one obtained with the Sirt1 null cells, basically displaying a significantly broader phase and higher amplitude in the oscillation (Figure 3A).