Direct effects of Leucine, β-Hydroxy-β-Methylbutyrate (HMB) and Ketoisocaproate (KIC) on SIRT1 activity. Recombinant human SIRT1 enzyme was incubated with Leucine, HMB and KIC for 45 min and fluorescence of deacetylated substrate was measured. Resveratrol and Suramin were used as positive and negative control, respectively. Valine was used as BCAA control. Data are expressed as means of % change of SIRT1 activity ± SE (n = 4, p ≤ 0.05).