SIRT1 and Insulin resistance: Because of the functional correlation between SIRT1 and estrogen signaling in cancer cells [11], we also assessed SIRT1 modulation by 17β-estradiol in rat VSMCs and, for comparison, in human peripheral blood mononuclear cells (PBMCs), a cell type in which SIRT1 downregulation is associated with insulin resistance and subclinical atherosclerosis [12].