Fig. 3: Enhanced insulin sensitivity and Akt signaling in male mice and cells deficient for endothelial Sirt1 is transferable via the systemic circulation and conditioned medium.

a, b Parabiosis to E-Sirt1-KO stimulates whole-body insulin sensitivity and Akt signaling in gastrocnemius of Sirt1^fl/fl mice when parabiosed with Sirt1^fl/fl (n = 6 pairs of mice) or with KO mice (n = 5 pairs of mice). a Parabiosis model and glucose tolerance test (*p < 0.05) with area under the curve (*p  = 0.04); b Insulin tolerance test (*p = 0.001), and c Akt and GSK3β phosphorylation in gastrocnemius muscle in Sirt1^fl/fl mice parabiosed with Sirt1^fl/fl (n = 6 pairs of mice) vs. KO mice (n = 6 pairs of mice); d Akt and GSK3β phosphorylation in C2C12 skeletal myotubes incubated with conditioned medium from aortic endothelial cells of Sirt1^fl/fl (n = 6 independent experiments) vs. KO (n = 6 independent experiments); e Expression of Sirt1 in HUVECs transfected with Sirt1 siRNA or control siRNA; f Akt and GSK3β phosphorylation in C2C12 myotubes incubated with CM from HUVECs transfected with control siRNA (n = 8 independent experiments) vs. Sirt1 siRNA (n = 8 independent experiments). Representative blots are shown. Data are shown as mean ± SEM. Two-tailed unpaired Student’s t test was used. In (a, b), black line or gray bar represents Sirt1^fl/fl-Sirt1^fl/fl pair, and blue line or bar represents Sirt1^fl/fl-KO pair. In d, f, the gray bars represent control-CM treated groups, and blue bars represent KO-CM or si-CM treated group. Each dark dot or blue circle represents one sample. EBM2 Endothelial Basic Medium 2. Sirt1^fl/fl Sirt1^flox/flox. KO E-Sirt1-KO mice. Control-si control siRNA, Sirt1-si Sirt1 siRNA. C-CM control siRNA conditioned medium, Si-CM Sirt1 siRNA conditioned medium. Source data are provided as a Source Data file.