Changes in endothelial cell secretome after sirtuin-1 knock-down

Sirtuin1 (Sirt1) in skeletal muscle (SK) and fat protects against metabolic damage by stimulating insulin sensitivity. Here we report that mice with selective deletion of endothelial Sirt1 (E-Sirt1-KO) paradoxically exhibit heightened whole-body insulin sensitivity. Akt phosphorylation, glucose uptake, and glycolysis are boosted in SK and brown adipose tissue (BAT) of E-Sirt1-KO mice. E-Sirt1-KO mice have higher energy expenditure and are partially protected from high-fat diet-induced insulin resistance. Enhanced insulin sensitivity and peripheral tissue Akt phosphorylation in E-Sirt1-KO mice is transferrable to wild-type mice via the systemic circulation after surgical parabiosis. Silencing of Sirt1 in endothelial cells upregulates transcription of the F-actin-binding protein thymosin beta-4 (Tβ4), whose secretion activates Akt in skeletal myotubes. Sirt1 downregulation stimulates endothelial Tβ4 transcription through inhibition of autophagy and upregulation of nuclear factor-kappa B signaling. Thus, unlike Sirt1 in skeletal muscle and fat, endothelial Sirt1 curtails whole-body insulin sensitivity by inhibiting expression of secreted Tβ4.