Activation of AMPK protects human coronary artery endothelial cells from lipoapoptosis. Cells were incubated in the presence or absence of palmitate (125 μM), metformin (A: 100 μM-2 mM), (B-E: 500 μM), with or without AICAR (200 μM) or Compound C (10 μM). (A) Metformin protects cells from lipoapoptosis in a dose-dependent manner after 24 h, an effect that is mimicked by AICAR (B) and blocked by Compound C after 24 h of incubation (C). Cleaved caspase 3 (CC3) levels over time (D) and in the presence or absence of metformin, AICAR and Compound C after 24 h (E). The protective effect of metformin against palmitate-induced apoptosis is lost upon downregulation of AMPK by siRNA transfection (F). Bars represent mean ± SEM. * p < 0.05 vs. control; # p < 0.05 vs. palmitate; § p < 0.05 vs. metformin + palmitate with Kruskal-Wallis one-way analysis of variance on ranks. n =4-5.