Acute Exercise Activates AMPK in the Mouse Aorta
Abstract Number: 1063-P
Authors: JOSE M. CACICEDO, MARIE-SOLEIL GAUTHIER, NATHAN K. LEBRASSEUR, RAVI JASUJA, NEIL B. RUDERMAN, YASUO IDO
Institutions: Boston, MA, Groton, CT
Results: Proper endothelial cell (EC) function is required for the regulation of vascular tone and the maintenance of anti-thrombotic and pro-coagulant processes. An enzyme key to proper EC function is endothelial nitric oxide synthase (eNOS) which, by generating nitric oxide (NO), confers on endothelium the ability to regulate vascular tone and hemostasis. AMP-activated protein kinase (AMPK) has been shown to phosphorylate and activate eNOS at Ser1177 in vitro and in cultured ECs; however, whether this occurs in endothelium in vivo is unclear. In this study, we demonstrate that both AMPK and eNOS are activated by a single bout of exhaustive treadmill exercise in the vascular endothelium of the mouse aorta. Since we did not exercise AMPK knock-out mice, we cannot conclusively demonstrate that AMPK was solely responsible for the phosphorylation of eNOS at S1177. On the other hand, we determined that of the three kinases most likely responsible for eNOS phosphorylation at that site (Akt/PKB, AMPK, and PKA), Akt is not one of them. Activating phosphorylations on Akt at S473 and T308 were either unaltered or decreased by exercise in the aortas, and there was no change in the phosphorylation of GSK3-beta at its Akt specific phosphorylation site (S9). In support that AMPK may be the kinase responsible for eNOS-S177 phosphorylation, we found (1) a significant linear correlation between AMPK-T172 and eNOS-S1177 phosphorylations, (2) aortic AMPK and eNOS phosphorylations both positively correlated with the net work done by the animals pointing at a common mechanism of activation, and (3) evidence to suggest the activation of a SIRT1-LKB1 signaling mechanism that has been linked to AMPK activation in other cells and tissues. The role of PKA remains to be determined. In conclusion, this study provides the first evidence that an acute bout of exercise causes AMPK activation in the aorta. The results also suggest that AMPK is a likely regulator of eNOS activity induced by exercise.