SIRT1 and obstructive sleep apnea syndrome: We measured the levels of phospho-Thr172 AMPK α (an active catalytic subunit of the AMPK complex) in atria and found that the phosphorylation of Sirt1 and AMPK was decreased in OSA dogs, while metoprolol increased the activation of Sirt1 and AMPK (P < 0.05, Fig. 5A–F).