Department of Cardiovascular Center, The First Hospital of Jilin University, Xinmin Street, Changchun 130021, China.
Department of Physiology and Biophysics, Mississippi Center for Heart Research, University of Mississippi Medical Center, 2500 N State Street, Jackson, MS 39216, USA.
Cardiovasc Res. 2018 May 1;114(6):805-821. doi: 10.1093/cvr/cvy033.
A longevity gene, Sirtuin 1 (SIRT1) and energy sensor AMP-activated protein kinase (AMPK) have common activators such as caloric restriction, oxidative stress, and exercise. The objective of this study is to characterize the role of cardiomyocyte SIRT1 in age-related impaired ischemic AMPK activation and increased susceptibility to ischemic insults.
Mice were subjected to ligation of left anterior descending coronary artery for in vivo ischemic models. The glucose and fatty acid oxidation were measured in a working heart perfusion system. The cardiac functions by echocardiography show no difference in young wild-type C57BL/6 J (WT, 4-6 months), aged WT C57BL/6 J (24-26 months), and young inducible cardiomyocyte-specific SIRT1 knockout (icSIRT1 KO) (4-6 months) mice under physiological conditions. However, after 45 mins ischaemia and 24-h reperfusion, the ejection fraction of aged WT and icSIRT1 KO mice was impaired. The aged WT and icSIRT1 KO hearts vs. young WT hearts also show an impaired post-ischemic contractile function in a Langendorff perfusion system. The infarct size of aged WT and icSIRT1 KO hearts was larger than that of young WT hearts. The immunoblotting data demonstrated that aged WT and icSIRT1 KO hearts vs. young WT hearts had impaired phosphorylation of AMPK and downstream acetyl-CoA carboxylase during ischaemia. Intriguingly, AMPK upstream LKB1 is hyper-acetylated in both aged WT and icSIRT1 KO hearts; this could blunt activation of LKB1, leading to an impaired AMPK activation. The working heart perfusion results demonstrated that SIRT1 deficiency significantly impaired substrate metabolism in the hearts; fatty acid oxidation is augmented and glucose oxidation is blunted during ischaemia and reperfusion. Adeno-associated virus (AAV9)-Sirt1 was delivered into the aged hearts via a coronary delivery approach, which significantly rescued the protein level of SIRT1 and the ischemic tolerance of aged hearts. Furthermore, AMPK agonist can rescue the tolerance of aged heart and icSIRT1 KO heart to ischemic insults.
Cardiac SIRT1 mediates AMPK activation via LKB1 deacetylation, and AMPK modulates SIRT1 activity via regulation of NAD+ level during ischaemia. SIRT1 and AMPK agonists have therapeutic potential for treatment of aging-related ischemic heart disease.
长寿基因 Sirtuin 1（SIRT1）和能量传感器 AMP 激活的蛋白激酶（AMPK）有共同的激活剂，如热量限制、氧化应激和运动。本研究的目的是研究心肌细胞 SIRT1 在与年龄相关的缺血性 AMPK 激活受损和对缺血性损伤易感性增加中的作用。
通过结扎左前降支冠状动脉建立体内缺血模型，在工作心脏灌流系统中测量葡萄糖和脂肪酸氧化。超声心动图显示，在生理条件下，年轻野生型 C57BL/6J（WT，4-6 个月）、老年 WT C57BL/6J（24-26 个月）和年轻诱导型心肌细胞特异性 SIRT1 敲除（icSIRT1 KO）（4-6 个月）小鼠之间的心脏功能无差异。然而，在缺血 45 分钟和再灌注 24 小时后，老年 WT 和 icSIRT1 KO 小鼠的射血分数受损。与年轻 WT 心脏相比，老年 WT 和 icSIRT1 KO 心脏在 Langendorff 灌流系统中也表现出缺血后收缩功能受损。老年 WT 和 icSIRT1 KO 心脏的梗死面积大于年轻 WT 心脏。免疫印迹数据表明，与年轻 WT 心脏相比，老年 WT 和 icSIRT1 KO 心脏在缺血期间 AMPK 和下游乙酰辅酶 A 羧化酶的磷酸化受到抑制。有趣的是，老年 WT 和 icSIRT1 KO 心脏中的 AMPK 上游 LKB1 发生高度乙酰化；这可能使 LKB1 的激活受到抑制，导致 AMPK 激活受损。工作心脏灌流结果表明，SIRT1 缺乏显著损害心脏中的底物代谢；在缺血和再灌注期间，脂肪酸氧化增加，葡萄糖氧化减少。通过冠状动脉给药途径将腺相关病毒（AAV9）-Sirt1 递送至老年心脏，这显著挽救了 SIRT1 的蛋白水平和老年心脏的缺血耐受性。此外，AMPK 激动剂可挽救老年心脏和 icSIRT1 KO 心脏对缺血性损伤的耐受性。
心脏 SIRT1 通过 LKB1 去乙酰化介导 AMPK 激活，AMPK 通过调节缺血期间 NAD+水平调节 SIRT1 活性。SIRT1 和 AMPK 激动剂具有治疗与年龄相关的缺血性心脏病的潜力。
