Carvajal Karla, Zarrinpashneh Elham, Szarszoi Ondrej, Joubert Frederic, Athea Yoni, Mateo Philippe, Gillet Brigitte, Vaulont Sophie, Viollet Benoit, Bigard Xavier, Bertrand Luc, Ventura-Clapier Renée, Hoerter Jacqueline A
INSERM U-769, Faculté de Pharmacie, Université Paris-Sud, Châtenay-Malabry, France.
Am J Physiol Heart Circ Physiol. 2007 Jun;292(6):H3136-47. doi: 10.1152/ajpheart.00683.2006. Epub 2007 Mar 2.
Because the question "is AMP-activated protein kinase (AMPK) alpha(2)-isoform a friend or a foe in the protection of the myocardium against ischemia-reperfusion injury?" is still in debate, we studied the functional consequence of its deletion on the contractility, the energetics, and the respiration of the isolated perfused heart and characterized the response to low-flow ischemia and reperfusion with glucose and pyruvate as substrates. alpha(2)-AMPK deletion did not affect basal contractility, respiration, and high-energy phosphate contents but induced a twofold reduction in glycogen content and a threefold reduction in glucose uptake. Low-flow ischemia increased AMPK phosphorylation and stimulated glucose uptake and phosphorylation in both alpha(2)-knockout (alpha(2)-KO) and wild-type (WT) groups. The high sensitivity of alpha(2)-KO to the development of ischemic contracture was attributed to the constitutive impairment in glucose transport and glycogen content and not to a perturbation of the energy transfer by creatine kinase (CK). The functional coupling of MM-CK to myofibrillar ATPase and the CK fluxes were indeed similar in alpha(2)-KO and WT. Low-flow ischemia impaired CK flux by 50% in both strains, showing that alpha(2)-AMPK does not control CK activity. Despite the higher sensitivity to contracture, the postischemic contractility recovered to similar levels in both alpha(2)-KO and WT in the absence of fatty acids. In their presence, alpha(2)-AMPK deletion also accelerated the contracture but delayed postischemic contractile recovery. In conclusion, alpha(2)-AMPK is required for a normal glucose uptake and glycogen content, which protects the heart from the development of the ischemic contracture, but not for contractile recovery in the absence of fatty acids.
由于“AMP激活的蛋白激酶（AMPK）α2亚型在保护心肌免受缺血再灌注损伤中是有益还是有害？”这一问题仍存在争议，我们研究了其缺失对离体灌注心脏的收缩性、能量代谢和呼吸功能的影响，并以葡萄糖和丙酮酸为底物，对低流量缺血和再灌注反应进行了表征。α2-AMPK缺失不影响基础收缩性、呼吸和高能磷酸含量，但导致糖原含量降低两倍，葡萄糖摄取降低三倍。低流量缺血增加了AMPK磷酸化，并刺激了α2基因敲除（α2-KO）组和野生型（WT）组的葡萄糖摄取和磷酸化。α2-KO对缺血性挛缩发展的高敏感性归因于葡萄糖转运和糖原含量的先天性损伤，而非肌酸激酶（CK）对能量转移的干扰。在α2-KO和WT中，MM-CK与肌原纤维ATP酶的功能偶联以及CK通量确实相似。低流量缺血使两种品系的CK通量均受损50%，表明α2-AMPK不控制CK活性。尽管对挛缩更敏感，但在没有脂肪酸的情况下，α2-KO和WT的缺血后收缩性均恢复到相似水平。在有脂肪酸存在的情况下，α2-AMPK缺失也加速了挛缩，但延迟了缺血后收缩性恢复。总之，α2-AMPK对于正常的葡萄糖摄取和糖原含量是必需的，这可保护心脏免受缺血性挛缩的发展，但对于没有脂肪酸时的收缩性恢复并非必需。
