尽管原因尚不清楚,但慢性热量限制会引发心脏功能的不利改变。这项工作评估了Akt2可能参与热量限制诱发的心脏几何和功能变化以及关注自噬和线粒体自噬的负责过程。在评估心肌稳态之前,对Akt2敲除和WT小鼠进行热量限制30周。热量限制损害了超声心动图参数(左心室壁厚减少,LVEDD,每搏输出量,心输出量,射血分数,分数缩短,和低压质量),心肌细胞收缩和细胞内Ca2+容量,心肌萎缩,与血液糖皮质激素升高相关的间质纤维化和线粒体损伤,自噬(LC3B,p62,Atg7,Beclin-1),和线粒体自噬(Pink1,Parkin,TOM20),抑制心脏ATP水平,线粒体蛋白PGC1α和UCP2,抗凋亡蛋白Bcl2,细胞内Ca2+控制成分Na+-Ca2+交换剂,SERCA2a的磷酸化,mTOR(Ser2481)和ULK1(Ser757),上调Bax,磷脂,磷酸化的Akt2,AMPK,和ULK1(Ser555),除了自噬标记(Beclin-1,Atg7),AMPK的磷酸化,Akt2消融消除mTOR和ULK1。随着热量限制,CDK1和DRP1磷酸化水平明显上调,Akt2基因敲除逆转了反应.糖皮质激素受体拮抗减轻了热量限制引起的心脏重塑和心肌细胞功能的变化,Parkin消融和Mdivi-1。体外实验表明血清剥夺或糖皮质激素诱发GFP-LC3B积累和心肌细胞功能障碍,通过抑制Akt2,CDK1或DRP1而否定,而线粒体自噬诱导逆转了Akt2消融诱发的心脏保护作用。这些观察结果支持Akt2消融通过以CDK1-DRP1依赖性方式纠正糖皮质激素诱导的线粒体自噬缺陷在持续热量限制诱发的心脏病理变化中的保护作用。
Chronic caloric restriction triggers unfavorable alterations in cardiac function albeit responsible scenarios remain unclear. This work evaluated the possible involvement of
Akt2 in caloric restriction-evoked cardiac geometric and functional changes and responsible processes focusing on autophagy and mitophagy.
Akt2 knockout and WT mice were subjected to caloric restriction for 30 weeks prior to assessment of myocardial homeostasis. Caloric restriction compromised echocardiographic parameters (decreased LV wall thickness, LVEDD, stroke volume, cardiac output, ejection fraction, fractional shortening, and LV mass), cardiomyocyte contractile and intracellular Ca2+ capacity, myocardial atrophy, interstitial fibrosis and mitochondrial injury associated with elevated blood glucocorticoids, autophagy (LC3B, p62, Atg7, Beclin-1), and mitophagy (Pink1, Parkin, TOM20), dampened cardiac ATP levels, mitochondrial protein PGC1α and UCP2, anti-apoptotic protein Bcl2, intracellular Ca2+ governing components Na+-Ca2+ exchanger, phosphorylation of SERCA2a, mTOR (Ser2481) and ULK1 (Ser757), and upregulated Bax, phospholamban, phosphorylation of
Akt2, AMPK, and ULK1 (Ser555), the responses except autophagy markers (Beclin-1, Atg7), phosphorylation of AMPK, mTOR and ULK1 were negated by Akt2 ablation. Levels of CDK1 and DRP1 phosphorylation were overtly upregulated with caloric restriction, the response was reversed by
Akt2 knockout. Caloric restriction-evoked changes in cardiac remodeling and cardiomyocyte function were alleviated by glucocorticoid receptor antagonism, Parkin ablation and Mdivi-1. In vitro experiment indicated that serum deprivation or glucocorticoids evoked GFP-LC3B accumulation and cardiomyocyte dysfunction, which was negated by inhibition of Akt2, CDK1 or DRP1, whereas mitophagy induction reversed
Akt2 ablation-evoked cardioprotection. These observations favor a protective role of Akt2 ablation in sustained caloric restriction-evoked cardiac pathological changes via correction of glucocorticoid-induced mitophagy defect in a CDK1-DRP1-dependent manner.