Wang Qiurong, Ren Jun
Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA.
Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA; Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
Pharmacol Res. 2016 Sep;111:357-373. doi: 10.1016/j.phrs.2016.06.024. Epub 2016 Jun 27.
Insulin resistance is associated with cardiovascular diseases although the precise mechanisms remain elusive. Akt2, a critical member of the Akt family, plays an essential role in insulin signaling. This study was designed to examine the effect of trehalose, an mTOR-independent autophagy inducer, on myocardial function in an Akt2 knockout-induced insulin resistance model. Adult WT and Akt2 knockout (Akt2(-/-)) mice were administered trehalose (1mg/g/day, i.p.) for two days and were then given 2% trehalose in drinking water for two more months. Echocardiographic and myocardial mechanics, intracellular Ca(2+) properties, glucose tolerance, and autophagy were assessed. Apoptosis and ER stress were evaluated using TUNEL staining, Caspase 3 assay and Western blot. Autophagy and autophagy flux were examined with a focus on p38 mitogen activated protein kinase (MAPK), Forkhead box O (Foxo1) and Akt. Akt2 ablation impaired glucose tolerance, myocardial geometry and function accompanied with pronounced apoptosis, ER stress and dampened autophagy, the effects of which were ameliorated by trehalose treatment. Inhibition of lysosomal activity using bafilomycin A1 negated trehalose-induced induction of autophagy (LC3B-II and p62). Moreover, phosphorylation of p38 MAPK and Foxo1 were upregulated in Akt2(-/-) mice, the effect of which was attenuated by trehalose. Phosphorylation of Akt was suppressed in Akt2(-/-) mice and was unaffected by trehalose. In vitro findings revealed that the p38 MAPK activator anisomycin and the Foxo1 inhibitor (through phosphorylation) AS1842856 effectively masked trehalose-offered beneficial cardiomyocyte contractile response against Akt2 ablation. These data suggest that trehalose may rescue against insulin resistance-induced myocardial contractile defect and apoptosis, via autophagy associated with dephosphorylation of p38 MAPK and Foxo1 without affecting phosphorylation of Akt.
胰岛素抵抗与心血管疾病相关，尽管其确切机制仍不清楚。Akt2是Akt家族的关键成员，在胰岛素信号传导中起重要作用。本研究旨在研究海藻糖（一种不依赖mTOR的自噬诱导剂）对Akt2基因敲除诱导的胰岛素抵抗模型中心肌功能的影响。成年野生型（WT）和Akt2基因敲除（Akt2(-/-)）小鼠腹腔注射海藻糖（1mg/g/天）两天，然后在饮用水中添加2%海藻糖再持续两个月。评估超声心动图和心肌力学、细胞内Ca(2+)特性、葡萄糖耐量和自噬。使用TUNEL染色、Caspase 3检测和蛋白质印迹法评估细胞凋亡和内质网应激。重点研究p38丝裂原活化蛋白激酶（MAPK）、叉头框O（Foxo1）和Akt来检测自噬和自噬通量。Akt2基因缺失损害葡萄糖耐量、心肌形态和功能，伴有明显的细胞凋亡、内质网应激和自噬减弱，海藻糖治疗可改善这些影响。使用巴弗洛霉素A1抑制溶酶体活性可消除海藻糖诱导的自噬（LC3B-II和p62）。此外，Akt2(-/-)小鼠中p38 MAPK和Foxo1的磷酸化上调，海藻糖可减弱这种作用。Akt2(-/-)小鼠中Akt的磷酸化受到抑制，且不受海藻糖影响。体外研究结果显示，p38 MAPK激活剂茴香霉素和Foxo1抑制剂（通过磷酸化）AS1842856有效地掩盖了海藻糖对Akt2基因缺失提供的有益心肌细胞收缩反应。这些数据表明，海藻糖可能通过与p38 MAPK和Foxo1去磷酸化相关的自噬来挽救胰岛素抵抗诱导的心肌收缩缺陷和细胞凋亡，而不影响Akt的磷酸化。
