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目的:通过ATP依赖的钾离子通道(KATP)亚基-Kir6.2基因敲除小鼠(Kir6.2KO)模型,研究线粒体ATP敏感钾离子通道mitoKATP对心肌线粒体和代谢酶的调控机制。方法:分别将野生型小鼠(WT平行对照组)和Kir6.2KO小鼠(实验组)分为假手术、主动脉横断缩窄(TAC)2周和4周各3个亚组。检测并比较各组心功能、心肌能量代谢酶基因表达水平、信号转导通路中叉头框O1(FOXO1)和转录因子PGC1α水平、线粒体比面积和嵴间距。结果:与平行WT组相比较,TAC前Kir6.2KO小鼠心肌PGC1α表达水平有所降低、FOXO1略提高,能量代谢酶中链乙酰辅酶A脱氢酶(MCAD)、肉碱软脂酰基转移酶1(CPT1)和细胞色素C氧化酶亚单位III(COXIII)明显负表达,线粒体比面积和线粒体嵴间距有所增加(8.45%和3.11%),表现为有氧代谢能力降低,线粒体代偿增生。TAC后2周时,Kir6.2KO组的心肌线粒体比面积没有变化(8.75%vs0.14%),而嵴间距增加幅度低于WT组(18.27%vs11.65%),线粒体失代偿。TAC后4周时,Kir6.2KO组FOXO1和PGC1α的蛋白或mRNA水平均显著降低,下游能量代谢酶mRNA和蛋白显著负调表达,心肌线粒体比面积降低幅度更大(-8.45%vs-23.6%),嵴间距变化与WT组相同(6.60%vs7.17%),心功能障碍更为明显,有氧代谢功能衰竭。结论:阻断mitoKATP降低了心肌线粒体对负荷增加时的增生和正调能量代谢酶的反应能力,这与FOXO1-PGC1α信号通路的弱化有关。说明mitoKATP通过FOXO1-PGC1α信号通路调节负荷过载小鼠心肌线粒体增殖和能量代谢功能。
OBJECTIVE: To investigate the regulatory mechanism of mitochondrial ATP-sensitive potassium channel mitoKATP on myocardial mitochondrial and metabolic enzymes through the ATP-dependent KATP subunit-Kir6.2 knockout mouse (Kir6.2KO) model. Methods: Wild-type mice (WT parallel control group) and Kir6.2 KO mice (experimental group) were divided into 3 groups: sham operation, 2 weeks and 4 weeks of aorta transection (TAC). The levels of cardiac function, myocardial energy metabolism enzyme gene expression, FOXO1 and PGC1α signal transduction pathways, mitochondrial specific surface area and crest distance were detected and compared. Results: Compared with the WT group, the expression of PGC1α in the myocardium of pre-TAC-Kir6.2 KO mice was decreased and FOXO1 slightly increased. The activities of acetyl-CoA dehydrogenase (MCAD), carnitine palmitoyl acyltransferase 1 (CPT1) and cytochrome C oxidase subunit III (COXIII) were significantly negatively expressed, mitochondrial specific area and mitochondrial cristae spacing increased (8.45% and 3.11%), manifested as reduced aerobic capacity, mitochondrial compensatory proliferation . At 2 weeks after TAC, there was no change in myocardial mitochondria area in Kir6.2KO group (8.75% vs0.14%), while the ridge crest distance was less than that in WT group (18.27% vs11.65%). At 4 weeks after TAC, protein and mRNA levels of FOXO1 and PGC1α were significantly decreased in Kir6.2 KO group, while mRNA and protein expression of downstream energy metabolism enzymes were significantly down-regulated. The mitochondria in myocardium decreased more significantly than that in the area (-8.45% vs-23.6% ), The change of crest distance was the same as WT group (6.60% vs7.17%), cardiac dysfunction was more obvious, and aerobic metabolic failure. Conclusion: Blocking mitoKATP reduces the ability of mitochondria to repress hyperplasia and up-regulation of energy metabolism enzymes at increased load, which is related to the weakened FOXO1-PGC1α signaling pathway. It shows that mitoKATP regulates myocardial mitochondrial proliferation and energy metabolism through the FOXO1-PGC1α signaling pathway.