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标题： Lin28a protects against cardiac ischemia/reperfusion injury in diabetic mice

讲者：张明明

单位：第四军医大学第一附属医院西京医院

关键词：

Diabetes Ischemia/reperfusion injury Lin28a

播放： 1577

论文摘要：

OBJECTIVES The insulin-PI3K-mTOR and insulin-PI3K-AMPK pathways exhibit a variety of cardiovascular activities including protection against I/R injury. Lin28a enhanced glucose uptake and insulin-sensitivity via insulin-PI3K-mTOR signaling pathway. However, the role of lin28a on experimental cardiac I/R injury in diabetic mice are not well understood.

Methods Diabetic mice underwent 30 minutes of ischemia followed by 3h of reperfusion. Animals were randomized to be treated with lentivirus carrying lin28a siRNA (siLin28a) or lin28a cDNA (Lin28a) 72h before coronary artery ligation. Myocardial infarct size, cardiac function, cardiomyocyte apoptosis and mitochondria morphology in diabetic mice who underwent cardiac I/R injury were compared between groups. Primary cardiomyocytes which were isolated from neonatal mouse were randomized to be treated with lentivirus carrying Lin28a siRNA, Lin28acDNA 72h before H/R (9h/2h). Cardiomyocytes biomarkers release (LDH and CK), cardiomyocytes apoptosis, mitochondria biogenesis and morphology, intracellular reactive oxygen species (ROS) production, ATP content and inflammatory cytokines levels after H/R injury in high glucose/high fat conditions were compared between groups. The target proteins of lin28a were examined by western blot analysis.

Results Lin28a overexpression significantly reduced myocardial infarct size, improved left ventricular ejection fraction (LVEF), decreased myocardial apoptotic index and alleviated mitochondria cristae destruction in diabetic mice underwent cardiac I/R injury. Lin28a knockdown exacerbated cardiac I/R injury as evidenced by increased infarct size, decreased LVEF, increased apoptotic index and aggravated mitochondria cristae destruction. Interestingly, pretreatment with rapamycin abolished the beneficial effects of lin28a overexpression. Lin28a overexpression increased, while Lin28a knockdown decreased the expression of IGF1R, p-Akt, p-mTOR and p-p70s6k after cardiac I/R injury in diabetic mice. Rapamycin pretreatment abolished the effects of increased p-mTOR and p-p70s6k expression exerted by lin28a overexpression. Our results revealed that Lin28a cDNA transfection (overexpression) significantly inhibited cardiomyocyte apoptotic index, improved mitochondria biogenesis, increased ATP production and reduced ROS production as compared with the H/R group in HG/HF conditions. Lin28a siRNA transfection (knockdown) rendered the cardiomyocytes more susceptible to H/R injury as evidenced by increased apoptotic index, impaired mitochondrial biogenesis, decreased ATP production and increased ROS level. Interestingly, these effects of Lin28a were blocked by pretreatment with the PI3K inhibitor wortmannin. Lin28a overexpression increased, while Lin28a knockdown inhibited IGF1R, Nrf-1,Tfam, p-IRS-1, p-Akt, p-mTOR, p-p70s6k, p-AMPK expression levels after H/R injury in HG/HF conditions. Moreover, pretreatment with wortmannin abolished the effects of Lin28a on the expression levels of p-AKT, p-mTOR, p-p70s6k, p-AMPK.

Conclusions This study indicates that lin28a overexpression reduces infarct size, improves cardiac function, decreases cardiomyocyte apoptosis index and alleviates cardiomyocyte mitochondria impairment after cardiac I/R injury in diabetic mice. The present results suggest that Lin28a inhibits cardiomyocytes apoptosis by enhancing mitochondrial biogenesis and function under high glucose/high fat conditions. The mechanism responsible for the effects of Lin28a is associated with the insulin-PI3K-mTOR and insulin-PI3K-AMPK dependent pathways.