AMPK在体外循环诱发急性糖代谢紊乱调控中的作用及机制

Cardiopulmonary bypass (CPB) frequently induces patients' disorders of glucose metabolism which would promote with systemtic inflammation each other and severely affect patients' prognosis. The disorders of glucose metabolism are characterized by insulin resistance, stress hyperglycemia and so on. Phosphatidylinositol 3-kinase (PI3K) pathway is the major insulin regulatory pathway of glucose metabolism under physiological conditions, however, adenosine monophosphate-activated protein kinase (AMPK) pathway is also very important in regulating the glucose metabolism. In our former studies, we have found for the first time: ①Insulin- PI3K/Akt-Glut4 signaling pathway is inhibited in patients undergoing CPB, which is the main reason for disorders of glucose metabolism. While intensive insulin therapy can still ameliorate disorders of glucose metabolism in patients undergoing CPB. ②At the same time, expression and activity of AMPK are not influenced in patients undergoing CPB,and the expression and activity of AMPK increase in patients treated with intensive insulin therapy. All of above suggest that AMPK might play an important role in the regulation of glucose metabolism in patients undergoing CPB. However, the mechanism is unclear and needs to be further explored. To better regulate cardiopulmonary bypass-induced disorders of glucose metabolism, we intend to focus on AMPK's role in regulating glucose metabolism and its mechanisms in patients undergoing CPB. We plan to treat patients undergoing CPB with intensive insulin therapy or not, and observe patients' AMPK and its downstream molecular expression and activity changes in patients undergoing CPB at different time points of perioperation period. By activating or blocking the CPB animal models' AMPK pathway, we plan to observe myocardial glucose uptake and other glucose metabolism indicators and investigate AMPK's role in the regulation of glucose metabolism in patients undergoing CPB; Furthermore, we plan to use gene transfection and RNA interference to selectively upregulate or downregulate AMPK signaling pathway in CPB cell model. At last, we could illuminate the molecular mechanisms of AMPK signaling pathway in regulating glucose metabolism during CPB and find new therapeutic targets. And we could provide new therapy strategy for disorders of glucose metabolism induced by heart surgery and other critical illness.

人工心肺体外循环（CPB）易诱发心脏手术患者发生严重的急性糖代谢紊乱，导致细胞摄取和利用葡萄糖障碍，是CPB致机体损伤的核心机制之一，显著影响预后，但具体分子机制不明。我们研究发现生理状态下胰岛素调节细胞糖代谢主要通路-PI3K通路显著受抑，而对细胞能量调节也发挥重要作用的AMPK通路未受抑制，并且在胰岛素强化治疗后其表达、活性增加，同时糖代谢紊乱得以改善。因此，我们假设在CPB致PI3K通路受抑时，AMPK通路在细胞糖代谢调控中发挥关键作用，调控AMPK表达可以有效控制CPB糖代谢紊乱。本研究拟围绕上述科学假说，在CPB动物模型和细胞模型中干预AMPK通路，结合心肌特异性AMPK基因敲除小鼠，观察心肌葡萄糖利用等指标，明确AMPK通路是CPB时细胞糖代谢调控以及胰岛素强化治疗中的关键机制之一。本研究将为防治CPB引发的糖代谢紊乱，降低CPB所致机体损伤，提供新的治疗靶点和思路。

根据实验目的和标书研究内容，研究团队首先建立体外循环犬和大鼠模型，通过检测体外循环前和主动脉开放后不同时间点的血糖和胰岛素水平，发现体外循环可以引起体外循环后的血糖和胰岛素水平升高，以及胰岛素抵抗指数的升高 (P<0.05)。进一步研究发现，体外循环降低了胰岛素诱导的心肌葡萄糖摄取(P<0.05)。PET/CT检查心肌对 18F-FDG 的摄取进一步验证以上的研究。研究中发现受损的心肌葡萄糖摄取和心肌ATP生成降低与体外循环后的心肌功能下降密切相关。在体外循环损伤心肌葡萄糖摄取的机制研究中，我们发现心肌Akt的失活损伤了体外循环后心肌Glut-4的转运。SC79激活Akt后可以通过增加心肌葡萄糖摄取和ATP浓度改善体外循环心功能；研究中发现，AICAR激活AMPK可以明显提高心肌细胞在CPB后的糖摄取，改善心脏功能。AICAR是通过激活AMPK-AS160-GLUT-4改善急性心脏胰岛素抵抗；大鼠体内心肌转染AS160-4P基因，进一步证明AICAR通过活性AMPK-AS160-GLUT4改善心肌损伤和心脏功能障碍。 我们通过原代培养的大鼠心肌，验证CPB对心肌细胞糖代谢的影响及其分子机制。本研究将为防治CPB引发的糖代谢紊乱，降低CPB所致机体损伤，提供新的治疗靶点和思路。