Increasing glycolysis in the diabetic heart is cardioprotective and improves glucose tolerance

这项建议的目标是确定在其限速步骤增加心脏糖酵解是否可以 减轻糖尿病心肌病(DC)，提高全身葡萄糖耐量。DC是一个主要的公共卫生问题 这一问题在1型和2型糖尿病中都会出现，并由多种因素调节。其中最重要的是 是代谢灵活性的丧失，这是心脏吸收和代谢可用循环的能力 营养素。健康的心脏主要使用脂肪酸，但它可以转变为葡萄糖代谢，以应对 喂食。然而，糖尿病患者的心脏几乎完全依赖于脂肪酸氧化，如果是慢性的，这 导致线粒体功能障碍，氧化应激，最终导致DC。在恢复正常心脏的同时 代谢具有治疗潜力，目前还没有治疗方法来使代谢不灵活正常化。我们 假设增加糖酵解可以使代谢不灵活正常化并减轻DC。我们一直在测试这一点 假说使用通过表达一种基因增强心脏葡萄糖代谢的小鼠(GlycoHi小鼠) 糖酵解调节剂的组成活性形式，磷酸果糖激酶-2(PFK-2)。我们发现：GlycoHi小鼠 对饮食诱导的心脏舒张性功能障碍具有抵抗力；GlycoHi心脏线粒体能力增强 使用丙酮酸，这表明代谢灵活性增加；雌性GlycoHi小鼠改善了系统 糖耐量和抵抗HFD的影响。这支持了我们的假设，即增加心脏PFK-2 运动可以减轻DC，并对全身血糖调节有好处。我们的首要目标是测试 假设增加心脏糖酵解可改善代谢灵活性，以应对HFD或1型糖尿病。 对照组和GlycoHi小鼠将患上HFD或诱发1型糖尿病。我们将确定心脏 蛋白质组学和代谢组学的功能和代谢图谱。新陈代谢灵活性将以 成年心肌细胞的放射性标记分析。目标2将验证增加心脏糖酵解的假设 在糖尿病条件下维持线粒体功能。我们将询问糖尿病患者的线粒体功能 (T1D和T2D)对照GlycoHi和PFK-2基因敲除小鼠。我们还将确定糖酵解的增加如何 能够维持丙酮酸脱氢酶活性。目标3将确定增长的机制 心脏糖酵解改善糖尿病GlycoHi小鼠的全身葡萄糖耐量。我们将区分 使用代谢笼增加能量消耗，并增加心脏、骨骼肌、 和脂肪组织。我们还将检验这一假设，即这种影响是通过脂肪细胞的变化来调节的 分化和生物能量学。糖尿病的发生持续增加，心脏病和心脏病 失败是导致这一人群死亡的主要原因。目前尚不清楚增加的心脏糖酵解是否会 缓解DC的治疗潜力。这些结果将推动未来的研究，以检验 靶向pfk-2使心脏代谢灵活性和葡萄糖稳态正常化的治疗潜力。

The goal of this proposal is to identify whether increasing cardiac glycolysis at its rate-limiting step can mitigate diabetic cardiomyopathy (DC) and improve whole body glucose tolerance. DC is a major public health issue that arises in both type 1 and type 2 diabetes and is mediated by numerous factors. Chief amongst them is the loss of metabolic flexibility, which is the capacity of the heart to take up and metabolize available circulating nutrients. The healthy heart primarily uses fatty acids, but it can shift to glucose metabolism in response to feeding. However, with diabetes the heart relies almost exclusively on fatty acid oxidation and if chronic, this leads to mitochondrial dysfunction, oxidative stress, and ultimately DC. While restoring proper cardiac metabolism has therapeutic potential, there are currently no treatments to normalize metabolic inflexibility. We posit that increasing glycolysis can normalize metabolic inflexibility and mitigate DC. We have been testing this hypothesis using mice that have enhanced cardiac glucose metabolism (GlycoHi mice) via the expression of a constitutively active form of the glycolytic regulator, phosphofructokinase-2 (PFK-2). We found that: GlycoHi mice are resistant to diet-induced cardiac diastolic dysfunction; GlycoHi heart mitochondria have an enhanced capacity to use pyruvate, indicative of increased metabolic flexibility; and female GlycoHi mice have improved systemic glucose tolerance and are resistant to HFD effects. This supports our hypothesis that increasing cardiac PFK-2 activity can mitigate DC and have beneficial effects on whole body glucose regulation. Our first Aim is to test the hypothesis that increasing cardiac glycolysis improves metabolic flexibility in response to HFD or type 1 diabetes. Control and GlycoHi mice will be subjected to HFD or induced with type 1 diabetes. We will determine cardiac function and metabolic profile by both proteomics and metabolomics. Metabolic flexibility will be measured in adult cardiomyocytes using a radiolabeled assay. Aim 2 will test the hypothesis that increasing cardiac glycolysis sustains mitochondrial function under diabetic conditions. We will interrogate mitochondrial function in diabetic (T1D and T2D) control GlycoHi, and PFK-2 knockout mice. We will also determine how the increase in glycolysis is able to sustain pyruvate dehydrogenase activity. Aim 3 will determine the mechanisms by which increasing cardiac glycolysis improves whole body glucose tolerance in diabetic GlycoHi mice. We will discern between increased energy expenditure, using metabolic cages, and increased insulin sensitivity in heart, skeletal muscle, and adipose tissue. We will also test the hypothesis that the effects are mediated through changes in adipocyte differentiation and bioenergetics. The occurrence of diabetes continues to increase, and heart disease and heart failure are leading causes of death in this population. It is not known whether increasing cardiac glycolysis has therapeutic potential in mitigating DC. These results will be an impetus for future studies that examine the therapeutic potential of targeting PFK-2 to normalize cardiac metabolic flexibility and glucose homeostasis.