G protein coupling of lipid metabolism in diabetic heart

I型和II型糖尿病都伴随着心肌底物利用的深刻变化，从利用几乎等量的葡萄糖和脂肪酸转变为以FA为底物的状态。心脏中的G蛋白在介导心肌电和收缩蛋白方面具有重要作用，这在一定程度上依赖于适当的膜微环境来实现其特定功能。在糖尿病状态下，脂质合成发生了深刻的变化，包括磷脂酰肌醇(Gq通过磷脂酶C偶联，导致IP3的产生)和纤溶酶原含量的变化，这对膜的流动性和动力学有显着影响。在过去的五年中，大量的证据表明糖尿病心肌中G蛋白轴的活性和功能发生了改变。这些变化包括β肾上腺素能受体数量的减少、GQ蛋白质量的增加、G蛋白受体-效应器偶联的改变、PKCepsilon活性的增加以及细胞内钙离子稳态的变化。因此，G信号的改变似乎有助于糖尿病心脏的病理生理表现的传播，或者是其基础。项目4的基本假设是，糖尿病心肌病的发生是由于GQ和GI蛋白介导的信号通路的异常刺激，导致细胞内磷脂酶、过氧化脂质代谢和脂质第二信使生成的改变。为了验证这一糖尿病心肌病变模型，我们将评估糖尿病小鼠心肌中G蛋白介导的信号转导增加或减少的功能和生化后遗症。特别是，我们将确定心脏中GQ和GI信号的减少是否抑制糖尿病小鼠心肌病变的发展。G蛋白信号将被GQ和GI家族成员的GTP酶激活蛋白RGS4所减弱。所涉及的特定G蛋白的鉴定将通过对单个Galpha亚单位基因的定向破坏来确定。此外，我们还将评估GQ信号的增加是否促进了糖尿病心肌病的发展。此外，我们将确定心脏中的GQ或GI信号转导是否促进PLA2的激活和脂质代谢的变化。最后，我们将研究心脏中的转导促进PLA2的激活和脂质代谢的变化。最后，我们将研究肌膜磷脂酶cPLA2-γ在糖尿病心肌病发病机制中的生理作用，并将确定G蛋白介导的信号是否调节该磷脂酶的激活。

Both Type I and Type II diabetes are accompanied by a profound switch in myocardial substrate utilization form one which utilizes nearly equal amounts of glucose and fatty acid to a state which predominantly employs FA for substrate. G-proteins in he heart have important effects in mediated the electrical and contractile proteins for myocardium which depend, in part, on an appropriate membrane microenvironment to carry out their specific functions. In the diabetic state profound changes in lipid synthesis occur including alterations in phosphatidylinositol (to which Gq is coupled through phospholipase C leading to IP3 generation) and in the content of plasmalogen which have dramatic effects on membrane fluidity and dynamics. During the last fie years substantial evidence has been accrued demonstrating the altered activity and function of the G-protein axis in diabetic myocardium. These include decreases in beta adrenergic receptor number, increases in Gq-protein mass, altered G-protein receptor-effector coupling, increases in PKCepsilon activity and changes in intracellular calcium ion homeostasis. Thus, it seems likely that altered G signaling contributes to, or underlies the propagation of the pathophysiology manifest in the diabetic heart. The primary hypothesis of Project 4 is that diabetic cardiomyopathy develops as a result of abnormal stimulation of Gq and Gi protein- mediated signaling pathways that leads to alterations in intracellular phospholipases, peroxisomal lipid metabolism and lipid second messenger generation. In order to test this model of diabetic cardiomyopathy we will evaluate the functional and biochemical sequelae of increased or decreased G protein-mediated signal transduction in diabetic murine myocardium. In particular, we will determine whether reduced Gq and Gi signaling in the heart inhibits the development of cardiomyopathy in diabetic mice. G protein signaling will be attenuated by use of RGS4, a GTPase activating protein for Gq and Gi family members. The identify of the specific G protein involved will be determined by targeted disruption of individual Galpha subunit genes. In addition, we will evaluate whether increased Gq signaling potentiates the development of diabetic cardiomyopathy. Furthermore, we will determine whether Gq or Gi signal transduction in heart promotes PLA2 activation and changes in lipid metabolism. Finally, we will examine the transduction in heart promotes PLA2 activation and changes in lipid metabolism. Finally, we will examine the physiological role of the sarcolemmal phospholipase cPLA2gamma, in the pathogenesis of diabetic cardiomyopathy and we will determine whether G protein-mediated signaling regulates activation of this phospholipase.