G protein coupling of lipid metabolism in diabetic heart

G蛋白偶联糖尿病心脏脂质代谢

• 批准号: 6591380
• 负责人: ANTHONY JUSTIN MUSLIN
• 金额: $ 34.15万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6591380
• 关键词: G protein; beta adrenergic receptor; biological signal transduction; diabetic cardiomyopathy; enzyme induction /repression; fatty acid metabolism; gene targeting; guanosinetriphosphatase activating protein; laboratory mouse; lipid metabolism; peroxisome; phospholipase A2; phospholipase C; second messengers

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.

I 型和 II 型糖尿病都伴随着心肌底物利用的深刻转变，从利用几乎等量的葡萄糖和脂肪酸到主要利用 FA 作为底物的状态。心脏中的 G 蛋白在介导心肌的电蛋白和收缩蛋白方面具有重要作用，这部分依赖于适当的膜微环境来执行其特定功能。在糖尿病状态下，脂质合成发生深刻变化，包括磷脂酰肌醇（Gq 通过磷脂酶 C 与其偶联，导致 IP3 生成）和缩醛磷脂含量的变化，这对膜的流动性和动力学具有显着影响。在过去五年中，大量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 信号传导的改变似乎可能促进糖尿病心脏中病理生理学的传播，或成为其传播的基础。项目 4 的主要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异常刺激导致细胞内磷脂酶、过氧化物酶体脂质代谢和脂质第二信使生成的改变。为了测试这种糖尿病心肌病模型，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 信号传导的减少是否会抑制糖尿病小鼠心肌病的发展。 G 蛋白信号传导将通过使用 RGS4 减弱，RGS4 是 Gq 和 Gi 家族成员的 GTP 酶激活蛋白。所涉及的特定 G 蛋白的鉴定将通过对单个 Galpha 亚基基因的定向破坏来确定。此外，我们将评估 Gq 信号传导的增加是否会加剧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 激活和脂质代谢的变化。最后，我们将检查心脏中的转导促进 PLA2 激活和脂质代谢的变化。最后，我们将研究肌膜磷脂酶 cPLA2gamma 在糖尿病心肌病发病机制中的生理作用，并确定 G 蛋白介导的信号传导是否调节该磷脂酶的激活。