TRANSMEMBRANE SIGNALLING IN GENETIC OBESITY

本研究的目的是了解体重的机制 调控 腺苷受体或GTP结合蛋白，其作为 这些受体的转换器，可能是重要的正常调节， 脂质储存，并可能在某些形式的肥胖中改变。 述的遗传 肥胖（fa/fa）Zucker大鼠，其似乎在以下方面表现出异常： 腺苷受体信号传导和Gi功能，将用作动物 模型 Gi是与异源三聚体GTP结合密切相关的家族之一 在跨膜信号传导中起中间体作用的蛋白质。 遗传性肥胖动物和由各种大脑造成肥胖的动物 病变表现出一系列共同的症状。 其中包括胰岛素 抵抗力，不同程度的高胰岛素血症，非寒战性受损 产热和缓慢的去甲肾上腺素周转。 许多这些症状 可能归因于与A1腺苷受体结合的过度激动剂 在肌肉、棕色脂肪、白色脂肪和交感神经末梢中。 胰岛素 肥胖Zucker大鼠骨骼肌条的典型阻力， 被A1腺苷受体拮抗剂逆转，并通过预先治疗 百日咳毒素 该实验室最近的研究表明， 激素刺激脂肪分解，Zucker大鼠白色脂肪细胞典型特征 可以用腺苷受体拮抗剂逆转。 隔离的等离子体 来自肥胖动物的膜表现出增强的GTP依赖性和腺苷 腺苷酸环化酶的受体激动剂依赖性抑制，与 瘦的动物。 然而，最近的研究表明， 受体或腺苷酸环化酶的量。 令人惊讶的低水平Gi 与瘦的相比，肥胖的细胞膜中发现了。 建议的目的 研究的目的是确定差异的结构基础， 瘦和肥胖动物A1腺苷受体活性。 研究是 设计用于重建来自具有正常Gi的肥胖动物的受体， 反之亦然。 计划对分离的受体进行结构研究， Gi，其包括磷酸化、糖基化， 酰化或氨基酸序列的改变，由于蛋白水解或 突变 将获得受体的cDNA以确定受体的表达。 原始编码氨基酸序列。 将脂肪细胞置于培养物中 以确定激素环境对受体功能的影响。 到 测定A1腺苷受体活性水平对全身的影响 代谢肥胖和瘦Zucker大鼠将长期用 激动剂或拮抗剂。 葡萄糖耐量、胰岛素 水平，血清甘油周转以及整体体重增加应 提供了腺苷受体重要性的指示， 能量存储与利用的调节器。

The objective of this study is to understand the mechanisms of body weight regulation. Adenosine receptors or the GTP binding proteins, which act as transducers for these receptors, may be important in normal regulation of lipid storage and may be altered in some forms of obesity. The genetically obese (fa/fa) Zucker rat, which appears to exhibit abnormalities in adenosine receptor signalling and Gi function, will be used as an animal model. Gi is one of a closely related family of heterotrimeric GTP binding proteins which function as intermediates in transmembrane signalling. Genetically obese animals and animals rendered obese by a variety of brain lesions exhibit a common array of symptoms. These include insulin resistance, varying degrees of hyperinsulinemia, impaired non-shivering thermogenesis, and slow norepinephrine turnover. Many of these symptoms might be ascribed to excessive agonist binding to the A1 adenosine receptor in muscle, brown fat, white fat and sympathetic nerve endings. The insulin resistance, typical of skeletal muscle strips from obese Zucker rats, can be reversed with an A1 adenosine receptor antagonist and by prior treatment with pertussis toxin. Recent studies in this laboratory show that impaired hormone stimulated lipolysis, typical of white adipocytes of Zucker rats can be reversed with an adenosine receptor antagonist. Isolated plasma membranes from obese animals exhibit enhanced GTP dependent and adenosine receptor agonist dependent inhibition of adenylate cyclase, compared to lean animals. However, recent studies reveal no differences in amounts of receptor or amounts of adenylate cyclase. Surprisingly low levels of Gi are found in obese membrane compared to lean. The aim of the proposed studies is to determine the structural basis for the difference between lean and obese animals in A1 adenosine receptor activity. Studies are designed to reconstitute receptors from obese animals with normal Gi and visa versa. Structural studies are planned for the isolated receptor and Gi which include assays for changes in phosphorylation, glycosylation, acylation or alterations of amino acid sequence, due to proteolysis or mutation. The cDNA of the receptor will be obtained to determine the original coded amino acid sequence. Adipocytes will be placed in culture to determine the effect of hormonal milieu on receptor function. To determine the effect of A1 adenosine receptor activity levels on whole body metabolism obese and lean Zucker rats will be chronically treated with either agonist or antagonists. Measurements of glucose tolerance, insulin levels, serum glycerol turnover as well as overall weight gain should provide an indication of the importance of the adenosine receptors as regulators of energy storage vs. utilization.