Metabolism and Growth in a Teleost Fish Model of Diabetes Mellitus: Insulin Regulation in an Ectothermic Vertebrate

9600783凯利一种独特的糖尿病模型已经在一种海洋鱼类--奇异虎鱼身上出现。与其他动物的胰腺内分泌细胞(即产生胰岛素和胰升糖素的细胞)与外分泌细胞(即消化酶产生细胞)位于同一组织中的解剖安排不同，这种虎虎鱼只有一个胰腺内分泌器官，称为“胰岛”，其中包含纯粹的激素产生细胞。因此，虎鱼可以进行简单的外科“岛叶切除”，完全去除内分泌细胞，产生胰岛素依赖型糖尿病(IDDM)的直接症状。然而，与哺乳动物模型不同的是，在哺乳动物模型中，IDDM是由于胰岛素产生细胞((-细胞)的单一丧失而引起的，而虎鱼的胰岛切除同时去除了(-细胞和(-细胞)(胰高血糖素的来源)。在哺乳动物中，不受胰岛素挑战的“逆调节”高血糖素被认为是推动IDDM发病阶段高血糖的主要因素。然而，还没有可用的实验模型，在这种模型中，可以同时去除(和)细胞，以便直接测试这一假设。PI的目的是在虎鱼模型中表征胰升糖素在IDDM发病过程中的促糖尿病作用，并特别关注发生在肝脏和血液中的代谢机制。肾上腺糖皮质激素(皮质醇)是糖尿病哺乳动物发病后的一种重要的促糖尿病激素，其影响也将被研究。除了代谢干扰外，IX虎鱼还表现出强烈的糖尿病生长抑制作用，包括胰岛素样生长因子(IGF)生物活性的降低(身体生长积极的指标)和低分子IGF结合问题的显著增加，这可能与哺乳动物代谢敏感、IGF抑制的“IGFBP-1”有关。利用IGFBP-1类蛋白在IX goby中的这种明显的代谢调节，PI旨在表征该蛋白的内分泌/代谢调节及其生长调节作用，并尝试使用基于PCR的策略来克隆其基因。PI特别感兴趣的是，对这种蛋白质的测量是否可以作为天然和水产养殖鱼类种群的健康、生长状况和压力的方便指标。由于以前在低等脊椎动物中缺乏胰岛素缺乏的模型，关于胰岛素在体温过高的动物(“冷血”动物)中的生物学作用的研究仅限于对完整动物的激素注射研究。IX虎鱼模型将允许PI在吸热(“温血”)进化之前获得以前无法获得的新陈代谢调节的洞察。有人假设，吸热生理学的发展，就像哺乳动物和鸟类进化中所发生的那样，需要开发更有效的代谢调节系统，增加对胰岛素调节影响的依赖。在IX虾虎鱼中，PI发现外周肌肉组织中胰岛素可调节的葡萄糖运输变得对胰岛素产生抵抗，而IX虾虎鱼的胰岛素治疗使葡萄糖运输系统再次对胰岛素的作用做出反应。这些数据表明，胰岛素可能对鱼类葡萄糖转运蛋白具有与哺乳动物类似的双重调节作用，即对转运蛋白动态/活性的急性影响，对转运蛋白基因表达的长期影响。重要的是，这些数据还建立了一个可调节的实验系统，符合另一个特定的目标：表征虎鱼中胰岛素的调节和葡萄糖运输系统的细胞机制，特别是当它与吸热哺乳动物有关的时候；PI然后计划使用基于PCR的策略来克隆GLUT-4(哺乳动物主要的胰岛素调节的葡萄糖转运体)的虎鱼对应物。在拟议的研究中，将重点研究代谢和生长机制之间的相互关系，以便对这种外温体的生理系统有一个完整的了解。

9600783 Kelley A unique model of diabetes mellitus has been developed in a marine fish, the goby Gillichthys mirabilis. In contrast to the anatomical arrangement in other animals in which pancreatic endocrine cells (i.e., those producing insulin and glucagon) are located in the same tissue as exocrine cells (i.e., digestive enzyme-producing cells), this goby possesses a single pancreatic endocrine organ, called the "islet", which contains purely hormone-producing cells. The goby thereby allows for a simple surgical "isletectomy", which removes completely the endocrine cells and produces the outright symptomatology of insulin-dependent diabetes mellitus (IDDM). In contrast to mammalian models, however, in which IDDM results from the singular loss of the insulin-producing cells ((-cells), isletectomy in the goby removes simultaneously (-cells as well as (-cells (the source of glucagon). In mammals, "counterregulatory" glucagon, acting unchallenged by insulin, is believed to be a primary factor in driving the hyperglycemia during the onset phase of IDDM. There have been no experimental models available, however, in which both (- and (-cells can be removed in order to test this hypothesis directly. The PI aims to characterize the diabetogenic role of glucagon during IDDM onset in the goby model, with special attention given to the metabolic mechanisms occurring in the liver and blood. The influence of adrenal glucocorticoid (cortisol), a diabetogenic hormone important post-onset in diabetic mammals, will also be investigated. In addition to metabolic perturbation, the Ix goby exhibits a strong diabetic growth inhibition, including reductions in insulin-like growth factor (IGF) bioactivity (an indicator of positive somatic) growth) and a significant increase in a low molecular weight IGF-binding problem that may be related to the metabolically-sensitive, IGF-inhibitory "IGFBP-1" of mammals. Taking advantage of this apparent metabolic regulation of the IGFBP-1-like protein in the Ix g oby, the PI aims to characterize this protein's endocrine/metabolic regulation and its growth-regulatory role, and to attempt the cloning of its gene using a PCR-based strategy. The PI is particularly interested in whether measurement of this protein may serve as a convenient indicator of health, growth status, and stress in natural and aquacultured fish populations. Owing to the prior lack of a model of insulin deficiency in lower vertebrates, studies on the biological role of insulin in ectotherms ("cold-blooded" animals) have been limited to hormone injection studies on intact animals. The Ix goby model will allow the PI to gain previously-unattainable insight on metabolic regulation "before" the evolution of endothermy ("warm-bloodedness"). It has been hypothesized that the development of the physiology of endothermy, as has occurred in mammalian and avian evolution, necessitated the development of a more efficient metabolic regulatory system with an increased dependence on the regulatory influence of insulin. In the Ix goby, the PI has found that insulin-regulatable glucose transport ion peripheral muscle tissues becomes insulin resistant, and that insulin treatment of Ix gobies renders the glucose transport system once again responsive to insulin action. These data suggest that insulin may exert a dual regulation on fish glucose transporters comparable to that in mammals, i.e., acute effects on transporter dynamics/activity, long-term effects on transporter gene expression. Importantly, the data also establish a regulatable experimental system amenable to another specific aim: to characterize the insulin regulation and cellular mechanisms of the glucose transport system in the goby, especially as it relates to that of the endothermic mammal; the PI then plans to use a PCR-based strategy to clone the goby counterpart of glut-4 (the primary insulin-regulated glucose transporter of mammals). In the proposed studies, interrelationships between metabolic and growth mechanisms will be e mphasized, in order to gain an integrated picture of this ectotherm's physiological system.