Role of Deiodinases in Thyroid Hormone Homeostasis

描述(由申请人提供)：项目摘要：甲状腺激素(T3)调节生长、发育和代谢率。甲状腺激素(T4)必须被1型和2型脱碘酶(D1和D2)激活才能产生T3。D1和3型脱碘酶(D3)也可以通过去除额外的碘来灭活T3。因此，这些酶控制着T3的利用。这一建议的目的是了解这些酶在彼此和中枢甲状腺轴的背景下的相互作用，以便维持适合情况的甲状腺激素浓度和受体占有率。为了进一步了解这些网络，我们创造了C3H-D2KO小鼠，其中Dio2基因的靶向破坏被回交到遗传低D1(1/10正常水平)的C3H小鼠中。令人惊讶的是，这些小鼠保持了正常的血清T3水平，尽管T4和TSH增加了。在具体目标1中，我们将评估这些小鼠的组织特异性甲状腺状况，确定它们用来实现正常血清T3浓度的机制，并评估它们在受到低碘饮食挑战时的补偿能力。在具体目标2中，我们将调查体脂增加30%的原因，并评估他们对高脂肪饮食的反应。在具体目标3中，我们将利用二维差示凝胶电泳结合质谱仪(2D DICE MS)和酵母双杂交系统分离D3相互作用的蛋白质，目的是将D3细胞生物学与生理学联系起来。此外，我们将评估由2-D DICE MS鉴定的第一个D3相互作用蛋白是否作为D3的还原辅助因子。与NIDDK任务相关：这项提议将支持与内分泌学、能量平衡、发育和新陈代谢领域相关的基础研究。与公共健康相关：甲状腺激素(T3)对胎儿和新生儿的正常生长是必需的，而在成年人中，它是新陈代谢和能量消耗的关键调节因素。这项研究将研究激活和失活T3的酶水平的变化如何使正确数量的T3在各种不同的环境条件下存在。了解这种平衡是如何维持的，与生活在慢性缺碘地区的约10亿人的健康有关，对于确定当前肥胖流行以及糖尿病和心脏病等相关疾病的潜在原因和治疗方法非常重要。

DESCRIPTION (provided by applicant): Project Summary: Thyroid hormone (T3) regulates growth, development, and metabolic rate. Thyroxine (T4) must be activated by the type 1 and 2 deiodinases (D1 and D2) to produce T3. D1 and the type 3 deiodinase (D3) can also inactivate T3 by removal of an additional iodine. Thus, these enzymes control T3 availability. The goal of this proposal is to understand the interplay of these enzymes in context of each other and the central thyroidal axis such that situational-appropriate thyroid hormone concentrations and receptor occupancy are maintained. To further understand these networks, we created the C3H-D2KO mouse where the targeted disruption of the Dio2 gene is backcrossed into C3H mice with genetically low D1 (1/10 normal levels). Surprisingly, these mice maintain normal serum T3 levels, although T4 and TSH are increased. In Specific Aim 1 we will evaluate the tissue-specific thyroid status of these mice, define the mechanisms they use to achieve normal serum T3 concentrations, and evaluate their ability to compensate when challenged by a low iodine diet. In Specific Aim 2 we will investigate the causes of a 30% increase in body fat, and evaluate their response to a high fat diet. In Specific Aim 3, we will isolate D3 interacting proteins using 2 dimensional differential gel electrophoresis combined with mass spectrophotometry (2-D DICE MS) and the yeast two-hybrid system, with the goal of linking D3 cell biology to physiology. Further, we will assess if the first D3 interacting protein identified by 2-D DICE MS acts as a reducing co-factor for D3. Relevance to NIDDK Mission: This proposal will support basic research related to the fields of endocrinology, energy balance, development and metabolism. Relevance to Public Health: Thyroid hormone (T3) is necessary for proper fetal and neo-natal growth, while in adults it is a key regulator of metabolism and energy expenditure. This research will study how changes in levels of the enzymes that activate and inactivate T3 allow the correct amount of T3 to be present under a variety of different environmental conditions. Understanding how this balance is maintained is relevant to the health of the estimated 1-billion people living in areas of chronic iodine deficiency, and is important in identifying potential causes and treatments for the current obesity epidemic and the related diseases of diabetes, and heart disease.