Thyrotropin Receptor, Thyrotropin and Mechanisms of Bone Loss

促甲状腺素受体、促甲状腺素与骨丢失机制

• 批准号: 9317142
• 负责人: TERRY Francis DAVIES
• 金额: $ 62.7万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2021-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9317142
• 关键词: Affect; Affinity; Agonist; American; Anterior Pituitary Gland; Anterior Pituitary Hormones; Binding; Bone Diseases; Bone Marrow Cells; Bone Resorption; Bone remodeling; Cells; Clinical; Clinical Research; Closure by clamp; Coculture Techniques; Data; Defect; Dominant-Negative Mutation; Dose; Excision; Flow Cytometry; Fracture; Genes; Genetic; Health; Hormone replacement therapy; Hyperthyroidism; Implant; In Vitro; Incidence; Injectable; Injection of therapeutic agent; Mediating; Mediation; Mesenchymal; Methimazole; Modeling; Molecular; Mus; Myocardial Infarction; Osteoblasts; Osteoclasts; Osteogenesis; Osteoporosis; Osteoporotic; Ovariectomy; Patients; Pharmacology; Phenotype; Pituitary Hormones; Postmenopause; Prevention; Production; Rattus; Replacement Therapy; Reproducibility; Role; Serum; Signal Transduction; Skeleton; Specificity; Stroke; Stromal Cells; TNF gene; The Sun; Thyroid Function Tests; Thyroid Gland; Thyroid Hormone Receptor Beta; Thyroid Hormones; Thyrotropin; Thyrotropin Receptor; Tumor Necrosis Factor Receptor; United States; Woman; autoimmune thyroid disease; bone; bone cell; bone loss; bone mass; cellular targeting; cohort; cytokine; experimental study; follow-up; fracture risk; malignant breast neoplasm; men; mouse model; mutant; nanomolar; novel; novel strategies; osteoclastogenesis; overexpression; permissiveness; prevent; restoration; skeletal; small molecule

PROJECT SUMMARY In 2003, we showed that the anterior pituitary hormone thyrotropin (a.k.a. TSH), hitherto known to promote thyroid hormone secretion, is a potent direct regulator of bone mass (Abe et al, Cell, 2003, PMID: 14567913)1. This finding underscored a potential role for low circulating TSH levels in causing the bone loss that has been recognized in patients with hyperthyroidism for over a century2, and, by tradition, has been attributed solely to thyroid hormone excess. We found instead that Tsh receptor-deficient Tshr-/- mice had profound osteoporosis, even when rendered euthyroid1. Importantly, we showed more recently that bone loss in Tshr-/- mice rendered hyperthyroid significantly exceeded that in wild type hyperthyroid mice (Baliram et al, J Clin Invest, 2012, PMID: 22996689)3 – this finding not only confirmed a direct permissive action of Tshr deficiency on bone, but also buttressed multiple clinical studies showing a tight and highly reproducible correlation between low TSH levels, bone loss, and a high fracture risk in cohorts of hyperthyroid patients worldwide4-24. Furthermore, we found that the osteoclastogenic cytokine, Tnfα, was grossly elevated in Tshr-/- mice, and that its genetic deletion rescued the skeletal phenotype of Tshr deficiency (Hase et al, PNAS, 2006, PMID: 16908863; Sun et al, PNAS, 2013, PMID: 23716650)25,26. This led to the question: which cell – osteoblast or osteoclast – drives the effect, and which of the two Tnf receptors, Tnfrsf1a or Tnfrsf1b, mediate the action of Tnfα in Tshr deficiency? Specific Aim 1 will study mice in which the Tshr is deleted selectively in osteoblasts or osteoclasts, as well as double mutants in which both the Tshr and either Tnfrsf1a or Tnfrsf1b are deleted. Complementary co-culture experiments will determine if osteoblastic Tnfα mediates the hyper-resorption in Tshr-/- mice. A second corpus of data, confirmed by other groups27-33, showed that Tsh displays both anti- resorptive and anabolic actions1,34-37. For example, intermittent low dose Tsh injections restored the lost bone 7 months post-ovariectomy, importantly without elevating T4 levels (Sun et al, PNAS, 2008, PMID: 18332426)37. A follow-up question thus arises: is the Tshr a druggable target? Towards finding an answer, we will utilize both genetic and pharmacological approaches. In Specific Aim 2, we will examine whether high Tsh levels are anabolic using mice in which the expression of dominant-negative Trβ337 in the thyrotrope clamps Tsh at ~30-fold higher circulating levels. In Specific Aim 3, we will study the effects of a small molecule activator of the Tshr, MS438, which, we have found, binds Tshrs selectively and with a nanomolar affinity (Latif et al, Thyroid, 2015, PMID: 25333622)38. We also find that MS438 displays pro-osteoblastic and anti-osteoclastic actions in vitro, and does not elevate serum T4. We will thus inject mice with MS438 immediately (‘prevention’) or 7-months following (‘restoration’) ovariectomy to determine if it can prevent bone loss and/or restore the lost bone. Together, these studies should not only allow an in-depth understanding of Tsh action on bone, but also provide proof-of-concept for a new approach that targets the skeletal Tshr.

项目总结 2003年，我们发现垂体前叶激素促甲状腺激素(又名：促甲状腺激素)。TSH)，迄今已知促进 甲状腺激素分泌，是骨量的有力直接调节(Abe等人，细胞，2003年，PMID：14567913)1。 这一发现强调了低循环TSH水平在导致骨丢失中的潜在作用 在甲状腺功能亢进症患者中被发现已有一个多世纪了，按照传统，它仅被归因于 甲状腺激素过多。相反，我们发现TSH受体缺陷的TSHR-/-小鼠患有严重的骨质疏松症， 即使是在甲状腺功能正常的情况下也是如此。重要的是，我们最近显示，TSHR-/-小鼠的骨丢失呈现 甲亢显著超过野生型甲亢小鼠(Baliram等人，J Clin Invest，2012， PMID：22996689)3--这一发现不仅证实了促性腺激素释放激素缺乏对骨骼的直接允许作用，而且 还支持了多项临床研究，表明低TSH与低TSH之间存在紧密且高度可重复性的相关性 全世界甲亢患者队列中的水平、骨丢失和高骨折风险4-24。此外，我们 研究发现，破骨细胞因子肿瘤坏死因子α在Tshr-/-小鼠中显著升高，其基因 缺失挽救了TSHR缺乏症的骨骼表型(Hase等人，PNAS，2006年，PMID：16908863；Sun等人 美国国家统计局，2013年，PMID：23716650)25，26。这就引出了一个问题：哪种细胞--成骨细胞或破骨细胞--驱动 两种肿瘤坏死因子受体Tnfrsf1a或Tnfrsf1b中的哪一种介导肿瘤坏死因子α在TSHR中的作用 缺乏症？特定目标1将研究TSHR在成骨细胞中选择性缺失或 破骨细胞，以及TSHR和Tnfrsf1a或Tnfrsf1b均缺失的双突变体。 补充性共培养实验将确定成骨细胞肿瘤坏死因子α是否介导了 TSHR-/-小鼠。经其他组27-33证实的第二组数据显示，TSH既表现出抗- 吸收和合成代谢作用1，34-37。例如，间歇性低剂量TSH注射修复了丢失的骨骼 卵巢切除后7个月，重要的是没有升高T4水平(Sun等人，PNAS，2008，PMID： 18332426)37.这样就产生了一个后续问题：TSHR是一个可下药的靶点吗？为了找到答案，我们 将同时利用遗传和药理学方法。在具体目标2中，我们将检查是否高 促甲状腺激素水平是合成代谢的，在小鼠中，显性阴性的Trβ337在促甲状腺激素中的表达 将TSH夹在大约30倍的循环水平上。在具体目标3中，我们将研究一个小的 TSHR的分子激活剂MS438，我们已经发现，它选择性地与TSHR结合，并与纳米分子结合 亲和力(拉蒂夫等人，甲状腺，2015年，PMID：25333622)38.我们还发现，MS438显示出促成骨细胞和 体外有抗破骨作用，且不升高血清T4。因此，我们将给小鼠注射MS438 立即(“预防”)或在卵巢切除(“修复”)后7个月，以确定它是否可以防止骨质 丢失和/或恢复丢失的骨骼。总而言之，这些研究不仅应该让我们深入了解 TSH对骨骼的作用，但也为针对骨骼TSHR的新方法提供了概念验证。