Parathyroid hormone (PTH) modulates lipid metabolism in the skeletal niche

项目总结/摘要 我实验室的长期目标是全面了解细胞内 代谢途径影响骨骼健康。在这个范围内，目前的项目旨在探索骨- 间歇性甲状旁腺激素（iPTH）通过其对细胞内脂质代谢的调节的合成代谢作用 骷髅龛骨质疏松症和骨质减少症是迟发性疾病， 美国人 . 除了经济负担外，与骨质疏松症相关的骨折通常会导致多发性骨折。 显著缩短寿命的合并症。虽然增加骨形成的合成代谢剂， PTH或PTH相关蛋白（PTHrP）有助于骨质疏松症的管理，患者仍然会遇到 不良副作用因此，有必要继续开发完善的治疗方案。因此，在本发明中， 该项目提出了PTH信号上调骨脂解的双重互补机制 骨髓脂肪细胞（BMAdipo），将脂质物质释放到骨骼龛中，同时也增强脂肪酸 成骨细胞中的氧化。考虑到BMAdipo与成骨细胞的密切关系， 治疗作用于BMAdipo以释放脂质物质，同时也“引发"成骨细胞利用这些脂质 作为能够支持骨形成的能量需求过程的机制。所以我们的 总体假设是PTH的骨合成代谢作用涉及刺激BMAdipo中的脂解， 增强成骨细胞中的脂肪酸氧化。我们将在两个具体目标中检验这一假设。第一个目标 (SA1)将决定PTH刺激的BMAdipo脂解支持PTH诱导的骨形成的能力， 无论是在体内还是体外。这将使用一种新的小鼠模型来完成，该模型由Co-I开发， 特异性抑制BMAdipo中的脂解作用。然后对这些小鼠进行卵巢切除（OVX）或假手术 并用PTH或载体对照治疗。将在研究结束时评估骨骼和代谢参数。 书房除了该实验之外，还将测定PTH处理后从BMAdipo释放的脂质物质。 使用液相色谱-质谱法（LC-MS）表征。第二个目标（SA 2）将定义 PTH通过调节细胞生物能量学改变成骨细胞脂质代谢的能力。13 C18油酸的示踪 将使用LC-MS进行脂肪酸测定，以确定成骨细胞中PTH治疗期间的脂肪酸代谢命运。 此外，将测量成骨细胞线粒体氧化磷酸化底物依赖性， PTH采用Seahorse XFe 96技术。最后，成骨细胞生物能量学将使用反向- 相高效液相色谱法（RP-HPLC）测定一磷酸腺苷（AMP）， 腺苷二磷酸（ADP）和ATP流量在控制条件下和在PTH刺激。总的来说， 本项目的目的是提高我们对PTH通过骨形成促进骨形成的能力的理解。 调节脂质代谢。该项目预计将产生重大的健康影响，因为它将 确定治疗探索的新领域，这对改善骨质疏松症的管理至关重要。

PROJECT SUMMARY/ ABSTRACT The long-term goal of my laboratory is to develop a comprehensive understanding of how intracellular metabolic pathways impact bone health. Within this scope the current project aims to explore the osteo- anabolic effects of intermittent parathyroid hormone (iPTH) via its modulation of lipid metabolism on cells within the skeletal niche. Osteoporosis and osteopenia are late-onset diseases affecting a staggering 54 million people in the U.S . In addition to the financial burden, osteoporosis-related fractures often lead to multiple comorbidities which significantly reduce longevity. While anabolic agents that increase bone formation such as PTH or PTH related protein’s (PTHrP) have aided in the management of osteoporosis, patients still experience adverse side-effects. Therefore, continued development of refined therapeutic options is necessary. As such, this project presents dual, complimentary mechanisms whereby PTH signaling up-regulates lipolysis in bone marrow adipocytes (BMAdipo), releasing lipid species into the skeletal niche, while also enhancing fatty acid oxidation in osteoblasts. Given the intimate proximity of BMAdipo to osteoblasts, it stands to reason that PTH treatment acts on both BMAdipo to liberate lipid species while also ‘priming’ the osteoblast to utilize these lipids as a mechanism capable of supporting the energy demanding process of bone formation. Therefore, our overarching hypothesis is that PTH’s bone anabolic actions involve stimulation of lipolysis in BMAdipo and enhanced fatty acid oxidation in osteoblasts. We will test this hypothesis in two specific aims. The first aim (SA1) will determine the ability of PTH-stimulated BMAdipo lipolysis to support PTH-induced bone formation, both in vivo and in vitro. This will be accomplished using a new mouse model, developed by the Co-I, designed to specifically inhibit lipolysis in BMAdipo. These mice will then be ovariectomized (OVX) or sham-operated on and be treated with PTH or vehicle control. Skeletal and metabolic parameters will be assessed at the end of the study. In addition to this experiment, lipid species released from BMAdipo upon PTH treatment will be characterized using liquid chromatography-mass spectrometry (LC-MS). The second aim (SA2) will define PTH’s ability to alter osteoblast lipid metabolism via modulation of cellular bioenergetics. Tracing of 13C18 oleic acid will be performed using LC-MS to determine fatty acid metabolic fate during PTH treatment in osteoblasts. Additionally, osteoblast mitochondrial oxidative phosphorylation substrate dependency will be measured during PTH using Seahorse XFe96 technology. Finally, osteoblast bioenergetics will be monitored using reversed- phase high-performance liquid chromatography (RP-HPLC) to determine adenosine monophosphate (AMP), adenosine diphosphate (ADP), and ATP flux under control conditions and during PTH stimulation. In summary, the goal of this project is to enhance our understanding of PTH’s ability to promote bone formation via the modulation of lipid metabolism. This project is expected to have substantial health-related influence as it will identify new areas for therapeutic exploration that are crucial to improve the management of osteoporosis.