Osteoblastic Respiration and IRS Signaling

成骨细胞呼吸和 IRS 信号传导

• 批准号: 8823029
• 负责人: CLIFFORD JAMES ROSEN
• 金额: $ 23.42万
• 依托单位: MAINEHEALTH
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8823029
• 关键词: AKT Signaling Pathway; ATP Synthesis Pathway; Abbreviations; Affect; Attenuated; Binding; Bioenergetics; Biogenesis; Biology; Bone Density; Bone Diseases; C3H/HeJ Mouse; Calvaria; Cell Respiration; Cells; Collagen; Complex; Data; Defect; Energy Metabolism; Enzymes; Exhibits; Gene Expression; Generations; Genes; Glycolysis; Glycolysis Induction; Goals; Hormones; IRS1 gene; Image; Impairment; In Situ; In Vitro; Inbred Strain; Inbred Strains Mice; Individual; Insulin-Like Growth Factor I; Lead; Longevity; Measures; Mediating; Membrane; Membrane Potentials; Membrane Proteins; Microscopy; Mitochondria; Mus; Nature; Neonatal; Nuclear; Nutrient; Osteoblasts; Osteocalcin; Osteogenesis; Osteoid; Osteoporosis; Oxidative Phosphorylation; Oxygen Consumption; Parathyroid gland; Pathway interactions; Peptides; Proto-Oncogene Proteins c-akt; Raptors; Relative (related person); Respiration; Role; Signal Pathway; Signal Transduction; Stress; Sum; Techniques; Testing; Therapeutic Agents; Time; Work; bone; bone cell; bone mass; cellular imaging; density; energy balance; high risk; human FRAP1 protein; in vivo; insight; loss of function mutation; mineralization; mitochondrial membrane; mouse model; mutant; novel; osteoblast differentiation; public health relevance; response; skeletal; skeletal disorder; transcriptome sequencing; two-photon

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to delineate how energy utilization in bone cells is regulated and in turn, how substrate availability affects osteoblast differentiation and bone formation. Optimal bone formation is required for peak bone acquisition and skeletal remodeling across the lifespan. We previously showed IGF-I is necessary for terminal OB differentiation through the mTORC1 pathway. Moreover, PTH induces skeletal IGF-I and this peptide is required for the anabolic actions of PTH on bone. Previously we noted that in C57BL/6J (B6) and C3H/HeJ (C3H) mice, the latter exhibits higher bone density, greater bone formation, and more skeletal Igf1 expression. Importantly, C3H COBs have higher rates of oxidative phosphorylation (OxPhos) and glycolysis (Glyc) than B6. We then established that during terminal OB differentiation glycolysis (Glyc) is favored over OxPhos in both strains and that PTH, which stimulates IGF-I, increases Glyc in both COBs and calvariae ex vivo. To understand the role of the IGF pathway in the bioenergetics of OB differentiation, we have been studying the sml/sml mouse that has a defect in mTOR signaling due to a 'loss of function' mutation in the Irs1 gene. These mice have very low bone mass, reduced bone formation but normal OB number and osteoid volume. Remarkably, sml/sml COBs have significantly reduced OxPhos and Glyc during OB differentiation in vitro and in vivo. Taken together these data point to the importance of energy metabolism during bone formation, and the central role of IGF-I in cellular respiration. As such, in this proposal our over- arching hypothesis is that PTH stimulates bone formation by enhancing Glyc through the induction of IGF-I, which in turn activates IRS1/ mTorc/AKT signaling. Thus we propose 2 specific aims in a high risk, high impact strategy to delineate the importance of substrate availability during PTH induced bone formation using novel single cell imaging and bioenergetic studies of OBs and calvariae: 1-Determine the context-specific nature of OB respiration and Glyc as well as its relationship to bone formation in response to PTH in +/+ and sml/sml mice in vitro and ex vivo: We propose there is a time dependent switch during COB differentiation under the influence of PTH when Glyc is activated, leading to enhanced synthesis and mineralization of matrix. Novel in situ imaging and cellular respiration studies will be employed to determine PTH actions on single cell bioenergetics and will be compared with in vitro studies. 2-Define the importance of the IRS/ mTORC1 mTORC2/AKT signaling pathway for PTH-stimulated changes in energy balance in differentiated OBs. We postulate that mTORC2 activation via the IRS/AKT pathway is critical for up regulating Glyc during the OB differentiation following PTH. We will delineate te relationship of individual signaling components of the mTOR pathway to OB bioenergetics. Findings from these studies could lead to novel insights into the fundamental biology of OBs and enhance the possibility of newer anabolic approaches for skeletal disorders.

描述（由申请人提供）：该提案的长期目标是描述如何调节骨细胞中的能量利用，然后底物的可用性如何影响成骨细胞分化和骨形成。在整个生命周期中，需要峰值骨骼和骨骼重塑需要最佳的骨形成。我们先前表明IGF-I对于通过MTORC1途径的末端OB分化是必需的。此外，PTH会诱导骨骼IGF-I，并且PTH在骨上的合成代谢作用需要这种肽。以前，我们注意到在C57BL/6J（B6）和C3H/HEJ（C3H）小鼠中，后者表现出较高的骨密度，更大的骨形成和骨骼IGF1表达更高。重要的是，与B6相比，C3H棒的氧化磷酸化（OXPHOS）和糖酵解（GLYC）的速率更高。然后，我们确定在末端OB分化期间（GLYC）在菌株中都受到oxphos的青睐，而刺激IGF-I的PTH则增加了COBS和CALVARIAE EX VIVO的GLYC。为了了解IGF途径在OB分化的生物能力中的作用，我们一直在研究由于IRS1基因中的“功能丧失”，该SML/SML小鼠在MTOR信号中具有缺陷。这些小鼠的骨骼质量非常低，骨形成减少，但OB数量正常和骨素体积。值得注意的是，在体外和体内OB分化过程中，SML/SML棒有明显降低OXPHOS和GLYC。这些数据综合起来表明骨形成过程中能量代谢的重要性以及IGF-I在细胞呼吸中的核心作用。因此，在此提案中，我们的过度假设是，PTH通过诱导IGF-I增强GLYC来刺激骨骼形成，这又激活了IRS1/ MTORC/ AKT信号传导。 Thus we propose 2 specific aims in a high risk, high impact strategy to delineate the importance of substrate availability during PTH induced bone formation using novel single cell imaging and bioenergetic studies of OBs and calvariae: 1-Determine the context-specific nature of OB respiration and Glyc as well as its relationship to bone formation in response to PTH in +/+ and sml/sml mice in vitro and ex vivo: We提出在激活GLYC时，在PTH的影响下，在COB分化过程中有一个时间依赖性开关，从而增强了基质的合成和矿化化。将采用新颖的原位成像和细胞呼吸研究来确定对单细胞生物能力的PTH作用，并将与体外研究进行比较。 2定义IRS/ MTORC1 MTORC2/ AKT信号传导途径的重要性对于分化obs中PTH刺激的能量平衡变化。我们假设通过IRS/AKT途径激活MTORC2对于在PTH后在OB分化过程中调节GLYC至关重要。我们将描述MTOR途径的单个信号成分与OB生物能学的关系。这些研究的发现可能会导致对观察的基本生物学的新见解，并增强骨骼疾病的新代谢方法的可能性。