Regulation of PTH-induced Osteoanabolism by Inflammatory Lipids

炎症脂质对 PTH 诱导的骨合成代谢的调节

• 批准号: 8248315
• 负责人: Yin Tintut
• 金额: $ 32.83万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-08 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8248315
• 关键词: Accounting; Adenylate Cyclase; Adult; Affect; Age; Agonist; Anabolic Agents; Anabolism; Antioxidants; Apolipoprotein E; Arteries; Atherosclerosis; Attenuated; Blood Vessels; Bone Density; Bone Matrix; Bone Mineral Contents; C57BL/6 Mouse; Cardiovascular Diseases; Cell Count; Cells; Cholesterol; Chronic; Collagen Type I; Connecticut; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Deposition; Diet; Differentiation Antigens; Disease; Enzymes; Epidemiology; Family; Fatty acid glycerol esters; Fibrinogen; GTP-Binding Proteins; Generations; Genes; Goals; Green Fluorescent Proteins; Health; Hormones; Hyperlipidemia; Immediate-Early Genes; In Vitro; Inflammatory; Inflammatory Response; Injection of therapeutic agent; Intervention; Kidney Diseases; Label; Lipids; Lipoproteins; Literature; Liver; Low-Density Lipoproteins; Marrow; Measures; Modification; Molecular; Mus; Nerve Growth Factors; Nuclear Orphan Receptor; Osteoblasts; Osteocytes; Osteoporosis; Paraoxonase 1; Parathyroid Hormone Receptor; Parathyroid gland; Pathway interactions; Patients; Pharmacotherapy; Phospholipids; Plasma; Population; Prevalence; Prevention; Production; Public Health; Rattus; Reaction; Reactive Oxygen Species; Recombinants; Regimen; Regulation; Regulator Genes; Research Personnel; Role; Signal Pathway; Signal Transduction; Site; Stem cells; Teriparatide; Testing; Therapeutic; Thick; Tissues; Transgenes; Transgenic Mice; Treatment Efficacy; United States; Universities; attenuation; base; bone; bone metabolism; bone morphogenetic protein 2; bone turnover; chemokine; cytokine; hormone resistance; hormone sensitivity; hormone therapy; in vitro testing; in vivo; inhibitor/antagonist; insight; member; mouse model; novel; novel strategies; osteoblast differentiation; osteogenic; overexpression; oxidant stress; oxidation; particle; progenitor; promoter; protein activation; receptor; receptor expression; response; trafficking

DESCRIPTION (provided by applicant): Parathyroid hormone (PTH) is a key regulator of bone metabolism and is used as anabolic pharmacotherapy for treatment of osteoporosis. Recent evidence suggests that lipids may affect bone metabolism and that intermittent PTH therapy may fail in the presence of hyperlipidemia. This is clinically important because hyperlipidemia is prevalent in patients with osteoporosis even accounting for age. In the hyperlipidemic condition, bioactive derivatives of low-density lipoproteins (LDL) are generated in the subendothelial space of tissues, triggering chronic inflammatory responses including oxidant stress and expression of cytokines and chemokines. We have found that these inflammatory lipoproteins/lipids are also present in bone and that they inhibit osteoblastic differentiation. In additional studies, we and other investigators demonstrated that hyperlipidemic mice have reduced bone density compared to WT mice. Our preliminary studies, both in vitro and in vivo, now show that lipids inhibit PTH-induced immediate early genes, including Nurr1, a transcriptional regulator of osteoblastic genes, by attenuating cyclic AMP production and that hyperlipidemia blunts PTH-induced osteoanabolism in vivo, primarily in cortical bone. These findings strongly suggest that hyperlipidemia induces PTH resistance. Whether PTH resistance is at the molecular and/or tissue level remains to be determined. Since osteoporosis and hyperlipidemia remain widespread despite treatment, understanding effects of lipids on basal (endogenous) and intermittent (exogenous) PTH may provide new approaches to osteoporosis. We hypothesize that inflammatory lipoproteins, which are increased in hyperlipidemia, reduce PTH anabolic effects. Based on our preliminary studies, in Specific Aim 1, we will test in vitro whether the inhibitory mechanism of lipids on PTH-induced cyclic AMP production is at the level of PTH receptor expression, receptor trafficking, downstream at the level of G-protein activation, or further downstream at the level of adenylate cyclase activation. In Specific Aim 2, we will identify the level at which lipid-induced PTH resistance occurs in vivo: at the level of differentiation of marrow progenitors toward osteogenic vs. adipogenic lineages; anabolic responses of mature osteoblasts/osteocytes; and/or transient expression of osteoclastogenic factors by osteoblasts. We will generate Ldlr-/- mice that express green fluorescent protein targeted to osteoblasts and osteocytes. In Specific Aim 3, we will test whether reducing hyperlipidemia or inhibiting lipid oxidation will reverse PTH resistance in vivo by measuring bone density, histomorphometric parameters and bone turnover markers in the hyperlipidemic (Ldlr-/-) mice that are treated with liver X receptor agonists or that overexpress the anti-oxidant enzyme, paraoxonase-1. These proposed studies will provide insights into how inflammatory lipids inhibit PTH-induced osteoanabolism, pinpoint the site of inhibitory action within the PTH signaling pathway, and demonstrate approaches to reverse lipid-induced PTH dysregulation. PUBLIC HEALTH RELEVANCE: Relevance to Public Health High cholesterol is common in patients with the low bone density disease, osteoporosis. Parathyroid hormone treatment is a promising therapy for osteoporosis, but evidence suggests that it may be much less effective in patients with high cholesterol. The proposed studies will determine how unmanaged cholesterol level reduces efficacy of the treatment so that corrective strategies can be developed.

描述（由申请人提供）：甲状旁腺激素（PTH）是骨代谢的关键调节剂，用作治疗骨质疏松症的合成代谢药物。最近的证据表明，脂质可能会影响骨代谢，间歇性PTH治疗可能会失败，在高脂血症的存在。这在临床上很重要，因为高脂血症在骨质疏松症患者中很普遍，即使考虑到年龄。在高脂血症条件下，低密度脂蛋白（LDL）的生物活性衍生物在组织的内皮下空间中产生，引发慢性炎症反应，包括氧化应激和细胞因子和趋化因子的表达。我们已经发现这些炎性脂蛋白/脂质也存在于骨中，并且它们抑制成骨细胞分化。在另外的研究中，我们和其他研究人员证明，与WT小鼠相比，高脂血症小鼠的骨密度降低。我们的初步研究，在体外和体内，现在表明，脂质抑制PTH诱导的立即早期基因，包括Nurr 1，成骨细胞基因的转录调节因子，通过衰减环AMP的生产和高脂血症钝化PTH诱导的骨坏死在体内，主要是在皮质骨。这些发现强烈表明，高脂血症诱导PTH抵抗。PTH抵抗是否是在分子和/或组织水平仍有待确定。由于骨质疏松症和高脂血症仍然普遍存在，尽管治疗，了解脂质对基础（内源性）和间歇性（外源性）PTH的影响可能会提供新的方法来治疗骨质疏松症。我们推测，高脂血症中增加的炎性脂蛋白降低了PTH合成代谢的作用。基于我们的初步研究，在特定目标1中，我们将在体外测试脂质对PTH诱导的环AMP产生的抑制机制是否在PTH受体表达水平、受体运输、下游G蛋白活化水平或更下游腺苷酸环化酶活化水平。在具体目标2中，我们将确定体内脂质诱导的PTH抵抗发生的水平：骨髓祖细胞向成骨与成脂谱系分化的水平;成熟成骨细胞/骨细胞的合成代谢反应;和/或成骨细胞瞬时表达破骨细胞生成因子。我们将产生表达靶向成骨细胞和骨细胞的绿色荧光蛋白的Ldlr-/-小鼠。在具体目标3中，我们将通过测量高脂血症（Ldlr-/-）小鼠的骨密度、组织形态计量学参数和骨转换标志物来测试降低高脂血症或抑制脂质氧化是否会逆转体内PTH抗性，所述高脂血症（Ldlr-/-）小鼠用肝脏X受体激动剂治疗或过表达抗氧化酶对氧磷酶-1。这些拟议的研究将提供深入了解炎症脂质如何抑制PTH诱导的骨关节炎，精确定位PTH信号通路内的抑制作用位点，并证明逆转脂质诱导的PTH失调的方法。高胆固醇在低骨密度疾病、骨质疏松症患者中很常见。甲状旁腺激素治疗骨质疏松症是一种很有前途的治疗方法，但有证据表明，它可能是低得多的高胆固醇患者的有效性。拟议的研究将确定未管理的胆固醇水平如何降低治疗效果，以便制定纠正策略。