Elucidating the role of iron metabolizing macrophages in adipose tissue

阐明铁代谢巨噬细胞在脂肪组织中的作用

• 批准号: 8781372
• 负责人: Merla J. Hubler
• 金额: $ 2.73万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-10 至 2018-09-09
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8781372
• 关键词: Adipocytes; Adipose tissue; Aftercare; Anti-Inflammatory Agents; Anti-inflammatory; Attention; Cell Culture Techniques; Cell physiology; Cells; Characteristics; Chelating Agents; Coculture Techniques; Cultured Cells; Data; Dichloromethylene Diphosphonate; Diet; Endocrinology; Etiology; Gene Expression; Genetic Models; Health; Hemoglobin; Homeostasis; Human; Hydroxychloroquine; Immune; Immunology; In Vitro; Inflammation; Inflammatory; Insulin Resistance; Iron; Iron Overload; Knock-out; Light; Link; Lipids; Liposomes; Maintenance; Metabolic; Metabolic Pathway; Methods; Mitochondria; Modeling; Mus; Nonesterified Fatty Acids; Obese Mice; Obesity; Pathway interactions; Peritoneal; Peritoneum; Phenotype; Physiological; Play; Population; Prevalence; Reading; Role; Signal Transduction; System; Techniques; Training; ammoniacal ferrous citrate; comparative; cytokine; cytotoxic; cytotoxicity; fluorexon; follow-up; glucose tolerance; in vivo; insulin sensitivity; insulin signaling; iron metabolism; lipid biosynthesis; macrophage; metabolomics; metal transporting protein 1; novel; oxidation; public health relevance; receptor; response; uptake

DESCRIPTION (provided by applicant): In the last decade, there has been growing appreciation of adipose tissue (AT) inflammation in obesity, and its link to insulin sensitivity. Te prevalence of insulin resistance in our population makes it imperative that we come to a better understanding of the role of immune cells in maintaining healthy AT. Macrophages are the predominant immune cell in AT and are known to change to an inflammatory phenotype in response to unhealthy lipid accumulation in obesity. Lean AT contains a resident population of anti-inflammatory "M2-like" AT macrophages (M2 ATMs), whose role in the maintenance of a healthy lean state is not well understood. Our lab has recently identified a "MFehi" sub-population of M2 ATMs, with a two-fold increase in intracellular iron content and increased expression of genes involved in iron uptake (e.g. CD163), storage and release. This population composes 25% of M2 ATMs in lean AT and also exists in obese mouse and human AT. Previous studies have demonstrated that adipocytes require iron for adipogenesis, but excess iron is cytotoxic and leads to systemic changes in insulin sensitivity. Therefore, healthy adipocytes must maintain a narrow range of intracellular iron concentrations. It remains unknown whether MFehi ATMs contribute to adipocyte iron homeostasis. We hypothesize that MFehi ATMs modulate iron availability to adipocytes, and thereby impact insulin sensitivity of lean and obese AT. To identify possible iron exchange between MFehi ATMs and adipocytes, we will co-culture these cells after iron-loading treatment and from genetic models of iron overload. In initial studies, we have successfully quantified increased intracellular iron in macrophages after treatment with ferrous ammonium citrate and the chelator 8-hydroxychloroquine. We also propose to deplete MFehi ATMs in vivo in mice using CD163-targeted clodronate-containing liposomes. Depletion will allow us to determine the impact of MFehi ATMs on the systemic metabolic state. Our preliminary studies with fluorescent calcein-loaded liposomes in the peritoneum have revealed CD163-targeted liposomes as a novel technique to specifically target ATMs. Lastly, comparative metabolomics analysis of MFehi and MFelo ATMs will serve as an unbiased hypothesis-generating approach to characterizing the MFehi phenotype. From our current understanding of iron in cell function, we expect to find changes in mitochondrial and/or lipid oxidation pathways in the MFehi population. The studies in this proposal will allow us to define the role of the MFehi population in maintaining healthy adipocyte iron concentrations and, thereby, insulin sensitivity.

描述（由申请人提供）：在过去的十年中，人们越来越重视肥胖症中的脂肪组织（AT）炎症及其与胰岛素敏感性的联系。胰岛素抵抗在我们人群中的流行使得我们必须更好地理解免疫细胞在维持健康AT中的作用。巨噬细胞是AT中的主要免疫细胞，并且已知其响应于肥胖症中的不健康脂质积聚而改变为炎性表型。瘦AT包含抗炎性“M2样”AT巨噬细胞（M2 ATM）的常驻群体，其在维持健康瘦状态中的作用尚不清楚。我们的实验室最近鉴定了M2 ATM的“MFehi”亚群，其细胞内铁含量增加两倍，并且参与铁摄取（例如CD 163）、储存和释放的基因表达增加。该群体构成瘦AT中M2 ATM的25%，并且也存在于肥胖小鼠和人AT中。以前的研究表明，脂肪细胞需要铁的脂肪形成，但过量的铁是细胞毒性的，并导致胰岛素敏感性的全身变化。因此，健康的脂肪细胞必须维持一个狭窄的细胞内铁浓度范围。目前尚不清楚MFehi ATM是否有助于脂肪细胞铁稳态。我们假设MFehi ATM调节脂肪细胞的铁可用性，从而影响瘦和肥胖AT的胰岛素敏感性。为了鉴定MFehi ATM和脂肪细胞之间可能的铁交换，我们将在铁负载处理后和从铁过载的遗传模型共培养这些细胞。在最初的研究中，我们已经成功地定量增加细胞内铁与柠檬酸亚铁铵和螯合剂8-羟氯喹治疗后的巨噬细胞。我们还提出使用CD 163靶向的含氯膦酸盐的脂质体在小鼠体内耗尽MFehi ATM。消耗将使我们能够确定MFehi ATM对全身代谢状态的影响。我们在腹膜中使用荧光钙黄绿素负载脂质体的初步研究揭示了CD 163靶向脂质体作为特异性靶向ATM的新技术。最后，MFehi和MFelo ATM的比较代谢组学分析将作为表征MFehi表型的无偏假设生成方法。根据我们目前对铁在细胞功能中的理解，我们期望在MFehi人群中发现线粒体和/或脂质氧化途径的变化。本提案中的研究将使我们能够确定MFehi人群在维持健康脂肪细胞铁浓度和胰岛素敏感性方面的作用。