Macrophage inflammasome activation and the mechanism of lipolysis resistance in aged adipose

项目摘要 尽管身体质量指数正常，但老年人的内脏肥胖增加， 与代谢疾病风险增加有关。脂肪分解是游离脂肪生成的第一步， 酸和甘油作为能量底物，随着年龄的增长而减少，可能是导致 老年人肥胖症。导致脂肪分解减少的变化尚不清楚，但了解这些变化 可能提供恢复脂肪分解和减少老年人内脏肥胖的方法。脂肪巨噬细胞 在维持组织内环境稳定中至关重要的组织驻留细胞。在衰老过程中， 炎性小体激活和控制脂解减少。衰老和纤维化也会增加， 衰老，但它们是否有助于减少脂肪分解尚不清楚。我们已经鉴定出巨噬细胞表达 生长分化因子（GDF）-3是TGF β家族的成员，是脂肪分解的负调节因子 以及老化过程中炎症、衰老和纤维化的潜在触发因素。本研究的总体目标是 确定巨噬细胞表达的GDF3在促进炎症、衰老和纤维化中的作用， 老年脂肪组织的脂解抵抗力。具体而言，我们建议（1）确定GDF 3如何增加 NLRP 3炎性小体活化和脂解抗性，（2）表征衰老巨噬细胞和 确定GDF 3是否驱动脂肪巨噬细胞中的衰老，以及（3）鉴定GDF 3是否是 所需的ECM生产和增加的纤维化在老年脂肪。在目标1中，我们将识别激活素受体 以及SMAD信号传导是否改变体外巨噬细胞中的炎性小体活化。我们将把这些扩展到 体外结果，并检查GDF3是否是年龄诱导的脂解抵抗和炎症所必需的 使用Gdf3缺乏的老年小鼠模型。在目标2中，我们将使用独特的 允许使用流式细胞术鉴定衰老细胞的转基因小鼠模型。以测试 由于GDF 3的需要，我们将在转基因小鼠中缺失GDF 3以使用流式细胞仪分析脂肪巨噬细胞， 细胞计数和基因表达。目的3将确定细胞外基质蛋白， 巨噬细胞对GDF3的应答。此外，Gdf3 +/+和Gdf3-/-小鼠衰老模型和RNA 测序将用于鉴定在脂肪纤维化中调节GDF3的新候选物。完成本 该项目将允许确定GDF 3在年龄诱导的脂解抵抗中的作用，并作为一种潜在的 在治疗人类衰老过程中的炎症和脂解抵抗中的治疗靶点。长期 候选人的目标是获得一个独立的学术生涯，研究重点是理解 衰老过程中导致脂肪功能障碍的机制。

Project Summary Visceral adiposity is increased in the elderly, despite a normal body-mass-index, and this increase is associated with increased risk for metabolic diseases. Lipolysis is the first step in the generation of free fatty acids and glycerol as energy substrates, is reduced with age and may be responsible for the increased adiposity in the elderly. The changes that drive reduced lipolysis are unclear, but understanding those changes may provide ways to restore lipolysis and reduce visceral adiposity in the elderly. Adipose macrophages are tissue resident cells that are critical in maintaining tissue homeostasis. During aging they have elevated levels of inflammasome activation and control lipolysis reduction. Senescence and fibrosis are also increased with aging, but whether they contribute to reduced lipolysis is unclear. We have identified macrophage-expressed growth differentiation factor (GDF)-3, a member of the TGFβ family, as a negative regulator of adipose lipolysis and potential trigger of inflammation, senescence and fibrosis in aging. The overall goal of this study is to identify the role for macrophage-expressed GDF3 in promoting inflammation, senescence and fibrosis to drive lipolysis resistance in the aged adipose tissue. Specifically, we propose to (1) determine how GDF3 increases NLRP3 inflammasome activation and lipolysis resistance, (2) characterize senescent macrophages and the determine whether GDF3 drives senescence in adipose macrophages and (3) identify whether GDF3 is required for ECM production and increased fibrosis in aged adipose. In Aim 1, we will identify activin receptors and whether SMAD signaling alters inflammasome activation in macrophages in vitro. We will extend these in vitro results and examine whether GDF3 is required for age-induced lipolysis resistance and inflammation using aged mouse models of Gdf3-deficiency. In Aim 2, we will define senescent macrophages using a unique transgenic mouse model permitting the identification of senescent cells using flow cytometry. To test for a requirement of GDF3, we will delete GDF3 in the transgenic mice to analyze adipose macrophages using flow cytometry and gene expression. Aim 3 will identify extracellular matrix proteins that are produced by macrophages in response to GDF3. Additionally, Gdf3+/+ and Gdf3-/- mouse models of aging and RNA sequencing will be used to identify novel candidates regulating GDF3 in adipose fibrosis. Completion of this project will permit identification of the role for GDF3 in age-induced lipolysis resistance and as a potential therapeutic target in treatment of inflammation and lipolysis resistance for humans during aging. The long term goals of the candidate are to obtain an independent academic career with research focused on understanding the mechanisms driving adipose dysfunction in aging.