Role of PIK3R1 in Adipose Tissue Insulin Resistance and Inflammation in Obesity

项目总结 肥胖及其相关的代谢性疾病是美国最大的公共卫生挑战之一 各州。胰岛素抵抗是肥胖引起的代谢性疾病增加的主要原因，而且 建议继发于由脂肪组织(AT)渗入引起的炎症反应 巨噬细胞和增加的促炎细胞因子的产生。然而，令人惊讶的是，细胞信号 在AT中，启动和传播响应营养过剩炎症表型在很大程度上 未知，突显了知识方面的重大差距。磷酸肌醇3-激酶(PI3K)调节关键胰岛素， 细胞因子和生长信号通路，因此是联系细胞胰岛素抵抗的有力候选者 与炎症反应有关。我们最近发现，PI3K p55和p50的调节性基因增加了2-4倍 高脂饮食(HFD)诱导的肥胖小鼠脂肪细胞中亚基与胰岛素敏感性降低的平行关系。 阻断HFD通过杂合性缺失Pik3r1基因诱导的p55？和p50？增加 编码调节亚基，减少AT巨噬细胞的渗透，显著改善脂肪细胞， 肥胖小鼠骨骼肌与全身性胰岛素敏感性。我们小组的研究已经确定了sirtuin 1 (SIRT1)和信号转导与转录激活因子3(STAT3)作为p50？和p55？的关键调节因子 在营养受限的肌肉中表达和随后的PI3K活性，突出了潜在的普遍性 胰岛素敏感性和细胞能量状态之间的联系。我们假设营养过剩会增加 脂肪细胞p55和p50丰度到，1)抑制胰岛素刺激的PI3K信号，进一步抑制 营养吸收和，2)促进PI3K介导的核因子B的激活，从而刺激细胞因子的产生和 巨噬细胞募集。与目前的范式不同，我们预测胰岛素抵抗本身，通过 PI3K信号促进炎症反应，而不是导致胰岛素抵抗的炎症。至 为了解决这一假设，我们将使用一种将整个动物生理学与细胞相结合的综合方法 和分子技术。具体地说，AIM1将使用脂肪细胞特异的转基因小鼠模型 抑制或过度表达p55和p50研究脂肪细胞p55和p50是否升高 在急性或慢性HFD后，充足是刺激巨噬细胞募集的必要条件和充分条件 喂食。在AIM2中，我们将在体外测试脂肪细胞p55和p50的增加是否改变细胞因子的分泌 通过上调核因子B信号促进巨噬细胞趋化和/或抑制胰岛素 抑制脂解作用。在AIM3中，我们将使用转基因小鼠模型在体内确定HFD是否诱导 AT p55？和p50？的增加位于SIRT1-STAT3轴下游。考虑到PI3K在人类社会中的重要作用 代谢性疾病和癌症研究，这些研究将为PI3K研究提供独特的新资源， 将拓宽我们对PI3K监管的理解，并将促进更有针对性的发展 靶向PI3K的方法，它有可能治疗新陈代谢，并最终影响人类健康。

PROJECT SUMMARY Obesity and its associated metabolic diseases are one of the greatest public health challenges in the United States. Insulin resistance is a primary contributor to this increase in metabolic disease with obesity and is proposed to arise secondary to an inflammatory response caused by infiltration of adipose tissue (AT) with macrophages and increased pro-inflammatory cytokine production. Surprisingly, however, the cellular signals within AT that initiate and propagate the inflammatory phenotype in response to nutrient excess are largely unknown, highlighting a significant gap in knowledge. Phosphoinosital 3-kinase (PI3K) regulates key insulin, cytokine, and growth signaling pathways, and is thus a strong candidate for linking cellular insulin resistance with the inflammatory response. We recently found a 2-4-fold increase in the PI3K p55¿ and p50¿ regulatory subunits in parallel with reduced insulin sensitivity in adipocytes from high-fat diet (HFD)-induced obese mice. Blocking HFD-induced increase in p55¿ and p50¿ through global heterozygous deletion of Pik3r1, the gene that encodes the regulatory subunits, reduced AT macrophage infiltration and significantly improved adipocyte, skeletal muscle and systemic insulin sensitivity in obese mice. Studies by our group have identify sirtuin 1 (SIRT1) and signal transducer and activator of transcription 3 (STAT3) as key regulators of p50¿ and p55¿ expression and subsequent PI3K activity in muscle with nutrient restriction, highlighting a potential universal link between insulin sensitivity and cellular energy status. We hypothesize that nutrient excess increases adipocyte p55¿ and p50¿ abundance to, 1) inhibit insulin-stimulated PI3K signaling, further suppressing nutrient uptake and, 2) promote PI3K-mediate NF¿B activation, thereby stimulating cytokine production and macrophage recruitment. In contrast to the current paradigm, we predict that insulin resistance itself, through PI3K signaling promotes the inflammatory response, rather than inflammation causing insulin resistance. To address this hypothesis, we will use an integrative approach that combines whole animal physiology with cell and molecular techniques. Specifically, AIM1 will use transgenic mouse models with adipocyte-specific knockdown or over-expression of p55¿ and p50¿ to investigate whether increased adipocyte p55¿ and p50¿ abundance is necessary and sufficient to stimulate macrophage recruitment after acute or chronic HFD feeding. In AIM2, we will test in vitro whether increased adipocyte p55¿ and p50¿ alters cytokine secretion through up-regulation of NF¿B signaling to promote macrophage chemotaxis and/or inhibition of insulin suppression of lipolysis. In AIM3, we will use transgenic mouse models to determine in vivo if the HFD-induced increase in AT p55¿ and p50¿ is downstream of a SIRT1-STAT3 axis. Considering the integral role of PI3K in metabolic disease and cancer research, these studies will provide unique new resources for PI3K research, will broaden our understanding of PI3K regulation and will facilitate the development of more focused approaches for targeting PI3K, which has the potential to treat metabolic, and ultimately impact human health.