Insulin Signaling and Metabolic Regulation in Adipocytes

这个项目已经资助了30多年，研究胰岛素的基本机制。 对脂肪代谢的作用和控制健康中全身代谢稳态的功能， 疾病与肥胖相关的合并症，包括胰岛素抵抗和2型糖尿病， 认为是由于脂肪组织内甘油三酯沉积和储存不足，导致 脂肪对肝脏、骨骼肌、心血管器官和胰岛素分泌β细胞的有害作用。 该项目先前使用siRNA筛选来发现Ste20直系同源物Map4k4， 在与代谢稳态相关的许多组织中作为关键信号节点的激酶。在 在前一个资助期，我们仔细评估了Map4k4在体内的作用，表明这种蛋白质 激酶在许多组织中起抑制全身胰岛素敏感性以及促进 动脉粥样硬化因此，我们在六种组织中始终观察到有益的代谢表型- 我们制作的特定Map4k4敲除小鼠模型，证明Map4k4发挥了强大的 值得继续研究的生物学效应。这些研究的重点包括：1。内皮细胞 Map4k4 KO在ApoE敲除小鼠中降低血糖并减弱动脉粥样硬化，2.诱导整体 体Map4k4 KO小鼠显示出增加的胰岛素敏感性，低得多的胰岛素水平和受损的 胰岛分泌胰岛素，3. Myf5阳性细胞中的Map4k4 KO（但脂联素阳性细胞中不存在） 导致脂肪细胞胰岛素敏感性和Akt活化显著增加。后一项发现与 骨骼肌分泌一种或多种增强胰岛素的因子 脂肪细胞的敏感性。总的来说，我们的研究结果还表明，两种蛋白激酶非常相似， Map4k4、Tnik和Mink也可能在相同的途径中起作用。因此，我们生产了三种 将Tnik/Mink/Map4k4小鼠固定，以测试它们在哺乳动物中与Map4k4功能的潜在冗余。 通过与脂联素-Cre小鼠杂交和在β细胞（胰岛素 分泌）通过与Ins1Cre或Ins1CreER小鼠杂交（Aim 1）。我们亦建议严格测试 一个令人兴奋的假设，即Myf5阳性细胞中的Map4k4 KO诱导了一种循环因子， 脂肪细胞胰岛素敏感性和葡萄糖耐量的联体研究与小鼠模型，我们有 设计（目标2）。最后，我们同时试图用免疫荧光法来鉴定血清中的这些循环因子。 Somalogic技术和质谱在UMASS蛋白质组学核心设施（目标3）。 相关性（参见说明）： 脂肪组织在调节能量代谢中起着关键作用，肥胖症中脂肪的过度积累是 与包括2型糖尿病在内的许多疾病有关。我们发现了信号通路的组成部分 他们研究了一种名为Map4k4的酶，这种酶有助于 胰岛素抵抗、动脉粥样硬化和其他与代谢功能相关的疾病。我们希望 进一步表征Map4k4的功能，因为它可能是新药物治疗的良好靶点。

This project, which has been funded for over 30 years, addresses fundamental mechanisms of insulin action on adipose metabolism and functions that control whole body metabolic homeostasis in health and disease. Co-morbidities associated with obesity including insulin resistance and type 2 diabetes are thought to result from insufficient deposition and storage of triglyceride within adipose tissue, leading to deleterious effects of fat on liver, skeletal muscle, cardiovascular organs and insulin secreting beta cells. This project previously employed siRNA screens to discover the Ste20 ortholog Map4k4, a protein kinase that acts as a critical signaling node in many tissues related to metabolic homeostasis. In the previous grant period we have carefully assessed the role of Map4k4 in vivo showing that this protein kinase functions in many tissues to suppress systemic insulin sensitivity as well as promote atherosclerosis. Thus, we consistently observed beneficial metabolic phenotypes in six tissue- specific Map4k4 knockout mouse models we produced, demonstrating that Map4k4 exerts powerful biological effects worthy of continued study. Highlights of these studies include: 1. endothelial cell Map4k4 KO lowers blood glucose and attenuates atherosclerosis in ApoE null mice, 2. Inducible whole body Map4k4 KO mice show increased insulin sensitivity, much lower insulin levels and compromised insulin secretion from islets, 3. Map4k4 KO in Myf5 positive cells (but not in Adiponectin positive cells) causes a marked increase in adipocyte insulin sensitivity and Akt activation. This latter finding is consistent with the exciting hypothesis that skeletal muscle secretes one or more factors that enhance insulin sensitivity of adipocytes. Overall, our findings also suggest that two protein kinases very highly similar to Map4k4, Tnik and Mink, may also be active in the same pathways. We have therefore produced triple floxed Tnik/Mink/Map4k4 mice in order to test their potential redundancy with Map4k4 function in adipocytes (lipid metabolism) by crossing with adiponectin-Cre mice and in beta cells (insulin secretion) by crossing with Ins1Cre or Ins1CreER mice (Aim 1). We also propose to rigorously test the exciting hypothesis that Map4k4 KO in Myf5 positive cells induces a circulating factor that enhances adipocyte insulin sensitivity and glucose tolerance by parabiosis studies with the mouse models we have engineered (Aim 2). Finally, in parallel we seek to identify such circulating factors in serum using Somalogic technology and mass spectroscopy in the UMASS Proteomics Core Facility (Aim 3). RELEVANCE (See instructions): Fat tissue plays a key role in regulating energy metabolism, and excess accumulation of fat in obesity is associated with many maladies including type 2 diabetes. We identified components of signaling pathways in fat cells that mediate dysfunction in obesity and have studied an enzyme called Map4k4 that contributes to insulin resistance, atherosclerosis and other diseases associated with metabolic functions. We hope to further characterize Map4k4's functions, as it may be a good target for new drug therapies.