LIPOGENIC PATHWAYS IN ADIPOSE TISSUE DEVELOPMENT AND METABOLISM

该职业发展计划将为Irfan Lodhi博士过渡到独立的职位做好准备 代谢研究的学术研究者。这个为期5年的项目的指导阶段（K99）将是 在华盛顿大学医学院ClaySemenkovich博士的实验室完成。整体 该项目的目的是了解脂肪生成途径在PPARg激活中的作用，PPARg是一个关键的 脂肪组织发育和代谢的调节剂。PPARg属于过氧化物酶体增殖剂- 配体激活的核受体的激活受体（PPAR）家族，最初基于其 被促进过氧化物酶体增殖的试剂激活的能力。PPARg的内源性途径 激活仍然不清楚。以前的研究表明，脂肪酸介导的新生脂肪生成 合成酶（FAS）对于脂肪细胞中PPARg的内源性活化是重要的。基于质谱的 方法鉴定了几种FAS依赖性复合脂质作为PPARg的假定内源性配体。这些 脂质是在过氧化物酶体中产生的，需要一种以前未鉴定的过氧化物酶体酶PexRAP来合成。 他们的合成。在培养的细胞中敲低PexRAP会损害PPARg的激活和脂肪形成，这两种作用都是通过抑制PexRAP的表达来实现的。 这可以用罗格列酮（PPARg的药理学激活剂）来挽救。反义寡核苷酸- 在小鼠中介导的PexRAP敲低降低了PPARg依赖性基因的表达， 体重增加，瘦，改善胰岛素敏感性。进一步的研究表明， 过氧化物酶体生物合成在脂肪形成过程中增加，并受PPARg调节。这些研究一起 这导致了过氧化物酶体衍生的脂质激活PPARg的假设，并且PPARg促进 过氧化物酶体生物合成，导致驱动脂肪细胞分化的前馈循环。以下 设计了具体目标来检验这一假设。目的1将确定是否有脂肪特异性缺失的小鼠 PexRAP被保护免受饮食诱导和遗传形式的肥胖和糖尿病。目标2将描述 脂肪细胞中PexRAP功能的分子机制。最后，目标3将确定过氧化物酶体的作用 脂肪细胞分化中的生物发生。

This career development plan will prepare Dr. Irfan Lodhi to transition to a position as an independent academic investigator in metabolic research. The mentored phase (K99) of this 5 year project will be completed in the laboratory of Dr. Clay Semenkovich at Washington University School of Medicine. The overall objective of this project is to understand the role of lipogenic pathways in the activation of PPARg, a key regulator of adipose tissue development and metabolism. PPARg belongs to the peroxisome proliferator- activated receptor (PPAR) family of ligand-activated nuclear receptors, originally identified based on their ability to be activated by agents that promote peroxisome proliferation. Endogenous pathways of PPARg activation have remained unclear. Previous work suggests that de novo lipogenesis mediated by fatty acid synthase (FAS) is important for endogenous activation of PPARg in adipocytes. A mass spectrometry-based approach identified several FAS-dependent complex lipids as putative endogenous ligands for PPARg. These lipids are made in peroxisomes and require a previously unidentified peroxisomal enzyme named PexRAP for their synthesis. Knockdown of PexRAP in cultured cells impaired PPARg activation and adipogenesis, both of which could be rescued with rosiglitazone, a pharmacological activator of PPARg. Antisense oligonucleotide- mediated knockdown of PexRAP in mice decreased expression of PPARg-dependent genes, reduced fat mass, increased leanness, and improved insulin sensitivity. Additional studies suggested that genes involved in peroxisomal biogenesis increase during adipogenesis and are regulated by PPARg. Together, these studies led to the hypothesis that peroxisome-derived lipids activate PPARg and, reciprocally, PPARg promotes peroxisomal biogenesis, resulting in a feed-forward cycle that drives adipocyte differentiation. The following specific aims are designed to test this hypothesis. Aim 1 will determine if mice with adipose-specific deletion of PexRAP are protected from diet-induced and genetic forms of obesity and diabetes. Aim 2 will characterize the molecular mechanism of PexRAP function in adipocytes. Finally, Aim 3 will determine the role of peroxisomal biogenesis in adipocyte differentiation.