Brown adipose tissue lysosomal and neutral lipases in nonshivering thermogenesis

 描述（由申请人提供）：肥胖是一种新兴的流行病，影响了大约三分之一的美国人口。目前的治疗方法长期疗效低，或需要手术。最近的研究表明，非颤抖性产热（NST）的能力，以减少啮齿类动物的肥胖和人类中的产热脂肪细胞的存在提供了一个潜在的新的策略，开发肥胖症的治疗。NST在冷挑战期间部分地通过棕色脂肪组织（BAT）的作用来维持体温。目前的模型表明，白色脂肪组织（WAT）衍生的脂肪酸是中性脂肪酶（包括脂肪甘油三酯脂肪酶（ATGL/PNPLA 1））的产物。酸性脂肪酶以前没有涉及NST，然而，最近的研究牵连溶酶体酸性脂肪酶（利帕）在WAT的脂解调节。出乎意料的是，我们的初步数据显示，温度挑战激活BAT中的溶酶体功能，并且利帕的全身遗传消融损害产热，使小鼠无法防御体温以响应寒冷挑战。此外，这些溶酶体功能变化似乎是BAT特异性的，而不是WAT。尽管有这些发现，关于这种新的溶酶体依赖性NST和溶酶体和中性脂肪酶在产生产热所需的脂肪酸中的作用的许多问题仍然存在。我们假设利帕通过棕色脂肪细胞内的内源性脂质或通过巨噬细胞为BAT中的解偶联氧化提供脂肪酸。目的研究NST是否需要棕色脂肪细胞的溶酶体功能，特别是利帕功能。我们将使用多种技术的组合：首先，BAT移植以测试具有完整利帕的BAT是否可以拯救利帕敲除小鼠的冷敏感表型，第二，棕色脂肪细胞特异性利帕敲除小鼠。组织特异性模型和移植的冷挑战将使我们能够确定利帕在棕色脂肪细胞中的重要性。在目标二中，我们将评估BAT中的中性脂肪酶ATGL对NST的贡献。一项已发表的ATGL研究使用了在白色脂肪细胞、棕色脂肪细胞和巨噬细胞中缺失的Cre-line，这些细胞均参与NST功能。我们将产生棕色脂肪细胞特异性ATGL敲除系。冷攻击这些小鼠将提供ATGL在BAT NST维持中的作用的功能证据。拟议研究的成功完成将确定酸性和中性脂肪酶对BAT依赖性NST的贡献。

 DESCRIPTION (provided by applicant): Obesity is a burgeoning epidemic that affects approximately one third of the American population. Current treatments have low long-term efficacy or require surgery. Recent research showing the ability of non- shivering thermogenesis (NST) to reduce obesity in rodents and the presence of thermogenic adipocytes in humans provides a potential novel strategy for developing obesity therapies. NST maintains body temperature during a cold challenge in part through the action of brown adipose tissue (BAT). Current models suggest white adipose tissue (WAT) derived fatty acids, products of neutral lipases including adipose triglyceride lipase (ATGL/PNPLA1). Acid lipases have not previously been implicated in NST; however, recent studies implicate lysosomal acid lipase (LIPA) in the regulation of lipolysis in WAT. Unexpectedly, our preliminary data show that temperature challenges activate lysosome function in BAT and that whole body genetic ablation of LIPA impairs thermogenesis, rendering mice unable to defend body temperature in response to a cold challenge. Moreover, these lysosomal functional changes appear to be specific to the BAT, not the WAT. Despite these findings, many questions regarding this novel lysosomal-dependent NST and the role of lysosomal and neutral lipases in producing fatty acids required for thermogenesis remain. We hypothesize that LIPA provides fatty acids for uncoupled oxidation in BAT either through endogenous lipids within brown adipocytes or secondarily through macrophages. Aim One will test whether lysosomal and specifically LIPA function is required in the brown adipocytes for NST. We will use a combination of techniques: first, a BAT transplant to test whether BAT with intact LIPA can rescue the cold sensitive phenotype of the LIPA knockout mice, and second, a brown adipocyte-specific LIPA knockout mouse. Cold challenge of the tissue specific model and the transplant will allow us to determine the importance of LIPA in brown adipocytes. In Aim Two, we will assess the contribution of the neutral lipase ATGL in BAT to NST. A published study of ATGL used a Cre-line that deleted in white adipocytes, brown adipocytes, and macrophages that are each implicated in NST function. We will generate a brown adipocyte-specific ATGL knockout line. Cold challenging these mice will provide functional evidence of the role of ATGL in BAT NST maintenance. Successful completion of the proposed studies will define the contributions of acid and neutral lipases to BAT dependent NST.