Brown adipose tissue lysosomal and neutral lipases in nonshivering thermogenesis

 描述(申请人提供)：肥胖症是一种迅速流行的流行病，影响着大约三分之一的美国人口。目前的治疗方法远期疗效较低或需要手术治疗。最近的研究表明，非颤抖生热(NST)能够减少啮齿类动物的肥胖，并在人类中存在生热脂肪细胞，为开发肥胖治疗提供了潜在的新策略。NST在寒冷的挑战中保持体温，部分是通过棕色脂肪组织(BAT)的作用。目前的模型建议白色脂肪组织(WAT)衍生的脂肪酸，中性脂肪酶的产物，包括脂肪甘油三酯脂肪酶(ATGL/PNPLA1)。酸性脂肪酶以前没有涉及到NST；然而，最近的研究表明溶酶体酸性脂肪酶(LIPA)参与调节WAT的脂解。出乎意料的是，我们的初步数据显示，温度挑战激活了蝙蝠的溶酶体功能，而LIPA的全身遗传消融会损害产热，使小鼠无法防御体温来应对寒冷的挑战。此外，这些溶酶体的功能变化似乎是蝙蝠特有的，而不是Wat。尽管有这些发现，关于这种新的溶酶体依赖的NST以及溶酶体和中性脂肪酶在产生产热所需的脂肪酸中的作用仍然存在许多问题。我们推测，LIPA为蝙蝠体内的解偶联氧化提供脂肪酸，可能是通过棕色脂肪细胞内的内源性脂类，也可能是通过巨噬细胞。目的一将测试NST的棕色脂肪细胞是否需要溶酶体，特别是LIPA功能。我们将结合使用多种技术：首先，进行蝙蝠移植，以测试具有完整LIPA的蝙蝠是否可以挽救LIPA基因敲除小鼠的寒冷敏感表型；第二，棕色脂肪细胞特异性LIPA基因敲除小鼠。冷挑战的组织特异性模型和移植将使我们能够确定LIPA在棕色脂肪细胞中的重要性。在第二个目标中，我们将评估BAT中中性脂肪酶ATGL对NST的贡献。一项发表的关于ATGL的研究使用了一个Cre-line，该Cre-line在白色脂肪细胞、棕色脂肪细胞和巨噬细胞中缺失了各自与NST功能有关的基因。我们将产生一个棕色脂肪细胞特异的ATGL基因敲除系。寒冷挑战这些小鼠将为ATGL在BAT NST维持中的作用提供功能证据。成功完成拟议的研究将确定酸性和中性脂肪酶对BAT依赖的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.