Mitochondrial Uncoupling and Thermogenesis in Adipose Tissues

在哺乳动物中，两种组织主要负责适应性产热：棕色脂肪和米色脂肪。 虽然棕色脂肪长期以来被认为是一种专门的产热组织，但米色脂肪细胞， 在暴露于冷或高脂肪时在白色脂肪库中发育的形态上不同的脂肪细胞类型 饮食，是最近才发现的。与棕色脂肪细胞相似，米色脂肪细胞含有丰富的 线粒体和似乎表达线粒体解偶联蛋白1（UCP 1），促进线粒体 通过增加线粒体内膜的被动质子（H+）泄漏产生热量。然而，在这方面， 各种米色脂肪库中线粒体解偶联和产热的机制以及 UCP 1的相对贡献仍不清楚。此外，棕色和米色脂肪细胞保留部分产热， 甚至在UCP 1缺陷小鼠中也是如此。因此，本建议的重点是查明和 棕色和棕色植物产热的UCP 1依赖性和UCP 1非依赖性机制的表征 米色脂肪。为此，我们开发了一种技术，直接膜片钳记录从囊泡的整体 完整的线粒体内膜（线粒体），这是第一次允许高分辨率的功能性 线粒体离子通道和转运蛋白在其天然膜环境中的分析。使用此 方法，我们已经成功地记录了产热UCP 1依赖的H+泄漏电流的内部 棕色和米色脂肪的线粒体膜。有趣的是，并不是所有的米色脂肪库都拥有这种UCP 1- 依赖的线粒体H+泄漏，使用UCP 1缺陷小鼠，我们也发现了一种新的UCP 1- 棕色和米色脂肪细胞中线粒体解偶联和产热的独立机制。 该提案有一个单一的具体目标：表征线粒体解偶联的机制， 脂肪组织产热。因为棕色和米色脂肪中的适应性产热消耗了大量 大量的能量从脂肪库和减少身体肥胖和体重，这个项目将有助于 制定控制肥胖和糖尿病的治疗干预措施。

In mammals, two tissues are primarily responsible for adaptive thermogenesis: brown fat and beige fat. Although brown fat has long been known as a specialized thermogenic tissue, beige adipocytes, a morphologically distinct type of fat cells that develop within white fat depots upon exposure to cold or high-fat diet, have been discovered only recently. Similar to brown adipocytes, beige adipocytes contain abundant mitochondria and seem to express mitochondrial uncoupling protein 1 (UCP1), which promotes mitochondrial production of heat by increasing the passive proton (H+) leak of the inner mitochondrial membrane. However, the mechanisms of mitochondrial uncoupling and thermogenesis in various beige fat depots as well as the relative contribution of UCP1 remain unclear. Moreover, brown and beige adipocytes retain partial thermogenic capacity even in UCP1-deficient mice. Therefore, this proposal is focused on the identification and characterization of UCP1-dependent and UCP1-independent mechanisms of thermogenesis in brown and beige fat. To this end, we developed a technique for direct patch-clamp recording from vesicles of the whole intact inner mitochondrial membrane (mitoplasts), which for the first time allowed high-resolution functional analysis of mitochondrial ion channels and transporters in their native membrane environment. Using this method, we have succeeded in recording thermogenic UCP1-dependent H+ leak currents across the inner mitochondrial membrane of brown and beige fat. Interestingly, not all beige fat depots possess this UCP1- dependent mitochondrial H+ leak, and using UCP1-deficient mice we also have discovered a novel UCP1- independent mechanism of mitochondrial uncoupling and thermogenesis in both brown and beige adipocytes. This proposal has a single specific aim: to characterize the mechanisms of mitochondrial uncoupling and thermogenesis in adipose tissues. Because adaptive thermogenesis in brown and beige fat consumes large amounts of energy from fat depots and reduces body adiposity and weight, this project will aid the development of therapeutic interventions to control obesity and diabetes.