Mitochondrial Uncoupling and Thermogenesis in Adipose Tissues

在哺乳动物中，有两种组织主要负责适应性产热：棕色脂肪和米色脂肪。 尽管棕色脂肪长期以来一直被认为是一种特殊的生热组织，但米色脂肪细胞是一种 形态不同的脂肪细胞，暴露在寒冷或高脂肪环境中后，在白色脂肪库中发育 饮食，是最近才被发现的。与棕色脂肪细胞相似，米色脂肪细胞含有丰富的 线粒体，似乎表达线粒体解偶联蛋白1(UCP1)，促进线粒体 通过增加线粒体内膜的被动质子(H+)泄漏来产生热量。然而， 不同米色脂肪库中线粒体解偶联和生热的机制以及 UCP1的相对贡献尚不清楚。此外，棕色和米色脂肪细胞保留了部分生热作用。 即使在UCP1缺陷的小鼠中也是如此。因此，这项建议的重点是识别和 棕色和黄曲霉UCP1依赖和非UCP1产热机制的特征 米色脂肪。为此，我们开发了一种从整体小泡直接记录膜片钳的技术 完整的线粒体内膜(有丝分裂体)，这首次允许高分辨率功能 线粒体天然膜环境中离子通道和转运体的分析。使用这个 方法，我们已经成功地记录了跨越内膜的生热UCP1依赖的H+泄漏电流 棕色和米色脂肪的线粒体膜。有趣的是，并不是所有米色脂肪仓库都有这种UCP1- 依赖于线粒体H+泄漏，利用UCP1缺陷小鼠，我们还发现了一种新的UCP1- 棕色和米色脂肪细胞线粒体解偶联和产热的独立机制。 这一提议有一个单一的特定目标：表征线粒体解偶联和 脂肪组织中的生热作用。因为棕色和米色脂肪中的适应性产热消耗很大 来自脂肪仓库的大量能量，减少身体肥胖和体重，这个项目将帮助 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.