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首页> 外文期刊>Canadian Journal of Zoology >White, brite, and brown adipocytes: the evolution and function of a heater organ in mammals.
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White, brite, and brown adipocytes: the evolution and function of a heater organ in mammals.

机译：白色，棕色和棕色脂肪细胞：哺乳动物中发热器官的进化和功能。

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Brown fat is a specialized heater organ in eutherian mammals. In contrast to the energy storage function of white adipocytes, brown adipocytes dissipate nutrient energy by uncoupling of mitochondrial oxidative phosphorylation, which depends on uncoupling protein 1 (UCP1). UCP1, as well as UCP2 and UCP3, belong to the family of mitochondrial carriers inserted into the inner mitochondrial membrane for metabolite trafficking between the matrix and the intermembrane space. UCP1 transports protons into the mitochondrial matrix when activated by a rise in free fatty acid levels in the cell. This UCP1-dependant proton leak drives high oxygen consumption rates in the absence of ATP synthesis and dissipates proton motive force as heat. The enormous heating capacity of brown fat is supported by dense vascularization, high rates of tissue perfusion, and high mitochondrial density in brown adipocytes. It has been known for more than 50 years that nonshivering thermogenesis in brown fat serves to maintain body temperature of neonates and small mammals in cold environments, and is used by hibernators for arousal from torpor. It has been speculated that the development of brown fat as a new source for nonshivering thermogenesis provided mammals with a unique advantage for survival in the cold. Indeed brown fat and UCP1 is found in ancient groups of mammals, like the afrotherians and marsupials. In the latter, however, the thermogenic function of UCP1 and brown fat has not been demonstrated as of yet. Notably, orthologs of all three mammalian UCP genes are also present in the genomes of bony fishes and in amphibians. Molecular phylogeny reveals a striking increase in the substitution rate of UCP1 between marsupial and eutherian lineages. At present, it seems that UCP1 only gained thermogenic function in brown adipocytes of eutherian mammals, whereas the function of UCP1 and that of the other UCPs in ectotherms remains to be identified. Evolution of thermogenic function required expression of UCP1 in a brown-adipocyte-like cell equipped with high mitochondrial density embedded in a well-vascularized tissue. Brown-adipocyte-like cells in white adipose tissue, called "brite" (brown-in-white) or "beige" adipocytes, emerge during adipogenesis and in response to cold exposure in anatomically distinct adipose tissue depots of juvenile and adult rodents. These brite adipocytes may resemble the archetypical brown adipocyte in vertebrate evolution. It is therefore of interest to elucidate the molecular mechanisms of brite adipocyte differentiation, study the bioenergetic properties of these cells, and search for the presence of related brown-adipocyte-like cells in nonmammalian vertebrates.CT Animal mitochondria: evolution, performance, and plasticity, Canadian Society of Zoologists' Annual Meeting, University of Guelph, 13-17 May 2013.
机译：棕色脂肪是在以太哺乳动物中的一种特殊的加热器器官。与白色脂肪细胞的能量存储功能相反，棕色脂肪细胞通过线粒体氧化磷酸化的解偶联来耗散营养能量，线粒体的氧化磷酸化取决于解偶联蛋白1（UCP1）。 UCP1以及UCP2和UCP3属于线粒体载体家族，插入到线粒体内膜中，用于代谢物在基质和膜间空间之间的运输。当细胞中游离脂肪酸水平升高时，UCP1将质子转运到线粒体基质中。在没有ATP合成的情况下，这种依赖UCP1的质子泄漏会导致高耗氧率，并以热量的形式耗散质子动力。褐色脂肪的巨大加热能力由褐色脂肪细胞中密集的血管形成，高组织灌注速率和高线粒体密度支持。五十多年来，众所周知，棕色脂肪中无颤抖的生热作用可在寒冷的环境中维持新生儿和小型哺乳动物的体温，冬眠者也用它来引起火炬。据推测，棕色脂肪作为不发抖的生热作用的新来源的发展为哺乳动物提供了在寒冷中存活的独特优势。的确，在古代哺乳动物群体（如非洲人和有袋动物）中发现了棕色脂肪和UCP1。然而，在后者中，尚未证明UCP1和棕色脂肪的生热功能。值得注意的是，所有三个哺乳动物UCP基因的直系同源基因也存在于骨鱼类和两栖动物的基因组中。分子系统发育学表明，有袋世系和真人世系之间UCP1的替代率显着增加。目前，似乎UCP1仅在真核哺乳动物的棕色脂肪细胞中获得产热功能，而UCP1和其他UCP在外热中的功能仍有待确定。致热功能的进化要求UCP1在配备有高线粒体密度的褐色脂肪细胞样细胞中表达，该细胞嵌入血管良好的组织中。白色脂肪组织中的棕色脂肪细胞样细胞，称为“ brite”（白褐色）或“米色”脂肪细胞，在脂肪形成过程中出现，并响应于少年和成年啮齿动物在解剖学上不同的脂肪组织库中的冷暴露。这些脊椎动物的脂肪细胞可能类似于原型棕色脂肪细胞。因此，阐明非脂肪类脊椎动物的脂肪细胞分化的分子机制，研究这些细胞的生物能特性，并寻找相关的棕色脂肪细胞样细胞的存在是很有意义的。CT动物线粒体：进化，性能和可塑性，加拿大动物学家学会年会，圭尔夫大学，2013年5月13日至17日。

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