Bartness T J, Ryu V
Department of Biology, Obesity Reversal Center, Georgia State University , Atlanta, GA, USA.
Int J Obes Suppl. 2015 Aug;5(Suppl 1):S35-9. doi: 10.1038/ijosup.2015.9. Epub 2015 Aug 4.
Reports of brown-like adipocytes in traditionally white adipose tissue (WAT) depots occurred ~30 years ago, but interest in white adipocyte 'browning' only has gained attention more recently. We integrate some of what is known about the sympathetic nervous system (SNS) innervation of WAT and brown adipose tissue (BAT) with the few studies focusing on the sympathetic innervation of the so-called 'brite' or 'beige' adipocytes that appear when WAT sympathetic drive increases (for example, cold exposure and food deprivation). Only one brain site, the dorsomedial hypothalamic nucleus (DMH), selectively browns some (inguinal WAT (IWAT) and dorsomedial subcutaneous WAT), but not all WAT depots and only when DMH neuropeptide Y gene expression is knocked down, a browning effect is mediated by WAT SNS innervation. Other studies show that WAT sympathetic fiber density is correlated with the number of brown-like adipocytes (multilocular lipid droplets, uncoupling protein-1 immunoreactivity) at both warm and cold ambient temperatures. WAT and BAT have sensory innervation, the latter important for acute BAT cold-induced temperature increases, therefore suggesting the possible importance of sensory neural feedback from brite/beige cells for heat production. Only one report shows browned WAT capable of producing heat in vivo. Collectively, increases in WAT sympathetic drive and the phenotype of these stimulated adipocytes seems critical for the production of new and/or transdifferentiation of white to brite/beige adipocytes. Selective harnessing of WAT SNS drive to produce browning or selective browning independent of the SNS to counter increases in adiposity by increasing expenditure appears to be extremely challenging.
关于传统白色脂肪组织（WAT）库中出现褐色样脂肪细胞的报道大约出现在30年前，但对白色脂肪细胞“褐色化”的关注直到最近才增多。我们整合了一些关于WAT和褐色脂肪组织（BAT）的交感神经系统（SNS）神经支配的已知信息，以及少数聚焦于所谓“明亮型”或“米色”脂肪细胞交感神经支配的研究，这些脂肪细胞在WAT交感驱动增加时（如冷暴露和食物剥夺）出现。只有一个脑区，即下丘脑背内侧核（DMH），能选择性地使部分（腹股沟WAT（IWAT）和背内侧皮下WAT）而非所有WAT库褐色化，且只有在DMH神经肽Y基因表达被敲低时，褐色化效应才由WAT的SNS神经支配介导。其他研究表明，在温暖和寒冷环境温度下，WAT交感纤维密度都与褐色样脂肪细胞（多泡脂质滴、解偶联蛋白-1免疫反应性）的数量相关。WAT和BAT都有感觉神经支配，后者对BAT急性冷诱导的温度升高很重要，因此提示来自明亮型/米色细胞的感觉神经反馈对产热可能很重要。只有一篇报道显示褐色化的WAT在体内能够产热。总体而言，WAT交感驱动的增加以及这些受刺激脂肪细胞的表型似乎对白色脂肪细胞向明亮型/米色脂肪细胞的新生和/或转分化至关重要。选择性利用WAT的SNS驱动来产生褐色化或独立于SNS的选择性褐色化以通过增加能量消耗来对抗肥胖增加似乎极具挑战性。
