Molecular Regulation of Beige Fat Cells in Mice and Humans

描述(由申请人提供)：本提案要求为吴军的K01的最后两年期间提供额外的资金，并促进她转变为代谢研究的独立研究员。与肥胖相关的深远的健康后果强调了开发有效的治疗干预措施的重要性。肥胖本质上是一种能量平衡的紊乱，即摄入超过支出。脂肪细胞大致分为白色脂肪细胞和棕色脂肪细胞。白色脂肪细胞专门储存化学能量，而棕色脂肪细胞通过线粒体解偶联蛋白1(UCP1)介导的产热作用来抵御低温和肥胖。资助的K奖导致从小鼠的白色脂肪仓库中分离出米色细胞。不同于经典的棕色脂肪，它来自于Myf-5+肌样细胞谱系，而分散在白色脂肪组织中的米色脂肪细胞则来自非Myf-5谱系。米色细胞有一种不同于白色或棕色脂肪的基因表达模式。米色细胞与白色脂肪细胞相似，Ucp1的基础表达极低，但与经典的棕色脂肪一样，它们对循环AMP刺激的反应是高Ucp1表达和呼吸频率。原代米色脂肪细胞优先对多肽激素虹膜蛋白敏感，这种激素会导致白色脂肪堆积的“褐变”，并改善葡萄糖稳态。先前在成人中观察到的UCP-1+脂肪细胞的沉积在分子上更类似于小鼠的米色脂肪细胞，而不是棕色。这项建议的总体目标是研究通过米色选择性标记和激素反应对米色脂肪的分子调控；以及米色脂肪如何影响人类系统的代谢动态平衡。目的#1.先前的研究表明，米色标记CD137的激活会增加啮齿动物的能量消耗，但其机制尚不清楚。CD137的激活/失活如何影响米色脂肪的功能将在体外和体内进行研究。目的#2.已知的诱导白色脂肪库“褐变”的分子将被研究它们如何影响米色脂肪细胞功能的分子机制。米色选择性激素/信号分子将被识别和功能表征。基因集浓缩分析将用于说明米色选择性激素反应的下游信号级联(S)。目的#3.初步数据显示，在来自不同脂肪仓库的原代基质血管成分(SVF)的分化培养中，虹膜蛋白处理的生热程序显著上调，提示人类这些脂肪仓库中可能存在米色前体/脂肪细胞。将使用建立的米色细胞分选方案从锁骨上和皮下脂肪组织(抽脂样本)中分离出初级米色前体，并将研究人类米色脂肪的功能。

DESCRIPTION (provided by applicant): This proposal requests additional funding for the last two-year period of Jun Wu's K01 and to facilitate her transition into an independent investigator in metabolic research. The profound health consequences associated with obesity emphasize the importance of developing effective therapeutic interventions. Obesity is essentially a disorder of energy balance, in which intake exceeds expenditure. Broadly, adipocytes have been divided into white and brown fat cells. White fat cells are specialized to store chemical energy, whereas brown fat defends against hypothermia and obesity through thermogenesis mediated by mitochondrial uncoupling protein 1 (UCP1). The funded K award has led to the isolation of beige cells from murine white fat depots. Different from the classical brown fat, whic is derived from a myf-5+ muscle-like cellular lineage, beige fat cells, dispersing in white fat tissues are from a non-myf-5 lineage. Beige cells have a gene expression pattern distinct from either white or brown fat. Beige cells resemble white fat cells in having extremely low basal expression of Ucp1, but like classical brown fat, they respond to cyclic AMP stimulation with high Ucp1 expression and respiration rates. Primary beige adipocytes are preferentially sensitive to the polypeptide hormone irisin, which induces "browning" of the white adipose depots and improves glucose homeostasis. Deposits of UCP-1+ adipocytes previously observed in adult humans molecularly resemble murine beige adipose cells much more closely than brown. The overall goal of this proposal is to study molecular regulation of beige fat through beige-selective markers and hormonal responses; and how beige fat impacts systematic metabolic homeostasis in humans. Aim #1. Previous studies shown that activation of beige marker CD137 will increase energy expenditure in rodents, but the mechanism is unknown. How CD137 activation/inactivation affects beige fat function will be investigated in vitro and in vivo. Aim #2. Molecules known to induce "browning" of the white fat depots will be investigated for the molecular mechanisms how they affect beige adipocytes function. Beige-selective hormones/signaling molecules will be identified and functionally characterized. Gene set enrichment analysis will be conducted to illustrate downstream signaling cascades of beige selective hormonal response(s). Aim #3. Preliminary data shown a robust upregulation of thermogenic program upon irisin treatment in the differentiated cultures of primary stromal vascular fraction (SVF) from various human adipose depots, suggesting that beige precursors/adipocytes may exist in these adipose depots in humans. Primary beige precursors will be isolated from both supraclavicular region and subcutaneous adipose tissues (liposuction samples) using the established beige cell sorting protocols and human beige fat functions will be investigated.