Immunohistochemical localization of leptin and uncoupling protein in white and brown adipose tissue
Immunohistochemical localization of leptin and uncoupling protein in white and brown adipose tissue
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DOI：
10.1210/en.138.2.797
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发表时间：
1997-02-01
期刊：
影响因子：
4.8
通讯作者：
Lowell, BB
中科院分区：
文献类型：
--
作者：
Cinti, S;Frederich, RC;Lowell, BB
瘦素只由脂肪细胞合成，作用于下丘脑以调节能量平衡。先前的信使RNA表达研究表明，瘦素在白色脂肪细胞中表达，也在棕色脂肪组织中表达，但是在棕色脂肪中的表达明显低于在白色脂肪中的表达。这表明瘦素在棕色脂肪组织中的表达可能是由于存在于棕色脂肪组织中的白色脂肪细胞，而棕色脂肪细胞实际上不表达瘦素。为了解决这一点，我们进行了免疫组织化学石蜡切片和研究瘦和肥胖（db/db）小鼠的不同仓库的白色和棕色脂肪瘦蛋白蛋白的表达。为了建立表达瘦素的细胞类型，我们还评估了脂滴的大小和组织，线粒体的超微结构特征，以及解偶联蛋白（一种棕色脂肪特异性标记物）的存在或不存在。在瘦和肥胖（db/db）小鼠的白色脂肪组织中，瘦素蛋白在各种大小的脂肪细胞中表达（检测范围：19.67-200 μ m），包括多房分化阶段的脂肪细胞。瘦素染色在一些贮库（腹膜后）中更强烈，并且似乎随着禁食而减少。在瘦型动物的棕色脂肪组织中，多室解偶联蛋白（UCP）阳性的棕色脂肪细胞具有典型的棕色线粒体，并且在进食和禁食条件下均为瘦素阴性。在肩胛间棕色脂肪组织贮库的周围，观察到具有白色线粒体的单室、UCP阴性脂肪细胞（平均直径：41.55 μ m），并且这些细胞是瘦素阳性的。在肥胖（db/db）动物中，棕色脂肪主要由小的单室性、UCP阳性脂肪细胞（平均直径：40.08 μ m）组成，这些脂肪细胞也是瘦素阳性的。在器官的外周，存在许多大的、单室的、UCP阴性的脂肪细胞（平均直径：73.65 μ m），具有白色样线粒体。正如预期的那样，这些细胞也是瘦素阳性的。总之，经典棕色脂肪细胞不同于白色脂肪细胞，不仅在于它们的形态和UCP表达，而且在于它们明显缺乏可检测的瘦素表达。然而，db/db棕色脂肪细胞是单室的和瘦素阳性的。瘦型动物白色脂肪细胞表达瘦素而棕色脂肪细胞不表达瘦素的分子机制以及db/db小鼠棕色脂肪细胞中瘦素的显著表达将是未来研究的重点。
Leptin is synthesized exclusively by adipocytes and acts on the hypothalamus to regulate energy balance. Previous messenger RNA expression studies demonstrated that leptin is expressed in white adipocytes and also in brown adipose tissue, however expression in brown fat is markedly lower than in white fat. This suggests the possibility that leptin expression in brown adipose tissue is due to the presence of white adipocytes that reside within brown adipose tissue, and that brown adipocytes actually do not express leptin. To address this point, we performed immunohistochemistry on paraffin sections and studied leptin protein expression in different depots of white and brown fat of lean and obese (db/db) mice. To establish the cell type expressing leptin, we also assessed the size and organization of lipid droplets, the ultrastructural features of mitochondria, and the presence or absence of uncoupling protein, a brown fat-specific marker. In white adipose tissue of lean and obese (db/db) mice, leptin protein was expressed in adipocytes of various sizes (range examined: 19.67-200 mu m), including adipocytes at the multilocular stage of differentiation. Leptin staining was more intense in some depots (retroperitoneal), and appeared to decrease with fasting. In brown adipose tissue of lean animals, multilocular uncoupling protein (UCP)-positive brown adipocytes had typical brown mitochondria and were leptin-negative, both in fed and fasted conditions. At the periphery of the interscapular brown adipose tissue depot, unilocular, UCP-negative adipocytes (mean diameter: 41.55 mu m) with white-type mitochondria were observed, and these cells were leptin-positive. In obese (db/db) animals, brown fat was composed mainly of small unilocular, UCP-positive adipocytes (mean diameter: 40.08 mu m), which were also leptin-positive. At the periphery of the organ, numerous large, unilocular, UCP-negative adipocytes (mean diameter: 73.65 mu m) with white-like mitochondria were present. As expected, these cells were also leptin-positive. In summary, classical brown adipocytes differ from white adipocytes, not only by their morphology and UCP expression, but also by their apparent lack of detectable leptin expression. db/db brown adipocytes, however, were unilocular and leptin-positive. The molecular mechanisms mediating expression of leptin in white but not brown adipocytes of lean animals, and the significant expression of leptin in brown adipocytes of db/db mice will be the focus of future studies.