Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 3, Aarhus C, 8000, Aarhus, Denmark.
Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark.
Histochem Cell Biol. 2022 Jun;157(6):623-639. doi: 10.1007/s00418-022-02090-4. Epub 2022 Mar 2.
The glycerol channel AQP7 facilitates glycerol efflux from adipose tissue (AT), and AQP7 deficiency has been suggested to promote obesity. However, the release of glycerol from AT is not fully blocked in AQP7-deficient mice, which suggests that either alternative glycerol channels are present in AT or significant simple diffusion of glycerol occurs. Previous investigations of the expression of other aquaglyceroporins (AQP3, AQP9, AQP10) than AQP7 in AT are contradictory. Therefore, we here aim at determining the cellular localization of AQP3 and AQP9 in addition to AQP7 in human and mouse AT using well-characterized antibodies for immunohistochemistry (IHC) and immunoblotting as well as available single-cell transcriptomic data from human and mouse AT. We confirm that AQP7 is expressed in endothelial cells and adipocytes in human AT and find ex vivo evidence for interaction between AQP7 and perilipin-1 in adipocytes. In addition, labeling for AQP7 in human AT also includes CD68-positive cells. No labeling for AQP3 or AQP9 was identified in endothelial cells or adipocytes in human or mouse AT using IHC. Instead, in human AT, AQP3 was predominantly found in erythrocytes, whereas AQP9 expression was observed in a small number of CD15-positive cells. The transcriptomic data revealed that AQP3 mRNA was found in a low number of cells in most of the identified cell clusters, whereas AQP9 mRNA was found in myeloid cell clusters as well as in clusters likely representing mesothelial progenitor cells. No AQP10 mRNA was identified in human AT. In conclusion, the presented results do not suggest a functional overlap between AQP3/AQP9/AQP10 and AQP7 in human or mouse white AT.
甘油通道水通道蛋白 7（AQP7）促进脂肪组织（AT）中甘油的外排，AQP7 缺乏被认为可促进肥胖。然而，AQP7 缺陷小鼠的 AT 中甘油的释放并未完全被阻断，这表明 AT 中存在替代甘油通道，或者甘油发生了显著的简单扩散。先前对 AQP7 以外的其他水通道蛋白（AQP3、AQP9、AQP10）在 AT 中的表达的研究结果相互矛盾。因此，我们旨在使用经过充分验证的免疫组织化学（IHC）和免疫印迹抗体以及来自人类和小鼠 AT 的可用单细胞转录组数据，确定 AQP3 和 AQP9 除 AQP7 以外在人类和小鼠 AT 中的细胞定位。我们确认 AQP7 在人类 AT 的内皮细胞和脂肪细胞中表达，并在体外发现 AQP7 与脂肪细胞中 perilipin-1 之间存在相互作用的证据。此外，在人类 AT 中，AQP7 的标记物还包括 CD68 阳性细胞。我们使用 IHC 在人类或小鼠 AT 的内皮细胞或脂肪细胞中均未鉴定到 AQP3 或 AQP9 的表达。相反，在人类 AT 中，AQP3 主要存在于红细胞中，而 AQP9 的表达则见于少数 CD15 阳性细胞中。转录组数据显示，AQP3 mRNA 存在于大多数鉴定出的细胞簇中的少数细胞中，而 AQP9 mRNA 存在于髓样细胞簇以及可能代表间皮祖细胞的细胞簇中。在人类 AT 中未鉴定到 AQP10 mRNA。总之，本研究结果表明，在人类或小鼠白色 AT 中，AQP3/AQP9/AQP10 与 AQP7 之间没有功能重叠。
