Guo Amin, He Bo, Li Angdi, Jiang Huaidong
School of Physical Science and Technology, & Center for Transformative Science, ShanghaiTech University, Shanghai, 201210, China.
iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.
Biochem Biophys Res Commun. 2022 Mar 15;597:23-29. doi: 10.1016/j.bbrc.2022.01.104. Epub 2022 Jan 29.
Insulin is the main hypoglycemic hormone, promoting the absorption and storage of glucose and inhibiting its production. It is a hexamer composed of six insulin macromolecules and a Zn and clustered in insulin vesicles of pancreatic β cell. Most current research has focused on the in vivo imaging of whole cells while there are few detailed studies on structure of insulin vesicles. The precise content of Zn in vesicles is not clear, and the aggregation state and location of insulin in insulin vesicles is not fully characterized, which hinders a thorough understanding of insulin secretion process and diseases caused by blood sugar regulation. Here, we performed electron microscopy (EM) studies on both whole cells (in vivo) and extracted isolated insulin vesicles by supercentrifugation (in vitro) to explore the location and distribution of insulin vesicles in pancreatic β cells. Meanwhile, we analyzed the content of Zn and Ca through EM imaging and energy dispersive spectroscopy (EDS) mapping, and the content of Zn was found to be proportional to the size of insulin vesicles. In addition, by taking advantage of TEM tomography, the three-dimensional structure of insulin vesicle was obtained by acquisition projections in different angles of insulin vesicle. This study provides a promising way to quantitative analysis of intracellular insulin, which may be of great significance to the study of diabetes and other blood sugar diseases.
胰岛素是主要的降血糖激素，它促进葡萄糖的吸收和储存，并抑制其生成。它是一种由六个胰岛素大分子和一个锌组成的六聚体，聚集在胰腺β细胞的胰岛素囊泡中。目前大多数研究集中在全细胞的体内成像，而对胰岛素囊泡结构的详细研究较少。囊泡中锌的精确含量尚不清楚，胰岛素在胰岛素囊泡中的聚集状态和位置也未得到充分表征，这阻碍了对胰岛素分泌过程以及血糖调节引起的疾病的深入理解。在这里，我们对全细胞（体内）进行了电子显微镜（EM）研究，并通过超速离心法提取了分离的胰岛素囊泡（体外），以探索胰岛素囊泡在胰腺β细胞中的位置和分布。同时，我们通过EM成像和能量色散光谱（EDS）映射分析了锌和钙的含量，发现锌的含量与胰岛素囊泡的大小成正比。此外，利用透射电子显微镜断层扫描技术，通过获取胰岛素囊泡不同角度的投影，得到了胰岛素囊泡的三维结构。本研究为细胞内胰岛素的定量分析提供了一种有前景的方法，这可能对糖尿病和其他血糖疾病的研究具有重要意义。
