Evidence for Adipocyte-Derived Extracellular Vesicles in the Human Circulation

• DOI: 10.1210/en.2018-00266
• Publication Date: 2018-07-16T14:01:23Z
• Authors: Katherine D Connolly; Rebecca M Wadey; Donna Mathew; Errin Johnson; D Aled Rees; Philip E James
• Keywords: Blood Platelets; Male; 0303 health sciences; Erythrocytes; Endosomal Sorting Complexes Required for Transport; Blotting, Western; Calcium-Binding Proteins; Endothelial Cells; Cell Cycle Proteins; Healthy Volunteers; Tetraspanin 29; circulating plasma; Extracellular Vesicles; Plasma; 03 medical and health sciences; Adipokines; Microscopy, Electron, Transmission; Adipocytes; Chromatography, Gel; Leukocytes; Humans; Female; Adipocyte-derived extracellular vesicles; Biomarkers

Adipocyte-derived extracellular vesicles (EVs) may serve as novel endocrine mediators of adipose tissue and impact upon vascular health. However, it is unclear whether adipocyte-derived EVs are present in the human circulation. Therefore, the purpose of this study was to seek evidence for the presence of adipocyte-derived EVs in circulating plasma. Size-exclusion chromatography of platelet-free plasma identified fractions 5 to 10 as containing EVs by a peak in particle concentration, which corresponded with the presence of EV and adipocyte proteins. Pooling fractions 5 to 10 and subjecting to ultracentrifugation yielded a plasma EV sample, as verified by transmission electron microscopy (TEM) showing EV structures and Western blotting for EV (e.g., CD9 and Alix) and adipocyte markers. Magnetic beads and a solid-phase assay were used to deplete the EV sample of the four major families of circulating EVs: platelet-derived, leukocyte-derived, endothelial-derived, and erythrocyte-derived EVs. Postdepletion samples from both techniques contained EV structures as visualized by TEM, as well as CD9, Alix, and classic adipocyte proteins. Postdepletion samples also contained a range of other adipocyte proteins from an adipokine array. Adipocyte proteins and adipokines are expressed in optimally processed plasma EV samples, suggesting that adipocyte-derived EVs are secreted into the human circulation.