Immune cells regulate circulating adipocyte extracellular vesicle levels in response to metabolic shifts.

Extracellular vesicles (EVs) are now recognized as potent mediators of inter-organ signaling and are implicated in the pathogenesis of obesity and associated comorbidities. Despite a recent surge in functional information about EVs, we still lack a basic understanding of how endogenous EV levels are controlled to regulate inter-organ signaling. New flow cytometry technologies have allowed us to study the regulation of circulating endogenous EVs from metabolically relevant cell types such as adipocytes (adipocyte-derived EVs [adipoEVs]). We provide evidence for a paradigm of EV regulation in which tissue-resident immune cells, predominantly macrophages, clear EVs released by local tissue cells or those entering the tissue from circulation, an activity that determines circulating EV levels. In obesity, EV uptake by adipose tissue immune cells is reduced, leading to increased circulating adipoEVs and reduced adipoEV clearance rates. This work shows that tissue immune cells gate tissue EV entry into the circulation, making them key regulators of inter-organ EV signaling.