A Liquid Biopsy-Based Approach to Isolate and Characterize Adipose Tissue-Derived Extracellular Vesicles from Blood.

Obesity is a major risk factor for multiple chronic diseases. Anthropometric and imaging approaches are primarily used to assess adiposity, and there is a dearth of techniques to determine the changes in adipose tissue (AT) at the molecular level. Extracellular vesicles (EVs) have emerged as a novel and less invasive source of biomarkers for various pathologies. Furthermore, the possibility of enriching cell or tissue-specific EVs from the biofluids based on their unique surface markers has led to classifying these vesicles as "liquid biopsies", offering valuable molecular information on hard-to-access tissues. Here, we isolated small EVs from AT (sEV) of lean and diet-induced obese (DIO) mice, identified unique surface proteins on sEV by surface shaving followed by mass spectrometry, and developed a signature of five unique proteins. Using this signature, we pulled out sEV from the blood of mice and validated the specificity of isolated sEV by measuring the expression of adiponectin, 38 adipokines on an array, and several adipose tissue-related miRNAs. Furthermore, we provided evidence of sEV applicability in disease prediction by characterizing sEV from the blood of lean and DIO mice. Interestingly, sEV cargo showed a stronger pro-inflammatory effect on THP1 monocytes compared to sEV and a significant increase in obesity-associated miRNA expression. Equally important, sEV cargo revealed an obesity-associated aberrant amino acid metabolism that was subsequently validated in the corresponding AT. Lastly, we show a significant increase in inflammation-related molecules in sEV isolated from the blood of nondiabetic obese (>30 kg/m) individuals. Overall, the present study offers a less-invasive approach to characterize AT.