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^AT) of lean and diet-induced obese (DIO) mice, identified unique surface proteins on sEV^AT by surface shaving followed by mass spectrometry, and developed a signature of five unique proteins. Using this signature, we pulled out sEV^AT from the blood of mice and validated the specificity of isolated sEV^AT 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^AT from the blood of lean and DIO mice. Interestingly, sEV^AT-DIO cargo showed a stronger pro-inflammatory effect on THP1 monocytes compared to sEV^AT-Lean and a significant increase in obesity-associated miRNA expression. Equally important, sEV^AT 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^AT isolated from the blood of nondiabetic obese (>30 kg/m²) individuals. Overall, the present study offers a less-invasive approach to characterize AT.