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

Obesity is a major risk factor formultiple chronic diseases.Anthropometricand imaging approaches are primarily used to assess adiposity, andthere is a dearth of techniques to determine the changes in adiposetissue (AT) at the molecular level. Extracellular vesicles (EVs) haveemerged as a novel and less invasive source of biomarkers for variouspathologies. Furthermore, the possibility of enriching cell or tissue-specificEVs from the biofluids based on their unique surface markers has ledto 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 anddiet-induced obese (DIO) mice, identified unique surface proteinson 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 validatedthe specificity of isolated sEV(AT) by measuring the expressionof adiponectin, 38 adipokines on an array, and several adipose tissue-relatedmiRNAs. Furthermore, we provided evidence of sEV applicability indisease prediction by characterizing sEV(AT) from the bloodof lean and DIO mice. Interestingly, sEV(AT-DIO) cargoshowed a stronger pro-inflammatory effect on THP1 monocytes comparedto sEV(AT-Lean) and a significant increase in obesity-associatedmiRNA expression. Equally important, sEV(AT) cargo revealedan obesity-associated aberrant amino acid metabolism that was subsequentlyvalidated in the corresponding AT. Lastly, we show a significant increasein inflammation-related molecules in sEV(AT) isolated fromthe blood of nondiabetic obese (>30 kg/m(2)) individuals.Overall, the present study offers a less-invasive approach to characterizeAT.