Circulating large extracellular vesicles as biomarkers of vascular, immune, metabolic, and exercise-related physiology in humans

Extracellular vesicles (EVs) are membrane-bound particles released by cells that carry surface markers and molecular cargo reflective of cellular activation, stress, and intercellular communication. Large EVs within the 200-900 nm size range are commonly associated with plasma membrane-derived microvesicles (MVs), although definitive biogenesis cannot be assigned without direct confirmation. This thesis examined circulating large EV/MV profiles as biologically informative signatures of vascular, immune, metabolic, and exercise-related physiology. Three complementary studies were conducted. First, circulating MV concentration, phenotype, and microRNA (miRNA) cargo were compared between healthy young males and females. Second, the same general analytical framework was applied to individuals with type 2 diabetes (T2D) and healthy controls to determine whether cardiometabolic disease was associated with altered circulating MV profiles. Third, a randomized controlled trial examined whether six weeks of lactate-threshold-based aerobic exercise training altered fasting circulating MV concentration, surface phenotype, and MV-associated miRNA cargo in healthy young adults. Across studies, EVs/MVs were characterized using complementary approaches including size exclusion chromatography (SEC), tunable resistive pulse sensing (TRPS), high-sensitivity flow cytometry, and reverse transcription quantitative polymerase chain reaction (RT-qPCR). In healthy adults, total MV concentration and MV-associated miRNA cargo were comparable between sexes, but females had higher platelet-derived MV concentration in plasma. In T2D, circulating MV profiles reflected a disrupted cardiometabolic environment, characterized by higher total MV concentration, elevated immune-, platelet-, endothelial-, phosphatidylserine-, and Annexin A1-associated MV subpopulations, and increased MV-associated miR-155. In response to chronic aerobic exercise training, resting MV profiles were comparatively stable, with no statistically significant adjusted between-group effects observed for MV concentration, surface phenotype, or MV-associated miRNA cargo. However, tendencies for differences in selected leukocyte-associated MV phenotypes may warrant further investigation in future exercise trials. Collectively, this thesis demonstrates that circulating large EV/MV profiles provide information beyond particle abundance alone. Surface phenotype and molecular cargo appear especially important for interpreting biological relevance, as they may provide insight into cellular origin, activation state, inflammatory signaling, and vascular stress in humans. These findings support continued investigation of EV/MV concentration, phenotype, and cargo as complementary tools for understanding physiological variation, cardiometabolic disease, and exercise adaptation.