| Summary: | Extracellular vesicles (EVs) are submicron vesicles released from cells as intercellular communicators. EV research is hindered by a current lack of standardisation. However, mounting evidence suggests a role for EVs in both physiological and pathophysiological processes. Little is known about adipocyte-derived EVs despite the recognition of adipose tissue (AT) as an endocrine organ and the role of dysfunctional AT in disease. Obese AT develops regions of hypoxia and inflammation, leading to obesity-associated metabolic complications. The aim of this thesis was to explore EVs as novel adipocyte communicators, characterising their release under physiological and disease-like conditions. Nanoparticle tracking analysis (NTA) and tunable resistive pulse sensing (TRPS) were assessed for their accuracy and usability for EV quantification. NTA and TRPS both accurately quantified EVs though NTA was more user-friendly. The choice of anticoagulant, filtering and storage of EVs all affected EV concentration. Physiological EV release from 3T3-L1 adipocytes was characterised pre- and post-adipogenesis. EV generation increased prior to adipogenesis and EVs were enriched in pro-signalling fatty acids and proteins characteristic of the original cell. Therefore, EVs may aid the initiation of adipogenesis. Hypoxia was then used to pathologically generate EVs to mimic adipocyte obesity. Adipocyte EV release increased in hypoxia; these EVs were enriched in pro-signalling fatty acids and monocyte chemoattractant protein-1. Hypoxic EVs were then analysed for their interaction with macrophages (Mϕ). Hypoxic EVs may increase Mϕ migration and promote an anti-inflammatory Mϕ phenotype; further repeats are needed to confirm this. Finally, adipocyte markers were detected in plasma EVs suggesting the presence of circulating adipocyte-derived EVs in vivo. Plasma EVs were also reduced in hypercholesterolaemia patients by routine apheresis treatment. In conclusion, adipocytes release EVs which may assist intercellular communication in both physiological and disease-like conditions. Adipocyte-derived EVs can be detected in vivo and may provide novel biomarkers of obesity-associated diseases.
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