Topic session

Recent studies have produced evidence that extracellular vesicles (EVs) released from adipocytes and visceral adipose tissue (VAT) could have important roles in interorgan communication leading to ectopic fat accumulation in the liver (i.e., non-alcoholic fatty liver disease, NAFLD).However, despite the promising results based on the analyses of the contents of AT-EV, the predicted EV-mediated effects in the liver have been rarely confirmed in vitro or in vivo.In our experiments, we aim to provide the first, detailed mechanistic data about EV-mediated crosstalk between VAT and the liver in vitro.To examine this, EVs were isolated from adipocyte cell line and VAT from NAFLD patients.EVs were then exposed to hepatocyte cell cultures, and EV-mediated changes in hepatocyte fatty acid metabolism and signalling inducing insulin resistance, inflammation and fat accumulation were studied thoroughly.To investigate VAT-hepatocyte crosscommunication in terms of soluble mediators and also to confirm the effects that were mediated by adipocyte/VAT-EV only, VAT samples were incorporated into transwell co-culture system with hepatocytes.METHODS: EVs were isolated from human Simpson Golabi Behmel Syndrome (SGBS) adipocyte cells and NAFLD patient ex vivo VAT cultures by differential steps of ultracentrifugation.EVs were transferred to hepatocyte (immortalized human hepatocyte [IHH], human hepatoma cell line HuH7) cultures.VAT-hepatocyte co-cultures were done by Millicell ® inserts.The effects of EV and VAT on hepatocyte fatty acid metabolism and signalling promoting insulin resistance, inflammation and fat accumulation were studied by qPCR and RNAseq.The amount of fatty acids was analysed by the fluorescent labelling of intracellular lipids and confocal microscopy.Fatty acid profiles of hepatocytes and EVs were determined by mass spectrometry-gas chromatography.RESULTS: Our preliminary analyses revealed that SGBS-EV attach to the hepatocyte cell membrane after 6 h.In addition, SGBS-EV treatment caused increased expression of sterol regulatory elementbinding protein 1c and acetyl coenzyme A carboxylase enzymes in hepatocytes, together with increased number of lipid droplets.CONCLUSION: Our results suggest that EVs are important communicators between AT and the liver, which potentially has a role in the development of NAFLD.Co-cultures and EV isolations, also from VAT, will be continued.