Circulating small extracellular vesicles activate pancreatic stellate cells and impair glucose-stimulated insulin secretion during MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) and type 2 diabetes (T2D) are coexisting conditions that synergistically worsen hepatic and systemic outcomes. Circulating small extracellular vesicles (sEV) elicit diverse cellular responses; however, their potential to impair insulin secretion during MASLD progression remains unclear. We investigated the role of MASLD-associated sEV in the activation of pancreatic stellate cells (PSCs) and the impact on insulin secretion, shedding light on the inter-organ crosstalk in metabolic diseases. C57BL6 male mice were fed a chow (CHD) or a choline-deficient, amino acid defined high-fat diet (CDAAHFD) for 3 or 9 weeks. Metabolic profiles, morphological and functional alterations in hepatic and pancreatic tissues were assessed. Plasma and circulating sEV were characterized by lipidomics and the sEV effects on PSCs activation and glucose-stimulated insulin secretion (GSIS) in pancreatic islets were assessed. Lean mice received single or repeated injections of MASLD-associated circulating sEV to examine their impact on liver and pancreas. Plasma sEV from healthy or individuals with MASLD were characterized by lipidomics, and their ability to activate human PSCs was tested. The PSCs-derived secretome was analysed by proteomics and applied to human stem cell-derived islets (SC-islets). Mice fed a CDAAHFD diet exhibited liver injury, islet inflammation, PSC activation, and increased circulating sEV enriched in reactive lipid species. In vitro, sEV from CDAAHFD-fed mice were efficiently internalized by PSCs and features of activation were found. Likewise, sEV from CDAAHFD-fed mice were internalized by pancreatic islets where they reduced GSIS. After a single in vivo injection, sEV were internalized by macrophages in both liver and pancreas, while repeated injections recruited macrophages and PSCs into pancreatic islets and reduced ex vivo GSIS. Individuals with MASLD also showed elevated plasma sEV levels which activated human PSCs in culture. Under these conditions, conditioned media from activated PSCs impaired GSIS in SC-islets. This study offers new insights into the role of MASLD-associated circulating sEV in regulating hepatic and pancreatic physiology, highlighting their contribution to PSC activation and GSIS impairment. These findings reveal a potential mechanistic between MASLD and the development of T2D.