Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles Attenuate Oxidative Damage via the miR-191-5p/DAPK1/AKT Axis in Type 2 Diabetes

Human umbilical cord mesenchymal stem cell extracellular vesicles (hucMSC-EVs) exhibit remarkable potential for alleviating type 2 diabetes mellitus (T2DM). However, the role of hucMSC-EVs in T2DM, particularly concerning oxidative damage to pancreatic β cells, remains underexplored. This study utilized a high-fat diet and streptozotocin (STZ)-induced T2DM mouse model and an STZ-induced INS-1 cell damage model to investigate the effects and mechanisms of hucMSC-EVs. In the T2DM mouse model, hucMSC-EVs effectively lowered blood glucose levels, improved lipid metabolism disorders, and preserved liver function. Moreover, hucMSC-EVs enhanced insulin sensitivity and mitigated oxidative damage. Histological analysis confirmed that hucMSC-EVs marked alleviated liver, kidney, and pancreatic tissue damage. In vitro studies demonstrate that hucMSC-EVs enhance glucose absorption and glycogen synthesis in an insulin-resistant HepG2 model and stimulated insulin secretion in INS-1 cells under high-glucose conditions. In the STZ-induced INS-1 oxidative damage model, hucMSC-EVs protect against oxidative damage by increasing antioxidant enzyme activities, reducing reactive oxygen species production, and decreasing cell apoptosis. The effects were partially mediated by the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT and signal transducer and activator of transcription (STAT) signaling pathways, as well as the up-regulation of key antioxidant proteins such as Nrf2, SOD1, and Bcl2. Further research revealed that miR-191-5p, which is enriched in hucMSC-EVs, targets DAPK1 to activate the PI3K/AKT pathway, thereby contributing to the protective effects against oxidative damage. These findings highlight the critical role and underlying mechanisms of hucMSC-EVs in ameliorating metabolic dysfunction in T2DM, particularly the protective effects against oxidative damage, thus providing a novel strategy for the treatment of T2DM.