Inhibition of the mitochondrial fission dynamin-related protein-1 attenuates insulin resistance in hepatoma cells: Implication of mitochondrial dysfunction, apoptosis and nucleolar disruption

Abstract

Background and purpose: Chronic hyperglycaemia, a defining feature of diabetes mellitus, is closely associated with excessive mitochondrial fragmentation. Accordingly, inhibition of mitochondrial fission has been proposed as a potential strategy for alleviating insulin resistance; however, the associated mitochondrial, cellular, and nuclear consequences remain insufficiently characterised. Experimental approach: In the present study, an insulin-resistant (IR) cellular model was established in HepG2 cells and treated with the mitochondrial division inhibitor (Mdivi-1), a selective inhibitor of dynamin-related protein-1 (DRP1). Key results: Exposure of cells to high-glucose medium (25 mM) and insulin (1 nM) decreased glucose uptake, enhanced reactive oxygen species (ROS) production, and downregulated insulin receptor substrate 1 (IRS-1). Also, Mdivi-1 treatment suppressed DRP1 expression in both Insulin-sensitive (IS) and insulin-resistant (IR) cells, upregulated mito­chondrial fusion-related genes (MFN1 and OPA1) in IR cells, and improved cellular glucose uptake. Notably, IR cells exhibited greater responsiveness to Mdivi-1 than IS cells, as evidenced by enhanced glucose utili­zation, elevated ROS generation, increased apoptosis (24.1 vs. 18.8 % in IS cells), and increased PI3K expres­sion. Despite improvements in insulin responsiveness, Mdivi-1 adversely impaired mitochondrial function, as demonstrated by reduced ATP production and decreased mitochondrial membrane potential (MMP). These alterations were accompanied by G0/G1 cell-cycle arrest, chromatin condensation, downregulation of mTORC1, and impaired ribosomal biogenesis, with most cells exhibiting single hyper­trophic or fragmented nucleoli. Conclusion: These findings demonstrate that although Mdivi-1 ameliorated insulin resistance and partially restored insulin signalling, its beneficial effects are accompanied by mitochondrial dysfunction, enhanced apoptosis, and nucleolar alterations. These observations underscore the necessity for therapeutic strategies that selectively restrict mitochondrial fission while preserving mitochondrial integrity and cellular viability.