Metformin protects podocytes by inhibiting the MAPK14–SLC7A11–GPX4 axis and dysregulation of fatty acid metabolism

AIMS/HYPOTHESIS: Diabetic nephropathy is a leading cause of end-stage renal disease, with podocyte loss being a critical event in its progression. However, the dominant molecular mechanism driving podocyte loss remains elusive, hindering targeted therapy. We aimed to identify the key pathways of podocyte failure in human diabetic nephropathy and investigate metformin's therapeutic potential. METHODS: We employed an integrative multi-omics approach, including single-nucleus RNA-seq (snRNA-seq) of 156,043 human kidney nuclei from individuals with diabetic nephropathy and healthy control individuals, db/db mouse models of diabetic nephropathy, spatial metabolomics, in vitro podocyte cultures, and targeted urinary metabolomics in individuals with diabetic nephropathy and healthy control individuals. RESULTS: snRNA-seq identified ferroptosis and fatty acid metabolic dysregulation as the most enriched pathways within podocytes, mechanistically linked to the MAPK14-solute carrier family 7 member 11 (SLC7A11)-glutathione peroxidase 4 (GPX4) axis. In murine diabetic nephropathy models and in vitro, metformin directly inhibited this MAPK14-SLC7A11-GPX4 axis, suppressed podocyte ferroptosis (including restoration of GPX4 and SLC7A11 expression and reduction of p-p38 and lipid peroxidation) and restored compartment-specific renal lipid accumulation as shown by spatial metabolomics. Clinically, we identified and validated a urinary fatty acid signature, with palmitoylcarnitine as a key biomarker (AUC 0.974, calculated from receiver operating characteristic curves), correlating with disease indices including blood glucose, eGFR, serum creatinine and blood urea nitrogen. CONCLUSIONS/INTERPRETATION: Our study reveals podocyte ferroptosis to be a central pathogenic event in human diabetic nephropathy, repositioning metformin as a direct ferroptosis inhibitor that preserves podocyte integrity via the MAPK14-SLC7A11-GPX4 axis. Furthermore, we provide a high-performance urinary biomarker, offering a direct translational link toward targeted anti-ferroptosis therapies and non-invasive diagnostics for diabetic nephropathy.