Diabetic kidney disease (DKD) is increasingly recognized as a consequence of impaired mitochondrial quality control in renal tubular epithelial cells (TECs). In this study we show that the nuclear receptor ESRRA (estrogen related receptor alpha) transcriptionally activates ATG5 (autophagy related 5) to sustain PINK1 (PTEN induced kinase 1)-dependent mitophagy and preserve tubular homeostasis. ESRRA and ATG5 expression were markedly reduced in human DKD biopsies, and their abundance correlated positively with estimated glomerular filtration rate and inversely with albuminuria. Conditional deletion ofin mouse tubules or CRISPR-Cas9 knockout in primary TECs suppressed mitophagy, exacerbated mitochondrial dysfunction and aggravated tubulointerstitial fibrosis, whereas tubularre-expression oroverexpression restored mitophagy and attenuated renal injury. Multi-omics and mechanistic assays identified the natural polyphenol salvianolic acid C (SAC) as a high-affinity ESRRA agonist that binds Asp326, Phe382 and Ala396, stabilizes the receptor and upregulates ATG5. SAC dose-dependently improved proteinuria, renal function, mitochondrial respiration and insulin sensitivity in db/db and high-fat diet-streptozotocin DKD models without overt toxicity. Metabolomic profiling revealed that ESRRA-ATG5-driven mitophagy targets ARG2 (arginase 2) for autophagy-lysosomal degradation, thereby shifting L-arginine flux from urea production toward nitric-oxide synthesis; exogenous L-arginine partly rescued renal injury in-deficient mice. Collectively, this study uncovers an ESRRA-ATG5 axis that couples selective mitophagy to L-arginine metabolism as a pivotal defense against DKD, and identifies SAC as a first-in-class, naturally derived ESRRA activator with therapeutic potential.: AAV: adeno-associated virus; ACR: albumin:creatinine ratio; ACTA2: actin alpha 2, smooth muscle; AKI: acute kidney injury; ALB: albumin; ARG2: arginase 2; ATG12: autophagy related 12; ATG16L1: autophagy related 16-like 1; ATG5: autophagy related 5; BafA1: bafilomycin A1; BUN: blood urea nitrogen; CETSA: cellular thermal shift assay; ChIP-qPCR: chromatin immunoprecipitation followed by quantitative PCR; ChIP-Seq: chromatin immunoprecipitation sequencing; Co-IP: co-immunoprecipitation; CON: control; Cr: creatinine; DEGs: differentially expressed genes; DHE: dihydroethidium; DKD: diabetic kidney disease; eGFR: estimated glomerular filtration rate; ESRD: end-stage renal disease; ESRRA: estrogen related receptor alpha; FSGS: focal segmental glomerulosclerosis; GSEA: gene set enrichment analysis; GTT: glucose tolerance test; HE: hematoxylin and eosin; HFD: high-fat diet; HG: high glucose; HOMA-IR: homeostatic model assessment of insulin resistance; IF: immunofluorescence; IgAN: immunoglobulin A nephropathy; IHC: immunohistochemistry; IOD: integrated optical density; ITT: insulin tolerance test; KD: equilibrium dissociation constant; KEGG: Kyoto Encyclopedia of Genes and Genomes; KO: knockout; LUC: luciferase; MCN: minimal change nephrosis; MST: microscale thermophoresis; MTS: mitochondrial targeting sequence; NAFLD: non-alcoholic fatty liver disease; NIH: National Institutes of Health; NO: nitric oxide; OCR: oxygen consumption rate; PAS: periodic acid-Schiff; PCR: polymerase chain reaction; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; qPCR: quantitative PCR; RNA-seq: RNA sequencing; ROS: reactive oxygen species; RT-qPCR: reverse transcription quantitative PCR; SAC: salvianolic acid C; SAFI: salvianolic acid for injection; SDH: succinate dehydrogenase; SEM: standard error of the mean; SPF: specific pathogen-free; SPR: surface plasmon resonance; STZ: streptozotocin; TCA: tricarboxylic acid; TECs: tubular epithelial cells; TEM: transmission electron microscopy; TFAM: transcription factor A, mitochondrial. Esrra Esrra Atg5Esrra Abbreviations
