XIAP-ULK1-mediated mitophagy modulates carnitine metabolism to mitigate diabetic kidney disease.

Diabetic kidney disease (DKD) is a major complication of diabetes, characterized by progressive renal dysfunction and mitochondrial impairment. Mitophagy, a selective form of macroautophagy/autophagy that maintains mitochondrial quality, is essential for kidney homeostasis. However, the molecular mechanisms by which mitophagy links these pathways to DKD remain poorly understood. This study investigated the role of XIAP-ULK1-mediated mitophagy in regulating carnitine metabolism and its therapeutic potential in alleviating DKD. Through a combination of renal biopsy analysis from DKD patients, diabetic mouse models, high-glucose-treated tubular epithelial cells, and molecular docking, we determined that XIAP upregulation led to ULK1 degradation via K48-linked polyubiquitination, impairing mitophagy and disrupting carnitine metabolism. Restoring ULK1 expression through the ULK1 agonist echinacoside and L-carnitine supplementation improved mitophagy and carnitine homeostasis, reducing kidney injury and enhancing mitochondrial function in diabetic mouse models. These findings suggested that targeting the XIAP-ULK1 axis to restore mitophagy and stabilize carnitine metabolism hold significant promise as a therapeutic strategy for DKD, highlighting the importance of metabolic regulation in kidney disease management.Abbreviations: ACR: ALB (albumin):creatinine ratio; AAV: adeno-associated virus; BUN: blood urea nitrogen; CETSA: cellular thermal shift assay; DARTS: drug affinity responsive target stability; DMEM/F12: Dulbecco's modified Eagle medium/nutrient mixture F-12; FBS: fetal bovine serum; HG: high glucose; IHC: immunohistochemistry; IF: immunofluorescence; LC-MS: liquid chromatography-mass spectrometry; MitoQ: Mitoquinone; PCT: proximal convoluted tubule; PPI: protein-protein interaction; PAS: periodic acid-Schiff; RMSD: root mean square deviation; RMSF: root mean square fluctuation; RNA-seq: RNA sequencing; RT-qPCR: reverse transcription quantitative polymerase chain reaction; Scr: serum creatinine; SDH: succinate dehydrogenase; STZ: streptozotocin; TMLHE: trimethyllysine hydroxylase, epsilon; TEM: transmission electron microscopy; TECs: tubular epithelial cells; scRNA-seq: single-cell RNA sequencing; ULK1: unc-51 like autophagy activating kinase 1; XIAP: X-linked inhibitor of apoptosis.