Mitochondrial Copper Homeostasis in Diabetic Kidney Disease: Emerging Links Between Metabolic Stress, Respiratory Chain Dysfunction, and Renal Injury

Diabetic kidney disease (DKD) remains a leading cause of chronic kidney disease and kidney failure despite major therapeutic advances. Current disease-modifying therapies reduce, but do not abolish, residual risk, indicating that additional cell-intrinsic mechanisms convert diabetic metabolic stress into progressive renal injury. Mitochondrial dysfunction has emerged as a central node in this process because renal tubular cells, podocytes, endothelial cells, and mesangial cells rely on mitochondrial oxidative phosphorylation to sustain transport, filtration-barrier integrity, redox control, and adaptive repair. Copper is an essential metal cofactor for cytochrome c oxidase (COX; respiratory chain complex IV), and mitochondrial copper delivery is required for COX assembly, electron transfer, proton-pumping capacity, and ATP generation. This review integrates established evidence from DKD pathobiology, mitochondrial biology, and copper homeostasis with emerging and indirect evidence to examine mitochondrial copper dyshomeostasis as a potential mechanistic link in DKD. Established findings support mitochondrial dysfunction in DKD and the essential role of copper in COX/complex IV assembly and respiratory-chain function. We further propose that diabetic metabolic stress may disturb copper uptake, intracellular trafficking, mitochondrial copper delivery, or copper use by COX, resulting in functional mitochondrial copper depletion or misallocation. Such disturbances could contribute to COX dysfunction, oxidative phosphorylation failure, ATP depletion, mtROS amplification, impaired mitochondrial quality control, and subsequent renal injury. However, direct DKD-specific evidence demonstrating impaired mitochondrial copper trafficking or functional mitochondrial copper depletion remains limited, and this mechanism should therefore be regarded as a testable hypothesis rather than an established pathogenic pathway. We also distinguish this mechanism from cuproptosis, examine intersections with ferroptosis, and outline biomarker, multi-omics, metallomics, and therapeutic opportunities.