Mitochondrial Injury and Inflammation–Fibrosis Coupling in Diabetic Kidney Disease: Cell Type-Specific Mechanisms and Therapeutic Implications

Altered mitochondrial metabolism, impaired quality control, and persistent inflammation are closely associated with diabetic kidney disease (DKD). This narrative review examines how these processes differ across renal cell populations and disease contexts, and considers their implications for treatment. We organize the evidence around three overlapping functional states: compensatory adaptation, metabolic vulnerability, and functional decompensation. Each is characterized by a combination of energetic capacity, respiratory reserve, substrate flexibility, and the ability to clear damaged mitochondria. The proposed states offer a testable conceptual framework; they do not constitute a validated biological sequence or clinical staging system. Mechanistic evidence is most extensive in podocytes and proximal tubular epithelial cells, whereas direct evidence in mesangial cells, the distal nephron, and immune-interstitial compartments remain more limited. Experimental studies support individual connections between mitochondrial danger signaling, regulated cell death, senescence, and fibrosis, but rarely establish the entire temporal sequence in a single model. In assessing established therapies, experimental agents, and botanical preparations, we distinguish clinical kidney benefits from mitochondrial functional effects, causal pathway dependence, and direct target engagement. This synthesis supports tailoring interventions to the affected cell population and its remaining adaptive capacity, while testing mitochondrial mediation separately from kidney protection.