Roles of mitochondrial complexes in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is increasingly recognized as a mitochondrial-driven metabolic disorder, yet the specific contributions of individual mitochondrial respiratory chain complexes remain poorly defined. In particular, inconsistent alterations in complexes I–V have been reported across different NAFLD models, representing a critical knowledge gap. Here, we systematically reviewed in vivo and in vitro studies to evaluate changes in mitochondrial complexes I–V during NAFLD progression. Overall, NAFLD is commonly associated with reduced complex activity, impaired mitochondrial respiration, and increased reactive oxygen species production. Notably, a subset of studies reported enhanced complex activity and respiration, suggesting context-dependent mitochondrial adaptations. This synthesis clarifies divergent findings and highlights mitochondrial respiratory complexes as dynamic and therapeutically relevant targets for future NAFLD intervention strategies.