Non-alcoholic fatty liver disease (NAFLD) is a clinical frequent disease. However, its pathogenesis still needs further study, especially the mechanism at the molecular level. The recent identified novel protein post-translational modification, lysine succinylation was reported involved in diverse metabolism and cellular processes. In this study, we performed the quantitative succinylome analysis in the liver of NAFLD model to elucidate the regulatory role of lysine succinylation in NAFLD progression. Firstly, experimental model of NAFLD was induced by carbon tetrachloride injection and supplementary high-lipid and low-protein diet. Then series histochemical and biochemical variables were determined. For the quantitative succinylome analysis, tandem mass tags (TMT)-labeling, highly sensitive immune-affinity purification, liquid chromatography-tandem mass spectrometry techniques were applied. Bioinformatics analysis including gene ontology annotation based classification; Wolfpsort based subcellular prediction; function enrichment; protein-protein interaction network construction and conserved succinylation site motifs extraction were performed to decipher the differentially changed succinylated proteins and sites and p-value < 0.05 was selected as threshold. Totally, 815 succinylation sites on 407 proteins were identified, of which 243 succinylation acetylation sites on 178 proteins showed changed succinylation level with the threshold fold change > 1.5. Theses differentially changed succinylated proteins were involved in diverse metabolism pathways and cellular processes including carbon metabolism, amino acid metabolism, fat acid metabolism, binding and catalyzing, anti-oxidation and xenobiotics metabolism. Besides, these differentially changed succinylated proteins were prominently localized to cytoplasm and mitochondria. Moreover, 8 conserved succinylation site motifs were extracted around the succinylation sites. Protein succinylation was an extensive post-translation modification in rat. The changed succinylation level in diverse proteins may disturb multiple metabolism pathways and promote non-alcoholic fatty liver disease development. This study provided a basis for further characterization of the pathophysiological role of lysine succinylation in NAFLD progression, which laid a foundation for the innovation of novel NAFLD drugs and therapies.

Background/Objectives: Metabolic-dysfunction-associated steatotic liver disease (MASLD) and metabolic-dysfunction-associated steatohepatitis (MASH) arise in the setting of obesity, insulin resistance, type 2 diabetes, and metabolic syndrome. This review examines how mitochondrial dysfunction participates in the transition from lipid accumulation to hepatocyte injury, inflammation, and fibrosis, and how evidence from human, animal, and in vitro studies should be interpreted. Methods: We provide a narrative synthesis of mechanistic, translational, and clinical studies on hepatic mitochondrial metabolism, fatty acid oxidation, oxidative phosphorylation, redox stress, organelle crosstalk, mitophagy, mitochondrial biogenesis and proteostasis, mitochondrial danger signals, the gut-liver-mitochondria axis, and mitochondria-related therapeutic strategies. Results: In early metabolic overload, mitochondrial oxidation may increase as an adaptive response. With persistent substrate pressure, this adaptation can become inefficient, with impaired fatty acid disposal, less efficient oxidative phosphorylation, reactive oxygen species production, redox imbalance, defective mitochondrial quality control, altered mitochondrial biogenesis, mitochondrial unfolded protein response (UPRmt)-related proteostatic stress and mtDNA instability. Mitochondrial DNA and RNA released from damaged organelles may also activate cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING), inflammasome, and RNA-sensing pathways, linking hepatocyte stress to macrophage activation, stellate cell activation, extracellular matrix deposition, and fibrosis. Conclusions: The current evidence supports mitochondria as a stage-dependent amplifier of metabolic liver injury rather than a uniform initiating event. Clinically, the strongest evidence remains with upstream metabolic unloading and liver-directed metabolic therapy, whereas direct mitochondrial restoration and quality-control targeting remain promising but less mature.