Protein profiling and functional analysis of liver mitochondria from rats with nonalcoholic steatohepatitis

Mitochondrial dysfunction is closely associated with the pathogenesis of nonalcoholic steatohepatitis (NASH). The aim of the present study was to comprehensively determine mitochondrial abnormalities in NASH by detecting the proteomics in liver mitochondria in a NASH rat model, which was induced for 16 weeks by the provision of a high fat and high cholesterol diet (HFD). Serum parameters, including triglycerides, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were determined, and hematoxylin and eosin staining of liver tissues was examined to evaluate the NASH rat model. Various parameters associated with mitochondrial function were examined, including mitochondrial DNA (mtDNA) copy number, mitochondrial membrane potential (MMP) and mitochondrial respiratory chain complex (MRC) activity. The mitochondrial proteomics were analyzed and identified using isobaric tags for relative and absolute quantitation labeling coupled with two-dimensional liquid chromatography-tandem mass spectrometry. The identified proteins were classified and grouped using the Blast2GO program against the non-redundant protein database, the Kyoto Encyclopedia of Genes and Genomes database and the Cluster of Orthologous Groups of proteins database. Compared with the control, mtDNA copy number, MMP, and activities of MRC I and III were decreased markedly in the HFD group. A total of 18 upregulated and 13 downregulated proteins were identified, with a significant 1.2-fold difference between the control and NASH groups. The dysregulated proteins were closely involved in mitochondrial oxidative phosphorylation, the lipid metabolic process and fatty acid β-oxidation. The results of the present study provide important proteomic information regarding liver mitochondria in NASH and serve as a basis for further detailed investigations of the pathogenesis of NASH.