Mitochondria play an essential role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Previously, we found that succinate-activated respiration was the most affected mitochondrial parameter in mice with mild NAFLD. In this study, we focused on the role of succinate dehydrogenase (SDH) in NAFLD pathogenesis. To induce the progression of NAFLD to nonalcoholic steatohepatitis (NASH), C57BL/6J mice were fed a Western-style diet (WD) or control diet for 30 weeks. NAFLD severity was evaluated histologically and the expression of selected proteins and genes was assessed. Mitochondrial respiration was measured by high-resolution respirometry. Liver redox status was assessed using glutathione, malondialdehyde, and mitochondrial production of reactive oxygen species (ROS). Metabolomic analysis was performed by GC/MS. WD consumption for 30 weeks led to reduced succinate-activated respiration. We also observed decreased SDH activity, decreased expression of the SDH activator sirtuin 3, decreased gene expression of SDH subunits, and increased levels of hepatic succinate, an important signaling molecule. Succinate receptor 1 (SUCNR1) gene and protein expression were reduced in the livers of WD-fed mice. We did not observe signs of oxidative damage compared to the control group. The changes observed in WD-fed mice appear to be adaptive to prevent mitochondrial respiratory chain overload and massive ROS production.

• Keywords
• mitochondria, nonalcoholic fatty liver disease, oxidative phosphorylation, respirometry, succinate, succinate dehydrogenase,
• MeSH
• Apoptosis MeSH
• Biomarkers MeSH
• Cell Respiration MeSH
• Fibrosis MeSH
• Mitochondria, Liver metabolism   MeSH
• Succinic Acid metabolism   MeSH
• Metabolome MeSH
• Metabolomics methods   MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Disease Susceptibility MeSH
• Non-alcoholic Fatty Liver Disease etiology   metabolism   pathology   MeSH
• Oxidation-Reduction * MeSH
• Oxidative Stress * MeSH
• Succinate Dehydrogenase metabolism   MeSH
• Diet, Western * MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Biomarkers MeSH
• Succinic Acid MeSH
• Succinate Dehydrogenase MeSH

Maladaptation of mitochondrial oxidative flux seems to be a considerable feature of nonalcoholic fatty liver disease (NAFLD). The aim of this work was to induce NAFLD in mice fed a Western-style diet (WD) and to evaluate liver mitochondrial functions. Experiments were performed on male C57BL/6J mice fed with a control diet or a WD for 24 weeks. Histological changes in liver and adipose tissue as well as hepatic expression of fibrotic and inflammatory genes and proteins were evaluated. The mitochondrial respiration was assessed by high-resolution respirometry. Oxidative stress was evaluated by measuring lipoperoxidation, glutathione, and reactive oxygen species level. Feeding mice a WD induced adipose tissue inflammation and massive liver steatosis accompanied by mild inflammation and fibrosis. We found decreased succinate-activated mitochondrial respiration and decreased succinate dehydrogenase (SDH) activity in the mice fed a WD. The oxidative flux with other substrates was not affected. We observed increased ketogenic capacity, but no impact on the capacity for fatty acid oxidation. We did not confirm the presence of oxidative stress. Mitochondria in this stage of the disease are adapted to increased substrate flux. However, inhibition of SDH can lead to the accumulation of succinate, an important signaling molecule associated with inflammation, fibrosis, and carcinogenesis.

• Keywords
• mitochondria, nonalcoholic fatty liver disease, oxidative phosphorylation, respirometry,
• MeSH
• Diet, High-Fat adverse effects   MeSH
• Glutathione metabolism   MeSH
• Mitochondria, Liver metabolism   MeSH
• Liver metabolism   pathology   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Non-alcoholic Fatty Liver Disease etiology   metabolism   MeSH
• Lipid Peroxidation * MeSH
• Succinate Dehydrogenase metabolism   MeSH
• Adipose Tissue metabolism   pathology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Glutathione MeSH
• Succinate Dehydrogenase MeSH

Oxidative stress and mitochondrial dysfunction play an important role in the pathogenesis of nonalcoholic fatty liver disease and toxic liver injury. The present study was designed to evaluate the effect of exogenous inducer of oxidative stress (tert-butyl hydroperoxide, tBHP) on nonfatty and steatotic hepatocytes isolated from the liver of rats fed by standard and high-fat diet, respectively. In control steatotic hepatocytes, we found higher generation of ROS, increased lipoperoxidation, an altered redox state of glutathione, and decreased ADP-stimulated respiration using NADH-linked substrates, as compared to intact lean hepatocytes. Fatty hepatocytes exposed to tBHP exert more severe damage, lower reduced glutathione to total glutathione ratio, and higher formation of ROS and production of malondialdehyde and are more susceptible to tBHP-induced decrease in mitochondrial membrane potential. Respiratory control ratio of complex I was significantly reduced by tBHP in both lean and steatotic hepatocytes, but reduction in NADH-dependent state 3 respiration was more severe in fatty cells. In summary, our results collectively indicate that steatotic rat hepatocytes occur under conditions of enhanced oxidative stress and are more sensitive to the exogenous source of oxidative injury. This confirms the hypothesis of steatosis being the first hit sensitizing hepatocytes to further damage.

• MeSH
• Diet, High-Fat MeSH
• Glutathione metabolism   MeSH
• Hepatocytes drug effects   metabolism   MeSH
• Rats MeSH
• Cells, Cultured MeSH
• L-Lactate Dehydrogenase metabolism   MeSH
• Malondialdehyde metabolism   MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Non-alcoholic Fatty Liver Disease metabolism   pathology   MeSH
• Oxidative Stress drug effects   MeSH
• Lipid Peroxidation drug effects   MeSH
• Rats, Wistar MeSH
• Reactive Oxygen Species metabolism   MeSH
• tert-Butylhydroperoxide toxicity   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Glutathione MeSH
• L-Lactate Dehydrogenase MeSH
• Malondialdehyde MeSH
• Reactive Oxygen Species MeSH
• tert-Butylhydroperoxide MeSH