Alcohol- and Low-Iron Induced Changes in Antioxidant and Energy Metabolism Associated with Protein Lys Acetylation.

Understanding the role of iron in ethanol-derived hepatic stress could help elucidate the efficacy of dietary or clinical interventions designed to minimize liver damage from chronic alcohol consumption. We hypothesized that normal levels of iron are involved in ethanol-derived liver damage and reduced dietary iron intake would lower the damage caused by ethanol. We used a pair-fed mouse model utilizing basal Lieber-DeCarli liquid diets for 22 weeks to test this hypothesis. In our mouse model, chronic ethanol exposure led to mild hepatic stress possibly characteristic of early-stage alcoholic liver disease, seen as increases in liver-to-body weight ratios. Dietary iron restriction caused a slight decrease in non-heme iron and ferritin (FeRL) expression while it increased transferrin receptor 1 (TfR1) expression without changing ferroportin 1 (FPN1) expression. It also elevated protein lysine acetylation to a more significant level than in ethanol-fed mice under normal dietary iron conditions. Interestingly, iron restriction led to an additional reduction in nicotinamide adenine dinucleotide (NAD+) and NADH levels. Consistent with this observation, the major mitochondrial NAD+-dependent deacetylase, NAD-dependent deacetylase sirtuin-3 (SIRT3), expression was significantly reduced causing increased protein lysine acetylation in ethanol-fed mice at normal and low-iron conditions. In addition, the detection of superoxide dismutase 1 and 2 levels (SOD1 and SOD2) and oxidative phosphorylation (OXPHOS) complex activities allowed us to evaluate the changes in antioxidant and energy metabolism regulated by ethanol consumption at normal and low-iron conditions. We observed that the ethanol-fed mice had mild liver damage associated with reduced energy and antioxidant metabolism. On the other hand, iron restriction may exacerbate certain activities of ethanol further, such as increased protein lysine acetylation and reduced antioxidant metabolism. This metabolic change may prove a barrier to the effectiveness of dietary reduction of iron intake as a preventative measure in chronic alcohol consumption.

Evaluation of mitochondrial biogenesis and ROS generation in high-grade serous ovarian cancer.

Introduction: Ovarian cancer is one of the leading causes of death for women with cancer worldwide. Energy requirements for tumor growth in epithelial high-grade serous ovarian cancer (HGSOC) are fulfilled by a combination of aerobic glycolysis and oxidative phosphorylation (OXPHOS). Although reduced OXPHOS activity has emerged as one of the significant contributors to tumor aggressiveness and chemoresistance, up-regulation of mitochondrial antioxidant capacity is required for matrix detachment and colonization into the peritoneal cavity to form malignant ascites in HGSOC patients. However, limited information is available about the mitochondrial biogenesis regulating OXPHOS capacity and generation of mitochondrial reactive oxygen species (mtROS) in HGSOC. Methods: To evaluate the modulation of OXPHOS in HGSOC tumor samples and ovarian cancer cell lines, we performed proteomic analyses of proteins involved in mitochondrial energy metabolism and biogenesis and formation of mtROS by immunoblotting and flow cytometry, respectively. Results and discussion: We determined that the increased steady-state expression levels of mitochondrial- and nuclear-encoded OXPHOS subunits were associated with increased mitochondrial biogenesis in HGSOC tumors and ovarian cancer cell lines. The more prominent increase in MT-COII expression was in agreement with significant increase in mitochondrial translation factors, TUFM and DARS2. On the other hand, the ovarian cancer cell lines with reduced OXPHOS subunit expression and mitochondrial translation generated the highest levels of mtROS and significantly reduced SOD2 expression. Evaluation of mitochondrial biogenesis suggested that therapies directed against mitochondrial targets, such as those involved in transcription and translation machineries, should be considered in addition to the conventional chemotherapies in HGSOC treatment.

Mitochondrial oxidative phosphorylation is impaired in TALLYHO mice, a new obesity and type 2 diabetes animal model.

Type 2 diabetes has become an epidemic disease largely explained by the dramatic increase in obesity in recent years. Mitochondrial dysfunction is suggested as an underlying factor in obesity and type 2 diabetes. In this study, we evaluated changes in oxidative phosphorylation and mitochondrial biogenesis in a new human obesity and type 2 diabetes model, TALLYHO/Jng mice. We hypothesized that the sequence variants identified in the whole genome analysis of TALLYHO/Jng mice would affect oxidative phosphorylation and contribute to obesity and insulin resistant phenotypes. To test this hypothesis, we investigated differences in the expression and activity of oxidative phosphorylation complexes, including the transcription and translation of nuclear- and mitochondrial-encoded subunits and enzymatic activities, in the liver and kidney of TALLYHO/Jng and C57BL/6 J mice. A significant decrease was observed in the expression of nuclear- and mitochondrial-encoded subunits of complex I and IV, respectively, in TALLYHO/Jng mice, which coincided with significant reductions in their enzymatic activities. Furthermore, sequence variants were identified in oxidative phosphorylation complex subunits, a mitochondrial tRNA synthetase, and mitochondrial ribosomal proteins. Our data suggested that the lower expression and activity of oxidative phosphorylation complexes results in the diminished energy metabolism observed in TALLYHO/Jng mice. Sequence variants identified in mitochondrial proteins accentuated a defect in mitochondrial protein synthesis which also contributes to impaired biogenesis and oxidative phosphorylation in TALLYHO/Jng mice. These results demonstrated that the identification of factors contributing to mitochondrial dysfunction will allow us to improve the disease prognosis and treatment of obesity and type 2 diabetes in humans.