Metabolic syndrome is a growing concern in developed societies and due to its polygenic nature, the genetic component is only slowly being elucidated. Common mitochondrial DNA sequence variants have been associated with symptoms of metabolic syndrome and may, therefore, be relevant players in the genetics of metabolic syndrome. We investigate the effect of mitochondrial sequence variation on the metabolic phenotype in conplastic rat strains with identical nuclear but unique mitochondrial genomes, challenged by high-fat diet. We find that the variation in mitochondrial rRNA sequence represents risk factor in the insulin resistance development, which is associated with diacylglycerols accumulation, induced by tissue-specific reduction of the oxidative capacity. These metabolic perturbations stem from the 12S rRNA sequence variation affecting mitochondrial ribosome assembly and translation. Our work demonstrates that physiological variation in mitochondrial rRNA might represent a relevant underlying factor in the progression of metabolic syndrome.

• MeSH
• Diet, High-Fat adverse effects   MeSH
• Genetic Predisposition to Disease MeSH
• Haplotypes * MeSH
• Insulin Resistance genetics   MeSH
• Rats MeSH
• Metabolic Syndrome * genetics   metabolism   MeSH
• DNA, Mitochondrial genetics   metabolism   MeSH
• Mitochondria metabolism   genetics   MeSH
• RNA, Mitochondrial genetics   metabolism   MeSH
• RNA, Ribosomal * genetics   metabolism   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
• DNA, Mitochondrial MeSH
• RNA, Mitochondrial MeSH
• RNA, Ribosomal * MeSH
• RNA, ribosomal, 12S MeSH Browser

Individual complexes of the mitochondrial oxidative phosphorylation system (OXPHOS) are not linked solely by their function; they also share dependencies at the maintenance/assembly level, where one complex depends on the presence of a different individual complex. Despite the relevance of this "interdependence" behavior for mitochondrial diseases, its true nature remains elusive. To understand the mechanism that can explain this phenomenon, we examined the consequences of the aberration of different OXPHOS complexes in human cells. We demonstrate here that the complete disruption of each of the OXPHOS complexes resulted in a decrease in the complex I (cI) level and that the major reason for this is linked to the downregulation of mitochondrial ribosomal proteins. We conclude that the secondary cI defect is due to mitochondrial protein synthesis attenuation, while the responsible signaling pathways could differ based on the origin of the OXPHOS defect.

• Keywords
• Biochemistry, Cell biology, Molecular biology,
• Publication type
• Journal Article MeSH

Obesity adversely affects bone and fat metabolism in mice and humans. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have been shown to improve glucose metabolism and bone homeostasis in obesity. However, the impact of omega-3 PUFAs on bone marrow adipose tissue (BMAT) and bone marrow stromal cell (BMSC) metabolism has not been intensively studied yet. In the present study we demonstrated that omega-3 PUFA supplementation in high fat diet (HFD + F) improved bone parameters, mechanical properties along with decreased BMAT in obese mice when compared to the HFD group. Primary BMSCs isolated from HFD + F mice showed decreased adipocyte and higher osteoblast differentiation with lower senescent phenotype along with decreased osteoclast formation suggesting improved bone marrow microenvironment promoting bone formation in mice. Thus, our study highlights the beneficial effects of omega-3 PUFA-enriched diet on bone and cellular metabolism and its potential use in the treatment of metabolic bone diseases.

• MeSH
• Adiposity MeSH
• Bone and Bones metabolism   MeSH
• Bone Marrow * metabolism   MeSH
• Humans MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Obesity complications   prevention & control   metabolism   MeSH
• Fatty Acids, Omega-3 * pharmacology   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fatty Acids, Omega-3 * MeSH

OBJECTIVE: The use of thiazolidinediones (TZDs) as insulin sensitizers has been shown to have side effects including increased accumulation of bone marrow adipocytes (BMAds) associated with a higher fracture risk and bone loss. A novel TZD analog MSDC-0602K with low affinity to PPARγ has been developed to reduce adverse effects of TZD therapy. However, the effect of MSDC-0602K on bone phenotype and bone marrow mesenchymal stem cells (BM-MSCs) in relation to obesity has not been intensively studied yet. METHODS: Here, we investigated whether 8-week treatment with MSDC-0602K has a less detrimental effect on bone loss and BM-MSC properties in obese mice in comparison to first generation of TZDs, pioglitazone. Bone parameters (bone microstructure, bone marrow adiposity, bone strength) were examined by μCT and 3-point bending test. Primary BM-MSCs were isolated and measured for osteoblast and adipocyte differentiation. Cellular senescence, bioenergetic profiling, nutrient consumption and insulin signaling were also determined. RESULTS: The findings demonstrate that MSDC-0602K improved bone parameters along with increased proportion of smaller BMAds in tibia of obese mice when compared to pioglitazone. Further, primary BM-MSCs isolated from treated mice and human BM-MSCs revealed decreased adipocyte and higher osteoblast differentiation accompanied with less inflammatory and senescent phenotype induced by MSDC-0602K vs. pioglitazone. These changes were further reflected by increased glycolytic activity differently affecting glutamine and glucose cellular metabolism in MSDC-0602K-treated cells compared to pioglitazone, associated with higher osteogenesis. CONCLUSION: Our study provides novel insights into the action of MSDC-0602K in obese mice, characterized by the absence of detrimental effects on bone quality and BM-MSC metabolism when compared to classical TZDs and thus suggesting a potential therapeutical use of MSDC-0602K in both metabolic and bone diseases.

• Keywords
• Bone marrow adiposity, Bone marrow mesenchymal stem cells, Bone microstructure, Obesity-induced bone fragility, Pioglitazone, Thiazolidinedione analog MSDC-0602K,
• MeSH
• Bone Marrow Stromal Antigen 2 metabolism   pharmacology   MeSH
• Glucose metabolism   MeSH
• Glutamine metabolism   MeSH
• Hypoglycemic Agents pharmacology   MeSH
• Insulin metabolism   MeSH
• Humans MeSH
• Mesenchymal Stem Cells * metabolism   MeSH
• Mice, Obese MeSH
• Mice MeSH
• Obesity drug therapy   metabolism   MeSH
• Pioglitazone metabolism   pharmacology   MeSH
• PPAR gamma metabolism   MeSH
• Spiro Compounds MeSH
• Thiazolidinediones * pharmacology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 10-methyl spiro(4.5)dec-6-en-6-carboxylic acid MeSH Browser
• 2,4-thiazolidinedione MeSH Browser
• Bone Marrow Stromal Antigen 2 MeSH
• Glucose MeSH
• Glutamine MeSH
• Hypoglycemic Agents MeSH
• Insulin MeSH
• Pioglitazone MeSH
• PPAR gamma MeSH
• Spiro Compounds MeSH
• Thiazolidinediones * MeSH

In humans, disruptions in the heme biosynthetic pathway are associated with various types of porphyrias, including variegate porphyria that results from the decreased activity of protoporphyrinogen oxidase IX (PPO; E.C.1.3.3.4), the enzyme catalyzing the penultimate step of the heme biosynthesis. Here we report the generation and characterization of human cell lines, in which PPO was inactivated using the CRISPR/Cas9 system. The PPO knock-out (PPO-KO) cell lines are viable with the normal proliferation rate and show massive accumulation of protoporphyrinogen IX, the PPO substrate. Observed low heme levels trigger a decrease in the amount of functional heme containing respiratory complexes III and IV and overall reduced oxygen consumption rates. Untargeted proteomics further revealed dysregulation of 22 cellular proteins, including strong upregulation of 5-aminolevulinic acid synthase, the major regulatory protein of the heme biosynthesis, as well as additional ten targets with unknown association to heme metabolism. Importantly, knock-in of PPO into PPO-KO cells rescued their wild-type phenotype, confirming the specificity of our model. Overall, our model system exploiting a non-erythroid human U-2 OS cell line reveals physiological consequences of the PPO ablation at the cellular level and can serve as a tool to study various aspects of dysregulated heme metabolism associated with variegate porphyria.

• MeSH
• Cell Line MeSH
• CRISPR-Cas Systems MeSH
• Heme MeSH
• Aminolevulinic Acid metabolism   MeSH
• Humans MeSH
• Oxidoreductases * genetics   metabolism   MeSH
• Porphyria, Variegate * genetics   MeSH
• Protoporphyrinogen Oxidase genetics   metabolism   MeSH
• Protoporphyrins MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Heme MeSH
• Aminolevulinic Acid MeSH
• Oxidoreductases * MeSH
• Protoporphyrinogen Oxidase MeSH
• Protoporphyrins MeSH
• protoporphyrinogen MeSH Browser

The oxidative phosphorylation (OXPHOS) system localized in the inner mitochondrial membrane secures production of the majority of ATP in mammalian organisms. Individual OXPHOS complexes form supramolecular assemblies termed supercomplexes. The complexes are linked not only by their function but also by interdependency of individual complex biogenesis or maintenance. For instance, cytochrome c oxidase (cIV) or cytochrome bc1 complex (cIII) deficiencies affect the level of fully assembled NADH dehydrogenase (cI) in monomeric as well as supercomplex forms. It was hypothesized that cI is affected at the level of enzyme assembly as well as at the level of cI stability and maintenance. However, the true nature of interdependency between cI and cIV is not fully understood yet. We used a HEK293 cellular model where the COX4 subunit was completely knocked out, serving as an ideal system to study interdependency of cI and cIV, as early phases of cIV assembly process were disrupted. Total absence of cIV was accompanied by profound deficiency of cI, documented by decrease in the levels of cI subunits and significantly reduced amount of assembled cI. Supercomplexes assembled from cI, cIII, and cIV were missing in COX4I1 knock-out (KO) due to loss of cIV and decrease in cI amount. Pulse-chase metabolic labeling of mitochondrial DNA (mtDNA)-encoded proteins uncovered a decrease in the translation of cIV and cI subunits. Moreover, partial impairment of mitochondrial protein synthesis correlated with decreased content of mitochondrial ribosomal proteins. In addition, complexome profiling revealed accumulation of cI assembly intermediates, indicating that cI biogenesis, rather than stability, was affected. We propose that attenuation of mitochondrial protein synthesis caused by cIV deficiency represents one of the mechanisms, which may impair biogenesis of cI.

• Keywords
• COX, COX4, OXPHOS, biogenesis interdependency, cI, cIV, cIV assembly, complex I, complexome profiling, knock-out, mitochondria, mitochondrial protein synthesis,
• MeSH
• Glycolysis MeSH
• HEK293 Cells MeSH
• Humans MeSH
• Mitochondrial Diseases metabolism   MeSH
• Mitochondrial Proteins biosynthesis   MeSH
• Oxidative Phosphorylation MeSH
• Protein Subunits metabolism   MeSH
• Protein Biosynthesis * MeSH
• Electron Transport Complex IV metabolism   MeSH
• Oxygen Consumption MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• COX4I1 protein, human MeSH Browser
• Mitochondrial Proteins MeSH
• Protein Subunits MeSH
• Electron Transport Complex IV MeSH

Cytochrome c oxidase (COX), the terminal enzyme of mitochondrial electron transport chain, couples electron transport to oxygen with generation of proton gradient indispensable for the production of vast majority of ATP molecules in mammalian cells. The review summarizes current knowledge of COX structure and function of nuclear-encoded COX subunits, which may modulate enzyme activity according to various conditions. Moreover, some nuclear-encoded subunits posess tissue-specific and development-specific isoforms, possibly enabling fine-tuning of COX function in individual tissues. The importance of nuclear-encoded subunits is emphasized by recently discovered pathogenic mutations in patients with severe mitopathies. In addition, proteins substoichiometrically associated with COX were found to contribute to COX activity regulation and stabilization of the respiratory supercomplexes. Based on the summarized data, a model of three levels of quaternary COX structure is postulated. Individual structural levels correspond to subunits of the i) catalytic center, ii) nuclear-encoded stoichiometric subunits and iii) associated proteins, which may constitute several forms of COX with varying composition and differentially regulated function.

• MeSH
• Cell Nucleus enzymology   genetics   MeSH
• Genome MeSH
• Humans MeSH
• Mitochondrial Diseases enzymology   pathology   MeSH
• Mitochondria enzymology   genetics   MeSH
• Organ Specificity MeSH
• Protein Subunits MeSH
• Electron Transport Complex IV genetics   metabolism   MeSH
• Signal Transduction MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Protein Subunits MeSH
• Electron Transport Complex IV MeSH

Prostate cancer is one of the most prominent cancers diagnosed in males. Contrasting with other cancer types, glucose utilization is not increased in prostate carcinoma cells as they employ different metabolic adaptations involving mitochondria as a source of energy and intermediates required for rapid cell growth. In this regard, prostate cancer cells were associated with higher activity of mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH), the key rate limiting component of the glycerophosphate shuttle, which connects mitochondrial and cytosolic processes and plays significant role in cellular bioenergetics. Our research focused on the role of mGPDH biogenesis and regulation in prostate cancer compared to healthy cells. We show that the 42 amino acid presequence is cleaved from N-terminus during mGPDH biogenesis. Only the processed form is part of the mGPDH dimer that is the prominent functional enzyme entity. We demonstrate that mGPDH overexpression enhances the wound healing ability in prostate cancer cells. As mGPDH is at the crossroad of glycolysis, lipogenesis and oxidative metabolism, regulation of its activity by intramitochondrial processing might represent rapid means of cellular metabolic adaptations.

• Keywords
• GPD2 gene, metabolic adaptation, mitochondrial glycerol-3-phosphate dehydrogenase (EC:1.1.5.3), prostate cancer,
• MeSH
• Glycerolphosphate Dehydrogenase metabolism   MeSH
• HEK293 Cells MeSH
• Humans MeSH
• Mitochondria genetics   metabolism   MeSH
• Cell Line, Tumor MeSH
• Prostatic Neoplasms genetics   metabolism   MeSH
• Transfection MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Glycerolphosphate Dehydrogenase MeSH