Mitochondrial Malate Dehydrogenase Research Articles

Diosmin Prevents Isoproterenol-Induced Heart Mitochondrial Oxidative Stress in Rats.

Cardiac mitochondrial oxidative stress causes mitochondrial damage that plays an important role in the pathology of myocardial infarction. The preventive effects of diosmin on cardiac mitochondrial oxidative stress in isoproterenol-induced myocardial infarcted rats were evaluated. Rats were pretreated with diosmin (10mg/kg body weight) daily for 10days. Myocardial infarction was induced in rats by isoproterenol (100mg/kg body weight) injection twice at an interval of 24h (on 11th and 12th day). Isoproterenol-induced myocardial infarcted rats showed a significant increase in the levels of cardiac diagnostic markers, heart mitochondrial lipid peroxidation, calcium ion, and a significant decrease in the levels of heart mitochondrial glutathione peroxidase, reduced glutathione, glutathione-S-transferase, isocitrate, malate, α-ketoglutarate, and succinate dehydrogenases. Transmission electron microscopic findings revealed damaged mitochondria with loss of cristae, swelling, and vacuolation in isoproterenol-induced rats' heart. Diosmin pretreatment showed significant preventive effects on all the biochemical parameters, and the structure of mitochondria was evaluated. Furthermore, the transmission electron microscopic study confirms the biochemical findings. The antioxidant and negative inotropic effects of diosmin inhibited cardiac mitochondrial oxidative stress and prevented mitochondrial damage in myocardial infarcted rats.

Dl-3-n-butylphthalide protects the heart against ischemic injury and H9c2 cardiomyoblasts against oxidative stress: involvement of mitochondrial function and biogenesis

BackgroundMyocardial infarction (MI) is an acute and fatal condition that threatens human health. Dl-3-n-butylphthalide (NBP) has been used for the treatment of acute ischemic stroke. Mitochondria may play a protective role in MI injury. However, there are few reports on the cardioprotective effect of NBP or the potential mitochondrial mechanism for the NBP-induced protection against cardiac ischemia injury. We investigated the therapeutic effects of NBP in an in vivo MI model and an in vitro oxidative stress model, as well as the potential mitochondrial mechanism.MethodsThis study comprised two different experiments. The aim of experiment 1 was to determine the protective effects of NBP on MI and the underlying mechanisms in vivo. In part 1, myocardial infarct size was measured by staining with 2,3,5-triphenyltetrazoliumchloride (TTC). Myocardial enzymes and mitochondrial enzymes were assayed. The aim of experiment 2 was to investigate the role of NBP in H2O2-induced myocardial ischemic injury in H9c2 cells and to determine the potential mechanism. In part 2, H9c2 cell viability was evaluated. ROS levels, mitochondrial morphology, and mitochondrial membrane potential of H9c2 cells were measured. ATP levels were evaluated using an assay kit; mitochondrial DNA (mtDNA), the expressions of NRF-1 and TFAM, and mitochondrial biogenesis factors were determined.ResultsNBP treatment significantly reduced the infarct ratio, as observed by TTC staining, decreased serum myocardial enzymes in MI, and restored heart mitochondrial enzymes (isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and a-ketoglutarate dehydrogenase (a-KGDH) activities after MI. Moreover, in in vitro studies, NBP significantly increased the viability of H9c2 cells in a dose-dependent manner, reduced cell apoptosis, protected mitochondrial functions, elevated the cellular ATP levels, and promoted H2O2-induced mitochondrial biogenesis in H9c2 cardiomyoblasts.ConclusionCollectively, the results from both the in vivo and in vitro experiments suggested that NBP exerted a cardioprotective effect on cardiac ischemic injury via the regulation of mitochondrial function and biogenesis.

The Enzymology of 2-Hydroxyglutarate, 2-Hydroxyglutaramate and 2-Hydroxysuccinamate and Their Relationship to Oncometabolites.

Many enzymes make “mistakes”. Consequently, repair enzymes have evolved to correct these mistakes. For example, lactate dehydrogenase (LDH) and mitochondrial malate dehydrogenase (mMDH) slowly catalyze the reduction of 2-oxoglutarate (2-OG) to the oncometabolite l-2-hydroxyglutarate (l-2-HG). l-2-HG dehydrogenase corrects this error by converting l-2-HG to 2-OG. LDH also catalyzes the reduction of the oxo group of 2-oxoglutaramate (2-OGM; transamination product of l-glutamine). We show here that human glutamine synthetase (GS) catalyzes the amidation of the terminal carboxyl of both the l- and d- isomers of 2-HG. The reaction of 2-OGM with LDH and the reaction of l-2-HG with GS generate l-2-hydroxyglutaramate (l-2-HGM). We also show that l-2-HGM is a substrate of human ω-amidase. The product (l-2-HG) can then be converted to 2-OG by l-2-HG dehydrogenase. Previous work showed that 2-oxosuccinamate (2-OSM; transamination product of l-asparagine) is an excellent substrate of LDH. Finally, we also show that human ω-amidase converts the product of this reaction (i.e., l-2-hydroxysuccinamate; l-2-HSM) to l-malate. Thus, ω-amidase may act together with hydroxyglutarate dehydrogenases to repair certain “mistakes” of GS and LDH. The present findings suggest that non-productive pathways for nitrogen metabolism occur in mammalian tissues in vivo. Perturbations of these pathways may contribute to symptoms associated with hydroxyglutaric acidurias and to tumor progression. Finally, methods for the synthesis of l-2-HGM and l-2-HSM are described that should be useful in determining the roles of ω-amidase/4- and 5-C compounds in photorespiration in plants.

Cold acclimation alters DNA methylation patterns and confers tolerance to heat and increases growth rate in Brassica rapa.

Epigenetic modifications are implicated in plant adaptations to abiotic stresses. Exposure of plants to one stress can induce resistance to other stresses, a process termed cross-adaptation, which is not well understood. In this study, we aimed to unravel the epigenetic basis of elevated heat-tolerance in cold-acclimated Brassica rapa by conducting a genome-wide DNA methylation analysis of leaves from control (CK) and cold-acclimated (CA) plants. We found that both methylation and demethylation occurred during cold acclimation. Two significantly altered pathways, malate dehydrogenase activity and carbon fixation, and 1562 differentially methylated genes, including BramMDH1, BraKAT2, BraSHM4, and Bra4CL2, were identified in CA plants. Genetic validation and treatment of B. rapa with 5-aza-2-deoxycytidine (Aza) suggested that promoter demethylation of four candidate genes increased their transcriptional activities. Physiological analysis suggested that elevated heat-tolerance and high growth rate were closely related to increases in organic acids and photosynthesis, respectively. Functional analyses demonstrated that the candidate gene BramMDH1 (mMDH: mitochondrial malate dehydrogenase) directly enhances organic acids and photosynthesis to increase heat-tolerance and growth rate in Arabidopsis. However, Aza-treated B. rapa, which also has elevated BramMDH1 levels, did not exhibit enhanced heat-tolerance. We therefore suggest that DNA demethylation alone is not sufficient to increase heat-tolerance. This study demonstrates that altered DNA methylation contributes to cross-adaptation.

Effects of dietary leucine supplementation on the hepatic mitochondrial biogenesis and energy metabolism in normal birth weight and intrauterine growth-retarded weanling piglets.

BACKGROUND/OBJECTIVESThe study was conducted to evaluate the effects of dietary leucine supplementation on mitochondrial biogenesis and energy metabolism in the liver of normal birth weight (NBW) and intrauterine growth-retarded (IUGR) weanling piglets.MATERIALS/METHODSA total of sixteen pairs of NBW and IUGR piglets from sixteen sows were selected according to their birth weight. At postnatal day 14, all piglets were weaned and fed either a control diet or a leucine-supplemented diet for 21 d. Thereafter, a 2 × 2 factorial experimental design was used. Each treatment consisted of eight replications with one piglet per replication.RESULTSCompared with NBW piglets, IUGR piglets had a decreased (P < 0.05) hepatic adenosine triphosphate (ATP) content. Also, IUGR piglets exhibited reductions (P < 0.05) in the activities of hepatic mitochondrial pyruvate dehydrogenase (PDH), citrate synthase (CS), α-ketoglutarate dehydrogenase (α-KGDH), malate dehydrogenase (MDH), and complexes I and V, along with decreases (P < 0.05) in the concentration of mitochondrial DNA (mtDNA) and the protein expression of hepatic peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α). Dietary leucine supplementation increased (P < 0.05) the content of ATP, and the activities of CS, α-KGDH, MDH, and complex V in the liver of piglets. Furthermore, compared to those fed a control diet, piglets given a leucine-supplemented diet exhibited increases (P < 0.05) in the mtDNA content and in the mRNA expressions of sirtuin 1, PGC-1α, nuclear respiratory factor 1, mitochondrial transcription factor A, and ATP synthase, H+ transporting, mitochondrial F1 complex, β polypeptide in liver.CONCLUSIONSDietary leucine supplementation may exert beneficial effects on mitochondrial biogenesis and energy metabolism in NBW and IUGR weanling piglets.

Mutations in MDH2, Encoding a Krebs Cycle Enzyme, Cause Early-Onset Severe Encephalopathy

MDH2 encodes mitochondrial malate dehydrogenase (MDH), which is essential for the conversion of malate to oxaloacetate as part of the proper functioning of the Krebs cycle. We report bi-allelic pathogenic mutations in MDH2 in three unrelated subjects presenting with early-onset generalized hypotonia, psychomotor delay, refractory epilepsy, and elevated lactate in the blood and cerebrospinal fluid. Functional studies in fibroblasts from affected subjects showed both an apparently complete loss of MDH2 levels and MDH2 enzymatic activity close to null. Metabolomics analyses demonstrated a significant concomitant accumulation of the MDH substrate, malate, and fumarate, its immediate precursor in the Krebs cycle, in affected subjects’ fibroblasts. Lentiviral complementation with wild-type MDH2 cDNA restored MDH2 levels and mitochondrial MDH activity. Additionally, introduction of the three missense mutations from the affected subjects into Saccharomyces cerevisiae provided functional evidence to support their pathogenicity. Disruption of the Krebs cycle is a hallmark of cancer, and MDH2 has been recently identified as a novel pheochromocytoma and paraganglioma susceptibility gene. We show that loss-of-function mutations in MDH2 are also associated with severe neurological clinical presentations in children.

150 PROTEOME OF BOVINE CUMULUS CELLS AS RELATED TO OOCYTE MORPHOLOGY AND IN VITRO EMBRYO PRODUCTION

The present study was conducted to study the effect of cumulus-oocyte complex (COC) morphology on subsequent in vitro embryo development and to assess the proteome of their corresponding cumulus cells (CC). Cow ovaries were obtained at an abattoir and COC aspirated from 3–8 mm follicles. The COC were defined as type I (TI): homogeneous ooplasma and ≥4 layers of compact CC; type II (TII): granular ooplasma and ≥4 layers of slight expanded CC. Fifty COC had ~500,000 CC. Cumulus cells were frozen in ammonium bicarbonate and immediately lyophilized for proteome analysis. Other selected COC were matured in vitro in TCM-199-supplemented media for 24 h. After maturation, CC were collected (T24) and processed as described above. The remaining COC were fertilized with sperm from a fertile bull and zygotes, cultured in vitro until Day 7. Ten blastocysts per group were stained (Hoechst 33342) and blastomeres, counted for assessment of embryo quality. The CC proteins were obtained from the following groups: immature type I (TIT0) and type II (TIIT0), and in vitro matured type I (TIT24) and type II (TIIT24). For protein extraction, we used sonication (30 min, 4°C), freezing and unfreezing in liquid nitrogen, and maceration. The CC proteins were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by ESI-MS/MS. Differences in cleavage, embryo rates, and blastomere numbers were analysed by t-test. Protein expression difference was set at 2.5-fold (P &lt; 0.05). In silico protein interactions were investigated using STRING v. 10.0. There were no differences in cleavage (88 ± 4 v. 89 ± 8%) and embryo rates (36 ± 7 v. 33 ± 8%) between COC of TI (n = 220) and TII (n = 161), respectively. Blastomeres were also similar in TI (101) and TII (104) groups. Major proteins expressed in all CC were α-enolase, β-actin, oestradiol 17-β-dehydrogenase 1, glutathione S-transferase, glyceraldehyde 3-phosphate dehydrogenase, heat shock protein β-1, histone H2B type 1-N, histone H4, mitochondrial malate dehydrogenase 2, protein disulfide isomarase A6, triosephosphate isomerase, tubulin α-1C chain, and vimentin. Glyceraldehyde 3-phosphate dehydrogenase appeared to be more expressed in TIT0, whereas tubulin α-1C chain and vimentin had greater expression in TIIT24. As evidenced by in silico analysis, most CC proteins interact among themselves, participating in complex networks involving intracellular signalling and other events. In conclusion, there are no difference in embryo development when using compact and early-expanded COC, indicating that both types can be selected for IVP. Protein profile of cumulus cell may serve as a marker for in vitro embryo competence.

Regulation of human cerebrospinal fluid malate dehydrogenase 1 in sporadic Creutzfeldt-Jakob disease patients.

The identification of reliable diagnostic biomarkers in differential diagnosis of neurodegenerative diseases is an ongoing topic. A previous two-dimensional proteomic study on cerebrospinal fluid (CSF) revealed an elevated level of an enzyme, mitochondrial malate dehydrogenase 1 (MDH1), in sporadic Creutzfeldt-Jakob disease (sCJD) patients. Here, we could demonstrate the expression of MDH1 in neurons as well as in the neuropil. Its levels are lower in sCJD brains than in control brains. An examination of CSF-MDH1 in sCJD patients by ELISA revealed a significant elevation of CSF-MDH1 levels in sCJD patients (independently from the PRNP codon 129 MV genotype or the prion protein scrapie (PrPSc) type) in comparison to controls. In combination with total tau (tau), CSF-MDH1 detection exhibited a high diagnostic accuracy for sCJD diagnosis with a sensitivity of 97.5% and a specificity of 95.6%. A correlation study of MDH1 level in CSF with other neurodegenerative marker proteins revealed a significant positive correlation between MDH1 concentration with tau, 14-3-3 and neuron specific enolase level. In conclusion, our study indicated the potential of MDH1 in combination with tau as an additional biomarker in sCJD improving diagnostic accuracy of tau markedly.

Comparative Genome-Wide Analysis of the Malate Dehydrogenase Gene Families in Cotton.

Malate dehydrogenases (MDHs) play crucial roles in the physiological processes of plant growth and development. In this study, 13 and 25 MDH genes were identified from Gossypium raimondii and Gossypium hirsutum, respectively. Using these and 13 previously reported Gossypium arboretum MDH genes, a comparative molecular analysis between identified MDH genes from G. raimondii, G. hirsutum, and G. arboretum was performed. Based on multiple sequence alignments, cotton MDHs were divided into five subgroups: mitochondrial MDH, peroxisomal MDH, plastidial MDH, chloroplastic MDH and cytoplasmic MDH. Almost all of the MDHs within the same subgroup shared similar gene structure, amino acid sequence, and conserved motifs in their functional domains. An analysis of chromosomal localization suggested that segmental duplication played a major role in the expansion of cotton MDH gene families. Additionally, a selective pressure analysis indicated that purifying selection acted as a vital force in the evolution of MDH gene families in cotton. Meanwhile, an expression analysis showed the distinct expression profiles of GhMDHs in different vegetative tissues and at different fiber developmental stages, suggesting the functional diversification of these genes in cotton growth and fiber development. Finally, a promoter analysis indicated redundant but typical cis-regulatory elements for the potential functions and stress activity of many MDH genes. This study provides fundamental information for a better understanding of cotton MDH gene families and aids in functional analyses of the MDH genes in cotton fiber development.

THERAPEUTIC EFFECT OF TRIDHAM AND 1,2,3,4,6-PENTA-O-GALLOYL-Β-D-GLUCOSE ON ALTERED ENERGY METABOLISM IN MAMMARY CARCINOMA BEARING RATS

ABSTRACT Objective: Emerging evidence indicates that cancer is primarily a metabolic disease involving disturbances in energy production, and hence, reprogramming of cellular energy metabolism is deemed to be one of the principal hallmarks of cancer. Tridham (TD) has been used by traditional practitioners of Siddha medicine against various ailments. Hence, the present study has been designed to evaluate the therapeutic effect of TD on altered energy metabolism in mammary carcinoma-bearing rats. Methods: Adult female albino rats of Sprague-Dawley strain weighing 170-190 g were used and 7,12-dimethylbenzeneanthracene (DMBA) was used for induction of mammary carcinoma and rats were divided into seven groups. Group I - control rats, Group II - DMBA-induced rats, Group III - DMBA- and TD-treated rats, Group IV - DMBA- and 1,2,3,4,6-Penta-O-galloyl-β-d-glucose (PGG)-treated rats, Group V - DMBA- and cyclophosphamide-treated rats, Groups VI and VII are TD and PGG control rats. Results: Significant (p<0.05) increase in the glycolytic enzymes, hexokinase, phosphoglucoisomerase and aldolase, was observed in tumor-bearing rats whereas gluconeogenic enzymes, glucose-6-phosphatase and fructose-1,6-biphosphatase, were significantly decreased. The activities of the mitochondrial Krebs cycle enzymes, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase, and respiratory chain enzymes, nicotinamide dinucleotide dehydrogenase and cytochrome c oxidase, were significantly reduced in tumor tissue of the mammary carcinoma-bearing rats. These biochemical disturbances were effectively counteracted by TD and PGG which restore the activities of all these enzymes to the respective control levels. Conclusion: TD and PGG effectively ameliorated the altered glucose metabolism resulting in the regression of breast cancer. Keywords: Breast cancer, Cancer cachexia, Carbohydrate-metabolizing enzymes, Krebs cycle.

Direct Evidence for Metabolon Formation and Substrate Channeling in Recombinant TCA Cycle Enzymes.

Supramolecular assembly of enzymes into metabolon structures is thought to enable efficient transport of reactants between active sites via substrate channeling. Recombinant versions of porcine citrate synthase (CS), mitochondrial malate dehydrogenase (mMDH), and aconitase (Aco) were found to adopt a homogeneous native-like metabolon structure in vitro. Site-directed mutagenesis performed on highly conserved arginine residues located in the positively charged channel connecting mMDH and CS active sites led to the identification of CS(R65A) which retained high catalytic efficiency. Substrate channeling between the CS mutant and mMDH was severely impaired and the overall channeling probability decreased from 0.99 to 0.023. This work provides direct mechanistic evidence for the channeling of reaction intermediates, and disruption of this interaction would have important implications on the control of flux in central carbon metabolism.

Methanol Expression Regulator 1 (Mxr1p) Is Essential for the Utilization of Amino Acids as the Sole Source of Carbon by the Methylotrophic Yeast, Pichia pastoris

Unlike Saccharomyces cerevisiae, the methylotrophic yeast Pichia pastoris can assimilate amino acids as the sole source of carbon and nitrogen. It can grow in media containing yeast extract and peptone (YP), yeast nitrogen base (YNB) + glutamate (YNB + Glu), or YNB + aspartate (YNB + Asp). Methanol expression regulator 1 (Mxr1p), a zinc finger transcription factor, is essential for growth in these media. Mxr1p regulates the expression of several genes involved in the utilization of amino acids as the sole source of carbon and nitrogen. These include the following: (i) GDH2 encoding NAD-dependent glutamate dehydrogenase; (ii) AAT1 and AAT2 encoding mitochondrial and cytosolic aspartate aminotransferases, respectively; (iii) MDH1 and MDH2 encoding mitochondrial and cytosolic malate dehydrogenases, respectively; and (iv) GLN1 encoding glutamine synthetase. Synthesis of all these enzymes is regulated by Mxr1p at the level of transcription except GDH2, whose synthesis is regulated at the level of translation. Mxr1p activates the transcription of AAT1, AAT2, and GLN1 in cells cultured in YP as well as in YNB + Glu media, whereas transcription of MDH1 and MDH2 is activated in cells cultured in YNB + Glu but not in YP. A truncated Mxr1p composed of 400 N-terminal amino acids activates transcription of target genes in cells cultured in YP but not in YNB + Glu. Mxr1p binds to Mxr1p response elements present in the promoters of AAT2, MDH2, and GLN1 We conclude that Mxr1p is essential for utilization of amino acids as the sole source of carbon and nitrogen, and it is a global regulator of multiple metabolic pathways in P. pastoris.

Loss of Mitochondrial Malate Dehydrogenase Activity Alters Seed Metabolism Impairing Seed Maturation and Post-Germination Growth in Arabidopsis.

Mitochondrial malate dehydrogenase (mMDH; EC 1.1.1.37) has multiple roles; the most commonly described is its catalysis of the interconversion of malate and oxaloacetate in the tricarboxylic acid cycle. The roles of mMDH in Arabidopsis (Arabidopsis thaliana) seed development and germination were investigated in mMDH1 and mMDH2 double knockout plants. A significant proportion of mmdh1mmdh2 seeds were nonviable and developed only to torpedo-shaped embryos, indicative of arrested seed embryo growth during embryogenesis. The viable mmdh1mmdh2 seeds had an impaired maturation process that led to slow germination rates as well as retarded post-germination growth, shorter root length, and decreased root biomass. During seed development, mmdh1mmdh2 showed a paler green phenotype than the wild type and exhibited deficiencies in reserve accumulation and reduced final seed biomass. The respiration rate of mmdh1mmdh2 seeds was significantly elevated throughout their maturation, consistent with the previously reported higher respiration rate in mmdh1mmdh2 leaves. Mutant seeds showed a consistently higher content of free amino acids (branched-chain amino acids, alanine, serine, glycine, proline, and threonine), differences in sugar and sugar phosphate levels, and lower content of 2-oxoglutarate. Seed-aging assays showed that quiescent mmdh1mmdh2 seeds lost viability more than 3 times faster than wild-type seeds. Together, these data show the important role of mMDH in the earliest phases of the life cycle of Arabidopsis.

Adenine nucleotide-dependent and redox-independent control of mitochondrial malate dehydrogenase activity in Arabidopsis thaliana

Mitochondrial metabolism is important for sustaining cellular growth and maintenance; however, the regulatory mechanisms underlying individual processes in plant mitochondria remain largely uncharacterized. Previous redox-proteomics studies have suggested that mitochondrial malate dehydrogenase (mMDH), a key enzyme in the tricarboxylic acid (TCA) cycle and redox shuttling, is under thiol-based redox regulation as a target candidate of thioredoxin (Trx). In addition, the adenine nucleotide status may be another factor controlling mitochondrial metabolism, as respiratory ATP production in mitochondria is believed to be influenced by several environmental stimuli. Using biochemical and reverse-genetic approaches, we addressed the redox- and adenine nucleotide-dependent regulation of mMDH in Arabidopsis thaliana. Recombinant mMDH protein formed intramolecular disulfide bonds under oxidative conditions, but these bonds did not have a considerable effect on mMDH activity. Mitochondria-localized o-type Trx (Trx-o) did not facilitate re-reduction of oxidized mMDH. Determination of the in vivo redox state revealed that mMDH was stably present in the reduced form even in Trx-o-deficient plants. Accordingly, we concluded that mMDH is not in the class of redox-regulated enzymes. By contrast, mMDH activity was lowered by adenine nucleotides (AMP, ADP, and ATP). Each adenine nucleotide suppressed mMDH activity with different potencies and ATP exerted the largest inhibitory effect with a significantly lower Ki. Correspondingly, mMDH activity was inhibited by the increase in ATP/ADP ratio within the physiological range. These results suggest that mMDH activity is finely controlled in response to variations in mitochondrial adenine nucleotide balance.

Reduced mitochondrial malate dehydrogenase activity has a strong effect on photorespiratory metabolism as revealed by 13C labelling.

Mitochondrial malate dehydrogenase (mMDH) catalyses the interconversion of malate and oxaloacetate (OAA) in the tricarboxylic acid (TCA) cycle. Its activity is important for redox control of the mitochondrial matrix, through which it may participate in regulation of TCA cycle turnover. In Arabidopsis, there are two isoforms of mMDH. Here, we investigated to which extent the lack of the major isoform, mMDH1 accounting for about 60% of the activity, affected leaf metabolism. In air, rosettes of mmdh1 plants were only slightly smaller than wild type plants although the fresh weight was decreased by about 50%. In low CO2 the difference was much bigger, with mutant plants accumulating only 14% of fresh weight as compared to wild type. To investigate the metabolic background to the differences in growth, we developed a (13)CO2 labelling method, using a custom-built chamber that enabled simultaneous treatment of sets of plants under controlled conditions. The metabolic profiles were analysed by gas- and liquid- chromatography coupled to mass spectrometry to investigate the metabolic adjustments between wild type and mmdh1 The genotypes responded similarly to high CO2 treatment both with respect to metabolite pools and (13)C incorporation during a 2-h treatment. However, under low CO2 several metabolites differed between the two genotypes and, interestingly most of these were closely associated with photorespiration. We found that while the glycine/serine ratio increased, a concomitant altered glutamine/glutamate/α-ketoglutarate relation occurred. Taken together, our results indicate that adequate mMDH activity is essential to shuttle reductants out from the mitochondria to support the photorespiratory flux, and strengthen the idea that photorespiration is tightly intertwined with peripheral metabolic reactions.

Proteomic analysis for early neurodegenerative biomarker detection in an animal model.

The exposure to xenobiotics in the early stages of life represents the most important component in the etiology of many neurodegenerative disorders. Proteomic analysis of plasma and brain samples from early life treated animal model was performed in order to identify early biomarkers of neurodegeneration. Two-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry identified four proteins in the plasma of adolescent rats that deviated from the control group. Low expression levels of transthyretin and plasma transferrin, and the absence of long-chain fatty acid transport 1 were measured. On the other hand, the same proteomic approach was done on striatum of an adult rat model of neurodegeneration. Mitochondrial aspartate aminotransferase and voltage-dependent anion channel were under expressed, while mitochondrial malate dehydrogenase, myelin basic protein and ubiquitin-60S ribosomal protein L40 were absent in striatum of animal model compared to control group. Data show that early biomarkers for the diagnosis of neurodegeneration can be obtained by proteomic analysis, starting from adolescent age and the results highlight the time frame for the onset of neurodegeneration due to early exposure to xenobiotics.

Visnagin-a new protectant against doxorubicin cardiotoxicity? Inhibition of mitochondrial malate dehydrogenase 2 (MDH2) and beyond.

Doxorubicin (DOX) is a broad-spectrum and potent anthracycline antibiotic that has been widely used since 1960s as a chemotherapeutic agent to treat a variety of human cancers (1). Despite its superior anti-cancer efficacy, the clinical use of DOX is often limited by dose-dependent cardiotoxicity, which may lead to irreversible dilated cardiomyopathy and congestive heart failure (2,3). Currently predominant theories for explaining DOX cardiotoxicity include the DOX-induced increase of oxidative stress in cardiomyocytes (4), alteration of mitochondrial energetics (5,6), and direct effect on DNA. Particularly, anthracyclines promote the formation of reactive oxygen species (ROS) through redox cycling of their aglycones and anthracyclineiron complexes (7). Other suggested contributing factors to DOX cardiotoxicity comprise platelet-activating factor, prostaglandins, histamine, calcium, and C-13 hydroxy anthracycline metabolites, etc. (8,9). DOX is metabolized to doxorubicinol, which is implicated for its cardiotoxicity, possibly by causing perturbation of the iron homeostasis (4).

Cr-induced changes in leaf protein profile, ultrastructure and photosynthetic traits in the two contrasting tobacco genotypes

Soil Cr contamination has emerged as an increasing problem worldwide. To investigate the genotypic difference on the effect of Cr in tobacco, Hydroponic experiments were performed, assessing changes in proteomes, transcriptional features as well as the ultrastructure and photosynthetic characteristics of two contrasting tobacco genotypes Guiyan 1 (Cr-tolerant) and Yunyan 2 (Cr-sensitive) under Cr exposure. Transmission electron microscopy observation depicted that Guiyan 1 was less influenced by Cr stress than Yunyan 2. Leaves of Guiyan 1 exhibited relatively well composed arrangement of photosynthetic apparatus as compared with that of Yunyan 2. A total of 86/74 and 107/77 proteins showed more-/less-abundance following Cr treatment in Guiyan 1 and Yunyan 2. Twelve Cr-tolerance-associated proteins were identified, using two-dimensional gel electrophoresis coupled with mass spectrometry, whose expressions were significantly induced in Guiyan 1 leaves but down-regulated/unchanged in Yunyan 2, or unchanged in Guiyan 1 but down-regulated in Yunyan 2 under 100 µM Cr stress. They are including mitochondrial processing peptidase, dehydrin, superoxide dismutase, adenine phosphoribosyl transferase, mitochondrial malate dehydrogenase proteins. Based upon their functions, they are categorized in four groups: stress response, energy, RNA-binding and metabolism related proteins. Furthermore, the expression patterns of four Cr-responsive proteins were validated by quantitative real-time PCR. The data extend our knowledge to understand the underlying Cr tolerance mechanisms and provide an insight into possible utilization of elite genetic resources for the development of Cr tolerant tobacco genotypes.

The mitochondrial malate dehydrogenase 1 gene GhmMDH1 is involved in plant and root growth under phosphorus deficiency conditions in cotton.

Cotton, an important commercial crop, is cultivated for its natural fibers, and requires an adequate supply of soil nutrients, including phosphorus, for its growth. Soil phosporus exists primarily in insoluble forms. We isolated a mitochondrial malate dehydrogenase (MDH) gene, designated as GhmMDH1, from Gossypium hirsutum L. to assess its effect in enhancing P availability and absorption. An enzyme kinetic assay showed that the recombinant GhmMDH1 possesses the capacity to catalyze the interconversion of oxaloacetate and malate. The malate contents in the roots, leaves and root exudates was significantly higher in GhmMDH1-overexpressing plants and lower in knockdown plants compared with the wild-type control. Knockdown of GhmMDH1 gene resulted in increased respiration rate and reduced biomass whilst overexpression of GhmMDH1 gave rise to decreased respiration rate and higher biomass in the transgenic plants. When cultured in medium containing only insoluble phosphorus, Al-phosphorus, Fe-phosphorus, or Ca-phosphorus, GhmMDH1-overexpressing plants produced significantly longer roots and had a higher biomass and P content than WT plants, however, knockdown plants showed the opposite results for these traits. Collectively, our results show that GhmMDH1 is involved in plant and root growth under phosphorus deficiency conditions in cotton, owing to its functions in leaf respiration and P acquisition.

Discovery of Predictive Biomarkers for Litter Size in Boar Spermatozoa*

Conventional semen analysis has been used for prognosis and diagnosis of male fertility. Although this tool is essential for providing initial quantitative information about semen, it remains a subject of debate. Therefore, development of new methods for the prognosis and diagnosis of male fertility should be seriously considered for animal species of economic importance as well as for humans. In the present study, we applied a comprehensive proteomic approach to identify global protein biomarkers in boar spermatozoa in order to increase the precision of male fertility prognoses and diagnoses. We determined that l-amino acid oxidase, mitochondrial malate dehydrogenase 2, NAD (MDH2), cytosolic 5'-nucleotidase 1B, lysozyme-like protein 4, and calmodulin (CALM) were significantly and abundantly expressed in high-litter size spermatozoa. We also found that equatorin, spermadhesin AWN, triosephosphate isomerase (TPI), Ras-related protein Rab-2A (RAB2A), spermadhesin AQN-3, and NADH dehydrogenase [ubiquinone] iron-sulfur protein 2 (NDUFS2) were significantly and abundantly expressed in low-litter size spermatozoa (>3-fold). Moreover, RAB2A, TPI, and NDUFS2 were negatively correlated with litter size, whereas CALM and MDH2 were positively correlated. This study provides novel biomarkers for the prediction of male fertility. To the best of our knowledge, this is the first work that shows significantly increased litter size using male fertility biomarkers in a field trial. Moreover, these protein markers may provide new developmental tools for the selection of superior sires as well as for the prognosis and diagnosis of male fertility.