Isocitrate Dehydrogenase Activity Research Articles

Thymoquinone Alleviates Cadmium Induced Stress in Germinated Lens culinaris Seeds by Reducing Oxidative Stress and Increasing Antioxidative Activities.

This study investigated the effect of thymoquinone on seeds germination and young seedlings of lentils under cadmium (Cd) stress (300 µM). Three different concentrations (10 µM, 1 µM, and 0.1 µM) of thymoquinone were applied. Our results indicated that thymoquinone has a positive effect on several physiological and biochemical parameters on seeds germination and young seedlings of lentils under Cd stress, which led to enhancing their growth. A significant increase in shoot and root length, fresh and dry weight, and chlorophyll content was observed in the treated plants compared to the control plants. However, the thymoquinone treatment significantly reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents compared to untreated roots and seedlings under Cd-stress. Nevertheless, our results show that the thymoquinone significantly improved the activities of enzymes involved in antioxidant response, including superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), thioredoxin reductase (TrxR), and ascorbate peroxidase (APX). We have also studied the activities of isocitrate dehydrogenase (ICDH) and malate dehydrogenase (MDH); ICDH was increased significantly in roots and seedlings in the presence of different doses of thymoquinone. However, the activity MDH was increased only in roots. Our results suggest that the application of thymoquinone could mitigate cadmium induced oxidative stress.

Metabolomic responses in livers of female and male zebrafish (Danio rerio) following prolonged exposure to environmental levels of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnONPs) are widespread pollutants that are present in diverse environmental samples. Here, we determined metabolomic and bioenergetic responses in the liver of female and male zebrafish exposed to a prolonged environmentally relevant concentration of ZnONPs. Metabolome analysis revealed that exposure to 500 μg/L ZnONPs reduced the abundance of metabolites in the tricarboxylic acid (TCA) cycle by modulating the activities of rate-limiting enzymes α-ketoglutarate dehydrogenase and isocitrate dehydrogenase. Moreover, oxidative phosphorylation (OXPHOS) was negatively impacted in the liver based upon decreased activities of mitochondrial Complex I and V in both female and male livers. Our results revealed that bioenergetic responses were not attributed to dissolved Zn2+ and were not sex-specific. However, the metabolic responses in liver following exposure to ZnONPs did show sex-specific responses. Females exposed to ZnONPs compensated for the energetic stress via increasing fatty acids and amino acids metabolism, while males compensated to ZnONPs exposure by adjusting amino acids metabolism, based upon transcript profiles. This study demonstrates that zebrafish adjust the transcription of metabolic enzymes in the liver to compensate for metabolic disruption following ZnONPs exposure. Taken together, this study contributes to a comprehensive understanding of risks related to ZnONPs exposure in relation to metabolic activity in the liver.Environmental implication Zinc oxide nanoparticles (ZnONPs) are widely used in industry and are subsequently released into environments. However, biological responses between female and male following ZnONPs exposure has never been compared. Our data revealed for the first time that female and male zebrafish showed comparable bioenergetic responses, but different metabolic responses to ZnONPs at an environmentally relevant dose. Females compensated for the energetic stress via increasing fatty acids and amino acids metabolism, while males compensated to ZnONPs exposure by adjusting amino acids metabolism in livers. This study reveals that sex may be an important variable to consider in risk assessments of nanoparticles released into environments.

Nitric Oxide Negatively Regulates the Rapid Formation of Pleurotus ostreatus Primordia by Inhibiting the Mitochondrial aco Gene.

Nitric oxide (NO) is as a signaling molecule that participates in the regulation of plant development and in a number of physiological processes. However, the function and regulatory pathway of NO in the growth and development of edible mushrooms are still unknown. This study found that NO played a negative role in the transformation of Pleurotus ostreatus from vegetative growth to reproductive growth by the exogenous addition of NO donors and scavengers. Further studies showed that NO can inhibit the gene expression and enzyme activity of aconitase (ACO). Moreover, the overexpression (OE) of mitochondrial aco and RNA interference (RNAi) confirmed that ACO participates in the regulation of the primordia formation rate. The effects of aco OE and RNAi on the tricarboxylic acid (TCA) cycle and energy metabolism were further measured. The results showed that RNAi-aco mutant strains can affect the enzyme activities of isocitrate dehydrogenase of mitochondria (ICDHm) and α-ketoglutarate dehydrogenase (α-KGDH) in the TCA cycle, thereby reducing the production of nicotinamide adenine dinucleotide (NADH) in the TCA cycle, decreasing the contents of adenosine triphosphate (ATP) and hydrogen peroxide (H2O2), and negatively regulating the rapid formation of primordia. In addition, H2O2 was significantly increased during the transformation from vegetative growth to reproductive growth of P. ostreatus. Additionally, the exogenous addition of H2O2 and its scavengers further confirmed the positive regulation by H2O2 in primordia formation. This study shows that during the growth and development of P. ostreatus, NO can inhibit the expression of the mitochondrial aco gene and ACO protein in the TCA cycle, reduce the production of ATP and H2O2 in the respiratory chain, and negatively regulate the rate of primordia formation.

Protective effect of baicalin on methotrexate-induced mitochondrial damage in testicular tissues of rats

Methotrexate (MTX) is commonly used as a chemotherapeutic drug against cancer but its efficacy is limited due to its side effects. Baicalin is a flavonoid that has potent antioxidant properties. This study aimed to evaluate baicalin’s protective effect on MTX-induced mitochondrial damage in testicular tissues of rats. Twenty-four male Wistar rats were distributed into four groups: control, MTX, MTX + baicalin, and baicalin alone. The activities of enzymes such as catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase was significantly lowered in the MTX treated group, compared to the other groups. Concomitantly, MTX group also showed elevated the levels of reactive oxygen species and thiobarbituric acid reactive substances in the testicular mitochondria. Furthermore, MTX group also showed reduced the activities of tricarboxylic acid (TCA) cycle enzymes, i.e., succinate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, and alpha-ketoglutarate dehydrogenase. The actions of electron transport chain (ETC) complexes (I-IV), as well as mitochondrial membrane potential (MMP), were also reduced the MTX group. However, baicalin treatment reversed the damaging effect of MTX in the mitochondria of testicular tissues. The baicalin treatment potentially reduced the damaging impact of MTX in isolated mitochondria from testicular tissues. Thus, the current study revealed that the baicalin has conspicuous potential to attenuate the MTX induced mitochondrial damage in rat’s testicular tissues.

Impact of olfactory and visual cues of soybean aphid on the metabolism and stress resistance of Orius sauteri (Poppius)

Orius sauteri (Poppius) is the main natural enemy of Aphis glycines (Matsumura) and plays an important role in the biological control of vegetables, forestry, flowers, and farmland ecosystems. In this study, O. sauteri could sense the cues of prey (soybean aphid, Aphis glycines Matsumura) but could not hunt prey. Persistent prey cues could stimulate the olfactory and visual senses and induce the regulation of various metabolic reactions. The activation of food signals increases resistance to starvation stress. To investigate the regulatory methods of prey cues in O. sauteri, we employed an Enzyme-Linked Immunosorbent Assay (ELISA) to detect changes in important enzymes in physiological processes such as energy supply, oxidative stress resistance, and degradation of prey stimulus cues. We found that pyruvate kinase activity was stimulated after O. sauteri smelled the soybean aphid. The peak pyruvate kinase activity in the unfed group was observed after 10 min in the smell treatment group and control group. The first peak value was 28.88 % higher than the other peak values. The peak of enzyme activity in the sight treatment group appeared at 30 min, and it was 29.61 % greater than the peak value of the control group. Furthermore, the expression of HSP70 protein and isocitrate dehydrogenase activity, which are linked to insect stress tolerance, increased to a peak and then quickly declined with olfactory or visual perception time. We also found that carboxylesterase, glutathione S-transferase and acetylcholinesterase activities first increased and then decreased after O. sauteri smelled the soybean aphid. The increased enzyme activity might be linked to resistance to starvation stress and nervous system protection. The olfactory and visual senses of O. sauteri could detect the stimulus cues from soybean aphids which have different regulation effects on key enzymes in physiological processes. The activities of pyruvate kinase, isocitrate dehydrogenase, carboxylesterase, glutathione S-transferase, and acetylcholinesterase were preferentially stimulated by olfactory by visual cues. Visual cues stimulated HSP70 protein expression more than olfactory cues. With the prolongation of food cue sensing time, the intensity of regulation of enzyme activity by the two sensing methods gradually tended to the same level. These results could help us understand the predation and regulation response of O. sauteri to soybean aphids. It provided a reference for the efficient biological control of soybean aphids using O. sauteri.

Synchronised interaction of carbon and nitrogen provides drought tolerance in Cyamopsis tetragonoloba

Drought is a major adverse environmental factor that limits plant productivity. Concomitant assimilation of carbon (C) and nitrogen (N) in illuminated leaves requires the regulated partitioning of reductant and photosynthate to sustain the demands of amino acid and carbohydrate biosynthesis. The short-term exposure to drought and its responses of photosynthesis and photosynthate partitioning to N enrichment was studied in Cyamopsis tetragonoloba (L.) Taub (guar). Four contrasting varieties of guar, HG-563, RGC-986 (drought-tolerant) and RGC-471, Varsha (drought-sensitive) were subjected to 15 days water stress and leaf tissues were studied in order to contemplate the counter strategy engaged under drought conditions. In guar plants, sensors trigger a signalling cascade that activates numerous proteins to induce the expression of certain genes involved in carbon and nitrogen metabolism.The levels of glucose, starch, and Glutamate dehydrogenase (GDH), Aspartate aminotransferase (AspAT), isocitrate dehydrogenase (ICDH), Nitrate Reductase (NR), and Nitrite reductase (NiR) activities were determined biochemically during 15 days drought treatment, at three stages. Further, the carbon (oxidative phosphorylation and TCA cycle) - nitrogen metabolic pathway interaction was studied at the molecular level. The respiratory pathway genes were upregulated, while the nitrogen metabolic pathway genes were downregulated under all stages of drought in guar plants. The physiological, biochemical and molecular data suggests that the high rates of dark respiration was insufficient to provide extra carbon required to assist amino acid synthesis but rather sufficed by a rapid metamorphosis in the photosynthetic carbon partitioning to amino acid metabolism via the nitrogen metabolism. • Drought causes NADH DEHYDROGENASE gene to escalate dark respiration. • Nitrogen assimilation reduces under drought in leguminous Cyamopsis tetragonoloba. • Drought triggers protein kinase cascade signalling in guar plants. • Drought regulates nitrogen metabolic genes in guar. • Drought triggers increase in sugar content at the cost of amino acids.

Cholesterol accumulation induced by acetylated LDL exposure modifies the enzymatic activities of the TCA cycle without impairing the respiratory chain functionality in macrophages

The unregulated uptake of modified low-density lipoproteins (LDL) by macrophages leads to foam cell formation, promoting atherosclerotic plaque progression. The cholesterol efflux capacity of macrophages by the ATP-Binding Cassette transporters depends on the ATP mitochondrial production. Therefore, the mitochondrial function maintenance is crucial in limiting foam cell formation. Thus, we aimed to investigate the mechanisms involved in the mitochondrial dysfunction that may occur in cholesterol-laden macrophages.We incubated THP-1 macrophages with acetylated LDL (acLDL) to obtain cholesterol-laden cells or with mildly oxidized LDL (oxLDL) to generate cholesterol- and oxidized lipids-laden cells. Cellular cholesterol content was measured in each condition. Mitochondrial function was evaluated by measurement of several markers of energetic metabolism, oxidative phosphorylation, oxidative stress, mitochondrial biogenesis and dynamics.OxLDL-exposed macrophages exhibited a significantly reduced mitochondrial respiration and complexes I and III activities, associated to an oxidative stress state and a reduced mitochondrial DNA copy number. Meanwhile, acLDL-exposed macrophages featured an efficient oxidative phosphorylation despite the decreased activities of aconitase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.Our study revealed that mitochondrial function was differently impacted according to the nature of modified LDL. Exposure to cholesterol and oxidized lipids carried by oxLDL leads to a mitochondrial dysfunction in macrophages, affecting the mitochondrial respiratory chain functional capacity, whereas the cellular cholesterol enrichment induced by acLDL exposure results in a tricarboxylic acid cycle shunt while maintaining mitochondrial energetic production, reflecting a metabolic adaptation to cholesterol intake. These new mechanistic insights are of direct relevance to the understanding of the mitochondrial dysfunction in foam cells.

Type I interferon antagonism of the JMJD3-IRF4 pathway modulates macrophage activation and polarization.

Metabolic adaptations can directly influence the scope and scale of macrophage activation and polarization. Here we explore the impact of type I interferon (IFNβ) on macrophage metabolism and its broader impact on cytokine signaling pathways. We find that IFNβ simultaneously increased the expression of immune-responsive gene 1 and itaconate production while inhibiting isocitrate dehydrogenase activity and restricting α-ketoglutarate accumulation. IFNβ also increased the flux of glutamine-derived carbon into the tricarboxylic acid cycle to boost succinate levels. Combined, we identify that IFNβ controls the cellular α-ketoglutarate/succinate ratio. We show that by lowering the α-ketoglutarate/succinate ratio, IFNβ potently blocks the JMJD3-IRF4-dependent pathway in GM-CSF and IL-4 activated macrophages. The suppressive effects of IFNβ on JMJD3-IRF4-dependent responses, including M2 polarization and GM-CSF-induced inflammatory pain, were reversed by supplementation with α-ketoglutarate. These results reveal that IFNβ modulates macrophage activation and polarization through control of the cellular α-ketoglutarate/succinate ratio.

Concentration-dependent dual effects of exogenous sucrose on nitrogen metabolism in Andrographis paniculata

The effects of exogenous sucrose (Suc) concentrations (0, 0.5, 1, 5, 10 mmol L−1) on carbon (C) and nitrogen (N) metabolisms were investigated in a medicinal plant Andrographis paniculata (Chuanxinlian). Suc application with the concentration of 0.5–5 mmol L−1 significantly promoted plant growth. In contrast, 10 mmol L−1 Suc retarded plant growth and increased contents of anthocyanin and MDA and activity of SOD in comparison to 0.5–5 mmol L−1 Suc. Suc application increased contents of leaf soluble sugar, reducing sugar and trerhalose, as well as isocitrate dehydrogenase (ICDH) activity, increasing supply of C-skeleton for N assimilation. However, total leaf N was peaked at 1 mmol L−1 Suc, which was consistent with root activity, suggesting that exogenous Suc enhanced root N uptake. At 10 mmol L−1 Suc, total leaf N and activities of glutamine synthase (GS), glutamate synthase (GOGAT), NADH-dependent glutamate dehydrogenase (NADH-GDH) and glutamic–pyruvic transaminase (GPT) were strongly reduced but NH4+ concentration was significantly increased. The results revealed that exogenous Suc is an effective stimulant for A. paniculata plant growth. Low Suc concentration (e.g. 1 mmol L−1) increased supply of C-skeleton and promoted N uptake and assimilation in A. paniculata plant, whereas high Suc concentration (e.g. 10 mmol L−1) uncoupled C and N metabolisms, reduced N metabolism and induced plant senescence.

Acetate-based production of itaconic acid with Corynebacterium glutamicum using an integrated pH-coupled feeding control

To date, most bio-based products of industrial biotechnology stem from sugar-based carbon sources originating from food and feed competing resources. Exemplary for bioproducts converted from glucose, the potential C5 platform chemical itaconic acid is presently produced by the filamentous fungus Aspergillus terreus. Here, an engineered strain of the industrial platform organism Corynebacterium glutamicum ATCC 13032 was used for acetate-based production of itaconic acid to overcome current production difficulties. For this purpose, C. glutamicum ICDR453C (pEKEx2-malEcadopt) with a mutated icd variant for reduced isocitrate dehydrogenase activity was constructed harbouring pEKEx2-malEcadopt, that includes a cis-aconitate dehydrogenase gene originating from A. terreus. Overall, a peak volumetric productivity of 1.01 gL−1h−1 was achieved resulting in an itaconate titer of 29.2 g/L, by using an integrated pH-coupled acetate feeding control in a fed-batch process without base titration. The results support the high potential of acetate as alternative substrate for bioproduction.

A metabolic perspective into antimicrobial tolerance and resistance

A metabolic perspective into antimicrobial tolerance and resistance

A biochemical, physiological and molecular evaluation of how the herbicide 2, 4-dichlorophenoxyacetic acid intercedes photosynthesis and diazotrophy in the cyanobacterium Nostoc muscorum Meg 1.

Among the non-target microorganisms residing in crop fields that are potentially vulnerable to herbicides are cyanobacteria. They contribute to the maintenance of soil quality and fertility and hence are considered to be an important component of soil microflora. Consequently, the present study was aimed to check the influence of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on some major parameters of carbon (CO2) and nitrogen (N2) fixations of a cyanobacterium Nostoc muscorum Meg 1 isolated from a rice field in Cherrapunji, Meghalaya, India. These include various photosynthetic pigments, the oxygen-evolving complex activity of the PSII, the protein contents of RuBisCO, D1 protein, isocitrate dehydrogenase (IDH), nitrogenase and glutamine synthetase (GS) enzymes, the heterocyst percentage, nitrogenase and GS enzyme activities, and production of total proteins and carbohydrates in the cyanobacterium in a varying range of 50 to 125 ppm doses of 2,4-D. The mRNA levels of several proteins were also analyzed. Besides carotenoid concentration that enhanced at 50 ppm, all other parameters were compromised by 2,4-D in a dose-dependent manner resulting in a reduction in photosynthetic and N2-fixing activities. The negative effect on N2-fixation was partly due to compromised IDH activity. RT-PCR analysis further showed that these negative effects were initiated at transcription levels as mRNA contents of all enzymes studied were found compromised under 2,4-D exposure. The scanning and transmission electron microscopy further revealed herbicide induced adverse changes in the morphology and ultrastructure of the organism. The significance of the work lies in its detailed analysis of the effect of 2,4-D at biochemical, physiological, and molecular levels.

Вплив мексидолу на глутатіонову систему мозку щурів при моделюванні хвороби Паркінсона

We studied the effects of mexidol (3-oxy-6-methyl-2-ethylpiridine succinate) on the antioxidant glutathione system in rat brain mitochondria in experimental Parkinson’s disease induced by rotenone administration. Wistar rats were divided into the following groups of 6 in each: I - intact rats (control); II - rotenone (3 mg/kg per day) was injected subcutaneously for 2 weeks; III - after rotenone intoxication, mexidol (50 mg/kg per day) was injected intraperitoneally for 2 weeks. In the suspension of brain mitochondria, the activity of NADH dehydrogenase (complex I of the mitochondrial respiratory chain), content of the active products of 2-thiobarbituric acid (TBA-AP), the reduced (GSH) and oxidized (GSSG) glutathione amounts, the activity of glutathione-dependent enzymes: glutathione peroxidase (GP) and glutathione reductase (GR) as well as NADH+-isocitrate-dehydrogenase activity (NADPH+- ICDH) were measured. The activity and protein expression of MnSOD and GP in rat brain mitochondria were estimated. Treatment of rats with mexidol led to a weakening of oxidative processes in brain mitochondria in comparison with rats exposed to rotenone intoxication. It was shown that intraperitoneal injections of mexidol led to a decrease in the TBA-AP and in the GSSG content and to an increase in GSH/GSSG ratio in comparison with rotenone intoxication. It was also registered an increase in the activity of NADH-dehydrogenase. Such changes indicated a weakening of the mitochondrial oxidative processes intensity. Treatment of rats with mexidol promoted an increase in GSH content, GR and NADPH+-ICDH activities in brain mitochondria in comparison with rotenone administration. Treatment with mexidol resulted to an increased activity and protein expression of GP and MnSOD. We conclude that mexidol reduced the rotenone-induced damage of rat brain mitochondria increasing the action of glutathione-dependent and NADPH+-generating enzymes.

γ-Aminobutyric acid regulates mitochondrial energy metabolism and organic acids metabolism in apples during postharvest ripening

“Golden Delicious” apples were treated with 1.0 mmol L−1 γ-aminobutyric acid (GABA) to evaluate the changes of mitochondrial energy metabolism and organic acids metabolism during ripening. Results showed that GABA dipping enhanced malic, citric, succinic, and tartaric acids contents in apple fruit. GABA treatment enhanced phosphoenolpyruvate carboxylase (PEPC), NADP-dependent isocitrate dehydrogenase (NADP-IDH), cytoplasm aconitase (Cyt-ACO), citrate synthase (CS), and cytosolic NAD-dependent malate dehydrogenase (NAD-MDH) activities, but decreased cytosolic NAD phosphate-dependent malic enzyme (NADP-ME) activity. GABA also enhanced the expressions of MdPEPC, MdNADP-IDH, MdCyt-ACO, MdNAD-MDH and MdCS, and decreased MdNADP-ME expression in apples. Moreover, higher level of energy charge, adenosine triphosphate (ATP) content, H+-ATPase, cytochrome C oxidase (CCO), succinic dehydrogenase (SDH), and Ca2+-ATPase activities were recorded in GABA-treated fruit. Additionally, GABA up-regulated MdSDH, MdCCO, MdH+-ATPase, and MdCa2+-ATPase expressions of apples. In conclusion, GABA could regulate the key gene expression and enzyme activity in mitochondrial energy metabolism and organic acids metabolism during ripening to maintain freshness of apple fruit.

Physiological Biochemistry-Combined Transcriptomic Analysis Reveals Mechanism of Bacillus cereus G2 Improved Salt-Stress Tolerance of Glycyrrhiza uralensis Fisch. Seedlings by Balancing Carbohydrate Metabolism.

Salt stress severely threatens the growth and productivity of Glycyrrhiza uralensis. Previous results found that Bacillus cereus G2 enhanced several carbohydrate contents in G. uralensis under salt stress. Here, we analyzed the changes in parameters related to growth, photosynthesis, carbohydrate transformation, and the glycolysis Embden-Meyerhof-Parnas (EMP) pathway-tricarboxylic acid (TCA) cycle by G2 in G. uralensis under salt stress. Results showed that G2 helped G. uralensis-accumulating photosynthetic pigments during photosynthesis, which could further increase starch, sucrose, and fructose contents during carbohydrate transformation. Specifically, increased soluble starch synthase (SSS) activity caused to higher starch content, which could induce α-amylase (AM) and β-amylase (BM) activities; increased sucrose content due to the increase of sucrose synthase (SS) activity through upregulating the gene-encoding SS, which decreased cell osmotic potential, and consequently, induced invertase and gene-encoding α-glucosidase that decomposed sucrose to fructose, ultimately avoided further water loss; increased fructose content-required highly hexokinase (HK) activity to phosphorylate in G. uralensis, thereby providing sufficient substrate for EMP. However, G2 decreased phosphofructokinase (PFK) and pyruvate kinase (PK) activities during EMP. For inducing the TCA cycle to produce more energy, G2 increased PDH activity that enhanced CA content, which further increased isocitrate dehydrogenase (ICDH) activity and provided intermediate products for the G. uralensis TCA cycle under salt stress. In sum, G2 could improve photosynthetic efficiency and carbohydrate transformation to enhance carbohydrate products, thereby releasing more chemical energy stored in carbohydrates through the EMP pathway-TCA cycle, finally maintain normal life activities, and promote the growth of G. uralensis under salt stress.

ACTIVITY OF KIDNEY MITOCHONDRIAL NAD+-DEPENDENT DEHYDROGENASES IN RATS UNDER CONDITIONS OF DIFFERENT NUTRIENT SUPPLY

The aim of this work was to evaluate the activity NAD+-dependent dehydrogenases of Krebs cycle in kidney of rats under the conditions of different sucrose and protein content in a diet. The activity of isocitrate dehydrogenase was evaluated based on the amount of accumulated NADН during conversion of isocitrate to α-ketoglutarate. The activity of malate dehydrogenase was determined from NADH accumulation in reaction of malate oxidation, at λ = 340 nm. The activity of α-ketoglutarate dehydrogenase was measured by intensity of α-ketoglutarate oxidation, spectrophoto-metrically at λ = 417 nm. The animals were divided into the following experimental groups: I – control group (C); II – animals receiving low-protein ration (LP); III – animals receiving high-sucrose diet (HS); IV – animals receiving low-protein high-sucrose diet (LP/HS). It has been shown, that by rats group kept on a low-protein diet isocitrate dehy-drogenase activity was increased, without any significantly compared changes in α-ketoglutarate dehydrogenase and malate dehydrogenase activities. A similar tendence is typical for animals maintained on a low-protein/high-sucrose diet. At the same time isocitrate dehydrogenase, α-ketoglutarate dehydrogenase and malate dehydrogenase activities exceeded control values in group of animals feeded by high-sucrose diet the most. From results we got, it can be con-cluded, that activation of NAD+-dependent dehydrogenases of Krebs cycle in mitochondrial kidney fraction of rats received a high-sucrose diet can be considered as one of possible links in mechanism of kidney injury progression. Our finding allows to substantiate the approaches for kidney complications treatment biochemically under nutrient imbalance.

Antibacterial mechanism of apple phloretin on physiological and morphological properties of Listeria monocytogenes

Green bactericides are excellent strategies for reducing food spoilage. Phloretin was regarded as efficient, broad-spectrum and safe preservative, which showed enormous potential in food industry. Inhibitory mechanism of phloretin on Listeria monocytogenes was systematically elucidated through integrity of cell membrane, intracellular protein content, energy level, and nucleic acid morphological character. SEM and TEM results showed minimal injury of cell membrane, which was further proved by a leakage of potassium ions, ATP and little protein and nucleic acid. There were drastic reduction of intracellular or total protein and ATP compared to cell without phloretin treatment. However, the specific activity of hexokinase and isocitrate dehydrogenase were unaffected after phloretin treatment. From these results, we concluded that phloretin’s bacteriostatic mechanism is decreasing the intracellular protein content and energy level resulting from DNA aggregation. This finding was prospective to fully illustrate the phloretin’s mechanism and develop it into a natural preservative in food industry.

Relationship between L-lactate dehydrogenase and multidrug resistance in Staphylococcus xylosus.

Staphylococcus xylosus is a gram-positive bacterium that has attracted much attention due to its increasing clinical appearance, frequently associated with serious multidrug resistance cases. L-lactate dehydrogenase (LDH) has been related to drug resistance in several bacterial species. However, the mechanism of multidrug resistance in S. xylosus remains unclear as well as the involvement of LDH in such resistance. To explore the relationship between multidrug resistance and LDH in S. xylosus, we used tylosin-resistant S. xylosus as the parent strain to construct ldh knockout and complemented strains. Then, we tested their resistance to macrolides, lincosamides, tetracyclines, and aminoglycosides. In addition, the enzyme activity, metabolite content, and transcriptional level of key genes involved in the TCA cycle and thioredoxin system were determined to clarify the mechanism of resistance. We observed that the resistance to multiple antibiotics increased significantly after ldh knockout, especially that to lincomycin, whereas antibiotic sensitivity was partially restored in the complemented strain. The levels of pyruvate, nicotinamide adenine dinucleotide, and reactive oxygen species decreased significantly upon ldh knockout, and the activity of isocitrate dehydrogenase and malate dehydrogenase decreased. These results indicate that the lack of LDH promotes multidrug resistance in S. xylosus by inhibiting the TCA cycle and regulating the thioredoxin system.

Mitochondrial superoxide targets energy metabolism to modulate epigenetic regulation of NRF2-mediated transcription

Mitochondria are central to the metabolic circuitry that generates superoxide radicals/anions (O2•-) as a by-product of oxygen metabolism. By regulating superoxide levels, manganese superoxide dismutase plays important roles in numerous biochemical and molecular events essential for the survival of aerobic life. In this study, we used MitoParaquat (mPQ) to generate mitochondria-specific O2•- and stable isotope-resolved metabolomics tracing in primary human epidermal keratinocytes to investigate how O2•- generated in mitochondria regulates gene expression. The results reveal that isocitrate is blocked from conversion to α-ketoglutarate and that acetyl-coenzyme A (CoA) accumulates, which is consistent with a reduction in oxygen consumption rate and inactivation of isocitrate dehydrogenase (IDH) activity. Since acetyl-CoA is linked to histone acetylation and gene regulation, we determined the effect of mPQ on histone acetylation. The results demonstrate an increase in histone H3 acetylation at lysines 9 and 14. Suppression of IDH increased histone acetylation, providing a direct link between metabolism and epigenetic alterations. The activity of histone acetyltransferase p300 increased after mPQ treatment, which is consistent with histone acetylation. Importantly, mPQ selectively increased the nuclear levels and activity of the oxidative stress-sensitive nuclear factor erythroid 2-related factor 2. Together, the results establish a new paradigm that recognizes O2•- as an initiator of metabolic reprogramming that activates epigenetic regulation of gene transcription in response to mitochondrial dysfunction.

DA-6 improves sunflower seed vigor under Al3+ stress by regulating Al3+ balance and ethylene metabolic

Aluminum (Al3+) stress restricts plant seed germination and seedling growth seriously. Here, the sunflower “S175″ variety was used to explore the technique of improving seed vigor under Al3+ stress and investigate the effect of diethyl aminoethyl hexanoate (DA-6) on physiological characteristics in sunflower seeds during germination under Al3+ stress. The results showed that 3.0 mmol·L−1 Al3+ treatment significantly suppressed the sunflower seed germination and seedling growth. Al3+ stress significantly increased Al3+ content and secretion rates of citric and malic acids in sunflower seeds during germination. Besides, endogenous ethylene content was increased in Al3+-treated seeds. DA-6 serves as a positive signal to regulate the sunflower seed germination under Al3+ stress. Moreover, DA-6 enhanced the activities of malic dehydrogenase, citrate synthase, and isocitrate dehydrogenase, up-regulated the expressions of organic acid transport-related genes (ALMT and MATE), resulting in reduced accumulation of Al3+. Furthermore, exogenous DA-6 mitigated excessive accumulation of ethylene by decreasing the 1-aminocyclopropane-1-dihydrodipicolinate synthase activity and related-gene expression. However, DA-6 treatment had no effect on abscisic acid or gibberellin metabolism in sunflower seeds under Al3+ stress. These results confirmed that DA-6 application enhanced the germination capacity through induction of the synthesis and transport of malic and citric acids, and suppression of the excessive accumulation of endogenous ethylene, thus contributing to alleviate Al3+ toxicity in sunflower seeds.