Succinate Dehydrogenase Activity Research Articles

A comprehensive analysis of the defense responses of Odontotermes formosanus (Shiraki) provides insights into the changes during Serratia marcescens infection

BackgroundOdontotermes formosanus (Shiraki) is a highly damaging agroforestry pest. Serratia marcescens is a broad-spectrum insecticidal pathogen and is highly lethal to O. formosanus. However, little is known about the mechanism between them. To improve the biological control of pests, a more in-depth analysis of the interactions between the pests and the pathogens is essential.ResultsWe used RNA-seq, enzyme activity assays and real-time fluorescent quantitative PCR (qPCR) to explore the defense responses of O. formosanus against SM1. RNA-seq results showed that 1,160, 2,531 and 4,536 genes were differentially expressed at 3, 6 and 12 h after SM1 infection, and Kyoto Encyclopedia of Genes and Genomes (KEGG) results indicated that immune response and energy metabolism were involved in the defense of O. formosanus against SM1. Reactive oxygen species (ROS) levels and ROS synthesis genes were significantly elevated, and the antioxidant system were induced in O. formosanus after SM1 infection. In addition, the cellular immune genes were affected, and the Toll, immune deficiency (Imd), Janus kinase/signal transducer and activator of transcription (JAK/STAT), c-Jun N-terminal Kinase (JNK) and melanization pathways were activated. In vitro, Oftermicin, an antimicrobial peptide, had a significantly inhibitory effect on SM1. Furthermore, the expression levels and enzyme activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH) and isocitrate dehydrogenase (IDH) in glycolysis and tricarboxylic acid (TCA) cycles were increased.ConclusionsOur results clearly demonstrated that O. formosanus defended against SM1 by activating the antioxidant system, innate immunity and energy metabolism. This study would provide useful information for the development of biological controls of O. formosanus.

The respiratory chain of Klebsiella aerogenes in urine-like conditions: critical roles of NDH-2 and bd-terminal oxidases

Klebsiella aerogenes is an opportunistic nosocomial bacterial pathogen that commonly causes urinary tract infections. Over the past decades, K. aerogenes strains have acquired resistance to common antibiotics that has led to the rise of multidrug-resistant and even pandrug-resistant strains. Infections produced by these strains are nearly impossible to treat, which makes K. aerogenes a global priority to develop new antibiotics and there is an urgent need to identify targets to treat infections against this pathogen. However, very little is known about the metabolism and metabolic adaptations of this bacterium in infection sites. In this work, we investigated the respiratory metabolism of K. aerogenes in conditions that resemble human urine, allowing us to identify novel targets for antibiotic development. Here we describe that, unlike other gram-negative pathogens, K. aerogenes utilizes the type-2 NADH dehydrogenase (NDH-2) as the main entry point for electrons in the respiratory chain in all growth conditions evaluated. Additionally, in urine-like media, the aerobic metabolism as a whole is upregulated, with significant increases in succinate and lactate dehydrogenase activity. Moreover, our data show that the bd-I type oxidoreductases are the main terminal oxidases of this microorganism. Our findings support an initial identification of NDH-2 and bd-I oxidase as attractive targets for the development of new drugs against K. aerogenes as they are not found in human hosts.

Modifications of the respiratory chain of Bacillus licheniformis as an alkalophilic and cyanide-degrading microorganism.

Bacillus licheniformis can use cyanide as a nitrogen source for its growth. However, it can also carry out aerobic respiration in the presence of this compound, a classic inhibitor of mammalian cytochrome c oxidase, indicating that B. licheniformis has a branched respiratory chain with various terminal oxidases. Here, we studied the modifications in the respiratory chain of B. licheniformis when cells were cultured in Nutrient Broth, an alkaline medium with ammonium, or an alkaline medium with cyanide. Then, we measured oxygen consumption in intact cells and membranes, enzyme activities, carried out 1D and 2D-BN-PAGE, followed by mass spectrometry analysis of BN-PAGE bands associated with NADH, NADPH, and succinate dehydrogenase activities. We found that cell growth was favored in a nutrient medium than in an alkaline medium with cyanide. In parallel, respiratory activity progressively decreased in cells cultured in the rich medium, alkaline medium with ammonium, and the lowest activity was in the cells growing in the alkaline medium with cyanide. B. licheniformis membranes contain NADH, NADPH, and succinate dehydrogenases, and the proteomic analysis detected the nitrate reductase and the bc, caa3, aa3, and bd complexes. The succinate dehydrogenase migrated with a molecular mass of 375kDa, indicating its association with the nitrate reductase (115kDa + 241kDa, respectively). The NADH dehydrogenase of B. licheniformis forms aggregates of different molecular mass.

Sodium danshensu modulates skeletal muscle fiber type formation and metabolism by inhibiting pyruvate kinase M1.

Sodium Danshensu (SDSS) is extracted from Salvia miltiorrhiza and has many pharmacological effects. However, little is known about its effects on muscle fiber formation and metabolism. Here, we aimed to investigated the role and molecular mechanisms of SDSS in modulating the formation of skeletal muscle fiber. C2C12 cells were incubated in differentiation medium with or without SDSS for 4days. C57BL/6 mice were orally administered SDSS by gavage once a day for 8weeks. Grip strength, treadmill, muscle weight, western blotting, qPCR, immunofluorescence staining and H&E staining were performed. SDSS target proteins were searched through drug affinity responsive target stability (DARTS) and mass spectrometry analysis. Furthermore, molecular docking was carried out for Pyruvate kinase M1 (PKM1). The effect of PKM1 on myosin heavy chain (MyHCs) gene expression was verified by knockdown of PKM1 experiment. SDSS induced oxidative muscle fiber-related gene expression, and inhibited glycolytic fiber-related gene expression in C2C12 cells. Muscle mass, the percentage of slow oxidative fibers, succinic dehydrogenase activity, muscle endurance, glucose tolerance, and the expression of the MyHC1 and MyHC2a genes increased while MyHC2b expression, lactate dehydrogenase activity, and the percentage of glycolytic muscle fibers decreased in SDSS-treated mice. Mechanistically, SDSS bound to the pyruvate kinase PKM1 and significantly repressed its activity. PKM1 inhibited MyHC1 and MyHC2a expression but promoted MyHC2b expression. SDSS also significantly attenuated the effects of PKM1 on muscle fiber-related gene expression in C2C12 cells. Our findings indicate that SDSS promotes muscle fiber transformation from the glycolytic type to the oxidative type by inhibiting PKM1 activity, which provide a new idea for treating muscle atrophy, muscle metabolism diseases and improving animal meat production.

Nitric Oxide-Dependent Regulation of Oxygen-Related Processes in a Rat Model of Lead Neurotoxicity: Influence of the Hypoxia Resistance Factor

Background/Aims: Lead exposure is known to induce oxidative stress and neurotoxicity. Nitric oxide (NO) plays an important role in modulating oxidative stress, with L-arginine as a precursor of NO and Nω-nitro-L-arginine (L-NNA) as an inhibitor of NO synthase, an enzyme that catalyses the production of nitric oxide (NO) from L-arginine. Methods: This study investigated the differential effects of L-arginine and L-NNA on markers of oxidative stress and biochemical changes in brain tissue from rats with different levels of resistance to hypoxia exposed to lead nitrate. Rats with either low or high resistance to hypoxia were exposed to lead nitrate (oral 3.6 mg lead nitrate/kg b.w. per day for 30 days) and treated with L-arginine (600 mg/kg b.w., i.p., 30 min before and after exposure to lead nitrate) or L-NNA (35 mg/kg b.w., i.p., 30 min before and after exposure to lead nitrate). Brain tissue samples were analysed for lipid peroxidation, oxidative modification of proteins, and activity of antioxidant enzymes, including superoxide dismutase, catalase, glutathione reductase, and peroxidase, and total antioxidant status (TAS). We also examined the biomarkers of biochemical pathways involving the activity of alanine and aspartate aminotransferases, succinate dehydrogenase (SDH), and α-ketoglutarate dehydrogenase (KGDH). In addition, the trend observed was supported by assessments of the acetylcholine levels and acetylcholinesterase activity (ACh-AChE system) in brain tissue. Results: In rats with low resistance to hypoxia, the L-arginine treatment significantly reduced lipid peroxidation and oxidative protein modification but increased antioxidant enzyme activity, suggesting a protective effect against lead-induced oxidative stress. Conversely, in rats with high resistance to hypoxia, L-NNA had a protective effect, reducing lead-induced oxidative damage and decreasing lipid peroxidation, whereas L-arginine exacerbated oxidative stress and impaired antioxidant defences. These findings were supported by corresponding changes in the acetylcholine-acetylcholinesterase system, reflecting the observed patterns of lead-induced oxidative stress and neurotoxicity. The study shows that L-arginine exerts a protective effect by reducing lead-induced oxidative damage via an improvement in TAS. Our study shows that lead nitrate exposure significantly increases ala-nine and aspartate aminotransferase activity in brain tissue, with L-arginine exacerbating and L-NNA reversing this effect. The lead nitrate exposure also affected the activities of SDH and KGDH, which are important for cellular energy production and hypoxia resistance, with L-arginine altering SDH activity depending on the level of resistance and L-NNA enhancing both SDH and KGDH activities. These trends were further validated by alterations in the ACh-AChE system, highlighting the differential role of NO-dependent mechanisms in modulating lead-induced neurotoxicity based on hypoxia resistance. Conclusion: These findings suggest potential targeted therapeutic strategies based on the oxidative stress profile and highlight the potential of nitric oxide system modulators in counteracting lead-induced biochemical alterations and the dynamics of the ACh-AChE system depending on the individual physiological reactivity of organisms.

Novel Flavonol Derivatives Containing Quinoxaline: Insights into the Antifungal Mechanism against Sclerotinia sclerotiorum.

In this study, 12 pairs of tautomeric flavonol derivatives containing quinoxaline were synthesized. The results of antifungal activity showed that in the enol-keto tautomerism, the target compounds containing keto (YB series) had better inhibitory activity against Sclerotinia sclerotiorum (S.s.) than compounds containing enol (YA series). YB9 showed the strongest antifungal activity against S.s., and the median effective concentration (EC50) value was 1.0 μg/mL, which was better than azoxystrobin (Az, 35.3 μg/mL). In vivo fungal inhibition experiments showed that the protective activity of YB9 against rape leaves was 83.4% at 200 μg/mL, which was superior to that of Az (70.2%). The activity of succinate dehydrogenase and molecular docking results showed that YB9 had a stronger antifungal effect than YA9. The results of oxalic acid content determination showed that YB9 could reduce the pathogenic ability of S.s. Then, the inhibitory effect of YB9 against S.s. was further verified by scanning electron microscopy, fluorescence microscopy, cell membrane permeability, cell content leakage, and malondialdehyde content.

Design, Synthesis, and Biological Activity Evaluation of Eco-Friendly Rosin-Diamide-Based Fungicides as Potential Succinate Dehydrogenase Inhibitors for Sustainable Crop Protection.

To develop novel succinate dehydrogenase (SDH) inhibitors for sustainable crop protection, a series of dehydroabietyl-diamide-based fungicides (a total of 21) were designed. In vitro fungicidal activity measurement showed that compound 3u exhibited excellent fungicidal activity against Valsa mali (half-maximal effective concentration, EC50 = 0.195 μg/mL), surpassing that of the positive control carbendazim (EC50 = 1.35 μg/mL). The in vivo fungicidal activity assessment suggested that 3u exhibited a protective effect on apple branches (69.7-48.1%) and apples (94.6-56.6%). Furthermore, biosafety evaluation indicated that 3u was significantly environmentally friendly toward zebrafish. Subsequently, morphology, physiology, and molecular docking were investigated to elucidate the mode of action of 3u against V. mali. Results demonstrated a strong binding between 3u and SDH, resulting in decreased SDH activity (half-maximal inhibitory concentration, IC50 = 11.7 μg/mL). Moreover, 3u disrupted the mycelial cell membrane and accelerated electrolyte leakage, ultimately resulting in the death of V. mali. These findings suggest that 3u could serve as a potent SDH inhibitor for sustainable crop protection.

Combined effects of thermal environment and gene regulation on metabolic enzyme activities of major metabolic tissues in a winter-breeding amphibian

Variations in thermal environments can provoke diverse physiological responses in amphibians. Despite extensive studies on the thermal sensitivity of amphibian metabolic physiology, including enzyme activity at different temperatures, the rationale for selecting specific metabolic enzymes and their relationship with gene expression remains unclear. Cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH) are key metabolic enzymes within the primary metabolic regulatory tissues of animals. Through a comparative analysis of the effects of two different thermal conditions (12 and 18 °C) on the activities and mRNA expression levels of these enzymes within the kidney and liver tissues of a winter-breeding amphibian (Leptobrachium liui), with the field group during the breeding season as the control, we provide insights into the interplay between temperature and gene expression. The mRNA levels of CCO subunits 1 (cox1), 2 (cox2), and 3 (cox3), and LDH subunit A (ldha) were significantly higher in the kidney than in the liver of all individuals. High-temperature acclimation resulted in significantly decreased expression levels of cox1-3, ldha, and SDH complex flavoprotein subunit A (sdha) in the kidney. In the liver, the expression levels of sdha and ldha significantly reduced under high-temperature treatment, whereas cox3 expression increased. SDH and LDH activities displayed tissue-specific variations, while no significant differences in CCO activity were observed between tissues. CCO, SDH, and LDH activities in both liver and kidney tissues significantly declined after high-temperature acclimation, but simultaneously increased with up-regulated gene expression, indicating that the thermal environment and corresponding gene expression combined affect the activities of these metabolic enzymes. In conclusion, the thermal environment is a key factor affecting the physiological and biochemical responses of L. liui. Prolonged exposure to high temperatures during the breeding season could inhibit the activity of primary metabolic enzymes in the winter-breeding amphibian.

Coral-like AgNPs hybrided MOFs modulated with biopolymer polydopamine for synergistic antibacterial and biofilm eradication

Bacterial contamination is an intractable challenge in food safety, environments and biomedicine fields, and places a heavy burden on society. Polydopamine (PDA), a high molecular biopolymer, is considered as a promising candidate to participate in the design of novel antibacterial agents with unique contributions in biocompatibility, adherence, photothermal and metal coordination ability. In this study, coral-like ZIFL-PDA@AgNPs with excellent antibacterial properties and biocompatibility were prepared by embedding AgNPs into the biopolymer PDA-modulated ZIFL-PDA nanostructures by green reduction method to solve the problem with poor stability of AgNPs. Based on the plasma resonance effect of AgNPs, coral-like ZIFL-PDA@AgNPs had enhanced photothermal properties compared with ZIFL-PDA. Due to the synergistic effect between antibacterial metal ions mainly Ag+ and the photothermal effect, coral-like ZIFL-PDA@AgNPs showed enhanced anti-mature biofilm and antibacterial properties, which was dependent on its concentration and sterilization time. In addition, regulated by the ZIFL-PDA nanostructure, coral-like ZIFL-PDA@AgNPs demonstrated a unique Ag+ long-time sustained release behavior, giving it an extended antibacterial validity period and good biocompatibility. Antibacterial mechanism experiments indicated that coral-like ZIFL-PDA@AgNPs can significantly damage the integrity of bacterial cell membrane, reduce the content of ATP in bacterial by affecting the activity of succinate dehydrogenase, and induce the accumulation of reactive oxygen species, ultimately leading to bacterial death.

Comparative Analysis of Oxidative Metabolism in Liver in Different Experimental Models of Hypothyroidism: Low Iodine Diet and Anti-Thyroid drug (Methimazole)

Objectives: On the concept of oxidative stress in hypothyroidism, which still remains ambiguous and controversial, the article emphasizes the issue of the impact of the experimental conditions on the validity of the data obtained in different methods of modeling thyroid dysfunction. Materials and Methods: Experiments were conducted on 112 white nonlinear male rats. Thyroid hormones and biomarkers of oxidative metabolism in the liver tissue were determined in rats kept for 3 months on a low-iodine diet (LID) and in rats with methimazole (MMI)-induced hypothyroidism (2,5 mg/100 g of body weight for 3 weeks). Results: In LID-rats (n=96) total serum T4 amounted 43, total T3 in liver tissue - 73% of the level found in euthyroid animal, p=0.0121 and p=0.0051, respectively), whereas in MMI-rats (n=96) both total and free serum T4 were 67% of control (p=0.0002 for both total and free T4). In LID-rats cytochrome oxidase (CcOX) activity in liver tissue was 68.5, concentration of malondialdehyde (MDA) - 58% of euthyroids (p value - 0.0202 and 0.0127, respectively), while protein carbonyls (PC) level was 116% of the control (p=0.0411). In MMI-rats liver malate dehydrogenase (MDH) activity decreased up to 70.9, but succinate dehydrogenase (SDH) activity and MDA concentration increased up to 163.6 and 154% of the level in euthyroid animals respectively (p˂0.05). Conclusion: LID-model led to the more pronounced inhibition of thyroid function, than that the MMI-hypothyroidism model used. LID-model was accompanied by a decrease in the intensity of oxidative metabolism in liver tissue, whereas MMI-hypothyroidism - by activation of the succinate oxidation pathway and an increase in the concentration of secondary lipid peroxidation products in the liver of experimental animals. The results suggest that the conflicting data obtained from studies of oxidative metabolism in hypothyroidism, among other assumptions, may be due to the different approaches used by researchers to model thyroid dysfunction.

Study on sperm cryopreservation of hybrid fish derived from Carassius cuvieri (♀) × Carassius auratus red var (♂)

Cryopreservation of sperm is an effective method for conserving germplasm resources in fish genetic breeding. The high-quality hybrid fish (WR) derived from white crucian carp (Carassius cuvieri, WCC, ♀) and red crucian carp (C. auratus red var., RCC, ♂), possesses valuable traits such as high survival rates, strong resistance, and rapid growth, representing an important germplasm resources of crucian carp. This study compared the effects of different antifreeze solutions on sperm viability among three varieties (WR, WCC, and RCC) and examined changes in enzyme activity, fertilization rates, and hatching rates after cryopreservation, aiming to enhance the cryogenic sperm cryopreservation technique in hybrid fish and investigate the mechanisms underlying spermatozoa damage caused by cryopreservation. The results showed that the antifreeze combination of D14 with 15 % dimethyl sulfoxide (DMSO) had the best effect in preserving the sperm of WR and WCC, while D20 with 10 % DMSO was the optimal combination for RCC sperm. After ultra-low temperature preservation, the longevity, fertilization, and hatching rates of frozen sperm were significantly lower (P < 0.05) compared to fresh sperm. The enzyme activities of superoxide dismutase (SOD), lactate dehydrogenase (LDH), and creatine kinase (CK) were significantly decreased (P < 0.05) in spermatozoa, whereas they showed a significant increase (P < 0.05) in sperm plasma. Succinate dehydrogenase (SDH) activity was significantly reduced (P < 0.05) in frozen spermatozoa of RCC compared to fresh spermatozoa, and exhibited lower activity in frozen spermatozoa of WCC and WR. Additionally, SDH activity was significantly elevated (P < 0.05) in frozen sperm plasma, and glutathione reductase (GR) activity was significantly lower (P < 0.05) in both frozen sperm plasma and spermatozoa across all three species. The study demonstrated that cryopreservation had a significant effect on the enzyme activities of spermatozoa and sperm plasma in all three species. These findings provide important technical support for the conservation of high-quality fish germplasm resources, particularly for novel varieties resulting from distant hybridization in fish.

Myeloid beta-arrestin 2 depletion attenuates metabolic dysfunction-associated steatohepatitis via the metabolic reprogramming of macrophages

Macrophage-mediated inflammation has been implicated in the pathogenesis of metabolic dysfunction-associated steatohepatitis (MASH); however, the immunometabolic program underlying the regulation of macrophage activation remains unclear. Beta-arrestin 2, a multifunctional adaptor protein, is highly expressed in bone marrow tissues and macrophages and is involved in metabolism disorders. Here, we observed that β-arrestin 2 expression was significantly increased in the liver macrophages and circulating monocytes of patients with MASH compared with healthy controls and positively correlated with the severity of metabolic dysfunction-associated steatotic liver disease (MASLD). Global or myeloid Arrb2 deficiency prevented the development of MASH in mice. Further study showed that β-arrestin 2 acted as an adaptor protein and promoted ubiquitination of immune responsive gene 1 (IRG1) to prevent increased itaconate production in macrophages, which resulted in enhanced succinate dehydrogenase activity, thereby promoting the release of mitochondrial reactive oxygen species and M1 polarization. Myeloid β-arrestin 2 depletion may be a potential approach for MASH.

Dysfunctional cardiac energy transduction, mitochondrial oxidative stress, oncogenic and apoptotic signaling in DiNP-induced asthma in murine model.

Diisononyl phthalate (DiNP) has been associated with the development of allergies, asthma, and allergic airway inflammation. Through a complex interplay of signals and feedback mechanisms, the lungs communicate with the heart to ensure maintenance of homeostasis and supporting the body's metabolic demands. In the current study, we assessed the crosstalk between DiNP-induced asthma and cardiac cellular respiration, oxidative stress, apoptotic potential, and induction of oncogenic factors. Ten male BALB/c mice with a weight range of 20-30g were divided into two groups, each comprising five mice. Group 1 (control), was administered saline orally for a duration of 30days. In contrast, group 2 (DiNP group), received 50mg/kg of DiNP to induce asthma. After the final administration and asthma induction, the mice were euthanized, and their hearts were excised, processed, and subjected to biochemical analyses. The DiNP group had downregulated (P < 0.05) activities of the enzymes of glycolysis, tricyclic acid cycle, and electron transport chain except the hexokinase and succinate dehydrogenase activity which were upregulate relative to control. Also, oxidative distress markers (GSH, CAT, and MDA and SOD) were also perturbed. Biomarkers of inflammation (MPO and NO) were considerably higher (P < 0.05) in the heart of DiNP-induced asthma mice as compared with the control group. Furthermore, DiNP-induced asthma group has an increased cardiac caspase-3, Bax, c-Myc and K-ras, and p53 while the Bcl2 decreased when compared with control. Overall, the findings indicate that DiNP-induced asthma impairs cardiac functions by induction of key cardiac oncogenes, downregulation of cardiac energy, transduction of enzymes, and promotion of oxidative stress and cellular death.

Identification of Chemical Scaffolds That Inhibit the Mycobacterium tuberculosis Respiratory Complex Succinate Dehydrogenase.

Drug-resistant Mycobacterium tuberculosis is a significant cause of infectious disease morbidity and mortality for which new antimicrobials are urgently needed. Inhibitors of mycobacterial respiratory energy metabolism have emerged as promising next-generation antimicrobials, but a number of targets remain unexplored. Succinate dehydrogenase (SDH), a focal point in mycobacterial central carbon metabolism and respiratory energy production, is required for growth and survival in M. tuberculosis under a number of conditions, highlighting the potential of inhibitors targeting mycobacterial SDH enzymes. To advance SDH as a novel drug target in M. tuberculosis, we utilized a combination of biochemical screening and in-silico deep learning technologies to identify multiple chemical scaffolds capable of inhibiting mycobacterial SDH activity. Antimicrobial susceptibility assays show that lead inhibitors are bacteriostatic agents with activity against wild-type and drug-resistant strains of M. tuberculosis. Mode of action studies on lead compounds demonstrate that the specific inhibition of SDH activity dysregulates mycobacterial metabolism and respiration and results in the secretion of intracellular succinate. Interaction assays demonstrate that the chemical inhibition of SDH activity potentiates the activity of other bioenergetic inhibitors and prevents the emergence of resistance to a variety of drugs. Overall, this study shows that SDH inhibitors are promising next-generation antimicrobials against M. tuberculosis.

A field study to optimize protein and lipid levels in diet for cage-cultured subadult rockfish Sebastes schlegelii

A feeding trial was conducted to evaluate growth, body composition, serum biochemistry, digestion and metabolism, and oxidation resistence of S. schlegelii fed 9 diets in a 3×3 factorial design (protein levels: 44 %, 48 %, 52 %; lipid levels: 6 %, 10 %, 14 %), to optimize protein and lipid levels for practical feed formula. Rockfish (114.25 g) were stocked into 27 cages in an offshore system and fed test diets to satiation twice daily for 8 weeks. Growth increased but feed conversion rate decreased with dietary protein increasing. Increasing dietary protein to >48 % led to reduced feeding intake but increased protein efficiency ratio. Lipid efficiency ratio increased with dietary protein increasing but decreased with dietary lipid increasing. Hepatosomatic index decreased coupling with the increases in condition factor and liver lipid content as dietary lipid increased to 14 %. Intraperitoneal fat ratio increased with dietary lipid increasing. Increasing dietary protein to > 48 % significantly elevated serum total protein and glucose concentrations, hepatic glycogen synthase activity. High-protein (52 %) diets elevated serum albumin and urea nitrogen concentrations, hepatic pyruvate kinase and alanine aminotransferase (ALT) activities but downregulated hepatic growth-hormone (GH) receptor. Activities of trypsin, lipase, serum superoxide dismutase and total antioxidant capacity decreased with the dietary lipid increasing. Increasing dietary lipid to > 10 % reduced serum GH concentration, and high-lipid (14 %) diets significantly enhanced serum triglyceride concentration and hepatic transaminases activities, and resulted in a visual increase of adipocytes in liver. Serum cholesterol and low-density lipoprotein decreased as dietary protein increased to 48–52 % or dietary lipid >10 %. Hepatic succinate dehydrogenase activity and serum IGF-1 significantly increased while hepatic fatty acid synthetase decreased as dietary protein increased to >48 % or dietary lipid >10 %. High-protein (52 %) diet or high-lipid (14 %) diet elevated serum malonaldehyde concentration. These findings suggested 48 % protein and 10 % lipid were the optimal in diet for subadult S. schlegelii.

Plasma Biochemistry, Intestinal Health, and Transcriptome Analysis Reveal Why Laying Hens Produce Translucent Eggs.

Producing translucent eggs has been found to reduce the quality and safety of the eggs, as well as the demand from consumers. However, the intestinal function and the molecular mechanism for the production of translucent eggs remain uncertain. A total of 120 eggs from 276-day-old Jining Bairi were divided into two groups based on eggshell translucence: the translucent egg group (group T) and the normal group (group C). Group T exhibited thicker eggshells and a lower egg yolk color. Subsequently, we divided the chickens into translucent and normal groups based on their egg quality. We then assessed the plasma biochemical index, intestinal morphology and structure, enzyme activity, and antioxidant capacity of the hens producing translucent eggs compared to those producing normal eggs. The results showed that the ratio of duodenal villus length to crypt depth, succinate dehydrogenase (SDH) activity, chymotrypsin, total ATPase (T-ATPase), alkaline phosphatase (AKP), and glutathione peroxidase (GSH-Px) activities were decreased in the hens produced translucent eggs (p < 0.05), but malondialdehyde (MDA) content was increased (p < 0.05); jejunal lipase activity, Na+K+-ATPase activity, total antioxidant capacity (T-AOC), and GSH-Px activities were decreased (p < 0.05) in group T; ileal amylase and Ca2+Mg2+-ATPase activities were also decreased (p < 0.05) in group T. In addition, we identified a total of 471 differentially expressed genes (DEGs) in duodenal tissue, with 327 up-regulated genes and 144 down-regulated genes (|log2FC| ≥ 1 and p < 0.05). Enrichment analysis showed that the up-regulated genes, such as GSTT1, GSTO2, and GSTA3, were mostly enriched in metabolism of xenobiotics by cytochrome P450, drug metabolism-cytochrome P450, and oxidative phosphorylation pathways. The results of our study indicate that plasma lipid metabolism disorder, decreased intestinal antioxidant capacity, and altered intestinal metabolism capabilities may influence the formation of translucent eggs.

SDHAF2 facilitates mitochondrial respiration through stabilizing succinate dehydrogenase and cytochrome c oxidase assemblies

Succinate dehydrogenase (SDH) plays pivotal roles in maintaining cellular metabolism, modulating regulatory control over both the tricarboxylic acid cycle and oxidative phosphorylation to facilitate energy production within mitochondria. Given that SDH malfunction may serve as a hallmark triggering pseudo-hypoxia signaling and promoting tumorigenesis, elucidating the impact of SDH assembly defects on mitochondrial functions and cellular responses is of paramount importance. In this study, we aim to clarify the role of SDHAF2, one assembly factor of SDH, in mitochondrial respiratory activities. To achieve this, we utilize the CRISPR/Cas9 system to generate SDHAF2 knockout in HeLa cells and examine mitochondrial respiratory functions. Our findings demonstrate a substantial reduction in oxygen consumption rate in SDHAF2 knockout cells, akin to cells with inhibited SDH activity. In addition, in our in-gel activity assays reveal a significant decrease not only in SDH activity but also in cytochrome c oxidase (COX) activity in SDHAF2 knockout cells. The reduced COX activity is attributed to the assembly defect and remains independent of SDH inactivation or SDH complex disassembly. Together, our results indicate a critical role of SDHAF2 in regulating respiration by facilitating the assembly of COX.

Repeated marine heatwaves aggravate the adverse effects of nano-TiO2 on physiological metabolism of the thick-shelled mussel Mytilus coruscus

Global climate change is a major trigger of unexpected temperature fluctuations. The impacts of marine heatwaves (MHWs) and nano-titanium dioxide (nano-TiO2) on marine organisms have been extensively investigated. However, the potential mechanisms underlying their interactive effects on physiological processes and metabolism remain poorly understood, especially regarding periodic MHWs in real-world conditions. In this study, the effects of nano-TiO2 (at concentrations of 0, 25, and 250 μg/L) and periodic MHWs on the condition index (CI) and underlying metabolic mechanisms were investigated in mussels (Mytilus coruscus). The results showed that mussels try to upregulate their respiration rate (RR) to enhance aerobic metabolism (indicated by elevated succinate dehydrogenase) under short-term nano-TiO2 exposure. However, even at ambient concentration (25 μg/L), prolonged nano-TiO2 exposure inhibited ingestion ability (decreased clearance rate) and glycolysis (inhibited pyruvate kinase, hexokinase, and phosphofructokinase activities), which led to an insufficient energy supply (decreased triglyceride, albumin, and ATP contents). Repeated thermal scenarios caused more severe physiological damage, demonstrating that mussels are fragile to periodic MHWs. MHWs decreased the zeta potential of the nano-TiO2 particles but increased the hydrodynamic diameter. Additionally, exposure to nano-TiO2 and periodic MHWs further affected aerobic respiration (inhibited lactate dehydrogenase and succinate dehydrogenase activities), metabolism (decreased RR, activities of respiratory metabolism-related enzymes, and expressions of PEPCK, PPARγ, and ACO), and overall health condition (decreased ATP and CI). These findings indicate that the combined stress of these two stressors exerts more detrimental impact on the physiological performance and energy metabolism of mussels, and periodic MHWs exacerbate the toxicological effects of ambient concentration nano-TiO2. Given the potential worsening of nanoparticle pollution and the increase in extreme heat events in the future, the well-being of mussels in the marine environment may face further threats.

Human inborn errors of long-chain fatty acid oxidation show impaired inflammatory responses to TLR4-ligand LPS.

Stimulation of mammalian cells with inflammatory inducers such as lipopolysaccharide (LPS) leads to alterations in activity of central cellular metabolic pathways. Interestingly, these metabolic changes seem to be important for subsequent release of pro-inflammatory cytokines. This has become particularly clear for enzymes of tricarboxylic acid (TCA) cycle such as succinate dehydrogenase (SDH). LPS leads to inhibition of SDH activity and accumulation of succinate to enhance the LPS-induced formation of IL-1β. If enzymes involved in beta-oxidation of fatty acids are important for sufficient responses to LPS is currently not clear. Using cells from various patients with inborn long-chain fatty acid oxidation disorders (lcFAOD), we report that disease-causing deleterious variants of Electron Transfer Flavoprotein Dehydrogenase (ETFDH) and of Very Long Chain Acyl-CoA Dehydrogenase (ACADVL), both cause insufficient inflammatory responses to stimulation with LPS. The insufficiencies included reduced TLR4 expression levels, impaired TLR4 signaling, and reduced or absent induction of pro-inflammatory cytokines such as IL-6. The insufficient responses to LPS were reproduced in cells from healthy controls by targeted loss-of-function of either ETFDH or ACADVL, supporting that the deleterious ETFDH and ACADVL variants cause the attenuated responses to LPS. ETFDH and ACADVL encode two distinct enzymes both involved in fatty acid beta-oxidation, and patients with these deficiencies cannot sufficiently metabolize long-chain fatty acids. We report that genes important for beta-oxidation of long-chain fatty acids are also important for inflammatory responses to an acute immunogen trigger like LPS, which may have important implications for understanding infection and other metabolic stress induced disease pathology in lcFAODs.

Biochemical and Antioxidant Characteristics of Chlorococcum oleofaciens (Chlorophyceae, Chlorophyta) under Various Cultivation Conditions.

The functional state of enrichment cultures of the Chlorophycean strain Chlorococcum oleofaciens CAMU MZ-Ch4 under various cultivation conditions was studied. Experiments with different aeration conditions, cultivation durations, and nitrogen and phosphorus concentrations in the medium were carried out to evaluate the growth dynamics of the strain and its biochemical characteristics. The contents of chlorophylls, carotenoids, proteins, lipids, retinol, α-tocopherol, ascorbic acid, phenolic compounds, lipid peroxidation products, antioxidant enzymes (glutathione peroxidase, catalase, superoxide dismutase), and succinate dehydrogenase activity were measured. The lipid content on the fully supplemented Bold's basal medium increased to 381.03 mg g-1 dry weight at the late stationary growth phase. This value is 1.3-2.8 times higher than in other experiments. The use of aeration was associated with an increased content of proteins at 283.56 mg g-1 and of carotenoids at 2.12 mg g-1. Also, cultures at the early stationary growth phase with aeration showed the ability to accumulate phenolic compounds and ascorbic acid in amounts up to 0.32 mg g-1 and 0.19 mg g-1. The 74-day-old cultures had the highest contents of retinol (0.16 mg g-1) and α-tocopherol (0.68 mg g-1). Growth in nitrogen- and phosphorus-depleted media increased catalase and superoxide dismutase activity. A comprehensive analysis of all data showed that the antioxidant defence system is stress-resistant and flexible under varying aeration conditions and nitrogen and phosphorus availabilities. Thus, the strain CAMU MZ-Ch4 can be considered a potential producer of lipids, pigments, proteins, and vitamins under various culturing conditions.