Reduced Oxygen Consumption Research Articles

Beetroot Juice - Legal Doping for Athletes?

Nitric oxide (NO) is a physiologically important signaling molecule that promotes the expansion of blood vessels and thus facilitates the transport of oxygen (O2) and energy substrates to the muscles. Research shows that nitric oxide (NO) also improves the effectiveness of mitochondrial respiration, which is manifested by reduced oxygen consumption during exercise. Until recently, it was thought that nitric oxide (NO) could only be formed as a result of the endogenous pathway of oxidative transformations L-arginine. Recent research results indicate, however, that an alternative to the endogenous pathway of nitric oxide (NO) formation may be the exogenous supply of inorganic nitrates (NO3-) with food. The aim of the study was to review the current literature on the properties of beetroot juice as an important source of nitrates (NO3-) and its effectiveness in improving the exercise capacity of physically active people. A systematic review of the research, published from 2005 to January 31, 2021, was made on the basis of searching bibliographic databases such as: PubMed, Elsevier and Web of Science. The following keywords were used: “beetroot”, “beetroot juice”, “nitrates”, “nitrites”, “nitric oxide”, “supplementation”, “ergogenic substances”, “sports nutrition”. Although there are conflicting data, it appears that beetroot juice supply may be a cheap, natural, and promising nutritional strategy for improving sports performance in both endurance and intermittent high intensity (start-stop) exercise. More detailed studies are analyzing the effect of dietary nitrate (NO3-) supply in anaerobic exercise - especially in high-volume resistance training - are needed. It is also emphasized that further research is needed to elucidate the effects of specific factors on the variability of ergogenic effects after beetroot juice consumption, which may be of the greatest importance in terms of the effectiveness of this nutritional intervention.

Bioenergetic consequences of FoF1–ATP synthase/ATPase deficiency in two life cycle stages of Trypanosoma brucei

Mitochondrial ATP synthase is a reversible nanomotor synthesizing or hydrolyzing ATP depending on the potential across the membrane in which it is embedded. In the unicellular parasite Trypanosoma brucei, the direction of the complex depends on the life cycle stage of this digenetic parasite: in the midgut of the tsetse fly vector (procyclic form), the FoF1–ATP synthase generates ATP by oxidative phosphorylation, whereas in the mammalian bloodstream form, this complex hydrolyzes ATP and maintains mitochondrial membrane potential (ΔΨm). The trypanosome FoF1–ATP synthase contains numerous lineage-specific subunits whose roles remain unknown. Here, we seek to elucidate the function of the lineage-specific protein Tb1, the largest membrane-bound subunit. In procyclic form cells, Tb1 silencing resulted in a decrease of FoF1–ATP synthase monomers and dimers, rerouting of mitochondrial electron transfer to the alternative oxidase, reduced growth rate and cellular ATP levels, and elevated ΔΨm and total cellular reactive oxygen species levels. In bloodstream form parasites, RNAi silencing of Tb1 by ∼90% resulted in decreased FoF1–ATPase monomers and dimers, but it had no apparent effect on growth. The same findings were obtained by silencing of the oligomycin sensitivity-conferring protein, a conserved subunit in T. brucei FoF1–ATP synthase. However, as expected, nearly complete Tb1 or oligomycin sensitivity-conferring protein suppression was lethal because of the inability to sustain ΔΨm. The diminishment of FoF1–ATPase complexes was further accompanied by a decreased ADP/ATP ratio and reduced oxygen consumption via the alternative oxidase. Our data illuminate the often diametrically opposed bioenergetic consequences of FoF1–ATP synthase loss in insect versus mammalian forms of the parasite.

Single nucleotide polymorphism in avian uncoupling protein gene is associated with thermoregulation in chicks.

Avian uncoupling protein (av-UCP) is a key protein for thermoregulation in poultry. A single nucleotide polymorphism (SNP) in the av-UCP gene has been reported in chickens. The purpose of the current study was to clarify the association between this av-UCP gene mutation and thermoregulation in chickens. Wild and mutant type chicks for the av-UCP gene SNP (g. 1270 of the av-UCP gene exon 3 with C to T substitution and amino acid substitution) were exposed to high ambient temperature. Rectal temperature, radiation temperature on the body surface, and the expression of heat dissipation behavior (wing drooping and panting) during heat exposure were measured. In addition, oxygen consumption rate in the thermoneutral zone in wild and mutant type chicks was measured. Changes in wing temperature during heat exposure in wild-type chicks were lower than those in mutants. The latency of continuous wing drooping during heat exposure in wild-type chicks was shorter than in mutant chicks. It was also found that the SNP in the av-UCP gene caused reduced oxygen consumption. These results suggest that the av-UCP gene mutation affects thermoregulation, especially heat production, in chickens.

Biodegradable copper-metformin nanoscale coordination polymers for enhanced chemo/chemodynamic synergistic therapy by reducing oxygen consumption to promote H2O2 accumulation.

Chemo/chemodynamic synergistic therapy is a promising strategy to improve the antitumor effect. However, hypoxia and a limited amount of hydrogen peroxide (H2O2) in the tumor microenvironment (TME) severely restrict the therapeutic efficacy of this combined treatment. Herein, we report biodegradable doxorubicin (Dox)-loaded copper-metformin (Met) nanoscale coordination polymers (Dox@Cu-Met NPs), which exert a chemo/chemodynamic synergistic therapeutic effect by reducing oxygen (O2) consumption to promote H2O2 accumulation in the tumor. Inside tumor cells, Met can inhibit the consumption of O2 to relieve tumor hypoxia by suppressing mitochondrial respiration. The alleviated-tumor hypoxia can not only elevate H2O2 content via the Dox-activated cascade reaction of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and superoxide dismutase (SOD), but also improve the efficacy of Dox. More importantly, the depletion of glutathione (GSH) accompanies the whole treatment process, which can realize the conversion of Cu2+ to Cu+ and boost reactive oxygen species (ROS) accumulation to improve chemodynamic therapy (CDT) efficacy. Meanwhile, Met is expected to cut off the energy supply by inhibiting respiration, leading to starvation therapy. In vivo investigations demonstrate that tumor growth is significantly inhibited through the enhanced chemo/chemodynamic synergistic treatment. This work provides a new paradigm for cancer therapy using an economical and straightforward method to construct a synergistic nanomedicine platform.

Hepatic LDL receptor-related protein-1 deficiency alters mitochondrial dynamics through phosphatidylinositol 4,5-bisphosphate reduction

The LDL receptor-related protein 1 (LRP1) is a multifunctional transmembrane protein with endocytosis and signal transduction functions. Previous studies have shown that hepatic LRP1 deficiency exacerbates diet-induced steatohepatitis and insulin resistance via mechanisms related to increased lysosome and mitochondria permeability and dysfunction. The current study examined the impact of LRP1 deficiency on mitochondrial function in the liver. Hepatocytes isolated from liver-specific LRP1 knockout (hLrp1−/−) mice showed reduced oxygen consumption compared with control mouse hepatocytes. The mitochondria in hLrp1−/− mouse livers have an abnormal morphology and their membranes contain significantly less anionic phospholipids, including lower levels of phosphatidylethanolamine and cardiolipin that increase mitochondrial fission and impair fusion. Additional studies showed that LRP1 complexes with phosphatidylinositol 4-phosphate 5-kinase like protein-1 (PIP5KL1) and phosphatidylinositol 4-phosphate 5-kinase-1β (PIP5K1β). The absence of LRP1 reduces the levels of both PIP5KL1 and PIP5K1β in the plasma membrane and also lowers phosphatidylinositol(4,5) bisphosphate (PI(4,5)P2) levels in hepatocytes. These data indicate that LRP1 recruits PIP5KL1 and PIP5K1β to the plasma membrane for PI(4,5)P2 biosynthesis. The lack of LRP1 reduces lipid kinase expression, leading to lower PI(4,5)P2 levels, thereby decreasing the availability of this lipid metabolite in the cardiolipin biosynthesis pathway to cause cardiolipin reduction and the impairment in mitochondria homeostasis. Taken together, the current study identifies another signaling mechanism by which LRP1 regulates cell functions: binding and recruitment of PIP5KL1 and PIP5K1β to the membrane for PI(4,5)P2 synthesis. In addition, it highlights the importance of this mechanism for maintaining the integrity and functions of intracellular organelles.

Yeast Translation Elongation Factor eIF5A Expression Is Regulated by Nutrient Availability through Different Signalling Pathways.

Translation elongation factor eIF5A binds to ribosomes to promote peptide bonds between problematic amino acids for the reaction like prolines. eIF5A is highly conserved and essential in eukaryotes, which usually contain two similar but differentially expressed paralogue genes. The human eIF5A-1 isoform is abundant and implicated in some cancer types; the eIF5A-2 isoform is absent in most cells but becomes overexpressed in many metastatic cancers. Several reports have connected eIF5A and mitochondria because it co-purifies with the organelle or its inhibition reduces respiration and mitochondrial enzyme levels. However, the mechanisms of eIF5A mitochondrial function, and whether eIF5A expression is regulated by the mitochondrial metabolism, are unknown. We analysed the expression of yeast eIF5A isoforms Tif51A and Tif51B under several metabolic conditions and in mutants. The depletion of Tif51A, but not Tif51B, compromised yeast growth under respiration and reduced oxygen consumption. Tif51A expression followed dual positive regulation: by high glucose through TORC1 signalling, like other translation factors, to promote growth and by low glucose or non-fermentative carbon sources through Snf1 and heme-dependent transcription factor Hap1 to promote respiration. Upon iron depletion, Tif51A was down-regulated and Tif51B up-regulated. Both were Hap1-dependent. Our results demonstrate eIF5A expression regulation by cellular metabolic status.

Disulfiram Chelated With Copper Inhibits the Growth of Gastric Cancer Cells by Modulating Stress Response and Wnt/β-catenin Signaling.

Disulfiram (DSF) is a well-known drug for alcohol abuse. In recent decades, DSF has been demonstrated to exhibit anti-tumor activity; DSF chelated with copper shows enhanced anti-tumor effect. Our goal was to explore the effect of DSF/Cu complex on the growth and metastasis of gastric cancer (GC) in vitro and in vivo. DSF/Cu complex suppressed the proliferation, migration of MKN-45 and BGC-823 GC cells. Furthermore, DSF/Cu treatment reduced the tumor volume in GC mouse models with a tumor suppression rate of 48.24%. Additionally, DSF/Cu induced apoptosis in vitro in MKN-45 and BGC-823 GC cells in a dose- and time-dependent manner as well as in vivo in the xenograft tumor mouse model. Furthermore, DSF/Cu induced autophagy and autophagic flux in MKN-45 and BGC-823 cells, increased the expression of autophagy-related Beclin-1 and LC3 proteins in vivo. Additionally, DSF/Cu suppressed aerobic glycolysis and oxidative phosphorylation by reducing oxygen consumption rate and extracellular acidification rate, respectively, in MKN-45 and BGC-823 cells. Treatment with DSF/Cu induced oxidative stress and DNA damage response by elevating the reactive oxygen species levels; increasing the expression of P53, P21, and γ-H2AX proteins; and inhibiting Wnt/β-catenin signaling in vitro and in vivo. Thus, DSF/Cu suppressed the growth and metastasis of GC cells via modulating the stress response and Wnt/β-catenin signaling. Hence, DSF may be used as a potential therapeutic agent for the treatment of GC.

Mitochondrial quality surveillance as a therapeutic target in myocardial infarction.

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide. As mitochondrial dysfunction critically contributes to the pathogenesis of MI, intensive research is focused on the development of therapeutic strategies targeting mitochondrial homeostasis. Mitochondria possess a quality control system which maintains and restores their structure and function by regulating mitochondrial fission, fusion, biogenesis, degradation and death. In response to slight damage such as transient hypoxia or mild oxidative stress, mitochondrial metabolism shifts from oxidative phosphorylation to glycolysis, in order to reduce oxygen consumption and maintain ATP output. Mitochondrial dynamics are also activated to modify mitochondrial shape and structure, in order to meet cardiomyocyte energy requirements through augmenting or reducing mitochondrial mass. When damaged mitochondria cannot be repaired, poorly structured mitochondria will be degraded through mitophagy, a process which is often accompanied by mitochondrial biogenesis. Once the insult is severe enough to induce lethal damage in the mitochondria and the cell, mitochondrial death pathway activation is an inevitable consequence, and the cardiomyocyte apoptosis or necrosis program will be initiated to remove damaged cells. Mitochondrial quality surveillance is a hierarchical system preserving mitochondrial function and defending cardiomyocytes against stress. A failure of this system has been regarded as one of the potential pathologies underlying MI. In this review, we discuss the recent findings focusing on the role of mitochondrial quality surveillance in MI, and highlight the available therapeutic approaches targeting mitochondrial quality surveillance during MI.

HypoxamiR-210 accelerates wound healing in diabetic mice by improving cellular metabolism

Wound healing is a high energy demanding process that needs a good coordination of the mitochondria with glycolysis in the characteristic highly hypoxic environment. In diabetes, hyperglycemia impairs the adaptive responses to hypoxia with profound negative effects on different cellular compartments of wound healing. miR-210 is a hypoxia-induced microRNA that regulates cellular metabolism and processes important for wound healing. Here, we show that hyperglycemia blunted the hypoxia-dependent induction of miR-210 both in vitro and in human and mouse diabetic wounds. The impaired regulation of miR-210 in diabetic wounds is pathogenic, since local miR-210 administration accelerated wound healing specifically in diabetic but not in non-diabetic mice. miR-210 reconstitution restores the metabolic balance in diabetic wounds by reducing oxygen consumption rate and ROS production and by activating glycolysis with positive consequences on cellular migration. In conclusion, miR-210 accelerates wound healing specifically in diabetes through improvement of the cellular metabolism.

Risk stratification in cardiomyopathy.

Prognostic stratification of cardiomyopathies represents a cornerstone for the appropriate management of patients and is focused mainly on arrhythmic events and heart failure. Cardiopulmonary exercise testing provides additional prognostic information, particularly in the setting of heart failure. Cardiopulmonary exercise testing data, integrated in scores such as the Metabolism Exercise Cardiac Kidney Index score have been shown to improve the risk stratification of these patients. Cardiopulmonary exercise testing has been analysed as a potential supplier of prognostic parameters in the context of hypertrophic cardiomyopathy, for which it has been shown that a reduced oxygen consumption peak, an increased ventilation/carbon dioxide production slope and chronotropic incompetence correlate with a worse prognosis. To a lesser extent, in dilated cardiomyopathy, it has been shown that the percentage of oxygen consumption peak, not the pure value, and the ventilation/carbon dioxide production slope are associated with a greater cardiovascular risk. Few data are available about other cardiomyopathies (arrhythmogenic and restrictive). Cardiomyopathy patients should be early and routinely referred to heart failure advanced centres in order to perform a comprehensive risk stratification which should include a cardiopulmonary exercise test, with variables and cut-offs shown to improve their risk stratification.

Abstract PR04: Transcriptional regulation of mitochondrial metabolism by TIF1γ drives erythroid progenitor differentiation

Abstract Understanding in-vivo mechanisms of erythropoiesis is critical for directed differentiation approaches to treat blood disorders such as leukemias. Zebrafish moonshine (mon) mutant embryos defective for the conserved transcriptional intermediary factor 1 gamma (tif1γ) do not specify enough erythroid progenitors due to a transcription elongation block characterized by aberrantly paused RNA polymerase II. To elucidate the TIF1γ-mediated mechanisms in erythroid differentiation, we performed a chemical suppressor screen using 3,100 compounds and identified inhibitors of the essential mitochondrial pyrimidine synthesis enzyme dihydroorotate dehydrogenase (DHODH). Leflunomide as well as the structurally unrelated DHODH inhibitor brequinar rescue the formation of erythroid progenitors in 61% (38/62) and 68% (50/74) of mon embryos, respectively. Beyond changes in nucleotide metabolism, in-vivo metabolic analyses revealed low levels of TCA cycle metabolites which were functionally linked to a reduced oxygen consumption rate. In addition, an increased 2HG/αKG ratio was associated with higher histone methylation states at H3K27, H3K36 and H4K20 as assessed by quantitative targeted mass spectrometry, which may contribute to the erythroid differentiation block upon tif1γ loss. DHODH is the only pyrimidine de novo synthesis enzyme located in mitochondria and its activity is coupled to that of the electron transport chain (ETC) via coenzyme Q (CoQ). Rotenone, a potent ETC complex I inhibitor reversed the rescue by DHODH inhibition in mon embryos. Through parallel genome-wide transcriptome and chromatin immunoprecipitation analyses, we found that genes encoding CoQ metabolic enzymes are direct TIF1γ targets. Treatment with the CoQ analog decylubiquinone rescued erythroid progenitors in 26% (33/126) of mon embryos. These results demonstrate a tight coordination of nucleotide and mitochondrial metabolism as a key function of tif1γ-dependent transcription and reveal that TIF1γ activity regulates a metabolic program that drives cell fate decisions in the early blood lineage. Our work highlights the importance of the plasticity achieved by transcription regulatory processes such as transcription elongation for metabolic processes during lineage differentiation and could have therapeutic potential for blood diseases. Citation Format: Marlies P. Rossmann, Karen Hoi, Victoria Chan, Brian J. Abraham, Song Yang, James Mullahoo, Malvina Papanastasiou, Ilaria Elia, Sejal Vyas, Partha P. Nag, Lucas B. Sullivan, Julie R. Perlin, Elliott J. Hagedorn, Sara Hetzel, Raha Weigert, Curtis R. Warren, Bilguujin Dorjsuren, Eugenia Custo Greig, Chad A. Cowan, Stuart L. Schreiber, Richard A. Young, Alexander Meissner, Marcia Haigis, Steven A. Carr, Leonard I. Zon. Transcriptional regulation of mitochondrial metabolism by TIF1γ drives erythroid progenitor differentiation [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PR04.

110 Metmyoglobin reducing activity and oxygen consumption properties of atypical dark-cutting beef

Abstract Deviation from characteristic bright-red color during grading leads to discounted carcass price and value. Dark-cutting carcasses are examples of color deviation due to high-pH. However, atypical dark-cutters are not discounted at grading but have a dark color compared to normal-pH beef. Limited knowledge is currently available on the biochemical properties of atypical dark cutting beef compared with normal-pH beef. Therefore, the objective of the study was to determine metmyoglobin reducing activity and oxygen consumption of atypical dark-cutting beef. Strip loins from atypical dark-cutting (ADC; selected based on HunterLab L* values and pH less than 5.8 and not discounted by grader) and USDA Low Choice (C) carcasses were selected from a commercial beef processing plant and transported to the Food and Agricultural Products Center in Stillwater, Oklahoma. pH, color, oxygen consumption, and metmyoglobin reducing activity of atypical dark cutters and normal pH loins were determined on d3 postmortem. The surface color was determined using a HunterLab Miniscan spectrophotometer. Reflectance-based methods using K/S ratios were utilized to determine oxygen consumption and metmyoglobin reducing activity. The data were analyzed using the Mixed Procedure of SAS and the experiment was replicated 10 times (n = 10). There were no differences in initial pH (C = 5.46 and ADC = 5.6 atypical dark-cutter; P = 0.05) between normal-pH and atypical dark cutters. However, atypical dark cutters had lower lightness (L* values; C = 44.2 and ADC = 38.4), redness (a* values; C = 28.6 and ADC = 25.2), and red intensity (chroma; C = 40.2 and ADC = 36.4) compared with normal-pH. Further, atypical dark cutters had greater (P < 0.05) oxygen consumption and metmyoglobin reducing activity than normal-pH. The results suggest that atypical dark cutters and normal-pH beef have different biochemical properties.

The reduction of lipid-sourced energy production caused by ATGL inhibition cannot be compensated by activation of HSL, autophagy, and utilization of other nutrients in fish.

The adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL)-mediated lipolysis play important roles in lipid catabolism. ATGL is considered the central rate-limiting enzyme in the mobilization of fatty acids in mammals. Currently, severe fat accumulation has been commonly detected in farmed fish globally. However, the ATGL-mediated lipolysis and the potential synergy among ATGL, HSL, and autophagy, which is another way for lipid breakdown, have not been intensively understood in fish. In the present study, we added Atglistatin as an ATGL-specific inhibitor into the zebrafish diet and fed to the fish for 5weeks. The results showed that the Atglistatin-treated fish exhibited severe fat deposition, reduced oxygen consumption, and fatty acid β-oxidation, accompanied with increased oxidative stress and inflammation. Furthermore, the Atglistatin-treated fish elevated total and phosphorylation protein expressions of HSL. However, the free fatty acids and lipase activities in organs were still systemically reduced in the Atglistatin-treated fish, and the autophagy marker LC3 was also decreased in the liver. On the other hand, glycogenolysis was stimulated but blood glucose was higher in the Atglistatin-treated fish. The transcriptomic analysis also provided the hint that the protein turnover efficiency in Atglistatin-treated fish was likely to be accelerated, but the protein content in whole fish was not affected. Taken together, ATGL plays crucial roles in energy homeostasis such that its inhibition causes loss of lipid-sourced energy production, which cannot be compensated by activation of HSL, autophagy, and utilization of other nutrients.

Kidney epithelial targeted mitochondrial transcription factor A deficiency results in progressive mitochondrial depletion associated with severe cystic disease

Abnormal mitochondrial function is a well-recognized feature of acute and chronic kidney diseases. To gain insight into the role of mitochondria in kidney homeostasis and pathogenesis, we targeted mitochondrial transcription factor A (TFAM), a protein required for mitochondrial DNA replication and transcription that plays a critical part in the maintenance of mitochondrial mass and function. To examine the consequences of disrupted mitochondrial function in kidney epithelial cells, we inactivated TFAM in sine oculis-related homeobox 2-expressing kidney progenitor cells. TFAM deficiency resulted in significantly decreased mitochondrial gene expression, mitochondrial depletion, inhibition of nephron maturation and the development of severe postnatal cystic disease, which resulted in premature death. This was associated with abnormal mitochondrial morphology, a reduction in oxygen consumption and increased glycolytic flux. Furthermore, we found that TFAM expression was reduced in murine and human polycystic kidneys, which was accompanied by mitochondrial depletion. Thus, our data suggest that dysregulation of TFAM expression and mitochondrial depletion are molecular features of kidney cystic disease that may contribute to its pathogenesis.

Soluble factors released by dedifferentiated fat cells reduce the functional activity of iPS cell-derived cardiomyocytes.

Interactions between tissues such as epicardial adipose (EAT), and myocardial tissues is important in the pathogenesis of heart failure. Changes in adipose tissues in obesity or diabetes impair preadipocyte differentiation. Furthermore, proinflammatory cytokine secretion is higher in preadipocytes than in mature adipocytes in diabetes and obesity. However, how undifferentiated cells committed to the adipose lineage directly influence cardiomyocytes is not yet understood. We used human-derived dedifferentiated fat (DFAT) cells as models of undifferentiated cells committed to an adipose lineage. Here, we evaluated the effects of soluble factor interactions in indirect cocultures of DFAT cells and induced pluripotent stem cell-derived cardiomyocytes. Our RNA sequencing findings showed that these interactions were predominantly inflammatory responses. Furthermore, proinflammatory cytokines secreted by DFAT cells reduced myocardial functions such as contraction frequency and catecholamine sensitivity, and simultaneously increased apoptosis, decreased antioxidative stress tolerance, and reduced oxygen consumption rates in cardiomyocytes. These adverse effects might be attributable to monocyte chemoattractant protein-1, chemokine (C-X-C motif) ligands 1 (CXCL1), and 12, granulocyte colony-stimulating factor, interleukins 6 and 8, macrophage migration inhibitory factor (MIF), and plasminogen activator inhibitor 1-A among the proinflammatory mediators secreted by DFAT cells. Our results could be useful for understanding the pathogenesis of EAT-related heart failure in terms of the involvement of undifferentiated cells committed to the adipose lineage. Furthermore, we suggest the importance of focusing on surrounding adipose tissues as a strategy with which to maximize the survival and function of transplanted stem cell-derived cardiomyocytes.

How costly are metacercarial infections in a bivalve host? Effects of two trematode species on biochemical performance of cockles

Bivalve stocks have been decreasing in the last decades largely due to emergent diseases and consequent mass mortality episodes. Cerastoderma edule (the edible cockle) is one of the most exploited bivalves in Europe and is among the most common hosts for trematodes, the most prevalent macroparasites in coastal waters but yet poorly studied. Therefore, in the present study, this bivalve species was used as host model to determine if trematode infection exerts a negative effect on bivalve energy metabolism and balance and if the tissues targeted by different trematodes influence the metabolic cost, with physiological and biochemical consequences. Cockles were experimentally infected with two trematode species, Himasthla elongata and Renicola roscovitus, that infect the foot and palps, respectively. Trematode infection exerted a negative effect on the metabolism of C. edule, the second intermediate host, by reduction of oxygen consumption. A different host biochemical response was found depending on trematode species, especially in regard to the level of oxygen consumption decrease and the preferential accumulation of lipids and glycogen. This study represents a step towards the understanding of host-trematode relationships that can be used to better predict potential conservation threats to bivalve populations and to maximize the success of stock and disease management.

The use of Ocimum gratissimum L. essential oil during the transport of Lophiosilurus alexandri: Water quality, hematology, blood biochemistry and oxidative stress

This study evaluated the effects of the essential oil of Ocimum gratissimum L. (EOOG) on water quality, blood characteristics and tissue damage during transport of Lophiosilurus alexandri. One hundred and sixty juveniles of L. alexandri (123.44 ± 1.95 g and 23.71 ± 1.95 cm) were fasted for 24 h before transportation. Fish were then submitted to one of three treatments of transport water with five replicates each: 0 (control), 5 and 10 mg/L EOOG. The animals were transported for 4 h in plastic bags at a density of 1 juvenile/L and 10 animals per bag. The ventilatory frequency of one fish from each bag was determined after 3 h of transport by direct observation and counting of opercular beats. Blood, brain and liver samples were collected prior to (basal group) and at the end of transport from 10 animals each. Blood aliquots were used to determine hematocrit and hemoglobin, total plasma protein, glucose, aspartate aminotransferase and alanine aminotransferase levels. Samples of liver and brain were used to determine parameters and oxidative stress (reactive oxygen species, glutathione peroxidase, superoxide dismutase, glutathione S-transferase, lipid peroxidation and protein carbonyl formation). No mortality was observed 24 h after transport. The addition of EOOG to transport water appeared to reduce animal metabolism, thus ensuring higher dissolved oxygen and lower ammonia levels. Juveniles transported with 10 mg/L EOOG also had reduced opercular beats, lower levels of hemoglobin and blood aspartate aminotransferase and glucose. This concentration also reduced lipid and protein oxidation levels in tissues, thereby avoiding lipid peroxidation and the formation of carbonyl protein. The use of 10 mg/L EOOG during transport promotes a sedative effect in L. alexandri, with reduced oxygen consumption, ammonia excretion and biochemical changes and enhanced protection against oxidative damage.

Malic Enzyme Couples Mitochondria with Aerobic Glycolysis in Osteoblasts

SUMMARYThe metabolic program of osteoblasts, the chief bone-making cells, remains incompletely understood. Here in murine calvarial cells, we establish that osteoblast differentiation under aerobic conditions is coupled with a marked increase in glucose consumption and lactate production but reduced oxygen consumption. As a result, aerobic glycolysis accounts for approximately 80% of the ATP production in mature osteoblasts. In vivo tracing with 13C-labeled glucose in the mouse shows that glucose in bone is readily metabolized to lactate but not organic acids in the TCA cycle. Glucose tracing in osteoblast cultures reveals that pyruvate is carboxylated to form malate integral to the malate-aspartate shuttle. RNA sequencing (RNA-seq) identifies Me2, encoding the mitochondrial NAD-dependent isoform of malic enzyme, as being specifically upregulated during osteoblast differentiation. Knockdown of Me2 markedly reduces the glycolytic flux and impairs osteoblast proliferation and differentiation. Thus, the mitochondrial malic enzyme functionally couples the mitochondria with aerobic glycolysis in osteoblasts.

Oxidative stress-mediated mitochondrial dysfunction facilitates mesenchymal stem cell senescence in ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease possessing a morbid serum microenvironment with enhanced oxidative stress. Long-term exposure to an oxidative environment usually results in cellular senescence alone with cellular dysfunction. Mesenchymal stem cells (MSCs) are a kind of stem cell possessing strong capabilities for immunoregulation, and senescent MSCs may increase inflammation and participate in AS pathogenesis. The objective of this study was to explore whether and how the oxidative serum environment of AS induces MSC senescence. Here, we found that AS serum facilitated senescence of MSCs in vitro, and articular tissues from AS patients exhibited higher expression levels of the cell cycle arrest-related proteins p53, p21 and p16. Importantly, the levels of advanced oxidative protein products (AOPPs), markers of oxidative stress, were increased in AS serum and positively correlated with the extent of MSC senescence induced by AS serum. Furthermore, MSCs cultured with AS serum showed decreased mitochondrial membrane potential and ATP production together with a reduced oxygen consumption rate. Finally, we discovered that AS serum-induced mitochondrial dysfunction resulted in elevated reactive oxygen species (ROS) in MSCs, and ROS inhibition successfully rescued MSCs from senescence. In conclusion, our data demonstrated that the oxidative serum environment of AS facilitated MSC senescence through inducing mitochondrial dysfunction and excessive ROS production. These results may help elucidate the pathogenesis of AS and provide potential targets for AS treatment.

Prolonged exposure to hypoxia inhibits the growth of Pacific abalone by modulating innate immunity and oxidative status

In aquatic animals, hypoxia is associated with growth retardation, impaired immunity, susceptibility to pathogens, oxidative stress, and mortality. However, the relative long-term effects of hypoxia on bivalves, including abalone, are not well understood. In this study, we examined the effects of exposure to hypoxic (2.5 and 4 mg O2 L−1) and normoxic (8 mg O2 L−1) conditions on the growth, survival, and immune and antioxidant responses of the economically important Pacific abalone Haliotis discus hannai over a 4 month period. We observed that exposure to 2.5 mg O2 L−1 resulted in marked reductions in assessed shell parameters, average meat weight, and survival compared with exposure to 4 and 8 mg O2 L–1. There were also significant reductions in oxygen consumption and ammonia-N excretion in abalone exposed to 2.5 mg O2 L−1. We also detected initial immunosuppression in the 2.5 mg O2 L−1-treated abalone, as evidenced by a significant reduction in total hemocytes and inhibition of antibacterial and lysozyme activities. Furthermore, intracellular malondialdehyde concentrations were significantly elevated at 1 month in the 2.5 mg O2 L−1 treatment group, whereas there were reductions in the levels of glutathione and enzymatic activities of catalase and superoxide dismutase, thereby indicating potential hypoxia-induced oxidative stress and a depression of antioxidant capacity. After 4 months of treatment, severe hypoxia (2.5 mg O2 L−1) had significantly modulated all measured parameters, whereas exposure to 4 and 8 mg O2 L−1 had induced no significant effects. Collectively, our observations indicate that under long-term exposure to hypoxia, Pacific abalone failed to maintain an effective antioxidant defense system and adequate immunity, with the observed biochemical disruptions leading to a reduction in growth and survival.