Intracellular sodium elevation reprograms cardiac metabolism

Intracellular Na elevation in the heart is a hallmark of pathologies where both acute and chronic metabolic remodelling occurs. Here, we assess whether acute (75 μM ouabain 100 nM blebbistatin) or chronic myocardial Nai load (PLM3SA mouse) are causally linked to metabolic remodelling and whether the failing heart shares a common Na-mediated metabolic ‘fingerprint’. Control (PLMWT), transgenic (PLM3SA), ouabain-treated and hypertrophied Langendorff-perfused mouse hearts are studied by 23Na, 31P, 13C NMR followed by 1H-NMR metabolomic profiling. Elevated Nai leads to common adaptive metabolic alterations preceding energetic impairment: a switch from fatty acid to carbohydrate metabolism and changes in steady-state metabolite concentrations (glycolytic, anaplerotic, Krebs cycle intermediates). Inhibition of mitochondrial Na/Ca exchanger by CGP37157 ameliorates the metabolic changes. In silico modelling indicates altered metabolic fluxes (Krebs cycle, fatty acid, carbohydrate, amino acid metabolism). Prevention of Nai overload or inhibition of Na/Camito may be a new approach to ameliorate metabolic dysregulation in heart failure

Fasting increases susceptibility to acute myocardial ischaemia/reperfusion injury through a sirtuin-3 mediated increase in fatty acid oxidation.

Fasting increases susceptibility to acute myocardial ischaemia/reperfusion injury (IRI) but the mechanisms are unknown. Here, we investigate the role of the mitochondrial NAD+-dependent deacetylase, Sirtuin-3 (SIRT3), which has been shown to influence fatty acid oxidation and cardiac outcomes, as a potential mediator of this effect. Fasting was shown to shift metabolism from glucose towards fatty acid oxidation. This change in metabolic fuel substrate utilisation increased myocardial infarct size in wild-type (WT), but not SIRT3 heterozygous knock-out (KO) mice. Further analysis revealed SIRT3 KO mice were better adapted to starvation through an improved cardiac efficiency, thus protecting them from acute myocardial IRI. Mitochondria from SIRT3 KO mice were hyperacetylated compared to WT mice which may regulate key metabolic processes controlling glucose and fatty acid utilisation in the heart. Fasting and the associated metabolic switch to fatty acid respiration worsens outcomes in WT hearts, whilst hearts from SIRT3 KO mice are better adapted to oxidising fatty acids, thereby protecting them from acute myocardial IRI

On the pivotal role of PPARa in adaptation of the heart to hypoxia and why fat in the diet increases hypoxic injury

The role of peroxisome proliferator activated alpha (PPARα) -mediated metabolic remodeling in cardiac adaptation to hypoxia has yet to be defined. Here, mice were housed in hypoxia for 3 weeks before in vivo contractile function was measured using cine magnetic resonance (MR) imaging. In isolated, perfused hearts, energetics were measured using 31P MR spectroscopy and glycolysis and fatty acid oxidation were measured using 3H labelling. Compared with normoxic, chow-fed control mouse heart, hypoxia decreased PPARα expression, fatty acid oxidation and mitochondrial UCP3 levels, while increasing glycolysis, all of which served to maintain normal ATP concentrations and thereby ejection fractions. A high-fat diet increased cardiac PPARα expression, fatty acid oxidation and UCP3 levels, with decreased glycolysis. Hypoxia was unable to alter the high PPARα expression or reverse the metabolic changes caused by the high fat diet, with the result that ATP concentrations and contractile function decreased significantly. The adaptive metabolic changes caused by hypoxia in control mouse hearts were found to have already occurred in PPARα-/- mouse hearts, and sustained function in hypoxia despite an inability for further metabolic remodelling. We conclude that decreased cardiac PPARα expression is essential for adaptive metabolic remodelling in hypoxia, but is prevented by dietary fat

Ischaemic accumulation of succinate controls reperfusion injury through mitochondrial ROS.

Ischaemia-reperfusion injury occurs when the blood supply to an organ is disrupted and then restored, and underlies many disorders, notably heart attack and stroke. While reperfusion of ischaemic tissue is essential for survival, it also initiates oxidative damage, cell death and aberrant immune responses through the generation of mitochondrial reactive oxygen species (ROS). Although mitochondrial ROS production in ischaemia reperfusion is established, it has generally been considered a nonspecific response to reperfusion. Here we develop a comparative in vivo metabolomic analysis, and unexpectedly identify widely conserved metabolic pathways responsible for mitochondrial ROS production during ischaemia reperfusion. We show that selective accumulation of the citric acid cycle intermediate succinate is a universal metabolic signature of ischaemia in a range of tissues and is responsible for mitochondrial ROS production during reperfusion. Ischaemic succinate accumulation arises from reversal of succinate dehydrogenase, which in turn is driven by fumarate overflow from purine nucleotide breakdown and partial reversal of the malate/aspartate shuttle. After reperfusion, the accumulated succinate is rapidly re-oxidized by succinate dehydrogenase, driving extensive ROS generation by reverse electron transport at mitochondrial complex I. Decreasing ischaemic succinate accumulation by pharmacological inhibition is sufficient to ameliorate in vivo ischaemia-reperfusion injury in murine models of heart attack and stroke. Thus, we have identified a conserved metabolic response of tissues to ischaemia and reperfusion that unifies many hitherto unconnected aspects of ischaemia-reperfusion injury. Furthermore, these findings reveal a new pathway for metabolic control of ROS production in vivo, while demonstrating that inhibition of ischaemic succinate accumulation and its oxidation after subsequent reperfusion is a potential therapeutic target to decrease ischaemia-reperfusion injury in a range of pathologies

Fumarate is cardioprotective via activation of the Nrf2 antioxidant pathway

The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents. © 2012 Elsevier Inc

With a grain of salt: Sodium elevation and metabolic remodelling in heart failure.

Elevated intracellular Na (Nai) and metabolic impairment are interrelated pathophysiological features of the failing heart (HF). There have been a number of studies showing that myocardial sodium elevation subtly affects mitochondrial function. During contraction, mitochondrial calcium (Camito) stimulates a variety of TCA cycle enzymes, thereby providing reducing equivalents to maintain ATP supply. Nai elevation has been shown to impact Camito; however, whether metabolic remodelling in HF is caused by increased Nai has only been recently demonstrated. This novel insight may help to elucidate the contribution of metabolic remodelling in the pathophysiology of HF, the lack of efficacy of current HF therapies and a rationale for the development of future metabolism-targeting treatments. Here we review the relationship between Na pump inhibition, elevated Nai, and altered metabolic profile in the context of HF and their link to metabolic (in)flexibility and mitochondrial reprogramming

Detection of PBP2a (penicillin-binding protein 2a) and mecA gene in methicillin resistant staphylococci originated from animals

For the purpose of detecting methicillin (oxacillin) resistance in staphylococcal strains, in a number of microbiological laboratories only disc diffusion method with cefoxitin and/or oxacillin discs is used. Besides this method, it is desirable to determine MIC values for cefoxitin and/or oxacillin. After examination by disc diffusion and dilution methods, latex agglutination is used for the detection of PBP2a and PCR is used for the detection of mecA gene. Use of PCR is not possible in a large number of diagnostic laboratories and as method of choice, latex agglutination test for rapid detection of PBP2a is recommended. In this investigation, as confirmatory methods, latex agglutination and PCR were used for strains that were resistant to oxacillin and/or cefoxitin by disc diffusion and broth microdilution methods. In total, 14 strains of coagulase-negative staphylococci originating from clinical specimens of cats, dogs and chicken were examined. Among isolated strains, it was established that the dominating species was Staphylococcus haemolyticus with 11 isolated strains. Other isolated species were Staphylococcus epidermidis, Staphylococcus capitis and Staphylococcus vitulinus, each with one isolated strain. For all 14 strains, oxacillin MIC values ranged from 0.5 μg/mL to >64 μg/mL and cefoxitin MIC values ranged from 1 μg/mL to >256 μg/mL. Positive agglutination reaction by latex agglutination test was recorded in 13 out of 14 strains. The PCR assay for mecA gene was positive in 12 investigated strains. [Projekat Ministarstva nauke Republike Srbije, br. 31079

Myocardial creatine levels do not influence response to acute oxidative stress in isolated perfused heart

BACKGROUND: Multiple studies suggest creatine mediates anti-oxidant activity in addition to its established role in cellular energy metabolism. The functional significance for the heart has yet to be established, but antioxidant activity could contribute to the cardioprotective effect of creatine in ischaemia/reperfusion injury. OBJECTIVES: To determine whether intracellular creatine levels influence responses to acute reactive oxygen species (ROS) exposure in the intact beating heart. We hypothesised that mice with elevated creatine due to over-expression of the creatine transporter (CrT-OE) would be relatively protected, while mice with creatine-deficiency (GAMT KO) would fare worse. METHODS AND RESULTS: CrT-OE mice were pre-selected for creatine levels 20-100% above wild-type using in vivo (1)H-MRS. Hearts were perfused in isovolumic Langendorff mode and cardiac function monitored throughout. After 20 min equilibration, hearts were perfused with either H2O2 0.5 µM (30 min), or the anti-neoplastic drug doxorubicin 15 µM (100 min). Protein carbonylation, creatine kinase isoenzyme activities and phospho-PKCδ expression were quantified in perfused hearts as markers of oxidative damage and apoptotic signalling. Wild-type hearts responded to ROS challenge with a profound decline in contractile function that was ameliorated by co-administration of catalase or dexrazoxane as positive controls. In contrast, the functional deterioration in CrT-OE and GAMT KO hearts was indistinguishable from wild-type controls, as was the extent of oxidative damage and apoptosis. Exogenous creatine supplementation also failed to protect hearts from doxorubicin-induced dysfunction. CONCLUSIONS: Intracellular creatine levels do not influence the response to acute ROS challenge in the intact beating heart, arguing against creatine exerting (patho-)physiologically relevant anti-oxidant activity

Myocardial creatine levels do not influence response to acute oxidative stress in isolated perfused heart

BACKGROUND: Multiple studies suggest creatine mediates anti-oxidant activity in addition to its established role in cellular energy metabolism. The functional significance for the heart has yet to be established, but antioxidant activity could contribute to the cardioprotective effect of creatine in ischaemia/reperfusion injury. OBJECTIVES: To determine whether intracellular creatine levels influence responses to acute reactive oxygen species (ROS) exposure in the intact beating heart. We hypothesised that mice with elevated creatine due to over-expression of the creatine transporter (CrT-OE) would be relatively protected, while mice with creatine-deficiency (GAMT KO) would fare worse. METHODS AND RESULTS: CrT-OE mice were pre-selected for creatine levels 20-100% above wild-type using in vivo (1)H-MRS. Hearts were perfused in isovolumic Langendorff mode and cardiac function monitored throughout. After 20 min equilibration, hearts were perfused with either H2O2 0.5 µM (30 min), or the anti-neoplastic drug doxorubicin 15 µM (100 min). Protein carbonylation, creatine kinase isoenzyme activities and phospho-PKCδ expression were quantified in perfused hearts as markers of oxidative damage and apoptotic signalling. Wild-type hearts responded to ROS challenge with a profound decline in contractile function that was ameliorated by co-administration of catalase or dexrazoxane as positive controls. In contrast, the functional deterioration in CrT-OE and GAMT KO hearts was indistinguishable from wild-type controls, as was the extent of oxidative damage and apoptosis. Exogenous creatine supplementation also failed to protect hearts from doxorubicin-induced dysfunction. CONCLUSIONS: Intracellular creatine levels do not influence the response to acute ROS challenge in the intact beating heart, arguing against creatine exerting (patho-)physiologically relevant anti-oxidant activity

Contribution of Particles to Air Pollution in Green Parks

Parks can aid in the regulation of microclimates and the improvement of air quality. They can be utilized in real-world systems to choose the best model for explaining the source of pollutant emissions, indicating the requirement for pollution concentration monitoring. Monitoring concentration trends is critical to formulating a strategy to reduce CO2 emissions and the contribution of these gasses to the greenhouse effect, as well as to curbing the rising levels of PM in the air. The research background of this study was performed in the green parks of Novi Sad, Serbia. The results are represented in terms of the quantity of the pollutants, and the correlation of the examined phenomena through statistical analysis. Aeroqual monitors with laser sensors were used to take measurements of particle pollution (PM2.5/10). The constant was confirmed by inter-comparison laboratory measurements of air-quality quantitative control. The measurement findings revealed a minor variance in concentration values for PM2.5/10 from 26–30 μg/m3, which were within the allowed limits, indicating that the air was moderately clean. The linear link between particle concentrations and nitrogen dioxide in the sample was also validated using simple linear regression, as was the high influence of humidity on particle concentrations