Persistent overexpression of phosphoglycerate mutase, a glycolytic enzyme, modifies energy metabolism and reduces stress resistance of heart in mice

G-quadruplex forming regions in GCK and TM6SF2 are targets for differential DNA methylation in metabolic disease and hepatocellular carcinoma patients

The alarming increase in global rates of metabolic diseases (MetDs) and their association with cancer risk renders them a considerable burden on our society. The interplay of environmental and genetic factors in causing MetDs may be reflected in DNA methylation patterns, particularly at non-canonical (non-B) DNA structures, such as G-quadruplexes (G4s) or R-loops. To gain insight into the mechanisms of MetD progression, we focused on DNA methylation and functional analyses on intragenic regions of two MetD risk genes, the glucokinase (GCK) exon 7 and the transmembrane 6 superfamily 2 (TM6SF2) intron 2-exon 3 boundary, which harbor non-B DNA motifs for G4s and R-loops.Pyrosequencing of 148 blood samples from a nested cohort study revealed significant differential methylation in GCK and TM6SF2 in MetD patients versus healthy controls. Furthermore, these regions harbor hypervariable and differentially methylated CpGs also in hepatocellular carcinoma versus normal tissue samples from The Cancer Genome Atlas (TCGA). Permanganate/S1 nuclease footprinting with direct adapter ligation (PDAL-Seq), native polyacrylamide DNA gel electrophoresis and circular dichroism (CD) spectroscopy revealed the formation of G4 structures in these regions and demonstrated that their topology and stability is affected by DNA methylation. Detailed analyses including histone marks, chromatin conformation capture data, and luciferase reporter assays, highlighted the cell-type specific regulatory function of the target regions. Based on our analyses, we hypothesize that changes in DNA methylation lead to topological changes, especially in GCK exon 7, and cause the activation of alternative regulatory elements or potentially play a role in alternative splicing.Our analyses provide a new view on the mechanisms underlying the progression of MetDs and their link to hepatocellular carcinomas, unveiling non-B DNA structures as important key players already in early disease stages.

Improved integration of single-cell transcriptome data demonstrates common and unique signatures of heart failure in mice and humans

BACKGROUND

Cardiovascular research heavily relies on mouse (Mus musculus) models to study disease mechanisms and to test novel biomarkers and medications. Yet, applying these results to patients remains a major challenge and often results in noneffective drugs. Therefore, it is an open challenge of translational science to develop models with high similarities and predictive value. This requires a comparison of disease models in mice with diseased tissue derived from humans.

RESULTS

To compare the transcriptional signatures at single-cell resolution, we implemented an integration pipeline called OrthoIntegrate, which uniquely assigns orthologs and therewith merges single-cell RNA sequencing (scRNA-seq) RNA of different species. The pipeline has been designed to be as easy to use and is fully integrable in the standard Seurat workflow.We applied OrthoIntegrate on scRNA-seq from cardiac tissue of heart failure patients with reduced ejection fraction (HFrEF) and scRNA-seq from the mice after chronic infarction, which is a commonly used mouse model to mimic HFrEF. We discovered shared and distinct regulatory pathways between human HFrEF patients and the corresponding mouse model. Overall, 54% of genes were commonly regulated, including major changes in cardiomyocyte energy metabolism. However, several regulatory pathways (e.g., angiogenesis) were specifically regulated in humans.

CONCLUSIONS

The demonstration of unique pathways occurring in humans indicates limitations on the comparability between mice models and human HFrEF and shows that results from the mice model should be validated carefully. OrthoIntegrate is publicly accessible (https://github.com/MarianoRuzJurado/OrthoIntegrate) and can be used to integrate other large datasets to provide a general comparison of models with patient data.

The role of glycolytic metabolic pathways in cardiovascular disease and potential therapeutic approaches

Cardiovascular disease (CVD) is a major threat to human health, accounting for 46% of non-communicable disease deaths. Glycolysis is a conserved and rigorous biological process that breaks down glucose into pyruvate, and its primary function is to provide the body with the energy and intermediate products needed for life activities. The non-glycolytic actions of enzymes associated with the glycolytic pathway have long been found to be associated with the development of CVD, typically exemplified by metabolic remodeling in heart failure, which is a condition in which the heart exhibits a rapid adaptive response to hypoxic and hypoxic conditions, occurring early in the course of heart failure. It is mainly characterized by a decrease in oxidative phosphorylation and a rise in the glycolytic pathway, and the rise in glycolysis is considered a hallmark of metabolic remodeling. In addition to this, the glycolytic metabolic pathway is the main source of energy for cardiomyocytes during ischemia-reperfusion. Not only that, the auxiliary pathways of glycolysis, such as the polyol pathway, hexosamine pathway, and pentose phosphate pathway, are also closely related to CVD. Therefore, targeting glycolysis is very attractive for therapeutic intervention in CVD. However, the relationship between glycolytic pathway and CVD is very complex, and some preclinical studies have confirmed that targeting glycolysis does have a certain degree of efficacy, but its specific role in the development of CVD has yet to be explored. This article aims to summarize the current knowledge regarding the glycolytic pathway and its key enzymes (including hexokinase (HK), phosphoglucose isomerase (PGI), phosphofructokinase-1 (PFK1), aldolase (Aldolase), phosphoglycerate metatase (PGAM), enolase (ENO) pyruvate kinase (PKM) lactate dehydrogenase (LDH)) for their role in cardiovascular diseases (e.g., heart failure, myocardial infarction, atherosclerosis) and possible emerging therapeutic targets.

A plasma proteomic approach in patients with heart failure after acute myocardial infarction: insights into the pathogenesis and progression of the disease

Aims

The pathogenesis of disease progression targets for patients with heart failure after acute myocardial infarction was investigated by using plasma proteomics.

Methods

The plasma proteomes of acute myocardial infarction patients with (MI-HF) and without (MI-WHF) heart failure were compared. Each group consisted of 10 patients who were matched for age and sex. The peptides were analyzed by 2-dimensional liquid chromatography coupled to tandem mass spectrometry in a high definition mode. Parallel reaction monitoring (PRM) verified the selected target proteins.

Results

We identified and quantified 2,589 and 2,222 proteins, respectively, and found 117 differentially expressed proteins (DEPs) (≥1.5-fold), when the MI-HF and MI-WHF groups were compared. Of these 51 and 66 were significantly up-regulated and down-regulated, respectively. The significant DEPs was subjected to protein-protein interaction network analysis which revealed a central role of the NF-κB signaling pathway in the MI-HF patients. PRM verified that MB, DIAPH1, VNN1, GOT2, SLC4A1, CRP, CKM, SOD3, F7, DLD, PGAM2, GOT1, UBA7 and HYOU1 were 14 proteins which were highly expressed in MI-HF patients.

Conclusions

These findings showed a group of proteins related to the NF-κB signaling pathway in the pathogenesis of patients with poor outcomes after experiencing MI-HF. These proteins may be useful candidate markers for the diagnosis of MI-HF as well as help to elucidate the pathophysiology of this major cause of mortality in older patients.

iTRAQ-based comparative proteomics reveal an enhancing role of PRDX6 in the freezability of Mediterranean buffalo sperm

BACKGROUND

Semen cryopreservation is a critical tool for breed improvement and preservation of biodiversity. However, instability of sperm freezability affects its application. The Mediterranean buffalo is one of the river-type buffaloes with the capacity for high milk production. Until now, there is no specific cryopreservation system for Mediterranean buffalo, which influences the promotion of excellent cultivars. To improve the semen freezing extender used in cryopreservation of Mediterranean buffalo, different protein datasets relating to freezability sperm were analyzed by iTRAQ-based proteomics. This study will be beneficial for further understanding the sperm freezability mechanism and developing new cryopreservation strategy for buffalo semen.

RESULTS

2652 quantified proteins were identified, including 248 significantly differentially expressed proteins (DEP). Gene Ontology (GO) analysis indicated that many these were mitochondrial proteins, enriched in the molecular function of phospholipase A2 activity and enzyme binding, and biological processes of regulation of protein kinase A signaling and motile cilium assembly. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis identified 17 significant pathways, including oxidative phosphorylation (OXPHOS). Furthermore, 7 DEPs were verified using parallel reaction monitoring or western blot, which confirmed the accuracy of the iTRAQ data. Peroxiredoxin 6 (PRDX6), which expressed 1.72-fold higher in good freezability ejaculate (GFE) compared to poor freezability ejaculate (PFE) sperms, was selected to explore the function in sperm freezability by adding recombinant PRDX6 protein into the semen freezing extender. The results showed that the motility, mitochondrial function and in vitro fertilization capacity of frozen-thawed sperm were significantly increased, while the oxidation level was significantly decreased when 0.1 mg/L PRDX6 was added compared with blank control.

CONCLUSIONS

Above results revealed the metabolic pattern of freezability of Mediterranean buffalo sperms was negatively associated with OXPHOS, and PRDX6 had protective effect on cryo-damage of frozen-thawed sperms.

Sumoylation-deficient phosphoglycerate mutase 2 impairs myogenic differentiation

Phosphoglycerate mutase 2 (PGAM2) is a critical glycolytic enzyme that is highly expressed in skeletal muscle. In humans, naturally occurring mutations in Phosphoglycerate mutase 2 have been etiologically linked to glycogen storage disease X (GSDX). Phosphoglycerate mutase 2 activity is regulated by several posttranslational modifications such as ubiquitination and acetylation. Here, we report that Phosphoglycerate mutase 2 activity is regulated by sumoylation-a covalent conjugation involved in a wide spectrum of cellular events. We found that Phosphoglycerate mutase 2 contains two primary SUMO acceptor sites, lysine (K)49 and K176, and that the mutation of either K to arginine (R) abolished Phosphoglycerate mutase 2 sumoylation. Given that K176 is more highly evolutionarily conserved across paralogs and orthologs than K49 is, we used the CRISPR-mediated homologous recombination technique in myogenic C2C12 cells to generate homozygous K176R knock-in cells (PGAM2^K176R/K176R). Compared with wild-type (WT) C2C12 cells, PGAM2^K176R/K176R C2C12 cells exhibited impaired myogenic differentiation, as indicated by decreased differentiation and fusion indexes. Furthermore, the results of glycolytic and mitochondrial stress assays with the XF96 Extracellular Flux analyzer revealed a reduced proton efflux rate (PER), glycolytic PER (glycoPER), extracellular acidification rate (ECAR), and oxygen consumption rate (OCR) in PGAM2^K176R/K176R C2C12 cells, both at baseline and in response to stress. Impaired mitochondrial function was also observed in PGAM2^K176R/K176R P19 cells, a carcinoma cell line. These findings indicate that the PGAM2-K176R mutation impaired glycolysis and mitochondrial function. Gene ontology term analysis of RNA sequencing data further revealed that several downregulated genes in PGAM2^K176R/K176R C2C12 cells were associated with muscle differentiation/development/contraction programs. Finally, PGAM2 with either of two naturally occurring missense mutations linked to GSDX, E89A (conversion of glutamic acid 89 to alanine) or R90W (conversion of arginine 90 to tryptophan), exhibited reduced Phosphoglycerate mutase 2 sumoylation. Thus, sumoylation is an important mechanism that mediates Phosphoglycerate mutase 2 activity and is potentially implicated in Phosphoglycerate mutase 2 mutation-linked disease in humans.

TMPRSS12 Functions in Meiosis and Spermiogenesis and Is Required for Male Fertility in Mice

Serine proteases are involved in many physiological activities as initiators of proteolytic cascades, and some members have been reported to play roles in male reproduction. Transmembrane serine protease 12 (TMPRSS12) has been shown to regulate sperm motility and uterotubal junction migration in mice, but its role in the testis remains unknown. In this study, we verified that TMPRSS12 was expressed in the spermatocytes and spermatids of testis and the acrosome of sperm. Mice deficient in Tmprss12 exhibited male sterility. In meiosis, TMPRSS12 was demonstrated to regulate synapsis and double-strand break repair; spermatocytes of Tmprss12^−/− mice underwent impaired meiosis and subsequent apoptosis, resulting in reduced sperm counts. During spermiogenesis, TMPRSS12 was found to function in the development of mitochondria; abnormal mitochondrial structure in Tmprss12^−/− sperm led to reduced availability of ATP, impacting sperm motility. The differential protein expression profiles of testes in Tmprss12^−/− and wild-type mice and further molecule identification revealed potential targets of TMPRSS12 related to meiosis and mitochondrial function. Besides, TMPRSS12 was also found to be involved in a series of sperm functions, including capacitation, acrosome reaction and sperm-egg interaction. These data imply that TMPRSS12 plays a role in multiple aspects of male reproduction.

Identification and Functional Characterization of Toxoneuron nigriceps Ovarian Proteins Involved in the Early Suppression of Host Immune Response

The endophagous parasitoid Toxoneuron nigriceps (Viereck) (Hymenoptera, Braconidae) of the larval stages of the tobacco budworm Heliothis virescens (Fabricius) (Lepidoptera, Noctuidae) injects the egg, the venom, the calyx fluid, which includes a Polydnavirus (T. nigriceps BracoVirus: TnBV) and the Ovarian Proteins (OPs) into the host body during oviposition. The host metabolism and immune system are disrupted prematurely shortly after parasitization by the combined action of the TnBV, venom, and OPs. OPs are involved in the early suppression of host immune response, before TnBV infects and expresses its genes in the host tissues. In this work, we evaluated the effect of HPLC fractions deriving from in toto OPs. Two fractions caused a reduction in hemocyte viability and were subsequently tested to detect changes in hemocyte morphology and functionality. The two fractions provoked severe oxidative stress and actin cytoskeleton disruption, which might explain the high rate of hemocyte mortality, loss of hemocyte functioning, and hence the host’s reduced hemocyte encapsulation ability. Moreover, through a transcriptome and proteomic approach we identify the proteins of the two fractions: eight proteins were identified that might be involved in the observed host hemocyte changes. Our findings will contribute to a better understanding of the secreted ovarian components and their role in parasitoid wasp strategy for evading host immune responses.

Evaluation of nuclear PGAM2 value in hepatocellular carcinoma prognosis

Phosphoglycerate mutase (PGAM) is a critical enzyme in glycolysis. PGAM2 is abundant in several types of tissues and malignant tumours. However, there is limited information regarding their clinicopathological significance in dysplastic nodules and hepatocellular carcinoma (HCC). This study aims to investigate the prognostic value of PGAM2 as a new biomarker for HCC. The PGAM2 expression level was evaluated by immunohistochemistry in liver cirrhosis (n = 10), low-grade dysplastic nodules (n = 15), high-grade dysplastic nodules (n = 15) and HCCs (n = 20) and 178 pairs of HCC and adjacent peritumoral liver tissues. We selected X-tile software for counting cut-point based on the outcomes for prognosis analysis, and used Kaplan-Meier analysis and Cox regression analysis can assess the prognosis of clinicopathologic parameters. Nuclear PGAM2 was significantly overexpressed in peritumoral liver tissues compared with HCC tissues (P = 0.0010). Kaplan-Meier analyses of 178 HCC samples revealed that nuclear PGAM2's high expression level, but not cytoplasmic PGAM2, was significantly related to good overall survival rate (OS). In addition, univariate and multivariate Cox analyses indicated nuclear PGAM2 expression could be regarded as valuable predictors for OS in HCC. PGAM2 was highly expressed in HCC tissues than liver cirrhosis tissues, and nuclear PGAM2's high expression might demonstrate HCC patients have poor postoperative results. Thus, nuclear PGAM2 can be regarded as valuable predictors for OS in HCC patients after surgery.

Phosphoglycerate mutase 2 is elevated in serum of patients with heart failure and correlates with the disease severity and patient's prognosis

Background

Heart failure (HF) is a serious and advanced stage of various cardiac diseases with high mortality and rehospitalization rates. Phosphoglycerate mutase 2 (PGAM2) overexpression was identified in the serum of patients with HF.

Material/methods

One hundred and fifty-three cases of HF were included in the present work. According to New York Heart Association (NYHA) classification, 22 were grade II, 84 were grade III, and 47 were grade IV. Serum PGAM2, NT-proBNP, B-type natriuretic peptide (BNP), troponin T (TNT), and Cys-C of HF patients were detected using ELISA assay. Left ventricular ejection fraction, left ventricular end-diastolic inner diameter, and left atrium (LA) inner diameter of the included cases were also detected by the cardiac color Doppler.

Results

The number of patients with atrial fibrillation was significantly higher in NYHA IV group than in groups II and III with statistical difference (p < 0.05). The serum PGAM2, NT-proBNP, and Cys-C were significantly higher in NYHA IV group than in NYHA II and NYHA III groups (p _all < 0.05). NT-proBNP had the highest prediction efficacy of HF severity and PGAM2 was also a potential biomarker for HF severity evaluation with relatively high sensitivity, specificity, and area under the ROC. The overall survival among NYHA II, III, and IV groups were statistically different (p = 0.04) with the median survival time of 25 months for NYHA III and IV groups.

Conclusion

PGAM2 is a new promising biomarker for evaluation of the severity of HF. Combination detection using multiple serum factors such as PGAM2, NT-proBNP, BNP, TNT, and Cys-C can improve the HF severity differential diagnosis performance.

The aging mouse lens transcriptome

Age is a major risk factor for cataract (ARC). However, the influence of aging on the lens transcriptome is under studied. Lens epithelial (LEC) and fiber cells (LFC) were isolated from young (3 month old) and aged (24 month old) C57BL/6J mice, and the transcriptome elucidated via RNAseq. EdgeR estimated differential gene expression in pairwise contrasts, and Advaita's Ipathway guide and custom R scripts were used to evaluate the potential biological significance of differentially expressed genes (DEGs). This analysis revealed age-dependent decreases in lens differentiation marker expression in both LECs and LFCs, with gamma crystallin transcripts downregulating nearly 50 fold in aged LFCs. The expression of the transcription factors Hsf4 and Maf, which are known to activate lens fiber cell preferred genes, are downregulated, while FoxE3, which represses gamma crystallin expression, is upregulated in aged fibers. Aged LECs upregulate genes controlling the immune response, complement pathways, and cellular stress responses, including glutathione peroxidase 3 (Gpx3). Aged LFCs exhibit broad changes in the expression of genes regulating cell communication, and upregulate genes involved in antigen processing/presentation and cholesterol metabolism, while changes in the expression of mitochondrial respiratory chain genes are consistent with mitochondrial stress, including upregulation of NDufa4l2, which encodes an alternate electron transport chain protein. However, age did not profoundly affect the response of LECs to injury as both young and aged LECs upregulate inflammatory gene signatures at 24 h post injury to similar extents. These RNAseq profiles provide a rich data set that can be mined to understand the genetic regulation of lens aging and how this impinges on the pathophysiology of age related cataract.

Characterization of genetically modified mice for phosphoglycerate mutase, a vitally-essential enzyme in glycolysis

Glycolytic metabolism is closely involved in physiological homeostasis and pathophysiological states. Among glycolytic enzymes, phosphoglycerate mutase (PGAM) has been reported to exert certain physiological role in vitro, whereas its impact on glucose metabolism in vivo remains unclear. Here, we report the characterization of Pgam1 knockout mice. We observed that homozygous knockout mice of Pgam1 were embryonic lethal. Although we previously reported that both PGAM-1 and -2 affect global glycolytic profile of cancers in vitro, in vivo glucose parameters were less affected both in the heterozygous knockout of Pgam1 and in Pgam2 transgenic mice. Thus, the impact of PGAM on in vivo glucose metabolism is rather complex than expected before.

Adriamycin inhibits glycolysis through downregulation of key enzymes in Saccharomyces cerevisiae

Adriamycin is a widely used drug for the treatment of various types of cancers, but its clinical application is limited because of irreversible dilated cardiomyopathy. The incidence of cardiomyopathy is a consequence of disrupted energy production, which could be related to the defects in glycogen, lipid and mucopolysaccharide metabolism. We explored the effect of Adriamycin on enzymes involved in glycolysis and apoptotic genes through molecular docking. We used Saccharomyces cerevisiae as model organism and studied the effect of Adriamycin on selected enzymes involved in glycolysis. The docking studies revealed that Adriamycin interacts with phosphofructokinase and enolase in an efficient manner. In phosphofructokinase, Adriamycin binds at the active site and with enolase the drug interacts at the cofactor-binding site (Mg²⁺) which might impair the activity of the enzyme. Gene expression studies revealed that Adriamycin causes the dysregulation of glycolysis through dysregulation of hexokinase, phosphoglycerate mutase, enolase and downregulation of pyruvate kinase. The drug shows a biphasic effect on the expression of genes enolase and pyruvate kinase. The impairment in glycolysis might reduce the ATP synthesis, and the cells might be deprived of energy. The condition is further worsened by elevated ROS levels triggering the cell to undergo apoptosis evidenced by downregulation of SOD and upregulation of BAX and caspase. In conclusion, our study reveals that Adriamycin impairs glycolysis and cause cell to undergo apoptosis due to oxidative stress in yeast cells.

Persistent or Transient Human β Cell Dysfunction Induced by Metabolic Stress: Specific Signatures and Shared Gene Expression with Type 2 Diabetes

Pancreatic β cell failure is key to type 2 diabetes (T2D) onset and progression. Here, we assess whether human β cell dysfunction induced by metabolic stress is reversible, evaluate the molecular pathways underlying persistent or transient damage, and explore the relationships with T2D islet traits. Twenty-six islet preparations are exposed to several lipotoxic/glucotoxic conditions, some of which impair insulin release, depending on stressor type, concentration, and combination. The reversal of dysfunction occurs after washout for some, although not all, of the lipoglucotoxic insults. Islet transcriptomes assessed by RNA sequencing and expression quantitative trait loci (eQTL) analysis identify specific pathways underlying β cell failure and recovery. Comparison of a large number of human T2D islet transcriptomes with those of persistent or reversible β cell lipoglucotoxicity show shared gene expression signatures. The identification of mechanisms associated with human β cell dysfunction and recovery and their overlap with T2D islet traits provide insights into T2D pathogenesis, fostering the development of improved β cell-targeted therapeutic strategies.

Phosphoglycerate Mutase Cooperates with Chk1 Kinase to Regulate Glycolysis

Dysregulated glycolysis, including the cancerous Warburg effect, is closely involved in pathological mechanisms of diseased states. Among glycolytic enzymes, phosphoglycerate mutase (PGAM) has been known to exert certain physiological impact in vitro, whereas its regulatory role on glycolysis remains unclear. Here, we identified that PGAM plays a key role in regulating glycolysis in cancer cells but not in standard cells. Cancer-prone phenotype by PGAM overexpression in vivo was associated with upregulated glycolytic features. PGAM interacts and cooperates with Chk1 to regulate the enhanced glycolysis in cancer cells, especially under oncogenic Ras expressing conditions. Genetic or chemical interference of the PGAM-Chk1 interaction, with intact PGAM activity, abrogated the maintenance of cancerous enhanced glycolysis. Thus, the nonenzymatic function of PGAM is essential for the Warburg effect that accompanies cancerous proliferation.

A novel transplantable model of lung cancer-associated tissue loss and disrupted muscle regeneration

BACKGROUND

Cancer-associated muscle wasting (CAW), a symptom of cancer cachexia, is associated with approximately 20% of lung cancer deaths and remains poorly characterized on a mechanistic level. Current animal models for lung cancer-associated cachexia are limited in that they (1) primarily employ flank transplantation methods, (2) have short survival times not reflective of the patient condition, and (3) are typically performed in young mice not representative of mean patient age. This study investigates a new model for lung cancer-associated cachexia that can address these issues and also implicates muscle regeneration as a contributor to CAW.

METHODS

We used tail vein injection as a method to introduce tumor cells that seed primarily in the lungs of mice. Body composition of tumor-bearing mice was longitudinally tracked using NMR-based, echo magnetic resonance imaging (echoMRI). These data were combined with histological and molecular assessments of skeletal muscle to provide a complete analysis of muscle wasting.

RESULTS

In this new lung CAW model, we observed (1) progressive loss in whole body weight, (2) progressive loss of lean and fat mass, (3) a circulating cytokine/inflammatory profile similar to that seen in other models of CAW, (4) histological changes associated with muscle wasting, and (5) molecular changes in muscle that implicate suppression of muscle repair/regeneration. Finally, we show that survival can be extended without lessening CAW by titrating injected cell number.

CONCLUSIONS

Overall, this study describes a new model of CAW that could be useful for further studies of lung cancer-associated wasting and accompanying changes in the regenerative capacity of muscle. Additionally, this model addresses many recent concerns with existing models such as immunocompetence, tumor location, and survival time.

Analysis of Cardiac Metabolic Remodeling in Heart Failure Using Nuclear Medicine and Its Application: Japanese Society of Nuclear Cardiology Award

Heart failure is associated with a significant change in the energy metabolism of the heart. We aimed to elucidate the altered energetics during the progression of heart failure. We used radioactive metabolic tracers to assess the substrate uptake. In a rat model of heart failure, the glucose uptake increased significantly at the stage of left ventricular hypertrophy, whereas the uptake of fatty acids decreased at the stage of heart failure, with decreased energy reserve during the transition of cardiac hypertrophy to failure. Metabolic modulator which enhances glucose oxidation ameliorated the decrease in cardiac function. We also validated the close correlation with mitochondrial membrane potentials and ^99mtechnetium sestamibi (^99mTc-MIBI) in vivo and at the organ level. The retention of ^99mTc-MIBI signals was correlated with the severity of heart failure. Nuclear medicine is a powerful tool to understand the mechanism of cardiac remodeling in heart failure.

Microarray and metabolome analysis of hepatic response to fasting and subsequent refeeding in zebrafish (Danio rerio)

Background

Compensatory growth refers to the phenomenon in which organisms grow faster after the improvement of an adverse environment and is thought to be an adaptive evolution to cope with the alleviation of the hostile environment. Many fish have the capacity for compensatory growth, but the underlying cellular mechanisms remain unclear. In the present study, microarray and nontargeted metabolomics were performed to characterize the transcriptome and metabolome of zebrafish liver during compensatory growth.

Results

Zebrafish could regain the weight they lost during 3 weeks of fasting and reach a final weight similar to that of fish fed ad libitum when refed for 15 days. When refeeding for 3 days, the liver displayed hyperplasia accompanied with decreased triglyceride contents and increased glycogen contents. The microarray results showed that when food was resupplied for 3 days, the liver TCA cycle (Tricarboxylic acid cycle) and oxidative phosphorylation processes were upregulated, while DNA replication and repair, as well as proteasome assembly were also activated. Integration of transcriptome and metabolome data highlighted transcriptionally driven alterations in metabolism during compensatory growth, such as altered glycolysis and lipid metabolism activities. The metabolome data also implied the participation of amino acid metabolism during compensatory growth in zebrafish liver.

Conclusion

Our study provides a global resource for metabolic adaptations and their transcriptional regulation during refeeding in zebrafish liver. This study represents a first step towards understanding of the impact of metabolism on compensatory growth and will potentially aid in understanding the molecular mechanism associated with compensatory growth.

The regulation of TORC1 pathway by the yeast chaperones Hsp31 is mediated by SFP1 and affects proteasomal activity

The Saccharomyces cerevisiae heat shock proteins Hsp31-34 are members of DJ-1/ThiJ/Pfpl superfamily that includes human DJ-1 (Park7), a protein involved in heritable Parkinsonism. Although, homologs of these proteins can be found in most organisms their functions are unclear. We have carried out a quantitative proteomics analysis of yeast cells devoid of the whole set of Hsp31 family of proteins, as a model of Parkinson Disease (PD), under conditions of glucose availability and starvation. The protein profile indicates a constitutive activation of the enzyme TORC1 that makes the cells more sensitive to stress conditions. TORC1 activation prevents the cells from diauxic shift and entry into the stationary phase inducing cell death. Sfp1 stays at the helm among the several transcription factors governing the cell adaptation to Hsp31-34 deficiency. We show that Sfp1 remains mainly in the nucleus likely releasing TORC1 from inhibition by cytosolic Sfp1. Impairment of glycolysis leads to increased levels of methylglyoxal and accumulation of glycated proteins. We also show an increase in proteasome subunits in the Hsp31-34 mutant, under the control of Rpn4 transcription factor. This increase is abnormally accompanied by a decrease in proteasomal activity which could lead to accumulation of aberrant proteins and contributing to cell death.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

The metabolic profile of a rat model of chronic kidney disease

Background

The kidney is always subjected to high metabolic demand. The aim of this study was to characterize metabolic profiles of a rat model of chronic kidney disease (CKD) with cardiorenal syndrome (CRS) induced by prolonged hypertension.

Methods

We used inbred male Dahl salt-sensitive (DS) rats fed an 8% NaCl diet from six weeks of age (high-salt; HS group) or a 0.3% NaCl diet as controls (low-salt; LS group). We analyzed function, pathology, metabolome, and the gene expression related to energy metabolism of the kidney.

Results

DS rats with a high-salt diet showed hypertension at 11 weeks of age and elevated serum levels of creatinine and blood urea nitrogen with heart failure at 21 weeks of age. The fibrotic area in the kidneys increased at 21 weeks of age. In addition, gene expression related to mitochondrial function was largely decreased. The levels of citrate and isocitrate increased and the gene expression of alpha-ketoglutaratedehydrogenase and succinyl-CoA synthetase decreased; these are enzymes that metabolize citrate and isocitrate, respectively. In addition, the levels of succinate and acetyl Co-A, both of which are metabolites of the tricarboxylic acid (TCA) cycle, decreased.

Conclusions

DS rats fed a high-salt diet were deemed a suitable model of CKD with CRS. Gene expression and metabolites related to energy metabolism and mitochondria in the kidney significantly changed in DS rats with hypertension in accordance with the progression of renal injury.

Bioenergetic Impairment in Congenital Muscular Dystrophy Type 1A and Leigh Syndrome Muscle Cells

Skeletal muscle has high energy requirement and alterations in metabolism are associated with pathological conditions causing muscle wasting and impaired regeneration. Congenital muscular dystrophy type 1A (MDC1A) is a severe muscle disorder caused by mutations in the LAMA2 gene. Leigh syndrome (LS) is a neurometabolic disease caused by mutations in genes related to mitochondrial function. Skeletal muscle is severely affected in both diseases and a common feature is muscle weakness that leads to hypotonia and respiratory problems. Here, we have investigated the bioenergetic profile in myogenic cells from MDC1A and LS patients. We found dysregulated expression of genes related to energy production, apoptosis and proteasome in myoblasts and myotubes. Moreover, impaired mitochondrial function and a compensatory upregulation of glycolysis were observed when monitored in real-time. Also, alterations in cell cycle populations in myoblasts and enhanced caspase-3 activity in myotubes were observed. Thus, we have for the first time demonstrated an impairment of the bioenergetic status in human MDC1A and LS muscle cells, which could contribute to cell cycle disturbance and increased apoptosis. Our findings suggest that skeletal muscle metabolism might be a promising pharmacological target in order to improve muscle function, energy efficiency and tissue maintenance of MDC1A and LS patients.

The c.-360 T>C mutation affects PGAM2 transcription activity and is linked with the water holding capacity of the longissimus lumborum muscle in pigs

The phosphoglycerate mutase 2 (PGAM2) gene encodes a key enzyme in the glycolytic process. This study examined a functional mutation in the PGAM2 gene and evaluated its relationship with water holding capacity (WHC). RT-qPCR analysis showed the PGAM2 mRNA level was significantly higher in the low-WHC group than in the high-WHC group (P<0.05). The c.-360 T>C mutation was identified through sequencing and found to have opposite allele distributions in the two groups. The allele was further genotyped in 170 Duroc×Large White×Yorkshire crossbred pigs using allele-specific PCR. The CC genotype was associated with lower WHC and higher PGAM2 mRNA levels, whereas the TT genotype corresponded to a higher WHC and lower PGAM2 mRNA levels (P<0.05). A luciferase activity assay also showed that the CC-genotype promoter had higher activity than the TT-genotype promoter (P<0.05). In conclusion, we discovered the c.-360 T>C mutation in the PGAM2 gene, which is a promising marker for improving pork WHC.

A data sheet for the simultaneous assessment of dual radioactive tracer uptake in the heart

The myocardium takes up two major substrates: glucose and fatty acids, and various methods have been used to evaluate this uptake. Despite extensive study of radiotracer uptake-based methods, however, an easily applicable datasheet has not previously been provided. In this manuscript, an example of a method involving an easily modified data sheet based on dual tracer methods is presented. This method, with its data sheet: •Is applicable to all radiotracers, regardless of decay time•Is useful, simple, and modifiable; and•Is applicable to small animal studies.

Branched-chain amino acids ameliorate heart failure with cardiac cachexia in rats

AIMS

Heart failure (HF) is associated with changes in energy metabolism of the heart, as well as in extra-cardiac organs such as the skeletal muscles. Cardiac cachexia is a common complication and is associated with poor prognosis. Branched-chain amino acids (BCAAs) reportedly improve sarcopenia and cancer cachexia. We tested the hypothesis that BCAA ameliorates HF with cardiac cachexia.

MAIN METHODS

We used Dahl salt-sensitive (DS) rats fed a high-salt diet as a model of HF. DS rats fed a low-salt diet were used as a control. BCAA were administered in drinking water from 11weeks of age, when cardiac hypertrophy was established but the cardiac function was preserved. Survival and the cardiac function were monitored, and animals were sacrificed at 21weeks of age and analyzed.

KEY FINDINGS

In HF rats, BCAA treatment decreased the heart rate, preserved the cardiac function, and prolonged survival. BCAA also prevented body weight loss, associated with preservation of the skeletal muscle weight. Moreover, gene expression related to mitochondrial biogenesis and function was increased with BCAA in skeletal muscles.

SIGNIFICANCE

BCAA preserved the body weight and cardiac function and prolonged survival in HF rats. The expression of genes involved in mitochondrial biogenesis and function in skeletal muscles was increased by BCAA.

Dysregulated glycolysis as an oncogenic event

Enhanced glycolysis in cancer, called the Warburg effect, is a well-known feature of cancer metabolism. Recent advances revealed that the Warburg effect is coupled to many other cancer properties, including adaptation to hypoxia and low nutrients, immortalisation, resistance to oxidative stress and apoptotic stimuli, and elevated biomass synthesis. These linkages are mediated by various oncogenic molecules and signals, such as c-Myc, p53, and the insulin/Ras pathway. Furthermore, several regulators of glycolysis have been recently identified as oncogene candidates, including the hypoxia-inducible factor pathway, sirtuins, adenosine monophosphate-activated kinase, glycolytic pyruvate kinase M2, phosphoglycerate mutase, and oncometabolites. The interplay between glycolysis and oncogenic events will be the focus of this review.

Measurement of technetium-99m sestamibi signals in rats administered a mitochondrial uncoupler and in a rat model of heart failure

Background

Many methods have been used to assess mitochondrial function. Technetium-99m sestamibi (^99mTc-MIBI), a lipophilic cation, is rapidly incorporated into myocardial cells by diffusion and mainly localizes to the mitochondria. The purpose of this study was to investigate whether measurement of ^99mTc-MIBI signals in animal models could be used as a tool to quantify mitochondrial membrane potential at the organ level.

Methods and Results

We analyzed ^99mTc-MIBI signals in Sprague-Dawley (SD) rat hearts perfused with carbonyl cyanide m-chlorophenylhydrazone (CCCP), a mitochondrial uncoupler known to reduce the mitochondrial membrane potential. ^99mTc-MIBI signals could be used to detect changes in the mitochondrial membrane potential with sensitivity comparable to that obtained by two-photon laser microscopy with the cationic probe tetramethylrhodamine ethyl ester (TMRE). We also measured ^99mTc-MIBI signals in the hearts of SD rats administered CCCP (4 mg/kg intraperitoneally) or vehicle. ^99mTc-MIBI signals decreased in rat hearts administered CCCP, and the ATP content, as measured by ³¹P magnetic resonance spectroscopy, decreased simultaneously. Next, we administered ^99mTc-MIBI to Dahl salt-sensitive rats fed a high-salt diet, which leads to hypertension and heart failure. The ^99mTc-MIBI signal per heart tissue weight was inversely correlated with heart weight, cardiac function, and the expression of atrial natriuretic factor, a marker of heart failure, and positively correlated with the accumulation of labeled fatty acid analog. The ^99mTc-MIBI signal per liver tissue weight was lower than that per heart tissue weight.

Conclusion

Measurement of ^99mTc-MIBI signals can be an effective tool for semiquantitative investigation of cardiac mitochondrial membrane potential in the SD rat model by using a chemical to decrease the mitochondrial membrane potential. The ^99mTc-MIBI signal per heart tissue weight was inversely correlated with the severity of heart failure in the Dahl rat model.