title: Mice over-expressing the myocardial creatine transporter develop progressive heart failure and show decreased glycolytic capacity.
abstract: The metabolic phenotype of the failing heart includes a decrease in phosphocreatine and total creatine concentration [Cr], potentially contributing to contractile dysfunction. Surprisingly, in 32- week-old mice over-expressing the myocardial creatine transporter (CrT-OE), we previously demonstrated that elevated [Cr] correlates with left ventricular (LV) hypertrophy and failure. The aim of this study was to determine the temporal relationship between elevated [Cr] and the onset of cardiac dysfunction and to screen for potential molecular mechanisms. CrT-OE mice were compared with wild-type (WT) littermate controls longitudinally using cine-MRI to measure cardiac function and single-voxel (1)H-MRS to measure [Cr] in vivo at 6, 16, 32, and 52 weeks of age. CrT-OE mice had elevated [Cr] at 6 weeks (mean 1.9-fold), which remained constant throughout life. Despite this increased [Cr], LV dysfunction was not apparent until 16 weeks and became more pronounced with age. Additionally, LV tissue from 12 to 14 week old CrT-OE mice was compared to WT using 2D difference in-gel electrophoresis (DIGE). These analyses detected a majority of the heart's metabolic enzymes and identified seven proteins that were differentially expressed between groups. The most pronounced protein changes were related to energy metabolism: alpha- and beta-enolase were selectively decreased (p<0.05), while the remaining enzymes of glycolysis were unchanged. Consistent with a decrease in enolase content, its activity was significantly lower in CrT-OE hearts (in WT, 0.59+/-0.02 micromol ATP produced/microg protein/min; CrT-OE, 0.31+/-0.06; p<0.01). Additionally, anaerobic lactate production was decreased in CrT-OE mice (in WT, 102+/-3 micromol/g wet myocardium; CrT-OE, 78+/-13; p=0.02), consistent with decreased glycolytic capacity. Finally, we found that enolase may be regulated by increased expression of the beta-enolase repressor transcription factor, which was significantly increased in CrT-OE hearts. This study demonstrates that chronically increased myocardial [Cr] in the CrT-OE model leads to the development of progressive hypertrophy and heart failure, which may be mediated by a compromise in glycolytic capacity at the level of enolase.
authors.affiliation: Department of Cardiovascular Medicine, University of Oxford, Henry Wellcome Building of Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN, UK.
authors.forename: Darci
authors.initials: D
authors.lastname: Phillips
authors.forename: Michiel
authors.initials: M
authors.lastname: Ten Hove
authors.forename: Jurgen E
authors.initials: JE
authors.lastname: Schneider
authors.forename: Colin O
authors.initials: CO
authors.lastname: Wu
authors.forename: Liam
authors.initials: L
authors.lastname: Sebag-Montefiore
authors.forename: Angel M
authors.initials: AM
authors.lastname: Aponte
authors.forename: Craig A
authors.initials: CA
authors.lastname: Lygate
authors.forename: Julie
authors.initials: J
authors.lastname: Wallis
authors.forename: Kieran
authors.initials: K
authors.lastname: Clarke
authors.forename: Hugh
authors.initials: H
authors.lastname: Watkins
authors.forename: Robert S
authors.initials: RS
authors.lastname: Balaban
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
mesh_terms: D000818:Animals; D001011:Aorta / Q000473:pathology; D006332:Cardiomegaly / Q000473:pathology; D003401:Creatine / Q000097:blood / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006019:Glycolysis; D006333:Heart Failure / Q000378:metabolism*; D006352:Heart Ventricles / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000378:metabolism*; D010725:Phosphocreatine / Q000737:chemistry; D010751:Phosphopyruvate Hydratase / Q000096:biosynthesis
chemical_list: D026901:Membrane Transport Proteins; C080679:creatine transporter; D010725:Phosphocreatine; D010751:Phosphopyruvate Hydratase; D003401:Creatine