Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Más filtros

Banco de datos
Tipo del documento
País de afiliación
Intervalo de año de publicación
1.
FASEB J ; 30(8): 2684-97, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-27103577

RESUMEN

The role of peroxisome proliferator-activated receptor α (PPARα)-mediated metabolic remodeling in cardiac adaptation to hypoxia has yet to be defined. Here, mice were housed in hypoxia for 3 wk before in vivo contractile function was measured using cine MRI. In isolated, perfused hearts, energetics were measured using (31)P magnetic resonance spectroscopy (MRS), and glycolysis and fatty acid oxidation were measured using [(3)H] labeling. Compared with a normoxic, chow-fed control mouse heart, hypoxia decreased PPARα expression, fatty acid oxidation, and mitochondrial uncoupling protein 3 (UCP3) levels, while increasing glycolysis, all of which served to maintain normal ATP concentrations ([ATP]) 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] and contractile function decreased significantly. The adaptive metabolic changes caused by hypoxia in control mouse hearts were found to have occurred already in PPARα-deficient (PPARα(-/-)) mouse hearts and sustained function in hypoxia despite an inability for further metabolic remodeling. We conclude that decreased cardiac PPARα expression is essential for adaptive metabolic remodeling in hypoxia, but is prevented by dietary fat.-Cole, M. A., Abd Jamil, A. H., Heather, L. C., Murray, A. J., Sutton, E. R., Slingo, M., Sebag-Montefiore, L., Tan, S. C., Aksentijevic, D., Gildea, O. S., Stuckey, D. J., Yeoh, K. K., Carr, C. A., Evans, R. D., Aasum, E., Schofield, C. J., Ratcliffe, P. J., Neubauer, S., Robbins, P. A., Clarke, K. On the pivotal role of PPARα in adaptation of the heart to hypoxia and why fat in the diet increases hypoxic injury.


Asunto(s)
Adaptación Fisiológica , Grasas de la Dieta/efectos adversos , Corazón/efectos de los fármacos , Miocardio/metabolismo , Consumo de Oxígeno/fisiología , PPAR alfa/metabolismo , Alimentación Animal/análisis , Animales , Línea Celular , Grasas de la Dieta/administración & dosificación , Regulación de la Expresión Génica/fisiología , Corazón/fisiología , Masculino , Ratones , Miocitos Cardíacos/metabolismo , PPAR alfa/genética
2.
Circ Res ; 112(6): 945-55, 2013 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-23325497

RESUMEN

RATIONALE: Creatine is thought to be involved in the spatial and temporal buffering of ATP in energetic organs such as heart and skeletal muscle. Creatine depletion affects force generation during maximal stimulation, while reduced levels of myocardial creatine are a hallmark of the failing heart, leading to the widely held view that creatine is important at high workloads and under conditions of pathological stress. OBJECTIVE: We therefore hypothesised that the consequences of creatine-deficiency in mice would be impaired running capacity, and exacerbation of heart failure following myocardial infarction. METHODS AND RESULTS: Surprisingly, mice with whole-body creatine deficiency due to knockout of the biosynthetic enzyme (guanidinoacetate N-methyltransferase [GAMT]) voluntarily ran just as fast and as far as controls (>10 km/night) and performed the same level of work when tested to exhaustion on a treadmill. Furthermore, survival following myocardial infarction was not altered, nor was subsequent left ventricular (LV) remodelling and development of chronic heart failure exacerbated, as measured by 3D-echocardiography and invasive hemodynamics. These findings could not be accounted for by compensatory adaptations, with no differences detected between WT and GAMT(-/-) proteomes. Alternative phosphotransfer mechanisms were explored; adenylate kinase activity was unaltered, and although GAMT(-/-) hearts accumulated the creatine precursor guanidinoacetate, this had negligible energy-transfer activity, while mitochondria retained near normal function. CONCLUSIONS: Creatine-deficient mice show unaltered maximal exercise capacity and response to chronic myocardial infarction, and no obvious metabolic adaptations. Our results question the paradigm that creatine is essential for high workload and chronic stress responses in heart and skeletal muscle.


Asunto(s)
Creatina/deficiencia , Tolerancia al Ejercicio/fisiología , Infarto del Miocardio/fisiopatología , Esfuerzo Físico/fisiología , Adenilato Quinasa/metabolismo , Animales , Femenino , Glicina/análogos & derivados , Glicina/metabolismo , Guanidinoacetato N-Metiltransferasa/genética , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/metabolismo , Insuficiencia Cardíaca/fisiopatología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias Cardíacas/fisiología , Infarto del Miocardio/complicaciones , Infarto del Miocardio/metabolismo , Consumo de Oxígeno/fisiología , Condicionamiento Físico Animal , Remodelación Ventricular/fisiología
3.
J Mol Cell Cardiol ; 75: 76-87, 2014 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-25066696

RESUMEN

UNLABELLED: Inhibition of malonyl-coenzyme A decarboxylase (MCD) shifts metabolism from fatty acid towards glucose oxidation, which has therapeutic potential for obesity and myocardial ischemic injury. However, ~40% of patients with MCD deficiency are diagnosed with cardiomyopathy during infancy. AIM: To clarify the link between MCD deficiency and cardiac dysfunction in early life and to determine the contributing systemic and cardiac metabolic perturbations. METHODS AND RESULTS: MCD knockout mice ((-/-)) exhibited non-Mendelian genotype ratios (31% fewer MCD(-/-)) with deaths clustered around weaning. Immediately prior to weaning (18days) MCD(-/-) mice had lower body weights, elevated body fat, hepatic steatosis and glycogen depletion compared to wild-type littermates. MCD(-/-) plasma was hyperketonemic, hyperlipidemic, had 60% lower lactate levels and markers of cellular damage were elevated. MCD(-/-) hearts exhibited hypertrophy, impaired ejection fraction and were energetically compromised (32% lower total adenine nucleotide pool). However differences between WT and MCD(-/-) converged with age, suggesting that, in surviving MCD(-/-) mice, early cardiac dysfunction resolves over time. These observations were corroborated by in silico modelling of cardiomyocyte metabolism, which indicated improvement of the MCD(-/-) metabolic phenotype and improved cardiac efficiency when switched from a high-fat diet (representative of suckling) to a standard post-weaning diet, independent of any developmental changes. CONCLUSIONS: MCD(-/-) mice consistently exhibited cardiac dysfunction and severe metabolic perturbations while on a high-fat, low carbohydrate diet of maternal milk and these gradually resolved post-weaning. This suggests that dysfunction is a common feature of MCD deficiency during early development, but that severity is dependent on composition of dietary substrates.


Asunto(s)
Carboxiliasas/deficiencia , Corazón/fisiopatología , Destete , Envejecimiento/patología , Animales , Simulación por Computador , Dieta Alta en Grasa , Femenino , Eliminación de Gen , Genotipo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Miocardio/metabolismo , Miocardio/patología , Fenotipo , Especificidad por Sustrato , Análisis de Supervivencia
4.
Am J Physiol Endocrinol Metab ; 305(2): E263-70, 2013 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-23715727

RESUMEN

Creatine is important for energy metabolism, yet excitable cells such as cardiomyocytes do not synthesize creatine and rely on uptake via a specific membrane creatine transporter (CrT; SLC6A8). This process is tightly controlled with downregulation of CrT upon continued exposure to high creatine via mechanisms that are poorly understood. Our aim was to identify candidate endogenous CrT inhibitors. In 3T3 cells overexpressing the CrT, creatine uptake plateaued at 3 h in response to 5 mM creatine but peaked 33% higher (P < 0.01) in the presence of cycloheximide, suggesting CrT regulation depends on new protein synthesis. Global gene expression analysis identified thioredoxin-interacting protein (Txnip) as the only significantly upregulated gene (by 46%) under these conditions (P = 0.036), subsequently verified independently at mRNA and protein levels. There was no change in Txnip expression with exposure to 5 mM taurine, confirming a specific response to creatine rather than osmotic stress. Small-interfering RNA against Txnip prevented Txnip upregulation in response to high creatine, maintained normal levels of creatine uptake, and prevented downregulation of CrT mRNA. These findings were relevant to the in vivo heart since creatine-deficient mice showed 39.71% lower levels of Txnip mRNA, whereas mice overexpressing the CrT had 57.6% higher Txnip mRNA levels and 28.7% higher protein expression compared with wild types (mean myocardial creatine concentration 124 and 74 nmol/mg protein, respectively). In conclusion, we have identified Txnip as a novel negative regulator of creatine levels in vitro and in vivo, responsible for mediating substrate feedback inhibition and a potential target for modulating creatine homeostasis.


Asunto(s)
Proteínas Portadoras/fisiología , Creatina/metabolismo , Homeostasis/fisiología , Tiorredoxinas/fisiología , Células 3T3 , Animales , Western Blotting , Cromatografía Líquida de Alta Presión , Cicloheximida/farmacología , Expresión Génica/efectos de los fármacos , Masculino , Proteínas de Transporte de Membrana/metabolismo , Ratones , Ratones Transgénicos , Análisis por Micromatrices , Miocardio/metabolismo , Inhibidores de la Síntesis de la Proteína/farmacología , ARN Mensajero/biosíntesis , ARN Mensajero/genética , ARN Interferente Pequeño/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa
5.
Basic Res Cardiol ; 107(5): 276, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22760499

RESUMEN

The creatine kinase (CK) energy transport and buffering system supports cardiac function at times of high demand and is impaired in the failing heart. Mice deficient in muscle- and mitochondrial-CK (M/Mt-CK(-/-)) have previously been described, but exhibit an unexpectedly mild phenotype of compensated left ventricular (LV) hypertrophy. We hypothesised that heart failure would develop with age and performed echocardiography and LV haemodynamics at 1 year. Since all previous studies have utilised mice with a mixed genetic background, we backcrossed for >10 generations on to C57BL/6, and repeated the in vivo investigations. Male M/Mt-CK(-/-) mice on the mixed genetic background developed congestive heart failure as evidenced by significantly elevated end-diastolic pressure, impaired contractility, LV dilatation, hypertrophy and pulmonary congestion. Female mice were less severely affected, only showing trends for these parameters. After backcrossing, M/Mt-CK(-/-) mice had LV dysfunction consisting of impaired isovolumetric pressure changes and reduced contractile reserve, but did not develop congestive heart failure. Body weight was lower in knockout mice as a consequence of reduced total body fat. LV weight was not significantly elevated in relation to other internal organs and gene expression of LVH markers was normal, suggesting an absence of hypertrophy. In conclusion, the consequences of CK deficiency are highly dependent on genetic modifiers, gender and age. However, the observation that a primary defect in CK can, under the right conditions, result in heart failure suggests that impaired CK activity in the failing heart could contribute to disease progression.


Asunto(s)
Creatina Quinasa/deficiencia , Insuficiencia Cardíaca/etiología , Factores de Edad , Animales , Composición Corporal , Enfermedad Crónica , Femenino , Insuficiencia Cardíaca/genética , Hemodinámica , Hipertrofia Ventricular Izquierda/etiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fenotipo , Factores Sexuales
6.
J Mol Cell Cardiol ; 48(4): 582-90, 2010 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-19913546

RESUMEN

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.


Asunto(s)
Creatina/metabolismo , Insuficiencia Cardíaca/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Miocardio/metabolismo , Animales , Aorta/patología , Cardiomegalia/patología , Creatina/sangre , Electroforesis en Gel Bidimensional , Femenino , Glucólisis , Ventrículos Cardíacos/patología , Imagen por Resonancia Magnética/métodos , Ratones , Ratones Endogámicos C57BL , Fosfocreatina/química , Fosfopiruvato Hidratasa/biosíntesis
7.
BMC Dev Biol ; 10: 70, 2010 Jun 22.
Artículo en Inglés | MEDLINE | ID: mdl-20569423

RESUMEN

BACKGROUND: It is well established that the immature myocardium preferentially utilises non-oxidative energy-generating pathways. It exhibits low energy-transfer capacity via the creatine kinase (CK) shuttle, reflected in phosphocreatine (PCr), total creatine and CK levels that are much lower than those of adult myocardium. The mechanisms leading to gradually increasing energy transfer capacity during maturation are poorly understood. Creatine is not synthesised in the heart, but taken up exclusively by the action of the creatine transporter protein (CrT). To determine whether this transporter is ontogenically regulated, the present study serially examined CrT gene expression pattern, together with creatine uptake kinetics and resulting myocardial creatine levels, in rats over the first 80 days of age. RESULTS: Rats were studied during the late prenatal period (-2 days before birth) and 7, 13, 21, 33, 50 and 80 days after birth. Activity of cardiac citrate synthase, creatine kinase and its isoenzymes as well as lactate dehydrogenase (LDH) and its isoenzymes demonstrated the well-described shift from anaerobic towards aerobic metabolism. mRNA levels of CrT in the foetal rat hearts, as determined by real-time PCR, were about 30% of the mRNA levels in the adult rat heart and gradually increased during development. Creatine uptake in isolated perfused rat hearts increased significantly from 3.0 nmol/min/gww at 13 days old to 4.9 nmol/min/gww in 80 day old rats. Accordingly, total creatine content in hearts, measured by HPLC, increased steadily during maturation (30 nmol/mg protein (-2 days) vs 87 nmol/mg protein (80 days)), and correlated closely with CrT gene expression. CONCLUSIONS: The maturation-dependant alterations of CK and LDH isoenzyme activities and of mitochondrial oxidative capacity were paralleled by a progressive increase of CrT expression, creatine uptake kinetics and creatine content in the heart.


Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Corazón/embriología , L-Lactato Deshidrogenasa/metabolismo , Proteínas de Transporte de Membrana/genética , Miocardio/metabolismo , Aerobiosis , Anaerobiosis , Animales , Creatina Quinasa/metabolismo , Creatinina/sangre , Técnicas In Vitro , Isoenzimas/metabolismo , Mitocondrias/metabolismo , Miocardio/enzimología , ARN Mensajero/genética , Ratas , Ratas Wistar , Transcripción Genética
8.
J Mol Cell Cardiol ; 46(1): 93-9, 2009 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-18948110

RESUMEN

UNLABELLED: Discrepant results for the phenotype of mitochondrial creatine kinase knockout mice (Mt-CK(-/-)) could be due to mixed genetic background and use of non-littermate controls. We therefore backcrossed with C57BL/6J for >8 generations, followed by extensive in vivo cardiac phenotyping. Echocardiography and in vivo LV haemodynamics were performed in independent cohorts at 20-40 weeks and 1 year. No significant differences were observed for ECG, LV volumes, pressures, and systolic or diastolic function compared to littermate controls. Furthermore, responses to dobutamine were not different, indicating preserved contractile reserve. Contrary to published reports using Mt-CK(-/-) on a mixed background, we observed normal LV weights even in year old mice, and gene expression of common hypertrophic markers were not elevated. However, previously undetected adaptations were observed: an increase in activity of the cytosolic MM-CK isoenzyme (+20% vs WT, P=0.0009), and of citrate synthase (+18% vs WT, P=0.0007), a marker for mitochondrial volume. In a 3-week voluntary wheel running protocol, Mt-CK(-/-) ran significantly less per day (P=0.009) and attained lower maximum speed compared to controls (P=0.0003), suggesting impaired skeletal muscle function. MM-CK isoenzyme activity was significantly elevated in soleus but not gastrocnemius muscle of KO mice, and citrate synthase activities were normal in both, suggesting compensatory mechanisms are incomplete in skeletal muscle. CONCLUSIONS: in contrast to previous reports using a mixed genetic background, Mt-CK(-/-) on a C57BL/6 background do not develop LV hypertrophy or dysfunction even up to 1 year, and this may be explained by a compensatory increase in MM-CK activity and mitochondrial volume.


Asunto(s)
Forma Mitocondrial de la Creatina-Quinasa/genética , Corazón/fisiología , Miocardio/metabolismo , Animales , Cardiomegalia , Ecocardiografía/métodos , Femenino , Insuficiencia Cardíaca , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Modelos Genéticos , Fenotipo , Disfunción Ventricular Izquierda/patología
9.
J Mol Cell Cardiol ; 45(3): 453-9, 2008 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-18602925

RESUMEN

Creatine plays an important role in energy metabolism in the heart. Cardiomyocytes accumulate creatine via a specific creatine transporter (CrT), the capacity of which is reduced in the failing heart, resulting in lower myocardial creatine concentration. Therefore, to gain insight into how the CrT is regulated, we studied two mouse models of severely altered myocardial creatine levels. Cardiac creatine uptake levels were measured in isolated hearts from creatine-free guanidinoacetate-N-methyl transferase knock out (GAMT(-/-)) mice and from mice overexpressing the myocardial CrT (CrT-OE) using (14)C-radiolabeled creatine. CrT mRNA levels were measured using real time RT-PCR and creatine levels with HPLC. Hearts from GAMT(-/-) mice showed a 7-fold increase in V(max) of creatine uptake and a 1.4-fold increase in CrT mRNA levels. The increase in Cr uptake and in CrT mRNA levels, however, was almost completely prevented when mice were fed a creatine supplemented diet, indicating that creatine uptake is subject to negative feedback regulation. Cardiac creatine uptake levels in CrT-OE mice were increased on average 2.7-fold, showing a considerable variation, in line with a similar variation in creatine content. Total CrT mRNA levels correlated well with myocardial creatine content (r=0.67; p<0.0001) but endogenous CrT mRNA levels did not correlate at all with myocardial creatine content (r=0.01; p=0.96). This study shows that creatine uptake can be massively upregulated in the heart, by almost an order of magnitude and that this upregulation is subject to feedback inhibition. In addition, our results strongly suggest that CrT activity is predominantly regulated by mechanisms other than alterations in gene expression.


Asunto(s)
Creatina/metabolismo , Miocardio/metabolismo , Animales , Transporte Biológico/fisiología , Creatina/genética , Femenino , Guanidinoacetato N-Metiltransferasa/deficiencia , Guanidinoacetato N-Metiltransferasa/genética , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Conejos
10.
J Mol Cell Cardiol ; 45(6): 754-60, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-18929569

RESUMEN

Patients with muscular dystrophy have abnormal cardiac function and decreased high-energy phosphate metabolism. Here, we have determined whether the 8 month old mdx mouse, an animal model of muscular dystrophy, also has abnormal cardiac function and energetics. In vivo cardiac MRI revealed 33% and 104% larger right ventricular end-diastolic and end-systolic volumes, respectively, and 17% lower right ventricular ejection fractions in mdx mice compared with controls. Evidence of left ventricular diastolic dysfunction included 18% lower peak filling rates in mdx mouse hearts. Abnormal cardiac function was accompanied by necrosis and lower citrate synthase activity in the mdx mouse heart, suggesting decreased mitochondrial content. Decreased mitochondrial numbers were associated with 38% lower phosphocreatine concentration, 22% lower total creatine, 36% higher cytosolic free ADP concentration and 1.3 kJ/mol lower free-energy available from ATP hydrolysis in whole isolated, perfused mdx mouse hearts than in controls. Transsarcolemmal creatine uptake was 12% lower in mdx mouse hearts. We conclude that the absence of dystrophin in adult mdx mouse heart, as in the heart of human patient, is associated with right ventricular dilatation, left ventricular diastolic dysfunction and abnormal energy metabolism.


Asunto(s)
Metabolismo Energético , Distrofias Musculares/metabolismo , Distrofias Musculares/patología , Distrofia Muscular Animal/metabolismo , Distrofia Muscular Animal/patología , Miocardio/metabolismo , Miocardio/patología , Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Citrato (si)-Sintasa/metabolismo , Hidrólisis , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Endogámicos mdx , Mitocondrias Cardíacas/metabolismo , Mitocondrias Cardíacas/patología , Distrofias Musculares/fisiopatología , Distrofia Muscular Animal/fisiopatología , Necrosis , Fosfocreatina/metabolismo , Sarcolema/metabolismo , Sarcolema/patología , Volumen Sistólico
11.
Circulation ; 112(20): 3131-9, 2005 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-16286605

RESUMEN

BACKGROUND: Heart failure is associated with deranged cardiac energy metabolism, including reductions of creatine and phosphocreatine. Interventions that increase myocardial high-energy phosphate stores have been proposed as a strategy for treatment of heart failure. Previously, it has not been possible to increase myocardial creatine and phosphocreatine concentrations to supranormal levels because they are subject to tight regulation by the sarcolemmal creatine transporter (CrT). METHODS AND RESULTS: We therefore created 2 transgenic mouse lines overexpressing the myocardial creatine transporter (CrT-OE). Compared with wild-type (WT) littermate controls, total creatine (by high-performance liquid chromatography) was increased in CrT-OE hearts (66+/-6 nmol/mg protein in WT versus 133+/-52 nmol/mg protein in CrT-OE). Phosphocreatine levels (by 31P magnetic resonance spectroscopy) were also increased but to a lesser extent. Surprisingly, CrT-OE mice developed left ventricular (LV) dilatation (LV end-diastolic volume: 21.5+/-4.3 microL in WT versus 33.1+/-9.6 microL in CrT-OE; P=0.002), substantial LV dysfunction (ejection fraction: 64+/-9% in WT versus 49+/-13% in CrT-OE; range, 22% to 70%; P=0.003), and LV hypertrophy (by 3-dimensional echocardiography and magnetic resonance imaging). Myocardial creatine content correlated closely with LV end-diastolic volume (r=0.51, P=0.02), ejection fraction (r=-0.74, P=0.0002), LV weight (r=0.59, P=0.006), LV end-diastolic pressure (r=0.52, P=0.02), and dP/dt(max) (r=-0.69, P=0.0008). Despite increased creatine and phosphocreatine levels, CrT-OE hearts showed energetic impairment, with increased free ADP concentrations and reduced free-energy change levels. CONCLUSIONS: Overexpression of the CrT leads to supranormal levels of myocardial creatine and phosphocreatine, but the heart is incapable of keeping the augmented creatine pool adequately phosphorylated, resulting in increased free ADP levels, LV hypertrophy, and dysfunction. Our data demonstrate that a disturbance of the CrT-mediated tight regulation of cardiac energy metabolism has deleterious functional consequences. These findings caution against the uncritical use of creatine as a therapeutic agent in heart disease.


Asunto(s)
Cardiomegalia/fisiopatología , Insuficiencia Cardíaca/fisiopatología , Proteínas de Transporte de Membrana/genética , Animales , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Ratones , Ratones Transgénicos , Sistemas de Lectura Abierta , Conejos , Sarcolema/fisiología
12.
Circulation ; 111(19): 2477-85, 2005 May 17.
Artículo en Inglés | MEDLINE | ID: mdl-15883212

RESUMEN

BACKGROUND: The role of the creatine kinase (CK)/phosphocreatine (PCr) energy buffer and transport system in heart remains unclear. Guanidinoacetate-N-methyltransferase-knockout (GAMT-/-) mice represent a new model of profoundly altered cardiac energetics, showing undetectable levels of PCr and creatine and accumulation of the precursor (phospho-)guanidinoacetate (P-GA). To characterize the role of a substantially impaired CK/PCr system in heart, we studied the cardiac phenotype of wild-type (WT) and GAMT-/- mice. METHODS AND RESULTS: GAMT-/- mice did not show cardiac hypertrophy (myocyte cross-sectional areas, hypertrophy markers atrial natriuretic factor and beta-myosin heavy chain). Systolic and diastolic function, measured invasively (left ventricular conductance catheter) and noninvasively (MRI), were similar for WT and GAMT-/- mice. However, during inotropic stimulation with dobutamine, preload-recruitable stroke work failed to reach maximal levels of performance in GAMT-/- hearts (101+/-8 mm Hg in WT versus 59+/-7 mm Hg in GAMT-/-; P<0.05). (31)P-MR spectroscopy experiments showed that during inotropic stimulation, isolated WT hearts utilized PCr, whereas isolated GAMT-/- hearts utilized P-GA. During ischemia/reperfusion, GAMT-/- hearts showed markedly impaired recovery of systolic (24% versus 53% rate pressure product recovery; P<0.05) and diastolic function (eg, left ventricular end-diastolic pressure 23+/-9 in WT and 51+/-5 mm Hg in GAMT-/- during reperfusion; P<0.05) and incomplete resynthesis of P-GA. CONCLUSIONS: GAMT-/- mice do not develop hypertrophy and show normal cardiac function at low workload, suggesting that a fully functional CK/PCr system is not essential under resting conditions. However, when acutely stressed by inotropic stimulation or ischemia/reperfusion, GAMT-/- mice exhibit a markedly abnormal phenotype, demonstrating that an intact, high-capacity CK/PCr system is required for situations of increased cardiac work or acute stress.


Asunto(s)
Metabolismo Energético/fisiología , Guanidinoacetato N-Metiltransferasa/deficiencia , Contracción Miocárdica , Daño por Reperfusión Miocárdica/etiología , Fosfocreatina/deficiencia , Animales , Cardiomegalia/etiología , Creatina Quinasa/fisiología , Susceptibilidad a Enfermedades , Guanidinoacetato N-Metiltransferasa/genética , Pruebas de Función Cardíaca , Hemodinámica , Ratones , Ratones Noqueados , Isquemia Miocárdica , Daño por Reperfusión Miocárdica/metabolismo , Fosfocreatina/fisiología , Estrés Fisiológico
13.
Diabetes ; 53(7): 1900-4, 2004 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-15220217

RESUMEN

Type II SH2 domain-containing inositol 5-phosphatase (INPPL1, or SHIP2) plays an important role in the control of insulin sensitivity. INPPL1 mutations affecting gene function have been found in rat models of type 2 diabetes and hypertension and in type 2 diabetic patients. We investigated the influence of nucleotide variation in INPPL1 on components of the metabolic syndrome. Following comprehensive resequencing of the gene, we genotyped 12 informative polymorphisms in 1,304 individuals from 424 British type 2 diabetes families that were characterized for several metabolic phenotypes. We have found highly significant associations of single nucleotide polymorphisms (SNPs) and haplotypes of INPPL1 with hypertension as well as with other components of the metabolic syndrome. In a cohort of 905 French type 2 diabetic patients, we found evidence of association of INPPL1 SNPs with the presence of hypertension. We conclude that INPPL1 variants may impact susceptibility to disease and/or to subphenotypes involved in the metabolic syndrome in some diabetic patients.


Asunto(s)
Síndrome Metabólico/fisiopatología , Monoéster Fosfórico Hidrolasas/genética , Polimorfismo Genético , Dominios Homologos src/genética , Anciano , Animales , Estudios de Cohortes , Diabetes Mellitus Tipo 2/genética , Femenino , Genotipo , Haplotipos , Humanos , Hipertensión/genética , Masculino , Síndrome Metabólico/genética , Persona de Mediana Edad , Datos de Secuencia Molecular , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatasas , Polimorfismo de Nucleótido Simple , Ratas
14.
PLoS One ; 8(6): e66461, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23823183

RESUMEN

BACKGROUND: Reduced levels of creatine and total adenine nucleotides (sum of ATP, ADP and AMP) are hallmarks of chronic heart failure and restoring these pools is predicted to be beneficial by maintaining the diseased heart in a more favourable energy state. Ribose supplementation is thought to support both salvage and re-synthesis of adenine nucleotides by bypassing the rate-limiting step. We therefore tested whether ribose would be beneficial in chronic heart failure in control mice and in mice with elevated myocardial creatine due to overexpression of the creatine transporter (CrT-OE). METHODS AND RESULTS: FOUR GROUPS WERE STUDIED: sham; myocardial infarction (MI); MI+ribose; MI+CrT-OE+ribose. In a pilot study, ribose given in drinking water was bioavailable, resulting in a two-fold increase in myocardial ribose-5-phosphate levels. However, 8 weeks post-surgery, total adenine nucleotide (TAN) pool was decreased to a similar amount (8-14%) in all infarcted groups irrespective of the treatment received. All infarcted groups also presented with a similar and substantial degree of left ventricular (LV) dysfunction (3-fold reduction in ejection fraction) and LV hypertrophy (32-47% increased mass). Ejection fraction closely correlated with infarct size independently of treatment (r(2) = 0.63, p<0.0001), but did not correlate with myocardial creatine or TAN levels. CONCLUSION: Elevating myocardial ribose and creatine levels failed to maintain TAN pool or improve post-infarction LV remodeling and function. This suggests that ribose is not rate-limiting for purine nucleotide biosynthesis in the chronically failing mouse heart and that alternative strategies to preserve TAN pool should be investigated.


Asunto(s)
Nucleótidos de Adenina/metabolismo , Creatinina/metabolismo , Insuficiencia Cardíaca/metabolismo , Miocardio/metabolismo , Ribosa/administración & dosificación , Animales , Insuficiencia Cardíaca/fisiopatología , Pruebas de Función Cardíaca , Ratones , Ratones Transgénicos , Proyectos Piloto
15.
Cardiovasc Res ; 96(3): 466-75, 2012 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-22915766

RESUMEN

AIMS: Increasing energy storage capacity by elevating creatine and phosphocreatine (PCr) levels to increase ATP availability is an attractive concept for protecting against ischaemia and heart failure. However, testing this hypothesis has not been possible since oral creatine supplementation is ineffectual at elevating myocardial creatine levels. We therefore used mice overexpressing creatine transporter in the heart (CrT-OE) to test for the first time whether elevated creatine is beneficial in clinically relevant disease models of heart failure and ischaemia/reperfusion (I/R) injury. METHODS AND RESULTS: CrT-OE mice were selected for left ventricular (LV) creatine 20-100% above wild-type values and subjected to acute and chronic coronary artery ligation. Increasing myocardial creatine up to 100% was not detrimental even in ageing CrT-OE. In chronic heart failure, creatine elevation was neither beneficial nor detrimental, with no effect on survival, LV remodelling or dysfunction. However, CrT-OE hearts were protected against I/R injury in vivo in a dose-dependent manner (average 27% less myocardial necrosis) and exhibited greatly improved functional recovery following ex vivo I/R (59% of baseline vs. 29%). Mechanisms contributing to ischaemic protection in CrT-OE hearts include elevated PCr and glycogen levels and improved energy reserve. Furthermore, creatine loading in HL-1 cells did not alter antioxidant defences, but delayed mitochondrial permeability transition pore opening in response to oxidative stress, suggesting an additional mechanism to prevent reperfusion injury. CONCLUSION: Elevation of myocardial creatine by 20-100% reduced myocardial stunning and I/R injury via pleiotropic mechanisms, suggesting CrT activation as a novel, potentially translatable target for cardiac protection from ischaemia.


Asunto(s)
Creatina/metabolismo , Insuficiencia Cardíaca/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Infarto del Miocardio/prevención & control , Daño por Reperfusión Miocárdica/prevención & control , Miocardio/metabolismo , Animales , Línea Celular , Modelos Animales de Enfermedad , Metabolismo Energético , Glucógeno/metabolismo , Insuficiencia Cardíaca/genética , Insuficiencia Cardíaca/patología , Insuficiencia Cardíaca/fisiopatología , Imagen por Resonancia Cinemagnética , Proteínas de Transporte de Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mitocondrias Cardíacas/metabolismo , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Poro de Transición de la Permeabilidad Mitocondrial , Infarto del Miocardio/genética , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Daño por Reperfusión Miocárdica/etiología , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/patología , Daño por Reperfusión Miocárdica/fisiopatología , Aturdimiento Miocárdico/metabolismo , Aturdimiento Miocárdico/patología , Aturdimiento Miocárdico/fisiopatología , Aturdimiento Miocárdico/prevención & control , Miocardio/patología , Necrosis , Estrés Oxidativo , Fosfocreatina/metabolismo , Factores de Tiempo , Regulación hacia Arriba , Función Ventricular Izquierda , Remodelación Ventricular
16.
Eur J Heart Fail ; 12(12): 1282-9, 2010 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-20940173

RESUMEN

AIMS: To measure the activity of the key phosphotransfer enzymes creatine kinase (CK), adenylate kinase (AK), and glycolytic enzymes in two common mouse models of chronic heart failure. METHODS AND RESULTS: C57BL/6 mice were subjected to transverse aortic constriction (TAC), myocardial infarction induced by coronary artery ligation (CAL), or sham operation. Activities of phosphotransfer enzymes CK, AK, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 3-phosphoglycerate kinase (PGK), and pyruvate kinase were assessed spectrophotometrically. Mice were characterized by echocardiography or magnetic resonance imaging 5- to 8-week post-surgery and selected for the presence of congestive heart failure. All mice had severe left ventricular hypertrophy, impaired systolic function and pulmonary congestion compared with sham controls. A significant decrease in myocardial CK and maximal CK reaction velocity was observed in both experimental models of heart failure. However, the activity of AK and its isoforms remained unchanged, despite a reduction in its protein expression. In contrast, the activities of glycolytic phosphotransfer mediators GAPDH and PGK were 19 and 12% higher in TAC, and 31 and 23% higher in CAL models, respectively. CONCLUSION: Chronic heart failure in the mouse is characterized by impaired CK function, unaltered AK, and increased activity of glycolytic phosphotransfer enzymes. This pattern of altered phosphotransfer activity was observed independent of the heart failure aetiology.


Asunto(s)
Adenilato Quinasa/metabolismo , Creatina Quinasa/metabolismo , Insuficiencia Cardíaca/enzimología , Transducción de Señal/fisiología , Animales , Western Blotting , Modelos Animales de Enfermedad , Insuficiencia Cardíaca/diagnóstico por imagen , Insuficiencia Cardíaca/metabolismo , Hemodinámica , Humanos , Hipertrofia Ventricular Izquierda/diagnóstico por imagen , Hipertrofia Ventricular Izquierda/enzimología , Hipertrofia Ventricular Izquierda/metabolismo , Ligadura , Masculino , Ratones , Ratones Endogámicos C57BL , Fosforilación , Fosfotransferasas/metabolismo , Estadística como Asunto , Ultrasonografía , Función Ventricular Izquierda
17.
J Mol Cell Cardiol ; 42(6): 1129-36, 2007 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-17481652

RESUMEN

Characteristic alterations of the creatine kinase (CK) system occur in heart failure and may contribute to contractile dysfunction. We examined two mouse models of chronic cardiac stress, transverse aortic constriction (TAC) and coronary artery ligation (CAL), and examined the relationship of CK system changes with hypertrophy and heart failure development. C57Bl/6 mice were subjected to TAC or sham surgery and sacrificed after 2-10 weeks according to echocardiographic criteria of myocardial hypertrophy and function to create four groups representing progressive dysfunction from normal, through compensated hypertrophy, to heart failure. Only mice with congestive heart failure had LV total creatine concentration and total CK activity significantly lower than sham values (11% and 30% lower, respectively). However for all aortic banded mice, a linear relationship was observed between ejection fraction and estimated maximal CK reaction velocity. Mice with heart failure also had corresponding decreases in the activities of the Mito-, MM-, and MB-CK isoenzymes, while the BB isoform remained unchanged. To determine whether these changes were model specific, mice were subjected to CAL or sham operation and followed for 7 weeks. Quantitative changes in total creatine, total CK activity, Mito-CK and MM-CK activities were similar for CAL and TAC mice. We conclude that alterations in the creatine kinase system occur during heart failure in mice qualitatively similar to those occurring in larger animals and humans, suggesting that mice are a suitable model for studying the role of such changes in the pathogenesis of heart failure.


Asunto(s)
Creatina Quinasa/metabolismo , Metabolismo Energético , Insuficiencia Cardíaca/fisiopatología , Miocardio/enzimología , Animales , Transporte Biológico , Creatina Quinasa/genética , Ecocardiografía , Insuficiencia Cardíaca/etiología , Masculino , Ratones , Ratones Endogámicos C57BL , Miocardio/metabolismo
18.
Basic Res Cardiol ; 101(1): 8-16, 2006 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-16132171

RESUMEN

Transverse aortic constriction (TAC) is used as a model of left ventricular hypertrophy and failure; however, there is extensive variability in the hypertrophic response. In 43 mice that underwent TAC with a 7-0 polypropylene suture, 13 were identified by echocardiography with initial LV hypertrophy that halted or regressed over time. Post-mortem examination on 7 of these mice found the constricting band to be intact, but partially internalized into the aortic lumen, allowing blood flow around the stenosis. To confirm this prospectively in vivo we then followed 12 mice after TAC for 6 weeks, using a new high resolution 3D-MRI method to measure minimal aortic arch cross-sectional area (CSA). Three of the 12 mice developed a significantly increased aortic CSA (0.31 +/- 0.15 on day 2 vs. 1.11 +/- 0.29 mm2 on day 42; P < 0.05), which was independently confirmed by dissection. These mice had internalized part of the band within the aortic lumen and, by week 6, showed significantly less LV hypertrophy and better systolic function. Nine of the 12 mice showed no change in aortic CSA. Band internalization could be prevented when two banding sutures were placed side-by-side (n = 10). This is the first observation that a significant subset of animals following TAC bypass the stenosis resulting in partial regression of hypertrophy.


Asunto(s)
Aorta/cirugía , Modelos Animales de Enfermedad , Hipertrofia Ventricular Izquierda , Ratones Endogámicos C57BL , Animales , Aorta/patología , Ligadura , Imagen por Resonancia Cinemagnética , Masculino , Ratones , Estudios Prospectivos
19.
Magn Reson Med ; 52(5): 1029-35, 2004 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-15508174

RESUMEN

The mouse is the predominant animal model to study the effect of gene manipulations. Imaging techniques to define functional effects on the heart caused by genomic alterations are becoming increasingly routine in mice, yet methods for in vivo investigation of metabolic phenotypes in the mouse heart are lacking. In this work, cardiac 1H-MRS was developed and applied in mouse hearts in vivo using a single-voxel technique (PRESS). In normal C57Bl/6J mice, stability and reproducibility achieved by dedicated cardiac and respiratory gating was demonstrated by measuring amplitude and zero-order phase changes of the unsuppressed water signal. Various cardiac metabolites, such as creatine, taurine, carnitine, or intramyocardial lipids were successfully detected and quantified relative to the total water content in voxels as small as 2 microl, positioned in the interventricular septum. The method was applied to a murine model of guanidinoacetate N-methyltransferase (GAMT) deficiency, which is characterized by substantially decreased myocardial creatine levels. Creatine deficiency was confirmed noninvasively in myocardium of anesthetized GAMT-/- mice. This is the first study to report the application of cardiac 1H-MRS in mice in vivo.


Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Miocardio/metabolismo , Animales , Carnitina/metabolismo , Creatina/metabolismo , Estudios de Factibilidad , Glicéridos/metabolismo , Ratones , Ratones Endogámicos C57BL , Taurina/metabolismo
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA