phosphocreatine and Hypertension--Pulmonary

Hypoxia-inducible factor (HIF) appears to function as a global master regulator of cellular and systemic responses to hypoxia. HIF pathway manipulation is of therapeutic interest; however, global systemic upregulation of HIF may have as yet unknown effects on multiple processes. We used a mouse model of Chuvash polycythemia (CP), a rare genetic disorder that modestly increases expression of HIF target genes in normoxia, to understand what these effects might be within the heart. An integrated in and ex vivo approach was employed. Compared with wild-type controls, CP mice had evidence (using in vivo magnetic resonance imaging) of pulmonary hypertension, right ventricular hypertrophy, and increased left ventricular ejection fraction. Glycolytic flux (measured using [(3)H]glucose) in the isolated contracting perfused CP heart was 1.8-fold higher. Net lactate efflux was 1.5-fold higher. Furthermore, in vivo (13)C-magnetic resonance spectroscopy (MRS) of hyperpolarized [(13)C1]pyruvate revealed a twofold increase in real-time flux through lactate dehydrogenase in the CP hearts and a 1.6-fold increase through pyruvate dehydrogenase. (31)P-MRS of perfused CP hearts under increased workload (isoproterenol infusion) demonstrated increased depletion of phosphocreatine relative to ATP. Intriguingly, no changes in cardiac gene expression were detected. In summary, a modest systemic dysregulation of the HIF pathway resulted in clear alterations in cardiac metabolism and energetics. However, in contrast to studies generating high HIF levels within the heart, the CP mice showed neither the predicted changes in gene expression nor any degree of LV impairment. We conclude that the effects of manipulating HIF on the heart are dose dependent.

Topics: Adenosine Triphosphate; Animals; Apoptosis Regulatory Proteins; Aryl Hydrocarbon Receptor Nuclear Translocator; Basic Helix-Loop-Helix Transcription Factors; Carbon Isotopes; Cardiotonic Agents; Disease Models, Animal; Glucose; Glycolysis; Heart; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia-Inducible Factor 1, alpha Subunit; Isolated Heart Preparation; Isoproterenol; L-Lactate Dehydrogenase; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Mice; Mutation; Myocardium; Phosphates; Phosphocreatine; Polycythemia; Pyruvic Acid; Repressor Proteins; Stroke Volume; Transcription Factors; Tritium; Von Hippel-Lindau Tumor Suppressor Protein

The present study was undertaken to explore the possible involvement of alterations in the mitochondrial energy-producing ability in the development of the right ventricular failure in monocrotaline-administered rats. The rats at the 6th week after subcutaneous injection of 60 mg/kg monocrotaline revealed marked myocardial hypertrophy and fibrosis, that is, severe cardiac remodeling. The time-course study on the cardiac hemodynamics of the monocrotaline-administered rat by the cannula and echocardiographic methods showed a reduction in cardiac double product, a decrease in cardiac output index, and an increase in the right ventricular Tei index, suggesting that the right ventricular failure was induced at the 6th week after monocrotaline administration in rats. The mitochondrial oxygen consumption rate of the right ventricular muscle isolated from the monocrotaline-administered animal was decreased, which was associated with a reduction in myocardial high-energy phosphates. Furthermore, the decrease in mitochondrial oxygen consumption rate was inversely related to the increase in the right ventricular Tei index of the monocrotaline-administered rats. These results suggest that impairment of the mitochondrial energy-producing ability is involved in the development of the right ventricular failure in monocrotaline-induced pulmonary hypertensive rats.

Topics: Adenosine Triphosphate; Animals; Cardiomyopathy, Dilated; Heart; Heart Failure; Hemodynamics; Hypertension, Pulmonary; Male; Mitochondria, Heart; Monocrotaline; Myocardium; Organ Size; Oxygen Consumption; Phosphocreatine; Random Allocation; Rats; Rats, Wistar; Ultrasonography