Altered glucose metabolism in adriamycin-induced heart failure

New Insights in Early Detection of Anticancer Drug-Related Cardiotoxicity Using Perfusion and Metabolic Imaging

Cardio-oncology requires a good knowledge of the cardiotoxicity of anticancer drugs, their mechanisms, and their diagnosis for better management. Anthracyclines, anti-vascular endothelial growth factor (VEGF), alkylating agents, antimetabolites, anti-human epidermal growth factor receptor (HER), and receptor tyrosine kinase inhibitors (RTKi) are therapeutics whose cardiotoxicity involves several mechanisms at the cellular and subcellular levels. Current guidelines for anticancer drugs cardiotoxicity are essentially based on monitoring left ventricle ejection fraction (LVEF). However, knowledge of microvascular and metabolic dysfunction allows for better imaging assessment before overt LVEF impairment. Early detection of anticancer drug-related cardiotoxicity would therefore advance the prevention and patient care. In this review, we provide a comprehensive overview of the cardiotoxic effects of anticancer drugs and describe myocardial perfusion, metabolic, and mitochondrial function imaging approaches to detect them before over LVEF impairment.

Detection of modifications in the glucose metabolism induced by genetic mutations in Saccharomyces cerevisiae by 13C- and H-NMR spectroscopy

NMR spectroscopy may offer a suitable technique to characterize the glucose metabolism in response to genetic mutations in cells. The effects of various genetic modifications in Saccharomyces cerevisiae yeast were investigated using 13C- and 1H-NMR spectroscopy associated with biochemical techniques. Cells were incubated with [1-13C]glucose in order to study glucose consumption and the formation of various end-products (ethanol, trehalose, glycerol, glutamate and amino acids) as a function of time. Two types of genetic modifications were studied in S. cerevisiae. A genetic modification deleted the N-terminal part of the TFC7 protein which is the smallest subunit (tau55) of the TFIIIC transcription factor. One secondary effect of this mutation was a large deletion of mitochondrial DNA giving the rho-phenotype. The other genetic modification corresponded to the disruption of the HUF gene; the mutated cells were rho+ like the reference strain. Both mutations increase the glycolysis rate and glycerol synthesis and decrease trehalose production. The most modified cells, which contain both TFC7 deletion and HUF gene disruption, utilize glucose in the most extreme manner as in these cells the largest production of the two glycolytic products (ethanol and glycerol) and the smallest trehalose formation occur. The HUF gene disruption serves as a positive modulator of glycolysis and respiration. However, the TFC7 deletion, associated with the phenotype rho-, induces the most damage in the cellular function, dramatically altering the behaviour of the Krebs cycle. The cycle becomes blocked at the level of 2-oxoglutarate, detected by a characteristic pattern of the 13C-NMR glutamate spectra. These NMR spectra corroborate the phenotypic data, the rho-phenotype corresponding to deletions of mitochondria DNA which block all mitochondria protein synthesis and render the cells unable to derive energy from respiration. Moreover, as a consequence of the Krebs cycle blocking, alanine formation is also observed.

Cardiac energy metabolism at several stages of adriamycin-induced heart failure in rats

To evaluate the changes in myocardial energy metabolism in the progressively failing myocardium, we measured myocardial level of adenosine triphosphate (ATP) using high-performance liquid chromatography (HPLC), and levels of lactate, alanine and free carnitine using 1H-nuclear magnetic resonance (NMR) spectroscopy in rats injected with adriamycin. The drug was injected intraperitoneally 2.5 mg/kg 6 times over a period of 2 weeks. Measurements were obtained 1 day (1 d), 3 weeks (3 w) and 6 weeks (6 w) after the last injection. No deaths were observed until the end of the 3rd week. The cumulative mortality rate 6 weeks after the last injection was 48%. ATP and free carnitine levels were not significantly changed at 1 d, while myocardial lactate was increased by 33% from the control values (P < 0.05). Lactate levels were reduced significantly, but not progressively, at 3 w (31% of control values) and at 6 w (69% of control values). Similar changes were observed in alanine levels. Free carnitine levels were progressively decreased at 3 w (74% of control values) and at 6 w (57% of control values). Changes in ATP levels paralleled those of free carnitine. Data suggest that a decrease in the myocardial level of free carnitine may be involved in progression of the heart failure induced by adriamycin in rats.

Calculation of absolute metabolic flux and the elucidation of the pathways of glutamate labeling in perfused rat heart by 13C NMR spectroscopy and nonlinear least squares analysis

Absolute metabolic fluxes in isolated perfused hearts have been determined by a nonlinear least squares analysis of glutamate labeling kinetics from [1-13C]glucose, [4-13C]beta-hydroxybutyrate, or [2-13C]acetate using 13C NMR spectroscopy. With glucose as substrate, the malate-aspartate shuttle flux was too slow to account for the reducing equivalents generated by glycolysis and to predict the observed oxygen consumption rate. For acetate and beta-hydroxybutyrate, the malate-aspartate shuttle had to be reversed for the network to agree with the observed oxygen consumption and glutamate labeling. Thus, an additional redox shuttle was required to reoxidize the NADH produced by cytoplasmic malate dehydrogenase. Using this model there was good agreement between the experimentally determined oxygen consumption and glutamate labeling and the calculated values of these parameters from the model for all substrates. The contribution of exogenous substrate to the overall tricarboxylic acid (TCA) cycle flux, 89.6 +/- 6.5% (mean +/- S.D.) as measured in the tissue extracts compared well with 91.4 +/- 4.2% calculated by the model. The ratio of TCA cycle flux to oxygen consumption for acetate, was 2.2 +/- 0.1, indicating that NADH production is principally accounted for by TCA cycle flux. For glucose or beta-hydroxybutyrate, this ratio was 2.9 +/- 0.2, consistent with the existence of other NADH producing reactions (e.g. glycolysis, beta-hydroxybutyrate oxidation).

Extracellular matrix arrangement in the papillary muscles of the adult rat heart. Alterations after doxorubicin administration and experimental hypertension

In the present study, we analyzed the components of the extracellular matrix (ECM) and its arrangement at the level of the papillary muscles in the adult rat heart using light and transmission and scanning electron microscopy techniques. Our results reveal that after a single dose (6 mg/kg) of dexorubicin to cause a significant decrease and disorganization of the endomysium and perimysium in the first week after injection, affecting the endomysial struts and perimysial strands. Degenerating myocytes and alterations of the coiled perimysial fibers were characteristic 4 weeks after treatment. After 8 weeks, ultrastructural alterations at the level of the plasma membrane of the myocytes and adjacent collagen network were present in the tip of the papillary muscles. These alterations may be responsible for the inefficiency of the valvular apparatus as an initial factor implicated in doxorubicin-induced congestive heart failure. Experimental hypertension, produced by constriction of the abdominal aorta, induced hypertrophy of the left ventricle, with increased perimysium and endomysium of the ECM at the level of the papillary muscles 4 weeks after aortic banding. Interstitial and perivascular fibrosis were observed 8 weeks after surgical treatment, and macrophages around the degenerating myocytes were characteristic 16 weeks after treatment. These alterations of the ECM network have been correlated with their possible implication in ventricular biomechanical properties.

Effects of oxidant exposure on substrate utilization and high-energy phosphates in isolated rat hearts

The effects of a xanthine oxidase-mediated free radical-generating system containing purine and iron-loaded transferrin or solutions containing hydrogen peroxide and iron-loaded transferrin on substrate utilization and high-energy phosphates were evaluated by nuclear magnetic resonance (NMR) spectroscopy in isolated perfused rat hearts. Hearts were supplied with lactate, acetate, and glucose, and the contribution of each substrate to acetyl coenzyme A was measured in control hearts and in the presence of a free radical-generating system. Perfused hearts were monitored by 31P NMR, and tissue extracts were analyzed by 13C NMR. Free radicals decreased the phosphocreatine and beta-ATP peak areas and reduced contractile function. Under control conditions, lactate, acetate, and endogenous sources were the major contributors of acetyl coenzyme A units, with only 5% originating from glucose. In the presence of a xanthine oxidase-mediated free radical-generating system, the glucose contribution increased to 54%, while contributions from acetate and endogenous sources were significantly reduced. Both 13C and 31P NMR analyses showed no significant accumulation of glycolytic sugar phosphates, suggesting little inhibition of glyceraldehyde-3-phosphate dehydrogenase. The increased contribution of glucose to the tricarboxylic acid cycle relative to acetate and endogenous sources is consistent with activation of pyruvate dehydrogenase. In contrast, hearts exposed to a hydrogen peroxide-based free radical-generating system showed an increase in lactate utilization, a decrease in acetate utilization, and no change in glucose utilization compared with control hearts. Glycolytic sugar phosphates were found to accumulate, suggesting possible inhibition of glyceraldehyde-3-phosphate. Thus, different radicals or their metabolites may have varying effects on myocardial metabolism.