Disruption of Glycolysis, TCA Cycle, Respiratory Chain, Calcium and Iron Homeostasis in Doxorubicin Induced Cardiomyopathy-An In-silico Approach

Doxorubicin is a well-known anthracycline antibiotic that is frequently used to treat a variety of malignancies. However, its clinical use is limited due to its adverse consequences, most notably cardiomyopathy. In the present work, we evaluated the molecular mechanisms behind the impairment of cardiac energetics in doxorubicin-induced cardiomyopathy. According to molecular docking, the interaction of doxorubicin with phosphofructokinase (PKF) and α-enolase is likely to negatively affect glycolysis. The interaction between doxorubicin with HMOX1 results in the accumulation of free iron. The free iron contributes to the heme-driven toxicity and the oxidizing environment that results in reactive oxygen species (ROS) production resulting from cell death. Additionally, the interaction of doxorubicin with HMOX1 impairs the availability of iron required for the Krebs cycle and ETC function. The interaction between doxorubicin and PINK1 results in a reduced membrane potential, which results in calcium accumulation. On the other hand, a lack of iron and calcium in the mitochondrial matrix results in ATP depletion, impairing the Krebs cycle activity. At the same time, the primary cause of doxorubicin-induced cardiomyopathy is cardiac energy metabolism. Thus, our work shows that doxorubicin impairs the activity of PFK, α-enolase, HMOX1, and PINK1, resulting in ATP production failure. As a result of changes in the heart energy metabolism, this ultimately leads to dilated cardiomyopathy caused by doxorubicin. Understanding the critical function of cardiac energy metabolism in doxorubicin-induced cardiomyopathy is critical for overcoming the obstacles that effectively limit the clinical effectiveness of this life-saving anti-cancer treatment.

Effects of Lipid Overload on Heart in Metabolic Diseases

Metabolic diseases are often associated with lipid and glucose metabolism abnormalities, which increase the risk of cardiovascular disease. Diabetic cardiomyopathy (DCM) is an important development of metabolic diseases and a major cause of death. Lipids are the main fuel for energy metabolism in the heart. The increase of circulating lipids affects the uptake and utilization of fatty acids and glucose in the heart, and also affects mitochondrial function. In this paper, the mechanism of lipid overload in metabolic diseases leading to cardiac energy metabolism disorder is discussed.

Global and Regional Myocardial Work in Female Adolescents with Weight Disorders

Background: Anorexia nervosa (AN) and obesity (OB) lead to changes in SBP (i.e., loading conditions) that may affect left ventricular (LV) myocardial work (MW). The novel concept of LV pressure-strain loops allows non-invasive estimation of MW, this latter being correlated with cardiac energy metabolism. In addition, the study of regional MW can detect subtle alterations in cardiac function by highlighting an abnormal distribution of MW. Objective: The aim of this study was to assess the cardiac function of AN and OB patients by evaluating global and regional LV strains and MW. Methods: Eighty-seven female adolescents, comprising 26 with AN (14.6 ± 1.9 yrs. old), 28 with OB (13.2 ± 1.4 yrs. old), and 33 controls (14.0 ± 2.0 yrs. old) underwent speckle-tracking echography to assess global and regional LV strains and MW. Results: SBP was higher in adolescents with obesity than in AN patients or controls. Global MW was similar between groups. In AN patients and controls, longitudinal strains were higher at the apex than at the base of the LV, whereas they were similar in obesity patients, owing to a decrease in their apical longitudinal strain. Consequently, their MW was higher at the basal level than either of the other two groups (1854 ± 272 vs. 1501 ± 280 vs. 1575 ± 295 mmHg% in OB patients, AN patients, and controls, respectively. Conclusion: Despite altered SBP, the global MW of adolescents with weight disorders was unaffected. However, in adolescents with obesity, the distribution of their regional LV MW was altered, which might reflect specific regional remodeling.

Creatine deficiency and heart failure

Impaired cardiac energy metabolism has been proposed as a mechanism common to different heart failure aetiologies. The energy-depletion hypothesis was pursued by several researchers, and is still a topic of considerable interest. Unlike most organs, in the heart, the creatine kinase system represents a major component of the metabolic machinery, as it functions as an energy shuttle between mitochondria and cytosol. In heart failure, the decrease in creatine level anticipates the reduction in adenosine triphosphate, and the degree of myocardial phosphocreatine/adenosine triphosphate ratio reduction correlates with disease severity, contractile dysfunction, and myocardial structural remodelling. However, it remains to be elucidated whether an impairment of phosphocreatine buffer activity contributes to the pathophysiology of heart failure and whether correcting this energy deficit might prove beneficial. The effects of creatine deficiency and the potential utility of creatine supplementation have been investigated in experimental and clinical models, showing controversial findings. The goal of this article is to provide a comprehensive overview on the role of creatine in cardiac energy metabolism, the assessment and clinical value of creatine deficiency in heart failure, and the possible options for the specific metabolic therapy.

Why the diabetic heart is energy inefficient: A ketogenesis and ketolysis perspective

Lack of glucose uptake compromises metabolic flexibility and reduces energy efficiency in the diabetes mellitus (DM) heart. Although increased utilization of fatty acid to compensate glucose substrate has been studied, less is known about ketone body metabolism in the DM heart. Ketogenic diet reduces obesity, a risk factor for T2DM. How ketogenic diet affects ketone metabolism in the DM heart remains unclear. At the metabolic level, the DM heart differs from the non-DM heart due to altered metabolic substrate and the T1DM heart differs from the T2DM heart due to insulin levels. How these changes affect ketone body metabolism in the DM heart are poorly understood. Ketogenesis produces ketone bodies by utilizing acetyl CoA whereas ketolysis consumes ketone bodies to produce acetyl CoA, showing their opposite roles in the ketone body metabolism. Cardiac-specific transgenic upregulation of ketogenesis enzyme or knockout of ketolysis enzyme causes metabolic abnormalities leading to cardiac dysfunction. Empirical evidence demonstrates upregulated transcription of ketogenesis enzymes, no change in the levels of ketone body transporters, very high levels of ketone bodies, and reduced expression and activity of ketolysis enzymes in the T1DM heart. Based on these observations, I hypothesize that increased transcription and activity of cardiac ketogenesis enzyme suppresses ketolysis enzymes in the DM heart, which decreases cardiac energy efficiency. The T1DM heart exhibits highly upregulated ketogenesis compared to T2DM due to lack of insulin that inhibits ketogenesis enzyme.

PCr/ATP Ratios and Mitochondrial Function in The Heart. A Comparative Study in Humans.

Objectives The objective of the study was to validate PCr/ATP ratios as an in vivo marker for cardiac mitochondrial function.Background Cardiac energy status, measured as PCr/ATP ratio with 31P-MRS in vivo, was shown to be a prognostic factor in heart failure and is lowered in cardiometabolic disease. As mitochondrial function is also hampered in these diseases and oxidative phosphorylation is the major contributor to ATP synthesis, the PCr/ATP ratio might be a reflection of cardiac mitochondrial function.Methods Thirty-eight patients scheduled for open heart surgery were enrolled in this study. Before surgery, cardiac 31P-MRS was performed. During surgery, tissue specimens from the right atrial appendage were obtained for the ex vivo assessment of mitochondrial function using high-resolution respirometry.Results The patient population included was heterogenous resulting in wide ranges of PCr/ATP ratios and ADP-stimulated respiration rates (PCr/ATP ranging from 0.533 to 1.717; ADP-stimulated respiration rates ranging from 28.5 to 94.6 pmol/mg/s). Correlation analysis however showed no relationship between PCr/ATP and ADP-stimulated respiration rates fueled by various substrates (octanoylcarnitine R2 < 0.005, p = 0.74; pyruvate R2 < 0.025, p = 0.41). Also, no correlations between PCr/ATP and maximally uncoupled respiration were found (octanoylcarnitine R2 = 0.005, p = 0.71; pyruvate R2 = 0.040, p = 0.26).Conclusions Our results do not support the use of cardiac energy status (PCr/ATP) as a surrogate marker of mitochondrial function in the heart. The dissociation of the two parameters in the present study suggests that mitochondrial function is not the only determinant of cardiac energy status.Condensed abstractThis study does not support the use of in vivo cardiac energy status (PCr/ATP ratio) as a surrogate marker of ex vivo mitochondrial function (maximal oxidative respiration). Although both PCr/ATP and mitochondrial function are reduced in cardiovascular disease, the dissociation of the two parameters in the present study shows that PCr/ATP is determined by more factors than only mitochondrial function. Hence, PCr/ATP is not a good marker for mitochondrial function, but it can be a valuable marker for cardiometabolic health in cardiometabolic studies.Trial registration: https://clinicaltrials.gov (NCT03049228).

Cardiac Energy Metabolism in Heart Failure

Alterations in cardiac energy metabolism contribute to the severity of heart failure. However, the energy metabolic changes that occur in heart failure are complex and are dependent not only on the severity and type of heart failure present but also on the co-existence of common comorbidities such as obesity and type 2 diabetes. The failing heart faces an energy deficit, primarily because of a decrease in mitochondrial oxidative capacity. This is partly compensated for by an increase in ATP production from glycolysis. The relative contribution of the different fuels for mitochondrial ATP production also changes, including a decrease in glucose and amino acid oxidation, and an increase in ketone oxidation. The oxidation of fatty acids by the heart increases or decreases, depending on the type of heart failure. For instance, in heart failure associated with diabetes and obesity, myocardial fatty acid oxidation increases, while in heart failure associated with hypertension or ischemia, myocardial fatty acid oxidation decreases. Combined, these energy metabolic changes result in the failing heart becoming less efficient (ie, a decrease in cardiac work/O 2 consumed). The alterations in both glycolysis and mitochondrial oxidative metabolism in the failing heart are due to both transcriptional changes in key enzymes involved in these metabolic pathways, as well as alterations in NAD redox state (NAD + and nicotinamide adenine dinucleotide levels) and metabolite signaling that contribute to posttranslational epigenetic changes in the control of expression of genes encoding energy metabolic enzymes. Alterations in the fate of glucose, beyond flux through glycolysis or glucose oxidation, also contribute to the pathology of heart failure. Of importance, pharmacological targeting of the energy metabolic pathways has emerged as a novel therapeutic approach to improving cardiac efficiency, decreasing the energy deficit and improving cardiac function in the failing heart.

Vasoplegia induces high energy demand and depletes cardiac energetics: a new insight into physiological concepts of cardiac work and a model for acute heart failure?

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): British Heart Foundation Background / Introduction Hearts subjected to constant high workload will, over time, fail. We hypothesized vasoplegia would create a high cardiac energy demand and deplete cardiac energy reserves, a mechanism causing failure. With 31Phosphorus Magnetic Resonance Spectroscopy, we can measure energy: ATP usage (via creatine kinase flux) and reserves of phosphocreatine (PCr/ATP ratio). Methods: Ten healthy volunteers were recruited mean age 37, mean BMI 22.4, 5 male, 5 female. A nitrate vasodilator (Glyceryl trinitrate, GTN) was used to induce vasoplegia, with MRI and MRS measurements taken before and during. Results There was reduced preload (falls in end diastolic volume and right atrial area) and afterload (mean blood pressure fall 14mmHg, p &lt;0.0001). Subjects mounted reflex tachycardia (mean heart rate rise 9bpm, p &lt; 0.0001) and inotropy (mean baseline ejection fraction increase 5%, p = 0.0002) hence cardiac output and rate pressure product were maintained (baseline CO 6.24 ± 1.45 L/min vs GTN 6.49 ± 1.43 L/min, p = 0.37; baseline RPP = 6929 ± 976 mmHg.bpm vs GTN 7214 ± 1051 mmHg.bpm, p = 0.06). There was a 58% increase in Creatine Kinase activity (kf) (baseline 0.158 s-1 vs GTN 0.249 s-1, p = 0.006) and CK flux (baseline 1.79 ± 0.78 umol/g/s vs GTN 2.59 ± 1.07 umol/g/s, p = 0.03), demonstrating increased ATP transfer. PCr/ATP fell (from 2.17 ± 0.2 to 1.99 ± 0.22, p = 0.027). Baseline PCr/ATP positively correlated with the change in stroke volume (R2 = 0.66, p = 0.005) during administration of GTN. In addition, whilst at rest, CK kf correlated with rate pressure product (R2 = 0.56, p = 0.03), there was no correlation seen during GTN. Conclusions We have shown vasoplegia increases energy demand upon the heart, despite unchanged cardiac output and rate pressure product. Further, we have shown a fall in Phosphocreatine/ATP ratio, suggesting this ATP transfer outstripped oxidative phosphorylation and the phosphocreatine pool was depleted in order to maintain ATP delivery. We speculate that progressive depletion of energetics in the context of high energy demand drives hearts under constant stress into failure. In addition, we demonstrate that the magnitude of the resting phosphocreatine pool relates to ability to augment stroke volume during stress and suggest that this may be protective against a decline into failure. Further work is needed, but PCr/ATP may be an important biomarker for treatments that target myocardial energetics to protect against failure. Abstract Figure 1