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Can Targeting Cardiomyocyte Metabolism Improve Cardiac Regeneration?
Review of “Mitochondrial substrate utilization regulates cardiomyocyte cell-cycle progression” from Nature Metabolism by Stuart P. Atkinson
The neonatal mammalian heart displays robust regenerative potential in the period just after birth; however, a metabolic shift from anaerobic glycolysis to mitochondrial oxidative phosphorylation during development, particularly towards fatty-acid use [1, 2], coincides with the loss of this ability. Fatty acid metabolism causes the cardiac mitochondria to produce elevated rates of reactive oxygen species (ROS) [3-5], and researchers led by Alisson C. Cardoso and Hesham A. Sadek (University of Texas Southwestern Medical Center, Dallas, TX, USA) recently established that these ROS can induce a DNA damage response in the early postnatal heart, thereby prompting the cell cycle arrest of cardiomyocytes . Given these findings, the team next sought to discover whether inhibiting fatty-acid utilization could reduce the ROS-mediated DNA damage response and promote cardiomyocyte proliferation in the postnatal heart .
The authors first studied the effect of feeding neonatal mice a fatty acid-free diet through mothers engineered not to produce fatty acids in milk and then supplying pups with fat-free food after weaning. Analysis of mouse pup hearts found that the absence of fatty acids in the diet prompted a modest prolongation of the postnatal proliferative window of cardiomyocytes before cell-cycle arrest at the ten-week stage, a timepoint that coincides with enhanced fatty acid synthesis by the liver.
Next, the authors engineered an inducible cardiomyocyte-specific pyruvate dehydrogenase kinase 4 (PDK4) knockout mouse model that leads to increased pyruvate dehydrogenase activity and an increase in the oxidation of glucose at the expense of fatty acids. Fascinatingly, this metabolic switch resulted in a decrease in cardiomyocyte size, DNA damage levels (both base oxidation and double-strand breaks), and DNA damage response marker expression and an increase in cardiomyocyte proliferation in the adult mouse. Encouragingly, the induced knockout of PDK4 after experimental myocardial infarction also prompted an improvement in left ventricular function and decreased cardiac remodeling. At the same time, the authors also found proof that the pharmacological inhibition of PDK4 in adult mice could also promote cardiomyocyte proliferation.
Overall, this study provides evidence that fatty-acid utilization significantly contributes to postnatal cardiomyocyte cell-cycle arrest through DNA damage-associated pathways, and that small molecule-based targeting of PDK4 may represent an efficient means to induce cardiomyocyte proliferation and prevent myocardial remodeling in the adult heart.
For more on how targeting cardiomyocyte metabolism may impact cardiac regeneration, stay tuned to the Stem Cells Portal!
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- Cardoso AC, Lam NT, Savla JJ, et al., Mitochondrial Substrate Utilization Regulates Cardiomyocyte Cell-cycle Progression. Nature Metabolism 2020;2:167-178.