Exercise Metabolic Memory Halts Pathological Cardiac Hypertrophy via PDK4

Pathological cardiac hypertrophy remains a major contributor to heart failure, with impaired glucose metabolism playing a central role. Although exercise is known to enhance myocardial glucose utilization, the long-term metabolic reprogramming effects of exercise and their role in preventing pathological hypertrophy are poorly understood. This study elucidates the mechanisms underlying the sustained metabolic memory induced by exercise-induced hypertrophic preconditioning (EHP) and its cardioprotective effects, with a focus on RNA methylation and arachidonic acid metabolism.

We used positron emission tomography/computed tomography to assess cardiac glucose uptake and bulk RNA sequencing to profile myocardial gene expression in sedentary and EHP mice. Genetic manipulation of Pdk4 (pyruvate dehydrogenase kinase 4) was achieved via adeno-associated virus-mediated overexpression and tamoxifen-inducible, cardiac-specific Pdk4 knockout. Pressure overload was induced by transverse aortic constriction in cardiac-specific Pdk4 knockout and control (MCM [Myh6-MerCreMer]) mice. Epigenetic regulation of Pdk4 by EHP was investigated using pyrosequencing, single-base elongation- and ligation-based quantitative polymerase chain reaction and dual-luciferase assays. Untargeted metabolomics and molecular docking, molecular dynamics simulation, and cellular thermal shift assay were performed on heart tissues and neonatal rat cardiomyocytes/fibroblasts to identify key metabolites and their mechanisms of action.

EHP conferred sustained myocardial glucose preference even after regression of physiological hypertrophy, mediated through METTL3 (methyltransferase-like 3)-dependent m6A RNA methylation that suppressed Pdk4 expression. Pdk4 overexpression abolished EHP-mediated cardioprotection, whereas Pdk4 deletion enhanced cardiac function and attenuated fibrosis under pressure overload. Metabolomic profiling identified arachidonic acid-derived metabolites 5-KETE (5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid), 12-keto-leukotriene B4, and 20-hydroxy-leukotriene B4 as novel inhibitors of hypertrophy and fibrosis. These metabolites attenuated cardiomyocyte hypertrophy and fibroblast transdifferentiation through inhibition of the ERK2 (extracellular signal-regulated kinase 2)/MAPK1 (mitogen-activated protein kinase 1) pathway.

This study establishes a unified mechanism by which EHP induces metabolic memory through RNA methylation-dependent suppression of Pdk4, leading to altered arachidonic acid metabolism and the accumulation of protective lipid mediators. These findings highlight the therapeutic potential of targeting the PDK4-arachidonic acid metabolites axis to mitigate pathological cardiac remodeling.