Background: Acute myocardial infarction (MI) remains one of the major causes of death worldwide, and innovative treatment strategies for MI represent a major challenge in cardiovascular medicine. Caloric restriction (CR) is the most potent nonpharmacological intervention known to prevent age-related disorders and extend lifespan. CR reduces glycolysis and elevates ketone body metabolism. However, whether and how CR or ketone body prevents the progression of MI remains poorly defined.
Methods: Mice treated with CR and β-hydroxybutyrate (β-OHB) underwent MI induced by ligation of the left anterior descending coronary artery. Cardiac function was assessed by echocardiographic measurements. Histological analysis, fluorescence-activated cell sorting, and immunofluorescence were used to assess myocardial neovascularization and macrophage filtration. The interaction and modification of β-OHB on PHD2 were analyzed by molecular docking, cellular thermal shift assay, liquid chromatography with tandem mass spectrometry, and coimmunoprecipitation. Macrophage-specific PHD2 K239R and K385R knock-in mice were used to determine the functional significance of β-OHB/PHD2 axis in vivo.
Results: Twelve weeks of CR markedly rescued postinfarction cardiac function by enhancing neovascularization. CR significantly increased circulating and cardiac ketone bodies, including β-OHB and acetoacetate. We identified β-OHB but not acetoacetate selectively targeted macrophages to stimulate VEGF (vascular endothelial growth factor) production in the peri-infarct area to promote neovascularization and cardiac repair. Mechanistically, β-OHB binds to and induces lysine β-hydroxybutyrylation of PHD2 at lysines 239 and 385, thus blocking its function in the hydroxylation of HIF-1α (hypoxia-inducible factor 1α) and resulting in enhanced HIF1α-dependent VEGF transcription and secretion. More importantly, specific PHD2 lys239 and lys385 mutations in macrophages abolished the preventive effects of exogenous β-OHB on MI in mice.
Conclusions: These data reveal a novel regulation of lysine β-hydroxybutyrylation on PHD2 and demonstrate a promising and therapeutic role for β-OHB/PHD2 in effectively accelerating neovascularization and preserving heart function after cardiac ischemia.
Keywords: caloric restriction; macrophages; myocardial infarction; prolyl hydroxylases; vascular endothelial growth factor.