β-Hydroxybutyrate Facilitates Postinfarction Cardiac Repair via Targeting PHD2

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.

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.

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.

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.