Light-phase prednisone promotes glucose oxidation in heart through novel transactivation targets of cardiomyocyte-specific GR and KLF15

Circadian time-of-intake gates the cardioprotective effects of glucocorticoid administration in both healthy and infarcted hearts. The cardiomyocyte-specific glucocorticoid receptor (GR) and its co-factor, Kruppel-like factor (Klf15), play critical roles in maintaining normal heart function in the long-term and serve as pleiotropic regulators of cardiac metabolism. Despite this understanding, the cardiomyocyte-autonomous metabolic targets influenced by the concerted epigenetic action of GR-Klf15 axis remain undefined. Here, we demonstrate the critical roles of the cardiomyocyte-specific GR and Klf15 in orchestrating a circadian-dependent glucose oxidation program within the heart. Combining integrated transcriptomics and epigenomics with cardiomyocyte-specific inducible ablation of GR or Klf15, we identified their synergistic role in the activation of adiponectin receptor expression (Adipor1) and the mitochondrial pyruvate complex (Mpc1/2), thereby enhancing insulin-stimulated glucose uptake and pyruvate oxidation. Furthermore, in obese diabetic (db/db) mice exhibiting insulin resistance and impaired glucose oxidation, light-phase prednisone administration, as opposed to dark-phase prednisone dosing, effectively restored cardiomyocyte glucose oxidation and improved diastolic function towards control-like levels in a sex-independent manner. Collectively, our findings uncover novel cardiomyocyte-autonomous metabolic targets of the GR-Klf15 axis. This study highlights the circadian-dependent cardioprotective effects of glucocorticoids on cardiomyocyte glucose metabolism, providing critical insights into chrono-pharmacological strategies for glucocorticoid therapy in cardiovascular disease. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/572210v3_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cf4b3corg.highwire.dtl.DTLVardef@1547db1org.highwire.dtl.DTLVardef@7f85aorg.highwire.dtl.DTLVardef@141fe94_HPS_FORMAT_FIGEXP M_FIG C_FIG Brief summaryDepending on when it is taken during the day, the drug prednisone activates the heart to