Myocardial Ketone Body Oxidation Contributes to Empagliflozin-Induced Improvements in Cardiac Contractility in Murine Heart Failure

Figure 1. Schematic overview study design. BDH1cko mice and littermate controls were randomly allocated to permanent coronary artery ligation of the left anterior descending coronary artery to induce myocardial infarction (MI) or sham surgery. Subsequently, mice in the MI groups were randomized based on left ventricular function to 6 weeks of treatment with empagliflozin or vehicle, resulting in six treatment groups. BDH1cko, cardiac‐specific knock‐out of the ketogenic enzyme D‐β‐hydroxybutyrate dehydrogenase‐1.

Figure 2. Validation of infarct and treatment model. (A) Expression and cardiac specific knock‐out of the D‐β‐hydroxybutyrate dehydrogenase‐1 (BDH1) protein were confirmed using western blot analysis. (B) Treatment with empagliflozin (EMPA) led to an increase in circulating ketone bodies. (C) Treatment with EMPA led to an increase in β‐hydroxybutryate (β‐OHB) in cardiac tissue. (D) Infarct size was determined after Masson's trichome staining of the mid‐papillary slice of the left ventricle after sacrifice. (E) Myocardial infarction (MI) surgery induced a significant decrease in left ventricular ejection fraction (LVEF) (%). Data are presented as mean ± standard error of the mean (N = 8–17). BDH1cko, cardiac‐specific knock‐out of the ketogenic enzyme D‐β‐hydroxybutyrate dehydrogenase‐1; TKB, total ketone body; VEH, vehicle. *p < 0.05; **p < 0.01; ***p < 0.001.

Figure 3. Effect of empagliflozin (EMPA) on cardiac function. Effects on cardiac function by treatment with EMPA and vehicle (VEH) in (A) littermate controls and (B) BDH1cko myocardial infarction (MI) animals. (C) Δ Left ventricular ejection fraction (LVEF) (%) for each study group. Data are presented as mean ± standard error of the mean (N = 8–15). BDH1cko, cardiac‐specific knock‐out of the ketogenic enzyme D‐β‐hydroxybutyrate dehydrogenase‐1. *p < 0.05.

Figure 4. Effect of empagliflozin (EMPA) on cardiac remodelling. (A) Ventricular weight (mg) adjusted for tibia length (mm). (B) Cardiomyocyte cell size (cross‐sectional area) (μm2). (C) Representative left ventricular sections stained with wheat germ agglutinin and Masson's trichrome. (D) Myocardial fibrosis (%) measured in the ventricular wall tissue contralateral to the infarct site. (E) mRNA level (fold change) levels of B‐type natriuretic peptide (BNP). Data are presented as mean ± standard error of the mean (N = 6–16). BDH1cko, cardiac‐specific knock‐out of the ketogenic enzyme D‐β‐hydroxybutyrate dehydrogenase‐1; KO, knock‐out; MI, myocardial infarction; VEH, vehicle; WT, wild‐type. *p < 0.05; **p < 0.01.