Endothelium-myocardial coupling mediated by endothelium-dependent hyperpolarization contributes to diastolic improvement with empagliflozin in heart failure with preserved ejection fraction
K Watanabe, T Shiroto, S Godo, S Onuma, T Shindo, J Takahashi, M Miura, S YasudaAbstract
Background
Heart failure with preserved ejection fraction (HFpEF) is increasing in prevalence and remains a major unmet clinical need. Coronary microvascular dysfunction (CMD) contributes to HFpEF pathophysiology and is often characterized by impaired endothelium-dependent vasodilation. While nitric oxide (NO) signaling has been extensively studied, regulation of coronary microvascular tone depends on resistance vessels, which rely substantially on endothelium-dependent hyperpolarization (EDH) for vasorelaxation. Sodium-glucose cotransporter-2 (SGLT2) inhibitors improve cardiovascular outcomes in HFpEF, yet their effects on EDH-mediated vascular function remain unknown.
Purpose
To test whether empagliflozin restores EDH-mediated relaxation in resistance arteries and improves cardiac diastolic function.
Methods
Twelve-week-old male db/db mice and control littermates (db/m+) were treated with empagliflozin (0.03% w/w in chow) or vehicle for 8 weeks. Endothelium-dependent relaxation to acetylcholine (ACh) was assessed in mesenteric resistance arteries by wire myography. Endothelium-derived relaxing factor components were dissected using indomethacin (cyclooxygenase inhibition), Nω-nitro-L-arginine (L-NNA; NO synthase inhibition), and charybdotoxin plus apamin (EDH blockade) (n=7 per group); responses were summarized as area under the concentration–response curve (AUC). In Langendorff-perfused hearts, coronary flow (CF) and left ventricular peak negative dP/dt (dP/dtmin) were measured under indomethacin + L-NNA (EDH condition) (n=7 per group). Relaxation kinetics were also evaluated in isolated ventricular trabeculae from db/db mice (vehicle n=5; empagliflozin n=8). Myocardial SIRT1, phosphorylated-to-total AMPK (p-AMPK/AMPK), SERCA2a, and phospholamban Ser16 phosphorylation (p-PLN[Ser16]/PLN) were quantified by Western blotting (n=7 per group).
Results
Under indomethacin + L-NNA (EDH condition), ACh-induced relaxation in mesenteric resistance arteries was markedly impaired in db/db mice versus db/m+ controls and was significantly restored by empagliflozin (AUC; Figure 1). In Langendorff hearts under the EDH condition, empagliflozin increased coronary flow and improved left ventricular relaxation in db/db mice (Figure 2A). In isolated ventricular trabeculae, empagliflozin accelerated relaxation, shortening RT50 (P<0.05), with a trend toward improved normalized minimum dF/dt (P=0.073) (Figure 2B). Molecularly, empagliflozin increased myocardial SIRT1, p-AMPK/AMPK, and p-PLN(Ser16)/PLN, whereas SERCA2a abundance was unchanged.
Conclusions
Empagliflozin enhances EDH-dependent microvascular function and links this endothelial improvement to enhanced coronary perfusion and diastolic relaxation. These findings support EDH-dependent endothelium-myocardial coupling as a previously underrecognized mechanism of benefit of SGLT2 inhibition in HFpEF.Figure 1.Mesenteric artery EDH componentFigure 2.Perfusion and myocardial relaxation