Empagliflozin reduces Ca/calmodulin‐dependent kinase II activity in isolated ventricular cardiomyocytes

AIMS: The EMPA‐REG OUTCOME study showed reduced mortality and hospitalization due to heart failure (HF) in diabetic patients treated with empagliflozin. Overexpression and Ca(2+)‐dependent activation of Ca(2+)/calmodulin‐dependent kinase II (CaMKII) are hallmarks of HF, leading to contractile dysfunction and arrhythmias. We tested whether empagliflozin reduces CaMKII‐ activity and improves Ca(2+)‐handling in human and murine ventricular myocytes. METHODS AND RESULTS: Myocytes from wild‐type mice, mice with transverse aortic constriction (TAC) as a model of HF, and human failing ventricular myocytes were exposed to empagliflozin (1 μmol/L) or vehicle. CaMKII activity was assessed by CaMKII–histone deacetylase pulldown assay. Ca(2+) spark frequency (CaSpF) as a measure of sarcoplasmic reticulum (SR) Ca(2+) leak was investigated by confocal microscopy. [Na(+)](i) was measured using Na(+)/Ca(2+)‐exchanger (NCX) currents (whole‐cell patch clamp). Compared with vehicle, 24 h empagliflozin exposure of murine myocytes reduced CaMKII activity (1.6 ± 0.7 vs. 4.2 ± 0.9, P < 0.05, n = 10 mice), and also CaMKII‐dependent ryanodine receptor phosphorylation (0.8 ± 0.1 vs. 1.0 ± 0.1, P < 0.05, n = 11 mice), with similar results upon TAC. In murine myocytes, empagliflozin reduced CaSpF (TAC: 1.7 ± 0.3 vs. 2.5 ± 0.4 1/100 μm(−1) s(−1), P < 0.05, n = 4 mice) but increased SR Ca(2+) load and Ca(2+) transient amplitude. Importantly, empagliflozin also significantly reduced CaSpF in human failing ventricular myocytes (1 ± 0.2 vs. 3.3 ± 0.9, P < 0.05, n = 4 patients), while Ca(2+) transient amplitude was increased (F/F(0): 0.53 ± 0.05 vs. 0.36 ± 0.02, P < 0.05, n = 3 patients). In contrast, 30 min exposure with empagliflozin did not affect CaMKII activity nor Ca(2+)‐handling but significantly reduced [Na(+)](i). CONCLUSIONS: We show for the first time that empagliflozin reduces CaMKII activity and CaMKII‐dependent SR Ca(2+) leak. Reduced Ca(2+) leak and improved Ca(2+) transients may contribute to the beneficial effects of empagliflozin in HF.