Empagliflozin attenuates arrhythmogenesis in diabetic cardiomyopathy by normalizing intracellular Ca 2+ handling in ventricular cardiomyocytes

Diabetic cardiomyopathy has been reported to increase the risk of fatal ventricular arrhythmia. The beneficial effects of the selective sodium-glucose cotransporter-2 inhibitor have not been fully examined in the context of antiarrhythmic therapy, especially its direct cardioprotective effects despite the negligible SGLT2 expression in cardiomyocytes. We aimed to examine the antiarrhythmic effects of empagliflozin (EMPA) treatment on diabetic cardiomyocytes, with a special focus on Ca handling. We conducted echocardiography and hemodynamic studies and studied electrophysiology, Ca handling, and protein expression in C57BLKS/J-lepr mice ( mice) and their nondiabetic lean heterozygous Lepr littermates ( / mice). Preserved systolic function with diastolic dysfunction was observed in 16-wk-old mice. During arrhythmia induction, mice had significantly increased premature ventricular complexes (PVCs) than controls, which was attenuated by EMPA. In protein expression analyses, calmodulin-dependent protein kinase II (CaMKII) Thr287 autophosphorylation and CaMKII-dependent RyR2 phosphorylation (S2814) were significantly increased in diabetic hearts, which were inhibited by EMPA. In addition, global -GlcNAcylation significantly decreased with EMPA treatment. Furthermore, EMPA significantly inhibited ventricular cardiomyocyte glucose uptake. Diabetic cardiomyocytes exhibited increased spontaneous Ca events and decreased sarcoplasmic reticulum (SR) Ca content, along with impaired Ca transient, all of which normalized with EMPA treatment. Notably, most EMPA-induced improvements in Ca handling were abolished by the addition of an -GlcNAcase (OGA) inhibitor. In conclusion, EMPA attenuated ventricular arrhythmia inducibility by normalizing the intracellular Ca handling, and we speculated that this effect was, at least partly, due to the inhibition of -GlcNAcylation via the suppression of glucose uptake into cardiomyocytes. SGLT2is are known to improve cardiovascular outcomes regardless of the presence of diabetes and decrease traditional cardiovascular risk factors. We demonstrated, for the first time, that EMPA inhibited PVCs by normalizing Ca handling in diabetic mice. Our data suggest that the effects of SGLT2is on calcium handling may occur because of suppression of -GlcNAcylation through inhibition of glucose uptake and not because of NHE inhibition, as previously suggested.