Empagliflozin inhibits increased Na influx in atrial cardiomyocytes of patients with HFpEF.

AIMS: Heart failure with preserved ejection fraction (HFpEF) causes substantial morbidity and mortality. Importantly, atrial remodelling and atrial fibrillation are frequently observed in HFpEF. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have recently been shown to improve clinical outcomes in HFpEF, and post-hoc analyses suggest atrial anti-arrhythmic effects. We tested if isolated human atrial cardiomyocytes from patients with HFpEF exhibit an increased Na influx, which is known to cause atrial arrhythmias, and if that is responsive to treatment with the SGTL2i empagliflozin. METHODS AND RESULTS: Cardiomyocytes were isolated from atrial biopsies of 124 patients (82 with HFpEF) undergoing elective cardiac surgery. Na influx was measured with the Na-dye Asante Natrium Green-2 AM (ANG-2). Compared to patients without heart failure (NF), Na influx was doubled in HFpEF patients (NF vs. HFpEF: 0.21 ± 0.02 vs. 0.38 ± 0.04 mmol/L/min (N = 7 vs. 18); P = 0.0078). Moreover, late INa (measured via whole-cell patch clamp) was significantly increased in HFpEF compared to NF. Western blot and HDAC4 pulldown assay indicated a significant increase in CaMKII expression, CaMKII autophosphorylation, CaMKII activity, and CaMKII-dependent NaV1.5 phosphorylation in HFpEF compared to NF, whereas NaV1.5 protein and mRNA abundance remained unchanged. Consistently, increased Na influx was significantly reduced by treatment not only with the CaMKII inhibitor autocamtide-2-related inhibitory peptide (AIP), late INa inhibitor tetrodotoxin (TTX) but also with sodium/hydrogen exchanger 1 (NHE1) inhibitor cariporide. Importantly, empagliflozin abolished both increased Na influx and late INa in HFpEF. Multivariate linear regression analysis, adjusting for important clinical confounders, revealed HFpEF to be an independent predictor for changes in Na handling in atrial cardiomyocytes. CONCLUSION: We show for the first time increased Na influx in human atrial cardiomyocytes from HFpEF patients, partly due to increased late INa and enhanced NHE1-mediated Na influx. Empagliflozin inhibits Na influx and late INa, which could contribute to anti-arrhythmic effects in patients with HFpEF.

Enhanced Cardiac CaMKII Oxidation and CaMKII-Dependent SR Ca Leak in Patients with Sleep-Disordered Breathing.

BACKGROUND: Sleep-disordered breathing (SDB) is associated with increased oxidant generation. Oxidized Ca/calmodulin kinase II (CaMKII) can contribute to atrial arrhythmias by the stimulation of sarcoplasmic reticulum Ca release events, i.e., Ca sparks. METHODS: We prospectively enrolled 39 patients undergoing cardiac surgery to screen for SDB and collected right atrial appendage biopsies. RESULTS: SDB was diagnosed in 14 patients (36%). SDB patients had significantly increased levels of oxidized and activated CaMKII (assessed by Western blotting/specific pulldown). Moreover, SDB patients showed a significant increase in Ca spark frequency (CaSpF measured by confocal microscopy) compared with control subjects. CaSpF was 3.58 ± 0.75 (SDB) vs. 2.49 ± 0.84 (no SDB) 1/100 µm-1s-1 (p < 0.05). In linear multivariable regression models, SDB severity was independently associated with increased CaSpF (B [95%CI]: 0.05 [0.03; 0.07], p < 0.001) after adjusting for important comorbidities. Interestingly, 30 min exposure to the CaMKII inhibitor autocamtide-2 related autoinhibitory peptide normalized the increased CaSpF and eliminated the association between SDB and CaSpF (B [95%CI]: 0.01 [-0.1; 0.03], p = 0.387). CONCLUSIONS: Patients with SDB have increased CaMKII oxidation/activation and increased CaMKII-dependent CaSpF in the atrial myocardium, independent of major clinical confounders, which may be a novel target for treatment of atrial arrhythmias in SDB.