Sodium-glucose cotransporter-2 inhibitors (SGLT2i) have a variety of cardiovascular and renoprotective effects and have been developed as novel agents for the treatment of heart failure. However, the beneficial mechanisms of SGLT2i on cardiac tissue need to be investigated further. In this study, we established a mouse model of acute myocardial infarction (AMI) using coronary artery constriction surgery and investigated the role of dapagliflozin (DAPA) in protecting cardiomyocytes from hypoxic injury induced by AMI. In vitro experiments were done using hypoxic cultured H9c2 ventricular cells to verify this potential mechanism. Expression of the SIRT family and related genes and proteins was verified by qPCR, Western blotting and immunofluorescence staining, and the intrinsic potential mechanism of cardiomyocyte death due to AMI and hypoxia was comprehensively investigated by RNA sequencing. The RNA sequencing results of cardiomyocytes from AMI mice showed that the SIRT family may be mainly involved in the mechanisms of hypoxia-induced cardiomyocyte death. In vitro hypoxia-induced ventricular cells showed the role of dapagliflozin in conferring resistance to hypoxic injury in cardiomyocytes. It showed that SIRT1/3/6 were downregulated in H9c2 cells in a hypoxic environment, and the addition of dapagliflozin significantly increased the gene and protein expression of SIRT1, 3 and 6. We then verified the underlying mechanisms induced by dapagliflozin in hypoxic cardiomyocytes using RNA-seq, and found that dapagliflozin upregulated the hypoxia-induced gene downregulation, which includes ESRRA, EPAS1, AGTRAP, etc., that associated with SIRTs-related and apoptosis-related signaling to prevent H9c2 cell death. This study provides laboratory data for SGLT2i dapagliflozin treatment of AMI and confirms that dapagliflozin can be used to treat hypoxia-induced cellular necrosis in cardiomyocytes, in which SIRT1 and SIRT3 may play an important role. This opens up further opportunities for SGLT2i in the treatment of heart disease.

(1) Background: The autonomic imbalance plays a role in vasovagal syncope (VVS) diagnosed by head-up tilting test (HUT). neuECG is a new method of recording skin electrical signals to simultaneously analyze skin sympathetic nerve activity (SKNA) and electrocardiogram. We hypothesize that SKNA is higher in subjects with tilt-positive than tilt-negative and the SKNA surges before syncope. (2) Methods: We recorded neuECG in 41 subjects who received HUT (according to the “Italian protocol”), including rest, tilt-up, provocation and recovery phases. Data were analyzed to determine the average SKNA (aSKNA, μV) per digitized sample. Electrocardiogram was used to calculate standard deviation of normal-to-normal beat intervals (SDNN). The “SKNA-SDNN index” was calculated by rest aSKNA multiplied by the ratio of tilt-up to rest SDNN. (3) Results: 16 of 41 (39%) subjects developed syncope. The aSKNA at rest phase is significantly higher in the tilt-positive (1.21 ± 0.27 µV) than tilt-negative subjects (1.02 ± 0.29 µV) (p = 0.034). There are significant surges and withdraw of aSKNA 30 s before and after syncope (both p ≤ 0.006). SKNA-SDNN index is able to predict syncope (p < 0.001). (4) Conclusion: Higher SKNA at rest phase is associated with positive HUT. The SKNA-SDNN index is a novel marker to predict syncope during HUT.

Betel-quid (BQ) is a commonly used psychoactive substance that renders a specific cardiotoxicity. The purpose of this study was to investigate the association between BQ chewing and premature ventricular contractions (PVC) in patients with cardiopulmonary symptoms, and examine the potential influences of cardiovascular and chronic diseases on such relationship. Participants were 146 patients with cardiopulmonary symptoms who participated in 24-h Holter electrocardiogram monitoring during 2012–2018 in a hospital serving residents that lived in a BQ high prevalence area. Data on substance uses and medical histories for cardiovascular and chronic diseases were collected. Baron–Kenny method was employed to evaluate possible mediation. In patients with cardiopulmonary symptoms, 36.3% were BQ users and 63.7% were nonusers. Adjusting for covariates, BQ chewing was significantly associated with heart failure and diabetes mellitus (adjusted odds ratio (aOR) = 3.4 and 2.3, respectively), but only heart failure was significantly correlated with a low and high level of PVC. Additionally controlling for the effect of heart failure, the risk of high PVC for BQ users reduced from 3.60 to 2.88; however, the risk for BQ chewers remained significant (95% CI: 1.06–7.84). Heart failure was found to explain 27.7% of the excessive effect of BQ use on high PVC. In conclusion, BQ use is directly associated with an elevated risk of high PVC in patients with cardiopulmonary symptoms. The higher risk might be elevated among patients who suffered heart failure. Given several research limitations, the findings from this study offer future opportunities for validation.

Aims: Metabolic syndrome (MetS) increases the risk of atrial arrhythmias (AA). Hypokalaemia, often secondary to diuretics or diet, frequently coexists with MetS and influences calcium handling. This study investigates the role of apamin-sensitive small-conductance calcium-activated potassium (SK) channels in atrial arrhythmogenesis under hypokalaemic MetS conditions. Methods and results: High-fat diets (HFD) were fed to mice at 8 weeks old for 16 weeks to mimic MetS. SK current was measured via voltage clamp, and Kcnn1–Kcnn3/CACNA1S, CACNA1C, and CACNA1D expression was assessed by qRT–PCR. We used optical mapping of intact mice hearts to assess the atrial action potential duration (APD), calcium transient duration (CaTD), conduction velocity (CV), conduction vector standard deviation, and AA inducibility in mice during hypokalaemia. HFD mice showed increased SK current and Kcnn3 expression. Apamin prolonged APD significantly in HFD mice. The APD heterogeneity of HFD was higher than that of the control mice. APD alternans threshold was significantly increased after apamin administration in HFD than that in control mice. Heterogeneity of conduction vectors in HFD is greater than that in control mice after apamin application. After apamin injection, AA inducibility is higher in HFD than that in control mice. AA inducibility was higher after apamin application in HFD, where AA was successfully induced. Conclusion: Our study demonstrated that apamin-sensitive SK channels may exert an antiarrhythmic effect in a hypokalaemic heart of the MetS model. These findings underscore the importance of evaluating the potential risks associated with the use of SK channel blockers in patients with hypokalaemic MetS.

Metabolic syndrome (MetS) is associated with arrhythmias and cardiovascular mortality. Arrhythmogenesis in MetS results from atrial structural and electrical remodelling. The small-conductance Ca²⁺-activated K⁺ (SK) currents modulate atrial repolarization and may influence atrial arrhythmogenicity. This study investigated the regulation of SK current perturbed by a high-fat diet (HFD) to mimic MetS. Thirty mice were divided into two groups that were fed with normal chow (CTL) and HFD for 4 months. Electrocardiography and echocardiography were used to detect cardiac electrical and structure remodelling. Atrial action potential duration (APD) and calcium transient duration (CaTD) were measured by optical mapping of Langendorff-perfused mice hearts. Atrial fibrillation (AF) inducibility and duration were assessed by burst pacing. Whole-cell patch clamp was performed in primarily isolated atrial myocytes for SK current density. The SK current density is higher in atrial myocytes from HFD than in CTL mice (P ≤ 0.037). The RNA and protein expression of SK channels are increased in HFD mice (P ≤ 0.041 and P ≤ 0.011, respectively). Action potential duration is shortened in HFD compared with CTL (P ≤ 0.015). The shortening of the atrial APD in HFD is reversed by the application of 100 nM apamin (P ≤ 0.043). Compared with CTL, CaTD is greater in HFD atria (P ≤ 0.029). Calcium transient decay (Tau) is significantly higher in HFD than in CTL (P = 0.001). Both APD and CaTD alternans thresholds were higher in HFD (P ≤ 0.043), along with higher inducibility and longer duration of AF in HFD (P ≤ 0.023). Up-regulation of apamin-sensitive SK currents plays a partial role in the atrial arrhythmogenicity of HFD mice.