Exendin-4 inhibits atrial arrhythmogenesis in a model of myocardial infarction-induced heart failure via the GLP-1 receptor signaling pathway

[Smeglutide inhibits high glucose-induced proliferation of myocardial fibroblasts by downregulating TGFβ/Smad3 signaling]

OBJECTIVE

To investigate the effect of semaglutide on high glucose-induced proliferation of cardiac fibroblasts (CFs) and explore its possible mechanism.

METHODS

Primary mouse CFs, identified by detecting vimentin expression, were stimulated with 25 mmol/L and treated with 5-20 nmol/L semaglutide, and the cell proliferation was examined with CKK-8 assay for concentration screening.Cultured CFs exposed to high glucose (25 mmol/L) were treated with 5 nmol/L semaglutide, and the changes in cell cycle were detected using Cell Cycle Staining Kit; The mRNA expressions of α-smooth muscle actin (α-SMA), transforming growth factor-β1(TGF-β1) and Smad3 were detected using RT-qPCR, and the levels of type Ⅰ collagen (CoLⅠ) and type Ⅲ collagen (CoLIII) in the cell cultures were determined with ELISA.

RESULTS

Compared with the control cells, the CFs cultured in high glucose exhibited significantly enhanced proliferative activity (P<0.05) with increased percentage of S-phase cells.Semagutide treatment obviously inhibited high glucose-induced proliferation of the CFs (P<0.05) and reduced the percentage of S-phase cells.High glucose stimulation significantly increased the mRNA expressions of α-SMA, CoL Ⅰ and CoLIII in the cells (P<0.01), which were effectively lowered by semaglutide treatment (P<0.01).The expressions of TGF-β1 and Smad3 were significantly increased in high glucose-stimulated CFs (P<0.01) and were lowered by semaglutide treatment (P<0.01).

CONCLUSION

Semaglutide can inhibit high glucose-induced proliferation and collagen synthesis in mouse CFs possibly by downregulating the TGFβ/Smad3 signaling pathway.

Effects of liraglutide on ANP secretion and cardiac dynamics

To observe the effects of liraglutide (analog of glucagon-like peptide 1 (GLP-1)) on atrial natriuretic peptide (ANP) secretion and atrial dynamics, an ex vivo isolated rat atrial perfusion model was used to determine atrial ANP secretion and pulse pressure. DPP-4-/- mice were also established in vivo. ANP levels were determined by radioimmunoassay; GLP-1 content was determined by Elisa. The expression levels of GLP-1 receptor (GLP-1R), PI3K/AKT/mTOR, piezo 1, and cathepsin K were analyzed by Western blot. In the clinical study, patients with acute coronary syndrome (ACS) had low levels of plasma GLP-1 but relatively high levels of plasma ANP. In ex vivo (3.2 nmol/L) and in vivo (30 μg/kg) models, liraglutide significantly decreased ANP levels and atrial pulse pressure. Exendin9-39 alone (GLP-1R antagonist) reversibly significantly increased ANP secretion, and the reduction effect of liraglutide on the secretion of ANP was significantly alleviated by Exendin9-39. Exendin9-39 demonstrated slightly decreased atrial pulse pressure; however, combined liraglutide and Exendin9-39 significantly decreased atrial pulse pressure. Ly294002 (PI3K/AKT inhibitor) inhibited the increase of ANP secretion by liraglutide for a short time, while Ly294002 didn't counteract the decrease in pulse pressure by liraglutide in atrial dynamics studies. Liraglutide increased the expression of GLP-1R and PI3K/AKT/mTOR in isolated rat atria and the hearts of mice in vivo, whereas Exendin9-39 reversibly reduced the expression of GLP-1R and PI3K/AKT/mTOR. Piezo 1 was significantly decreased in wild type and DPP-4-/- mouse heart or isolated rat atria after being treated with liraglutide. Cathepsin K expression was only decreased in in vivo model hearts. Liraglutide can inhibit ANP secretion while decreasing atrial pulse pressure mediated by GLP-1R. Liraglutide probably plays a role in the reduction of ANP secretion via the PI3K/AKT/mTOR signaling pathway. Piezo 1 and cathepsin K may be involved in the liraglutide mechanism of reduction.

A meta-analysis evaluating indirectly GLP-1 receptor agonists and arrhythmias in patients with type 2 diabetes and myocardial infarction

Aims

At present, the effects of Glucagon-Like Peptide 1 Receptor agonists (GLP-1RAs) on arrhythmia in patients with type 2 diabetes mellitus (T2DM) and myocardial infarction (MI) are still unclear. Hence, this systematic review and meta-analysis aimed to investigate this association.

Methods and results

PubMed, Embase, Cochrane Library, and Web of Science were searched from inception to 30 April 2022. Randomized controlled trials (RCTs) that compared GLP-1RAs with placebo and met the critical criterion of a proportion of patients with T2DM and MI > 30% were included to verify our purpose indirectly. The outcomes of interest included atrial arrhythmias, ventricular arrhythmias, atrioventricular block (AVB), sinus arrhythmia, and cardiac arrest. Relative risk (RR) and 95% confidence intervals (CI) were pooled using a random-effects model. We included five RCTs with altogether 31,314 patients. In these trials, the highest proportion of patients with T2DM and MI was 82.6%, while the lowest was 30.7%. Compared to placebo, GLP-1RAs were associated with a lower risk of atrial arrhythmias (RR 0.81, 95% CI 0.70-0.95). There was no significant difference in the risk of ventricular arrhythmias (RR 1.26, 95% CI 0.87-1.80), AVB (RR 0.95, 95% CI 0.63-1.42), sinus arrhythmia (RR 0.62, 95% CI 0.26-1.49), and cardiac arrest (RR 0.97, 95% CI 0.52-1.83) between groups.

Conclusion

GLP-1RAs may be associated with reduced risk for atrial arrhythmias, which seems more significant for patients with T2DM combined with MI. More studies are needed to clarify the definitive anti-arrhythmic role of this drug.

An Overview of Similarities and Differences in Metabolic Actions and Effects of Central Nervous System Between Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) and Sodium Glucose Co-Transporter-2 Inhibitors (SGLT-2is)

GLP-1 receptor agonists (GLP-1RAs) and SGLT-2 inhibitors (SGLT-2is) are novel antidiabetic medications associated with considerable cardiovascular benefits therapying treatment of diabetic patients. GLP-1 exhibits atherosclerosis resistance, whereas SGLT-2i acts to ameliorate the neuroendocrine state in the patients with chronic heart failure. Despite their distinct modes of action, both factors share pathways by regulating the central nervous system (CNS). While numerous preclinical and clinical studies have demonstrated that GLP-1 can access various nuclei associated with energy homeostasis and hedonic eating in the CNS via blood-brain barrier (BBB), research on the activity of SGLT-2is remains limited. In our previous studies, we demonstrated that both GLP-1 receptor agonists (GLP-1RAs) liraglutide and exenatide, as well as an SGLT-2i, dapagliflozin, could activate various nuclei and pathways in the CNS of Sprague Dawley (SD) rats and C57BL/6 mice, respectively. Moreover, our results revealed similarities and differences in neural pathways, which possibly regulated different metabolic effects of GLP-1RA and SGLT-2i via sympathetic and parasympathetic systems in the CNS, such as feeding, blood glucose regulation and cardiovascular activities (arterial blood pressure and heart rate control). In the present article, we extensively discuss recent preclinical studies on the effects of GLP-1RAs and SGLT-2is on the CNS actions, with the aim of providing a theoretical explanation on their mechanism of action in improvement of the macro-cardiovascular risk and reducing incidence of diabetic complications. Overall, these findings are expected to guide future drug design approaches.