Insulin Treatment Reduces Susceptibility to Atrial Fibrillation in Type 1 Diabetic Mice

Electro-metabolic coupling in atrial fibrillation: A deeper understanding of the metabolic driver

Atrial fibrillation (AF), the most common sustained heart rhythm abnormality, disrupts the normal link between electrical activity and atrial muscle contraction; this disruption is termed "excitation-contraction uncoupling". It weakens atrial contractions and contributes to the development and persistence of AF. In addition to electrical dysfunction, AF is increasingly recognized as a metabolic disorder. Metabolic remodeling may reportedly precede electrophysiological, contractile, and structural changes in AF. Both clinical observations and experimental studies have underscored the critical importance of metabolic homeostasis, and its disturbance is considered a key initial factor in the development of AF. Research in this field has progressed, and a consensus has emerged that metabolic status (energy flux) and electrophysiological signaling (ion flux) are interactively regulated, highlighting the concept of "electro-metabolic coupling." Their uncoupling or decompensation constitutes a common pathological basis of AF. Despite growing recognition of the importance of metabolic balance, the role of electro-metabolic coupling in AF remains unclear. Thus, this review aimed to discuss 1) a comprehensive understanding of electro-metabolic alterations post-AF, 2) the pivotal role of metabolic homeostasis in AF pathogenesis, and 3) the mutual regulation of electro-metabolic signaling, along with potential therapeutic strategies targeting these imbalances.

PANoptosis and cardiovascular disease: The preventive role of exercise training

Regulated cell death, including pyroptosis, apoptosis, and necroptosis, is vital for the body's defense system. Recent research suggests that these three types of cell death are interconnected, giving rise to a new concept called PANoptosis. PANoptosis has been linked to various diseases, making it crucial to comprehend its mechanism for effective treatments. PANoptosis is controlled by upstream receptors and molecular signals, which form polymeric complexes known as PANoptosomes. Cell death combines necroptosis, apoptosis, and pyroptosis and cannot be fully explained by any of these processes alone. Understanding pyroptosis, apoptosis, and necroptosis is essential for understanding PANoptosis. Physical exercise has been shown to suppress pyroptotic, apoptotic, and necroptotic signaling pathways by reducing inflammatory factors, proapoptotic factors, and necroptotic factors such as caspases and TNF-alpha. This ultimately leads to a decrease in cardiac structural remodeling. The beneficial effects of exercise on cardiovascular health may be attributed to its ability to inhibit these cell death pathways.

Association between estimated glucose disposal rate and atrial fibrillation recurrence in patients undergoing radiofrequency catheter ablation: a retrospective study

OBJECTIVE

Previous studies have shown a clear link between insulin resistance (IR) and an elevated risk of atrial fibrillation (AF). However, the relationship between the estimated glucose disposal rate (eGDR), which serves as a marker for IR, and the risk of AF recurrence after radiofrequency catheter ablation (RFCA) remains uncertain. Therefore, this study aimed to examine the potential association between the eGDR and the risk of AF recurrence following RFCA.

METHODS

This retrospective study was conducted at Nanchang University Affiliated Second Hospital. The study enrolled 899 patients with AF who underwent RFCA between January 2015 and January 2022. The formula used to calculate the eGDR was as follows: 19.02 - (0.22 * body mass index) - (3.26 * hypertension) - (0.61 * HbA1c). Cox proportional hazard regression models and exposure-effect curves were used to explore the correlation between the baseline eGDR and AF recurrence. The ability of the eGDR to predict AF recurrence was evaluated using the area under the receiver operating characteristic curve (AUROC).

RESULTS

The study observed a median follow-up period of 11.63 months, during which 296 patients experienced AF recurrence. K‒M analyses revealed that the cumulative incidence AF recurrence rate was significantly greater in the group with the lowest eGDR (log-rank p < 0.01). Participants with an eGDR ≥ 8 mg/kg/min had a lower risk of AF recurrence than those with an eGDR < 4 mg/kg/min, with a hazard ratio (HR) of 0.28 [95% confidence interval (CI) 0.18, 0.42]. Additionally, restricted cubic spline analyses demonstrated a linear association between the eGDR and AF recurrence (p nonlinear = 0.70). The area under the curve (AUC) for predicting AF recurrence using the eGDR was 0.75.

CONCLUSIONS

The study revealed that a decrease in the eGDR is associated with a greater AF recurrence risk after RFCA. Hence, the eGDR could be used as a novel biomarker for assessing AF recurrence risk.

Non-insulin-based insulin resistance indexes in predicting atrial fibrillation recurrence following ablation: a retrospective study

BACKGROUND

Insulin resistance (IR) is involved in the pathophysiological processes of arrhythmias. Increasing evidence suggests triglyceride and glucose (TyG) index, metabolic score for insulin resistance (METS-IR), triglyceride glucose-body mass index (TyG-BMI), and triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio are simple and reliable surrogates for IR. Although they have been associated with atrial fibrillation (AF), evidence supporting this is limited. Here, this is the first study to investigate the association between TyG-BMI index and AF recurrence following radiofrequency catheter ablation (RFCA). The performance of the four non-insulin-based IR indexes in predicting AF recurrence after ablation was explored.

METHODS

A total of 2242 AF patients who underwent a de novo RFCA between June 2018 to January 2022 at two hospitals in China were included in this retrospective study. The predictive values of IR indexes for AF recurrence after ablation were assessed.

RESULTS

During 1-year follow-up, 31.7% of patients experienced AF recurrence. The multivariable analysis revealed that TyG index, METS-IR, and TyG-BMI index were independent risk factors for AF recurrence. Restricted cubic spline analysis revealed a connection between METS-IR, TyG-BMI index, and AF recurrence (P < 0.001). Furthermore, incorporating the METS-IR or TyG-BMI index to the basic risk model with fully adjusted factors considerably enhanced the forecast of AF recurrence, as demonstrated by the C-statistic, continuous net reclassification improvement, and integrated discrimination improvement.

CONCLUSIONS

TyG index, METS-IR, and TyG-BMI index were independently associated with AF recurrence following ablation. Among the four non-insulin-based IR indexes, TyG-BMI had the highest predictive value, followed by METS-IR.

Association of type 1 diabetes mellitus and risk of atrial fibrillation: Systematic review and meta-analysis

AIM

Whether type 1 diabetes mellitus (T1DM) could be regarded as an independent risk factor for atrial fibrillation (AF) risk remains unclear, and thus we aimed to elaborate on this association in our meta-analysis.

METHODS

We systematically searched the Pubmed, Embase, Cochrane Library and Web of Science databases up to August 2022 for studies that were related to T1DM and AF incidence. Hazard ratios (HRs) and 95% confidence intervals (CIs) from each study were pooled via a random-effects model.

RESULTS

A total of four cohort studies were involved in our meta-analysis. Our pooled results suggested that T1DM patients had a higher AF risk (HR = 1.30, 95%CI 1.15-1.47) than the control group. In the subgroup analysis, a higher AF incidence was also found in female T1DM patients (HR = 1.50, 95%CI 1.26-1.79) than that in male patients. Compared with T1DM patients over 65 years, those with < 65 years showed an increased risk of AF (HR = 1.45, 95%CI 1.21-1.74).

CONCLUSIONS

Our meta-analysis demonstrated that T1DM was an independent risk factor for AF development, but further studies should be performed to provide more convincing evidence.

Overview of programmed electrical stimulation to assess atrial fibrillation susceptibility in mice

Atrial fibrillation (AF) is the most common human arrhythmia and is associated with increased risk of stroke, dementia, heart failure, and death. Among several animal models that have been used to investigate the molecular determinants of AF, mouse models have become the most prevalent due to low cost, ease of genetic manipulation, and similarity to human disease. Programmed electrical stimulation (PES) using intracardiac or transesophageal atrial pacing is used to induce AF as most mouse models do not develop spontaneous AF. However, there is a lack of standardized methodology resulting in numerous PES protocols in the literature that differ with respect to multiple parameters, including pacing protocol and duration, stimulus amplitude, pulse width, and even the definition of AF. Given this complexity, the selection of the appropriate atrial pacing protocol for a specific model has been arbitrary. Herein we review the development of intracardiac and transesophageal PES, including commonly used protocols, selected experimental models, and advantages and disadvantages of both techniques. We also emphasize detection of artifactual AF induction due to unintended parasympathetic stimulation, which should be excluded from results. We recommend that the optimal pacing protocol to elicit an AF phenotype should be individualized to the specific model of genetic or acquired risk factors, with an analysis using several definitions of AF as an endpoint.

Effects of Electrical Remodeling on Atrial Fibrillation in Diabetes Mellitus

Atrial fibrillation (AF) is one of the most common arrhythmias in medical practice. Diabetes mellitus (DM) is one of the independent risk factors for atrial fibrillation. The increased morbility of atrial fibrillation in diabetes mellitus is related to both structural and electrical remodeling of atrium. Based on studies of atrial electrophysiological changes in diabetes mellitus, this article focuses on the electrical remodeling of atrial cardiomyocytes, including remodeling of sodium channels, calcium channels, potassium channels and other channels, to provide the basis for the clinical management of antiarrhythmic drugs in diabetic patients with atrial fibrillation.

Diabetic hyperglycemia promotes primary tumor progression through glycation-induced tumor extracellular matrix stiffening

Diabetes mellitus is a complex metabolic disorder that is associated with an increased risk of breast cancer. Despite this correlation, the interplay between tumor progression and diabetes, particularly with regard to stiffening of the extracellular matrix, is still mechanistically unclear. Here, we established a murine model where hyperglycemia was induced before breast tumor development. Using the murine model, in vitro systems, and patient samples, we show that hyperglycemia increases tumor growth, extracellular matrix stiffness, glycation, and epithelial-mesenchymal transition of tumor cells. Upon inhibition of glycation or mechanotransduction in diabetic mice, these same metrics are reduced to levels comparable with nondiabetic tumors. Together, our study describes a novel biomechanical mechanism by which diabetic hyperglycemia promotes breast tumor progression via glycating the extracellular matrix. In addition, our work provides evidence that glycation inhibition is a potential adjuvant therapy for diabetic cancer patients due to the key role of matrix stiffening in both diseases.

Metabolic Inflexibility as a Pathogenic Basis for Atrial Fibrillation

Atrial fibrillation (AF), the most common sustained arrhythmia, is closely intertwined with metabolic abnormalities. Recently, a metabolic paradox in AF pathogenesis has been suggested: under different forms of pathogenesis, the metabolic balance shifts either towards (e.g., obesity and diabetes) or away from (e.g., aging, heart failure, and hypertension) fatty acid oxidation, yet they all increase the risk of AF. This has raised the urgent need for a general consensus regarding the metabolic changes that predispose patients to AF. “Metabolic flexibility” aptly describes switches between substrates (fatty acids, glucose, amino acids, and ketones) in response to various energy stresses depending on availability and requirements. AF, characterized by irregular high-frequency excitation and the contraction of the atria, is an energy challenge and triggers a metabolic switch from preferential fatty acid utilization to glucose metabolism to increase the efficiency of ATP produced in relation to oxygen consumed. Therefore, the heart needs metabolic flexibility. In this review, we will briefly discuss (1) the current understanding of cardiac metabolic flexibility with an emphasis on the specificity of atrial metabolic characteristics; (2) metabolic heterogeneity among AF pathogenesis and metabolic inflexibility as a common pathological basis for AF; and (3) the substrate-metabolism mechanism underlying metabolic inflexibility in AF pathogenesis.

Nanogenerator-Based Sensors for Energy Harvesting From Cardiac Contraction

Biomedical electric devices provide great assistance for health and life quality. However, their maintainable need remains a serious issue for the restricted duration of energy storage. Therefore, scientists are investigating alternative technologies such as nanogenerators that could harvest the mechanical energy of the human heart to act as the main source of energy for the pacemaker. Cardiac contraction is not a source for circulation; it utilizes body energy as an alternative energy source to recharge pacemaker devices. This is a key biomedical innovation to protect patients’ lives from possible risks resulting from repeated surgery. A batteryless pacemaker is possible via an implantable energy collecting tool, exchanging the restriction of the current batteries for a sustainable self-energy resource technique. In this context, the physiology of heart energy in the preservation of blood distribution pulse generation and the effects of cardiac hormones on the heart’s pacemaker shall be outlined. In this review, we summarized different technologies for the implantable energy harvesters and self-powered implantable medical devices with emphasis on nanogenerator-based sensors for energy harvesting from cardiac contraction. It could conclude that recent hybrid bio-nanogenerator systems of both piezoelectric and triboelectric devices based on biocompatible biomaterials and clean energy are promising biomedical devices for harvesting energy from cardiac and body movement. These implantable and wearable nanogenerators become self-powered biomedical tools with high efficacy, durability, thinness, flexibility, and low cost. Although many studies have proven their safety, there is a need for their long-term biosafety and biocompatibility. A further note on the biocompatibility of bio-generator sensors shall be addressed.

The pre-ablation triglyceride-glucose index predicts late recurrence of atrial fibrillation after radiofrequency ablation in non-diabetic adults

Background

Current prognostic risk scoring systems and biomarkers are routinely used as non-invasive methods for assessing late recurrence of atrial fibrillation (AF) in patients who have undergone radiofrequency catheter ablation (RFCA). This study aimed to investigate the predictive value of the triglyceride-glucose (TyG) index for late AF recurrence after RFCA in non-diabetic patients.

Methods

In total, 275 patients with AF who underwent RFCA at the Fuwai hospital (Beijing, China) between January 2016 and December 2018 were enrolled in this study. During follow up, patients were divided into late and non-late AF recurrence groups, based on whether they had experienced late AF recurrence determined by electrocardiography (ECG) examine or 48 h Holter monitoring. The TyG index was calculated using the following equation: ln [fasting triglycerides [mg/dL] × fasting glucose [mg/dL]/2].

Results

During a median follow-up of 26.1 months, late AF recurrence event rates significantly increased in the highest TyG index tertile group (tertile 3) compared to the lowest group (tertile 1) (54% versus 12%, respectively; p < 0.001). The mean TyG index was higher in the late AF recurrence group compared to the non- late AF recurrence group (9.42 ± 0.6 versus 8.68 ± 0.70, respectively; p < 0.001). On multivariate Cox regression analysis, the pre-ablation TyG index was an independent risk factor for late recurrence of AF after RFCA (hazard ratio [HR] 2.015 [95% confidence interval (CI): 1.408–4.117]; p = 0.009). Receiver operating characteristic (ROC) curve analysis revealed that TyG index was a significant predictor of late AF recurrence after RFCA, with an area under the ROC curve (AUC) of 0.737 (95% CI: 0.657–0.816; p < 0.001). In addition, the AUC of left atrial diameter (LAD) was 0.780 (95%CI: 0.703–0.857, p < 0.001). Finally, the TyG index positively correlated with LAD (r = 0.133, p = 0.027), high sensitivity C-reactive protein (r = 0.132, p = 0.028) and N-terminal pro B-type natriuretic peptide (r = 0.291, p < 0.001) levels.

Conclusions

An elevated pre-ablation TyG index was associated with an increased risk of late AF recurrence after RFCA in non-diabetic patients. The TyG index may be potentially useful as a novel biomarker for the risk stratification of late AF recurrence in non-diabetic patients.

Necroptosis is required for atrial fibrillation and involved in aerobic exercise-conferred cardioprotection

Necroptosis, a novel programmed cell death, plays a critical role in the development of fibrosis, yet its role in atrial fibrillation (AF) remains elusive. Mounting evidence demonstrates that aerobic exercise improves AF-related symptoms and quality of life. Therefore, we explored the role of necroptosis in AF pathogenesis and exercise-conferred cardioprotection. A mouse AF model was established either by calcium chloride and acetylcholine (CaCl₂ -Ach) administration for 3 weeks or high-fat diet (HFD) feeding for 12 weeks, whereas swim training was conducted 60 min/day, for 3-week duration. AF susceptibility, heart morphology and function and atrial fibrosis were assessed by electrophysiological examinations, echocardiography and Masson's trichrome staining, respectively. Both CaCl₂ -Ach administration and HFD feeding significantly enhanced AF susceptibility (including frequency and duration of episodes), left atrial enlargement and fibrosis. Moreover, protein levels of necroptotic signaling (receptor-interacting protein kinase 1, receptor-interacting protein kinase 3, mixed lineage kinase domain-like protein and calcium/calmodulin-dependent protein kinase II or their phosphorylated forms) were markedly elevated in the atria of AF mice. However, inhibiting necroptosis with necrostatin-1 partly attenuated CaCl₂ -Ach (or HFD)-induced fibrosis and AF susceptibility, implicating necroptosis as contributing to AF pathogenesis. Finally, we found 3-week swim training inhibited necroptotic signaling, consequently decreasing CaCl₂ -Ach-induced AF susceptibility and atrial structural remodeling. Our findings identify necroptosis as a novel mechanism in AF pathogenesis and highlight that aerobic exercise may confer benefits on AF via inhibiting cardiac necroptosis.