The Role of Ferroptosis in Atrial Fibrillation: A Promising Future.

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias, with its diagnosis being closely tied to higher rates of cardiovascular morbidity and mortality. AF is associated with a range of dangerous complications including stroke and heart failure, making it a key driver of healthcare spending and a major threat to global public health. The precise mechanisms that govern AF incidence and the onset of related complications, however, remain uncertain. Ferroptotic cell death has been the focus of rising interest in the cardiac arrhythmias, and there is recent evidence supporting a role for atrial ferroptosis as a mediator of AF development. Interventional strategies focused on ferroptotic activity, such as novel ferroptosis inhibitors, have also shown promise as a means of protecting against AF through their ability to reduce iron overload. In this review, we provide a summary of the proposed mechanisms whereby ferroptosis contributes to the pathophysiology of AF and their therapeutic implications.

Post translational modifications of connexin 43 in ventricular arrhythmias after myocardial infarction.

Ventricular arrhythmias are the leading cause of sudden cardiac death in patients after myocardial infarction (MI). Connexin43 (Cx43) is the most important gap junction channel-forming protein in cardiomyocytes. Dysfunction of Cx43 contributes to impaired myocardial conduction and the development of ventricular arrhythmias. Following an MI, Cx43 undergoes structural remodeling, including expression abnormalities, and redistribution. These alterations detrimentally affect intercellular communication and electrical conduction within the myocardium, thereby increasing the susceptibility to post-infarction ventricular arrhythmias. Emerging evidence suggests that post-translational modifications play essential roles in Cx43 regulation after MI. Therefore, Cx43-targeted management has the potential to be a promising protective strategy for the prevention and treatment of post infarction ventricular arrhythmias. In this article, we primarily reviewed the regulatory mechanisms of Cx43 mediated post-translational modifications on post-infarction ventricular arrhythmias. Furthermore, Cx43-targeted therapy have also been discussed, providing insights into an innovative treatment strategy for ventricular arrhythmias after MI.

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.

Calcineurin/NFATc3 pathway mediates myocardial fibrosis in diabetes by impairing enhancer of zeste homolog 2 of cardiac fibroblasts.

BACKGROUND: Diabetes is associated with myocardial fibrosis, while the underlying mechanisms remain elusive. The aim of this study is to investigate the underlying role of calcineurin/nuclear factor of activated T cell 3 (CaN/NFATc3) pathway and the Enhancer of zeste homolog 2 (EZH2) in diabetes-related myocardial fibrosis. METHODS: Streptozotocin (STZ)-injected diabetic rats were randomized to two groups: the controlled glucose (Con) group and the diabetes mellitus (DM) group. Eight weeks later, transthoracic echocardiography was used for cardiac function evaluation, and myocardial fibrosis was visualized by Masson trichrome staining. The primary neonatal rat cardiac fibroblasts were cultured with high-glucose medium with or without cyclosporine A or GSK126. The expression of proteins involved in the pathway was examined by western blotting. The nuclear translocation of target proteins was assessed by immunofluorescence. RESULTS: The results indicated that high glucose treatment increased the expression of CaN, NFATc3, EZH2 and trimethylates lysine 27 on histone 3 (H3K27me3) in vitro and in vivo. The inhibition of the CaN/NFATc3 pathway alleviated myocardial fibrosis. Notably, inhibition of CaN can inhibit the nuclear translocation of NFATc3, and the expression of EZH2 and H3K27me3 protein induced by high glucose. Moreover, treatment with GSK126 also ameliorated myocardial fibrosis. CONCLUSION: Diabetes can possibly promote myocardial fibrosis by activating of CaN/NFATc3/EZH2 pathway.

Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation.

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca2+-activated K+ channels (SK channels) are dependent on intracellular Ca2+ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.

Regulation of KCNMA1 transcription by Nrf2 in coronary arterial smooth muscle cells.

The large conductance Ca2+-activated K+ (BK) channels, composed of the pore-forming α subunits (BK-α, encoded by KCNMA1 gene) and the regulatory ß1 subunits (BK-ß1, encoded by KCNMB1 gene), play a unique role in the regulation of coronary vascular tone and myocardial perfusion by linking intracellular Ca2+ homeostasis with excitation-contraction coupling in coronary arterial smooth muscle cells (SMCs). The nuclear factor erythroid 2-related factor 2 (Nrf2) belongs to a member of basic leucine zipper transcription factor family that regulates the expression of antioxidant and detoxification enzymes by binding to the antioxidant response elements (AREs) of these target genes. We have previously reported that vascular BK-ß1 protein expression was tightly regulated by Nrf2. However, the molecular mechanism underlying the regulation of BK channel expression by Nrf2, particularly at transcription level, is unknown. In this study, we hypothesized that KCNMA1 and KCNMB1 are the target genes of Nrf2 transcriptional regulation. We found that BK channel protein expression and current density were diminished in freshly isolated coronary arterial SMCs of Nrf2 knockout (KO) mice. However, BK-α mRNA expression was reduced, but not that of BK-ß1 mRNA expression, in the arteries of Nrf2 KO mice. Promoter-Nrf2 luciferase reporter assay confirmed that Nrf2 binds to the ARE of KCNMA1 promoter, but not that of KCNMB1. Adenoviral expression and pharmacological activation of Nrf2 increased BK-α and BK-ß1 protein levels and enhanced BK channel activity in coronary arterial SMCs. Hence, our results indicate that Nrf2 is a key determinant of BK channel expression and function in vascular SMCs. Nrf2 facilitates BK-α expression through a direct increase in gene transcription, whereas that on BK-ß1 is through a different mechanism.

Glucose fluctuations promote vascular BK channels dysfunction via PKCα/NF-κB/MuRF1 signaling.

Glucose fluctuations may contribute to large conductance calcium activated potassium (BK) channel dysfunction. However, the underlying mechanisms remain elusive. The aim of this study was to investigate the molecular mechanisms involved in BK channel dysfunction as a result of glucose fluctuations. A rat diabetic model was established through the injection of streptozotocin. Glucose fluctuations in diabetic rats were induced via consumption and starvation. Rat coronary arteries were isolated and coronary vascular tensions were measured after three weeks. Rat coronary artery smooth muscle cells were isolated and whole-cell BK channel currents were recorded using a patch clamp technique. Human coronary artery smooth muscle cells in vitro were used to explore the underlying mechanisms. After incubation with iberiotoxin (IBTX), the Δ tensions (% Max) of rat coronary arteries in the controlled diabetes mellitus (C-DM), the uncontrolled DM (U-DM) and the DM with glucose fluctuation (GF-DM) groups were found to be 84.46 ± 5.75, 61.89 ± 10.20 and 14.77 ± 5.90, respectively (P < .05), while the current densities of the BK channels in the three groups were 43.09 ± 4.35 pA/pF, 34.23 ± 6.07 pA/pF and 17.87 ± 4.33 pA/pF, respectively (P < .05). The Δ tensions (% Max) of rat coronary arteries after applying IBTX in the GF-DM rats injected with 0.9% sodium chloride (NaCl) (GF-DM + NaCl) and the GF-DM rats injected with N-acetyl-L-cysteine (NAC) (GF-DM + NAC) groups were found to be 8.86 ± 1.09 and 48.90 ± 10.85, respectively (P < .05). Excessive oxidative stress and the activation of protein kinase C (PKC) α and nuclear factor (NF)-κB induced by glucose fluctuations promoted the decrease of BK-ß1 expression, while the inhibition of reactive oxygen species (ROS), PKCα, NF-κB and muscle ring finger protein 1 (MuRF1) reversed this effect. Glucose fluctuations aggravate BK channel dysfunction via the ROS overproduction and the PKCα/NF-κB/MuRF1 signaling pathway.

Glucose Fluctuations Promote Aortic Fibrosis through the ROS/p38 MAPK/Runx2 Signaling Pathway.

AIM: Glucose fluctuations may be responsible for, or further the onset of arterial hypertension, but the exact mechanisms remain unclear. The purpose of this study was to investigate the mechanisms behind and related to aortic fibrosis and aortic stiffening induced by glucose fluctuations. METHODS: Sprague-Dawley rats were injected with streptozotocin (STZ) and randomly divided into three treatment groups: controlled STZ-induced diabetes (C-STZ); uncontrolled STZ-induced diabetes (U-STZ); and STZ-induced diabetes with glucose fluctuations (STZ-GF). After 3 weeks, rat blood pressure (BP) was tested, and aortic fibrosis was detected by using the Masson trichrome staining technique. Levels of p38 mitogen-activated protein kinase (p38 MAPK), runt-related transcription factor 2 (Runx2), collagen type 1 (collagen I), and NADPH oxidases were determined by Western blot.Rat vascular smooth muscle cells in vitro were used to explore underlying mechanisms. RESULTS: The systolic BP of diabetic rats in the C-STZ, U-STZ, and STZ-GF groups was 127.67 ± 6.53, 150.03 ± 5.24, and 171.63 ± 3.53 mm Hg, respectively (p< 0.05). The mean BP of diabetic rats in the three groups was 91.20 ± 10.07, 117.29 ± 4.28, and 140.58 ± 2.14 mm Hg, respectively (p< 0.05). The diastolic BP of diabetic rats in the three groups was 73.20 ± 12.63, 101.93 ± 5.79, and 125.37 ± 4.62 mm Hg, respectively (p< 0.05). The ratios of fibrosis areas in the aortas of the three groups were 11.85 ± 1.23, 29.00 ± 0.87, and 48.36 ± 0.55, respectively (p< 0.05). The expressions of p38 MAPK, Runx2, and collagen I were significantly increased in the STZ-GF group. In vitro, applications of inhibitors of reactive oxygen species (ROS) and p38 MAPK successfully reversed glucose fluctuations that would have possibly induced aortic fibrosis. CONCLUSIONS: Blood glucose fluctuations aggravate aortic fibrosis via affecting the ROS/p38 MAPK /Runx2 signaling pathway.

Serum biomarkers combined with ultrasonography for early diagnosis of non-alcoholic fatty liver disease confirmed by magnetic resonance spectroscopy.

Magnetic resonance spectroscopy (MRS) is notably accurate for even minimal degree of hepatic steatosis in non-alcoholic fatty liver disease (NAFLD). But routine use of MRS is limited by its cost and availability. In this study, we developed a diagnostic model combining ultrasonography with biomarkers to identify mild NAFLD, with MRS as the reference standard. A total of 422 eligible subjects were enrolled. The serum levels of fibroblast growth factor 21 (FGF21), cytokeratin 18 M65ED, proteinase 3, neutrophil elastase, alpha-1 antitrypsin, and neutrophil elastase/alpha-1 antitrypsin were measured using ELISA assays. We found that among the six biomarkers, only serum FGF21 was independently associated with intrahepatic triglyceride content (IHTC, standardized ß = 0.185, P < 0.001) and was an independent risk factor for mild NAFLD. Thus, we established a Mild NAFLD Model based on FGF21, alanine transaminase, triglycerides, and body mass index. The area under the receiver-operating characteristic curve of the Mild NAFLD Model was 0.853 (95% confidence interval: 0.816-0.886). Furthermore, a two-step approach combining ultrasonography with the Mild NAFLD Model displayed a better sensitivity for diagnosing mild NAFLD compared with each method alone, with a sensitivity of 97.32% and a negative predictive value of 85.48%. This two-step approach combining ultrasonography and the Mild NAFLD Model derived from serum FGF21 improves the diagnosis of mild NAFLD and can be applied to the early diagnosis of NAFLD in clinical practice.

Kinetic Studies on Radical Scavenging Activity of Kaempferol Decreased by Sn(II) Binding.

Sn(II) binds to kaempferol (HKaem, 3,4',5,7-tetrahydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) at the 3,4-site forming [Sn(II)(Kaem)2] complex in ethanol. DPPH• scavenging efficiency of HKaem is dramatically decreased by SnCl2 coordination due to formation of acid inhibiting deprotonation of HKaem as ligands and thus reduces the radical scavenging activity of the complex via a sequential proton-loss electron transfer (SPLET) mechanism. Moderate decreases in the radical scavenging of HKaem are observed by Sn(CH3COO)2 coordination and by contact between Sn and HKaem, in agreement with the increase in the oxidation potential of the complex compared to HKaem, leading to a decrease in antioxidant efficiency for fruits and vegetables with Sn as package materials.

Regulation of Coronary Arterial Large Conductance Ca2+-Activated K+ Channel Protein Expression and Function by n-3 Polyunsaturated Fatty Acids in Diabetic Rats.

AIM: The objective of this study was to examine the effects of n-3 polyunsaturated fatty acids (n-3 PUFAs) on coronary arterial large conductance Ca2+-activated K+ (BK) channel function in coronary smooth muscle cells (SMCs) of streptozotocin-induced diabetic rats. METHODS: The effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on coronary BK channel open probabilities were determined using the patch clamp technique. The mRNA and protein expressions of BK channel subunits were measured using qRT-PCR and Western blots. The coronary artery tension and coronary SMC Ca2+ concentrations were measured using a myograph system and fluorescence Ca2+ indicator. RESULTS: Compared to nondiabetic control rats, the BK channel function was impaired with a reduced response to EPA and DHA in freshly isolated SMCs of diabetic rats. Oral administration of n-3 PUFAs had no effects on protein expressions of BK channel subunits in nondiabetic rats, but significantly enhanced those of BK-ß1 in diabetic rats without altering BK-α protein levels. Moreover, coronary ring tension induced by iberiotoxin (a specific BK channel blocker) was increased and cytosolic Ca2+ concentrations in coronary SMCs were decreased in diabetic rats, but no changes were found in nondiabetic rats. CONCLUSIONS: n-3 PUFAs protect the coronary BK channel function and coronary vasoreactivity in diabetic rats as a result of not only increasing BK-ß1 protein expressions, but also decreasing coronary artery tension and coronary smooth muscle cytosolic Ca2+ concentrations.

Effect of Dietary Resistant Starch on Prevention and Treatment of Obesity-related Diseases and Its Possible Mechanisms.

Overweight or obesity has become a serious public health problem in the world, scientists are concentrating their efforts on exploring novel ways to treat obesity. Nowadays, the availabilities of bariatric surgery and pharmacotherapy have enhanced obesity treatment, but it should has support from diet, physical exercise and lifestyle modification, especially the functional food. Resistant starch, an indigestible starch, has been studied for years for its beneficial effects on regulating blood glucose level and lipid metabolism. The aim of this review is to summarize the effect of resistant starch on weight loss and the possible mechanisms. According to numerous previous studies it could be concluded that resistant starch can reduce fat accumulation, enhance insulin sensitivity, regulate blood glucose level and lipid metabolism. Recent investigations have focused on the possible associations between resistant starch and incretins as well as gut microbiota. Resistant starch seems to be a promising dietary fiber for the prevention or treatment of obesity and its related diseases.

[3D Reconstruction of PCL Based on MRI and CT Image Fusion].

OBJECTIVE: To reconstruct three-dimensional (3D) image of posterior cruciate ligament (PCL) based on MRI and CT image fusion. METHODS: CT and MRI scans were performed on 12 knees of young men. The Dicom data were extracted and unified. The outline of PCL on MRI imaging was drew and plugged into the CT data. Finally, the visible 3D image of PCL with adjacent bones was reconstructed. The imaging anatomical measurements were examined and compared with those in published literature. RESULTS: Two cases were excluded from this study because of data deviations. The 3D visible reconstruction of PCL was proved to be feasible on the other ten cases. CONCLUSION: Three-dimensional visible reconstruction of PCL based on CT and MRI image fusion is feasible, which can provide support for individualized treatment of PCL injuries. Further simplification with increased accuracy may be needed.

The role and mechanism of heme oxygenase-1 in arrhythmias.

The global incidence and prevalence of arrhythmias are continuously increasing. However, the precise mechanisms of underlying arrhythmogenesis and the optimal measures for effective treatment remain incompletely understood. The inducible form of heme oxygenase, known as heme oxygenase-1 (HO-1), is recognized as a potent antioxidant molecule capable of exerting anti-inflammatory and anti-apoptotic effects. Recent research indicates that HO-1 plays a role in preventing arrhythmias by mitigating cardiac remodeling, including electrical remodeling, ion remodeling, and structural remodeling. This review aimed to consolidate current knowledge regarding the involvement of HO-1 in arrhythmias and elucidate its underlying mechanisms of action.

Role of angiotensin receptor-neprilysin inhibitor in diabetic complications.

Diabetes mellitus is a prevalent disorder with multi-system manifestations, causing a significant burden in terms of disability and deaths globally. Angio-tensin receptor-neprilysin inhibitor (ARNI) belongs to a class of medications for treating heart failure, with the benefits of reducing hospitalization rates and mortality. This review mainly focuses on the clinical and basic investigations related to ARNI and diabetic complications, discussing possible physiological and molecular mechanisms, with insights for future applications.

Diabetes Promotes Myocardial Fibrosis via AMPK/EZH2/PPAR-γ Signaling Pathway.

BACKGRUOUND: Diabetes-induced cardiac fibrosis is one of the main mechanisms of diabetic cardiomyopathy. As a common histone methyltransferase, enhancer of zeste homolog 2 (EZH2) has been implicated in fibrosis progression in multiple organs. However, the mechanism of EZH2 in diabetic myocardial fibrosis has not been clarified. METHODS: In the current study, rat and mouse diabetic model were established, the left ventricular function of rat and mouse were evaluated by echocardiography and the fibrosis of rat ventricle was evaluated by Masson staining. Primary rat ventricular fibroblasts were cultured and stimulated with high glucose (HG) in vitro. The expression of histone H3 lysine 27 (H3K27) trimethylation, EZH2, and myocardial fibrosis proteins were assayed. RESULTS: In STZ-induced diabetic ventricular tissues and HG-induced primary ventricular fibroblasts in vitro, H3K27 trimethylation was increased and the phosphorylation of EZH2 was reduced. Inhibition of EZH2 with GSK126 suppressed the activation, differentiation, and migration of cardiac fibroblasts as well as the overexpression of the fibrotic proteins induced by HG. Mechanical study demonstrated that HG reduced phosphorylation of EZH2 on Thr311 by inactivating AMP-activated protein kinase (AMPK), which transcriptionally inhibited peroxisome proliferator-activated receptor γ (PPAR-γ) expression to promote the fibroblasts activation and differentiation. CONCLUSION: Our data revealed an AMPK/EZH2/PPAR-γ signal pathway is involved in HG-induced cardiac fibrosis.

Empagliflozin Induces Vascular Relaxation in Rat Coronary Artery Due to Activation of BK Channels.

Purpose: The aim of this study was to investigate the effects and mechanisms of SGLT2 inhibitor empagliflozin on diabetic coronary function. Methods: A rat diabetic model was established by injection of streptozotocin. Rats in the treated group were administered empagliflozin by gavage and rat coronary vascular tensions were measured after eight weeks. Large conductance calcium activated K+ channel currents were recorded using a patch clamp technique, while human coronary artery smooth muscle cells were used to explore the underlying mechanisms. Results: After incubation with empagliflozin (10, 30, 100, 300, 1000 µmol/L), the Δ relaxation % of rat coronary arteries were 2.459 ± 1.304, 3.251 ± 1.119, 6.946 ± 3.407, 28.36 ± 11.47, 86.90 ± 3.868, respectively. Without and with empagliflozin in the bath solution, BK channel opening probabilities at a membrane potential of +60 mV were 0.0458 ± 0.0517 and 0.3413 ± 0.2047, respectively (p < 0.05, n = 4 cells). After incubation with iberiotoxin, the Δ tensions of rat coronary arteries in the control (Ctrl), untreated (DM), low empagliflozin (10 mg/kg/d)-treated (DM+L-EMPA) and high empagliflozin (30mg/kg/d)-treated (DM+H-EMPA) group were 103.20 ± 5.85, 40.37 ± 22.12, 99.47 ± 28.51, 78.06 ± 40.98, respectively (p < 0.01 vs Ctrl, n = 3-7; p < 0.001 vs DM+L-EMPA, n = 5-7). Empagliflozin restored high glucose-induced downregulation of Sirt1, Nrf2, and BK-ß1, while the effect of empagliflozin disappeared in the presence of EX-527, a Sirt1 selective inhibitor. Conclusion: Empagliflozin has a vasodilation effect on the coronary arteries in a concentration-dependent manner and can activate BK channels via the Sirt1-Nrf2 mechanism.

Symptom-to-balloon time and risk of ventricular arrhythmias in patients with STEMI undergoing percutaneous coronary intervention: The VERY-STEMI study.

Background: Ventricular arrhythmias (VAs) mainly occur in the early post-myocardial infarction (MI) period. However, studies examining the association between total myocardial ischemia time interval and the risk of new-onset VAs during a long-term follow-up are scarce. Methods: This study (symptom-to-balloon time and VEntricular aRrhYthmias in patients with STEMI, VERY-STEMI study) was a multicenter, observational cohort and real-world study, which included patients with ST-segment elevation MI (STEMI) undergoing percutaneous coronary intervention (PCI). The primary endpoint was cumulative new-onset VAs during follow-up. The secondary endpoints were the major adverse cardiovascular events (MACE) and changes in left ventricular ejection fraction (ΔLVEF, %). Results: A total of 517 patients with STEMI were included and 236 primary endpoint events occurred. After multivariable adjustments, compared to patients with S2BT of 24 h-7d, those with S2BT ≤ 24 h and S2BT > 7d had a lower risk of primary endpoint. RCS showed an inverted U-shaped relationship between S2BT and the primary endpoint, with an S2BT of 68.4 h at the inflection point. Patients with S2BT ≤ 24 h were associated with a lower risk of MACE and a 4.44 increase in LVEF, while there was no significant difference in MACE and LVEF change between the S2BT > 7d group and S2BT of 24 h-7d group. Conclusions: S2BT of 24 h-7d in STEMI patients was associated with a higher risk of VAs during follow-up. There was an inverted U-shaped relationship between S2BT and VAs, with the highest risk at an S2BT of 68.4 h.

Identification of key immune-related genes in dilated cardiomyopathy using bioinformatics analysis.

Dilated cardiomyopathy (DCM) is characterized by the left ventricular dilatation and impaired myocardial systolic dysfunction with high mortality and morbidity. However, the underlying mechanisms remain elusive. We first identified the differentially expressed genes (DEGs) between the DCM and control group using two expression profiles from GSE3585 and GSE84796. Enrichment analysis was conducted to explore the potential mechanisms underlying DCM. A total of four algorithms, including key module of MCODE, degree, maximum neighborhood component (MNC), and maximal clique centrality (MCC), were used to identify the hub genes within Cytoscape. The correlation between hub genes and infiltrated immune cells was evaluated to determine potential immune-related genes. The expression analysis and diagnosis value analysis of potential immune-related genes were performed. Finally, the expression analysis with GSE57338 and relationship analysis with the comparative toxicogenomics database (CTD) were performed to identify the key immune-related genes in DCM. A total of 80 DEGs were screened for DCM. Enrichment analysis revealed that DEGs were involved in the immune-related pathological process. Immune infiltration analysis indicated a potentially abnormal immune response in DCM. Four up-regulated genes (COL1A2, COL3A1, CD53, and POSTN) were identified as potential immune-related genes. Finally, three genes (COL1A2, COL3A1, and POSTN) were determined as the key immune-related genes in DCM via expression analysis with a validation set (GSE57338) and relationship analysis with CTD. Our study suggested that the upregulated COL1A2, COL3A1, and POSTN might be the key immune-related genes for DCM. Further studies are needed to validate the underlying mechanisms.

Advanced Glycation End Products Downregulate Connexin 43 and Connexin 40 in Diabetic Atrial Myocytes via the AMPK Pathway.

Purpose: Diabetes mellitus is an independent risk factor for atrial fibrillation (AF), which may be related to accumulation of advanced glycation end products (AGEs). However, the mechanisms involved are not completely clear. Abnormality of gap junction proteins, especially connexin 43 (Cx43) and connexin 40 (Cx40) in atrial myocytes, is an important cause of increased susceptibility of AF. The aim of our work is to investigate the mechanism of dysregulated Cx43 and Cx40 in atrial myocytes of diabetic rats. Methods: We established a type 1 diabetic rat model by intraperitoneal injection of streptozotocin. HL-1 cells and primary rat atrial myocytes were treated with AGEs in vitro. Using Western blotting, immunofluorescence staining, immunohistochemistry, and lucifer yellow diffusion measurements, we investigated dysregulation of Cx43 and Cx40 and its mechanism in atrial myocytes of diabetic rats. Results: Accumulation of AGEs was found in diabetic rats. The expression of Cx43 and Cx40 was reduced in the atrium of diabetic rats, accompanied by the decrease of phosphorylated Adenosine 5'-monophosphate-activated protein kinase (p-AMPK). Similar results were found in cultured HL-1 cells and primary rat atrial myocytes, suggesting a role of AGEs on gap junction proteins. An AMPK agonist, 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR), reversed the down-regulated Cx43 expression induced by AGEs stimulation. More importantly, lucifer yellow diffusion assay showed that AGEs significantly affected gap junctional function, and these changes were reversed by AICAR. Conclusion: Thus, we conclude that AGEs cause dysregulation of Cx43 and Cx40 in diabetic atria via the AMPK pathway, thereby leading to gap junction dysfunction, which may contribute to the increased AF susceptibility in diabetes.