α-adrenoceptor-mediated enhanced inducibility of atrial fibrillation in a canine system inflammation model

Association of lipopolysaccharide with new-onset atrial fibrillation in ST-segment elevation myocardial infarction

Background

Lipopolysaccharide (LPS) is related to various cardiovascular diseases. However, the relationship between LPS and new-onset atrial fibrillation (NOAF) after ST-segment elevation myocardial infarction (STEMI) has yet to be elucidated. This study aimed to evaluate the impact of LPS on NOAF in STEMI patients.

Methods

This was a single-center retrospective observational study including 806 patients diagnosed with STEMI. LPS levels were determined using a commercial ELISA kit. NOAF was characterized by postadmission AF with the absence of any prior history of AF.

Results

A total of 806 participants were enrolled, with 752 individuals in the non-AF group (93.3%) and 54 individuals in the AF group (6.7%). Multivariable analysis showed that LPS (OR = 1.047; 95% CI: 1.029-1.065, P < 0.001) was an independent risk marker for NOAF. The analysis of the ROC demonstrated that LPS had an AUC of 0.717 in predicting NOAF. When LPS was added to the conventional model, the ability of the risk model to discriminate and reclassify NOAF was improved significantly (IDI 0.053, P = 0.001; NRI 0.510, P < 0.001).

Conclusion

Elevated LPS is associated with an increased risk of NOAF in STEMI patients. The integration of LPS can improve the ability to predict NOAF in STEMI patients.

Targeting gut microbiota in aging-related cardiovascular dysfunction: focus on the mechanisms

The global population is aging and age-related cardiovascular disease is increasing. Even after controlling for cardiovascular risk factors, readmission and mortality rates remain high. In recent years, more and more in-depth studies have found that the composition of the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO), bile acids (BAs), and short-chain fatty acids (SCFAs), affect the occurrence and development of age-related cardiovascular diseases through a variety of molecular pathways, providing a new target for therapy. In this review, we discuss the relationship between the gut microbiota and age-related cardiovascular diseases, and propose that the gut microbiota could be a new therapeutic target for preventing and treating cardiovascular diseases.

Gut microbiota and cardiac arrhythmia

One of the most prevalent cardiac diseases is cardiac arrhythmia, however the underlying causes are not entirely understood. There is a lot of proof that gut microbiota (GM) and its metabolites have a significant impact on cardiovascular health. In recent decades, intricate impacts of GM on cardiac arrythmia have been identified as prospective approaches for its prevention, development, treatment, and prognosis. In this review, we discuss about how GM and its metabolites might impact cardiac arrhythmia through a variety of mechanisms. We proposed to explore the relationship between the metabolites produced by GM dysbiosis including short-chain fatty acids(SCFA), Indoxyl sulfate(IS), trimethylamine N-oxide(TMAO), lipopolysaccharides(LPS), phenylacetylglutamine(PAGln), bile acids(BA), and the currently recognized mechanisms of cardiac arrhythmias including structural remodeling, electrophysiological remodeling, abnormal nervous system regulation and other disease associated with cardiac arrythmia, detailing the processes involving immune regulation, inflammation, and different types of programmed cell death etc., which presents a key aspect of the microbial-host cross-talk. In addition, how GM and its metabolites differ and change in atrial arrhythmias and ventricular arrhythmias populations compared with healthy people are also summarized. Then we introduced potential therapeutic strategies including probiotics and prebiotics, fecal microbiota transplantation (FMT) and immunomodulator etc. In conclusion, the GM has a significant impact on cardiac arrhythmia through a variety of mechanisms, offering a wide range of possible treatment options. The discovery of therapeutic interventions that reduce the risk of cardiac arrhythmia by altering GM and metabolites is a real challenge that lies ahead.

Gut Microbiota and Atrial Fibrillation: Pathogenesis, Mechanisms and Therapies

Over the past decade there has been an interest in understanding the role of gut microbiota in the pathogenesis of AF. A number of studies have linked the gut microbiota to the occurrence of traditional AF risk factors such as hypertension and obesity. However, it remains unclear whether gut dysbiosis has a direct effect on arrhythmogenesis in AF. This article describes the current understanding of the effect of gut dysbiosis and associated metabolites on AF. In addition, current therapeutic strategies and future directions are discussed.

Gut Molecules in Cardiometabolic Diseases: The Mechanisms behind the Story

Atherosclerotic cardiovascular disease is the most common cause of morbidity and mortality worldwide. Diabetes mellitus increases cardiovascular risk. Heart failure and atrial fibrillation are associated comorbidities that share the main cardiovascular risk factors. The use of incretin-based therapies promoted the idea that activation of alternative signaling pathways is effective in reducing the risk of atherosclerosis and heart failure. Gut-derived molecules, gut hormones, and gut microbiota metabolites showed both positive and detrimental effects in cardiometabolic disorders. Although inflammation plays a key role in cardiometabolic disorders, additional intracellular signaling pathways are involved and could explain the observed effects. Revealing the involved molecular mechanisms could provide novel therapeutic strategies and a better understanding of the relationship between the gut, metabolic syndrome, and cardiovascular diseases.

Serum Lipopolysaccharide Is Associated with the Recurrence of Atrial Fibrillation after Radiofrequency Ablation by Increasing Systemic Inflammation and Atrial Fibrosis

Objectives

The gut microbiota and its metabolites are linked to inflammation and contribute to the progression of atrial fibrillation (AF), but the predictive value of the gut microbiota-derived metabolite lipopolysaccharide (LPS) for AF recurrence (RAF) is unknown. This study is aimed at investigating (1) the correlation between LPS and RAF and (2) its relationship with inflammation and atrial fibrosis.

Method

We performed a single-centre retrospective analysis in 159 AF patients. Fasting plasma samples were collected, and an enzyme-linked immunosorbent assay was used to determine the levels of serum LPS, interleukin-6 (IL-6), collagen type-1 C-terminal telopeptide (CITP), and transforming growth factor-β1 (TGFβ1). The cumulative risk for RAF was evaluated with Kaplan–Meier analysis. Cox proportional hazard analysis was carried out to predict the hazard of RAF. The correlations among LPS and IL-6, CITP, TGFβ1, and left atrial diameter (LAD) were analysed by Pearson's correlation coefficient. Subsequent univariate and multivariable linear regression analyses were carried out to evaluate the connection between clinical variables and Log-LPS.

Results

All 159 AF patients were included in this study. The proportion of persistent atrial fibrillation was 40.3%, the mean age was 61.9 ± 10.1 years, the proportion of males was 61.6%, and the mean LPS was 56.5 ± 29.5 pg/mL. After all patients were divided into tertiles according to the circulating LPS level, a total of 44 RAF occurred: 10 in the first tertile, 15 in the second tertile, and 19 in the third tertile (log-rank test P = 0.037). Heart failure (hazard ratio 2.029, P = 0.041), LAD (hazard ratio 1.064, P = 0.022), Log-LPS (hazard ratio 5.686, P = 0.043), and CITP (hazard ratio 6.841, P = 0.033) independently predicted the risk of RAF. In all patients, univariate analysis showed that heart failure, LAD, hs-CRP, IL-6, CITP, and TGF-β1 were connected with Log-LPS. Multivariate linear regression analysis indicated that IL-6 and hs-CRP were independently and positively connected with Log-LPS.

Conclusions

Our results indicated that circulating LPS was a predictor of RAF and may contribute to RAF incidence after ablation by increasing systemic inflammation and atrial fibrosis.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

Muscarinic receptor regulation of chronic pain-induced atrial fibrillation

Atrial fibrillation (AF), one of the most common arrhythmias, is associated with chronic emotional disorder. Chronic pain represents a psychological instability condition related to cardiovascular diseases, but the mechanistic linkage connecting chronic pain to AF occurrence remains unknown. Wild-type C57BL/6J male mice were randomly divided into sham and chronic pain groups. Autonomic nerve remodeling was reflected by the increased atrial parasympathetic tension and muscarinic acetylcholine receptor M2 expression. AF susceptibility was assessed through transesophageal burst stimulation in combination with electrocardiogram recording and investigating AERP in Langendorff perfused hearts. Our results demonstrated the elevated protein expression of muscarinic acetylcholine receptor M2 in the atria of mice subjected to chronic pain stress. Moreover, chronic pain induced the increase of atrial PR interval, and atrial effective refractory periods as compared to the sham group, underlying the enhanced susceptibility of AF. Thus, autonomic cholinergic nerve may mediate mice AF in the setting of chronic pain.

Gut microbiota, dysbiosis and atrial fibrillation. Arrhythmogenic mechanisms and potential clinical implications

Recent preclinical and observational cohort studies have implicated imbalances in gut microbiota composition as a contributor to atrial fibrillation (AF). The gut microbiota is a complex and dynamic ecosystem containing trillions of microorganisms, which produces bioactive metabolites influencing host health and disease development. In addition to host-specific determinants, lifestyle-related factors such as diet and drugs are important determinants of the gut microbiota composition. In this review, we discuss the evidence suggesting a potential bidirectional association between AF and gut microbiota, identifying gut microbiota-derived metabolites as possible regulators of the AF substrate. We summarize the effect of gut microbiota on the development and progression of AF risk-factors, including heart failure, hypertension, obesity and coronary artery disease. We also discuss the potential antiarrhythmic effects of pharmacological and diet-induced modifications of gut microbiota composition, which may modulate and prevent the progression to AF. Finally, we highlight important gaps in knowledge and areas requiring future investigation. Although data supporting a direct relationship between gut microbiota and AF are very limited at the present time, emerging preclinical and clinical research dealing with mechanistic interactions between gut microbiota and AF is important as it may lead to new insights into AF pathophysiology and the discovery of novel therapeutic targets for AF.

Sugar Fructose Triggers Gut Dysbiosis and Metabolic Inflammation with Cardiac Arrhythmogenesis

Fructose is a main dietary sugar involved in the excess sugar intake-mediated progression of cardiovascular diseases and cardiac arrhythmias. Chronic intake of fructose has been the focus on the possible contributor to the metabolic diseases and cardiac inflammation. Recently, the small intestine was identified to be a major organ in fructose metabolism. The overconsumption of fructose induces dysbiosis of the gut microbiota, which, in turn, increases intestinal permeability and activates host inflammation. Endotoxins and metabolites of the gut microbiota, such as lipopolysaccharide, trimethylamine N-oxide, and short-chain fatty acids, also influence the host inflammation and cardiac biofunctions. Thus, high-fructose diets cause heart-gut axis disorders that promote cardiac arrhythmia. Understanding how gut microbiota dysbiosis-mediated inflammation influences the pathogenesis of cardiac arrhythmia may provide mechanisms for cardiac arrhythmogenesis. This narrative review updates our current understanding of the roles of excessive intake of fructose on the heart-gut axis and proposes potential strategies for inflammation-associated cardiac vascular diseases.

Expression of Toll-Like Receptors in the Animal Model of Bladder Outlet Obstruction

Introduction

Bladder outlet obstruction (BOO) occurs in more than 20 percent of the adult population and may lead to changes in the structure and function of the bladder. The main objective of the study was to evaluate the expression of Toll-like receptor 4 (TLR 4) and Toll-like receptor 9 (TLR 9) in the animal model of BOO as potential triggers of the inflammation phase in the bladder. In addition, the modulating effect of alpha-1 adrenergic antagonist (tamsulosin) on TLR 4 and TLR 9 expression and inflammatory markers was assessed. Material and Methods. Thirty-two male, 9-week-old Sprague Dawley rats were randomly divided into 4 groups: SOP—sham-operated rats with a placebo (water); SOB—sham-operated rats with an alpha-1 adrenergic antagonist; BOOP—rats with BOO and a placebo; and BOOB—rats with BOO and an alpha-1 adrenergic antagonist. The rats were given a placebo or alpha-1 adrenergic antagonist for 15 days. Next, urine and the bladder were collected from the rats for histopathological and biochemical study.

Results

Histopathological analysis showed chronic inflammation without acute inflammation in the bladder. TLR 4 showed positive cytoplasmic reactivity in the urothelium and the smooth muscles of the bladder. TLR 9 showed positive cytoplasmic reactivity only in the urothelium. BOO caused an increase in TLR 4 and TLR 9 expression. Furthermore, treatment with an alpha-1 adrenergic antagonist had no significant effect on TLR 4 and TLR 9 expression in rats with BOO. BOO caused a significant increase in urine concentration of interleukin 6 (IL-6), while alpha-1 antagonist reduced the urine concentration of IL-6 and the concentration of interleukin 18 (IL-18).

Conclusions

The results suggest the participation of TLR 4 and TLR 9 receptors in the induction of inflammation in the bladder, which is the first phase in the development of pathophysiological changes in BOO.