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Background The gut microbiota provides health benefits in humans by producing short-chain fatty acids (SCFAs), whose deficiency causes multiple disorders and inflammatory diseases. However, gut bacteria producing SCFAs in patients with atrial fibrillation (AF), an arrhythmia with increasing prevalence, have not been reported. To investigate major gut microbial organisms related to SCFA synthesis, SCFAs-associated KEGG orthologues (KOs), enzymatic genes, and potential producers were examined according to metagenomic data-mining in a northern Chinese cohort comprising 50 non-AF control and 50 AF patients. Results Compared with non-AF controls, individuals with AF had marked differences in microbial genes involved in SCFA-related synthesis, including 125 KOs and 5 SCFAs-related enzymatic genes. Furthermore, there were 10 species that harbored SCFA-synthesis related enzymatic genes, and were markedly decreased in the gut of AF patients. Notably, discriminative features about SCFA-synthesis related function, including 8 KOs (K01752, K01738, K00175, K03737, K01006, K01653, K01647 and K15023), 4 genes ( menI , tesB , yciA and CO dehydrogenase acetyl-CoA synthase complex ) and 2 species ( Coprococcus catus and Firmicutes bacterium CAG:103 ), were selected as key factors based on LASSO analysis. Furthermore, PLS-SEM analysis showed that 72.8 and 91.14 % of the overall effects on gut microbiota diversity and key species on AF, respectively, were mediated by the key KOs. Meanwhile, 46.31 % of the total effects of SCFA-synthesis related function on left atrial enlargement was mediated by hsCRP. Upon incorporation of clinical properties in AF, the KO score was still significantly associated with AF incidence (OR = 0.004, P = 0.001). Conclusions The current study revealed that dysbiotic gut microbiota in AF is coupled with disrupted SCFA-synthesis related genes, characterized by decreased abundances of KEGG orthologues, synthesis enzymatic genes and harboring species.

Background The gut bacteria-derived metabolite trimethylamine-N-oxide (TMAO) has been discussed in various cardiometabolic diseases. However, evidence characterizing the microbial population responsible for TMAO accumulation in patients with atrial fibrillation (AF), an increasingly prevalent arrhythmia, is yet lacking. In order to understand the key gut microorganisms that produce TMAO in AF, trimethylamine (TMA)-synthesis enzymes and metabolic pathways, as well as the potential TMA-producers in gut microbiome were assessed based on metagenomic data-mining in a northern Chinese cohort consisting of 50 non-AF controls and 50 patients with different types of AF. Results Compared to the control subjects, AF patients showed a marked increase in the microbial genes underlying TMA formation in the gut, which included 12 potential TMA-synthesis functional orthologs and 1 module. The specific bacterial genes, including choline-TMA lyase , carnitine monooxygenase , glycine betaine reductase , and TMAO reductase , were elevated in the gut of AF patients. Furthermore, 16 genera were assigned and significantly correlated with TMA-enzymatic genes, where 9 genera were remarkably enriched in the gut communities of AF patients. Neither of these TMA-synthesis pathways nor the microbial players showed a significant discrepancy between different types of AF in the current cohort. These gut microbes might participate in the formation of TMA by activating the key TMA-synthesis enzymes and contributing to the functional pathways in AF patients. Conclusions The present study provides an in-depth insight into the potential bacteria and metabolic pathways involved in TMA production in the gut of AF patients. These findings emphasize a key role of the gut bacteria in driving TMAO formation during AF pathogenesis, thereby indicating its therapeutic potential as an intervention strategy of AF by targeting TMA-synthesis pathways and dysbiotic gut microbiota.

Atrial fibrillation was associated with a disordered gut microbiota in previous research. However, the gut microbiota signature of patients at different stages of atrial fibrillation remains largely unknown. We sought to determine whether the shift in the gut microbiota and metabolic profiles occurs early and remains stable or develops gradually during atrial fibrillation. We found that patients with persistent atrial fibrillation of <12 months and persistent atrial fibrillation of >12 months shared most of the common features of gut microbiota dysbiosis. However, some distinctive and progressive alterations in the gut microbiota and metabolic structure, which may contribute to the progression of atrial fibrillation, were identified. The present study provides a comprehensive description of the dysbiotic gut microbiota and metabolic profiles in patients of short and long persistent atrial fibrillation, and our findings may help identify therapeutic strategies targeting the gut microbiota to treat atrial fibrillation at an early stage. Atrial fibrillation (AF) has been shown to be associated with disordered gut microbiota (GM). The underlying factors governing persistent AF (psAF) are not well understood, and the association between AF duration and GM profiles remains to be characterized. Thus, the present study aimed at investigating the dysbiosis of GM in patients with short and long psAF duration and illuminating the relationship between the GM and psAF maintenance. Based on metagenomic sequencing and metabolomic analyses, we assessed the metabolic and GM signature in 12 patients with psAF of <12 months (Pers<12m), eight patients with psAF of >12 months (Pers>12m), and 20 controls. We found that the GM in patients with both Pers<12m and Pers>12m was significantly perturbed, with an elevated microbial diversity, distinct structure, and discrepant composition. Although Pers<12m and Pers>12m patients shared a large number of common bacteria with controls, including 84 genera and 404 species, certain bacteria were differently enriched at different AF durations. Furthermore, disturbance in gut microbial function and GM-linked metabolic alterations were detected in both the Pers<12m and Pers>12m groups. The connection of GM and metabolites with psAF is consistent with interaction and potential modulation of host metabolic pathways due to GM dysbiosis with AF persistence. Our results showed that patients of the Pers<12m and Pers>12m groups shared many common disordered GM and metabolic features, which might occur in early disease, while prolonged psAF duration was related to certain unique alterations. Preventative strategies targeting GM and microbial metabolites for early intervention to treat AF patients are highly warranted. IMPORTANCE Atrial fibrillation was associated with a disordered gut microbiota in previous research. However, the gut microbiota signature of patients at different stages of atrial fibrillation remains largely unknown. We sought to determine whether the shift in the gut microbiota and metabolic profiles occurs early and remains stable or develops gradually during atrial fibrillation. We found that patients with persistent atrial fibrillation of <12 months and persistent atrial fibrillation of >12 months shared most of the common features of gut microbiota dysbiosis. However, some distinctive and progressive alterations in the gut microbiota and metabolic structure, which may contribute to the progression of atrial fibrillation, were identified. The present study provides a comprehensive description of the dysbiotic gut microbiota and metabolic profiles in patients of short and long persistent atrial fibrillation, and our findings may help identify therapeutic strategies targeting the gut microbiota to treat atrial fibrillation at an early stage.

Atrial fibrillation has been identified to be associated with disordered gut microbiota. Notably, atrial fibrillation is a progressive disease and could be categorized as paroxysmal and persistent based on the duration of the episodes. The persistent atrial fibrillation patients are accompanied by higher risk of stroke and lower success rate of rhythm control. However, the microbial signatures of different categories of atrial fibrillation patients remain unknown. We sought to determine whether disordered gut microbiota occurs in the self-terminating PAF or intestinal flora develops dynamically during atrial fibrillation progression. We found that different types of atrial fibrillation show a limited degree of gut microbiota shift. Gut microbiota dysbiosis has already occurred in mild stages of atrial fibrillation, which might act as an early modulator of disease, and therefore may be regarded as a potential target to postpone atrial fibrillation progression. Dysbiotic gut microbiota (GM) and disordered metabolic patterns are known to be involved in the clinical expression of atrial fibrillation (AF). However, little evidence has been reported in characterizing the specific changes in fecal microbiota in paroxysmal AF (PAF) and persistent AF (psAF). To provide a comprehensive understanding of GM dysbiosis in AF types, we assessed the GM signatures of 30 PAF patients, 20 psAF patients, and 50 non-AF controls based on metagenomic and metabolomic analyses. Compared with control subjects, similar changes of GM were identified in PAF and psAF patients, with elevated microbial diversity and similar alteration in the microbiota composition. PAF and psAF patients shared the majority of differential taxa compared with non-AF controls. Moreover, the similarity was also illuminated in microbial function and associated metabolic alterations. Additionally, minor disparity was observed in PAF compared with psAF. Several distinctive taxa between PAF and psAF were correlated with certain metabolites and atrial diameter, which might play a role in the pathogenesis of atrial remodeling. Our findings characterized the presence of many common features in GM shared by PAF and psAF, which occurred at the self-terminating PAF. Preventative and therapeutic measures targeting GM for early intervention to postpone the progression of AF are highly warranted. IMPORTANCE Atrial fibrillation has been identified to be associated with disordered gut microbiota. Notably, atrial fibrillation is a progressive disease and could be categorized as paroxysmal and persistent based on the duration of the episodes. The persistent atrial fibrillation patients are accompanied by higher risk of stroke and lower success rate of rhythm control. However, the microbial signatures of different categories of atrial fibrillation patients remain unknown. We sought to determine whether disordered gut microbiota occurs in the self-terminating PAF or intestinal flora develops dynamically during atrial fibrillation progression. We found that different types of atrial fibrillation show a limited degree of gut microbiota shift. Gut microbiota dysbiosis has already occurred in mild stages of atrial fibrillation, which might act as an early modulator of disease, and therefore may be regarded as a potential target to postpone atrial fibrillation progression.

To improve the production process and produce high-quality annealed drawn and ironed (DI) plate, continuous annealing experiments were carried out at 620 °C, 640 °C, 680 °C, and 720 °C, and the effect of continuous annealing temperature on the microstructure, mechanical characteristics, and texture of annealed DI plate were clarified. The microstructure was tested with a scanning electron microscope (SEM); the mechanical properties and weighted average of the plastic strain ratio (r¯) were measured using a tension test; and the texture characterizations were tested by X-ray powder diffractometer (XRD) and electron backscatter diffraction (EBSD). The results reveal that, with the increase of the annealing temperature, the average grain size grew from 5.14 μm to 6.56 μm, the yield strength and tensile strength decreased, and the elongation increased. The rolling textures drastically reduced after annealing. When annealed at a lower temperature of 620 °C, the texture content of 111 was the highest. When the annealing temperature increased to 640 °C, 680 °C and 720 °C, the texture content of 111 was higher than that of 111 . The mechanical properties of the DI plate that was annealed at 640 °C are the best, with a higher r¯ value and a lower planar anisotropy value.

This study examined the effect of sleep disturbance on gut microbiota (GM), atrial substrate, and atrial fibrillation (AF) inducibility. C57BL/6 mice were subjected to six weeks of sleep deprivation (SD) using the method of modified multiple-platform. Transesophageal burst pacing was performed to evaluate AF inducibility. Feces, plasma, and an atrium were collected and analyzed by 16s rRNA sequencing, liquid chromatography–mass spectrometry (LC-MS)-based metabolome, histological studies, and transcriptome. Higher AF inducibility (2/30 of control vs. 15/30 of SD, p = 0.001) and longer AF duration (p < 0.001), concomitant with aggravated fibrosis, collagen, and lipid accumulation, were seen in the SD mice compared to control mice. Meanwhile, elevated alpha diversity, higher abundance of Flavonifractor, Ruminococcus, and Alloprevotella, as well as imbalanced functional pathways, were observed in the gut of SD mice. Moreover, the global patterns for the plasma metabolome were altered, e.g., the decreased butanoate metabolism intermediates in SD mice. In addition, disrupted metabolic homeostasis in the SD atrium, such as fatty acid metabolism, was analyzed by the transcriptome. These results demonstrated that the crosstalk between GM and atrial metabolism might be a promising target for SD-mediated AF susceptibility.

Background: Low-voltage zones (LVZs) were usually targeted for ablation in atrial fibrillation (AF). However, its relationship with AF initiation, perpetuation, and termination remains to be studied. This study aimed to explore such relationships. Methods: A total of 126 consecutive AF patients were enrolled, including 71 patients for AF induction protocol and 55 patients for AF termination protocol. Inducible and sustainable AF were defined as induced AF lasting over 30 and 300 s, respectively. Terminable AF was defined as those that could be terminated into sinus rhythm within 1 h after ibutilide administration. Voltage mapping was performed in sinus rhythm for all patients. LVZ was quantified as the percentage of the LVZ area (LVZ%) to the left atrium surface area. Results: The rates of inducible, sustainable, and terminable AF were 29.6, 18.3, and 38.2%, respectively. Inducible AF patients had no significant difference in overall LVZ% compared with uninducible AF patients (10.2 ± 11.8 vs. 8.5 ± 12.6, p = 0.606), while sustainable and interminable AF patients had larger overall LVZ% than unsustainable (16.2 ± 11.5 vs. 0.5 ± 0.7, p < 0.001) and terminable AF patients (44.6 ± 26.4 vs. 26.3 ± 22.3, p < 0.05), respectively. The segmental LVZ distribution pattern was diverse in the different stages of AF. Segmental LVZ% difference was initially observed in the anterior wall for patients with inducible AF, and the septum was further affected in those with sustainable AF, and the roof, posterior wall, and floor were finally affected in those with interminable AF. Conclusions: The associations between LVZ with AF initiation, perpetuation, and termination were different depending on its size and distribution.

Rationale: Dysbiotic gut microbiota (GM) and NLRP3 inflammasome are proarrhythmic factors in atrial fibrillation (AF). Herein, whether short-chain fatty acid (SCFA) produced from GM fermentation of dietary fiber serving as invisible mediators is yet unclear. Thus, the current study aimed to determine whether SCFA alleviated from NLRP3 signaling-mediated atrial remodeling protects AF development. Methods: First, a cross-sectional study based on the GC-MS metabolomics was performed to explore the association between fecal SCFA levels and AF traits in a cohort consisted of 48 individuals. Then, a well-established mice model fed diet deficient or enriched in dietary fiber was established to elucidate the pathophysiological role of SCFA involved in AF susceptibility, atrial remodeling, and G-protein-coupled receptor 43 (GPR43)/NLRP3 signaling. Finally, the effects of SCFA were verified on HL-1 cells. Results: Fecal SCFA levels were remarkably reduced in AF patients with a declining trend from paroxysmal to persistent AF. Prolonged P wave duration based on surface ECG and increased left atrial diameter gained from echocardiography was identified in low-fiber diet mice but lost in SCFA-supplemented group. Lack of dietary fiber enhanced susceptibility to AF under burst pacing, whereas SCFA might exert a protective effect. The supplementation of SCFA prevented dietary fiber deficiency-upregulated phosphorylation of calmodulin-dependent protein kinase II and ryanodine receptor 2, the disarray fibrosis, collagen expression, and NLRP3 inflammasome activation in atrial tissue. Finally, the AF protective roles of SCFA were identified through GPR43 mediated deactivation of NLRP3 by GPR43 knockdown in HL-1 cells. Conclusions: SCFA derived from dietary fiber fermentation by gut commensals alleviates AF development via GPR43/NLRP3 signaling.Rationale: Dysbiotic gut microbiota (GM) and NLRP3 inflammasome are proarrhythmic factors in atrial fibrillation (AF). Herein, whether short-chain fatty acid (SCFA) produced from GM fermentation of dietary fiber serving as invisible mediators is yet unclear. Thus, the current study aimed to determine whether SCFA alleviated from NLRP3 signaling-mediated atrial remodeling protects AF development. Methods: First, a cross-sectional study based on the GC-MS metabolomics was performed to explore the association between fecal SCFA levels and AF traits in a cohort consisted of 48 individuals. Then, a well-established mice model fed diet deficient or enriched in dietary fiber was established to elucidate the pathophysiological role of SCFA involved in AF susceptibility, atrial remodeling, and G-protein-coupled receptor 43 (GPR43)/NLRP3 signaling. Finally, the effects of SCFA were verified on HL-1 cells. Results: Fecal SCFA levels were remarkably reduced in AF patients with a declining trend from paroxysmal to persistent AF. Prolonged P wave duration based on surface ECG and increased left atrial diameter gained from echocardiography was identified in low-fiber diet mice but lost in SCFA-supplemented group. Lack of dietary fiber enhanced susceptibility to AF under burst pacing, whereas SCFA might exert a protective effect. The supplementation of SCFA prevented dietary fiber deficiency-upregulated phosphorylation of calmodulin-dependent protein kinase II and ryanodine receptor 2, the disarray fibrosis, collagen expression, and NLRP3 inflammasome activation in atrial tissue. Finally, the AF protective roles of SCFA were identified through GPR43 mediated deactivation of NLRP3 by GPR43 knockdown in HL-1 cells. Conclusions: SCFA derived from dietary fiber fermentation by gut commensals alleviates AF development via GPR43/NLRP3 signaling.

Alternations of gut microbiota (GM) in atrial fibrillation (AF) with elevated diversity, perturbed composition and function have been described previously. The current work aimed to assess the association of GM composition with AF recurrence (RAF) after ablation based on metagenomic sequencing and metabolomic analyses and to construct a GM‐based predictive model for RAF. Compared with non‐AF controls (50 individuals), GM composition and metabolomic profile were significantly altered between patients with recurrent AF (17 individuals) and non‐RAF group (23 individuals). Notably, discriminative taxa between the non‐RAF and RAF groups, including the families Nitrosomonadaceae and Lentisphaeraceae, the genera Marinitoga and Rufibacter and the species Faecalibacterium spCAG:82, Bacillus gobiensis and Desulfobacterales bacterium PC51MH44, were selected to construct a taxonomic scoring system based on LASSO analysis. After incorporating the clinical factors of RAF, taxonomic score retained a significant association with RAF incidence (HR = 2.647, P = .041). An elevated AUC (0.954) and positive NRI (1.5601) for predicting RAF compared with traditional clinical scoring (AUC = 0.6918) were obtained. The GM‐based taxonomic scoring system theoretically improves the model performance, and the nomogram and decision curve analysis validated the clinical value of the predicting model. These data provide novel possibility that incorporating the GM factor into future recurrent risk stratification.