Chronic kidney disease-induced atrial structural remodeling and atrial fibrillation: more studies on the pathological mechanism are encouraged

Aging and atrial fibrillation: A vicious circle

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia observed in clinical practice. Its prevalence increases dramatically with advancing age. This review article discusses the recent advances in studies investigating the relationship between aging and AF and the possible underlying mechanisms.

ROS-Activated TRPM2 Channel: Calcium Homeostasis in Cardiovascular/renal System and Speculation in Cardiorenal Syndrome

The transient receptor potential melastatin 2 (TRPM2) channel is a nonselective calcium channel that is sensitive to oxidative stress (OS), and is widely expressed in multiple organs, such as the heart, kidney, and brain, which is inextricably related to calcium dyshomeostasis and downstream pathological events. Due to the increasing global burden of kidney or cardiovascular diseases (CVDs), safe and efficient drugs specific to novel targets are imperatively needed. Notably, investigation of the possibility to regard the TRPM2 channel as a new therapeutic target in ROS-related CVDs or renal diseases is urgently required because the roles of the TRPM2 channel in heart or kidney diseases have not received enough attention and thus have not been fully elaborated. Therefore, we aimed to review the involvement of the TRPM2 channel in cardiovascular disorders related to kidney or typical renal diseases and attempted to speculate about TRPM2-mediated mechanisms of cardiorenal syndrome (CRS) to provide representative perspectives for future research about novel and effective therapeutic strategies.

Pathophysiology of atrial fibrillation and chronic kidney disease

Atrial fibrillation (AF) and chronic kidney disease (CKD) are closely related conditions with shared risk factors. The growing prevalence of both AF and CKD indicates that more patients will suffer from concurrent conditions. There are various complex interlinking mechanisms with important implications for the management of these patients. Furthermore, there is uncertainty regarding the use of oral anticoagulation (OAC) in AF and CKD that is reflected by a lack of consensus between international guidelines. Therefore, the importance of understanding the implications of co-existing AF and CKD should not be underestimated. In this review, we discuss the pathophysiology and association between AF and CKD, including the underlying mechanisms, risk of thrombo-embolic and bleeding complications, influence on stroke management, and evidence surrounding the use of OAC for stroke prevention.

Significance of serum fibroblast growth factor-23 and miR-208b in pathogenesis of atrial fibrillation and their relationship with prognosis

BACKGROUND

The incidence and prevalence of atrial fibrillation are increasing each year, and this condition is one of the most common clinical arrhythmias.

AIM

To investigate the levels and significance of serum fibroblast growth factor 23 (FGF-23) and miR-208b in patients with atrial fibrillation and their relationship with prognosis.

METHODS

From May 2018 to October 2019, 240 patients with atrial fibrillation were selected as an observation group, including 134 with paroxysmal atrial fibrillation and 106 with persistent atrial fibrillation; 150 patients with healthy sinus rhythm were selected as a control group. The serum levels of FGF-23 and miR-208b in the two groups were measured. In the observation group, cardiac parameters were determined by echocardiography.

RESULTS

The serum levels of FGF-23 and miR-208b in the observation group were 210.20 ± 89.60 ng/mL and 5.30 ± 1.22 ng/mL, which were significantly higher than the corresponding values in the control group (P < 0.05). In the observation group, the serum levels of FGF-23 and miR-208b in patients with persistent atrial fibrillation were 234.22 ± 70.05 ng/mL and 5.83 ± 1.00 ng/mL, which were significantly higher than the corresponding values in patients with paroxysmal atrial fibrillation (P < 0.05). The left atrial dimension (LAD) of patients with persistent atrial fibrillation was 38.81 ± 5.11 mm, which was significantly higher than that of patients with paroxysmal atrial fibrillation (P > 0.05). The serum levels of FGF-23 and miR-208b were positively correlated with the LAD (r = 0.411 and 0.382, P < 0.05). In the observation group, the serum levels of FGF-23 and miR-208b in patients with a major cardiovascular event (MACE) were 243.30 ± 72.29 ng/mL and 6.12 ± 1.12 ng/mL, which were significantly higher than the corresponding values in patients without a MACE (P < 0.05).

CONCLUSION

The serum levels of FGF-23 and miR-208b are increased in patients with atrial fibrillation and are related to the type of disease, cardiac parameters, and prognosis.

Chronic Kidney Disease Increases Atrial Fibrillation Inducibility: Involvement of Inflammation, Atrial Fibrosis, and Connexins

Chronic kidney disease (CKD) causes atrial structural remodeling and subsequently increases the incidence of atrial fibrillation (AF). Atrial connexins and inflammatory responses may be involved in this remodeling process. In this study, nephrectomy was used to produce the CKD rat model. Three months post-nephrectomy, cardiac structure, function and AF vulnerability were quantified using echocardiography and electrophysiology methods. The left atrial tissue was tested for quantification of fibrosis and inflammation, and for the distribution and expression of connexin (Cx) 40 and Cx43. An echocardiography showed that CKD resulted in the left atrial enlargement and left ventricular hypertrophy, but had no functional changes. CKD caused a significant increase in the AF inducible rate (91.11% in CKD group vs. 6.67% in sham group, P < 0.001) and the AF duration [107 (0–770) s in CKD vs. 0 (0–70) s in sham, P < 0.001] with prolonged P-wave duration. CKD induced severe interstitial fibrosis, activated the transforming growth factor-β1/Smad2/3 pathway with a massive extracellular matrix deposition of collagen type I and α-smooth muscle actin, and matured the NLR (nucleotide-binding domain leucine-rich repeat-containing receptor) pyrin domain-containing protein 3 (NLRP3) inflammasome with an inflammatory cascade response. CKD resulted in an increase in non-phosphorylated-Cx43, a decrease in Cx40 and phosphorylated-Cx43, and lateralized the distribution of Cx40 and Cx43 proteins with upregulations of Rac-1, connective tissue growth factor and N-cadherin. These findings implicate the transforming growth factor-β1/Smad2/3, the NLRP3 inflammasome and the connexins as potential mediators of increased AF vulnerability in CKD.