Permanent atrial fibrillation impairs the function of circulating endothelial progenitor cells

Association between vascular endothelial growth factor and atrial fibrillation: a systematic review

BACKGROUND

Atrial fibrillation (AF) is the most prevalent form of sustained cardiac arrhythmia, with vascular endothelial growth factor (VEGF) increasingly recognized for its potential role in the pathogenesis of AF through mechanisms involving atrial remodeling, inflammation, and fibrosis. This systematic review aims to synthesize available evidence on the association between VEGF and AF, exploring the implications of VEGF as a biomarker and therapeutic target.

METHODS

We conducted a comprehensive search across PubMed, Embase, and Web of Science until November 10 2024, selecting studies based on pre-defined criteria that involve adults with AF and measurements of VEGF levels. The selected studies included observational and experimental designs, excluding non-English and methodologically insufficient publications. Narrative synthesis was used for summarising the results.

RESULTS

Eight studies met the inclusion criteria. The studies show a general trend of elevated VEGF levels in AF patients compared to controls, with significant heterogeneity in findings across studies. VEGF subtypes such as VEGF-A and VEGF-D demonstrated stronger associations with AF risk compared to VEGF-C. These variations point to the complex role of VEGF in AF, influencing factors like angiogenesis, endothelial function, and inflammatory responses.

CONCLUSION

VEGF is potentially a significant contributor to AF pathophysiology, with its levels reflecting disease activity. The variability observed across studies suggests a need for standardized measurement approaches and further investigation into VEGF subtypes. Future research should focus on longitudinal studies to better understand the causal relationships and the potential of VEGF as a therapeutic target and biomarker in AF management.

CLINICAL TRIAL NUMBER

Not applicable.

Causal effect of atrial fibrillation on pulmonary embolism: a mendelian randomization study

Atrial fibrillation (AF) can increase thrombosis, especially arterial thrombosis, and some studies show that AF patients have a higher risk of developing pulmonary embolism (PE). The objective of our study is to investigate whether there is a direct causal effect of AF on PE. A two-sample Mendelian randomization (MR) approach was utilized to determine whether there is a causal relationship between AF and PE. European population-based consortia provided statistical data on the associations between Single Nucleotide Polymorphisms (SNPs) and relevant traits. The AF dataset was obtained from genome-wide association studies (GWAS) comprising 60,620 cases and 970,216 controls, while a GWAS of 1846 cases and 461,164 controls identified genetic variations associated with PE. Estimation of the causal effect was mainly performed using the random effects inverse-variance weighted method (IVW). Additionally, other tests such as MR-Egger intercept, MR-PRESSO, Cochran's Q test, "Leave-one-out," and funnel plots were conducted to assess the extent of pleiotropy and heterogeneity. Using 70 SNPs, there was no evidence to suggest an association between genetically predicted AF and risk of PE with multiplicative random-effects IVW MR analysis (odds ratio = 1.0003, 95% confidence interval: 0.9998-1.0008, P = 0.20). A null association was also observed in other methods. MR-Egger regression and MR-PRESSO respectively showed no evidence of directional (intercept, - 2.25; P = 0.94) and horizontal(P-value in the global heterogeneity test = 0.99) pleiotropic effect across the genetic variants. No substantial evidence was found to support the causal role of AF in the development of PE.

New-Onset Atrial Fibrillation and Adverse In-Hospital Outcome in Patients with Acute Pulmonary Embolism

Atrial fibrillation (AF) can be secondary to acute pulmonary embolism (PE). This study aimed to investigate the prognostic impact of new-onset AF on patients with acute PE. In this study, 4,288 consecutive patients who were diagnosed with acute PE were retrospectively screened. In total, 77 patients with acute PE and new-onset AF were analyzed. Another 154 acute PE patients without AF were selected as the age- and sex-matched control group. Adverse in-hospital outcome comprised one of the following conditions: all-cause death, endotracheal intubation, cardiopulmonary resuscitation, and intravenous catecholamine therapy. The patients with new-onset AF had higher prevalence of congestive heart failure, higher simplified PE severity index (sPESI), higher creatinine, and larger left atrium diameter. The incidences of adverse in-hospital outcomes were 10.4 and 2.6% in patients with new-onset AF and no AF, respectively (p = 0.02). Patients with sPESI ≥ 1 had higher incidence of adverse in-hospital outcomes than those with sPESI = 0 (9.4 vs. 0.9%, p < 0.01). The area under the receiver operating characteristic curve of sPESI and sPESI + AF (adding 1 point for new-onset AF) scores in assessing the adverse in-hospital outcome were 0.80 (95% confidence interval [CI]: 0.68-0.93) and 0.84 (95% CI: 0.72-0.96), respectively. In multivariable analysis, sPESI ≥ 1 (odds ratio, 8.88; 95% CI: 1.10-72.07; p = 0.04) was an independent predictor of adverse in-hospital outcome. However, new-onset AF was not an independent predictor. In the population studied, sPESI is an independent predictor of adverse in-hospital outcomes, whereas new-onset AF following acute PE is not, but it may add predictive value to sPESI.

Effects of Exercise Training on the Paracrine Function of Circulating Angiogenic Cells

Exercise training has various benefits on cardiovascular health, and circulating angiogenic cells have been proposed as executing these changes. Work from the late 1990s supported an important role of these circulating post-natal cells in contributing to the maintenance and repair of the endothelium and vasculature. It was later found that circulating angiogenic cells were a heterogenous population of cells and primarily functioned in a paracrine manner by adhering to damaged endothelium and releasing growth factors. Many studies have discovered novel circulating angiogenic cell secreted proteins, microRNA and extracellular vesicles that mediate their angiogenic potential, and some studies have shown that both acute and chronic aerobic exercise training have distinct benefits. This review highlights work establishing an essential role of secreted factors from circulating angiogenic cells and summarizes studies regarding the effects of exercise training on these factors. Finally, we highlight the various gaps in the literature in hopes of guiding future work.

Does an imbalance in circulating vascular endothelial growth factors (VEGFs) cause atrial fibrillation in patients with valvular heart disease?

Background

The pathogenesis of atrial fibrillation (AF) remains unclear. Vascular endothelial growth factors (VEGFs) can stimulate fibrosis within the atrium and ventricle. We hypothesized that there is a relationship between the serum VEGFs/soluble vascular endothelial growth factor receptor (sVEGFRs) levels and AF in patients with valvular heart disease (VHD). This provides a new paradigm for studying AF.

Methods

The plasma levels of VEGF-A, VEGF-C, sVEGFR-1 and sVEGFR-2 were detected by enzyme-linked immunosorbent assay (ELISA). A total of 100 people, consisting of AF patients (long-standing, persistent AF; n=49), sinus rhythm (SR) patients (n=31) and healthy controls (n=20), were included in this study.

Results

The plasma levels of VEGF-A were significantly higher in AF patients compared to healthy control (P<0.05). The plasma levels of sVEGFR-1 were significantly higher in AF compared to SR (P<0.05). The plasma levels of sVEGFR-2 were significantly lower in AF patients compared to SR patients and healthy controls (both P<0.05). There was a significant and negative correlation between AF and the sVEGFR-2 levels in the groups (r=-0.432, P=0.000).

Conclusions

An imbalance in VEGFs and sVEGFRs may contribute to AF by breaking the balance of angiogenesis and lymphangiogenesis. Additionally, sVEGFR-2 may be an important biomarker of AF.

Hyperinsulinemia impairs functions of circulating endothelial progenitor cells

AIMS

Circulating endothelial progenitor cells (EPCs) play a key role in maintaining endothelial function. Dysfunction of EPCs is associated with the cardiovascular complication of diabetes. The purpose of this study is to investigate the direct effects of hyperinsulinemia on EPCs and the underlying mechanisms.

METHODS

EPCs isolated from healthy adults were cultured with various concentrations of insulin (control group, without insulin; physiological insulin group, 10 nM insulin and hyperinsulinemia group, 100 nM insulin) with or without phosphatidylinositol-3-kinase (PI3-K) inhibitor (LY294002, 5 µM), endothelial nitric oxide synthase (eNOS) inhibitor (L-NG-nitro-arginine methyl ester (L-NAME), 100 µM), sodium nitroprusside (SNP, 25 µM), p38 mitogen-activated protein kinase(MAPK) inhibitor (SB203580, 5 µM) or extracellular signal-regulated kinases (ERK) 1/2 inhibitor (PD98059, 10 µM). Proliferation, tube formation, and apoptosis of EPCs were determined. Expressions of eNOS, PI3-K, protein kinase B (Akt), p38 MAPK, and ERK 1/2 were assessed.

RESULTS

Hyperinsulinemia caused a significant decrease in proliferation and tube formation abilities than control group. Hyperinsulinemia increased apoptosis rate of EPCs than control group. Furthermore, hyperinsulinemia downregulated phosphorylation of eNOS, PI3-K and Akt, and upregulated phosphorylation of p38 MAPK and ERK. SNP could restore impaired tube formation induced by hyperinsulinemia. P38 MAPK inhibitor but not ERK inhibitor could decrease apoptosis induced by hyperinsulinemia.

CONCLUSION

Hyperinsulinemia impaired EPCs' tube formation ability by downregulation of PI-3K/Akt/eNOS pathway. Hyperinsulinemia induced apoptosis of EPCs via upregulation of p38 MAPK.

Metformin Inhibits the Expression of Biomarkers of Fibrosis of EPCs In Vitro

Endothelial progenitor cells (EPCs) are a group of circulating cells with important functions in vascular repair and treatment of cardiovascular diseases. However, in patients with atrial fibrillation (AF), the number and function of EPCs reportedly are decreased. TGF-β is highly expressed in AF patients. In this study, we examined the effect of TGF-β1 on EPCs and the therapeutic outcome of metformin treatment on TGF-β1-induced EPCs. EPCs were induced with TGF-β1 at different concentrations (5 ng/ml, 10 ng/ml, and 20 ng/ml) for 48 h followed by western blot, qPCR, and immunofluorescence analyses to investigate changes in the levels of the fibrosis-related proteins, α-SMA, Col I, Col III, CTGF, and MMP-1. Live-dead cell staining was used to evaluate cell apoptosis. Compared with the control, TGF-β1 treatment significantly (p < 0.05) enhanced the levels of α-SMA, Col I, Col III, CTGF, and MMP-1 in a dose-dependent manner. The most effective concentration of TGF-β1 (20 ng/ml) was then used to induce fibrosis biomarker expression in EPCs, followed by treatment with metformin at different concentrations (0.5, 1, and 2 mmol/l). Metformin treatment suppressed TGF-β-induced expression of all above factors, with the effect at 2 mmol/l being significant (p < 0.05). Live-dead cell staining showed no difference among the control, TGF-β1-treated, and metformin-treated groups. In conclusion, our study showed that TGF-β1 induces the expression of fibrosis biomarkers in EPCs, which is attenuated by treatment with metformin. Thus, metformin may have therapeutic potential for improving EPC function in cardiovascular diseases.