Carátula del artículo
Reduced Angiopoietin Factor 2 Levels Are Correlated with Better
Cardiac Function and Prognosis in Valvular Heart Disease
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Guangxian Chen
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Huawei Wu
University of California, United States of America
Zhongkai Wu wuzhk@mail.sysu.edu.cn
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Suiqing Huang
Sun Yat-sen University, People’s Republic of China
Sun Yat-sen University, People’s Republic of China
Brazilian Journal of Cardiovascular Surgery, vol. 38, no. 1, pp. 104-109, 2023
Sociedade Brasileira de Cirurgia Cardiovascular
Received: 25 June 2021
Accepted: 02 November 2021
INTRODUCTION
Valvular heart disease (VHD) is an important cause of morbidity and mortality, with a
prevalence that is predicted to increase dramatically because of the increase in
life expectancy in middle-income and high-income nations. Despite the wider
appreciation of the emerging importance of VHD, the mechanisms underlying its
development are poorly understood, and the role of circulating biomarkers in guiding
clinical management in individual patients is relatively unexplored.
Angiopoietin (Ang) 1 and 2, secreted 70-kDa glycoproteins and well-known members of
the Ang-Tie pathway, have been demonstrated to participate in a number of
cardiovascular diseases[1-3]. Ang2 mediates vascular leakage and
inflammation, while Ang1 has antipermeability, anti-inflammatory, and
cardioprotective effects[4-7]. Higher plasma Ang2 levels were
predictive of myocardial infarction[8,9] and stroke
recurrence[10] and were
independent of traditional risk factors. In acute myocardial infarction, the extent
of myocardial damage correlated with serum Ang2 and Ang2/Ang1[11], indicating that Ang1 and Ang2
are potential biomarkers of the severity of cardiac disease.
Vascular endothelial growth factor (VEGF) has been shown to act as a proinflammatory
cytokine by inducing the expression of adhesion molecules that cause leukocytes to
bind endothelial cells[12,13]. Moreover, increased VEGF levels
were associated with an imbalance of Ang1 and Ang2[14], suggesting the complicated connection of these
inflammation-associated cytokines. However, investigations on the correlation of
VEGF and Ang have mostly focused on coagulation, and few have been related to
inflammation.
Given that VHD is characterized by an ongoing inflammatory cellular response, we
hypothesized that Ang1, Ang2, and VEGF play important roles in the progression and
prognosis of VHD. To explore this hypothesis, plasma levels of Ang1, Ang2, and VEGF
in VHD patients and healthy individuals were measured.
METHODS
Participants’ Clinical Information
Forty-two subjects with VHD were recruited between March 2018 and March 2019. All
patients underwent a valve replacement procedure and recovered well. Twenty
subjects without VHD and asymptomatic cardiovascular events were recruited as a
healthy control group.
The exclusion criteria included age < 18 years old, recent-onset acute
cardiovascular or cerebrovascular events, trauma, or surgery, coronary artery
heart disease, pregnancy, acute or chronic infection, autoimmune disease,
malignant tumor, and pulmonary, hepatic, or renal dysfunction. Clinical data of
the patients were reviewed and collected. The study was approved by the clinical
research and experimental animal ethics committee ([2017]157), and all patients
enrolled in this study provided informed consent prior to participating in the
study.
Blood Sample Collection and Detection
Blood samples from VHD patients and healthy controls were obtained from forearm
veins using 6.0-mL vacutainer tubes (BD, Plymouth, United Kingdom) containing
ethylenediamine tetraacetic acid. After centrifugation at 2,500 rpm for 15
minutes, plasma samples were collected and stored at-80°C within one day for
further enzyme-linked immunosorbent assays (ELISAs) detection. The plasma levels
of Ang1, Ang2, and VEGF were determined using ELISAs according to the
instructions from the manufacturer (R&D Systems, Minneapolis, Minnesota,
United States of America).
Statistical Analysis
Normality was tested by Shapiro-Wilk test. Continuous variables with normal
distribution were expressed as mean±standard deviation and compared by Student’s
t-test or one-way analysis of variance. Categorical
variables were expressed as percentages (number and %) and compared by
Chi-squared test. All potential predictors for short-term (within 30 days after
surgery) mortality were studied using univariable logistic regression analysis.
Correlations were determined using Pearson’s correlation method. For all tests,
P<0.05 was considered statistically significant.
Statistical analysis was performed using GraphPad Prism Software (Version 8, La
Jolla, California, United States of America) and IBM Corp. Released 2013, IBM
SPSS Statistics for Windows, version 22.0, Armonk, NY: IBM Corp.
RESULTS
Patients’ Characteristics
Table 1 shows the demographic data of the
patients enrolled in this study. Patients with VHD consisted of 22 men and 20
women (age: 55.65±1.71 years). We retrieved information, including sex, age, New
York Heart Association (NYHA) classifications, ejection fraction (EF),
N-terminal pro B-type natriuretic peptide level, creatinine, uric acid, white
blood cell count, neutrophils, neutrophil percentage, neutrophil-to-lymphocyte
ratio, platelet, cardiopulmonary bypass duration, aortic cross-clamping
duration, length of tracheal intubation, length of intensive care unit stay, and
length of hospital stay from patients’ hospital charts.
Table 1
Clinical characteristics of VHD patients (n=42).
Concentration of Ang1, Ang2, and VEGF in VHD Patients with Different NYHA
Classifications
Ang1, Ang2, and VEGF levels were detected in the plasma samples of VHD patients
and the healthy control group (Tables 2
and 3). Compared with the healthy control
group, Ang2 was significantly decreased in the VHD group (control =
1736.70±95.69 pg/mL, VHD = 1365.05±98.48 pg/mL, P=0.023), while
no significant difference was observed in the Ang1 and VEGF levels. Further,
differences in plasma Ang1 and Ang2 and VEGF levels among patients with NYHA
I/II classes, NYHA III/IV classes, and controls were analyzed. Interestingly,
only the Ang2 expression level of NYHA I/II patients was significantly decreased
compared with that of healthy control individuals, but the same was not true for
NYHA III/IV patients (NYHA I/II: 1317.01±120.36 pg/mL vs.
healthy control group: P=0.017; NYHA III/IV: 1567.81±189.27
pg/mL vs. healthy control group: P=0.485),
suggesting that decreased Ang2 might be associated with better cardiac function
in VHD.
Table 2
Ang1, Ang2, and VEGF levels in control group and VHD
patients.
Table 3
Ang1, Ang2, and VEGF levels in control group and VHD
patients.
Univariable Logistic Regression
Univariable analysis (Table 4) showed
significant differences between short-term survivors and non-survivors in the
following factor: Ang2 (odds ratio 18.75, P=0.033, 95%
confidence interval 8.08-102.33).
Table 4
Univariable logistic regression.
Correlation of Ang1, Ang2, and VEGF Levels
Given the complex connection of Ang1, Ang2, and VEGF[14], the correlation of Ang1, Ang2, and VEGF
levels was also analyzed and is shown in Table
5. Ang1 levels were negatively correlated with Ang2 levels
(P=0.032, Pearson’s correlation coefficient =-0.317) and
positively correlated with VEGF levels (P=0.019, Pearson’s
correlation coefficient = 0.359).
Table 5
Correlations among plasma levels of Ang1, Ang2, and VEGF in VHD
patients.
DISCUSSION
In the present study, we found that the plasma level of Ang2 was significantly lower
in all VHD patients and VHD patients with NYHA I/II classes — but not in VHD
patients with NYHA III/IV classes — than in healthy controls. It may suggest an
association of decreased Ang2 levels and better cardiac function and prognosis in
VHD. The Ang1 expression level was negatively associated with Ang2 but positively
associated with VEGF.
The Ang-Tie axis, one of the most important switch signaling pathways for
angiogenesis, has been documented in a wide range of cardiovascular diseases and
inflammatory diseases[1,15]. Among the pathway members, the
best characterized are Ang1 and Ang2. Ang2 mediates vascular leakage[4] and inflammation[5], while Ang1 has
antipermeability[4],
anti-inflammatory[6], and
cardioprotective effects[7] because
of their opposite pathophysiological effects in response to binding to the Tie2
receptor[16]. Circulating
Ang2 levels and the Ang2/Ang1 ratio could serve as suitable biomarkers of
inflammatory disease. Circulating Ang2 levels were correlated with markers of
endothelial cell activation and 28-day mortality in patients with severe
sepsis[15]. In acute lung
injury patients, the Ang2/Ang1 ratio was an independent predictor of
mortality[17]. Higher Ang2
and Ang2/Ang1 were associated with poor cardiac function in acute myocardial
infarction patients[18]. Our
results are consistent with previous results. In the present study, lower Ang2
levels were observed in the VHD patients with lower NYHA classes and higher EFs
(Table 3). As Ang2 is an important
inflammation-associated cytokine[19,20], it may suggest
that lower Ang2 levels might prevent VHD progression and improve prognosis by
regulating inflammation levels. The association of Ang2/Ang1 ratio and VHD patient
characteristics was not observed in the present study (data not shown); however, a
significantly negative correlation of Ang1 and Ang2 was observed (Table 5), which might have been due to the
small sample size of our study. Furthermore, Ang1 and Ang2 have been shown to
interact with VEGF to induce an inflammatory response[21]. Our data showed the positive association of Ang1
and VEGF (Table 5), indicating that a
synergistic effect of Ang1 and VEGF might exist in VHD, which may regulate the
inflammation level. Taken together, these results suggest that Ang2 could affect the
disease progression and prognosis of VHD by regulating the inflammatory level via
the interaction of Ang1 and VEGF.
In summary, a lower Ang2 level was associated with a better NYHA class in VHD.
Univariable logistic regression analysis result indicated that Ang2 was a
significant independent predictor for short-term mortality. Furthermore, the
association of Ang1, Ang2, and VEGF was found in VHD. Thus, Ang2 might affect the
disease progression and prognosis of VHD, which may involve the interaction of Ang1
and VEGF.
Limitations
As a single-center retrospective study, this study has all the limitations of a
retrospective observational study. Thus, as an observational study, cause-effect
relationships could not be established. Further prospective studies are
necessary to confirm our present findings. Also, the sample size of our study
was small. The changes in plasma levels of Ang1, Ang2, and VEGF after valve
replacement surgery were not evaluated. Future studies could examine whether the
expression of these proteins changes after surgery and how the levels correlate
with the outcomes of valve replacement.
CONCLUSION
Ang2 might serve as a therapeutic and prognostic target for VHD.
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Notes
Notes
Financial support: This study was funded by the National Key R&D Program of
China (x 2017YFC1105000) and the National Natural Science Foundation of China
(81570039, 81770319, 81900294, 82070297).
This study was carried out at the Department of Cardiac Surgery, The First
Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong Province,
People’s Republic of China.
Conflict of interest declaration
No conflict of interest.
Author notes
* Jian Hou, Xiaolin Huang, and Liqun Shang contributed equally to this
work.
Correspondence Address: Zhongkai Wu Department of
Cardiac Surgery, The First Affiliated Hospital of Sun Yat-sen University, 58
Zhongshan Rd. No.2, Guangzhou, Guangdong Province, People’s Republic of China -
Zip Code: 510080, E-mail: wuzhk@mail.sysu.edu.cn
