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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 13  |  Issue : 1  |  Page : 9-13

Serum levels of tumor necrosis factor-alpha and vascular endothelial growth factor as markers of disease activity in patients with axial spondyloarthritis


Institute of Rheumatology, Madras Medical College, Chennai, Tamil Nadu, India

Date of Web Publication26-Feb-2018

Correspondence Address:
Dr. Mahendran Bhuvanesh
Institute of Rheumatology, Madras Medical College, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/injr.injr_64_17

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  Abstract 


Background: Assessment of disease activity in axial spondyloarthritis (axSpA) has remained a challenge. This study aims to investigate the role of vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-α) as markers of disease activity in patients with axSpA.
Methods: A total of 40 patients with axSpA were included in this study. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)/Bath Ankylosing Spondylitis Functional Index (BASFI), serum TNF-α, and VEGF levels were assessed at baseline and the same parameters were assessed after 24 weeks of therapy with either etanercept or NSAIDs (20 patients in each group). Twenty healthy age- and sex-matched controls were also recruited for the study.
Results: Patients with axSpA had higher levels of serum TNF-α (mean 341 pg/ml) and VEGF (mean 791 pg/ml) as compared with healthy controls (mean 72.5 pg/ml, P < 0.001 and mean 269 pg/ml, P < 0.001). There was significant reduction in serum TNF-α and VEGF levels after 24 weeks of treatment with etanercept (mean 161 pg/ml, P < 0.001 and mean 442 pg/ml, P < 0.001, respectively) but not with NSAID (P = 0.29, P = 0.25). Both TNF-α and VEGF had a positive correlation with BASDAI (r = 0.57, P < 0.01 and r = 0.44, P < 0.01) and BASFI (r = 0.61, P < 0.01 and r = 0.33, P = 0.03) at baseline. The levels of TNF-α and VEGF showed no correlation with ESR and CRP (P = 0.48, P = 0.07 and P = 0.21, P = 0.06, respectively) at baseline. There was no correlation between BASDAI and levels of ESR, CRP (P = 0.27 and P = 0.49, respectively).
Conclusion: Serum levels of TNF-α and VEGF serve as better markers of disease activity as compared with ESR and CRP in axSpA.

Keywords: Ankylosing spondylitis, biologics, biomarkers, spondyloarthropathy


How to cite this article:
Bhuvanesh M, Balaji C, Saranya C, Ramesh R, Tamilselvam TN, Rajeswari S. Serum levels of tumor necrosis factor-alpha and vascular endothelial growth factor as markers of disease activity in patients with axial spondyloarthritis. Indian J Rheumatol 2018;13:9-13

How to cite this URL:
Bhuvanesh M, Balaji C, Saranya C, Ramesh R, Tamilselvam TN, Rajeswari S. Serum levels of tumor necrosis factor-alpha and vascular endothelial growth factor as markers of disease activity in patients with axial spondyloarthritis. Indian J Rheumatol [serial online] 2018 [cited 2018 Aug 18];13:9-13. Available from: http://www.indianjrheumatol.com/text.asp?2018/13/1/9/215322




  Introduction Top


Early diagnosis of axial spondyloarthritis (axSpA) is often difficult due to vague symptoms, the paucity of clinical findings, and lack of specific blood investigations.[1] The average delay in diagnosis of spondyloarthritis is about 10 years.[2] Monitoring of disease activity is also difficult due to the lack of specific markers of inflammation. Conventional markers of inflammation, namely erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), seldom correlates with disease activity. To help in the early diagnosis and monitoring of disease activity, there has been a growing need for new biomarkers.[3] Spondyloarthritis is a condition that is characterized by both bone resorption and formation occurring simultaneously.[4] Vascular endothelial growth factor (VEGF) severs as a marker of angiogenesis and endochondral ossification and hence represents bone formation.[5],[6] Tumor necrosis factor-alpha (TNF-α) is a key marker of inflammation and bone resorption in spondyloarthritis.[7],[8] Hence, estimation of VEGF and TNF-α will serve to monitor the divergent pathogenic mechanisms of axSpA. The aim of this study was to investigate the role of serum VEGF and TNF-α as markers of disease activity in axSpA and also their association with treatment with anti-TNF-α.


  Methods Top


The study was conducted at a tertiary care center in South India. Forty patients with axSpA who fulfilled the Assessment of SpondyloArthritis International Society criteria for axSpA were included in this study.[9] At the time of recruitment, patients were naïve to treatment with anti-TNF-α therapy. Overnight fasting blood samples were drawn from the patients and tested for ESR, CRP, serum VEGF, and serum TNF-α. Assessment of disease activity was performed using Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Bath Ankylosing Spondylitis Functional Index (BASFI).[10],[11] The VEGF levels were analyzed using a commercially available human VEGF enzyme-linked immunosorbent assay (ELISA) kit. TNF-α levels were done using a commercially available human TNF-α ELISA kit. The 40 patients were subsequently divided into two groups of twenty each. Group 1 received etanercept 50 mg/week subcutaneously for 24 weeks. Group 2 received NSAIDs (either diclofenac – maximum dose 150 mg/day or indomethacin – maximum dose 150 mg/day) for 24 weeks. NSAID dose was adjusted according to the tolerability of the patient. Parameters done at baseline were repeated at the end of 24 weeks of treatment.

Statistical analysis

Statistics were computed using Statistical Package for Social Sciences version 22 (Armonk, NY, IBM Corp). Descriptive measures such as mean, median, mode, confidence interval, and percentiles were used. Continuous variables were analyzed with correlation, regression, and t-test (paired). Parametric variables between the control and test group were analyzed using t-test for equality of means.

Ethical approval

The study was approved by the ethics committee of the institute. Informed written consent was obtained from all patients prior to their enrollment in this study.


  Results Top


Baseline parameters were comparable between the groups as shown in [Table 1]. Patients in both etanercept and NSAID group had higher levels of VEGF and TNF-α when compared to age- and sex-matched healthy controls as shown in [Table 2] and [Table 3].
Table 1: Baseline characteristics between treatment groups

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Table 2: Comparison of disease activity markers in etanercept group (before and after treatment)

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Table 3: Comparison of disease activity markers in nonsteroidal anti-inflammatory drug group (before and after treatment)

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There was a significant reduction in VEGF levels after 24 weeks of treatment (mean 442 pg/ml) with etanercept when compared to baseline values (mean 791 pg/ml, P < 0.001). We also found a significant reduction in TNF α levels in the etanercept group after 24 weeks of treatment (mean 169.5 pg/ml) when compared to baseline (mean 341.25 pg/ml, P < 0.001) as shown in [Table 2].

There was a decrease in VEGF and TNF-α after 24 weeks of treatment with NSAIDS, but the decrease was not statistically significant as shown in [Table 3].

Both TNF-α and VEGF had a positive correlation with BASDAI (r = 0.57, P < 0.01 and r = 0.44, P < 0.01, respectively) at baseline as shown in [Figure 1] and [Figure 2]. Similarly, both TNF α and VEGF showed significant positive correlation with BASFI (r = 0.61, P < 0.01 and r = 0.33, P = 0.03, respectively) at baseline as shown in [Table 4].
Figure 1: Scatter plot showing positive correlation between vascular endothelial growth factor and Bath Ankylosing Spondylitis Disease Activity Index

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Figure 2: Scatter plot showing positive correlation between tumor necrosis factor-alpha and Bath Ankylosing Spondylitis Disease Activity Index

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Table 4: Relationship between Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index and the inflammatory markers

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There was no correlation between ESR and BASDAI (r = 0.17, P = 0.27), BASFI (r = 0.04, P = 0.75). Similarly, there was no correlation between CRP and BASDAI (r = 0.11, P = 0.49), BASFI (r = −0.03, P = 0.82) as shown in [Table 4].

There was good linear correlation between VEGF and TNF-α (r = 0.72, P < 0.01) as shown in [Figure 3]. We could not find any correlation between TNF-α and ESR, CRP (r = −0.11, P = 0.48; r = −0.28, P = 0.07, respectively). Similarly, there was no correlation between VEGF and ESR, CRP (r = −0.20, P = 0.21 and r = −0.311, P = 0.06, respectively) as shown in [Table 5].
Figure 3: Scatter plot showing positive correlation between vascular endothelial growth factor and tumor necrosis factor-alpha

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Table 5: Relationship between erythrocyte sedimentation rate, C-reactive protein and biomarkers

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  Discussion Top


The assessment of disease activity and radiologic progression in axSpA has remained a challenge.[12] Various studies have negated the role of conventional markers of inflammation in assessing disease activity in axSpA.[13],[14],[15] The lack of association between inflammatory markers and disease activity in axSpA may be due to two reasons.[16] First, ESR and CRP do not reflect the exact pathogenic process involved in axSpA but rather a general inflammatory process. Therefore, it lacks specificity. Second, in axSpA inflammation is largely restricted to specific tissue compartments and does not extend to the systemic circulation. Therefore, there has been a growing need for identification of new markers of inflammation in axSpA.[17]

In this study, there was no correlation between ESR, CRP and disease activity tools such as BASDAI and BASFI. The study results are in keeping with other studies.[18],[19],[20] We found a good association between VEGF and BASDAI, BASFI and also between TNF-α and BASDAI, BASFI. In contrast, Pedersen et al. showed that VEGF correlated well with ASDAS but only weekly with BASDAI.[21] This reflects that VEGF and TNF-α are better markers of disease activity compared to conventional inflammatory markers.

VEGF is a signal transduction protein which is an important stimulator for angiogenesis.[22] In axSpA VEGF plays a pivotal role in new bone formation.[23] Thus, the elevated VEGF in our study is significant in reflecting the pathologic process of new bone formation in axSpA.[24],[25] The reduction in VEGF levels after 24 weeks of therapy with etanercept marks the efficacy of anti-TNF-α in targeting the basic pathogenic mechanism of new bone formation in axSpA. In a study by Tošovský et al., there was a similar reduction in VEGF levels in subjection receiving anti-TNF therapy which is in keeping with our study.[26]

TNF-α is a key cytokine involved in osteolysis.[27] In axSpA elevated TNF-α levels signify the ongoing bone destruction.[28] In this study, TNF-α levels were elevated at baseline, and there was a significant reduction after 24 weeks of etanercept therapy but not with NSAIDS. Hence, anti-TNF-α therapy may target the osteolytic pathway better than what NSAIDS do.

ESR and CRP had decreased in both NSAID and etanercept group after 24 weeks of treatment. In spite of the reduction in ESR and CRP following treatment in both groups, they did not correlate with disease activity as much as TNF-α and VEGF. In the absence of routine availability of TNF-α and VEGF; ESR and CRP may still be used in an individual patient in conjunction with clinical parameters to assess activity. Both TNF-α and VEGF levels continue to remain as a tool in research agenda.

Although we found a significant reduction in BASDAI and BASFI after 24 weeks of therapy in both etanercept and NSAID group, the reduction in disease activity has not resulted in a decrease in biomarkers in the NSAID group. This implies that other mechanisms may be involved in persistent elevation of biomarkers. Baseline levels of TNF-α and VEGF were low in the NSAID group compared to the etanercept group [Table 1]; this has probably influenced the treatment response when compared to the other group.

Prediction of radiologic progression in axSpA is a difficult task. One way to predict the radiologic progression is to use biomarkers of disease activity. This study gains significance in demonstrating the role of VEGF and TNF-α as markers of disease activity and may, therefore, be used as predictors of radiologic progression in axSpA.

Our study with a small sample size has shown that serum levels of TNF-α and VEGF serve as better markers of disease activity when compared with ESR and CRP in axSpA. Significant reduction in VEGF levels with treatment makes it a potentially new therapeutic target in axSpA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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