Abstract
Objective
Polymorphisms in the tumor necrosis factor superfamily 15 (
Methods
Eligible articles were retrieved from the PubMed, EMBASE, Web of Science, and CNKI databases through 20 March 2020. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the relationships of
Results
Under the recessive model,
Conclusions
Our meta-analysis suggested that under the allelic and recessive models, the
Keywords
Introduction
Inflammatory bowel disease (IBD) is a type of chronic, nonspecific intestinal inflammation.
1
,
2
Crohn’s disease (CD) and ulcerative colitis (UC) are two subtypes of IBD.
2
The etiology and pathogenesis of IBD are still unclear, but may be related to the combined effects of three aspects: intestinal flora, abnormal immune-mediated tissue damage, and genetic susceptibility.
3
,
4
Genetic factors are also considered to play an important role in the development of IBD. Research has shown that the coincidence of monozygotic twins in patients with IBD is 20% to 50%.
5
In recent years, a number of genes, including nucleotide binding oligomerization domain containing 2 (
The
An increasing number of studies have revealed that polymorphisms in
Considering the limited sample sizes in individual studies, we performed a meta-analysis by including eligible published studies to evaluate the relationship of the
Materials and methods
Publication search
A comprehensive systematic search was performed for all related publications up to 20 March 2020, using the following search terms: “tumor necrosis factor super family member 15 gene” or “TNFSF15”, and “polymorphism” or “single nucleotide polymorphism” or “SNP” or “variant” and “inflammatory bowel disease” or “IBD” or “Crohn’s disease” or “CD” or “ulcerative colitis” or “UC” through PubMed, EMBASE, Web of Science, and China National Knowledge Infrastructure (CNKI) databases. All procedures were conducted in accordance with Cochrane definitions and PRISMA 2009 guidelines for meta-analysis and systematic reviews. No limitations concerning language and publication year were set. Additionally, references from the relevant literature were manually screened. Ethical approval was considered unnecessary for this meta-analysis.
Inclusion and exclusion criteria
The criteria for inclusion were (1) case-control studies; (2) studies that documented the genetic association of
Data extraction and quality assessment
The following data were reviewed and collected: the first author’s name, year of publication, ethnicity, mean ages, percentage of males, numbers of cases and controls, and genotype and allele frequencies. Two authors (J.H.G. and C.Z.H.) carried out the data extraction independently. Discrepancies were resolved by discussion. The Newcastle–Ottawa Scale (NOS) was used to evaluate the quality of an individual study. The NOS scores ranged from 0 to 8. Studies were enrolled in the present meta-analysis if a NOS score ≥6 was obtained.
Statistical analysis
Pooled odd ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the relationship of the
Results
Characteristics of eligible studies
As shown in Figure 1, 679 studies were initially found after the initial search. After screening the titles, abstracts, and full text, 672 irrelevant studies were excluded and seven studies were enrolled in this meta-analysis.25–31 Table 1 summarizes the main characteristics of these eligible studies. One study was in a Caucasian population 29 and six were in Asian populations.25–28, 30 , 31 Five articles were on CD 25 ,27–30 and two were on UC. 26 , 31 One study was conducted on both CD and UC. 25 The studies in control groups were consistent with HWE. All of the eligible studies achieved NOS scores >6, indicating that they were of high methodological quality (Table 1).

PRISMA flowchart showing inclusion and exclusion of studies
Characteristics of included studies.
SD, standard deviation; CD, Crohn’s disease; UC, ulcerative colitis; HWE, Hardy-Weinberg equilibrium; NOS, Newcastle-Ottawa Scale.
Combined outcomes
A significant association was found between

Forest plots of odds ratios (and 95% confidence intervals, CI) for the association between
Association between
IBD, inflammatory bowel disease; CD, Crohn’s disease; UC, ulcerative colitis; OR, odds ratio; CI, confidence interval; F, fixed model; R, random model.

Forest plots of odds ratios (and 95% confidence intervals, CI) for the association between

Forest plots of odds ratios (and 95% confidence intervals, CI) for the association between
Association between
IBD, inflammatory bowel disease; CD, Crohn’s disease; UC, ulcerative colitis; OR, odds ratio; CI, confidence interval; F, fixed model; R, random model.
The association between TNFSF15 rs7865494 polymorphism and IBD risk.
IBD, inflammatory bowel disease; CD, Crohn’s disease; UC, ulcerative colitis; OR, odds ratio; CI, confidence interval; R, random model.
We performed a stratification analysis on the basis of ethnicity. Individuals in the Asian population carrying the
Heterogeneity and sensitivity analyses
Significant heterogeneity was found in all genetic models for the

Sensitivity analyses between
Publication bias
The funnel plots were symmetrical and the results of Egger’s test indicated no evidence of publication bias for

Publication bias of literatures for allelic model of
Discussion
According to the differences in secreted cytokines and mediated immune functions, CD4+ T cells can be divided into T helper (Th)1 and Th2 cells. 32 Th1 cells mainly secrete interleukin (IL)-12 and interferon (IFN)-γ, whereas Th2 cells mainly secrete IL-4, IL-13, and IL-10. 33 The Th1/Th2 imbalance has always been considered part of the pathogenesis of IBD. CD is mainly considered a type of Th1 disease, with secretion of IFN-γ, tumor necrosis factor (TNF)-α, IL-2, and IL-18 from intestinal mucosal cells, 34 whereas UC is a Th2 disease.
TNF-like ligand 1A (TL1A) is locally expressed in CD4+, CD8+ T lymphocytes and plasma cells of patients with UC. The amount of TL1A protein and the number of TL1A-positive cells are positively correlated with the severity of inflammation. 35 TL1A can bind to DR3 (TNFRSF25), activate NF-κB, and regulate DR3-mediated apoptosis. It also promotes the release of proinflammatory cytokines by immune cells. 21 Kamada et al. showed that TL1A not only induced differentiation of naïve CD4+ T cells to Th1 and Th17 in the intestinal mucosa lamina propria, but also promoted the secretion of IFN-γ and IL-17 in coordination with IL-23. 36 Thus, TL1A plays an important role in the occurrence and pathogenesis of intestinal mucosal inflammatory response in IBD.
The
In this meta-analysis, we found that
The current meta-analysis has a number of limitations. First, although seven studies with 2682 cases and 3242 controls were included, the sample size of the subgroup analyses, particularly for the Caucasian subgroup, was insufficient, which may affect the correlations. Second, both genetic and environmental factors can affect the process of IBD development. However, we failed to assess the effect of these factors in IBD. Third, the studies included in the present study were conducted in Asian and Caucasian populations; no studies with participants of other ethnicities were included.
Conclusions
Our meta-analysis suggested that under the allelic and recessive models, the
Supplemental Material
sj-pdf-1-imr-10.1177_0300060520961675 - Supplemental material for Polymorphism rs6478109 in the TNFSF15 gene contributes to the susceptibility to Crohn’s disease but not ulcerative colitis: a meta-analysis
Supplemental material, sj-pdf-1-imr-10.1177_0300060520961675 for Polymorphism rs6478109 in the
Supplemental Material
sj-pdf-2-imr-10.1177_0300060520961675 - Supplemental material for Polymorphism rs6478109 in the TNFSF15 gene contributes to the susceptibility to Crohn’s disease but not ulcerative colitis: a meta-analysis
Supplemental material, sj-pdf-2-imr-10.1177_0300060520961675 for Polymorphism rs6478109 in the
Footnotes
Declaration of conflicting interest
The authors declare that there is no conflict of interest.
Funding
This work was supported by the Medical and Health Science and Technology Project of Zhejiang Province, China (2019KY214, 2019KY692); the Jiaxing Key Discipline of Medicine-Oncology (Supporting Subject) 2019-zc-11; the Basic Public Welfare Research Program of Zhejiang Province, China (LGF18H160033); and the project of Public Welfare research of Jiaxing (2019AD32257).
References
Supplementary Material
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