Interleukin-17 SNPs and serum levels increase ulcerative colitis risk: a meta-analysis.
OBJECTIVE
To investigate the associations of interleukin-17 (IL-17) genetic polymorphisms and serum levels with ulcerative colitis (UC) risk.


METHODS
Relevant articles were identified through a search of the following electronic databases, excluding language restriction: (1) the Cochrane Library Database (Issue 12, 2013); (2) Web of Science (1945-2013); (3) PubMed (1966-2013); (4) CINAHL (1982-2013); (5) EMBASE (1980-2013); and (6) the Chinese Biomedical Database (1982-2013). Meta-analysis was conducted using STATA 12.0 software. Crude odds ratios and standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs) were calculated. All of the included studies met all of the following five criteria: (1) the study design must be a clinical cohort or a case-control study; (2) the study must relate to the relationship between IL-17A/F genetic polymorphisms or serum IL-17 levels and the risk of UC; (3) all patients must meet the diagnostic criteria for UC; (4) the study must provide sufficient information about single nucleotide polymorphism frequencies or serum IL-17 levels; and (5) the genotype distribution of healthy controls must conform to the Hardy-Weinberg equilibrium (HWE). The Newcastle-Ottawa Scale (NOS) criteria were used to assess the methodological quality of the studies. The NOS criteria included three aspects: (1) subject selection: 0-4; (2) comparability of subjects: 0-2; and (3) clinical outcome: 0-3. NOS scores ranged from 0 to 9, with a score ≥ 7 indicating good quality.


RESULTS
Of the initial 177 articles, only 16 case-control studies met all of the inclusion criteria. A total of 1614 UC patients and 2863 healthy controls were included in this study. Fourteen studies were performed on Asian populations, and two studies on Caucasian populations. Results of the meta-analysis revealed that IL-17A and IL-17F genetic polymorphisms potentially increased UC risk under both allele and dominant models (P < 0.001 for all). The results also showed that UC patients had higher serum IL-17 levels than healthy controls (SMD = 5.95, 95%CI: 4.25-7.65, P < 0.001). Furthermore, serum IL-17 levels significantly correlated with the severity of UC (moderate vs mild: SMD = 2.59, 95%CI: 0.03-5.16, P < 0.05; severe vs mild: SMD = 7.09, 95%CI: 3.96-10.23, P < 0.001; severe vs moderate: SMD = 5.84, 95%CI: 5.09-6.59, P < 0.001). The NOS score was ≥ 5 for all of the included studies. Based on the sensitivity analysis, no single study influenced the overall pooled estimates. Neither the Begger's funnel plots nor Egger's test displayed strong statistical evidence for publication bias (IL-17A/F genetic polymorphisms: t = -2.60, P = 0.019; serum IL-17 levels: t = -1.54, P = 0.141).


CONCLUSIONS
The findings strongly suggest that IL-17A/F genetic polymorphisms and serum IL-17 levels contribute to the development and progression of UC.
Juan Li, Department of Gastroenterology, the Third Affiliated Hospital of Liaoning Medical University, Jinzhou 120000, Liaoning Province, China.
Juan
J
Li
Juan Li, Department of Gastroenterology, the Third Affiliated Hospital of Liaoning Medical University, Jinzhou 120000, Liaoning Province, China.
Hao
H
Tian
Juan Li, Department of Gastroenterology, the Third Affiliated Hospital of Liaoning Medical University, Jinzhou 120000, Liaoning Province, China.
Hui-Jun
HJ
Jiang
Juan Li, Department of Gastroenterology, the Third Affiliated Hospital of Liaoning Medical University, Jinzhou 120000, Liaoning Province, China.
Bin
B
Han
D016022:Case-Control Studies; D003093:Colitis, Ulcerative / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D018450:Disease Progression; D005787:Gene Frequency; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood*; D020381:Interleukin-17 / Q000097:blood* / Q000235:genetics*; D016017:Odds Ratio; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D018570:Risk Assessment; D012307:Risk Factors
C508717:IL17A protein, human; C440021:IL17F protein, human; D018836:Inflammation Mediators; D020381:Interleukin-17
Interleukin-17; Meta-analysis; Polymorphism; Serum; Ulcerative colitis