The findings of the prior studies investigating the resistin levels in Crohn’s disease (CD) patients and ulcerative colitis (UC) patients are inconsistent. Hence we performed the meta-analysis to systematically evaluate the serum levels of resistin in CD and UC, as well as in healthy individuals. PubMed, Web of Science, Embase, Cochrane Library and Chinese National Knowledge Infrastructure (CNKI) (as of April 30, 2020) were searched to collect all relevant published articles. We calculated the pooled standard mean difference (SMD) and 95% confidence interval (CI) by R software. Eight articles including 438 CD patients and 358 controls, and 9 articles including 391 UC patients and 438 controls were enrolled. The results showed that resistin levels were significantly elevated in patients with CD (SMD = 1.76, 95% CI: 0.64 to 2.88, p = 0.002) and UC (SMD = 2.10, 95% CI: 1.03 to 3.17, p < 0.001) compared with healthy controls. Our findings indicate that the elevated levels of serum resistin were associated with CD and UC.

Summary Objective: Endoplasmic reticulum aminopeptidase 1 (ERAP1) is known to participate in the pathogenesis of ankylosing spondylitis (AS) cooperated with HLA-B27. This study aimed to evaluate the relationship between promoter methylation and mRNA levels of ERAP1 and AS. Methods: The DNA methylation level of 100 AS patients and 100 health controls (HCs) were tested using targeted bisulfite sequencing assay. Besides, the mRNA level of 20 AS patients and HCs was measured used quantitative real-time reverse transcription-polymerase chain reaction to verify the results of DNA methylation. Results: The methylation levels of two CpG islands containing 31 loci in ERAP1 promoter were measured. ERAP1_1 (P < 0.001) and ERAP1_2 (P < 0.001) islands were significantly hyperrmethylated in AS patients compared with healthy controls. Correspondingly, the mRNA level was significantly lower in AS patients. The ROC curve analysis reported the sensitivity, specificity and area under curve were 0.717, 0.737 and 0.779 of differential methylated CpG loci of ERAP1 for AS diagnosis. Besides, we also found that the methylation level was associated with the family history, non-steroidal anti-inflammatory drugs use, X-ray classification and clinical manifestations. Conclusions: Our study demonstrated that the ERAP1 gene is significantly hypermethylated in AS patients, which is verified by the lower mRNA level of AS patients. Our findings suggested that aberrant methylation of ERAP1 promoter may take part in the pathogenesis of AS and can be considered as diagnostic tool and therapeutic target of AS.