Objective To explore the pathogenesis of irritable bowel syndrome (IBS) by detecting serum levels and the colonic mucosa expression of inflammatory cytokines, peptide YY (PYY), and claudin-1, and to analyze their correlation. Methods From April 2013 to April 2015, 50 outpatients with IBS and 20 healthy controls were selected. Serum levels of PYY, interleukin (IL)-10, tumor necrosis factor (TNF)-α and claudin-1 were detected by enzyme-linked immunosorbent assay (ELISA). The expression of IL-10, TNF-α, PYY and claudin-1 in colonic mucosa was determined by immunohistochemistry. Single factor analysis of variance, least significant difference (LSD) method, chi-square test, and Pearson correlation analysis were performed for statistical analysis. Results Among the 50 patients with IBS, 27 cases were diarrhea-type irritable bowel syndrome (D-IBS), and 23 cases were constipated-type irritable bowel syndrome (C-IBS). The serum level and the positive expression rate of PYY in colonic mucosa of D-IBS group were significantly higher than those of healthy control group ((16.28±2.75) ng/L vs (10.12±1.55) ng/L; 66.7%(18/27) vs 30.0%(6/20)), and the differences were statistically significant (LSD-t=10.19, χ2=6.182, both P 0.05). The serum level of claudin-1 and its positive expression rate of PYY, IL-10, TNF-α in colonic mucosa in D-IBS group were both lower than those of healthy control group ((94.44±6.61) ng/L vs (103.64±5.47) ng/L; 11.1%(3/27) vs 40.0%(8/20)), and the differences were statistically significant (LSD-t=5.76, χ2=5.349; both P<0.05). However, the serum level of claudin-1 and its positive expression rate in colonic mucosa in C-IBS group were both higher than those of healthy control group ((115.54±3.42) ng/L vs (103.64±5.47) ng/L; 73.9%(17/23) vs 40.0%(8/20)), and the differences were statistically significant (LSD-t=5.56, χ2=5.055; both P<0.05). The serum levels of IL-10 and PYY, TNF-α and claudin-1 were negatively correlated in the D-IBS group (r=-0.874 and -0.863, both P<0.05). While the serum levels of TNF-α and PYY, IL-10 and claudin-1 were positively correlated (r=0.865 and 0.876, both P<0.05). Conclusions There may be the imbalance of proinflammatory factors and anti-inflammatory factors in IBS patients. PYY may decrease the expression of claudin-1 by promoting IL-10 and inhibiting TNF-α, and thus ameliorate the inflammation reaction of IBS patients. Key words: Irritable bowel syndrome; Tumor necrosis factor-alpha; Interleukin-10; Peptide YY; Claudin-1
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