Expression of inflammatory cytokines and its correlation with peptide YY and claudin-l in patients with irritable bowel syndrome

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