Role and Mechanism of Colon Circadian Clock Gene Bmal1 Involved in Symptoms of Irritable Bowel Syndrome With Diarrhea / 胃肠病学

ABSTRACT

Background: Symptoms of irritable bowel syndrome with diarrhea (IBS-D) are known to be influenced by circadian oscillation; however, the pathophysiological mechanism is still unclear. Aims: To investigate the role and underlying mechanism of colon circadian clock gene Bmal1 involved in the occurrence of symptoms in IBS-D patients. Methods: Forty-six patients with IBS-D and 34 normal controls from Army Medical Center of PLA during September 2018 to February 2021 were recruited in this study. IBS-severity scoring system (IBS-SSS) was used to evaluate the severity of IBS-D symptoms. A colonoscopy was performed to obtain biopsy specimens from rectosigmoid colon. The concentration of 5-hydroxytryptamine (5-HT), and expressions of Bmal1 and chromogranin A (CgA), a biomarker of enterochromaffin cells (EC cells), in colonic mucosa were detected by ELISA and double-labeled immunofluorescence, respectively. Results: Both the 5-HT concentration and number of EC cells in colonic mucosa of IBS-D patients were significantly higher than those of the normal controls (all P< 0.05). Bmal1 was mainly expressed in intestinal epithelial cells and was highly expressed in EC cells. Co-expression of Bmal1 and CgA was observed. Compared with the normal control group biopsied at the same time point, expression of Bmal1 was significantly higher in specimens taken at 9 a.m., and expression of Bmal1 was significantly lower in specimens taken at 17 p.m. in IBS-D patients (all P< 0.05). Spearman correlation coefficient analysis showed that Bmal1 expression at 9 a.m. was positively correlated with the total score of IBS-SSS and subscore of abdominal pain and discomfort (r