The role of brain-derived neurotrophic factor in the abdominal pain of irritable bowel syndrome patients

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Objective To investigate the correlation between the expression changes of brain-derived neurotrophic factor (BDNF) in colon mucosa and abdominal pain in irritable bowel syndrome (IBS). The density of nerve fiber in colon mucosa and ultrastructural alterations of nerve fiber in IBS were also observed. Methods From September 2008 to January 2010,the IBS patients who visited the department of gastroenterology of our hospital and met the Rome Ⅲ diagnosis criteria were selected and divided into IBS with diarrhea (D-IBS) and IBS with constipation (C-IBS) according to their clinical features. The patients with colon polyps detected by colonoscopy in our hospital were selected as control group. All subjects were asked to fill in Self-Rating abdominal pain or abdominal uncomfortable Scale according to abdominal symptom in the last 2 weeks before visit and underwent colonoscopy. Four biopsy specimens were taken from the colon mucosa of rectosigmoid junction. Ofwhich,two specimens were for protein isolation and detection of BDNF expression level,one specimen was used for PGP 9. 5 immunohistochemistry staining in paraffin slices. Another specimen was used to observe the ultrastructure changes of nerve fiber in colon mucosa under transmission electron microscopy. Results Total 40 IBS patients were enrolled in this study,of those 21 were D-IBS patients,19 were C-IBS patients,and 21 were controls. The abdominal pain severity score and frequency score of IBS patients were (2. 3±0. 8) and (2. 1±0. 7),which were significantly higher than those of control group (0. 4±0. 7 and 0. 3±0. 5,P＜0. 001). Compared with the control group,the BDNF expression in colon mucosa was significantly elevated in IBS patients (P= 0. 003 ),and which correlated with the severity and frequency of abdominal pain/discomfort (r=0. 57,P＜0. 001and r=0. 46,P= 0. 003,respectively). The immunohistochemistry result indicated that the nerve fiber density in colon mucosa of IBS patients was significantly higher than that of controls,and there were ultrastructural changes of colon mucosal nerve fibers in IBS patients. Conclusion Increased colon mucosal BDNF expression may be associated with abdominal pain symptom in IBS patients. The impaired ultrastructural of mucosal nerve fibers may cause the increased BDNF expression in colon mucosa,and result in the increased mucosal nerve fiber density in IBS patients. Key words: Brain-derived neurotrophic factor; Irritable bowel syndrome; Abdominal pain; Microscopy,electron; Nerve fibers; Intestinal mucosa