[Visceral sensitivity, gut barrier function and autonomic nerve function in patients with diarrhea-predominant...

To evaluate visceral sensitivity, gut barrier function and autonomic nerve function (ANF) in patients with diarrhea-predominant irritable bowel syndrome (IBS-D), and to explore their roles in IBS-D pathophysiology.
 Methods: A total of 46 IBS-D patients (IBS-D group) were selected from the Department of Gastroenterology of China-Japan Friendship Hospital from October 2015 to March 2016, and 20 healthy volunteer were served as a control group (HC group). Clinical and psychological symptoms were evaluated by questionnaire, and visceral sensitivity to rectal balloon distention, gut barrier function and autonomic nerve function (ANF) were examined. The difference in the above-mentioned indexes were compared between the 2 groups, and the correlations in the parameters were analyzed in the IBS-D group.
 Results: The scores of IBS symptom severity scale (IBS-SSS), Hamilton anxiety scale (HAMA), Hamilton depression scale (HAMD) and visceral sensitivity index (VSI) were significantly higher in the IBS-D group than those in the HC group (P<0.01). In the visceral sensitivity test, maximum tolerable threshold in the IBS-D group was significantly decreased compared to that in the HC group (P<0.01); there was no significant difference in first sensation threshold and defecating sensation threshold between the two groups (P>0.05). As gut barrier function markers, the serum diamine oxidase (DAO) and d-lactate were significantly increased in the IBS-D group (P<0.05). In ANF test, the total score and parasympathetic score as well as the proportion of abnormal scores in the IBS-D group were significantly higher than those in the HC group (P<0.05). In IBS-D group, the HAMA, VSI and serum DAO were positively correlated with IBS-SSS (r=0.528, 0.575, 0.507; P<0.01), while the 3 visceral sensitivity thresholds were negatively correlated with IBS-SSS (r=
-0.636, -0.476, -0.697; P<0.01); in addition to the IBS-SSS, the HAMA, HAMD, VSI and serum DAO were also significant negatively correlated with the visceral sensitivity thresholds (all P<0.05); no significant correlations were found between the ANF and the other parameters.
 Conclusion: IBS-D patients show psychological symptoms, visceral hypersensitivity, impaired gut barrier function and abnormal ANF characterized by parasympathetic dysfunction; the former 3 factors are all associated with disease severity, and thus may play vital roles in IBS-D pathophysiology.