功能性便秘和肠易激综合征便秘型患者结肠黏膜水通道蛋白8的表达与意义

Expression and its significance of aquaporin 8 in patients with functional constipation or constipated irritable bowel syndrome

目的检测功能性便秘（FC）、肠易激综合征便秘型患者（IBS-C）结肠黏膜水通道蛋白8（AQP8）的水平，及其与临床特征的相关性。方法收集2014年3月至12月符合罗马Ⅲ诊断标准的IBS-C患者16例，FC患者19例，同期健康体检者9名作为健康对照组。内镜下取3组受试者升、降结肠黏膜组织，采用实时荧光定量PCR及免疫组织化学方法检测AQP8 mRNA和蛋白质表达面积，采用Kruskal-Wallis检验统计各组间AQP8 mRNA表达差异和AQP8相对面积差异，采用Pearson相关系数统计其与临床特征的相关性。结果FC患者升结肠和降结肠的AQP8 mRNA相对表达量分别为1.38（0.61，4.09）、2.65（0.82，7.52），IBS-C患者分别为2.23（0.82，4.67）、1.35（0.51, 2.03），均比健康对照组[0.56（0.19，0.97）、0.38（0.21，1.19）]升高，差异均有统计学意义（ZFC＝-2.435、-3.149，ZIBS-C＝-2.690、-2.152，P均〈0.05）。FC患者降结肠AQP8 mRNA较IBS-C患者升高，差异有统计学意义（Z＝-2.003，P＝0.045）。FC和IBS-C组的AQP8 mRNA表达水平与患者病程长短呈正相关（r升结肠＝0.57、0.53, r降结肠＝0.49、0.54；P均〈0.05），与排便频率呈负相关（r升结肠＝-0.82、-0.61，r降结肠＝ -0.49、-0.53; P均〈0.05），与患者性别、年龄、初始发病年龄、腹胀无相关性（P均〉0.05）。FC组AQP8多表达于结肠黏膜上皮细胞胞质内，而IBS-C和健康对照组多表达于上皮细胞顶膜和基侧膜上。半定量分析显示，FC、IBS-C组患者降结肠AQP8相对面积均较健康对照组增加[3.42%（1.24%，5.61%）、2.45%（1.72%，4.27%）比1.18%（0.35%, 2.81%）；Z＝-2.534、-2.151，P均〈0.05]；FC组升结肠AQP8相对面积较健康对照组患者增加[2.46%（1.48%，4.18%）比1.14%（1.29%，2.15%）, Z＝-2.041, P〈0.05]。 结论FC患者降结肠AQP8 mRNA表达量及其蛋白质在细胞中的表达部位与IBS-C患者存在差异，可为两者鉴别提供依据。

ObjectiveTo detect the expression level of aquaporin 8 （AQP8） in patients with functional constipation（FC） or constipated irritable bowel syndrome （IBS-C）, and the correlation between the expression of AQP8 and clinical features.MethodsFrom March to December 2014, a total of 16 patients with IBS-C and 19 patients with FC met Rome Ⅲ criteria were collected, and nine healthy individuals were assigned to control group at the same period. The ascending and decending colonic tissues mucosa of FC, IBS-C and control group were taken under endoscope. The expression of AQP8 at mRNA and protein level was detected by real-time polymerase chain reaction （RT-PCR） and immunohistochemistry （IHC）. The differences in AQP8 mRNA expression and AQP8 relative area were analyzed by Kruskal-Wallis test among groups, and Pearson correlation coefficient was performed for correlation analysis between the expression and clinical features.ResultsThe relative expressions of AQP8 mRNA of ascending colon and descending colon of FC patients （1.38, 0.61 to 4.09; 2.65, 0.82 to 7.52） and IBS-C patients （2.23, 0.82 to 4.67; 1.35, 0.51 to 2.03） were higher than those of control group （0.56, 0.19 to 0.97; 0.38, 0.21 to 1.19）, and the differences were statistically significant （ZFC=-2.435, -3.149, ZIBS-C=-2.690, -2.152; all P〈0.05）. AQP8 mRNA expression of descending colon in patients with FC was higher than that of patients with IBS-C, and the difference was statistically significant （Z=-2.003, P=0.045）. The expression of AQP8 in patients with FC and IBS-C was positively correlated with disease course （ascending colon r=0.57 and 0.53; descending colon r=0.49 and 0.54, all P〈0.05）, and was negatively correlated with frequency of defecation （ascending colon r=-0.82 and -0.61; descending colon r=-0.49 and -0.53, all P〈0.05）. There was no correlation between the expression of AQP8 and age, gender, onset age, presence of abdominal symptoms of the patients （all P〉0.05）. Most of AQP8 of FC group was expressed in cytoplasm of colonic mucosa epithelial cells, while that of IBS-C group and control group was mostly expressed at apical membrane and basal membrane of epithelial cells. The results of semi-quantification demonstrated that AQP8 relative area of descending colon of FC and IBS-C group increased compared with that of control group （3.42%（1.24% to 5.61%）, 2.45%（1.72% to 4.27%） vs 1.18%（0.35% to 2.81%）; Z=-2.534, -2.151, both P〈0.05）. Meanwhile, AQP8 relative area of ascending colon of FC group increased compared with that of control group （2.46%（1.48% to 4.18%） vs 1.14%（1.29% to 2.15%） Z=-2.041, P〈0.05）.ConclusionThere are differences in AQP8 expression quantity and location in cells of descending colon between patients with FC and patients with IBS-C, which is a way for differentiation these two diseases.