Background:Tryptophan(TRP)is an essential amino acid,and can produce 5-hydroxytryptamine(5-HT)via 5-HT signal pathway and kynurenine( KYN)metabolic pathway under the catalysis of enzyme,thereby participating in the pathogenesis of visceral hypersensitivity in diarrhea-predominant irritable bowel syndrome(IBS-D). Aims:To investigate the relationship between visceral sensitivity and TRP metabolic pathway in patients with IBS-D. Methods:Thirty patients with IBS-D and 30 healthy controls from June 2012 to January 2014 at Guangdong Provincial TCM Hospital were enrolled. Score of gastrointestinal symptom rating scale( GSRS)was evaluated. Visceral sensitivity was measured by anorectal manometry. RT-PCR and Western blotting were used to detect mRNA and protein expressions of colon mucosal IDo, respectively. Serum 5-HT,5-HIAA,TRP,IDo,KYN,KYNA concentrations and IDo activity,KAT activity were determined by high performance liquid chromatography assay. Results:Compared with control group,GSRS score was significantly increased(P < 0. 05),initial perception threshold,defecation threshold,pain threshold were significantly decreased(P < 0. 05),anorectal constriction pressure was significantly increased( P < 0. 05),serum 5-HT,5-HIAA concentrations were significantly increased(P < 0. 05),mRNA and protein expressions of IDo were significantly increased (P < 0. 05),serum KYN was significantly increased(P < 0. 05),KYNA was significantly decreased(P < 0. 01),IDo activity was significantly incseased(P < 0. 01),and KAT activity was significantly decreased in IBS-D group(P < 0. 01). Correlation analysis showed that initial perception threshold,defecation threshold,pain threshold and anorectal constriction pressure were correlated with 5-HT,5-HIAA,TRP,KYN,KYNA,IDo activity and KAT activity in patients with IBS-D (P < 0. 05). Conclusions:TRP metabolic pathway is correlated with visceral hypersensitivity in patients with IBS-D.%背景：色氨酸（TRP）是一种人体必需氨基酸，可通过5-羟色胺（5-HT）信号通路和犬尿氨酸（KYN）代谢途径在相关酶的催化下生成5-HT，参与腹泻型肠易激综合征（IBS-D）内脏高敏感的发生。目的：探讨 IBS-D 患者内脏敏感性与 TRP 代谢通路的相关性。方法：纳入2012年6月—2014年1月广东省中医院的30例 IBS-D 患者和30名健康体检者。行胃肠道症状评估量表（GSRS）评分，以肛门直肠测压检测内脏敏感性，以 RT-PCR 和蛋白质印迹法分别检测结肠黏膜 IDo mRNA 和蛋白表达，高效液相色谱法检测血清5-HT、5-HIAA、TRP、IDo、KYN 和 KYNA 浓度以及IDo 活性和 KAT 活性。结果：与对照组相比，IBS-D 组 GSRS 评分显著升高（P <0.05），初始感觉阈值、排便阈值和疼痛阈值显著降低（P <0.05），肛门直肠收缩压显著升高（ P <0.05），血清5-HT、5-HIAA 浓度均明显升高（ P <0.05），IDO mRNA 和蛋白表达明显增高（ P <0.05），血清 KYN 浓度明显增高（ P <0.05），KYNA 浓度明显降低（P <0.01），IDO 活性明显增高（P <0.01），KAT 活性明显降低（P <0.01）。相关性分析显示 IBS-D 组初始感觉阈值、排便阈值、疼痛阈值和肛门直肠收缩压与5-HT、5-HIAA、TRP、KYN、KYNA、IDo 活性和 KAT 活性相关（ P <0.05）。结论：TRP 代谢通路与 IBS-D 的内脏高敏感相关。
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