Objective To investigate the role of homocysteine(Hcy)in the pathogenesis of irritable bowel syn-drome(IBS)and its effects on intestinal motility,visceral hypersensitivity,and barrier function.Methods Clinical cohorts and animal models were combined for this study.Clinically,fifteen IBS patients meeting Rome Ⅲcriteria and 15 control individuals were enrolled to detect fecal Hcy levels and their correlation with symptoms.As for animal experiments,water avoidance stress(WAS)and 2,4,6-trinitrobenzene sulfonic acid(TNBS)chemical induction were utilized to establish IBS rat and mouse models,combined with a high-methionine diet(HMD)to simulate hyperhomocysteinemia.IBS symptoms were evaluated through fecal water content,carmine red intestinal transit time,and visceral hypersensitivity scores.Immune-fluorescence and Western blot were used to detect intes-tinal epithelial tight junction proteins.Serum and fecal Hcy concentrations were measured to assess Hcy levels.Statistical analyses included t-tests and One-way Anova.Results Fecal Hcy level in IBS patients were signifi-cantly higher than those in the healthy control group which demonstrated a positive correlation with defecation fre-quency(P＜0.01).In animal models,the combination of TNBS administration and a high-methionine diet markedly elevated serum and fecal Hcy levels in mice,while synergistically exacerbated intestinal motility disor-ders and visceral hypersensitivity.In vitro experiments showed that Hcy treatment down-regulates the expression of tight junction proteins in human colon cancer cell line(Caco-2).Conclusions Hcy plays an important role in the pathogenesis of IBS by impairing intestinal barrier function and enhancing visceral hypersensitivity,and it may serve as a potential new target for the treatment of IBS.

Objective To study the mutation of FLCN gene in Chinese patients with sporadic and familial primary spontaneous pneumothorax. Methods A complete genetic analysis of FLCN by use of SSCP-PCR was performed in 102 unrelated Chinese patients with isolated PSP. Results Three novel mutations (c. 924_926del, c. 1611_1631del and c. 1740C.T) and a previously reported mutation (c. 1733insC) were identified in five familial and five sporadic PSP patients. Of the 21 family members of patients with PSP including 3 previous considered as sporadic, 4 ( 19% ) had history of at least one episode of PSP and 9 (43% ) were FLCN mutant carriers without PSP. Seven of the nine (78% ) mutant carriers had pulmonary cysts detected by high-resolution computed tomography ( HRCT) . Although c. 924_926del and c. 1611 _1631 del were found in eight patients from the same geographic district, haplotype analysis demonstrated that they did not share the same affected haplotype,thus excluding common ancestry. Conclusion This study first demonstrates that FLCN mutation contributes to not only familial but also apparently sporadic' patients with isolated PSP. It suggests that mutation analysis and HRCT scan may be recommended for first-degree family members of PSP patients with FLCN mutations, irrespective of their family history status of PSP.