[The impact of dietary methionine-restriction on tight junction expression and function in a rat colonitis model].
摘要
OBJECTIVE: To study the impact of methionine restriction (MetR) on mucosal histopathology, permeability and tight junction composition in a dextran sulfate sodium (DSS)-induced colitis model, and to explore its underlying mechanism. METHODS: SD rats were randomly divided into 4 groups: normal rats fed by a complete amino acid (AA group) diet, normal rats fed by MetR diet (MetR group), DSS treated rats fed by a complete amino acid (DSS+AA group) and DSS treated rats fed by MetR diet (DSS+MetR group), each group had 15 rats.Abdominal aorta blood sampling was taken at day 21 after DSS model been established to analyze blood routine examination, liver and kidney function and level of electrolyte. Morphological changes in colonic mucosa were evaluated and scored by light microscopy. Myeloperoxidase (MPO) activity was measured. The effect of MetR on mucosal permeability of colon strips was detected by Ussing chamber. Claudin2, occludin, claudin3, ZO-1 expression were quantified by Western blot. RESULTS: The early clinical manifestation in the DSS treated rats were loose stool or diarrhea, hematochezia positive and bleeding, and weight losing. HE observation showed prominent colitis in distal colon with manifestations of crypt abscess and infiltration of inflammatory cells. Although MPO activity and WBC account between the DSS+MetR and DSS+AA group did not significantly changed, treatment with MetR diet significantly decreased the extent and severity of epithelial injury of DSS+MetR group (10.55 ± 3.62 vs 15.00 ± 4.89, P = 0.003). There were no significant difference in PCNA immunohistochemical result between the DSS+MetR group and DSS+AA group. Compared to the rats on AA diet, transepithelial electrical resistance (TEER) in DSS+AA group was obvious lower [(28.40 ± 6.78) Ω·cm² vs (46.53 ± 4.03) Ω·cm², P < 0.05], and TEER in MetR group were obviously higher [(60.64 ± 8.40) Ω·cm² vs (46.53 ± 4.03) Ω·cm², P < 0.05]. However, short-circuit current (Isc) in DSS+MetR group was o