- 學位論文
以小鼠化學發炎致癌模式探討蒟蒻纖維及菊糖寡醣對大腸直腸癌腫瘤發生及免疫調節作用
Effects of konjac glucomannan and inulin oligosaccharide on tumor development and immune function in colitis-associated colon carcinogenesis mouse model
摘要
目的：本研究目的是探討於發炎恢復期補充蒟蒻纖維(KGM)及菊糖(Inulin)寡醣對azoxymethane (AOM)合併dextran sulfate sodium (DSS)誘發之發炎性大腸直腸癌 (colitis-associated colon cancer，CAC)是否具有延緩作用，並探討其免疫作用、腸道環境因子及可能機制。 材料方法：第一階段為誘發期: 6週齡之C57BL/6J雄性小鼠依體重隨機分成Vehicle組以及AOM-DSS組，給予AOM-DSS組AOM注射(i.p., 10 mg/kg BW)及3循環的1-1.5% DSS (w/v)飲水以誘發大腸急性發炎，飼料為AIN-93G，經3天恢復期後再進入第二階段實驗飼料期，依發炎程度將小鼠平均分配於四組：Control (AIN-93G diet)、KGM (2% w/w)、 Inulin (2% w/w)及KGM (1% w/w) + Inulin (1% w/w)補充組；Vehicle組則全程未施予任何藥劑並給予AIN-93G 飼料。飲食介入9週後犧牲小鼠，分析腫瘤病理情形(相對腫瘤面積、組織切片病理評分)、血液白血球吞噬能力、發炎相關指標(脾臟細胞細胞激素濃度、遠端大腸組織cyclooxygenase-2免疫染色)、腸道環境因子(盲腸內容物短鏈脂肪酸濃度與糞便菌相)及遠端大腸組織增生基因cyclin D1及抗凋亡基因B-cell lymphoma 2 (bcl-2)的表現。 結果：結果顯示AOM-DSS小鼠之腺癌發生率為100%，而且以Control組最嚴重，補充蒟蒻及菊糖可有效降低腫瘤侵襲程度。免疫作用方面：Control組血液白血球吞噬能力顯著低於Vehicle組，脾臟細胞發炎細胞激素Interleukin-1β (IL-1β)及Tumor necrosis factor-α (TNF-α)的分泌量顯著高於Vehicle組。在補充蒟蒻及菊糖後有助於提升吞噬能力，顯著抑制脾臟細胞IL-1β及TNF-α分泌，並且降低遠端大腸組織cyclooxygenase-2 (COX-2)表現量。在大腸組織基因表現方面：Control組cyclin D1和bcl-2表現量最高，在補充蒟蒻及菊糖後有降低cyclin D1表現的趨勢。在腸道環境因子方面：Control組糞便Bifidobacterium spp.菌數較低，Clostridium spp.菌數較高，盲腸內短鏈脂肪酸濃度較低。在補充蒟蒻及菊糖後均可促進Bifidobacterium spp.生長並抑制Clostridium spp.孳生，且有效增加盲腸內短鏈脂肪酸的濃度。 結論：本研究建議於發炎恢復期補充少量(2%, w/w)蒟蒻纖維或菊糖寡醣具有降低發炎性大腸直腸癌發生的潛力，可能藉由調控腸道微生物代謝，提升白血球吞噬能力、降低體內發炎反應以及調節大腸組織基因表現有關。
並列摘要
Objectives. The aim of study was to determine effects of konjac glucomannan (KGM) and inulin oligosaccharide on tumor development, immune function, intestinal ecology and its mechanisms using a colitis-associated colon carcinogenesis mouse model. Materials and Methods. Six-week-old C57BL/6J male mice were fed control diet (AIN-93G) and initially divided into vehicle control and AOM-DSS groups for 50 days. The AOM-DSS group was administered with a single carcinogen azoxymethane (AOM) (i.p., 10 mg/kg BW) and three cycles of 1-1.5% (w/v) dextran sodium sulfate (DSS) to induce inflammation of the large intestine. After 3 days of recovery period, the AOM-DSS treated mice were divided into control (AIN-93G diet), and fiber-supplemented (KGM 2%, Inulin 2%, and KGM 1% + Inulin 1% w/w) groups. Mice were sacrificed after 9 weeks of dietary intervention. The severity of adenocarcinoma, leukocyte phagocytic capacity, spleen proinflammatory cytokines, Cox-2 stain, gene expression of cyclin D1 and B-cell lymphoma 2 (bcl-2) in the distal colon, the cecal short-chain fatty acid and fecal microbiota were determined. Results. Colonic adenocarcinoma occurred in all AOM-DSS-treated mice. Supplementation of konjac and inulin effectively reduced the extent of tumor invasion. Compared to vehicle group, leukocyte phagocytotic ability were lower and spleen interleukin-1β(IL-1β) and tumor necrosis factor-α(TNF-α)levels were higher in the control group, which was partially reversed with KGM and inulin supplementation. In agreement with that, Cox-2 stain and the gene expression of cyclin D1 were also the most pronounced in the control group among the AOM-DSS induced groups. AOM-DSS treatment jeopardized the fecal bacteria profile and decreased the cecal short-chain fatty acid concentrations. The KGM and inulin supplement increased Bifidobacterium spp. and reduced Clostridium spp. concentration, and effectively increased the cecal short-chain fatty acid concentrations. Conclusion. This study suggested that supplementation of KGM and inulin (2% w/w diet in mouse, equivalent to 10 g/d in men) during the cancer promotion period could reduce the progression of colitis-associated colon carcinogenesis. The mechanisms mediating effects of these fibers may involve in the improvement of colonic ecology which ultimately reduced the cytokine-induced inflammation and proliferation-related gene expression in the distal colon.
參考文獻
延伸閱讀
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