FIBER VOLATILE FATTY ACIDS AND COLONIC CELL BIOLOGY

挥发性脂肪酸（VFA）是由膳食或内源性 这些成分在结肠中被微生物发酵。 一些膳食纤维 刺激VFA形成。 VFA已被证明影响分化 以及正常和恶性结肠粘膜细胞的增殖， 据推测，VFA也可能影响结肠的pH值， 结肠功能 这些因素中的每一个似乎都会影响 结肠癌发生 因为我们需要合适的标本 研究膳食纤维、VFA和结肠细胞生物学的相互作用 不能从健康的人类获得，我们已经开发了猪作为一种 合适的动物模型。 在这项研究中，我们假设肠道中VFA的产生可以被改变， 通过喂养不同的膳食纤维，纤维也可能影响 VFA被结肠粘膜细胞和血液吸收。 我们进一步 假设粘膜细胞的生物学将受到 的量的VFA被吸收，并认为内腔环境将 也受到影响。 为了验证我们的假设，猪将被喂食 含有纯化或半纯化的纤维，所述纤维被选择以显示 溶解度、物理性质和发酵性的范围。 以确定 这些纤维对VFA产生、吸收和排泄的影响， 将在盲肠内容物、门静脉血和粪便中测量VFA。 到 确定对细胞生物学、盲肠和结肠活检标本的影响 将检查细胞增殖和分化。 的 膳食纤维，VFA产生和吸收，结肠细胞 将确定结肠的生物学和内腔环境 我们可以更准确地选择可能提供保护的纤维， 对抗结肠疾病 这项研究旨在提供数据，以确定具体的 纤维对结肠环境和结肠细胞的影响 健康动物的生物学 从这些数据中我们可以理解为什么 关于纤维对肿瘤发生的影响的报道经常相互矛盾， 然后我们可以进一步检查这些纤维 来保护结肠免受癌症的侵害

Volatile fatty acids (VFA) are produced when dietary or endogenous constituents are fermented by microbes in the colon. Some dietary fibers stimulate VFA formation. VFA have been shown to influence differentiation and proliferation of normal and malignant colinic mucosal cells, and it has been postulated that VFA may also influence the pH of the colon, and colonic function. Each of these factors appears to influence the risk of colonic carcinogenesis. Since the appropriate specimens which are needed to study the interactions of dietary fiber, VFA and colonic cell biology cannot be acquired from healthy humans, we have developed the pig as an appropriate animal model. In this study, we postulate that VFA production in the gut can be altered by feeding different dietary fibers, and that the fibers may also influence absorption of VFA into the colonic mucosal cells and blood. We further postulate that the biology of the mucosal cells will be influenced by the quantity of VFA which are absorbed, and that the lumenal environment will also be affected. To test our hypothesis, pigs will be fed diets containing purified or semi-purified fibers which are selected to show a range in solubility, physical properties and fermentability. To determine the influence of these fibers on VFA production, absorption and excretion, VFA will be measured in cecal contents, portal blood and feces. To determine the influence on cell biology, cecal and colonic biopsy specimens will be examined for cell proliferation and differentiation. The relationships of dietary fiber, VFA production and absorption, colonic cell biology and the lumenal environment of the colon will be determined so that we can more accurately select fibers which are likely to offer protection against colonic disease. This study is designed to provide data which will identify the specific effects that fibers have on the colonic environment and on the colonic cell biology of a healthy animal. From these data we may understand why there are often conflicting reports on the effect of a fiber on tumorigenesis, and we can then go on to further examine those fibers which are most likely to protect the colon against cancer.