FIBER VOLATILE FATTY ACIDS AND COLONIC CELL BIOLOGY

挥发性脂肪酸(VFA)是在饮食或内源性时产生的 这些成分是由结肠中的微生物发酵的。一些膳食纤维 刺激VFA的形成。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，而且它有 推测VFA也可能影响结肠的PH值，以及 结肠功能。这些因素中的每一个似乎都影响着 结肠癌的发生。因为所需的适当标本 研究膳食纤维、挥发性脂肪酸与结肠细胞生物学的相互作用 不能从健康的人类那里获得，我们已经将猪培育成了一种 合适的动物模型。 在这项研究中，我们假设肠道中VFA的产生可以改变 通过饲喂不同的膳食纤维，这些纤维也可能影响 VFA在结肠粘膜细胞和血液中的吸收。我们进一步 假设粘膜细胞的生物学将受到 被吸收的VFA的量，管腔环境将 也会受到影响。为了验证我们的假设，猪将被喂食饲料 含有提纯或半提纯的纤维，这些纤维被选择来显示 溶解度、物理性质和可发酵性的范围。要确定 这些纤维对VFA的产生、吸收和排泄的影响， VFA将在盲肠内容物、门静脉血和粪便中进行测量。至 确定对细胞生物学、盲肠和结肠活检标本的影响 将检查细胞的增殖和分化情况。这个 膳食纤维、挥发性脂肪酸的产生与吸收、结肠细胞的关系 将确定结肠的生物学和管腔环境，以便 我们可以更准确地选择可能提供保护的纤维 治疗结肠病。 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 关于纤维在肿瘤发生中的作用的报道经常相互矛盾， 然后我们可以进一步检查那些最有可能 以保护结肠免受癌症侵袭。

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.