Alabaster O, Tang Z, Frost A, Shivapurkar N
Institute for Disease Prevention, George Washington University Medical Center, Washington, DC 20037.
Carcinogenesis. 1995 Jan;16(1):127-32. doi: 10.1093/carcin/16.1.127.
The typical high-fat, low-fiber American diet promotes colon cancer. An alternative to radical changes in dietary habits is to reinforce the diet with cancer protectors. Experiments to evaluate the effects of beta-carotene in the presence of high fat and low and high dietary levels of wheat bran fiber were designed using the Fischer-344 rat colon cancer model. Rats (20/group), were given either high fat (20% w/w), low wheat bran, fiber (1% w/w) diets, or high fat (20% w/w) high wheat bran fiber (8% w/w) diets, with different levels of beta-carotene. After 2 weeks of adaptation, half were given two weekly s.c. injections of azoxymethane (AOM, 15 mg/kg body wt); and half two weekly s.c. injections of saline. Six weeks later, five rats from each dietary group were killed to evaluate the comparative effect of different dietary regimens on the induction of colon aberrant crypt foci (ACF). The remaining rats were maintained on their respective diets for an additional 20 weeks to examine the effect on colon tumor incidence. The total number of ACF/rat in the low-fiber groups declined from 44.0 +/- 4.18 to 12.8 +/- 1.95 in response to increasing amounts of beta-carotene from 1 to 20 mg/kg diet. A similar progressive reduction in total ACF/rat was also seen in the high-fiber groups (20.8 +/- 2.92 to 9.2 +/- 0.58). ACF did not develop in the saline-exposed groups. Similarly colon tumor incidence declined from 73% to 20% in high-fiber groups and from 27% to 13% in low-fiber groups in response to increasing amounts beta-carotene from 1 to 20 mg/kg diet. The results showed that beta-carotene and wheat bran, individually and when combined, protected the colon in rats consuming high-fat, western-style diets from ACF and benign or malignant tumor formation.
典型的高脂肪、低纤维的美式饮食会诱发结肠癌。除了彻底改变饮食习惯之外，另一种方法是在饮食中添加防癌物质。利用Fischer-344大鼠结肠癌模型，设计了实验来评估在高脂肪以及低、高膳食水平麦麸纤维存在的情况下β-胡萝卜素的作用。将大鼠（每组20只）分为两组，分别给予高脂肪（20% w/w）、低麦麸纤维（1% w/w）饮食，或高脂肪（20% w/w）、高麦麸纤维（8% w/w）饮食，并添加不同水平的β-胡萝卜素。适应2周后，一半大鼠每周皮下注射两次偶氮甲烷（AOM，15 mg/kg体重）；另一半大鼠每周皮下注射两次生理盐水。6周后，处死每个饮食组的5只大鼠，以评估不同饮食方案对结肠异常隐窝灶（ACF）诱导的比较效果。其余大鼠继续各自的饮食20周，以检查对结肠肿瘤发生率的影响。随着饮食中β-胡萝卜素含量从1 mg/kg增加到20 mg/kg，低纤维组大鼠的ACF总数从44.0±4.18降至12.8±1.95。高纤维组大鼠的ACF总数也有类似的逐渐减少（从20.8±2.92降至9.2±0.58）。生理盐水处理组未出现ACF。同样，随着饮食中β-胡萝卜素含量从1 mg/kg增加到20 mg/kg，高纤维组的结肠肿瘤发生率从73%降至20%，低纤维组从27%降至13%。结果表明β-胡萝卜素和麦麸，单独使用或联合使用时，可保护食用高脂肪西式饮食的大鼠结肠免受ACF以及良性或恶性肿瘤的形成。
