Effect of beta-carotene and wheat bran fiber on colonic aberrant crypt and tumor formation in rats exposed to azoxymethane and high dietary fat.
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.
Institute for Disease Prevention, George Washington University Medical Center, Washington, DC 20037.
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Alabaster
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Tang
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Frost
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Shivapurkar
D000818:Animals; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D001397:Azoxymethane / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D002338:Carotenoids / Q000627:therapeutic use*; D003043:Cocarcinogenesis; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000209:etiology* / Q000517:prevention & control*; D004041:Dietary Fats / Q000009:adverse effects*; D004043:Dietary Fiber / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D008297:Male; D011230:Precancerous Conditions / Q000139:chemically induced / Q000209:etiology* / Q000517:prevention & control*; D051381:Rats; D011916:Rats, Inbred F344; D014908:Triticum; D019207:beta Carotene
D016588:Anticarcinogenic Agents; D004041:Dietary Fats; D004043:Dietary Fiber; D019207:beta Carotene; D002338:Carotenoids; D001397:Azoxymethane