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Absence of an inhibitory effect of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis in rats fed low- or high-fat diets

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Author: Rijnkels, J.M. · Hollanders, V.M.H. · Woutersen, R.A. · Koeman, J.H. · Alink, G.M.
Type:article
Date:1998
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Nutrition and Cancer, 2, 30, 124-129
Identifier: 234469
Keywords: Nutrition · Azoxymethane · Animal experiment · Animal model · Animal tissue · Article · Carcinogenesis · Colorectal cancer · Controlled study · Dietary intake · Fruit · Lipid diet · Low fat diet · Male · Nonhuman · Rat · Tumor promotion · Tumor volume · Vegetable · Adenocarcinoma · Adenoma · Animals · Azoxymethane · Carcinogens · Colorectal Neoplasms · Diet · Diet, Fat-Restricted · Dietary Fats · Fruit · Male · Rats · Rats, Inbred F344 · Vegetables

Abstract

The potential inhibitory effects of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis were examined in rats fed low- or high-fat diets. Rats were fed low-fat diets (20 energy percent, Diets A and B) or high-fat diets (40 energy percent, Diets C and D), supplemented with a vegetables-fruit mixture (19.5% wt/wt, Diets B and D) or unsupplemented (Diets A and C) for 36 weeks. After the animals were maintained on the respective diets for four weeks, they were given three weekly injections of azoxymethane at 15 mg/kg body wt sc. Eight weeks after the start of the study, animals maintained on Diet A were switched to Diet B or C or maintained on the same diet. Animals maintained on Diet B or D were switched to Diet A or C, respectively. Furthermore, animals maintained on Diet C were switched to Diet A or D or maintained on the same diet. Multiplicity of colorectal tumors did not differ between groups fed a vegetables-fruit mixture during the initiation or the promotion phase (Group B → A vs. Group A → B; Group D → C vs. Group C → D). However, multiplicity was significantly lower in animals fed low-fat diets than in animals fed high-fat diets in combination with a vegetables- fruit mixture (Group A → B/B → A vs. Group C → D/D → C). Furthermore, multiplicity was significantly increased in groups fed a high-fat diet during the promotion phase only in comparison with animals fed a low-fat diet during the whole experiment (Group A → C vs. Group A → A). No other differences in multiplicity or tumor incidences were observed among the eight experimental groups.