Nutr Res Pract.  2008 Jun;2(2):55-61.

Dose-response assessment of the anti-cancer efficacy of soy isoflavones in dimethylhydrazine-treated rats fed 6% fructooligosaccharide

• Sung HY
• Choi YS

Abstract

We investigated the combinatorial effects of different doses of dietary soy isoflavones (SI) and fructooligosaccharide (FOS) in a rat model of colon cancer. We hypothesized that increased bioavailability of SI metabolites due to dietary FOS may increase production of bioactive equol and affect colon carcinogenesis in a dose-dependent manner. Sprague-Dawley male rats were injected with 12-dimethylhydrazine (DMH) and were provided experimental diets that contained 0, 10, 50, 150, or 500 mg SI per kg of diet and 6% FOS for 12 weeks. The number of aberrant crypt foci (ACF) and the expression of cyclooxygenase-2 (COX-2) in colonic tissues were significantly decreased in the 6% FOS-fed groups compared to the control group. Gut transit time and fecal pH were significantly lower, and fecal concentrations of bifidobacteria were increased with 6% FOS. However, dietary SI supplementation in combination with 6% dietary FOS did not affect ACF formation or COX-2 expression. Plasma equol concentrations were dose-dependently increased by supplementation of SI up to 500 mg/kg of diet. In conclusion, SI supplementation up to 500 mg/kg of diet appeared to have no additive beneficial effects in rats with chemically-induced colon cancer that were fed 6% FOS, although plasma equol was dose-dependently increased.

Keyword

Aberrant crypt foci; cyclooxygenase-2; fructooligosaccharide; soy isoflavone; colon cancer

MeSH Terms

Aberrant Crypt Foci
Animals
Biological Availability
Colon
Colonic Neoplasms
Cyclooxygenase 2
Diet
Equol
Humans
Hydrogen-Ion Concentration
Isoflavones
Male
Oligosaccharides
Plasma
Rats
Cyclooxygenase 2
Equol
Isoflavones
Oligosaccharides

Figure

• 

  Fig. 1 Effects of different doses of soy isoflavones (SI) on fecal pH and gut transit time in DMH-treated rats fed a diet containing fructooligosaccharide (FOS). Rats were fed experimental diets that contained 0, 10, 50, 150, or 500 mg SI per kg diet and 6% FOS for 12 weeks. Data are mean ± SE values (n = 10). a,b,cMeans with different letters are significantly different from each other by Duncan's multiple range test at p < .05.

• 

  Fig. 2 Effects of different doses of soy isoflavones (SI) and fructooligosaccharide (FOS) on plasma equol concentrations in DMH-treated rats. Rats were fed experimental diets that contained 0, 10, 50, 150, or 500 mg SI per kg diet and 6% FOS for 12 weeks. Data are mean ± SE values (n = 10). a,b,cMeans with different letters are significantly different from each other by Duncan's multiple range test at p < .05.

• 

  Fig. 3 Effects of different doses of soy isoflavones (SI) and fructooligosaccharide (FOS) on numbers of (top) ACF and (bottom) ACF with four or more ACs per focus in the colons of DMH-treated rats. Rats were fed experimental diets that contained 0, 10, 50, 150, or 500 mg SI per kg diet and 6% FOS for 12 weeks. Data are mean ± SE values (n = 10). a,bMeans with different letters are significantly different from each other by Duncan's multiple range test at p < .05.

• 

  Fig. 4 Effects of different doses of soy isoflavones (SI) and fructooligosaccharide (FOS) on COX-2 protein levels in colonic tissues of DMH-treated rats. Rats were fed experimental diets that contained 0, 10, 50, 150, or 500 mg SI per kg diet and 6% FOS for 12 weeks. Data are mean ± SE values (n = 10). a,bMeans with different letters are significantly different from each other by Duncan's multiple range test at p < .05.

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