Wheat Bran Diet Reduces Tumor Incidence in a Rat Model of Colon Cancer Independent of Effects on Distal Luminal Butyrate Concentrations ,

Abstract

To investigate the effects of dietary fibers in colonic luminal physiology and their role in the prevention of colon cancer, a study was conducted using two diet groups and two treatment groups in a 2 x 2 factorial design. The two diets differed only in the type of dietary fiber, wheat bran and oat bran, and the two treatments were injection with the colon-specific carcinogen azoxymethane, or saline, as a control. There were 34 rats in the carcinogen-injected groups and 11 saline-injected rats per diet group. The goal of the study was to determine if a moderate consumption (6 g/100 g diet) of wheat bran or oat bran would alter the development of colonic tumors in this rat model of colon cancer, and if the differences in tumor incidence were correlated to luminal butyrate concentrations, luminal pH or fecal bulk. Short-chain fatty acid concentrations (SCFA) were measured in feces during the first half of the study (the promotion phase of tumor development) and again at the end of the study. Rats consuming oat bran had greater body weights (P < 0. 002), produced much larger concentrations of all SCFA, including butyrate, in both the proximal and distal colon (P < 0.0001), had more acidic luminal pH values (P < 0.0001), but also had significantly more development of colon tumors (P < 0.03). Alternatively, rats consuming wheat bran produced more typical molar ratios of the SCFA (65:10:20), had a relatively greater concentration of butyrate than propionate, and produced a larger volume (P < 0.05) and more bulky stool than the rats fed oat bran. The results of this study support other evidence that an acidic luminal pH is not protective in and of itself, and that diets containing wheat bran are protective against colon cancer development. In addition, these data show that large luminal butyrate concentrations in the distal colon alone, as were present in the rats consuming oat bran diets, are not protective of tumor development.

By-products of Rice Processing: An Overview of Health Benefits and Applications

“…Therefore, the presence of dietary fibre in high amounts in rice byproducts might partly explain its effects on the reduction of cancer. The dietary fibre in rice bran that ferments slowly may exert its protective effects through the physical dilution of the contents of the gut through its potential for dilution and faecal bulking capacity [90,91].…”

Histone deacetylase inhibitors: A novel target of anticancer therapy (Review)

“…Although the concentration of butyrate in the colonic lumen exceeds levels that inhibit proliferation of colon cancer cells in tissue culture, these concentrations still allow growth in the colonic crypt (54). A possible explanation, is that different dietary fibers may vary in their efficacy of increasing butyrate production (55,56), and possibly, the sensitivity of adenocarcinoma cells to butyrate can differ, at least in a tissue culture system (57). Combination of fluorouracil, phenylbutyrate, indomethacin and interferon-Á in treating patients with advanced colorectal cancer is now in process, and information regarding this clinical trial from National Cancer Institute, USA, can be found at the electronic address http://www.cancer.gov/cancer_information/.…”

Short-chain fatty acid formation at fermentation of indigestible carbohydrates

“…In rat models, high butyric acid concentration in the colon from fermentation of wheat bran, resistant starch and fructooligosaccharides has been shown to be protective against carcinogenesis in the colon of chemically induced cancer models (27,28). However, Zoran and co-workers found that wheat bran reduced tumour incidence in a rat model independently of butyric acid concentration (29).…”