Bile acids are normal components of the luminal contents of gastrointestinal tract but have been reported to cause oxidative damage by stimulating the generation of free oxygen radicals from the mitochondria. Several studies have demonstrated the contribution of reactive species to mutagenesis, carcinogenesis and tumor promotion. There is accumulating evidence to show that some carbohydrates and carbohydrate-containing molecules possess antioxidant ability by inhibiting the production of reactive species. Prebiotics are complex carbohydrates which have been shown to improve gut health when used in combination with probiotics. However, there is paucity of data on how prebiotics alone affect gut health and by which mechanism of action. The reactive oxygen scavenging ability of inulin, a prebiotic, has been shown in vitro in non-cell based system and in mice. The anti-inflammatory effect, through production of short chain fatty acids by fermentable inulin has also been shown. However, the mechanism of inulin in the amelioration of bile acid induced cancer remains unknown.
Methods: Three different cell-lines (colon stem cells, human colon carcinoma cells-HCT-116 and control normal colon epithelial cells) will be examined. Cells will be treated separately with secondary bile acids, primary bile acids and prebiotics. Cells will also be treated with microorganisms' filtrate such as probiotics (bifidobacteria) in conjunction with secondary bile acids, primary bile acids or prebiotics. Production of free radicals will be measured using nitro blue tetrazolium chloride assay (NBT) and inflammatory proteins will be measured using RT-PCR. DNA damage will be assessed using Endonuclease 111 enzyme modified Comet assay. In addition, C1 Single-Cell auto pep system will be used for mRNA sequencing of individual cells within the well plate.
This study hypothesized that normal cells exposed to secondary bile acids in the presence of inulin may be protected from transformation to cancer cells and this may correlate with decrease in production of reactive radicals and pro-inflammatory proteins. The anti inflammatory ability of short chain fatty acid and antioxidant ability of inulin may possibly be associated with AMP-activated protein kinase (AMPK), phosphatidylinositol 3-kinase (P13-K), NF-κB signaling pathways. Thus inulin and their fermentation/breakdown products may not only stimulate beneficial bacteria in the colon but may directly interfere with absorption and cellular metabolism processes in the colon.
Citation Format: Bene Akromaa Afolabi, Sandra Appiah, Azra Pachenari, Lucy Ghali. Impacts of inulin on bile acids induced colon cancer. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B01.