Clarify the mechanism of colon carcinogenesis by fat intake

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The aim of this study is to investigate the effect of conjugated linoleic acid (CLA) on colon carcinogenesis in rats fed with a high fat diet. Materials and Methods: Fifteen mg/kg body weight of azoxymethane (AOM) was i.p injected to male SD rats once a week for 2 weeks. Rats were fed with 10% beef tallow as a basal diet or supplemented with 1% CLA free fatty acid type (FFA) and triglyceride type (TG). Colonic aberrant crypt foci (ACF) was examined at 12 weeks. Colon cancer was examined at 44 weeks. Lipid peroxide level in serum was evaluated by thiobarbituric acid-reactive substance. Superoxide dismutase (SOD) activity was by WST-1 method. Prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) were by EIA. Colon proliferation was evaluated by BrdU uptake. Results: Both of CLA types decreased the number of ACFs and colon cancer incidence. CLA decreased BrdU uptake and expression of PGE2 and TXB2 in colonic mucosa. In rats fed with CLA without AOM, more BrdU uptook cells presented in lower area of crypt. Without CLA, more BrdU uptook cells presented in middle. Only FFA decreased oxidative stress. Conclusion: Despite long term feeding of a high fat diet, ingested CLA especially FFA was suggested to suppress colon carcinogenesis via arachidonate cascade. Decreasing and lower localization of BrdU uptook cells with CLA indicated that CLA itself played an important role in colon carcinogenicity. Furthermore, FFA was suggested to have higher efficacy than TG by decreasing oxidative stress.