Chemoprevention of azoxymethane-induced rat colon carcinogenesis by seatangle, a fiber-rich seaweed

Abstract

Seaweeds are rich sources of dietary fiber which possess diverse physiological functions in the colon. In the present study, the modulating effect of feeding seatangle (Laminaria japonica), a fiber-rich seaweed, on initiation and postinitiation of rat colon carcinogenesis was investigated. Four groups of animals were exposed to two weekly injections of a chemical carcinogen azoxymethane (AOM). Animals were fed a fiber-free semisynthetic diet or a diet containing 15% seatangle (4.7 g dietary fiber/100 g diet) during initiation, postinitiation or initiation postinitiation phase of carcinogenesis. Study results showed that animals fed the seatangle-containing diet had a significantly decreased number of both aberrant crypts and aberrant crypt foci in the colon. Also, labeling indices and proliferation zones were signi- ficantly reduced in the colon of the rats fed a seatangle diet. All of the seatangle feeding regimens used in this study were effective in reducing aberrant crypt formation indicating anticarcinogenic effects are mediated through both the blocking of initiation and the suppression of cell proliferation in initiated cells. These results suggest that a diet containing seatangle may decrease the risk of developing colon cancer although the precise cellular mechanisms involved in anticarcinogenic effects of seatangle should be further examined.