Supplementation of Seaweeds Extracts Suppresses Azoxymethane-induced Aberrant DNA Methylation in Colon and Liver of ICR Mice

BACKGROUND: Seamustard and seatangle are commonly consumed seaweeds in Korea and rich sources of non-digestible polysaccharides which possess biological activities. However anti-mutagenic and anti-cancer activities of these seaweeds under physiological condition have not been clarified yet. The objective of this study was to investigate the effect of seaweeds consumption on azoxymethane (AOM) -induced DNA methylation at N(7) and O(6) position of guanine base, an indicator of DNA damage related to cancer initiation. METHODS: Thirty ICR mice were divided into five groups and fed one of the following diets for two weeks: control diet, diet containing 10% water-soluble or water-insoluble fraction of seamustard or seatangle. After two weeks of experimental diet AOM was injected at 6 hours before sacrifice and N(7)-methylguanine (N(7)-meG) and O(6)-methylguanine (O(6)-meG) from the colon and liver DNA were quantified using a gas chromatography-mass spectroscopy. RESULTS: Water-soluble fractions of both seamustard and seatangle significantly reduced AOM-induced production of N(7)-meG guanine in colon and liver. Also water-soluble fractions of these seaweeds suppressed the level of methylation at O(6)-guanine of colon and liver directly responsible for tumorigenesis. While water-insoluble fraction of seamustard suppressed the production of N(7)-meG in liver this seaweed fraction decreased O(6)-meG and the ratio of O(6)/N(7)-meG in liver. Water insoluble fraction of seatangle decreased both O(6)- and N(7)-meG in colon and liver. Supplementation of all seaweeds extracts increased fecal weight of animals and the increase of fecal weight by water-insoluble fraction of seaweeds were higher than that by water-soluble fraction. CONCLUSION: Seamustard and seatangle intake may effectively prevent colon and liver carcinogenesis by decreasing DNA damage and the mechanism of inhibiting carcinogenesis by seaweeds in a long term study are warranted.