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.