Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2010
Publication Date: 3/20/2010
Citation: Sauer, J.A., Hyeran, J., Zimmerly, E., Kim, K., Liu, Z., Chanson, A., Smith, D., Mason, J.B., Friso, S., Choi, S. 2010. Aging and chronic alcohol consumption are determinants of p16 gene expression, genomic DNA methylation and p16 promoter methylation in the mouse colon. British Journal of Nutrition. 104(1):24-33. Interpretive Summary: Elder age and chronic alcohol consumption are important risk factors for the development of large bowel cancer. It is known that each factor can alter DNA methylation, a biological modification of DNA structure that can affect gene expression. In the present study we conducted an animal study using young and old mice to determine the effect of alcohol and aging on DNA methylation and expression of critical gene for the development of large bowel cancer. We found that aging has a remarkably robust and consistent impact on these molecular markers but alcohol and mild folate deficiency are more subtle and complex, indicating that the effect of alcohol and folate deficiency may be conducted not through DNA methylation. Further studies are needed to clarify the other mechanism by which chronic alcohol consumption affect the expression of critical genes during the colonic carcinogenesis.
Technical Abstract: Elder age and chronic alcohol consumption are important risk factors for the development of colon cancer. Each factor can alter genomic and gene-specific DNA methylation. This study examined the effects of aging and chronic alcohol consumption on genomic and p16-specific methylation, and p16 expression in the murine colon, aberrations of which are common in colorectal carcinogenesis. Old (18 months; n=70) and young (4 months; n=70) male C57BL/6 mice were pair-fed either a Lieber-DeCarli liquid diet with alcohol (18% of energy), a Lieber-DeCarli diet with alcohol (18%) and reduced folate (0.25 mg folate/L) or an isocaloric control diet (0.5 mg folate/L) for 5 or 10 weeks. p16 gene expression was measured using real-time RT-PCR. Genomic DNA methylation and p16 promoter methylation were analyzed by LC/MS and methylation-specific PCR, respectively. Genomic DNA methylation was lower in the colon of old mice compared to young mice (p<0.02) at 10 weeks. Alcohol consumption did not alter genomic DNA methylation in the old mouse colon, whereas it tended to decrease genomic DNA methylation in young mice (p=0.08). p16 promoter methylation and expression were higher in the old mouse colon in 3 diet groups compared to the corresponding young groups. There was a positive correlation between p16 promoter methylation and p16 expression in the old mouse colon (p<0.02). In young mice the combination of alcohol and reduced dietary folate led to significantly decreased p16 expression compared to the control group (p<0.02). Chronic alcohol consumption and aging alter genomic DNA methylation, p16 promoter methylation and p16 gene expression in the mouse colon, and dietary folate availability can further modify the relationship with alcohol in the young mouse. Further studies are needed to clarify the epigenetic mechanism by which chronic alcohol consumption and aging affect the expression of critical genes during the colonic carcinogenesis.