Vitamins and Carcinogenesis Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA.
Br J Nutr. 2010 Jul;104(1):24-30. doi: 10.1017/S0007114510000322. Epub 2010 Mar 8.
Older age, dietary folate and chronic alcohol consumption are important risk factors for the development of colon cancer. The present study examined the effects of ageing, folate and alcohol on genomic and p16-specific DNA methylation, and p16 expression in the murine colon. Old (aged 18 months; n 70) and young (aged 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 isoenergetic control diet (0.5 mg folate/l) for 5 or 10 weeks. Genomic DNA methylation, p16 promoter methylation and p16 gene expression were analysed by liquid chromatography-MS, methylation-specific PCR and real-time RT-PCR, respectively. Genomic DNA methylation was lower in the colon of old mice compared with 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 compared with 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 with the control group (P < 0.02). In conclusion, ageing and chronic alcohol consumption 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.
年龄较大、膳食叶酸和慢性酒精摄入是结肠癌发展的重要危险因素。本研究探讨了衰老、叶酸和酒精对老龄和年轻雄性 C57BL/6 小鼠结肠基因组和 p16 特异性 DNA 甲基化以及 p16 表达的影响。老龄（18 月龄；n 70）和年轻（4 月龄；n 70）雄性 C57BL/6 小鼠分别进行为期 5 或 10 周的以下喂养：Lieber-DeCarli 含酒精（能量的 18%）液体饮食、Lieber-DeCarli 含酒精（18%）和低叶酸（0.25mg 叶酸/L）饮食或等能量对照饮食（0.5mg 叶酸/L）。采用液相色谱-MS、甲基化特异性 PCR 和实时 RT-PCR 分别分析基因组 DNA 甲基化、p16 启动子甲基化和 p16 基因表达。与年轻小鼠相比，老龄小鼠结肠的基因组 DNA 甲基化水平在第 10 周时显著降低（P<0.02）。老龄小鼠的酒精摄入未改变其结肠的基因组 DNA 甲基化，而年轻小鼠的基因组 DNA 甲基化则呈下降趋势（P=0.08）。老龄小鼠结肠的 p16 启动子甲基化和表达均高于相应的年轻组。老龄小鼠结肠的 p16 启动子甲基化与 p16 表达呈正相关（P<0.02）。在年轻小鼠中，酒精和低膳食叶酸的联合作用导致 p16 表达明显低于对照组（P<0.02）。总之，衰老和慢性酒精摄入改变了小鼠结肠的基因组 DNA 甲基化、p16 启动子甲基化和 p16 基因表达，并且膳食叶酸的可利用性可以进一步改变年轻小鼠中酒精的关系。
