DNA Methylation and Hepatocarcinogenesis in Rats Fed a Choline-devoid Diet

Groups of male Fischer-344 rats were fed either a choline-supplemented or a choline-devoid (CD) diet, for up to 14 months. In rats fed the CD diet, hepatic lesions developed and progressed through two distinct stages, the first characterized by severe steatosis and an increase in cell turnover and the second by gradual clearance of the deposited fat, fibrosis and parenchymal nodularity. Large hepatocellular carcinomas were found in rats killed at 14 months. DNA was purified from the livers of all groups of rats and from the tumors, and its level of methylation was analyzed using the restriction endonucleases HpaII and MspI. DNA undermethylation was detected only in the livers of rats fed the CD diet for 14 months, whether bearing tumors or not, and in three of four hepatocellular carcinomas. Undermethylation of liver total DNA is therefore a late effect of dietary choline deficiency in the rat.