Lipotrope deficiency in experimental carcinogenesis

Abstract

Diets deficient in lipotropes (methionine, choline, and folate) and high in fat increase hepatocarcinogenesis by many chemicals, including aflatoxin B1 (AFB1) and N‐2‐fluor‐enylacetamide (AAF). The increase can be corrected in most cases by lipotrope supplementation, but the degree of correction appears to be influenced by the type of fat in the diet. A lipotrope‐deficient, high‐fat diet also increases dimethylhydrazine carcinogenesis in the colon, an effect due to the dietary fat content, not to lipotrope deficiency. In contrast, mammary carcinogenesis by dimethylbenzanthrene or AAF is decreased or unchanged in rats fed the deficient diet.

Hepatic microsomal oxidase activity, cytochrome P450 and conversion of AFB 1 to a bacterial mutagen all are decreased in assays in vitro using tissues from lipotrope‐deficient rats. However, urine mutagen content is increased after AFB1 treatment, as is urine content of activated AAF. AFB1 binding to hepatic DNA in vivo is unchanged or is slightly decreased. Therefore, there is evidence that the dietary deficiency influences carcinogen activation, but the expression and direction of the effect varies. The deficiency also increases cell division in the liver and decreases hepatic s‐adenosylmethionine; carcinogenesis may be influenced by either or both of those changes.