Lipogenic enzyme induction and incorporation of exogenous fatty acid into liver and liver nuclei.

The incorporation of exogenous fatty acid into lipids of liver and liver nuclei of rats fed diets with or without fat was compared. When [3H]palmitic acid was injected into rats, more radioactivity was incorporated into triacylglycerols and phospholipids of liver and liver nuclei from rats fed the fat-free diet than from those fed the fat diet. The results were supported further by an autoradiographic study. On the other hand, the enzyme induction and quantity of malic enzyme mRNA were decreased by fat feeding. Other lipogenic enzymes were also coordinately decreased. Thus, it may be possible that exogenous fatty acid is involved in nuclear regulation in addition to cytosolic regulation of lipogenic enzyme induction.