Early effect of myo-inositol deficiency on fatty acid synthetic enzymes of rat liver.

Young rats (100 g) were fed either a purified myo-inositol-deficient balanced diet or a control diet containing 0.5% by weight myo-inositol, ad libitum, for up to 2 weeks following a 48 h fast. Weight gain was the same for animals in both groups. Liver triacylglycerol levels in the deficient animals were 1.8-, 3.5- and 3.0-fold higher than the corresponding levels in the control animals after 4, 8 and 14 days of feeding, respectively. In the myo-inositol-deficient group the specific activities of liver fatty acid synthetase and acetyl-CoA carboxylase were elevated 1.5-2.0-fold over controls, reaching a maximum after 3-4 days of feeding. Subsequently, activities declined to control levels. Rates of fatty acid synthetase synthesis in the deficient group, as measured by [3H]leucine incorporation into immunoprecipitable fatty acid synthetase polypeptide, were significantly higher (1.5-2.0-fold) than controls after 12-18 h of feeding and then declined to control levels by 1 day. No difference was noted between groups in either the rate of total, soluble liver protein synthesis or the half-life of fatty acid synthetase over this time period. These results suggest that the liver lipodystrophy observed during myo-inositol deficiency in rats may be due in part to elevated levels of lipogenic enzymes in this tissue in the early stage of the deficiency.