Effects of dietary lipids on hepatic protein synthesis and lipid metabolism in the rat

¹ Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts

The effects of dietary cholesterol, cholic acid, or high fat on hepatic protein synthesis were studied in rats. The feeding of 1.5% cholesterol or 20% corn oil in the diet caused significant inhibition of leucine-C¹⁴ incorporation into protein in vitro; the effect of 0.5% cholic acid was less striking. The feeding of a diet containing all three factors (cholesterol, cholic acid, and high fat) resulted in the greatest inhibition of hepatic protein synthesis in vitro. This dietary effect was confirmed in vivo when methionine-S³⁵ incorporation into liver proteins was measured in male and female rats. Comparison between the control purified diet and laboratory chow showed no differences. Appropriate experiments in vitro employing 105,000-g cell sap fractions and microsomes ruled out any apparent effect of diet on the activation and transfer of leucine-C¹⁴ to the microsomal templates. Furthermore, no effect was noted in leucine-C¹⁴ incorporation into soluble RNA in vitro. It appears that the changes in protein synthesis are consistently associated with a "defect" in the microsomal fraction.

Key Words: diet and hepatic protein synthesis • methionine-S³⁵ incorporation into liver fractions in vivo • leucine-C¹⁴ incorporation into liver fractions in vitro • leucine-C¹⁴ incorporation into soluble RNA in vitro • diet and microsomal protein synthesis

Submitted on September 15, 1964