Effects of diet on hepatic triglyceride synthesis.

The effects of diet on the rate of triglyceride synthesis by rat liver homogenates was measured. Changes in triglyceride synthesis were correlated with the level of activity of L-alpha-glycerophosphate acyltransferase, the enzyme catalyzing the first specific reaction in hepatic glycerolipid synthesis. Fasting for 48-72 hr depressed the synthesis of triglyceride from L-alpha-glycerophosphate. High carbohydrate diets, fed to rats for 6 days, resulted in increased triglyceride synthesis. Diets high in starch were less effective than high glucose, sucrose, or fructose diets in increasing triglyceride synthesis. Diets high in corn oil did not alter triglyceride synthesis. These studies established the importance of dietary factors in the regulation of hepatic triglyceride synthesis.L-alpha-Glycerophosphate acyltransferase activity was measured after the same dietary changes. Both high carbohydrate and high fat diets resulted in increased enzyme specific activity. Fasting for 72 hr did not decrease activity. Thus, the specific activity of this enzyme did not correlate well with the measured rate of triglyceride synthesis indicating that other factors must participate in the regulation of triglyceride biosynthesis.