Secretion and Turnover of Very Low Density Lipoprotein Triacylglycerols in Rats Fed Chronically Diets Rich in Glucose and Fructose

Abstract

Very low density lipoproteins (VLDL) were isolated from serum after intravenous injection of rats with 1-¹⁴C-palmitic acid. These lipoproteins were in turn injected into tail veins of rats which had been fed ad libitum for 21 days on fat-free diets in which the source of carbohydrates was glucose or fructose. Groups of rats were killed at intervals up to 10 minutes after injection and the rates of decline of serum triacylglycerol (TG) and of serum VLDL-TG specific radioactivity were measured. The half-lives of VLDL-TG turnover were very short (approximately 1 minute in both groups) compared to those described previously for rats fed conventional diets or for fasted animals, but the higher plasma TG concentrations in fructose-fed rats were as reported elsewhere. From this information and the serum VLDL-TG concentrations in the two dietary groups, it was possible to estimate the rate of VLDL secretion from the liver which was found to be 75% greater in the fructose-fed rats. No differences were found in the total lipoprotein lipase activity in acetone powders of white adipose tissue from other rats fed fructose and glucose.