Metabolism of Very Low Density Lipoprotein-Triglyceride in Man

Abstract

Several methods have been used for estimating turnover of triglycerides (TG) in very low density lipoproteins (VLDL) of man. One technique has been to inject labelled precursors of TG and to analyze the resulting specific radioactivity curves of plasma VLDL-TG. Precursors have included labelled fatty acids and glycerol. The use of ³H-glycerol was developed by Farquhar et al. (1965) and has been used extensively for estimating VLDL-TG flux. In most previous studies estimations of VLDL-TG transport have been made by s ing le-exponential analysis. This was based on the observation that shortly after the injection of ³H-glycerol there is an initial build-up in specific activity of VLDL-TG followed by a single-exponential decay for several hours thereafter. The rate of this decay was assumed to represent the fractional catabolic rate (FCR) of VLDL-TG. However, in studies carried out for longer periods it has been noted that the fall in specific activity is not log-linear to zero, but after several hours the rate of decay declines producing a tail on the curve. During the past several years we have examined this latter phenomenon in some detail in conjunction with Drs. Loren Zech and Mones Berman at the National Institutes of Health. During the course of these studies a multi-compart- mental model has been developed for analysis of VLDL-TG kinetics ( Zech et al. 1979), and this method has been employed to examine these kinetics in a large group of subjects of normal and increased weight with and without hypertriglyceridemia (Grundy et al. 1979). In the following discussion, the major questions examined in these studies will be reviewed.

This research was supported by the Veterans Administration and NIH Grant HL-14197.