139 LOW DENSITY LIPOPROTEINS IIETEROGENEITY AND INTRAVENOUS FAT IN NEONATES.

Abstract

Background: The properties of iv-fat emulsions are similar to those of triglyceride-rich plasma lipoproteins and are rapidly hydrolyzed by lipoprotein lipase. Neonates frequently do not tolerate iv-fat because of low levels of the key enzymes for fat metabolism. Purpose of the study: We examined the effect of iv- fat therapy on Low Density Lipoproteins (LDL) subclass distribution of 20 neonates unable to tolerate enteral feeding. Methods: Particle size was determined by non-denaturing gradient gel electrophoresis. Results: The LDL size distribution profiles at baseline showed unexpected diversity in the position of the major lipoprotein peak with three different profiles identified by peak position; profile I with a major peak of large sized LDL (26.3-28.2 nm), profile II with a major peak at 25.2-26.7 nm and profile III with a major peak of small sized particles (24.9-25.6 nm). None of the profiles fit the classical LDL pattern A or B found in adult plasma since the skewedness associated with the adult pattern was not present. With iv fat feeding and with enteral nutrition no major shift in peak position was observed, even though plasma triglyceride and apo B concentrations increased suggesting that there was an increased number of LDL particles rather than an increase in size of particles. Conclusion: The constancy of the LDL peak position in the face of increases in plasma triglyceride and apo B concentrations during iv fat and onset of enteral nutrition in neonates suggests that other metabolic events, such as hormone status and lipid and transfer protein activities need to be considered