Plasma lipoprotein metabolism in lean and in fat

Plasma lipoprotein metabolism was studied in vivo in two lines of chickens produced by selection for high and low plasma very low density lipoprotein (VLDL) concentration. Rates of VLDL secretion were measured by determining the rate of accumulation of triglyceride in the plasma after intravenous injection of anti-lipoprotein lipase antibody. The clearance of VLDL-triglyceride and its uptake into liver and adipose tissue was examined using radioactively labeled VLDL synthesized in vivo. The rate of VLDL secretion was about threefold higher in the high-VLDL line as compared to the leaner, low VLDL-line (6.7 vs 2.1 pmol VLDL triglyceride/h per ml of plasma). The clearance of VLDL from the circulation of the low VLDL line was much faster than that of the high VLDL line (tu2 of 3.7 and 13.6 min, respectively). The proportion of administered radiolabel taken up by the abdominal fat pad was substantially greater in the fat line than in the lean line (11.9 vs 4.876, respectively). Lipoprotein lipase acitivities in leg muscle and heart were consistently greater in the low-VLDL line and B-hydroxybutyrate concentrations in the plasma of the low-VLDL line were significantly greater than those in the high-VLDL line (0.86 vs 0.48 fimol/ml). The results show that the approximately tenfold difference in plasma VLDL concentration between lines is primarily due to markedly different rates of hepatic VLDL production and that selection has made a major effect on partitionin W e pmpose that a direction of fatty acids to oxida$ion rather than VLDL ayp&esis in the liver of birds of the low-VLDL line is amajm c;4uSe &their Iw rate of VLDL secretion and makes iin imppngaat cpritrikn&q.to improved o@ciency of protein utilization. In addiiiatl, preferential use of VLDL-triglyceride and B-hydmxyihtyrate may reduce amino acid oxidation by muscle.G r i h , H., E Acamovic, K. Guo, and J. Peddie. Lipoprotein metabolism in lean and in fat chickens produced by divergent selection for plasma very low density lipoprotein concentration. J. Lipid Res. 1989. 3