Abstract
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 mumol 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 (t1/2 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 4.8%, respectively). Lipoprotein lipase activities in leg muscle and heart were consistently greater in the low-VLDL line and beta-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 mumol/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 partitioning of VLDL triglyceride between adipose and other tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
Highlights
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
The rate of accumulation was initially linear but began to decrease after about 20 min. Both "C-labeled VLDL injected 1 min after the antibody and 3H-labeled VLDL injected after 20 min were cleared very slowly from the circulation. This suggests that the decline in rate of VLDL accumulation was due to a decrease in rate of VLDL secretion rather than a reduction in the effectiveness of the antibody with time
The results of the present study suggest that differences in plasma VLDL concentration produced by divergent genetic selection for plasma VLDL in broiler chickens are primarily the result of differences in rate of hepatic VLDL secretion
Summary
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. 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). 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 amajmc;4uSe &their Iw rate of VLDL secretion and makes iin imppngaat cpritrikn&q.to improved o@ciency of protein utilization. Lipoprotein metabolism in lean and in fat chickens produced by divergent selection for plasma very low density lipoprotein concentration. Plasma lipid transport in immature birds [1] is similar to that in mammals, dietary fatty acids are absorbed directly into the portal vein (as nonesterified fatty acids and portomicrons) rather than through the lymphatic system [2, 3]
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