Ractopamine efect on lipid metabolism and GLUT4 amount of fnishing pigs

Abstract

Ractopamine (RAC) causes fat deposition and/or fatty acid synthesis reduction and increases the rate of protein synthesisand muscle growth. However, there are few scientifc studies detailing the mechanism of action of RAC and its possible metabolicpathways in swine. The objective of this study was to evaluate the effect of RAC on lipid metabolism of fnishing pigs. Subcutaneous andretroperitoneal fat, muscle, and blood samples were collected at slaughter. Forty pigs were fed diferent RAC levels (ppm): 0, 5, 10, 15,and 20. RAC did not afect lipoprotein lipase activity in any of the tissues. Tere were no changes in insulin levels, but a linear increasein serum triacylglycerol, total cholesterol, and HDL-cholesterol (HDL-c) was seen. Te insulin-dependent glucose transport (GLUT4)and fatty acid synthase amounts present in animals adipose tissue did not difer, but the muscle GLUT4 presented a negative quadraticeffect. Te smallest GLUT4 amount (0.959) was estimated for 15.5 ppm of RAC. Serum glucose increased linearly, while a linear decreasein glycogen content was detected. Te results indicate that RAC acts upon lipid metabolism in order to stimulate lipolysis, while thereare changes in carbohydrate metabolism that might support lean growth in these animals.