First evidence of uncoupling protein-2 (UCP-2) and -3 (UCP-3) gene expression in piglet skeletal muscle and adipose tissue

Uncoupling proteins (UCPs) facilitate proton transport inside the mitochond ria and decrease the proton gradient, leading to heat production. Until now , the presence of UCP1 or other UCP homologs had not been detected in tissu es of pig, a species where evidence for the presence of brown adipose tissu e has only been provided in 2-3 month old animals. In the light of the impr oving knowledge on the UCPs family, we decided to examine both UCP? and UCP 3 mRNA expression in piglet skeletal muscle and adipose tissue. Using RT-PC R we have successfully cloned a partial UCP2 sequence and a complete UCP3 c DNA. UCP3's open reading frame (936 bp) shares 90, 89 and 85% similarity wi th bovine, human and rat UCP3 nucleotide sequences, respectively. In 3-5 da y old piglets, these genes are expressed in adipose tissue and in both long issimus thoracis (LT) and rhomboideus (RH) muscles, without any effect of m uscle metabolic type. This is in good agreement with the measurement of the same membrane potential in mitochondria isolated from both types of muscle s. In triiodothyronine-treated piglets, UCP3 mRNA is more expressed in LT t han in RH muscle. These genes may be involved in the control of the energy metabolism of the piglet. (C) 2000 Elsevier Science B.V. All rights reserve d.