Influence of genotype on the differential ontogeny of uncoupling protein 2 and 3 in subcutaneous adipose tissue and muscle in neonatal pigs

The present study aimed to determine whether porcine genotype and/or postnatal age influenced mRNA abundance or protein expression of uncoupling protein (UCP)2 or 3 in subcutaneous adipose tissue (AT) and skeletal muscle (SM) and the extent to which these differences are associated with breed-specific discordance in endocrine and metabolic profiles. Piglets from commercial and Meishan litters were ranked according to birth weight. Tissue samples were obtained from the three median piglets from each litter on either day 0, 4, 7, 14 or 21 of neonatal life. UCP2 protein abundance in AT was similar between genotypes on the first day of life, but it was elevated at all subsequent postnatal ages (P<0.05) in AT of Meishan piglets. In contrast, UCP2 mRNA abundance was lower in Meishans up to 14 days of age. UCP2 mRNA expression was not correlated with protein abundance in either breed at any age. UCP3 mRNA in AT was similar between breeds up to day 7; thereafter, expression was higher (general linear model, P<0.05) in Meishan piglets. Conversely, UCP3 mRNA expression in SM was higher in commercial piglets after day 7. Colonic temperature remained lower in Meishan than commercial piglets throughout the study; this was most obvious in the immediate post-partum period when Meishan piglets had lower (P<0.05) plasma triiodothyronine. In conclusion, we have demonstrated that porcine genotype influences the expression and abundance of UCP2 and 3, an influence which may, in part, be due to the distinctive endocrine profiles associated with each genotype.