Influence of genotype on the discrepancy between UCP2 mRNA and protein expression in piglet subcutaneous adipose tissue (SCAT)

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University College London (2003) J Physiol 547P, C64

Oral Communications: Influence of genotype on the discrepancy between UCP2 mRNA and protein expression in piglet subcutaneous adipose tissue (SCAT)

A. Mostyn, J.C. Litten, K.S. Perkins, M.C. Alves-Guerra*, C. Pecqueur*, B. Miroux*, M.E. Symonds† and L. Clarke

Animal Research Group, Imperial College at Wye, Wye, Ashford, Kent TN25 5AH, †Academic Division of Child Health, School of Human Development, University Hospital, Nottingham NG7 2UH and *CEREMOD, 9 rue Jules Hetzel, 92190 Meudon, France

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Neonatal mortality is greater in the leaner commercial (C) porcine genotypes compared with the ancient Meishan (M) breed, which has a higher percentage of body fat. Piglets do not express UCP1, the mitochondrial protein primarily responsible for increasing heat production in neonatal mammals, although they do express UCP2 mRNA in SCAT (Damon et al. 2000). C piglets express higher levels of UCP2 mRNA in SCAT than M (Mostyn et al. 2002). However, differences in UCP2 mRNA do not always correlate with protein changes because of an upstream open reading frame in the UCP2 gene (Pecqueur et al. 2001). The present study aimed to determine whether the ontogeny of UCP2 protein abundance differed between C and M genotypes.

Piglets from 15 C and 15 M litters were ranked according to birth weight and the three median piglets were assigned to be randomly sampled on days 0, 4, 7, 14 or 21 of neonatal life. Piglets were weighed and colonic temperature measured on these days and a venous blood sample taken. SCAT was also sampled from each piglet following euthanasia with an overdose of barbiturate (100 mg kg-1 pentobarbital sodium: Euthatal). UCP2 mRNA was measured as described previously (Mostyn et al. 2002) and UCP2 protein abundance determined by immunoblotting using a fully validated UCP2 antibody (Pecqueur et al. 2001). Results, in arbitrary units (means ± S.E.M.), are expressed as a percentage of a reference sample present on all gels. Significant differences between breeds at each sampling age were assessed by GLM.

As shown in Table 1, UCP2 protein abundance was higher in M piglets at all ages except on the first day of birth. This difference was greatest on days 4 and 7, despite C piglets having higher UCP2 mRNA expression. UCP2 protein abundance was not correlated with UCP2 mRNA in either breed.

In conclusion, we confirm that changes in UCP2 protein can occur in the absence of a parallel change in mRNA, indicating that a post-transcriptional factor is critical in regulating expression of UCP2. Identification of the mechanism promoting this response in M piglets may subsequently enable neonatal survival to be enhanced in C breeds.

This work was supported by a BBSRC research grant.

Where applicable, experiments conform with Society ethical requirements.

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