Presented at the Neonatal Society 2007 Autumn Meeting.
Treece M1, Williams PJ1, McGivern R1, Litten JC2, Clarke L2, Symonds ME1, Mostyn A1
1 Centre for Reproduction and Early Life, Institute of Clinical Research, University Hospital, Nottingham NG7 2UH, UK
2 School of Agriculture, Policy & Development, University of Reading, RG6 6AR, UK
The endocrine function of subcutaneous adipose tissue is disturbed in obesity and this has implications for development of metabolic disease. Meishan pigs rapidly gain fat postnatally and become obese adults when compared to commercial breeds. Adiponectin is a recently discovered adipokine, secreted from adipose tissue (AT) and acts through its receptors; adiponectin receptor (adipoR) 1 and 2. Adipokine release and adipocyte differentiation is modulated, in part, by peroxisome proliferator activated receptor (PPAR)γ (Rosen et al 1999) and adiponectin concentrations decline prior to the onset of obesity (Yamauchi et al 2001). The aim of this study is to investigate the ontogeny of these key genes during rapid adipose tissue development in the neonatal pig.
Piglets from Meishan (n=13) and commercial (n=17) litters were ranked according to birth weight and 3 of median weight offspring were randomly assigned to tissue sampling on days 0, 4, 7, 14 and 21 of postnatal age, weight and lean mass were also measured on these days. Subcutaneous AT (SAT) was sampled after euthanasia with an overdose of sodium pentobarbitone (200 mg.kg-1). All procedures were in accordance with current UK legislation. Adiponectin and adipoR1 gene expression were determined using real-time PCR, PPARγ expression was determined using classical PCR. Results are expressed as mean values and standard errors normalised to 18S and were analysed by one-way ANOVA using SPSS version 12.
PPARγ was expressed in significantly greater abundance in commercial than Meishan piglets (P=0.001) during the first week of life. Adiponectin and AdipoR1 in Meishan piglets were expressed at levels below the sensitivity of the assay, but were detectable in commercial piglets. Age had no effect on the expression of either gene in commercial piglets.
In conclusion, low expression of adiponectin and adipoR1 in Meishan piglets is in accordance with theory that adiponectin declines in obesity, and that since this occurs even in neonates, it may be genetically, rather than environmentally regulated. Secondly, the low expression of all three genes in Meishan piglets may represent a delayed development of SAT in this breed; future histological analysis is required to confirm this hypothesis.
MT was supported by a Rank Prize Funds Summer Studentship.
References
Rosen, E.D. et al (1999) Molecular Cell 4, 611-617.
Yamauchi, T. et al (2001) Nature Medicine 7, 941-946.