Submitted to: Animal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2015
Publication Date: 5/1/2016
Citation: Ramsay, T.G., Blomberg, L., Caperna, T.J. 2016. a1-acid glycoprotein inhibits lipogenesis in neonatal swine adipose tissue. Animal. 10(5):812-20.
Interpretive Summary: Some serum proteins are involved in the response to inflammation or sickness and are described as acute phase proteins. A particular acute phase protein called alpha 1-acid glycoprotein (AGP) has unique properties in the pig. The serum concentration of AGP is extremely high in the fetal and neonatal pig and is in fact the major protein in the serum at these ages. The level of this protein very rapidly declines before weaning. The rapid decrease in serum AGP from birth to weaning coincides with the formation of body fat in the piglet which goes from less than 2% of the body weight at birth to 15% by weaning. This raised the question as to whether or not the high concentrations of serum AGP in the fetal and neonatal pig might interfere with the ability of the piglet to accumulate fat. This question is of importance to the swine industry as the health and growth of the pig are dependent upon adequate energy stores in the form of body fat. Studies in other species have shown that AGP can alter fat metabolism, so the present study was performed to determine if AGP can affect the metabolism of body fat in the piglet. Using cell and tissue culture, piglet fat tissue was incubated with increasing concentrations of pig AGP. Measurement of gene expression using molecular biology demonstrated that AGP reduced the expression of several enzymes essential for the formation of fat. The activity of some of the enzymes was also reduced in the tissue by treatment with AGP. Lastly, AGP reduced the overall ability to form fat from carbohydrate using highly sensitive assays to measure total synthesis of fat. These data clearly demonstrate that AGP inhibits fat formation in piglets and may contribute to the lack of body fat in the neonatal pig.
Technical Abstract: Serum a1-acid glycoprotein (AGP) is elevated during late gestation and at birth in the pig and rapidly declines postnatally. In contrast, the pig is born with minimal lipid stores in the adipose tissue, but rapidly accumulates lipid during the first week. The present study examined if AGP can affect adipose tissue metabolism in the neonatal pig. Isolated cell cultures or tissue explants were prepared from dorsal subcutaneous adipose tissue of preweaning piglets. Porcine AGP was used at concentrations of 0, 100, 1000 and 5000 ng/mL medium in 24 hours incubations. AGP reduced the mRNA abundance of the lipogenic enzymes malic enzyme (ME), fatty acid synthase (FASN) and acetyl coA carboxylase by at least 40% (p < 0.001). The activity of ME, FASN and citrate lyase were also reduced by AGP (p < 0.05). Glucose oxidation was unaffected by AGP (P > 0.05). However, 14C-glucose incorporation into fatty acids was reduced by approximately 25% by AGP treatment for 24 hours (P < 0.05). These data demonstrate an overall suppression of lipogenesis due to AGP inhibition of lipogenic gene expression in vitro, which suggests that AGP may have a role in the minimal lipid accumulation in newborn pig adipose tissue in vivo.