Submitted to: Animal-The International Journal of Animal Biosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2017
Publication Date: 7/10/2017
Citation: Ramsay, T.G., Stoll, M.J., Blomberg, L., Caperna, T.J. 2017. Regulation of fetuin A gene expression in the neonatal pig liver. Animal-The International Journal of Animal Biosciences. doi:10.1017/S1751731117001410.
Interpretive Summary: Fetuin A is a serum protein whose concentration is extremely high in the fetal and neonatal pig. In fact, fetuin A is one of the major proteins in the serum at these ages. The level of this protein declines before weaning and reaches its lower limit at approximately six months of age. Unfortunately, we have no direct way to measure the protein in serum. We must rely on measurement of the expression of the gene for Fetuin A. Previous work has suggested that Fetuin A may be affected by growth rate. This led to the present work to determine whether fetuin A may be able to predict growth in the neonatal pig and thus be a marker for growth potential in swine. In addition, little is known of the regulation of this protein which is produced by the liver. Therefore, this study did two things. First it demonstrated that expression of the fetuin gene by the liver is increased when a neonatal pig grows poorly, as in the runt pig or the pig which fails to thrive and grows much slower than its littermates. Secondly, this study used isolated liver cells in cell culture to show that specific hormones (glucagon, triiodothyronine and growth hormone), factors of the immune system (tumor necrosis factor a, interleukin 6) and antioxidants can regulate fetuin A gene expression either positively or negatively. This is the first comprehensive report of the regulation of Fetuin A gene expression in any species and provides support for pursuing fetuin A as a potential marker for growth, health and animal well-being.
Technical Abstract: Fetuin A (also known as a2-Heremans-Schmid glycoprotein) is a protein primarily expressed by the liver and secreted into the blood. Previous studies have suggested that plasma concentrations of fetuin A are elevated with impaired growth rate in swine. The present study was designed to examine the relationship of porcine fetuin A with growth rate in the pig and to also elucidate the regulation of fetuin A expression by examining the hormonal and cytokine regulation of fetuin A mRNA abundance in hepatocytes prepared from suckling piglets. A quantitative real-time PCR assay was used to measure the number of fetuin A mRNA molecules/ng total RNA. Total RNA was isolated from liver of three different groups of pigs to assess changes in mRNA abundance of fetuin A: normal piglets at day 1, day 7 day 21 or 6 months of age (n = 6 for each age); runt and control piglets at day 1 of age (n = 4); slow growing and normal growing piglets at 21 days of age (n = 8). Following birth, fetuin A gene expression declines between 7 and 21 days of age (P < 0.05), with a much greater decline to 6 months of age (P < 0.01). Fetuin A mRNA abundance was higher in runt pigs versus their normal birth weight littermates (P < 0.05). Similarly, fetuin A gene expression was higher in livers of pigs that were born at a normal weight but that grew much slower than littermates with the same birth weight (P < 0.05). Hepatocytes were isolated from preweaned piglets and maintained in serum-free monolayer culture for up to 72 h to permit examination of the influences of hormones, cytokines, and redox modifiers on fetuin A mRNA abundance. Fetuin A gene expression was enhanced by glucagon, T3 and resveratrol (P < 0.05). Growth hormone, cytokines (IL6, TNFa) and antioxidants (n-acetylcysteine, quercertin) reduced fetuin A mRNA abundance (P < 0.05). A role for fetuin A in postnatal development is suggested by the differences in fetuin A mRNA abundance between runt piglets or slow growing piglets and their normal growing sized littermates. The hepatocyte experiments suggest multiple hormones and cytokines may contribute to the regulation of fetuin A during early growth of the pig.