Ontogeny of adipokine expression in neonatal pig adipose tissue

Authors: Ramsay, Timothy; Caperna, Thomas

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2008
Publication Date: 1/1/2009
Citation: Ramsay, T.G., Caperna, T.J. 2009. Ontogeny of adipokine expression in neonatal pig adipose tissue. Comparative Biochemistry and Physiology. 152:72-78.

Interpretive Summary: Recent studies have demonstrated that adipose tissue produces a number of cytokines, hormones and growth factors that can impact health and metabolism. These various proteins have now been grouped and are described by the name “adipokines”. These adipokines have been examined for their potential roles in humans and rodents. A few initial studies have shown some of these adipokines are produced in swine adipose tissue. The present study was designed to examine a variety of these adipokines for their expression in the neonatal pig. This is the first study to characterize the development of adipokine expression in any species during the neonatal period, a critical time for the development of adipose tissue and for the survival of the baby pig. Adipokines that were examined included leptin, adiponectin, tumor necrosis factor a, interleukin 1ß (IL1ß), IL6, IL8, IL10, IL15, haptoglobin, vascular endothelial growth factor, macrophage migration inhibitory factor and monocyte chemotactic protein 1. The adipose tissue from neonatal pigs at the ages of 1, 4, 7, and 21 days of age were collected and extracted for RNA content. The RNA was then used for real-time PCR to assess the relative expression of these genes during neonatal development of the adipose tissue. The expression of the genes could be divided into three groups: expressed highly in adipocytes, expressed in adipocytes and the supporting cell types, or expressed primarily in the supporting cell types. The development of gene expression for each adipokine varied depending upon cell type of origin, the adipose tissue location and the type of adipokine. This study provides critical information for further research to determine if these adipokine genes respond to stressors(environmental, immunological or nutritional) and what impact they might have on neonatal survival.

Technical Abstract: This study examined ontogeny of development for a range of adipokines in neonatal adipose tissue. Pigs were selected across six litters for sampling at d1, d4, d7 or d21 of age. Subcutaneous (SQ) and perirenal (PR) adipose tissue were collected and extracted for total RNA. SQ was also collected from three 21 d old piglets for isolation of adipocytes and stromal vascular (SV) cells and extraction of total RNA. Reverse transcription and real-time PCR were used to quantify mRNA abundance for: leptin, adiponectin, tumor necrosis factor a (TNFa), interleukin 1ß (IL-1ß), IL-6, IL-8, IL-10, IL-15, haptoglobin, vascular endothial growth factor (VEGF), macrophage migration inhibitory factor (MIF) and monocyte chemotactic protein 1 (MCP1). Data were standardized against cyclophilin mRNA abundance. Separation of cells into adipocytes and SV cells demonstrated that genes could be divided into three groups: high adipocyte expression– leptin and adiponectin; expression in both cell populations - IL-15, haptoglobin, VEGF and MIF; high SV expression - MCP1, IL-1ß, IL-6, IL-8, and IL-10. Leptin, adiponectin and IL-15 expression increased from d1 to d 21 of age in both SQ and PR. Haptoglobin, VEGF, MIF and IL-8 expression decreased between d1 and d4 of age in SQ. TNFa expression was unchanged until d21. IL-1ß, IL-6 and IL-10 expression were unchanged with age in SQ; whereas PR IL-1ß and IL-6 mRNA abundance increased with age. These data demonstrate that neonatal development of adipokine expression varies between adipokines, the site of adipose tissue deposition and whether the adipokine is expressed in the adipocyte.