Submitted to: Adipocytes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2007
Publication Date: 7/1/2007
Citation: Ramsay, T.G., Mitchell, A.D., Richards, M.P. 2007. Comparison of gene expression in lean contemporary and crossbred obese swine. Adipocytes 2(3/4):133-142. Interpretive Summary: Identification of markers associated with excess fat accumulation in swine would prove beneficial to the swine industry as it attempts to improve quality by producing leaner meat animals. This study was designed to identify genes associated with metabolism, endocrinology and immunology which may contribute to excess fat accumulation in a population of animals that have been crossbred for 15 generations between lean and obese genotypes. Gene expression was measured using the tools of molecular biology. A total of 11 genes were examined, with their selection based upon their association with obesity in humans. The data from this study demonstrated that 3 candidate genes were detected that contribute to differences in the appearances of the lean and obese animals and their meat. These genes included acetyl CoA carboxylase, leptin receptor and interleukin 6. The first gene, acetyl CoA carboxylase is a key regulatory gene for making fat. The leptin receptor binds a hormone that can alter fat metabolism. Interleukin 6 is a component of the immune system that plays an important role in animal health, but can also affect the partitioning of energy between muscle and fat. The combination of the changes in the expression of these three genes significantly contributes to the difference in fat and muscle accumulation between lean and obese swine.
Technical Abstract: The present study was designed to identify genes associated with metabolism, paracrine secretion and cytokine biology which may contribute to retention of characteristics of the obese Meishan phenotype following generations of crossbreeding. The study was conducted with six commercial lean pigs and six ½ Meishan x ½ Large White (MxW) pigs. The MxW pigs have been maintained for 15 generations. Pigs were fed ad libitum a corn-soy based diet containing 18% crude protein, 1.1% lysine for 28 days. Then, carcass measurements were taken and tissue samples were collected: outer and middle subcutaneous adipose tissue, leaf fat, belly fat, liver, and longissimus. Gene expression was quantified by real-time PCR. The mRNA abundance was quantified for malic enzyme, fatty acid synthase, acetyl CoA carboxylase (CBX), lipoprotein lipase, leptin, long form leptin receptor (LepR), insulin-like growth factor I, resistin, interleukin 6 (IL-6), and interleukin 15. Analysis of gene expression across four sites of adipose tissue deposition demonstrated that CBX, LepR and IL-6 were associated with maintenance of the obese phenotype. CBX mRNA abundance was higher in adipose tissues of the MxH (P < 0.05). Both LepR and IL-6 mRNA abundance were lower in adipose tissues of MxH than lean pigs (P <0.05). The present study indicates that CBX, LepR and IL-6 contributes to differences between the MxW and lean lines of pigs at market weight.