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Lipolysis and lipogenesis related genes regulation in different laying stages of Japanese quail

Yang, Shujin
http://rave.ohiolink.edu/etdc/view?acc_num=osu1332166889

Abstract Details

2012, Master of Science, Ohio State University, Animal Sciences.
Egg yolk is typically made up of lipid, which comprises about 30% of the wet mass and 60% of the dry mass of the yolk. With a continuous increased demand in the egg industry, U.S. egg production is of great economic importance to the poultry industry. As a common source of nutrition, egg is considered to be indispensible in our daily lives. Therefore, understanding egg synthesis would improve egg production industry but also could benefit the consumers. The exact mechanisms of lipid production and transportation into oocyte are not fully understood. Whereas obesity and hormonal related weight control has been well studied in mammals, very few of those studies could be used as reference for poultry due to the significant difference between mammals and poultry. One unique feature about poultry is that, unlike mammals, adipose tissue in birds has a very limited capacity to generate lipid. Therefore the majority of lipid is synthesized by the liver. During the egg laying period, large amounts of lipid have to be produced and transported to the developing oocyte to be deposited into the egg. Adipose tissue, on the other hand, functions as the major storage site for the lipid and could also facilitate the process of laying by releasing more lipid into the system. iii The studies presented here investigate the hypothesis that during the laying period, increased lipid secretion from the maternal liver whereas decreased lipogenesis and increased lipolysis by the adipocyte coordinates with each other to guarantee enough lipid supply to the developing oocyte, by studying genes regulating lipolysis and lipogenesis in both adipocyte and liver among pre-laying, onset of laying and actively laying Japanese quail as well as relating changes in blood parameters and the expression of genes regulating lipolysis and lipogenesis. Three groups of quail were included in this study: 45d no yolk quail (n=6), representing pre-laying quail; 45d with yolk quail (n=6), representing onset of laying quail; and 80d actively laying quail (n=6), representing actively laying quail. It was found that adipose weight to body weight ratio was significantly higher among 45d with yolk quail than 45 d no yolk or 80 d quail (P < 0.01). Liver weight to body weight ratio, on the other hand, reached its peak in 80d quail (P < 0.01). Significant non-esterified fatty acids (NEFA) value increase was observed from 45d no yolk to 80d quail (P < 0.05). In 80 d quail, not only protein expression but also phosphorylation level of adipose triglyceride lipase (ATGL) was higher than 45 d quail. In addition, relative mRNA expression level of comparative gene identification-58 (CGI58), the co-activator of ATGL, was significantly higher (P<0.05) in 80d than 45 d quail. Increased lipolytic activity in adipocyte by increased ATGL activity can further being proved by significantly higher NEFA level in 80d quail as compared to 45d quail. On the other hand, higher G0S2 protein expression at this stage implies the effort made by adipocyte to counter-balance the strongly increased lipolytic activity in adipocyte by ATGL and CGI58. The relative mRNA expression of FATP1 in 80d quail was significantly lower than those of 45d quail (P < 0.05). Reverse quantitative PCR was performed to evaluate the expression of genes controlling lipogenesis and lipolysis in both liver and adipocyte. For genes controlling lipogenesis in liver, both fatty acid synthase (FAS) (P < 0.01) and lipoprotein lipase (LPL) (P < 0.005) were down-regulated from 45d to 80d quail whereas apoVLDL II, the laying specific gene, upregulated (P < 0.05) from 45d no yolk quail to both 45d with yolk and 80d quail. In conclusion, adipocyte actively uptakes fatty acid and converts them into TAG in pre-laying quail. For the purpose of securing enough lipid supply to the developing oocyte, the liver actively synthesizes TAG, either for storage purposes or for VLDL assembly purpose until enough lipid is accumulated in the liver and egg yolk production is initiated. Afterwards, the liver reduced its FA synthesis and uptaking, but actively packaged laying specific VLDL to transport lipid into circulation. Adipocyte actively secrets free fatty acids into circulation, perhaps to be taken up by other tissues or even sent directly to the oocyte.
Kichoon Lee, PhD (Committee Chair)
Michael Day, PhD (Committee Member)
Macdonald Wick, PhD (Committee Member)

Recommended Citations

Citations

  • Yang, S. (2012). Lipolysis and lipogenesis related genes regulation in different laying stages of Japanese quail [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332166889

    APA Style (7th edition)

  • Yang, Shujin. Lipolysis and lipogenesis related genes regulation in different laying stages of Japanese quail. 2012. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1332166889.

    MLA Style (8th edition)

  • Yang, Shujin. "Lipolysis and lipogenesis related genes regulation in different laying stages of Japanese quail." Master's thesis, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332166889

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.