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Chen Zhang Master Thesis Final v1.3.pdf (1.5 MB)

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Differential expression of Agouti-related Peptide in Avian Species and the Association of Appetite-related Neuropeptides with Nutrition Status

Zhang, Chen
http://rave.ohiolink.edu/etdc/view?acc_num=osu1367518755

Abstract Details

2013, Master of Science, Ohio State University, Animal Sciences.
In the poultry industry, the level of feed consumption plays an important role in determining the rate of growth and body composition achieved by animals. Especially for economic species, broiler and turkey, properly increasing feed intake and then elevating growth rate as well as body weight are among the critical goals for the benefit of producers. Therefore, the understanding of the regulatory mechanism of feed intake in the food animal species is of great importance, which is helpful in providing potential nutritional methods to overcome the negative environmental effects and to achieve the improvement of related animal production. The metabolism of food intake regulation is highly conserved along the evolution across different species, thus the knowledge gained from this study could also bring insights for the appetite control and the improvement of obesity in human. Agouti-related peptide (AgRP), an orexigenic neuropeptide mainly expressing in the arcuate nucleus, is of great importance in the food intake regulation. It is elevated by states of negative energy balance and is considered as the major indicator of poor nutrition status. Besides AgRP, other hypothalamic neuropeptides including NPY, POMC and CART are sensitive to peripheral nutrition status and regulate feed intake behavior. The studies presented here investigate AgRP in the avian specie, especially focus on the differential expression of alternative transcripts and how nutrition status modulates the amount of appetite-associated neuropeptides in the hypothalamus. Gamma amino-butyric acid (GABA) is a chief inhibitory neurotransmitter in the CNS, whose expression is restricted to the hypothalamus area. It plays a role in regulating neuronal excitability in the arcuate nucleus that is the hypothalamic area in charge of food intake regulation and energy homeostasis. In some feeding studies, GABA is considered as a nutritional supplement in order to overcome negative effects due to heat stress in poultry industry. The presented study aims to understand whether long-term dietary supplementation of GABA in different purity and dosages stimulates feed intake in chickens under normal ambient temperature. This study reported two major transcript isoforms of AgRP in the avian species, also their differential expression patterns in various tissues. These results revealed AgRP-A form to be expressed in all the avian species, while AgRP-B form to be expressed in the chicken and turkey rather than in the quail. The expression patterns of AgRP A- and B form are different from each other in the chicken and turkey, and AgRP-A form is exclusively expressed in the hypothalamus in the quail. Importantly, the results of cloning genomic DNA and cDNA of AgRP in the chicken, turkey and quail as well as our bioinformatics analysis demonstrated that there is a deletion of 521bp in genomic DNA of AgRP-A form in the quail, which results in the absent expression of qAgRP-B form. In order to investigate how the mRNA expressions of neuropeptides change with peripheral nutrition status, fast and re-feeding experiments were applied to 22-day old male quails. The results of real-time PCR on four appetite-related neuropeptides indicate that the amount of AgRP and NPY is increased (P<0.05) in negative energy balance while levels of POMC and CART are decreased (P<0.05) in fast then are elevated (P<0.05) in re-feeding state. Our GABA feeding experiments revealed that long-term dietary supplementations of both bacterial- and pure GABA in different doses fail to stimulate feed intake in chickens in normal ambient temperature. It suggests that GABA effects on promoting feed intake in the chickens in heat stress, which have been reported by other researchers, tend to release stress due to heat stress rather than to directly regulate appetites in chickens. This study, to our knowledge, firstly reported the differential expression of alternative transcript isoforms of AgRP in the chicken, turkey and quail. The absent expression of AgRP-B form in the quail and varied expression pattern of two isoforms in various tissues in the avian species suggest the alternative promoter usages of AgRP A- and B form, which might result in the differed biological functions of them. The knowledge gained from present study is helpful in understanding feed intake regulation metabolism in the avian species, and in providing potential targets for appetite control in human.
Kichoon Lee (Advisor)
Pasha Peffer (Committee Member)
David Latshaw (Committee Member)
Animal Sciences

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Citations

  • Zhang, C. (2013). Differential expression of Agouti-related Peptide in Avian Species and the Association of Appetite-related Neuropeptides with Nutrition Status [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367518755

    APA Style (7th edition)

  • Zhang, Chen. Differential expression of Agouti-related Peptide in Avian Species and the Association of Appetite-related Neuropeptides with Nutrition Status. 2013. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1367518755.

    MLA Style (8th edition)

  • Zhang, Chen. "Differential expression of Agouti-related Peptide in Avian Species and the Association of Appetite-related Neuropeptides with Nutrition Status." Master's thesis, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367518755

    Chicago Manual of Style (17th edition)

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