Hormonal and nutritional regulation of muscle growth and development in gilthead sea bream (Sparus aurata) = Regulación endocrina y nutricional del crecimiento y desarrollo muscular en dorada (Sparus aurata)
[eng] In the Mediterranean region the increasing of competitiveness of the aquaculture industry is of great interest, especially in the case of gilthead sea bream. With the ultimate purpose of optimizing the aquaculture production of this species, the overall goal of the present thesis is to increas...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2018 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/123193 |
| Acceso en línea: | https://hdl.handle.net/2445/123193 http://hdl.handle.net/10803/586044 |
| Access Level: | acceso abierto |
| Palabra clave: | Orada Factors de creixement Metabolisme Sparus aurata Growth factors Metabolism |
| Sumario: | [eng] In the Mediterranean region the increasing of competitiveness of the aquaculture industry is of great interest, especially in the case of gilthead sea bream. With the ultimate purpose of optimizing the aquaculture production of this species, the overall goal of the present thesis is to increase the knowledge on the regulation of somatic growth, muscle development and flesh quality. This work includes in vitro approaches to investigate the nutritional (i.e., amino acids, AA) and endocrine (i.e., growth factors) regulation of myogenesis, the role in this process of the main endogenous proteolytic systems, as well as of β2-agonists. On the other hand, by means of in vivo studies, the role of GH/IGF axis’ molecules mediating the positive effects of sustained and moderate swimming in growth, as well as the muscular adaptation to exercise in fingerlings of gilthead sea bream was evaluated. In addition, the effects of a sustained-release formulation of recombinant bovine GH (rBGH) on somatic growth, GH/IGF axis and muscle histology was also analyzed. Regarding the first block of studies, the obtained results revealed the important role of endocrine and nutritional factors, and their crosstalk, controlling in vitro myogenesis. Moreover, the nutritional regulation of protein synthesis through TOR signaling pathway was also demonstrated. Besides, the results have shown that the gene expression of calpains is in general higher at the early proliferative stages, whereas cathepsins and the ubiquitin-proteasome (UbP) molecules are more important at the early differentiation phase of in vitro myogenesis. Nevertheless, calpains and UbP members compared to cathepsins are differentially regulated in response to AA availability, supporting the relevance of nutritional factors in muscle development. The in vitro studies also demonstrated that β2-adrenoceptor agonists, mainly salmeterol, can activate both the PKA and PI3K/AKT/TOR signaling pathways. This activation produces an increase in cell proliferation and lipolysis in gilthead sea bream myocytes, therefore, β2-agonists should be considered an effective strategy to stimulate muscle growth by hyperplasia while reducing fat content, thus, to improve flesh quality in fish. Regarding in vivo studies, both the exercise and the rBGH treatment appeared as different useful strategies to stimulate the GH/IGF axis and to enhance muscle growth. Further, the excess of rBGH revealed the existence of systemic and local regulatory mechanisms in this endocrine system to achieve an accurate control of somatic growth. In addition, the obtained results demonstrated that an increased ratio of IGF-I/GH in plasma is an excellent indicator of growth capacity in this species. Also, a combination of enhanced expression of hepatic igf-1 with muscular GH receptor, ghr-1 has appeared as another molecular marker of fish growth potential. Further, the results demonstrated that growth induced by rBGH is a process that combines muscle hypertrophy and hyperplasia, as well as bone development, to maintain the adequate muscle-skeleton balance that will guarantee a quality product with a proper morphology. Additionally, sustained swimming also induced an improvement of muscle quality characteristics, since in response to exercise the protein turnover (cathepsins and UbP) was increased, which in parallel to structural changes and the new vessels formation, are required for hyperplastic growth and enhanced textural parameters. Overall, the works within this thesis demonstrate that it is possible to improve somatic growth and flesh quality in gilthead sea bream, being the moderate and sustained swimming and the adequate balance of nutrients (e.g., AA) in the diet, besides other potential muscle growth stimulators (such as salmeterol), very promising strategies to boost aquaculture production. |
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