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Title: Alteration in gene expression in Nile tilapia (Oreochromis niloticus) juveniles submitted to fasting and refeeding.

Author
item NEBO, CAROLINE - Faculdade De Ciências Agrárias E Veterinárias De Jaboticabal-Unesp
item Overturf, Kenneth - Ken
item BREZAS, ANDREAS - University Of Idaho
item DAL-PAI-SILVA, MAELI - Faculdade De Ciências Agrárias E Veterinárias De Jaboticabal-Unesp
item PORTELLA, MARIC CELIA - Faculdade De Ciências Agrárias E Veterinárias De Jaboticabal-Unesp

Submitted to: International Aquaculture Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/5/2014
Publication Date: 11/5/2014
Citation: Nebo, C., Overturf, K.E., Brezas, A., Dal-Pai-Silva, M., Portella, M. 2014. Alteration in gene expression in Nile tilapia (Oreochromis niloticus) juveniles submitted to fasting and refeeding. International Aquaculture Meeting. 9th International Aquaculture forum Book of Abstracts; pg 59.

Interpretive Summary:

Technical Abstract: One of the most important biological processes in living organisms that are affected by environmental fluctuations is growth, and the skeletal muscle growth in fish is dependent on proliferation and differentiation of myogenic precursor cells that are activated by Myogenic Regulatory Factors or inhibited by myostatin or other genes regulating protein turnover in muscle. The goal of this study was to investigate changes in the gene expression of factors related to growth and muscle atrophy in Nile tilapia juveniles (chitralada Thai strain) during periods of fasting and refeeding. Juveniles (body weight 26.37 ± 3.77g) were randomly stocked into 32 of 150-L tanks with continuously flowing water and constant aeration. Four treatments and eight replicates were established: FC (control treatment fed daily), F1 (one week of fasting and ten weeks of refeeding), F2 (two weeks of fasting and ten weeks of refeeding), and F3 (three weeks of fasting and ten weeks of refeeding). Fish were fed to apparent satiation with commercial diet (32% crude protein), three times a day (9AM, 2PM and 5PM). At the beginning of the experiment and during periods of fasting (1, 2 and 3 weeks) and after 10 weeks of refeeding, fish were weighed, measured and muscle samples (n=8 fish per treatment) were taken for analysis by real time quantitative RT-PCR. The data were analyzed by the software Statistical Analysis System (SAS 9.1). The means that showed significant differences between treatments were compared by Tukey test, at 5% of significance. Body mass and total lengths in FC were higher than for F1, F2 and F3, after fasting and refeeding times. The fasting condition promoted a decrease in IGF-1 gene expression, but increased expression in genes related to muscle atrophy (MuRF1 and Atrogin-1) in F1, F2 and F3 treatments (Figure 1). However, the myostatin levels did not differ during fasting and refeeding period. The levels of Myogenic Regulatory Factors (MyoD and Myogenin) were equal after the refeeding period, and only myogenin in F3, during 3 weeks of fasting was higher in relation to FC. IGF1-receptor mRNA expression was higher during fasting in F1, F2 and F3; nonetheless, after 10 weeks of refeeding only F3 was lower in relation to control treatment FC. Our results showed that atrophy genes (MuRF1 and Atrogin-1) inhibited muscle growth during 1, 2 and 3 weeks of fasting but 10 weeks of refeeding was shown to be sufficient to equalize the gene expression found in the control treatment FC. Therefore, indicating equilibrium in growth rate between the groups.