Abstract
The principle aim of this study is to elucidate the relationship between the fatty acid desaturase 2 gene (fads2) expression pattern in peripheral blood cells (PBCs) and liver of gilthead seabream (GSB), Sparus aurata broodstock in order to determine the possible use of fads2 expression as a potential biomarker for the selection of broodstock. This selection could be utilized for breeding programs aiming to improve reproduction, health, and nutritional status. Passive Integrated Transponder (PIT)-tagged GSB broodstock (Male-1.22 ± 0.20 kg; 44.8 ± 2 cm and female-2.36 ± 0.64 kg; 55.1 cm) were fed a diet containing low levels of fish meal and fish oil (EPA 2.5; DHA 1.7 and n-3 LC-PUFA 4.6% TFA) for one month. After the feeding period, fads2 expression in PBCs and liver of both male and female broodstock were highly significantly correlated (r = 0.89; p < 0.001). Additionally, in male broodstock, liver fads2 expression was significantly correlated (p < 0.05) to liver contents in 16:0 (r = 0.95; p = 0.04) and total saturates (r = 0.97; p = 0.03) as well as to 20:3n–6/20:2n–6 (r = 0.98; p = 0.02) a Fads2 product/precursor ratio. Overall, we found a positive and significant correlation between fads2 expression levels in the PBCs and liver of GSB broodstock. PBCs fads2 expression levels indicate a strong potential for utilization as a non-invasive method to select animals having increased fatty acid bioconversion capability, better able to deal with diets free of fish meal and fish oil.
Highlights
The ability of teleosts to biosynthesize long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA), such as arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3), from 18 carbon PUFA substrate, linoleic acid (LA; 18:2n-6), and α-linolenic acid (ALA; 18:3n-3) is limited [1,2,3]
It is well documented that the biosynthesise of n-3 LC-PUFA is initiated by the delta 6 fatty acid desaturase (∆6 Fads), which acts on ALA or LA to produce EPA and DHA or ARA through several steps of desaturation, elongation, and β-oxidation (Figure 1)
This study aimed to find the relationship between fads2 expression patterns in peripheral blood cells and liver of broodstock gilthead seabream, Sparus aurata, to see the possible use of the fads2 gene as a potential biomarker for the selection of broodstock to undertake breeding programs aiming at improved reproduction, health and nutritional status
Summary
The ability of teleosts to biosynthesize long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA), such as arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3), from 18 carbon PUFA substrate, linoleic acid (LA; 18:2n-6), and α-linolenic acid (ALA; 18:3n-3) is limited [1,2,3]. Freshwater fish and especially fish from lower trophic levels are considered capable of bioconversion of dietary C18 PUFA such as linoleic acid (LA; 18:2n-6) and α-linolenic acid (ALA; 18:3n-3) into LC-PUFA, whereas marine teleosts have limited ability to biosynthesize the LC-PUFA from LA and ALA substrates [1,8,10]. This is imputed to the lower activity of Fads, which is due to the lower expression of the fads gene in marine fish compared to freshwater fish [6,11,12,13]. It is well documented that the biosynthesise of n-3 LC-PUFA is initiated by the delta 6 fatty acid desaturase (∆6 Fads), which acts on ALA or LA to produce EPA and DHA or ARA through several steps of desaturation, elongation, and β-oxidation (Figure 1)
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