Dietary Lecithin Source Affects Growth Potential and Gene Expression in Sparus aurata Larvae

Abstract

Soybean lecithin (SBL), used as a phospholipid source in larval fish diets, may compromise growth and survival in marine species, and affect gene expression, due to differences in fatty acid composition relative to marine lecithins (ML). The potential of SBL as a phospholipid source in gilthead seabream microdiets as compared to ML was evaluated. Two stocking densities were tested in order to exacerbate possible dietary effects: 5 and 20 larvae L(-1). Larvae reflected dietary fatty acid profiles: linoleic acid was higher, whereas eicosapentaenoic and arachidonic acids were lower in SBL fed groups than in ML fed larvae. Highest stocking density decreased survival, and led to elevated saturates and lower docosahexaenoic acid levels in polar lipid. Muscle histology observations showed hindered growth potential in SBL fed larvae. Despite similar cortisol levels between treatments, higher glucocorticoid receptor (GR), as well as hormone-sensitive lipase (HSL) mRNA levels in SBL fed groups revealed a role for fatty acids in gene regulation. Further analysed genes suggested these effects were independent from the hypothalamus-pituitary-interrenal axis control and the endocannabinoid system. Cyclooxygenase-2 and gluconeogenesis seemed unaffected. For the first time in fish, a link between dietary lecithin nature and HSL gene transcription, perhaps regulated through GR fatty acid-induced activation, is suggested. Enhanced lipolytic activity could partly explain lower growth in marine fish larvae when dietary ML is not provided.

Teleost fish larvae adapt to dietary arachidonic acid supply through modulation of the expression of lipid metabolism and stress response genes

“…Relatively low survival was registered between 16 and 34 DAH, which may well relate to the stress of weaning (performed at an early life stage) combined with the fairly small tank volumes used in the rearing system. Still, the survivals observed are within the normal range for the species, despite higher values which have been reported when microdiets were offered at a later stage (43,55) . Relative growth rates may have reflected the same type of constraints, as higher values have been reported for sea-bream larvae fed caseinbased microencapsulated diets (56) .…”

“…Whole-body cortisol was determined in pooled larvae samples of about 150–300 mg per tank (wet weight), according to methodology which has been described previously ( 43 ) , and using a commercial cortisol ELISA kit (Neogen Corporation).…”

“…In fish, the existence of non-genomic pathways involving membrane-bound proteins is still unclear ( 41 , 42 ) . A study in sea-bream larvae showed that GR mRNA abundance could be affected by dietary lecithin source ( 43 ) . Also, in vitro studies in fish ( 44 ) and mammals ( 45 , 46 ) have shown dose-dependent suppression of GR binding by unsaturated fatty acids, a mechanism possibly mediated in vivo by fatty acid binding proteins ( 47 ) .…”

Dietary soybean lecithin affects growth performance, fillet biochemical composition and digestive enzyme activity inSparidentex hastajuvenile

“…Lipid classes (mg g −1 extracted lipid) of fillet of S. hasta juvenile fed experimental diets differing in their content in soybean lecithin (SBL) (mean ± SEM, n = 3). significantly increased with increasing dietary SBL levels, as it has also been reported in other fish species fed diets supplemented with SBL (Benedito-Palos et al 2008;Alves Martins et al 2010;Sotoudeh et al 2011;Azarm et al 2013;Saleh et al 2015;Salini et al 2016). Fish oil is the main source of the LC-PUFA, including arachidonic (20:4n-6, ARA), eicosapentaenoic (20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) (Glencross 2009; Turchini et al 2009 Salini et al 2016).…”

Fish larval nutrition and feed formulation: knowledge gaps and bottlenecks for advances in larval rearing

“…2003b) and gilthead seabream (Seiliez et al. 2006; Martins et al. 2010) fed on tailored designed microdiets have shown that the level and source of phospholipids differing in its fatty acid composition affect the body composition in lipid classes and growth potential.…”