Ontogenic effects of early feeding of sea bass (Dicentrarchus labrax) larvae with a range of dietary n-3 highly unsaturated fatty acid levels on the functioning of polyunsaturated fatty acid desaturation pathways

Abstract

Four replicated groups of sea bass (Dicentrarchus labrax) larvae were fed diets containing an extra-high level of highly unsaturated fatty acids (HUFA) (XH; 3·7 % EPA þ DHA), a high level of HUFA (HH; 1·7 %), a low level of HUFA (LH; 0·7 %) or an extra-low level of HUFA (XLH; 0·5 %) from day 6 to day 45 (experiment 1; XH1, HH1, LH1, XLH1). After a subsequent 1-month period feeding a commercial diet (2·7 % EPA þ DHA), the capacity of the four initial groups to adapt to an n-3 HUFA-restricted diet (0·3 % EPA þ DHA; R-groups: XH2 R , HH2 R , LH2 R , XLH2 R ) was tested for 35 d. Larval dietary treatments had no effect on larval and juvenile survival rates. The wet weight of day 45 larvae was higher in XH1 and HH1 (P,0·001), but the R-juvenile mass gains were similar in all treatments. D-6-desaturase (D6D) mRNA level was higher in LH1 and XLH1 at day 45 (P,0·001), and higher in LH2 R and XLH2 R , with a significant increase at day 118.Concomitantly, PPARa and PPARb mRNA levels were higher in XLH1 at day 45, and PPARb and g mRNA levels were higher in XLH2 R at day 118, suggesting possible involvement of PPAR in stimulation of D6D expression, when drastic dietary larval conditioning occurred. The low DHA content in the polar lipids (PL) of LH1 and XLH1 revealed an n-3-HUFA deficiency in these groups. Larval conditioning did not affect DHA content in the PL of R-juveniles. The present study showed (i) a persistent D6D mRNA enhancement in juveniles pre-conditioned with an n-3 HUFA-deficient larval diet, over the 1-month intermediate period, and (ii) brought new findings suggesting the involvement of PPAR in the D6D mRNA level stimulation. However, such nutritional conditioning had no significant effect on juvenile growth and lipid composition.

High or low dietary carbohydrate:protein ratios during first-feeding affect glucose metabolism and intestinal microbiota in juvenile rainbow trout

“…Possible biological mechanisms for 'imprinting' the nutritional event until adulthood in mammalian vertebrates comprise adaptive changes in gene expression pattern or cellular phenotype (epigenetic phenomenon), nutrient-sensitive signalling pathways and adaptive clonal selection, which may be transmitted to future offspring (Lucas, 1998;Symonds et al, 2009;Waterland and Jirtle, 2003;Gut and Verdin, 2013). Experimental data on the concept of nutritional programming in fish are limited and some first knowledge stems from recent studies dealing with the possibility of altering the functioning of long-chain fatty acid desaturation in European seabass (Dicentrarchus labrax) (Vagner et al, 2007;Vagner et al, 2009), the use of dietary carbohydrates in rainbow trout [Oncorhynchus mykiss (Walbaum 1792)] (Geurden et al, 2007) or zebrafish (Danio rerio) (Fang et al, 2014;Rocha et al, 2014) and the acceptance and use of plant-based feed in rainbow trout . Taken together, the results all showed particular long-term effects on molecular markers or on growth, because of the acute early-life exposure to the imposed nutritional stimulus.…”

“…In fish, a nutritional stimulus during stages of high metabolic plasticity, such as embryogenesis or early larval development, can be applied at the egg stage [e.g. egg glucose injection (Rocha et al, 2014) or maternal nutrient transfer (Fernández-Palacios et al, 1995;Fernández-Palacios et al, 1997)] or at the onset of exogenous feeding (Geurden et al, 2007;Vagner et al, 2007;Vagner et al, 2009;Fang et al, 2014). Indeed, a previous study in trout by Geurden et al (Geurden et al, 2007) has shown that a hyperglucidic stimulus at the onset of feeding had a permanent effect on carbohydrate digestive enzymes at the juvenile stage, indicating a positive long-term physiological change induced by the first-feeding stimulus in rainbow trout.…”

Novel methodologies in marine fish larval nutrition

“…Moreover, when a given nutrient is tested, it is possible to study the presence of the enzymes responsible for its degradation and in this way a more adequate diet formulation adapted to each developmental stage may be produced. Examples of metabolic enzymatic modulation in response to diet changes are the studies of Seiliez et al (2003), Izquierdo et al (2008) and Vagner et al (2009), reporting adaptations of delta 6 desaturase gene expression to dietary FA composition changes in marine larvae (see Fig. 3) and identifying some factors involved in this regulatory mechanism (Vagner et al 2009).…”

“…Examples of metabolic enzymatic modulation in response to diet changes are the studies of Seiliez et al (2003), Izquierdo et al (2008) and Vagner et al (2009), reporting adaptations of delta 6 desaturase gene expression to dietary FA composition changes in marine larvae (see Fig. 3) and identifying some factors involved in this regulatory mechanism (Vagner et al 2009). Further, changes in digestive enzyme expression when the diet shifts from carnivore to herbivore were recently shown for thicklip grey mullet (Chelon labrosus) larvae (Zouiten et al 2008), suggesting that digestive enzyme activity is genetically programmed to match the developmental alterations in the diet.…”

Reproduction, olfaction and dominance behaviour in Senegalese sole (Solea senegalensis)

“…Moreover, pparβ is a target gene for fatty acids and vitamin A. The expression of pparβ is influenced by nutrition in fish such as gilthead seabream (Fernandez et al, 2011) and sea bass (Vagner et al, 2009) acting as regulators of lipid and lipoprotein metabolism and associated with feeding behaviour. The second gene associated with nutrition analysed in this study was Insuline-like growth factor I (igf-I), which shows a central role in postnatal growth in mammals (Baxter, 1994).…”