Molecular details on gilthead sea bream (Sparus aurata) sensitivity to low water temperatures from 1H NMR metabolomics.

Biometric and metabolic responses of gilthead sea bream to cold challenge are described following a growth trial divided into three water temperature steps, namely cooling, cold maintenance and recovery. Experimental data provide a useful description of fish response to thermal stress at both zootechnical and molecular level. Although no mortality has been observed, Nuclear Magnetic Resonance-based metabolomics confirms the marked sensitivity of this fish species to low water temperature, and explains some key molecular events associated to fish response to cold. Increase in hepatosomatic index is associated to liver fat accumulation, as a consequence of lipid mobilization from muscle and other extrahepatic tissues, and metabolic rearrangements linked to homeoviscous adaptation of cellular membranes are observed. Following primary responses to descending temperature from 18°C to 11°C, the energetic metabolism (insulin signaling, glycolysis) is first clearly affected; then, at constant low water temperature (11°C), the most perturbed metabolic pathways are related to methionine cycle in liver, while osmoregulatory function is exerted by TMAO in muscle. Water temperature recovery from 11°C to 18°C stimulates gluconeogenesis and glycogen synthesis activities at hepatic level, although the rate of a thermo-compensatory response seems to be slower than that of the cooling phase. The obtained results are intended to guide novel high-performance feed formulations for gilthead sea bream reared during winter.

Impact of three commercial feed formulations on farmed gilthead sea bream (Sparus aurata, L.) metabolism as inferred from liver and blood serum proteomics.

BACKGROUND: The zootechnical performance of three different commercial feeds and their impact on liver and serum proteins of gilthead sea bream (Sparus aurata, L.) were assessed in a 12 week feeding trial. The three feeds, named A, B, and C, were subjected to lipid and protein characterization by gas chromatography (GC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. RESULTS: Feed B was higher in fish-derived lipids and proteins, while feeds C and A were higher in vegetable components, although the largest proportion of feed C proteins was represented by pig hemoglobin. According to biometric measurements, the feeds had significantly different impacts on fish growth, producing a higher average weight gain and a lower liver somatic index in feed B over feeds A and C, respectively. 2D DIGE/MS analysis of liver tissue and Ingenuity pathways analysis (IPA) highlighted differential changes in proteins involved in key metabolic pathways of liver, spanning carbohydrate, lipid, protein, and oxidative metabolism. In addition, serum proteomics revealed interesting changes in apolipoproteins, transferrin, warm temperature acclimation-related 65 kDa protein (Wap65), fibrinogen, F-type lectin, and alpha-1-antitrypsin. CONCLUSIONS: This study highlights the contribution of proteomics for understanding and improving the metabolic compatibility of feeds for marine aquaculture, and opens new perspectives for its monitoring with serological tests.

Multidisciplinary analytical investigation of phospholipids and triglycerides in offshore farmed gilthead sea bream (Sparus aurata) fed commercial diets.

In this work, a quantitative characterisation of lipid (both triglycerides and phospholipids) rearrangements in the muscle of offshore-raised gilthead sea bream was carried out as a function of fish growth between April and September. Relative percentages of lipid classes and fatty acids/acyls composition of the commercial feeds and fish dorsal muscles were assessed by means of an interdisciplinary analytical approach. A combination of preparative chemistry and experimental results from NMR spectroscopy, GC, 3D-TLC as well as proximate analysis permitted the observed growth parameters in key metabolic events to be linked with fish fattening and lipid turnover. While defined effects of feed composition on fatty acid profiles of fillets were ascertained, the relative increase of fatty acyls in triglycerides and phospholipids were also estimated enabling detailed evaluation of TAG:PL ratio in adult offshore-farmed gilthead sea bream. NMR was also used to quantify PUFA regiospecific distribution in TAG and PL.

Effect of modified atmosphere packaging on Quality Index Method (QIM) scores of farmed gilthead seabream (Sparus aurata L.) at low and abused temperatures.

A Quality Index Method (QIM) scheme was developed for modified atmosphere packaging (MAP) packed gilthead seabream, and the effect of MAP gas mixtures (60% CO2 and 40% N2; 60% CO2, 30% O2, and 10% N2), temperature (2, 4, and 8 °C), and time of storage on QI scores was assessed. QI scores were crossed with sensory evaluation of cooked fish according to a modified Torry scheme to establish the rejection point. In order to reduce redundant parameters, a principal component analysis was applied on preliminary QIM parameters scores coming from the best performing MAP among those tested. The final QIM scheme consists of 13 parameters and a maximum demerit score of 25. The maximum storage time was found to be 13 d at 4 °C for MAP 60% CO2 and 40% N2. Storage at 2 °C do not substantially improved sensory parameters scores, while storage under temperature abuse (8 °C) accelerated drastically the rate of increase of QI scores and reduced the maximum storage time to 6 d.