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Abstract: Fish fillet is a source of dietary protein with a well-balanced amino acid composition that also contains high levels of B-vitamins and high levels of the trace elements selenium and iodide. In the present study, we elucidated whether there was a partitioning of the micro-and macronutrients between the soluble fractions (fish protein hydrolysate, FPH) and the insoluble fractions obtained after the enzymatic hydrolysis of fish-raw materials. The FPHs from cod, salmon and saithe contained high levels of taurine, potassium and B-vitamins. Salmon FPH was particularly rich in niacin and pantothenic acid. All FPHs were low in the amino acid tryptophan. The cod and saithe insoluble peptide fractions contained high levels of the indispensable amino acids including tryptophan and of the trace elements selenium, iron and zinc. Iodide levels were high in both the soluble and insoluble fractions. Potential explanations for the segregation of macro- and micronutrients between the FPHs and their corresponding insoluble peptide fractions are discussed. These differences may have nutritional impact when testing different FPHs or insoluble peptide fractions in biological systems. [Copyright &y& Elsevier]

Farmed Atlantic salmon (Salmo salar L.) were slaughtered at an average weight of 5.5 kg in May 2001 under either traditional CO2 anaesthesia (denoted high stress) or a two-step iso-eugenol anaesthesia (denoted low stress) before being bled to death in chilled seawater. Product quality analyses were performed on fillets after 5 days on ice and on cutlets after 12 months of frozen storage (-25 °C). In ice-stored fillets, no differences in gaping were observed between the two anaesthetic protocols, but instrumental analyses revealed that the flesh of the salmon exposed to CO2 sedation was softer and slightly redder (higher a*-value, 27.1±0.1, S.E. versus 26.4±0.1, p<0.0004) and more yellowish (higher b*-value, 22.6±0.1 versus 22.0±0.1, p<0.0001) than the salmon anaesthetised using iso-eugenol. Analyses of frozen–thawed cutlets confirmed the fresh fillet results in that salmon anaesthetised using iso-eugenol were firmer and paler (RocheSalmoFan™ score, 23.5±0.4 versus 24.4±0.3, p<0.05) than the salmon anaesthetised using CO2. Furthermore, the frozen and thawed cutlets of iso-eugenol-anaesthetised salmon had a higher muscle pH (6.15±0.01 versus 5.98±0.03, p<0.05) and lower liquid loss (5.1±0.3 versus 7.1±0.3, p<0.05). Individual growth rate, final body weight (BW), final body length, condition factor (CF), sex, gonadosomatic index (GI) were also registered. No significant correlations (p>0.15) between these growth and body conformation variables and gaping or fillet softness were detected.In conclusion, no differences were observed in fillet gaping between the two anaesthetic protocols, but the salmon anaesthetised using iso-eugenol were firmer, paler and had a higher water-holding capacity than salmon exposed to CO2 anaesthesia. [Copyright &y& Elsevier]

A radioactive soluble model protein for studies of protein digestion, absorption and amino acid (AA) metabolism in larval fish was successfully produced in Atlantic salmon by oral administration of uniformly [U]-14C-labelled amino acids followed by blood sample withdrawal (48 h post-administration) and purification. The salmon serum protein (14C-SSP) was characterised in terms of the protein composition and specific activity of its amino acids. Most radioactivity was found in the three most abundant serum proteins, which had apparent molecular weights of 65, 75 and 120 kDa, respectively, of which labelling was found in all the amino acid residues of the SSP that were analysed. The digestibility of the 14C-SSP was tested by in vivo tube feeding using early stages of Atlantic halibut and was found to be more efficiently digested and utilised than the 14C-methylated bovine serum albumin (14C-BSA) that has been used in previous studies. This supports the notion that proteins labelled by 14C-methylation are not suitable as model proteins in metabolic studies due to modification of their 14C-methylated lysine residues. Further studies on the 14C-SSP demonstrated a digestibility of 59±13% in juvenile halibut, while at the pre-metamorphic stage, it was only 25±13%. This supports the hypothesis that there is a significant improvement in the ability to digest and utilise dietary proteins as the digestive system becomes fully developed, including a functional (acid-producing) stomach. [Copyright &y& Elsevier]

There is growing evidence that soy protein improves the blood lipid profiles of animals and humans. We compared the effects of fish protein hydrolysate (FPH), soy protein, and casein (control) on lipid metabolism in Wistar rats and genetically obese Zucker (fa/fa) rats. In Zucker rats, FPH treatment affected the fatty acid composition in liver, plasma, and triacylglycerol-rich lipoproteins. The mRNA levels of Delta 5 and Delta 6 desaturases were reduced by FPH and soy protein feeding compared with casein feeding. In Zucker rats both FPH and soy protein treatment reduced the plasma cholesterol level. Furthermore, the HDL cholesterol:total cholesterol ratio was greater in these rats and in the Wistar rats fed FPH and soy protein compared with those fed casein. Although fecal total bile acids were greater in soy protein-fed Zucker rats than in casein-fed controls, those fed FPH did not differ from the controls. However, the acyl-CoA:cholesterol acyltransferase activity was reduced in Zucker rats fed FPH and tended to be lower (P = 0.13) in those fed soy protein compared with those fed casein. Low ratios of methionine to glycine and lysine to arginine in the FPH and soy protein diets, compared with the casein diet, may be involved in lowering the plasma cholesterol concentration. Our results indicate that the effects of FPH and soy protein on fatty acid metabolism are similar in many respects, but the hypocholesterolemic effects of FPH and soy protein appear to be due to different mechanisms. FPH may have a role as a cardioprotective nutrient. [ABSTRACT FROM AUTHOR]

The changes in total fat content, fatty acid composition, tocopherol, ascorbic acid, pH and oxidation were analysed in Atlantic salmon (Salmo salar, L.) in response to either cold smoking (20 or 30 °C) or electrostatic smoking. Both fresh and frozen fillets were dry-salted before smoking. The fish smoked were the lean ocean-ranched salmon caught off Iceland in June 1998 and farmed Norwegian salmon, slaughtered in either November 1998 or April 1999, differing in fresh fillet fat content from 84 to 169 g·kg−1 wet weight. The fresh material used in smoking significantly affected the smoking loss of nutritive components in the fillets. The leaner the fish the higher percentile loss in fillet fat. Ascorbic acid decreased about 80 percent from the fresh value, independent of smoking temperature (20 or 30 °C). The fish that were dry-salted and electrostatically smoked only lost about 10 percent of the fresh ascorbic acid content, independent of the type of raw material used, indicating a conserving effect on ascorbic acid by the electrostatic process. Also, the electrostatically smoked fish showed a smaller drop in fillet pH than cold-smoked fillets, while tocopherol was little affected by the smoking methods tested. [Copyright &y& Elsevier]

Abstract: Cobia (Rachycentron canadum, Actinopterygii, Perciformes;10.5±0.1g) were fed to satiation with three plant-based protein test diets with different lysine (L) to arginine (A) ratios (LL/A, 0.8; BL/A, 1.1; and HL/A, 1.8), using a commercial diet as control for six weeks. The test diets contained 730gkg−1 plant ingredients with 505–529g protein, 90.2–93.9g lipidkg−1 dry matter; control diet contained 550g protein and 95g lipidkg−1 dry matter. Periprandial expression of brain NPY and CCK (npy and cck) was measured twice (weeks 1 and 6). At week one, npy levels were higher in pre-feeding than postfeeding cobia for all diets, except LL/A. At week six, npy levels in pre-feeding were higher than in postfeeding cobia for all diets. cck in pre-feeding cobia did not differ from that in postfeeding for all diets, at either time point. Cobia fed LL/A had lower feed intake (FI) than cobia fed BL/A and control diet, but no clear correlations between dietary L/A ratio and FI, growth and expression of npy and cck were detected. The data suggest that NPY serves as an orexigenic factor, but further studies are necessary to describe links between dietary L/A and regulation of appetite and FI in cobia. [Copyright &y& Elsevier]

An amount of 200 kg fresh salmon frames were enzymic hydrolysed with the commercial protease mixture Protamex™, which is known to produce non-bitter hydrolysates. After the enzymic procedure the frames were separated by centrifugation into five fractions: an aqueous fraction rich in peptides, an insoluble fraction, an emulsion fraction, salmon oil and a bone fraction. Approximately 48% of total crude protein present in the salmon frames were found in the aqueous fraction, in which the lipid content was reduced to <0.1% in dry samples after ultramembrane filtration (UF fraction). The UF fraction was low in tryptophan, leucine and phenylalanine+tyrosine, but high in taurine. Nearly 19% of total crude protein present in the salmon frames were found in the insoluble fraction. This fraction was high in most of the indispensable amino acids. Approximately 77% of total lipids present in the salmon frames were isolated as salmon oil, which was high in both eicosapentaenic acid (EPA) and docosahexaenic acid (DHA). The bone fraction contained 62% of total ash present in the salmon frames and was high in the minerals Ca, P and Mg and also in the trace elements Cu, Fe, I, Mn, Se and Zn. All of the produced fractions were low in the undesirable substances As, Cd, Hg and Pb. For future studies the UF fraction and salmon oil might be interesting as health promoting agents, the insoluble fraction as dietary protein supplement and the bone fraction as dietary mineral supplement. [Copyright &y& Elsevier]

Abstract The effects of low marine ingredient diets supplemented with graded levels (L1, L2, L3) of a micronutrient package (NP) on growth and metabolic responses were studied in diploid and triploid salmon parr. Diploids fed L2 showed significantly improved growth and reduced liver, hepatic steatosis, and viscerosomatic indices, while fish fed L3 showed suppressed growth rate 14 weeks post feeding. In contrast, dietary NP level had no effect on triploid performance. Whole body mineral composition, with exception of copper, did not differ between diet or ploidy. Whole fish total AAs and N-metabolites showed no variation by diet or ploidy. Free circulating AAs and white muscle N-metabolites were higher in triploids than diploids, while branch-chained amino acids were higher in diploids than triploids. Diploids had higher whole body α-tocopherol and hepatic vitamins K 1 and K 2 than triploids. Increased tissue B-vitamins for niacin and whole-body folate with dietary NP supplementation were observed in diploids but not triploids, while whole body riboflavin was higher in diploids than triploids. Hepatic transcriptome profiles showed that diploids fed diet L2 was more similar to that observed in triploids fed diet L3. In particular, sterol biosynthesis pathways were down-regulated, whereas cytochrome P450 metabolism was up-regulated. One‑carbon metabolism was also affected by increasing levels of supplementation in both ploidies. Collectively, results suggested that, for optimised growth and liver function, micronutrient levels be supplemented above current National Research Council (2011) recommendations for Atlantic salmon when fed low marine ingredient diets. The study also suggested differences in nutritional requirements between ploidy. Highlights • Plant based diets can support optimal growth in diploid salmon parr when micronutrient inclusion levels are increased • Different micronutrient supplementation affected lipid metabolism, cytochrome P450 genes and one-carbon metabolism • Dietary micronutrient requirements differ between ploidy • NRC 2011 minimum dietary recommendations for Atlantic salmon need to be revised when utilising low marine ingredient diets [ABSTRACT FROM AUTHOR]

Bile acids (BAs) are powerful regulators of metabolism, and mice treated orally with cholic acid are protected from diet-induced obesity, hepatic lipid accumulation, and increased plasma triacylglycerol (TAG) and glucose levels. Here, we show that plasma BA concentration in rats was elevated by exchanging the dietary protein source from casein to salmon protein hydrolysate (SPH). Importantly, the SPH-treated rats were resistant to diet-induced obesity. SPH-treated rats had reduced fed state plasma glucose and TAG levels and lower TAG in liver. The elevated plasma BA concentration was associated with induction of genes involved in energy metabolism and uncoupling, Dio2, Pgc-1a, and Ucp1, in interscapular brown adipose tissue. Interestingly, the same transcriptional pattern was found in white adipose tissue depots of both abdominal and subcutaneous origin. Accordingly, rats fed SPH-based diet exhibited increased whole body energy expenditure and heat dissipation. In skeletal muscle, expressions of the peroxisome proliferator-activated receptor β/δ target genes (Cpt-1b, Angptl4, Adrp, and Ucp3) were induced. Pharmacological removal of BAs by inclusion of 0.5 weight % cholestyramine to the high fat SPH diet attenuated the reduction in abdominal obesity, the reduction in liver TAG, and the decrease in nonfasted plasma TAG and glucose levels. Induction of Ucp3 gene expression in muscle by SPH treatment was completely abolished by cholestyramine inclusion. Taken together, our data provide evidence that bile acid metabolism can be modulated by diet and that such modulation may prevent/ameliorate the characteristic features of the metabolic syndrome. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the endocrine signalling from dietary plant protein on somatotropic system and gastrointestinal hormone cholecystokinin (CCK), two iso-amino acid diets based on either high plant or high fish meal protein were fed to Atlantic salmon. Salmon with an average starting weight of 641±23 g (N =180), were fed a fish meal (FM) based diet (containing 40% FM) or diets mainly consisting of blended plant proteins (PP) containing only 13% marine protein, of which only 5% was FM for 3 months. mRNA levels of target genes GH, GH-R, IGF-I, IGF-II, IGFBP-1, IGF-IR in addition to CCK-L, were studied in brain, hepatic tissue and fast muscle, and circulating levels of IGF-I in plasma of Atlantic salmon were measured. We detected reduced feed intake resulting in lower growth, weight gain and muscle protein accretion in salmon fed plant protein compared to a diet based on fish meal. There were no significant effects on the regulation of the target genes in brain or in hepatic tissues, but a trend of down-regulation of IGF-I was detected in fast muscle. Lower feed intake, and therefore lower intake of the indispensable amino acids, may have resulted in lower pituitary GH and lower IGF-I mRNA levels in muscle tissues. This, together with higher protein catabolism, may be the main cause of the reduced growth of salmon fed plant protein diet. There were no signalling effects detected either by the minor differences of the diets on mRNA levels of GH, GH-R, IGF-IR, IGF-II, IGFBP-1, CCK or plasma protein IGF-I. [Copyright &y& Elsevier]

In three consecutive experiments, frames without heads from Atlantic salmon were hydrolysed by Protamex™ protease. In experiment I (24 factorial design) nitrogen recoveries (NR) of 44–76% were obtained, after 120 min of hydrolysis, by systematically varying the hydrolysing parameters, starting pH (5.4–7.7), temperature (36–50 °C), E:S ratio (30–90 AU kg−1 crude protein) and frames–water ratio (0.71–1.21) between low and high levels. The highest levels of E:S ratio (90 AU kg−1 crude protein), temperature (50 °C) and starting pH (7.7) and the lowest level of frames–water ratio (0.71) resulted in the highest NR (76%). In experiment II, the optimal temperature and starting pH in the hydrolysis with Protamex™ were established at 50–56 °C and 6.5–7.6, respectively. Beyond these temperature and starting pH intervals, the NR tended to decrease. In experiment III, at optimal temperature (50 °C) and starting pH (6.5) conditions and frames–water ratio of 1.2, NR of 43–61% were achieved after 60 min of hydrolysis, by varying the E:S ratios from 10–90 AU kg−1 crude protein. The highest E:S ratio resulted in the highest NR but running the hydrolysis for a period longer than 60 min resulted in little increase in NR. [Copyright &y& Elsevier]

The Atlantic salmon aquaculture industry relies on adjustments of female broodstock spawning season to meet the demand for delivery of embryos outside the natural spawning season. Earlier results from zebrafish have shown that parental micronutrient status program offspring metabolism. Therefore, the main hypothesis of this study was to investigate if out-of-season (off-season) broodstock (spawning in June, in land-based recirculation systems) and their offspring deviate in micronutrient status when compared to broodstock and offspring from normal spawning season. Both seasons of female Atlantic salmon broodstock were fed the same diet and starved for approximately the same time interval prior to spawning. We compared nutrients related to the 1C metabolism (vitamin B12, folate, vitamin B6, methionine), free amino acids (FAAs) and lipid classes in broodstock muscle and liver tissues, and during offspring ontogeny. In general, the off-season broodstock showed higher levels of folate, vitamin B6 and selected FAAs in muscle tissue, and higher levels of folate and lipids (cholesterol and sphingomyelin) in liver tissue compared to normal-season. Furthermore, embryos from off-season had reduced amounts of all the measured lipid classes, like cholesterol and sphingomyelin, and lower levels of one type of folate and changes in FAAs and N-metabolites. We discovered significant differences between the seasons in mRNA levels of genes controlling fatty acid synthesis and 1C metabolism in both broodstock liver and offspring. Moreover, for genes controlling the methylation of DNA; both maintenance and de novo DNA methyltransferases (DNMTs) were expressed at higher levels in off-season compared to normal-season offspring. Our results show, in general that normal spawning season broodstock allocated more nutrients to eggs than off-season. Our results indicate a potential for improved maturation for off-season group to obtain a higher offspring growth potential, and this argues for a reassessment of the nutritional influence from broodstock to offspring and the consequences through nutritional programming. Unlabelled Image • Off-season spawning expands the availability period for salmon production. • Off-season broodstock retained higher levels of folate, FAAs and lipids. • Off-season embryos received lower levels of folate, vitamin B 12 and lipids. • Epigenetic related genes were expressed at higher levels in off-season larvae. • Off-season offspring growth is modified by nutritional programming. [ABSTRACT FROM AUTHOR]

The aim was to study the effect of resveratrol on the interplay of inflammatory signals using three different cell models; a metabolic organ (liver), an endocrine organ (visceral adipose tissue, VAT) and an immune organ (head kidney leukocytes, HKL) following lipopolysaccharide challenge (LPS). Atlantic salmon HKL, liver cells and VAT were isolated from the same fish (n = 5). Each cell type was cultured either as mono-cultures, as co-cultures between HKL-liver cells, liver cells-VAT and HKL-VAT. Triple -cultures included all three tissues. In all cultures of HKL, LPS induced transcription of IL-1β , cox2 , tnfα , IL-12 , ccattβ and Ahr were significantly inhibited by resveratrol (100, 200 μM). Likewise, in all cultures of liver cells, the LPS induced expression of IL-1β was inhibited by resveratrol (100 and 200 μM). HKL, both mono-cultures and triple-cultures and VAT cocultured with liver cells, showed LPS induced cox2 transcription that was inhibited by resveratrol (100 and 200 μM). In contrast, VAT cultured as triple cultures, resveratrol 200 μM particularly, in the presence of LPS, seemed to increase the expression of IL-1β and ccattβ. Resveratrol did not significantly affect lox5 expression in any culture. HKL and VAT are the main producers of PGE2 in response to inflammatory stimuli. VAT showed high endogenous production of eicosanoids, particularly LTB4 and LTB5. Resveratrol inhibited bot LPS induced and endogenous eicosanoid production. Possible targets of resveratrol, Sirt1 and pAMPK were affected differently in the different cells and tissue studied. • Resveratrol (100, 200 μM) reduced LPS induced transcription of IL-1β , cox2 , tnfα , IL-12 , ccattβ and Ahr in HKL and IL-1β in liver cells, regardless of culturing conditions. • VAT in triple-culture increased IL-1β and ccaatβ transcription when exposed to resveratrol 200 μM and LPS. • HKL and VAT are the main producers of PGE2 in response to inflammatory stimuli and resveratrol reduced this production. [ABSTRACT FROM AUTHOR]