Nutrition of Atlantic Salmon (Salmo salar): The Requirement and Metabolism of Arginine

Exploring the Biotechnological Value of Marine Invertebrates: A Closer Look at the Biochemical and Antioxidant Properties of Sabella spallanzanii and Microcosmus squamiger

Sabella spallanzanii and Microcosmus squamiger were profiled for proximate composition, minerals, amino acids, fatty acids (FA), carotenoids, radical scavenging activity on the 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical, oxygen radical absorbance capacity (ORAC) and iron and copper chelating properties. Microcosmus squamiger had the highest level of moisture and crude protein, S. spallanzanii was enriched in crude fat and ash. Both species had similar levels of carbohydrates and energy. There was a prevalence of arginine and glycine in S. spallanzanii, and of taurine in M. squamiger. The most abundant minerals in both species were Na, Ca, and K. The methanol extract of S. spallanzanii had metal chelating properties towards copper and iron, while the methanol extract of M. squamiger was able to chelate copper. M. squamiger extracts had similar ORAC values. Fucoxanthinol and fucoxanthin were the major carotenoids in the M. squamiger dichloromethane extract. Saturated FA were more abundant than unsaturated ones in methanol extracts, and unsaturated FA prevailed in the dichloromethane extracts. Palmitic acid was the predominant FA in methanol extracts, whereas eicosapentaenoic (EPA) and dihomo-γ-linolenic acids were the major compounds in dichloromethane extracts. Low n-6/n-3 ratios were obtained. Our results suggests that both species could be explored as sources of bioactive ingredients with multiple applications.

Rainbow trout (Oncorhynchus mykiss) urea cycle and polyamine synthesis gene families show dynamic expression responses to inflammation

The urea cycle is an endogenous source of arginine that also supports removal of nitrogenous waste following protein metabolism. This cycle is considered inefficient in salmonids, where only 10-15% of nitrogenous waste is excreted as urea. In rainbow trout, arginine is an essential amino acid that has attracted attention due to its many functional roles. These roles include the regulation of protein deposition, immune responses and polyamine synthesis; the latter is directly linked to the urea cycle and involved in tissue repair. The key enzymes used in the urea cycle, namely arginase, ornithine transcarbamylase, argininosuccinate synthase and argininosuccinate lyase, in addition to two rate limiting enzymes required for polyamine synthesis (ornithine decarboxylase and s-adenosylmethionine decarboxylase) are poorly studied in fishes, and their responses to inflammation remain unknown. To address this knowledge gap, we characterised these gene families using phylogenetics and comparative genomics, investigated their mRNA distribution among a panel of tissues and established their transcriptional responses to an acute inflammatory response caused by bacterial infection in liver and muscle. Gene duplicates (paralogues) were identified for arginase (ARG1a, 1b, 2a and 2b), ornithine decarboxylase (ODC1 and 2) and s-adenosylmethionine decarboxylase (SAMdc1 and 2), including paralogues retained from an ancestral salmonid-specific whole genome duplication. ARG2a and 2b were highly upregulated following bacterial infection in liver, whereas ARG1b was downregulated, while both paralogues of SAMdc and ODC were upregulated in liver and unchanged in muscle. Overall, these findings improve our understanding of the molecules supporting the urea cycle and polyamine synthesis in fish, highlighting major changes in the regulation of these systems during inflammation.

Effect of N-carbamoylglutamate supplementation on the growth performance, antioxidant status and immune response of mirror carp (Cyprinus carpio) fed an arginine-deficient diet

The present study was conducted to determine the effect of dietary N-carbamoylglutamate (NCG) supplementation on the growth performance, antioxidant capability and immune responses of mirror carp (Cyprinus carpio) fed an arginine (Arg)-deficient diet. A total of 630 mirror carp (41.65 ± 0.14 g) were fed diets (Arg 1.24% of the diet) that were supplemented with 0.50% Arg (control diet) or graded levels of NCG at 0 (Arg deficiency diet), 0.04%, 0.08%, 0.12%, 0.16% and 0.20% for 8 weeks. The results showed that, compared with the control diet, the Arg-deficient diet supplementation with 0 NCG (1) decreased the final body weight (FWB), the weight gain rate (WGR) or the protein efficiency ratio (PER) and increased the feed conversion ratio (FCR); (2) decreased the concentration of Arg and nitric oxide (NO) and the activity of total nitric oxide synthetase (T-NOS) in the plasma; (3) decreased the activities of superoxide dismutase (SOD) in the proximal intestine (PI), catalase (CAT) in the PI and distal intestine (DI), and glutathione peroxidase (GPx) in PI and mid-intestine (MI) and increased the concentration of malondialdehyde (MDA) in the PI, MI and DI; and (4) decreased the activity of lysozyme in the plasma, increased the relative mRNA expression of tumor necrosis factor-α (TNF-α), interleukin1β (IL-1β) and interleukin 8 (IL-8) in the PI, MI and DI, and decreased the relative mRNA expression of interleukin 10 (IL-10) in the PI and MI, and transforming growth factor β2 (TGF-β2) in the PI, MI and DI. Compared with the Arg deficient-diet supplementation with 0 NCG, (1) 0.12% or 0.16% NCG increased the FBW, WGR and PER, and 0.16% NCG increased the FCR; (2) 0.08%-0.20% NCG increased the concentration of Arg, NO and the activity of T-NOS; (3) 0.08% NCG increased the activities of SOD in the PI and MI, and 0.12% NCG increased activities of CAT and GPx in the PI, MI and DI; and (4) 0.04%-0.20% NCG increased the activity of lysozyme, 0.04%-0.20% NCG decreased the relative mRNA expression of TNF-α, IL-1β and IL-8 in the PI and MI, and 0.04%-0.20% NCG increased the relative mRNA expression of IL-10 and TGF-β2 in the PI and MI. The present results indicated that dietary 0.12% or 0.16% NCG improved the growth performance, feed utilization, intestinal antioxidant capacity and immune response of mirror carp fed an Arg-deficient diet.

Effects of dietary arginine levels on growth performance, body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish (Pelteobagrus fulvidraco)

This experiment was conducted to investigate the effects of dietary arginine levels on growth performance, body composition, serum biochemical indices and resistance ability against ammonia-nitrogen stress in juvenile yellow catfish (Pelteobagrus fulvidraco). Five isonitrogenous and isolipidic diets (42% protein and 9% lipid) were formulated to contain graded levels of arginine (2.44%, 2.64%, 2.81%, 3.01% and 3.23% of diet), by supplementing L-Arginine HCl. Seven hundred juvenile yellow catfish with an initial average body weight of 1.13 ± 0.02 g were randomly divided into 5 groups with 4 replicates of 35 fish each and each group was fed one of the diets. After 56 d feeding, fish were exposed to 100 mg/L of ammonia-nitrogen for 72 h. The results showed that weight gain (WG) and specific growth rate (SGR) in 2.64% and 2.81% groups were significantly higher than those in 3.23% group (P < 0.05). The feed conversation ratio (FCR) in 2.64%, 2.81% and 3.01% groups was significantly decreased when compared with 3.23% group. The protein efficiency ratio (PER) in 2.64% group was significantly higher than that in 2.44% and 3.23% groups (P < 0.05). The condition factor (CF) of fish was significantly higher in 2.81% group than that in 2.44% group (P < 0.05). Dietary arginine levels had no significant effect on hepatosomatic index (HSI), viscerosomatic index (VSI), and whole-body dry matter, crude protein, crude lipid, ash contents, as well as serum total protein (TP), triglyceride (TG), glucose (GLU), urea nitrogen (UN) contents and aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities (P > 0.05). After the fish were challenged to ammonia-nitrogen for 72 h, their cumulative mortality rate in 2.81% group was significantly lower than that in 2.44% group (P < 0.05). The results suggested that dietary arginine level at 2.81% could optimize anti-ammonia-nitrogen stress ability of juvenile yellow catfish and a level of 3.23% arginine seemed to depress the growth performance of fish and decreased their tolerance to the ammonia-nitrogen stress under current study. A quadratic regression analysis based on WG indicated that the optimal dietary arginine requirement of juvenile yellow catfish was estimated to be 2.74% of the diet (6.45% of dietary protein) under current culture conditions.

Arginine supplementation and exposure time affects polyamine and glucose metabolism in primary liver cells isolated from Atlantic salmon

Arginine has been demonstrated to enhance glucose and lipid oxidation in mammals through activation of polyamine turnover. We aimed to investigate how arginine affects energy utilization through polyamine metabolism and whether this effect is time dependent. Primary liver cells were isolated from Atlantic salmon (2.2 kg body weight) fed diets containing 25.5 (low arginine, LA) or 36.1 (high arginine, HA) g arginine/kg dry matter for 12 weeks, to investigate the effect of long-term arginine supplementation. The cells were cultured for 24 h in L-15 medium to which either alpha-difluoromethylornithine (DFMO) or N (1),N (11)-diethylnorspermine (DENSPM) was added. Analysis of the medium by nuclear magnetic resonance revealed significant differences between the two dietary groups as well as between cells exposed to DFMO and DENSPM, with decreased glucose, fumarate and lactate concentrations in media of the HA cells. Liver cells from fish fed the HA diet had higher spermidine/spermine-N1-acetyltransferase protein abundance and lower adenosine triphosphate concentration as compared to the LA-fed fish, while gene expression was not affected by either diet or treatment. Primary liver cells isolated from salmon fed a commercial diet and cultured in L-15 media with or without arginine supplementation (1.82 or 3.63 mM) for 48 h, representing short-term effect of arginine supplementation, showed differential expression of genes for apoptosis and polyamine synthesis due to arginine supplementation or inhibition by DFMO. Overall, arginine concentration and exposure time affected energy metabolism and gene regulation more than inhibition or activation of key enzymes of polyamine metabolism, suggesting a polyamine-independent influence of arginine on cellular energy metabolism and survival.

Feed intake and brain neuropeptide Y (NPY) and cholecystokinin (CCK) gene expression in juvenile cobia fed plant-based protein diets with different lysine to arginine ratios

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 730 g kg(-1) plant ingredients with 505-529 g protein, 90.2-93.9 g lipid kg(-1) dry matter; control diet contained 550 g protein and 95 g lipid kg(-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.

Intestinal absorption of amino acids in the Pacific bluefin tuna (Thunnus orientalis): in vitro lysine-arginine interaction using the everted intestine system

The interaction between lysine (Lys) and arginine (Arg) in the proximal intestinal region of Pacific bluefin tuna (Thunnus orientalis) was evaluated using the everted intestine method. This in vitro intestinal system has been shown to be an effective tool for studying the nutrient absorption without the need to handle the tuna fish in marine cages as needed for digestibility and amino acid (AA) absorption. We used a factorial design with two sets of variables: low and high Lys concentration (10 and 75 mM) and four different Arg concentrations (3, 10, 20, and 30 mM). Both amino acids were dissolved in marine Ringer solution with a basal amino acidic composition consisting of a tryptone solution (9 mg mL(-1)). No interaction was observed between the absorption of Lys and Arg during the first 10 min of the experiment when low concentration of Lys and Arg was used in the hydrolyzate solution. However, there seemed to be a positive effect on Lys absorption when both amino acids were at high concentrations (30 and 75 mM, respectively). This type of studies will led us to test different formulations and/or additives to better understand the efficiency of AA supplementation as an alternative to in situ studies that are difficult to follow to design with the Pacific Bluefin Tuna.

Contribution of dietary arginine to nitrogen utilisation and excretion in juvenile sea bass (Dicentrarchus labrax) fed diets differing in protein source

The role of dietary arginine in affecting nitrogen utilisation and excretion was studied in juvenile European sea bass (Dicentrarchus labrax) fed for 72 days with diets differing in protein sources (plant protein-based (PM) and fish-meal-based (FM)). Fish growth performance and nitrogen utilisation revealed that dietary Arg surplus was beneficial only in PM diets. Dietary Arg level significantly affected postprandial plasma urea concentrations. Hepatic arginase activity increased (P<0.05) in response to dietary Arg surplus in fish fed plant protein diets; conversely ornithine transcarbamylase activity was very low and inversely related to arginine intake. No hepatic carbamoyl phosphate synthetase III activity was detected. Dietary arginine levels did not affect glutamate dehydrogenase activity. A strong linear relationship was found between liver arginase activity and daily urea-N excretion. Dietary Arg excess reduced the proportion of total ammonia nitrogen excreted and increased the contribution of urea-N over the total N excretion irrespective of dietary protein source. Plasma and excretion data combined with enzyme activities suggest that dietary Arg degradation via hepatic arginase is a major pathway for ureagenesis and that ornithine-urea cycle is not completely functional in juvenile sea bass liver.

The optimum dietary indispensable amino acid pattern for growing Atlantic salmon (Salmo salarL.) fry

To determine the optimum indispensable (I) amino acid (AA) balance in Atlantic salmon (Salmo salarL.) fry, a single protocol established for the pig was adapted. The balance was calculated from the reduction in N gain after replacing about 45% of a single IAA by a mixture of dispensable AA in isonitrogenous diets. We confirmed that the mixture of AA simulating the AA pattern of cod-meal protein and gelatine (46:3, w/w) was used with the same efficiency as cod-meal protein and gelatine. From the deletion experiment an optimum balance between the IAA was derived. Expressed relative to lysine=100, the optimal balance was: arginine 76 (se 0·2), histidine 28 (se 2·2), methionine+cystine 64 (se 1·7), phenylalanine + tyrosine 105 (se 1·6), threonine 51 (se 2·4), tryptophan 14 (se 0·7), valine 59 (se 1·7). No estimates were made for isoleucine and leucine. Expressed as g/16g N, the optimal balance was: arginine 4·0 (se 0·0), histidine 1·5 (se 0·1), lysine 5·3 (se 0·2), methionine+cystine 3·4 (se 0·1), phenylaline+tyrosine 5·6 (se 0·1), threonine 2·7 (se 0·1), tryptophan 0·7 (se 0·0), valine 3·1 (se 0·1). This AA composition is close to that of the Atlantic salmon whole-body, but using it as an estimation of the IAA requirements may lead to an overestimation of the branched-chain AA requirements and an underestimation of aromatic and S-containing AA requirements. The results are discussed in accordance with the key assumptions associated with the model used (broken-line model, IAA efficiencies and maintenance requirements).

Ureotelism is inducible in the neotropical freshwater Hoplias malabaricus (Teleostei, Erythrinidae)

Increased environmental pH decreases ammonia transport through the gills, impairing nitrogenous waste. The consequent toxicity is usually drastic to most fishes. A few species are able to synthesize urea as a way to detoxify plasma ammonia. We studied three teleosts of the family Erythrinidae living in distinct environments, and assumed the biochemical behaviors would be different in spite of their being closely related species. Adult fish collected in the wild were submitted to alkaline water and the urea excretion rate was determined. The specific activity of urea cycle enzymes was determined in liver samples of fish from neutral waters. The studied species Hoplias lacerdae, Hoplerithrynus unitaeniatus, and Hoplias malabaricus are ureogenic. Urea synthesis is not a metabolic way to detoxify ammonia in H. lacerdae and Hoplerithrynus unitaeniatus exposed to an alkaline environment. The plasma ammonia profile of both species showed two distinct biochemical responses. Urea excretion of H. malabaricus was high in alkaline water, and the transition to ureotelism is proposed. The nitrogen excretion rate of H. malabaricus was among the highest values reported and the high urea excretion leads us to include this species as ureotelic in alkaline water.

Dietary arginine degradation is a major pathway in ureagenesis in juvenile turbot (Psetta maxima)

Recent studies indicate that urea excretion is responsive to protein intake and that turbot, Psetta maxima, appear to differ from other species by their urea excretion pattern and levels. This study was undertaken to evaluate the influence of dietary nitrogen and arginine on ureagenesis and excretion in turbot. Juvenile turbot (29 g) were fed semi-purified diets containing graded levels of nitrogen (0-8% dry matter) and arginine (0-3% dry matter) for 6 weeks. Growth data showed that turbot have high dietary nitrogen (123 mg/kg metabolic body weight/day) and very low dietary arginine (9.3 mg/kg metabolic body weight/day) requirements for maintenance. Requirements for unit body protein accretion were 0.31 g and 0.15 g for nitrogen and arginine respectively. Post-prandial plasma urea levels and urea excretion rates showed that urea production was significantly (P<0.05) influenced by dietary arginine levels. While hepatic arginase (EC 3.5.3.1) activity increased significantly (P<0.05) with increasing dietary arginine levels, activities of other enzymes of the ornithine urea cycle were very low. Our data strongly suggest that the ornithine urea cycle is not active in the turbot liver and that dietary arginine degradation is a major pathway of ureagenesis in turbot.