Plasma Free Amino Acid Concentrations Research Articles

The role of amino acid profiles in diabetes risk assessment.

The concentrations of plasma-free amino acids, such as branched-chain amino acids and aromatic amino acids, are associated with visceral obesity, insulin resistance, and the future development of diabetes and cardiovascular diseases. This review discusses recent progress in the early assessment of the risk of developing diabetes and the reversal of altered plasma-free amino acids through interventions. Additionally, recent developments that have increased the utility of amino acid profiling technology are also described. Plasma-free amino acid alterations in the early stage of lifestyle-related diseases are because of obesity and insulin resistance-related inflammation, and these alterations are reversed by appropriate (nutritional, drug, or surgical) interventions that improve insulin sensitivity. For clinical applications, procedures for measuring amino acids are being standardized and automated. Plasma-free amino acid profiles have potential as biomarkers for both assessing diabetes risk and monitoring the effects of strategies designed to lower that risk. In addition, the methodology for measuring amino acids has been refined, with the goal of routine clinical application.

Plasma amino acid profiles in healthy East Asian subpopulations living in Japan

ObjectivesProfiles of plasma free amino acids (PFAAs) have been utilized as biomarkers to detect various diseases. However, few studies have investigated whether ethnicity or specific subpopulations within East Asia influence PFAA concentrations.MethodsA total of 95 healthy volunteers living in Japan, including 31 Japanese individuals, 36 Korean individuals and 28 Chinese individuals, were enrolled. Participants’ PFAA levels were measured by high‐performance liquid chromatography mass spectrometry, and the effects of factors such as sex, age, body mass index (BMI) and subpopulation on PFAA profiles were analyzed.ResultsWith the exception of glutamine and α‐aminobutyric acid, there were no significant differences among the three examined subpopulations with respect to either the means or the distributions of PFAA concentrations. A multiple regression analysis revealed that most of the PFAA concentrations were significantly related to sex. Ornithine concentrations, glutamate concentrations, and glutamine and α‐aminobutyric acid concentrations were significantly associated with age, BMI, and Chinese subpopulation, respectively.ConclusionThe study results indicate that the contributions of subpopulation within East Asia to PFAA profiles are small, particularly relative to the contributions provided by sex. Am. J. Hum. Biol. 28:236–239, 2016. © 2015 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.

Changes in plasma osmolality, cortisol and amino acid levels of tongue sole (Cynoglossus semilaevis) at different salinities

A serial of salinity transferring treatments were performed to investigate the osmoregulation of tongue sole (Cynoglossus semilaevis). Juvenile tongue sole were directly transferred from a salinity of 30 to 0, 10, 20, 30, 40 and 50. Blood sampling was performed for each treatment after 0, 1, 6 and 12 h, as well as after 1, 2, 4, 8, 16 and 32 d. The plasma osmolality, cortisol and free amino acids were assessed. Under the experimental conditions, no fish died after acute salinity transfer. The plasma cortisol level increased 1 h after the abrupt transfer from a salinity of 30 to that of 0, 40 and 50, and decreased from 6 h to 8 d after transfer. Similar trends were observed in the changes of plasma osmolality. The plasma free amino acids concentration showed a ‘U-shaped’ relationship with salinity after being transferred to different salinities for 4 days. More obvious changes of plasma free amino acid concentration occurred under hyper-osmotic conditions than under hypo-osmotic conditions. The concentrations of valine, isoleucine, lysine, glutamic acid, glycine, proline and taurine increased with rising salinity. The plasma levels of threonine, leucine, arginine, serine, and alanine showed a ‘U-shaped’ relationship with salinity. The results of this study suggested that free amino acids might have important effects on osmotic acclimation in tongue sole.

The Influence of Dietary Lysine on Yellow Perch Maturation and the Quality of Sperm

AbstractThe objective of the present study was to determine whether lysine (Lys) supplementation influences the maturation and sperm quality of Yellow Perch Perca flavescens. Juveniles raised on a formulated commercial diet and weighing approximately 75 g each were randomly distributed into six 400‐L tanks. This experiment included two wheat‐gluten‐based diets in triplicate: (−) Lys (Lys‐deficient) and (+) Lys (Lys‐supplemented; 2.23% in dry feed) diets. In addition, 16 control fish were kept under identical conditions and fed a commercial diet. The weight of males was larger in the control group than in the (+) Lys and (−) Lys groups. The sperm concentration was significantly higher in the control and (+) Lys groups than in the (−) Lys group. Sperm motility was lower in the (−) Lys group than in the control and (+) Lys groups. The control group had significantly higher protein concentration in its seminal plasma than did the (+) Lys and (−) Lys groups. The seminal plasma trypsin inhibitor activity showed the same trend. The seminal plasma free amino acid concentrations of arginine, methionine, threonine, glutamine, alanine, and glycine differed significantly among treatments. This is the first report demonstrating the negative effect of dietary lysine level in plant‐protein‐based diets on reproduction in fish.

Effects of plant proteins on postprandial, free plasma amino acid concentrations in rainbow trout ( Oncorhynchus mykiss)

Postprandial patterns in plasma free amino acid concentrations were investigated in juvenile rainbow trout ( Oncorhynchus mykiss ) fed either a fish meal based diet (FM) or a diet (VEG) where 59% of fish meal protein (corresponding to 46% of total dietary protein) was replaced by a matrix of plant proteins from wheat, peas, field beans, sunflower and soybean. Blood samples were obtained from the caudal vein of 7 fish in each dietary treatment group prior to feeding, as well as: 2, 4, 6, 8, 12, 24, 48 and 72 h after feeding (sampling 7 new fish at each time point), and plasma amino acid concentrations were subsequently measured by HPLC. Nutrient digestibility and ammonia excretion of the two experimental diets were measured in a parallel experiment using a modified Guelph setup. Results showed that the appearance of most amino acids (essential and non-essential) in the plasma was delayed in fish fed the VEG diet compared to those fed the FM diet. Essential and non-essential amino acids furthermore appeared more or less synchronously in the plasma in fish fed the FM diet, while the appearance was less synchronised in fish fed the VEG diet. Differences in plasma concentrations between the two dietary treatment groups correlated largely with the amino acid content of the two diets except for methionine, lysine and arginine, where the differences were more extreme than what would be expected from differences in dietary concentrations. The apparent protein digestibility coefficient was higher in the VEG diet than in the FM diet (93 versus 92%; t-test, P < 0.05), supporting that protease inhibitors from plant protein ingredients were not the cause of the delay. The apparent digestibility coefficient of carbohydrates (calculated as nitrogen-free extract (NFE)) was much lower in the VEG than in the FM diet (51 versus 76%; t-test, P < 0.05). Combined with a higher NFE content in the VEG diet, this meant that there was 2.7 times more indigestible NFE in the VEG than in the FM diet (6.1 versus 2.2 g 100 − 1 g feed). Such difference may suggest that the uptake of amino acids (AA) was affected by dietary carbohydrates. Total ammonia-nitrogen (TAN) excretion was slightly, but non-significantly, higher in VEG fed fish than in FM fed fish (59 versus 55 mg TAN g − 1 digested protein; t-test, P > 0.05). In conclusion, the study showed that amino acid uptake patterns are affected when replacing fish meal with plant based protein ingredients.

Effects of urea and soybean meal supplementation on rates of plasma leucine turnover and protein synthesis in sheep fed concentrate-based diets

The isotope dilution method of [1-13C]leucine (Leu) and open-circuit calorimetry were used to determine the effects of urea and soybean meal (SBM) supplementation on rates of plasma Leu turnover and whole body protein synthesis (WBPS) in sheep fed concentrate-based diets. The experiment was performed in a replicated 3×3 Latin square design. The control diet (Control diet) consisted of timothy hay and ground corn. The urea supplemented diet (Urea diet) was supplemented with 3.1% urea of the Control diet. The SBM diet was similar to nitrogen and ME contents to the Urea diet by replacing 40% ground corn of the Control diet to the SBM. Plasma urea concentration was higher (P<0.05) for the SBM and Urea diets compared with the Control diet, but plasma ammonia concentration remained similar for all diets. Plasma free amino acid concentration also remained unchanged between the diets, except for plasma glycine concentration. Plasma Leu turnover rate and WBPS did not differ between the diets, but they were numerically higher for the SBM diet compared with the Control and Urea diets. These results suggest that in sheep, urea and SBM supplementation influence little on plasma Leu and protein metabolism, when concentrate-based diets are given.

Impact of complicated intra-abdominal infection on albumin synthesis rate

To study the impact of complicated intra-abdominal infections on albumin synthesis rate. Eight patients with complicated intra-abdominal infections associated with intestinal fistula were admitted to the Research Institute of General Surgery at the Jinling Hospital between December 2009 and October 2010. Eight healthy volunteers matched for age, sex, and body mass index were enrolled as controls. All the subjects were given a primed, constant infusion of sterile L-[ring-(2)H(5)]-phenylalanine solution (priming dose: 4 μmol/kg, infusion rate: 6 μmol·kg(-1)·min(-1)) via peripheral venous lines in fast state. Arterial blood samples(3 ml) were drawn before and throughout the infusion at hourly intervals. The enrichment of L-[ring-(2)H(5)]-phenylalanine from the plasma free amino acid pool and from albumin were determined by gas chromatography/mass spectrometry analysis. Both plasma total protein concentration(62.2±1.0) g/L and plasma albumin concentration (32.5±4.0) g/L in patients with complicated intra-abdominal infection were lower compared with controls[(74.2±1.7) g/L and (46.1±2.6) g/L, both P<0.05]. Body temperature, neutrophil count and plasma C-reactive protein concentration in patients with infection were significantly greater than the levels in control subjects(P<0.05). Albumin synthesis rate in patients with intra-abdominal infection was significantly lower than that in the control group [(5.3±1.6)%/d and (7.8±1.2)%/d respectively, P<0.05]. The measurement of plasma free amino acid concentration showed that plasma glutamic acid level was greater than that in control subjects, and that plasma phenylalanine and proline levels were lower than those in controls. Complicated intra-abdominal infection inhibits albumin synthesis rate in patients with intestinal fistula, which may partially contribute to the decrease of plasma albumin concentration.

Effects of Oral Glucosamine Hydrochloride Administration on Plasma Free Amino Acid Concentrations in Dogs

We examined the effects of oral glucosamine hydrochloride (GlcN), N-acetyl-d-glucosamine (GlcNAc) and d-glucose (Glc) administration on plasma total free amino acid (PFAA) concentrations in dogs. The PFAA concentrations increased in the control group and the GlcNAc group at one hour after feeding, and each amino acid concentration increased. On the other hand, in the GlcN group and the Glc group PFAA concentrations decreased at one hour after feeding. A significant decrease in amino acid concentration was observed for glutamate, glycine and alanine. Our results suggest the existence of differences in PFAA dynamics after oral administration of GlcN and GlcNAc in dogs.

Regulation of muscular glutamate metabolism by high‐protein diet in broiler chicks

The major taste active component, glutamate (Glu), improves the taste of meat. In this study, we investigated the effect of a short-term high-protein (HCP) diet on the intramuscular free Glu content to improve the taste of meat. Furthermore, we elucidated how the muscle free Glu content was controlled by the HCP diet. Chicks (14 days old) were fed the control diet or HCP diet for 10 days. Plasma and muscle free amino acid concentrations, and activity and messenger RNA (mRNA) expression of muscle enzymes related to Glu metabolism were determined. Muscle free Glu content was increased (P < 0.01) by 51%. Activity and mRNA expression of glutaminase (GA), which is one of the major Glu-related enzymes, were significantly decreased (P < 0.05) in the HCP group because of feedback inhibition. The mRNA expression of lysine α-ketoglutarate reductase (LKR), which is the enzyme involved in lysine (Lys) degradation and Glu production, was significantly increased (P < 0.001) in the HCP group. These results suggest that short-term dietary HCP feeding is an effective treatment for improving the taste of meat. Furthermore, our results suggest that the free Glu content in muscle is regulated by GA and LKR.

Abstract 4633: A novel screening marker for breast cancer composed of plasma free amino acid concentrations “AminoIndex”

Abstract Introduction Amino acids balance is changed in patients of various diseases due to metabolic transition while it is maintained in healthy human. For example, it is known to change in liver dysfunction, renal failure, and cancers. Therefore, it is expected that the detection of metabolic transition using amino acid profiles is a promising screening marker of various cancers. We previously showed significant changes of plasma amino acid profiles and discriminating functions using plasma amino acid concentrations “AminoIndex” in various cancer patients including breast cancer. In this study, further possibilities of “AminoIndex” for breast cancer were investigated by case-control study from multiple medical facilities. Subjects and Methods Plasma samples were collected from Japanese breast cancer patients those were hospitalized in three hospitals and finally diagnosed before any medical treatment (N=295). Those of controls were also collected from subjects who were undergone comprehensive medical examination at two hospitals (N=2,147). Plasma amino acid concentrations were measured by LC-MS. Among them, 90 patients (30 from each hospital) in chronological order and 450 age-matched control subjects were chosen as training data set. And the rest (205 patients and 1,697 controls, respectively) were used as test data set to valid the inferred “AminoIndex”. Using training data set, plasma amino acid concentration were compared and then “AminoIndex”, multivariate logistic regression function composed of plasma amino acid concentrations, was inferred to discriminate breast cancer from control subjects. Results Plasma concentrations of several amino acids were significantly changed in breast cancer patients compared to control subjects. Predicted “AminoIndex” for breast cancer was resulted the multivariate logistic function composed with six amino acids. To evaluate the performance of the index predicted, the ROC curve for each predictive score was calculated, and this gave an AUC of ROC of 0.764 using the study data. Then, validation of predicted “AminoIndex” was performed using test data set, resulting almost same diagnostic performance. Furthermore, predicted “AminoIndex” showed notably features; the index could discriminate breast cancer patients almost equally in any stages, and the index showed not only higher discrimination performance than those of existing tumor markers but also distributed independently of the levels of various tumor markers. Therefore, predicted “AminoIndex” would be suitable for screening and early detection of breast cancer patients. Conclusion and Perspectives In this study, we demonstrated that change of plasma amino acid profile would be an indicator of breast cancer and a helpful tool for early detection of breast cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4633.

Semen characteristics of boars receiving control diet and control diet supplemented with L-carnitine

The objective of this experiment was to test a hypothesis that L-carnitine supplemented diet would improve semen characteristics in 6 adult crossbred AI boars (Hampshire × Pietrain). The control and the tested diet were identical except the tested period (8 weeks) when the diet was supplemented with 2 g of L-carnitine per boar per day. The semen was collected regularly weekly by a gloved-hand technique. Semen volume, sperm motility and concentration, proportion of alive sperm cells and aspartate aminotransferase (AspAT) activity of semen were determined immediately after the semen collection once every two weeks. Sperm survival rate, morphologically abnormal spermatozoa, seminal plasma mineral components and free amino acid concentration, L-carnitine concentration in semen plasma and in sperm cells were determined after the sample storage (–20°C) at a later time. The differences ascertained between the average values of semen characteristics in the control vs. tested period did not prove a true and unambiguous positive effect on boar semen parameters by dietary supplementation of L-carnitine as our data show in our study: volume (239.11 vs. 250.50 ml; &lt;I&gt;P&lt;/I&gt; 0.518), sperm concentration (301.67 vs. 350.83 × 10&lt;sup&gt;3&lt;/sup&gt;/mm&lt;sup&gt;3&lt;/sup&gt;; &lt;I&gt;P&lt;/I&gt; 0.309), sperm progressive motility (66.94 vs. 70.00%; &lt;I&gt;P&lt;/I&gt; 0.409), morphologically abnormal spermatozoa (29.00 vs. 27.46%; &lt;I&gt;P&lt;/I&gt; 0.802), daily sperm cells output (9.86 vs. 11.71 × 10&lt;sup&gt;9&lt;/sup&gt;; &lt;I&gt;P&lt;/I&gt; 0.206), proportion of alive sperm cells (72.56 vs. 74.13%; &lt;I&gt;P&lt;/I&gt; 0.484), survival spermatozoa ability maintenance (43.29 vs. 38.68%; &lt;I&gt;P&lt;/I&gt; &lt; 0.01), mineral components in the seminal plasma (Na-, K-, Ca-, Mg-, Zn-; P from 0.138 to 0.968), AspAT activity (in semen plasma – 132.50 vs. 128.31 mU/10&lt;sup&gt;9&lt;/sup&gt; spermatozoa; &lt;I&gt;P&lt;/I&gt; 0.830, in sperm cells – 147.37 vs. 119.01 mU/10&lt;sup&gt;9&lt;/sup&gt; spermatozoa; &lt;I&gt;P&lt;/I&gt; 0.146), semen plasma amino acid concentration – a significant positive effect of L-carnitine in lysine only (0.79 vs.1.17 &amp;mu;mol/100 ml; &lt;I&gt;P&lt;/I&gt; &lt; 0.01), L-carnitine concentration (in semen plasma 255.40 vs. 259.97 mg/l; &lt;I&gt;P&lt;/I&gt; 0.884, in sperm cells – 1 110.68 vs. 883.58 mg/l; &lt;I&gt;P&lt;/I&gt; &lt; 0.01). In conclusion, the studied indicators of semen quality were not significantly enhanced by dietary supplementation of L-carnitine in adult AI boars.

Effects of early-and mid-pregnancy under-nutrition on maternal and foetal plasma free amino acid concentrations in Scottish Blackface and Suffolk sheep

Nutrient intake during pregnancy affects foetal development and placental function in a range of species, often with long-term effects on offspring viability. Maternal supply and placental transport of amino acids are key to delivering amino acids for foetal metabolism. Maternal under-nutrition has been shown to reduce both maternal and foetal amino acid concentrations even after a period of re-feeding (Kwon et al. 2004). Intriguingly whether sheep have been adapted to a harsh environment or not appears to influence the extent of any reduction (Jobgen et al. 2008). The present study therefore tested whether plasma amino acid concentrations differed between Scottish Blackface (B) sheep adapted to a hill environment and a lowland breed (Suffolk, S) selected for lean tissue growth when challenged by a period of under-nutrition.

Effect of circulating insulin concentration on whole body and muscle protein metabolism in mature thoroughbred mares

The role of insulin (INS) in carbohydrate metabolism and the development of certain metabolic diseases has been well studied in horsse; however, there has been minimal research with regards to the role that INS plays in equine protein metabolism. The objective of this study was to determine the effect of circulating INS concentration on whole‐body protein metabolism and the activation of translation initiation factors in muscle. Mature thoroughbred mares (n=8) underwent euglycemic clamp procedures at each of 4 different rates of INS infusion: 0, 1.2, 3 and 6 mU/kg/min. Blood samples were taken during the clamp and at the end of the clamp a biopsy from the gluteal muscle was taken. Western blotting was used to examine the phosphorylation of protein synthesis initiation factors Akt, rpS6 and 4E‐BP1 in the gluteal muscle, and HPLC was used to determine plasma and muscle free amino acid concentrations. INS infusion resulted in a decrease (P &lt; 0.05) in the plasma concentration of all indispensable amino acids, with greater decreases seen with increasing rates of INS infusion. Muscle free valine, leucine and isoleucine concentrations were also lower (P &lt; 0.05) following INS infusion, in a dose dependent manner. Akt phosphorylation was maximized at 6 mU/kg/min INS, while rpS6 and 4E‐BP1 phosphorylation was maximized at 3 mU/kg/min INS. INS infusion appeared to promote both whole‐body amino acid utilization and activation of translation initiation factors in muscle of mature horses. Future research should focus on the effects of altered INS sensitivity on equine protein metabolism. Funded by estate of the late Paul Mellon.

Effects of Squat Exercise and Branched-Chain Amino Acid Supplementation on Plasma Free Amino Acid Concentrations in Young Women

The present study was conducted to examine alterations in plasma free amino acid concentrations induced by squat exercise and branched-chain amino acid (BCAA) supplementation in young, untrained female subjects. In the morning on the exercise session day, participants ingested drinks containing either BCAA (isoleucine:leucine:valine=1:2.3:1.2) or dextrin (placebo) at 0.1 g/kg body weight 15 min before a squat exercise session, which consisted of 7 sets of 20 squats, with 3 min intervals between sets. In the placebo trial, plasma BCAA concentrations were decreased subsequent to exercise, whereas they were significantly increased in the BCAA trial until 2 h after exercise. Marked changes in other free amino acids in response to squat exercise and BCAA supplementation were observed. In particular, plasma concentrations of methionine and aromatic amino acids were temporarily decreased in the BCAA trial, being significantly lower than those in the placebo trial. These results suggest that BCAA intake before exercise affects methionine and aromatic amino acid metabolism.

Dietary carbohydrates and amino acids influence oocyte quality in dairy heifers

The objective of the present experiment was to determine whether increasing plasma insulin by different nutritional regimes affects oocyte quality. Holstein dairy heifers (eight per treatment) were assigned, using a two times two factorial design, to diets containing either low or high dietary leucine and either low or high dietary starch. Each heifer underwent six sessions of ovum pick-up beginning 25 days after introduction of the diets. Oocyte quality was assessed by development to the blastocyst stage in synthetic oviducal fluid following in vitro fertilisation. Feeding diets containing high leucine resulted in significantly higher plasma free leucine and tyrosine concentrations. The high-starch diet significantly increased plasma insulin but not glucagon concentration, whereas high dietary leucine increased plasma glucagon but not insulin. Oocyte cleavage was not influenced by diet. The high-starch diet, which was associated with a high plasma insulin : glucagon ratio, had adverse effects on oocyte quality that were avoided when leucine intake was increased. There was an association between total plasma free amino acid concentration and oocyte cleavage. Therefore, in dairy heifers dietary amino acids and carbohydrates during antral follicle development appear to mediate effects on oocyte quality by different mechanisms. These findings have implications for both diet formulation and feeding regimes.

Changes of plasma free amino acid concentrations and myofibrillar proteolysis index by starvation in non‐pregnant dry cows

ABSTRACTThe effects of 5 day starvation on urinary metabolite excretion, plasma metabolites and free amino acid concentrations in four non‐pregnant dry cows were investigated. Starvation significantly reduced (P &lt; 0.05) the bodyweight and feces weight. The plasma glucose concentration decreased (P &lt; 0.05) during days 2–5 of starvation. Starvation significantly increased (P &lt; 0.05) the plasma nonesterified fatty acid concentration. The plasma urea nitrogen concentration and urinary urea nitrogen excretion increased transiently (P &lt; 0.05) at days 1 and 2 of starvation. The plasma 3‐methlhistidine concentration was significantly higher (P &lt; 0.05) at days 2, 3 and 5 of starvation. However, the urinary 3‐methylhistidine excretion was significantly higher (P &lt; 0.05) at days 4 and 5 of starvation, not corresponding to the change in the plasma. Starvation did not change the plasma proline, methionine, lysine and total amino acid concentrations. On the other hand, starvation reduced (P &lt; 0.05) the plasma aspartic acid, serine, asparagine, glutamic acid, glutamine, alanine, tyrosine, tryptophan and histidine concentrations. Plasma glycine increased during starvation. Plasma threonine, isoleucine, leucine and branched‐chain amino acid increased (P &lt; 0.05) by prolonged starvation. The results of this study indicate that prolonged starvation accelerated myofibril protein degradation in non‐pregnant dry cows and apparently consumes most glucogenic amino acids in preference to other amino acids.

The Effects of Endotoxin on Plasma Free Amino Acid Concentrations in Rats

We examined the effects of lipopolysaccharide (LPS) injection on body temperature and plasma free amino acid concentrations in rats. A catheter was placed in the jugular vein of the rats in order to draw blood from and to inject LPS into awake animals. On the day of the experiment, body temperature was recorded during the experiment (330 min) and blood was drawn before and at several time points after injection of LPS (10 microg/kg body weight). Body temperature in LPS-treated rats began to rise approximately 30 min after injection with a peak at 120 min, and afterward remained approximately 1 degree C higher than that in control rats through the end of the experiment. Concentrations of many plasma free amino acids were decreased by LPS treatment, with a nadir at approximately 120 min, and then were increased to the level of or over the control. It appears that thermoregulatory responses induced by LPS treatment may be related to alterations in plasma free amino acid concentrations. Effects of LPS treatment on the dynamics of plasma free branched-chain amino acid (BCAA) concentrations in rats with peroral or intravenous administration of BCAAs were also examined. The results showed that the rise in plasma BCAA concentrations after peroral BCAA administration was significantly suppressed by LPS treatment, but the dynamics of plasma BCAAs after intravenous administration was not affected by LPS, suggesting that LPS treatment inhibited the intestinal absorption of BCAAs into the circulation. These results suggest that the availability of administered BCAAs to the body tissues during sepsis is higher following parenteral than peroral administration.

Growth, stress response and free amino acid levels in Senegalese sole (Solea senegalensis Kaup 1858) chronically exposed to exogenous ammonia

Stressful husbandry conditions are likely to affect growth and amino acid metabolism in fish. In this study, chronic ammonia exposure was used to test the effects of a stressor on growth and amino acid metabolism of Senegalese sole juveniles. The fish were exposed for 52 days to 11.6 mg L−1 [low-TAN (L-TAN)] or 23.2 mg L−1 [high-TAN (H-TAN)] of total ammonia nitrogen (TAN), or to 0 mg L−1 (Control). Growth in L-TAN groups was slightly but significantly different from the Control groups [relative growth rate (RGR=0.35±0.13 and 0.52±0.23% day−1 respectively)]. In H-TAN groups, growth was severely affected (RGR=0.01±0.13% day−1). Stress parameters (plasma cortisol and glucose) showed slight or no significant differences between treatments. Plasma free amino acid (FAA) concentrations were affected after H-TAN treatment. Increases in glutamine and aspartate concentrations in H-TAN fish suggest alterations in amino acid metabolism related to nitrogen excretion processes. Some of the changes in FAA concentrations also suggest mobilization to energy supply and synthesis of metabolites related to stress response. Therefore, Senegalese sole seem to adapt to the L-TAN concentration tested, but the H-TAN concentration reduced growth and affected amino acid metabolism.

Growth Depression in Socially Subordinate Rainbow TroutOncorhynchus mykiss: More than a Fasting Effect

To assess the effects of subordinate social status on digestive function, metabolism, and enzyme activity in salmonid fish, juvenile rainbow trout Oncorhynchus mykiss were paired with size-matched conspecifics (<1.5% difference in fork length) for 5 d. Fish that were fasted for 5 d and fish sampled directly from the holding tank were used as control groups. Both subordinate and fasted fish experienced significant decreases in intestine mass (P = 0.043), and the gall bladder showed marked and significant changes in both size (P = 0.004) and appearance. These findings suggest that the negative effect of social subordination on digestive function reflects in large part a lack of feeding. Hepatic phosphoenolpyruvate carboxykinase activity was significantly higher in subordinate fish relative to dominants, whereas subordinate hepatic pyruvate kinase activity was significantly lower; activities of both enzymes were significantly correlated with plasma cortisol concentrations and behavior scores. Dominant-subordinate differences in the activities of these enzymes were eliminated by administration of the glucocorticoid receptor antagonist RU486, underlining a role for circulating cortisol in eliciting the differences. Significant increases relative to control fish were also detected in red and white muscles from subordinate fish in the activities of protein catabolic enzymes (aspartate aminotransferase, alanine aminotransferase, glutamate dehydrogenase). These differences occurred in the absence of any change in plasma free amino acid or ammonia concentrations, supporting an enhanced turnover of amino acids in muscle in subordinate fish. The results support the hypothesis that changes in metabolism, beyond those elicited by low food consumption, may be responsible at least in part for the low growth rates typical of subordinate fish and that these changes may be related specifically to circulating cortisol levels in subordinate fish.

Metabolic organization of the spotted ratfish,Hydrolagus colliei (Holocephali: Chimaeriformes): insight into the evolution of energy metabolism in the chondrichthyan fishes

The metabolic organization of a holocephalan, the spotted ratfish (Hydrolagus colliei), was assessed using measurements of key enzymes of several metabolic pathways in four tissues and plasma concentrations of free amino acids (FAA) and non-esterified fatty acids (NEFA) to ascertain if the Holocephali differ metabolically from the Elasmobranchii since these groups diverged ca. 400 Mya. Activities of carnitine palmitoyl transferase indicate that fatty acid oxidation occurs in liver and kidney but not in heart or white muscle. This result mirrors the well-established absence of lipid oxidation in elasmobranch muscle, and more recent studies showing that elasmobranch kidney possesses a capacity for lipid oxidation. High activities in oxidative tissues of enzymes of ketone body metabolism, including D-beta-hydroxybutyrate dehydrogenase, indicate that, like elasmobranchs, ketone bodies are of central importance in spotted ratfish. Like many carnivorous fishes, enzyme activities demonstrate that amino acids are metabolically important, although the concentration of plasma FAA was relatively low. NEFA concentrations are lower than in teleosts, but higher than in most elasmobranchs and similar to that in some "primitive" ray-finned fishes. NEFA composition is comparable to other marine temperate fishes, including high levels of n-6 and especially n-3 polyunsaturated fatty acids. The metabolic organization of the spotted ratfish is similar to that of elasmobranchs: a reduced capacity for lipid oxidation in muscle, lower plasma NEFA levels, and an emphasis on ketone bodies as oxidative fuel. This metabolic strategy was likely present in the common chondrichthyan ancestor, and may be similar to the ancestral metabolic state of fishes.