Amino Acid Content Of Muscle Research Articles

Effects of dietary methionine and taurine interaction on growth performance, the profiles of amino acids, and protein metabolism of Chinese mitten crab, Eriocheir sinensis

The purpose of this study is to explore the interaction between dietary methionine and taurine levels on growth performance, the profiles of amino acids, protein metabolism, and how taurine spares methionine of Chinese mitten crab (Eriocheir sinensis). The crabs were divided into six groups which were fed six diets formulated with two Tau levels (0 and 0.4%) and three Met levels (0.6%, 0.9% and 1.2%). The results showed that the weight gain rate and specific growth rate were the highest in the crabs fed 0.4% Tau and 0.6% Met. Crabs fed 1.2% Met had the highest survival rate and lowest feed conversion ratio. Furthermore, the hepatopancreas and muscle amino acid content were significantly influenced by the interactive effects of Met and Tau (P < 0.05). Moreover, interactive effects of dietary methionine and taurine were significantly observed in the expressions of amino acid metabolism-related genes (P < 0.05). Additionally, crabs fed 1.2% Met and 0% Tau had the highest activities of cysteine decarboxylase (CSD) and cysteine dioxygenase (CDO). In conclusion, the addition of appropriate amount of taurine to the diet can reduce the requirement of methionine for Chinese mitten crab by regulating the activities of CSD and CDO. At the same time, the addition of methionine and taurine could affect the amino acids metabolism. Therefore, the diet formula of Chinese mitten crab needs to consider the metabolism of sulfur-containing amino acids.

Insights into Dietary Different Co-Forms of Lysine and Glutamate on Growth Performance, Muscle Development, Antioxidation and Related Gene Expressions in Juvenile Grass Carp (Ctenopharyngodon idellus).

The study aimed to compare the effects of crystalline L-lysine and L-glutamate (CAA), Lys-Glu dipeptide (KE) on the growth and muscle development of grass carp (Ctenopharyngodon idellus), and related molecular mechanisms. Five experimental diets (CR, 0.5% CAA, 1.5% CAA, 0.5% KE, 1.5% KE) containing Lys and Glu as free (Lys and Glu, CAA) dipeptide (Lys-Glu, KE) forms were prepared, respectively. A total of 450 juvenile grass carp with an initial weight of 10.69 ± 0.07g were randomly assigned to 15 cages, and 5 treatments with 3 replicates of 30 fish each for 61days of feeding. The results showed that the group of 0.5% KE exhibited the best growth performances according to the indicator's weight gain rate (WGR) and specific growth rate (SGR), although no statistically significant occurred among all groups; diet supplemented with 0.5% CAA significantly elevated the condition factor (CF) and viscerasomatic index (VSI) of juvenile grass carp. Diet supplemented with different Lys and Glu co-forms at different levels promoted the muscle amino acid content compared with those of CR group. Comparing with the CR group and other groups, the hardness of 0.5% CAA group significantly increased, and the springiness of 0.5% KE group excelled. Both the muscle fiber diameter and density of 0.5% KE group showed significant difference with those of the CR group, and a negative correlation between them was also observed. To uncover the related molecular mechanism of the differences caused by the different co-forms of Lys and Glu, the effect of different diets on the expressions of protein absorption, muscle quality, and antioxidation-related genes was analyzed. The results suggested that comparing with those of CR group, the dipeptide KE inhibited the expressions of genes associated with protein metabolism, such as AKT, S6K1, and FoxO1a but promoted PCNA expression, while the free style of CAA would improve the FoxO1a expression. Additionally, the muscle development-related genes (MyoD, MyOG, and Myf5) were significantly boosted in CAA co-form groups, and the expressions of fMYHCs were blocked but fMYHCs30 significantly promoted in 0.5% KE group. Finally, the effect of different co-forms of Lys and Glu on muscle antioxidant was examined. The 0.5% CAA diet was verified to increase GPX1a but obstruct Keap1 and GSTP1 expressions, resulting in enhanced SOD activity and reduced MDA levels in plasma. Collectively, the different co-forms of Lys and Glu influenced the growth of juvenile grass carp, and also the muscle development and quality through their different regulation on the protein metabolism, muscle development- and antioxidative-related genes.

Role of arginine supplementation on muscular metabolism and flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in freshwater.

It is no doubt that the improvement of flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in freshwater contributes to its development potential in aquaculture. In this study, we aimed to explore the effect of arginine supplementation on the flesh quality of L. vannamei reared in freshwater and its mechanism. L. vannamei were randomly fed with three diets for 56 days, of which arginine level was 10.15 g kg–1 (arginine-deficient diet), 21.82 g kg–1 (arginine-optimal diet), and 32.46 g kg–1 (arginine-excessive diet), respectively. Each diet was randomly assigned to triplicate tanks, and each tank was stocked with 35 shrimps (initial weight: 1.70 ± 0.02 g). Results showed the arginine-optimal diet increased the weight gain, flesh percentage, crude protein and flavor amino acid contents in muscle, and improved the flesh hardness by conversing fast myofibers to slow myofibers, increasing myofiber density and myofibrillar length, and promoting ornithine and collagen synthesis. The arginine-optimal diet influenced the purine metabolic pathway by reducing hypoxanthine, xanthine, and inosine contents. Ornithine, citrulline, and glutamate were identified as the key metabolites affecting flesh quality traits after arginine treatments. Only increasing the levels of dietary arginine did not result in an increase in endogenous creatine synthesis in muscle and hepatopancreas. Overall, the arginine-optimal diet improved the flesh quality traits of L. vannamei reared in freshwater due to the enhanced muscular hardness, protein deposition, and flavor, which may be contributing to the transformation of muscle fiber type and increase in protein synthesis by the metabolites of arginine (ornithine, citrulline, and glutamate).

Effects of Dietary 5′-CMP on Neu5Gc Contents in the Muscle and Viscera of Xiang Pigs

In order to reduce the health risks associated with red meat as listed by the World Health Organization, the work presented in this article aimed to elucidate the interaction between 5'-CMP-supplemented feed and N-glycolylneuraminic acid (Neu5Gc) in experimental animals in vivo. 5'-CMP was added to the diet of 90-, 180-, and 270-day-old Xiang pigs, and after 30 days, the Neu5Gc contents, physicochemical parameters, and free amino acid contents of muscle and internal viscera were measured by high-performance liquid chromatography coupled with fluorescence detection. The mechanism by which 5'-CMP affects Neu5Gc contents was investigated using molecular docking. Results show that 5'-CMP significantly decreased the Neu5Gc content in 180-day-old Xiang pigs (P < 0.05) but had no effect on the Neu5Gc contents in 90- and 270-day-old Xiang pigs. Umami amino acids were significantly increased in 180-day-old Xiang pigs. In the 90- and 270-day-old pigs, histidine increased by 10.38 and 17.87%, respectively. The other free amino acids were either reduced or not affected. Moreover, the 5'-CMP-supplemented diet did not affect the physicochemical parameters of the longissimus muscle in the Xiang pigs. 5'-CMP could occupy almost all the sialyltransferase active-site residues but not His302 and showed inhibition of the sialyltransferase activity. The results provided an experimental basis for the subsequent reduction of Neu5Gc in red meat before slaughter.

Effects of dietary Gelsemium elegans alkaloids on growth performance, immune responses and disease resistance of Megalobrama amblycephala

The present study aim to investigate the effects of dietary Gelsemium elegans alkaloids supplementation in Megalobrama amblycephala. A basal diet supplemented with 0, 5, 10, 20 and 40 mg/kg G. elegans alkaloids were fed to M. amblycephala for 12 weeks. The study indicated that dietary 20 mg/kg and 40 mg/kg G. elegans alkaloids supplementation could significantly improve final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) (P < 0.05). The 20 mg/kg and 40 mg/kg G. elegans alkaloids groups showed significantly higher whole body and muscle crude protein and crude lipid contents compared to the control group (P < 0.05). The amino acid contents in muscle were also significantly increased in 20 mg/kg and 40 mg/kg groups (P < 0.05). Dietary 40 mg/kg G. elegans alkaloids had a significant effect on the contents of LDH, AST, ALT, ALP, TG, TC, LDL-C, HDL-C, ALB and TP in M. amblycephala (P < 0.05). Fish fed 20 mg/kg and 40 mg/kg dietary G. elegans alkaloids showed significant increase in complement 3, complement 4 and immunoglobulin M contents. The liver antioxidant enzymes (SOD, CAT and T-AOC) and MDA content significantly increased at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). The mRNA levels of immune-related genes IL-1β, IL8, TNF-α and IFN-α were significantly up-regulated, whereas TGF-β and IL10 genes were significantly down-regulated in the liver, spleen and head kidney of fish fed dietary supplementation with 20 mg/kg and 40 mg/kg G. elegans alkaloids. After challenge with Aeromonas hydrophila, significant higher survival rate was observed at 20 mg/kg and 40 mg/kg G. elegans alkaloids supplement (P < 0.05). Therefore, these results indicated that M. amblycephala fed a diet supplemented with 20 mg/kg and 40 mg/kg G. elegans alkaloids could significantly promote its growth performance, lipids and amino acids deposition, immune ability and resistance to Aeromonas hydrophila.

Regulation of Amino Acids in Muscle and Blood from Patients with Pancreatic Cancer‐ Induced Cachexia

Cachexia, or weight loss, is a profound side effect of cancer. Patients that suffer from cachexia have poor treatment tolerance, poor post‐surgical outcomes, poor survival, and poor quality of life. Despite decades of research, we lack a pharmacological intervention to treat cachexia, as mechanisms driving cachexia remain incompletely understood. Further, while the significance of cancer cachexia is clear, this syndrome remains poorly recognized, and a biomarker of cancer cachexia would be a valuable tool to improve the recognition of this syndrome. Because cachexia is ultimately a metabolic syndrome, we hypothesized that a metabolomics approach could identify new potential mechanisms of cachexia while also identifying potential biomarkers. Using a targeted mass spectrometry approach, we sought to distinguish cachectic pancreatic cancer patients from those without cancer or weight stable pancreatic cancer patients. Surprisingly, amino acid content of muscle from both cachectic and weight stable cancer patients was pronouncedly decreased compared to control patients. Similarly, plasma amino acid content was also generally decreased in both weight stable and cachectic cancer patients. Only differential levels of gamma‐amino‐N‐butryic acid (GABA) distinguished cachectic cancer patients from weight stable cancer patients and controls. In summary, the majority of changes we detected were specific to pancreatic cancer rather than cachexia, emphasizing the need to include cancer patients with and without cachexia in the study design.Support or Funding InformationSupport was provided through a Pilot and Feasibility Grant from the Mayo Clinic Metabolomics Resource Core through grant number U24DK100469 from the National Institute of Diabetes and Digestive and Kidney Diseases. Additional funding was provided by NIH R01CA180057 (DCG) and American Cancer Society Postdoctoral Fellowship PF‐15‐156‐01‐CSM (EET).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

(-)-Hydroxycitric Acid Nourishes Protein Synthesis via Altering Metabolic Directions of Amino Acids in Male Rats.

(-)-Hydroxycitric acid (HCA), a major active ingredient of Garcinia Cambogia extracts, had shown to suppress body weight gain and fat accumulation in animals and humans. While, the underlying mechanism of (-)-HCA has not fully understood. Thus, this study was aimed to investigate the effects of long-term supplement with (-)-HCA on body weight gain and variances of amino acid content in rats. Results showed that (-)-HCA treatment reduced body weight gain and increased feed conversion ratio in rats. The content of hepatic glycogen, muscle glycogen, and serum T4 , T3 , insulin, and Leptin were increased in (-)-HCA treatment groups. Protein content in liver and muscle were significantly increased in (-)-HCA treatment groups. Amino acid profile analysis indicated that most of amino acid contents in serum and liver, especially aromatic amino acid and branched amino acid, were higher in (-)-HCA treatment groups. However, most of the amino acid contents in muscle, especially aromatic amino acid and branched amino acid, were reduced in (-)-HCA treatment groups. These results indicated that (-)-HCA treatment could reduce body weight gain through promoting energy expenditure via regulation of thyroid hormone levels. In addition, (-)-HCA treatment could promote protein synthesis by altering the metabolic directions of amino acids. Copyright © 2016 John Wiley & Sons, Ltd.

Dietary arginine requirement of juvenile swimming crab,Portunus trituberculatus

An 8-week feeding trial was conducted to determine the optimal dietary arginine requirement for juvenile swimming crab Portunus trituberculatus. Six isonitrogenous and isolipidic experimental diets were formulated to contain graded arginine levels which ranged from 15.9 to 33.0 g kg−1. Each diet was randomly assigned to triplicate groups of 60 juvenile swimming crabs (4.72 ± 0.12 g). The results indicated that dietary arginine had significant effects on weight gain (WG), specific growth rate (SGR), protein productive value, feed efficiency and protein efficiency ratio. Weight gain and SGR significantly increased with the dietary arginine increasing from 15.9 to 27.4 g kg−1, while with the further increasing from 27.4 to 33.0 g kg−1, WG and SGR did not increase significantly. Maximum arginine, proline and total essential amino acid contents in muscle were observed in 27.4 g kg−1 group diet. The swimming crab fed the diet with lower dietary arginine level showed higher AST and lower ALT in the serum. Crab fed with the lower dietary arginine level had significantly lower ALT in the serum than the other groups. Haemolymph indexes were significantly affected by the dietary arginine level except for the cholesterol concentration, and the highest values were all found in 27.4 g kg−1 group diet. The two slope broken-line model using SGR showed that the optimal dietary arginine requirement was 27.7 g kg−1 of the dry matter (56.0 g kg−1 dietary protein) for juvenile swimming crab.

Dietary threonine requirement of juvenile large yellow croaker,Larmichthys crocea

A feeding trial was conducted to determine the dietary threonine requirement of juvenile large yellow croaker (Larmichthys crocea). Six diets were formulated containing 45% crude protein with six graded levels of threonine (0.71–2.46% in about 0.35% increment). Each diet was randomly assigned to triplicate groups of 60 juvenile fish (initial body weight 6.00 ± 0.10 g). Fish were fed twice daily (05:00 and 16:30) to apparent satiation for 8 weeks. The result indicated that significant difference was observed in the weight gain among all treatments. Specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and nitrogen retention (NR) increased with increasing levels of threonine up to 1.75% diet (P < 0.05), and thereafter, declined. No significant differences in body dry matter, crude protein, crude lipid or ash content were found among dietary treatments. Theronine contents of fish muscle were significantly affected by dietary threonine levels (P < 0.05). Fish fed the diet with 0.71% threonine showed the lowest threonine content (2.94%) in fish muscle, while fish fed the diet with 1.75% threonine had the highest value (3.16%). Other essential amino acid contents of muscle were not significantly different among the dietary treatments. On the basis of SGR, FE or NR, the optimum dietary threonine requirements of juvenile L. crocea were estimated to be 1.86% of diet (4.13% of dietary protein), 1.90% of diet (4.22% of dietary protein) and 2.06% of diet (4.58% of dietary protein), respectively, using second-order polynomial regression analysis.

Dietary arginine requirement of juvenile cobia (Rachycentron canadum)

A 9-week feeding trial was conducted to estimate the dietary requirement of arginine in juvenile cobia in indoor flow-through and aerated aquaria. Six isonitrogenous and isoenergetic practical diets were formulated to contain graded levels of arginine ranging from 1.76% to 3.75% (dry weight) at about 0.4% increments replaced by equal proportions of glycine. Survival was not significantly different among dietary treatments. Specific growth rate (SGR) and feed efficiency ratio (FER) increased with increasing dietary arginine up to the 2.96% diet (P < 0.05), and thereafter declined. The whole body crude protein content was significantly affected by dietary arginine (P < 0.05), while moisture, crude lipid and ash showed no significant differences among dietary treatments. The essential amino acid contents of muscle were not significantly affected by dietary arginine. The serum nitric oxide synthase activities in fish fed diets with arginine from 2.18% to 3.75% were significantly higher than activities in fish fed the diet with 1.76% arginine (P < 0.05). On the basis of SGR and FER, the optimal dietary arginine requirements of juvenile cobia were estimated to be 2.85% of the diet (6.20% of dietary protein) and 2.82% of the diet (6.13% of dietary protein), respectively, using second-order polynomial regression analysis.

Branchial and intestinal osmoregulatory acclimation in the four-eyed sleeper, Bostrychus sinensis (Lacepède), exposed to seawater

Bostrychus sinensis is a facultative air breather that inhabits waters of a wide range of salinities. This study aimed to elucidate whether branchial and intestinal osmoregulatory acclimation occurred in B. sinensis transferred from 5‰ water through a progressive increase in salinities to seawater. Our results indicate that B. sinensis acted as a hyperosmotic regulator in 5‰ water, but exhibited hypoosmotic hypoionic regulation in seawater. During short- (1 day) and medium- (10 days) term acclimation to seawater, there were only minor perturbations in plasma osmolality and [Na+], which returned to control levels after 45 days of exposure to seawater. Branchial Na+/K+-ATPase activity was unaffected by 1, 10 or 45 days of exposure to seawater. However, prolonged (45 days) acclimation to seawater led to a significant increase in Na+/K+-ATPase α-subunit protein abundance. Taken together, these results indicate that there could be changes in the expression of Na+/K+-ATPase isoforms and/or post-translational modification of Na+/K+-ATPase in the gills of fish exposed to seawater. Immunofluorescence microscopy revealed that acclimation to seawater for 10 days only resulted in no change in branchial Na+/K+-ATPase protein expression, but there were increases in protein expression of cystic fibrosis transmembrane regulator (CFTR)-like chloride channel and Na+:K+:2Cl− cotransporter (NKCC; probably NKCC1). Indeed, NKCC was undetectable in gills of fish kept in 5‰ water by Western blotting, but it became weakly detectable in fish exposed to seawater for 10 days and prominently expressed in fish exposed to seawater for 45 days. Therefore, our results indicate that branchial CFTR-like chloride channel and NKCC1 were the determining factors in the transition between hyperosmotic regulation and hypoosmotic hypoionic regulation in B. sinensis. Furthermore, the intestine of B. sinensis also served as an important osmoregulatory organ, since there were significant increases in both the activity and protein abundance of intestinal Na+/K+-ATPase in fish acclimated to seawater for 45 days. The effectiveness of branchial and intestinal osmoregulatory acclimation in B. sinensis during seawater acclimation led to only a minor increase in plasma osmolality, and thus resulted in relatively unchanged free amino acid contents in muscle and liver.

Seven days of oral taurine supplementation does not increase muscle taurine content or alter substrate metabolism during prolonged exercise in humans

This study examined 1) the plasma taurine response to acute oral taurine supplementation (T), and 2) the effects of 7 days of T on muscle amino acid content and substrate metabolism during 2 h of cycling at approximately 60% peak oxygen consumption (VO2peak). In the first part of the study, after an overnight fast, 7 volunteers (28+/-3 yr, 184+/-2 cm, 88.0+/-6.6 kg) ingested 1.66 g oral taurine doses with breakfast (8 AM) and lunch (12 noon), and blood samples were taken throughout the day. In the second part of the study, eight men (22+/-1 yr, 181+/-1 cm, 80.9+/-3.8 kg, 4.21+/-0.16 l/min VO2peak) cycled for 2 h after 7 days of placebo (P) ingestion (6 g glucose/day) and again following 7 days of T (5 g/day). In the first part of the study, plasma taurine was 64+/-4 microM before T and rose rapidly to 778+/-139 microM by 10 AM and remained elevated at noon (359+/-56 microM). Plasma taurine reached 973+/-181 microM at 1 PM and was 161+/-31 microM at 4 PM. In the second part of the study, seven days of T had no effect on muscle taurine content (mmol/kg dry muscle) at rest (P, 44+/-15 vs. T, 42+/-15) or after exercise (P, 43+/-12 vs. T, 43+/-11). There was no difference in muscle glycogen or other muscle metabolites between conditions, but there were notable interaction effects for muscle valine, isoleucine, leucine, cystine, glutamate, alanine, and arginine amino acid content following exercise after T. These data indicate that 1) acute T produces a 13-fold increase in plasma taurine concentration; 2) despite the ability to significantly elevate plasma taurine for extended periods throughout the day, 7 days of T does not alter skeletal muscle taurine content or carbohydrate and fat oxidation during exercise; and 3) T appears to have some impact on muscle amino acid response to exercise.

Dietary lysine requirement of juvenile Japanese seabass, Lateolabrax japonicus

A feeding experiment was conducted to estimate the quantitative requirement of lysine in juvenile Japanese seabass by feeding six isonitrogenous and isoenergetic practical diets containing six levels of lysine ranging from 1.28% to 4.25% (dry weight) at about 0.6% increment (diets 1–6). Equal amino acid nitrogen was maintained by replacing lysine with glutamic acid. Triplicate groups of 20 fish (initial weight 5.50 ± 1.63 g) were fed to apparent satiation by hand twice daily for 10 weeks in floating sea cages. The water temperature ranged from 27 to 30 °C, the salinity from 25‰ to 28‰ and the dissolved oxygen content was approximately 7 mg l − 1 during the experimental period. Fish fed diets with lysine from 1.28% to 4.25% (diets 1–6) all showed high survival (above 95%) and no significant differences were observed. Final weight (FW) and specific growth rate (SGR) increased with increasing dietary lysine level up to 2.46%, and thereafter, remained nearly the same. Both feed efficiency ratio (FER) and protein efficiency ratio (PER) in fish fed diets with lysine from 2.46% to 3.66% (diets 3–5) were significantly higher than those in fish fed diets with lysine of 1.28%, 1.86% and 4.25% ( P < 0.01). The whole body crude protein and crude lipid contents were significantly affected ( P < 0.01) by dietary lysine level, while moisture and ash showed no significant differences. The whole body protein content was positively correlated with dietary lysine levels, while lipid content was negatively correlated with it. Lysine contents of fish muscle were significantly affected by dietary lysine levels ( P < 0.05). Fish fed the diet with 1.28% lysine showed the lowest lysine content (7.61%) in fish muscle, while fish fed the diet with 3.66% lysine had the highest value (7.83%). Other essential amino acid contents of muscle were not significantly different among the dietary treatments. Broken-line analysis on the basis of SGR, FER and PER showed that dietary lysine requirements of juvenile Japanese seabass were 2.49 ± 0.05%, 2.61 ± 0.16% and 2.60 ± 0.13% dry diet (5.80 ± 0.12%, 6.07 ± 0.37% and 6.05 ± 0.30% dietary protein), respectively.

Free Amino Acid Pools in the Spontaneously Hypertensive Rat: A Longitudinal Study

To investigate abnormalities of metabolism in spontaneously hypertensive rats (SHR) that might be related to the pathogenesis of hypertension, we measured concentrations of free amino acids in plasma and in homogenates of skeletal muscle from SHR and age-matched normotensive Wistar-Kyoto (WKY) rats. These pools were evaluated in rats aged 3.5, 6, 8 and 28 wk, corresponding to time points before, during and after onset of hypertension. Amino acid content of aortic tissue also was examined at 3.5 and 6 wk. In plasma, amino acid concentrations were relatively unchanged throughout the study. Free amino acid content of muscle, on the other hand, decreased markedly with age in both strains. The most consistent and quantitatively important difference between strains was the much smaller muscle pool of lysine in SHR at 3.5, 6 and 8 wk of age compared with WKY controls. The arginine pool was also smaller in SHR but only at 3.5 and 6 wk. Other urea cycle amino acids were also lower in muscle of SHR at 3.5 wk. These alterations in the muscle amino acid pool were mirrored in plasma and were also found in aortic tissue. Glutamine was higher in muscle and plasma of SHR at 6 wk and thereafter. At 28 wk, however, many amino acids, including the branched-chain amino acids and tyrosine and glutamine, were present at higher concentrations in muscle and plasma of SHR than in those of WKY rats. These differences, because they occur most strikingly in SHR during the prehypertensive state, may be related to the development of hypertension.

Influence of exercise on free amino acid concentrations in rat tissues

Levels of free amino acids in muscle, liver, and plasma were measured in rats that had either swum (1 or 2 h) or run (until exhausted). Exercise lowered alanine levels in all three tissues except for liver of exhausted rats. Exercise decreased the plasma levels of the acidic amino acids and their amides. Glutamate and glutamine levels were depressed in muscle, and the glutamine level was lowered in liver by exercise. Aspartate concentration was lowered by exercise in liver but elevated in muscle. The branched-chain amino acids were generally elevated by exercise as were tyrosine, phenylalanine, methionine, and lysine. Plasma 3-methylhistidine concentration was also elevated by an exercise bout. The changes observed in the amino acid contents of muscle, liver, and plasma are consistent with the increase in protein degradation during exercise that we previously reported. The lowered levels of some amino acids (e.g., alanine, glutamine, glutamate) seem to suggest that amino acid catabolism and/or gluconeogenesis is increased by exercise.

Composition of Poultry Meat as Affected by Nutritional Factors

In discussing the present subject it is first necessary to define the term “poultry meat”. Poultry, unlike most other meat, is usually sold as a complete carcass, or as portions with intact skin. The poultry industry is therefore concerned more with the composition of the entire carcass in contrast to the situation with swine and beef where carcasses are cut in an entirely different manner and often sold in a processed form.With the exception of some of the visceral organs, the vitamin and mineral content of poultry meat is not influenced by composition changes within conventional diets. We are thus primarily involved with the effect of diet on the protein and fat content of the carcass. Since the amino acid content of muscle is genetically controlled, we are concerned only with the effect of nutrition on the quantity of carcass protein deposition. The composition of carcass fat, however, can .

Amino acid content of muscle and plasma with altered pH

The free amino acid contents of plasma and skeletal muscle were determined in rats with K+-deficiency, acute respiratory acidosis or acute respiratory alkalosis. K+-deficiency caused a reduction in intracellular pH (pHi) and an elevation of extracellular pH (pHe). The acute respiratory acidosis reduced skeletal muscle pH1 to the same extent K+-deficiency did; the respiratory alkalosis imposed elevated pHe to a level comparable with K+-deficiency. This made it possible to determine whether or not altered pH1 or pHe might directly influence the movement of amino acids into (or out of) skeletal muscle cells. Low-K+ muscle contained increased amounts of basic amino acids, primarily lysine. These increases accounted for about 30 per cent of the alkali metal cation deficit found in K+-deficient muscle. Aside from changes in basic amino acids, low-K+ skeletal muscle had increased amounts of threonine, serine, glutamine and citrulline; there were decreased concentrations of isoleucine plus leucine, valine, alanine and aspartic acid. No comparable pattern of amino acid changes were observed in normal rats with comparably reduced pH1 or elevated pHe induced by changing pCO2. These findings indicate that altered pHi or pHe have no direct influence on free amino acid movements across rat skeletal muscle cells in vivo. The free amino acid contents of plasma and skeletal muscle were determined in rats with K+-deficiency, acute respiratory acidosis or acute respiratory alkalosis. K+-deficiency caused a reduction in intracellular pH (pHi) and an elevation of extracellular pH (pHe). The acute respiratory acidosis reduced skeletal muscle pH1 to the same extent K+-deficiency did; the respiratory alkalosis imposed elevated pHe to a level comparable with K+-deficiency. This made it possible to determine whether or not altered pH1 or pHe might directly influence the movement of amino acids into (or out of) skeletal muscle cells. Low-K+ muscle contained increased amounts of basic amino acids, primarily lysine. These increases accounted for about 30 per cent of the alkali metal cation deficit found in K+-deficient muscle. Aside from changes in basic amino acids, low-K+ skeletal muscle had increased amounts of threonine, serine, glutamine and citrulline; there were decreased concentrations of isoleucine plus leucine, valine, alanine and aspartic acid. No comparable pattern of amino acid changes were observed in normal rats with comparably reduced pH1 or elevated pHe induced by changing pCO2. These findings indicate that altered pHi or pHe have no direct influence on free amino acid movements across rat skeletal muscle cells in vivo.

Amino acid content of muscle and plasma with altered pH

Amino acid content of muscle and plasma with altered pH