scholarly journals Dietary amino acids: effect of depletion and recovery on synthesis in vitro in rat skeletal muscle and liver

1974 ◽  
Vol 31 (1) ◽  
pp. 67-76 ◽  
Author(s):  
P. T. Omstedt ◽  
Alexandra Von Der Decken
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Energy Levels ◽  
Wheat Gluten ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Amino Acid Mixtures ◽  
Wet Weight ◽  
Ribosomal Activity

1. Rats were given diets containing 200 g/kg of a complete or incomplete amino acid mixture or of high- or low-quality proteins. After 6 d the amino acid-incorporating activity of ribosomes from skeletal muscle and liver was studied.2. The level of isotope incorporation relative to ribosomal RNA was similar for casein supplemented with methionine and for a complete amino acid mixture with the composition of whole-egg protein. Per wet weight of tissue there was a significant decrease after feeding with the complete amino acid mixture.3. There was a significant decrease in activity after feeding with amino acid mixtures deficient in lysine, methionine or tryptophan. In skeletal muscle, but not in liver, the ribosomal activity was less than that obtained with wheat gluten. Activity per wet weight of both tissues was less than that obtained with wheat gluten.4. Refeeding with methionine for 1 d resulted in complete restoration of ribosomal activity and activity per wet weight in skeletal muscle.5. After lysine deficiency, protein synthesis per unit wet weight of both tissues and ribosomal activity in liver were not restored after 2 d of refeeding. Recovery of ribosomal activity in skeletal muscle was complete after 1 d.6. Rats receiving the 200 g casein/kg diet supplemented with methionine at daily energy levels of 263, 176, 141 and 106 KJ (62.6, 42.1, 33.7 and 25.3 kcal) showed no changes in ribosomal activity, but there was a significant decrease in activity per wet weight when 106 KJ were given.

scholarly journals Effect of co-ingestion of amino acids with rice on glycaemic and insulinaemic response

2015 ◽  
Vol 114 (11) ◽  
pp. 1845-1851 ◽  
Author(s):  
Yean Yean Soong ◽  
Joseph Lim ◽  
Lijuan Sun ◽  
Christiani Jeyakumar Henry
Keyword(s):  
Amino Acids ◽  
Blood Glucose ◽  
Amino Acid ◽  
Glycaemic Index ◽  
Amino Acid Mixture ◽  
Postprandial Blood Glucose ◽  
Acid Mixture ◽  
White Rice ◽  
Amino Acid Mixtures

AbstractConsumption of high glycaemic index (GI) and glycaemic response (GR) food such as white rice has been implicated in the development of type 2 diabetes. Previous studies have reported the ability of individual amino acids to reduce GR of carbohydrate-rich foods. Because of the bitter flavour of amino acids, they have rarely been used to reduce GR. We now report the use of a palatable, preformed amino acid mixture in the form of essence of chicken. In all, sixteen healthy male Chinese were served 68 or 136 ml amino acid mixture together with rice, or 15 or 30 min before consumption of white rice. Postprandial blood glucose and plasma insulin concentrations were measured at fasting and every 15 min after consumption of the meal until 60 min after the consumption of the white rice. Subsequent blood samples were taken at 30-min intervals until 210 min. The co-ingestion of 68 ml of amino acid mixture with white rice produced the best results in reducing the peak blood glucose and GR of white rice without increasing the insulinaemic response. It is postulated that amino acid mixtures prime β-cell insulin secretion and peripheral tissue uptake of glucose. The use of ready-to-drink amino acid mixtures may be a useful strategy for lowering the high-GI rice diets consumed in Asia.

Endotoxemia reduces skeletal muscle protein synthesis in neonates

2002 ◽  
Vol 283 (5) ◽  
pp. E909-E916 ◽  
Author(s):  
Renan A. Orellana ◽  
Pamela M. J. O'Connor ◽  
Hanh V. Nguyen ◽  
Jill A. Bush ◽  
Agus Suryawan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Interleukin 1 ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Skeletal Muscle Protein ◽  
Skeletal Muscle Protein Synthesis

Protein synthesis in skeletal muscle is reduced by as much as 50% as early as 4 h after a septic challenge in adults. However, the effect of sepsis on muscle protein synthesis has not been determined in neonates, a highly anabolic population whose muscle protein synthesis rates are elevated and uniquely sensitive to insulin and amino acid stimulation. Neonatal piglets ( n = 10/group) were infused for 8 h with endotoxin [lipopolysaccharide (LPS), 0 and 10 μg · kg−1 · h−1]. Plasma amino acid and glucose concentrations were kept at the fed level by infusion of dextrose and a balanced amino acid mixture. Fractional protein synthesis rates were determined by use of a flooding dose of [3H]phenylalanine. LPS infusion produced a septic-like state, as indicated by an early and sustained elevation in body temperature, heart rate, and plasma tumor necrosis factor-α, interleukin-1, cortisol, and lactate concentrations. Plasma levels of insulin increased, whereas glucose and amino acids decreased, suggesting the absence of insulin resistance. LPS significantly reduced protein synthesis in longissimus dorsi muscle by only 11% and in gastrocnemius by only 15%, but it had no significant effect in masseter and cardiac muscles. LPS increased protein synthesis in the liver (22%), spleen (28%), kidney (53%), jejunum (19%), diaphragm (21%), lung (50%), and skin (13%), but not in the stomach, pancreas, or brain. These findings suggest that, when substrate supply is maintained, skeletal muscle protein synthesis in neonates compared with adults is relatively resistant to the catabolic effects of sepsis.

scholarly journals Whole body and skeletal muscle glutamine metabolism in healthy subjects

2001 ◽  
Vol 280 (2) ◽  
pp. E323-E333 ◽  
Author(s):  
B. Mittendorfer ◽  
E. Volpi ◽  
R. R. Wolfe
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Healthy Subjects ◽  
Amino Acid Mixture ◽  
Glutamine Metabolism ◽  
Whole Body ◽  
Acid Mixture ◽  
Outward Transport ◽  
Glucose Ingestion ◽  
Glutamine Synthesis

We measured glutamine kinetics usingl-[5-15N]glutamine andl-[ ring-2H5]phenylalanine infusions in healthy subjects in the postabsorptive state and during ingestion of an amino acid mixture that included glutamine, alone or with additional glucose. Ingestion of the amino acid mixture increased arterial glutamine concentrations by ∼20% (not by 30%; P < 0.05), irrespective of the presence or absence of glucose. Muscle free glutamine concentrations remained unchanged during ingestion of amino acids alone but decreased from 21.0 ± 1.0 to 16.4 ± 1.6 mmol/l ( P < 0.05) during simultaneous ingestion of glucose due to a decrease in intramuscular release from protein breakdown and glutamine synthesis (0.82 ± 0.10 vs. 0.59 ± 0.06 μmol · 100 ml leg−1 · min−1; P < 0.05). In both protocols, muscle glutamine inward and outward transport and muscle glutamine utilization for protein synthesis increased during amino acid ingestion; leg glutamine net balance remained unchanged. In summary, ingestion of an amino acid mixture that includes glutamine increases glutamine availability and uptake by skeletal muscle in healthy subjects without causing an increase in the intramuscular free glutamine pool. Simultaneous ingestion of glucose diminishes the intramuscular glutamine concentration despite increased glutamine availability in the blood due to decreased glutamine production.

An amino acid mixture improves glucose tolerance and insulin signaling in Sprague-Dawley rats

2011 ◽  
Vol 300 (4) ◽  
pp. E752-E760 ◽  
Author(s):  
Jeffrey R. Bernard ◽  
Yi-Hung Liao ◽  
Daisuke Hara ◽  
Zhenping Ding ◽  
Chung-Yu Chen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Glucose ◽  
Amino Acid ◽  
Glucose Uptake ◽  
White Muscle ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Glucose Response ◽  
Skeletal Muscle Glucose Uptake ◽  
Fast Twitch

The aims of this investigation were to evaluate the effect of an amino acid supplement on the glucose response to an oral glucose challenge ( experiment 1) and to evaluate whether differences in blood glucose response were associated with increased skeletal muscle glucose uptake ( experimental 2). Experiment 1 rats were gavaged with either glucose (CHO), glucose plus an amino acid mixture (CHO-AA-1), glucose plus an amino acid mixture with increased leucine concentration (CHO-AA-2), or water (PLA). CHO-AA-1 and CHO-AA-2 had reduced blood glucose responses compared with CHO, with no difference in insulin among these treatments. Experiment 2 rats were gavaged with either CHO or CHO-AA-1. Fifteen minutes after gavage, a bolus containing 2-[3H]deoxyglucose and [U-14C]mannitol was infused via a tail vein. Blood glucose was significantly lower in CHO-AA-1 than in CHO, whereas insulin responses were similar. Muscle glucose uptake was higher in CHO-AA-1 compared with CHO in both fast-twitch red (8.36 ± 1.3 vs. 5.27 ± 0.7 μmol·g−1·h−1) and white muscle (1.85 ± 0.3 vs. 1.11 ± 0.2 μmol·g−1·h−1). There was no difference in Akt/PKB phosphorylation between treatment groups; however, the amino acid treatment resulted in increased AS160 phosphorylation in both muscle fiber types. Glycogen synthase phosphorylation was reduced in fast-twitch red muscle of CHO-AA-1 compared with CHO, whereas mTOR phosphorylation was increased. These differences were not noted in fast-twitch white muscle. These findings suggest that amino acid supplementation can improve glucose tolerance by increasing skeletal muscle glucose uptake and intracellular disposal through enhanced intracellular signaling.

scholarly journals Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness

2001 ◽  
Vol 179 (4) ◽  
pp. 356-360 ◽  
Author(s):  
S. F. B. McTavish ◽  
M. H. McPherson ◽  
C. J. Harmer ◽  
L. Clark ◽  
T. Sharp ◽  
...  
Keyword(s):  
Amino Acid ◽  
Healthy Volunteers ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Double Blind ◽  
Amino Acid Mixtures ◽  
Tyrosine Depletion ◽  
Dsm Iv ◽  
To Receive ◽  
The Brain

BackgroundIn rats, amino acid mixtures lacking tyrosine and its precursor phenylalanine decrease the release of dopamine produced by the psychostimulant drug amphetamine. Amphetamine has been proposed as a model for clinical mania.AimsTo assess whether dietary tyrosine depletion attenuates the psychostimulant effects of methamphetamine in healthy volunteers and diminishes the severity of mania in acutely ill patients.MethodSixteen healthy volunteers received a tyrosine-free amino acid mixture and a control mixture in a double-blind crossover design 4 h before methamphetamine (0.15 mg/kg). Twenty in-patients meeting DSM–IV criteria for mania were allocated blindly and randomly to receive either the tyrosine-free mixture or the control mixture.ResultsThe tyrosine-free mixture lowered both subjective and objective measures of the psychostimulant effects of methamphetamine. Ratings of mania were lower in the patients who received the tyrosine-free mixture.ConclusionsDecreased tyrosine availability to the brain attenuates pathological increases in dopamine neurotransmission following methamphetamine administration and putatively in mania.

scholarly journals The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase

1970 ◽  
Vol 120 (1) ◽  
pp. 205-214 ◽  
Author(s):  
A. R. Henderson
Keyword(s):  
Amino Acid ◽  
Rna Polymerase ◽  
Rat Liver ◽  
Acid Concentration ◽  
Polymerase Activity ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Amino Acid Mixtures ◽  
Rna Polymerase Activity ◽  
Tryptophan Concentration

1. The Widnell & Tata (1966) assay method for Mg2+-activated DNA-dependent RNA polymerase was used for initial-velocity determinations of rat liver nuclear RNA polymerase. One unit (U) of RNA polymerase was defined as that amount of enzyme required for 1 mmol of [3H]GMP incorporation/min at 37°C. 2. Colony fed rats were found to have a mean RNA polymerase activity of 65.9μU/mg of DNA and 18h-starved rats had a mean activity of 53.2μU/mg of DNA. Longer periods of starvation did not significantly decrease RNA polymerase activity further. 3. Rats that had been starved for 18h were used for all feeding experiments. Complete and tryptophan-deficient amino acid mixtures were given by stomach tube and the animals were killed 15–120min later. The response of RNA polymerase to the feeding with the complete amino acid mixture was rapid and almost linear over the first hour of feeding, resulting in a doubling of activity. The activity was still elevated above the starvation value at 120min after feeding. The tryptophan-deficient amino acid mixture produced a much less vigorous response about 45min after the feeding, and the activity had returned to the starvation value by 120min after the feeding. 4. The response of RNA polymerase to the feeding with the complete amino acid mixture was shown to occur within a period of less than 5min to about 10min after the feeding. 5. Pretreatment of the animals with puromycin or cycloheximide was found to abolish the 15min RNA polymerase response to the feeding with the complete amino acid mixture, but the activity of the controls was unaffected. 6. The characteristics of the RNA polymerase from 18h-starved animals and animals fed with the complete or incomplete amino acid mixtures for 1h were examined. The effects of Mg2+ ions, pH, actinomycin D and nucleoside triphosphate omissions were determined. The [Mg2+]– and pH–activity profiles of the RNA polymerase from the animal fed with the complete mixture appeared to differ from those of the enzyme from the other groups, but this difference is probably not significant. 7. [5-3H]Orotic acid incorporation by rat liver nuclei in vivo was shown to be affected by the amino acid mixtures in a similar manner to the RNA polymerase. 8. The tryptophan concentrations of plasma and liver were determined up to 120 min after feeding with the amino acid mixtures. Feeding with the complete mixture produced a rapid increase in free tryptophan concentrations in both plasma and liver, but feeding with the incomplete mixture did not alter the plasma concentration. The liver tryptophan concentration increased at about 45min after feeding with the tryptophan-deficient diet. 9. There was a good correlation between the liver tryptophan concentration and RNA polymerase activity in all groups of animals. 10. It was concluded that the rat liver nucleus responded to an increase in amino acid supply by increased synthesis of RNA as a result of synthesis of RNA polymerase de novo. The correlation of tryptophan concentration and RNA polymerase activity appears to reflect the general amino acid concentration required to support hepatic protein synthesis and to produce new RNA polymerase. This new polymerase appears to differ from the basal RNA polymerase by its rapid synthesis and destruction, which may be a means of regulating RNA synthesis by the amino acid concentration in the liver.

Evidence for Active Transport of the Dipeptide Carnosine (β-Alanyl-l-Histidine) by Hamster Jejunum in Vitro

1974 ◽  
Vol 46 (6) ◽  
pp. 693-705 ◽  
Author(s):  
D. M. Matthews ◽  
Jill M. Addison ◽  
D. Burston
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Active Transport ◽  
Amino Acid Mixture ◽  
Intestinal Wall ◽  
Free Form ◽  
Acid Mixture ◽  
Total Uptake ◽  
Hydrolysis Of

1. The characteristics of intestinal transport and hydrolysis of carnosine (β-alanyl-l-histidine) have been studied in rings of everted hamster jejunum in vitro. 2. During incubation with carnosine, large amounts of intact peptide appeared in the intestinal wall, accompanied by small amounts of the constituent amino acids in the free form. Although there was some extracellular hydrolysis, the free amino acids appearing in the intestinal wall were almost entirely derived from intracellular hydrolysis of the peptide. Incubation in l-alanyl-l-histidine resulted in uptake of the constituent amino acids in the free form without appearance of intact peptide in the intestinal wall. 3. Total uptake of β-alanine (both peptide-bound and free) and total uptake of histidine were greater from a low concentration (1 μmol/ml) of carnosine than uptake of these amino acids from the equivalent amino acid mixture. At a high concentration of carnosine (20 μmol/ml), total uptake of β-alanine was greater from the peptide than from the equivalent amino acid mixture but total uptake of histidine was less. At this concentration, total uptake of β-alanine plus total uptake of histidine from the peptide was approximately the same as from the amino acid mixture. 4. Uptake of carnosine by jejunal rings was the result of a saturable process (Kt 9·4 μmol/ml, Vmax. 2·7 μmol g−1 initial wet wt. min−1). Intact carnosine was concentrated in the intestinal wall, the concentration ratio between intracellular fluid and incubation medium being up to 3·4/1. Uptake of carnosine was reduced by anoxia, metabolic inhibitors and replacement of medium Na+. Na+-dependent active transport was shown to be involved in uptake of carnosine by hamster jejunum in vitro.

scholarly journals Jejunal absorption of an amino acid mixture simulating casein and an enzymic hydrolysate of casein prepared for oral administration to normal adults

1975 ◽  
Vol 33 (1) ◽  
pp. 95-100 ◽  
Author(s):  
D. B. A. Silk ◽  
M. L. Clark ◽  
T. C. Marrs ◽  
Jill M. Addison ◽  
D. Burston ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Oral Administration ◽  
Human Subjects ◽  
Amino Nitrogen ◽  
Casein Hydrolysate ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Amino Acid Mixtures ◽  
Percentage Absorption

1. An intestinal perfusion technique was used in six normal human subjects to study absorption of sixteen individual amino acids from an amino acid mixture simulating casein and from an enzymic hydrolysate of casein, prepared for oral administration to these subjects, which consisted of a mixture of oligopeptides and free amino acids.2. Total absorption of α-amino nitrogen was greater from the casein hydrolysate than from the amino acid mixture, and the considerable variation in percentage absorption of individual amino acids from the amino acid mixture was much reduced when the enzymic hydrolysate solution was perfused, as a number of amino acids which were poorly absorbed from the amino acid mixture were absorbed to a greater extent from the casein hydrolysate.3. These findings indicate that after extensive intestinal resections or in malabsorption there might be significant nutritional advantages in the administration of protein hydrolysates rather than amino acid mixtures.

scholarly journals Factors Influencing the Biosynthesis of the Tyrosine-rich Proteins of Wool

1974 ◽  
Vol 27 (1) ◽  
pp. 31 ◽  
Author(s):  
MJ Frenkel ◽  
JM Gillespie ◽  
PJ Reis
Keyword(s):  
Amino Acid ◽  
Acid Metabolism ◽  
Wheat Gluten ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Amino Acid Residues ◽  
Significant Reversal ◽  
Aromatic Amino Acid Metabolism ◽  
Tyrosine Content ◽  
Dietary Origin

The tyrosine content of wool can vary from about 2�3 to 4�4% of the amino acid residues. This variability, which can be attributed mostly to differences in the proportion of high-tyrosine proteins, appears to be partly of genetic and partly of dietary origin, for there are considerable differences in high-tyrosine protein content between the wools from different breeds of sheep and individual sheep of the same breed, and abomasal infusions of zein, maize gluten and wheat gluten strongly repress the synthesis of these proteins. Infusions of an amino acid mixture simulating the composition of zein produced a similar effect to that of zein. No significant reversal of the repression was produced by adding lysine, tryptophan or tyrosine to zein. It is suggested that these inhibitions may result from interference with aromatic amino acid metabolism.

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