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PubMed1976

Responses of laying hens to a low-protein diet supplemented with essential amino acids, L-glutamic acid and/or intact protein.

1. Three sequential experiments, each lasting 8 weeks, were carried out on 576 singly-caged light hybrids. 2. In experiment 1 egg production was 84% using a conventional control diet, 61% with a basal low-protein diet, and 79% with the basal diet supplemented with 10 essential amino acids+L-glutamic acid (GA). 3. In experiment 2 supplementation with lysine and methionine (L+M) alone increased egg production significantly from 54 to 72%, compared with 83% with the conventional diet. 4. In experiment 3 egg production was 55% with the basal diet, 71% with the basal diet+L+M, 75% with a diet containing 141 g protein/kg+L+M, and 73% with the conventional diet. 5. In all three experiments supplementation with GA alone either gave no significant response or a depression in production. 6. Daily intakes of 1-24 g nitrogen as non-essential amino acids and 13 to 14 g total crude protein per bird resulted in good egg production. Supplementation of the basal diet with L+M resulted in a daily intake of 413 mg methionine/bird day which was considered adequate, and a daily intake of 710 mg lysine which was considered slightly inadequate.

Amino Acids, Essential↗
PubMed1978

Evaluation of essential amino acids and keto acids in uremic patients on low-protein diet.

The effectiveness of a mixture of five analogues of essential amino acids and the remaining four essential amino acids as compared to a preceeding treatment period of the nine essential amino acids was evaluated in 16 chronic uremic patients fed a low-protein diet. During amino acid analogues supplementation, there was a tendency for blood urea nitrogen to fall whereas creatinine did not change. Serum phosphate decreased in most patients, whereas serum calcium rose in some subjects. Protein metabolism, as judged by serum transferrin, Clq, C3c, total complement activity, was improved. Furthermore, the concentrations of prealbumin and retinol-binding protein, which are elevated in uremia, showed a further increase that might favor a vitamin A intoxication.

Adult↗
PubMed1981

Loss of amino acids during hemodialysis: effect of oral essential amino acid supplementation.

The aim of this study was to investigate the effect of amino acid (AA) supplementation on the loss and its time course of free AA, during hemodialysis. 2 uremic patients on regular hemodialysis received an increasing number of essential AA tablets during the dialysis. The loss and its time course of 6 essential and 7 nonessential free AA during dialysis was assayed in the dialysate. The loss per dialysis treatment of the administered essential AA increased almost proportionally with the doses of AA tablets. For the nonessential AA, no definite relationship between doses of AA tablets and losses was observed. At all levels of supplementation, methionine was retained best: 90% of the amount present in the tablets. Threonine showed the lowest retention: 15-55%.

Administration, Oral↗
PubMed2002

[Effect of hypoproteic diets enriched with essential and non-essential amino acids on the uninephrectomized rat ].

Hyperalimentation solutions, with low protein content but rich in amino acids, have been more frequently used as a dietary treatment for renal terminal patients, with the purpose to increase their survival. However, the literature in this respect is contradictory. Some authors justify the use of amino acids due to the fact that they seem to regenerate damaged tubular cells (glycine, for example). Other authors, on the contrary, do not agree with this position, since some amino acids, like L-Serine and Lysine, are nephrotoxic. In 1977, it was demostrated that Lysine and Arginine inhibited protein tubular reabsorption, inducing proteinuria, while Glycine, Alanine, Asparagine and Glutamic Acid did not. In order to clarify this issue, we carried out a controlled animal study using uninephrectomized rats fed during nine weeks, with different hypoproteinic diets (4% protein content), enriched individually with five different amino acids. The hypoproteinic diets were enriched with Lysine and Arginine (essential amino acids) and Proline, Glutamic Acid and Asparagine (non essential amino acids). Assays for serum biochemical markers and renal function were carried-out pre-nephrectomy, two weeks after nephrectomy (post-nephrectomy control) and nine weeks post-diet for all the animals, no matter the diet to which they were subjected, the serum biochemistry results showed that all the hypoproteinic diets, enriched with amino acids, affected the renal function. The nephrotoxicity of the tested amino acids, followed this decreasing order: Glutamic Acid > Proline > Lysine > Asparagine > Arginine. hypoproteinic diets enriched with Lysine, Asparagine and Arginine, produced glomerular hyperfiltration, without proteinuria. In summary, our results point towards the idea that, contrarily to what has been described in the literature by some authors: enrichment of hypoproteinic diets with certain amino acids does not seem to protect against progression of renal disease in physiologically compromised kidneys.

Amino Acids↗
PubMed1988

Estimation of the biological value of food proteins by a modified equation of the essential amino acid index and the chemical score.

A modified essential amino acid index equation incorporating a digestibility factor (MEAAI), and a chemical score index (CSI) were developed from the essential amino acid profile of 18 different food proteins hydrolysed by the combined but sequential action of papain and pronase E enzyme systems. The essential amino acid composition of whole egg was used as a reference standard. The following equations were proposed: log MEAAI = 1/8 log (100 a/ae X DFP/DFe) + log (100 b/be X DFP/DFe) + .... + log (100 h/he X DFP/DFe) where a-h are the respective values of each of the 8 essential amino acids in the sample; DFp is the digestibility factor for food protein sample; DFe is the digestibility factor for whole cooked egg; CSI = 100 a/ae, in which a is the value of the limiting amino acid in the sample, and ae is the corresponding value in whole egg. Both equations were used to calculate the biological value of different protein foodstuffs. There was a close agreement between values obtained using the equations and reported values for the same foodstuffs published in the literature. There was also a close correlation (r = 0.665) between data obtained using MEAAI and those obtained using CSI in estimating biological values, suggesting that either equation could be used reliably and solely to estimate protein biological value of foods.

Amino Acids↗
PubMed2003

Pollen feeding in the butterfly Heliconius charitonia: isotopic evidence for essential amino acid transfer from pollen to eggs.

Heliconius and Laparus butterflies exhibit a unique pollen-collecting behaviour that enhances lifespan and fecundity. The specific nutritional contribution of pollen, however, had not been previously demonstrated. We used stable isotope variation to trace the carbon flow into eggs from corn pollen provided experimentally to ovipositing female Heliconius charitonia, and to evaluate the use of isotopically contrasting nectar sugars in egg amino acids. The delta(13)C of individual amino acids from pollen, larval host plant and the eggs from experimental butterflies was measured with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), to evaluate amino acid transfer. The delta(13)C of egg essential amino acids indicated a transfer of essential amino acids from pollen to butterfly eggs. However, the delta(13)C of non-essential amino acids reflected the isotopic composition of the artificial nectar, indicating that H. charitonia synthesizes non-essential amino acids from dietary sugars. This, to our knowledge, is the first direct demonstration of amino acid transfer from pollen to butterfly eggs, and suggests that essential amino acids in particular are a key resource for extending lifespan and fecundity in Heliconius butterflies.

Amino Acids, Essential↗
PubMed2006

A set of amino acids found to occur more frequently in human and fly than in plant and yeast proteomes consists of non-essential amino acids.

We investigated the hypothesis that essential amino acids are being replaced in proteins by non-essential amino acids. We compared the amino acid composition in human, worm and fly proteomes, organisms that cannot synthesize all amino acids, with the amino acids of the proteomes of plant, bakers yeast and budding yeast, which are capable of synthesizing them. The analysis covered 460,737 proteins (212,197,907 amino acids). The data suggest a bias towards the usage of non-essential amino acids (mostly the set GAPQC) by metazoan organisms, except for the worm, a Pseudocoelomata. Our results support the hypothesis that non-essential amino acids have been substituting essential ones in the Coelomata.

Amino Acids↗
PubMed2003

Threonine deprivation rapidly activates the system A amino acid transporter in primary cultures of rat neurons from the essential amino acid sensor in the anterior piriform cortex.

Omnivores show recognition of essential (indispensable) amino acid deficiency by changing their feeding behavior within 20 min, yet the cellular mechanisms of amino acid sensation in eukaryotes are poorly understood. The anterior piriform cortex (APC) of the brain in rats or its analog in birds likely houses the in vivo amino acid chemosensor. Because amino acid transporters adapt rapidly to essential amino acid deficiency in several cell models, we hypothesized that activation of electrogenic amino acid transport in APC neurons might contribute to the function of the amino acid sensor. We evaluated transport systems in primary cultures of neurons from the APC, hippocampus and cerebellum, or glia, incubated in complete or threonine-devoid (deficient) medium. After 10 min in deficient medium, uptake of threonine or a system A-selective substrate, methyl amino-isobutyric acid, was increased 60% in APC neurons only (P < 0.05). These results demonstrated upregulation of system A, an electrogenic amino acid-sodium symporter. This depletion-induced activation required sodium, intact intracellular trafficking, and phosphorylation of signal transduction-related kinases. Efflux studies showed that other transporter types were functional in the APC; they appeared to be altered dynamically in threonine-deficient cells in response to rapid increases in system A activity. The present data provided support for the chemical sensitivity of the APC and its role as the brain area housing the indispensable amino acid chemosensor. They also showed a region-specific, phosphorylation-dependent activation of the system A transporter in the brain in response to threonine deficiency.

Amino Acid Transport System A↗
PubMed1975

Effects of essential amino acids on central neurons.

Effects of eleven essential amino acids ejected by means of electrophoresis through five barrel glass microelectrodes on the frequency of extracellularly recorded action potentials of brain cells were determined. Data were collected on 129 cells from four different parts of the brains of 22 female hooded rats anesthetized with a mixture of chloralose and urethan. Eleven cells were tested in the cerebral cortex, 57 in the thalamus, 33 in the zona incerta, and 28 in the lateral hypothalamus. Of the eleven amino acids tested, cells of the zona incerta and lateral hypothalamus appear to be the most responsive and increases in discharge frequency were observed for all the amino acids except lysine and cystine. Cystine seems to be unusual in that it is the only amino acid tested which produces a decrease in the spontaneous discharge frequency. Cells of the cerebral cortex were not considered responsive in terms of the criteria of this study and displayed relatively high thresholds to all the essential amino acids. These results indicate some differential sensitivity of certain cells of the brain to essential amino acids which might be related to the centrally mediated anorexia which develops when rats are fed disproportionate amounts of these same amino acids in the diet.

Amino Acids↗
PubMed1990

[Treatment of chronic renal failure: effects of a supplemented diet with essential amino acids].

We evaluated the results of essential amino acids supplementation added to a protein restricted diet (0.6 g/kg/day) in patients with advanced renal failure (creatinine clearance under 20 ml/min). A diet containing food with high biologic value was used as control. Diets were tested during 7 months. Anthropometric and nutritional (serum albumin and transferrin) values were normal in both groups both at the beginning and at the end of the treatment period. A slight increase in weight in the natural diet group and in serum phosphorus level in the amino acid supplemented group was observed. Two patients in each group required chronic dialysis, renal function remaining stable in the rest. We conclude that both forms of diet supplementation were effective in preserving nutritional status possibly in delaying deterioration of renal function in patients with advanced renal failure.

Amino Acids, Essential↗
PubMed1975

Plasma amino acids and protein levels in chronic renal failure and changes caused by oral supplements of essential amino acids.

1. Plasma amino acids and six proteins have been measured in patients with chronic renal failure receiving low protein diets before and after oral supplementation with essential amino acids. 2. All the patients on low protein diets had a lower percentage of essential amino acids in their plasma than normal subjects but after supplementation, plasma levels increased significantly with minimal increase in non-essential amino acids or urea nitrogen. 3. Mean levels of plasma transferrin, complement C3 and globulin Gc were lower and plasma prealbumin higher in patients than in normal subjects. Plasma complement C4 and albumin were not different from normal. 4. Seven out of nine patients who tolerated the supplementation showed a significant increase in plasma transferrin, prealbumin and complement C3 but not in complement C4, globulin Gc or albumin. 5. Correlations between the percentage of essential amino acids and each of plasma transferrin, prealbumin and complement C3 and also between several of the plasma proteins further substantiate their value in the assessment of dietary intake in chronic renal failure. 6. The value of amino acid supplementation on low protein diets in chronic renal failure is discussed in relation to these observations.

Adult↗
PubMed1977

Influence of essential amino acids and keto acids on protein metabolism and the anaemia of patients on chronic intermittent haemodialysis.

Ten patients were treated with 10 g essential amino acids per day orally; 9 patients received 9.5 g of a mixture of essential amino acids (Lys, Thr, Try, His, Tyr) and ketoanalogues of Ile, Leu, Phe, Val, Met per day and a control group of 11 patients received no supplementation. All patients were on a liberal food intake amounting to 1g protein/kg body weight and 31 kcal/kg body weight daily. Before and three months after the beginning of supplementation the following parameters were measured: serum concentrations of albumin, transferrin, urea, creatinine, blood haemoglobin content and haematocrit, activities of the enzymes delta-aminolevulinic acid dehydrase and porpho-bilinogen desaminase, and globin synthesis in peripheral red blood cells. After treatment with either essential amino acids or keto acids a significant stimulation of globin synthesis occurred. None of the other parameters was altered. It is concluded that in well-nourished patients supplements of essential amino acids or keto acids are ineffective.

Amino Acids, Essential↗
PubMedDate not supplied

Evidence for an anabolic action of essential amino acid analogues in uremia and starvation.

Nitrogen-free analogues of essential amino acids, when administered with those essential amino acids for which analogues are ineffective or unavailable, exert three actions that may be beneficial in protein-deficient or protein-intolerant subjects. First, they bring about an increase in the concentrations of essential amino acids in the blood at the expense of the concentrations of certain non-essential amino acids, notably alanine and glutamine. This effect is most readily demonstrated in children with congenital defects of the urea cycle enzymes, but can also be seen during daily therapy of adults with portal-systemic encephalopathy. Second, these compounds promote nitrogen balance through their suppressive effect on urea synthesis (an effect not attributable to re-utilization of ammonia derived from urease action in the gut). This action is demonstrable in obese subjects who are already conserving nitrogen maximally at the end of a prolonged fast and can also be shown in the first week of fasting when the branched-chain keto acids alone are administered. In both situations, improved nitrogen conservation persists long after the analogues are metabolized, suggesting enzyme adaptations. In chronic uremics, nitrogen balance can be maintained in some (but not all) patients on very low nitrogen intakes. Third, these mixtures may delay or reverse the progressive decline in glomerular filtration rate characteristic of chronic renal failure in some cases: thus, for example, 5 of 6 patients taken off chronic dialysis have maintained lower serum urea concentrations without evidence of protein malnutrition for periods of 2-24 months.

Amino Acids↗
PubMed2001

An in vivo study of ovine placental transport of essential amino acids.

Under normal physiological conditions, essential amino acids (EA) are transported from mother to fetus at different rates. The mechanisms underlying these differences include the expression of several amino acid transport systems in the placenta and the regulation of EA concentrations in maternal and fetal plasma. To study the relation of EA transplacental flux to maternal plasma concentration, isotopes of EA were injected into the circulation of pregnant ewes. Measurements of concentration and molar enrichment in maternal and fetal plasma and of umbilical plasma flow were used to calculate the ratio of transplacental pulse flux to maternal concentration (clearance) for each EA. Five EA (Met, Phe, Leu, Ile, and Val) had relatively high and similar clearances and were followed, in order of decreasing clearance, by Trp, Thr, His, and Lys. The five high-clearance EA showed strong correlation (r(2) = 0.98) between the pulse flux and maternal concentration. The study suggests that five of the nine EA have similar affinity for a rate-limiting placental transport system that mediates rapid flux from mother to fetus, and that differences in transport rates within this group of EA are determined primarily by differences in maternal plasma concentration.

Amino Acids↗
PubMed1989

Effect of some essential amino acid deficiency in the medium on the action of insulin on primary cultured hepatocytes of rats. Hepatocytes do not respond to insulin in some essential amino acid-deficient medium.

1. The effects of insulin, glucagon and dexamethasone on the amino acid consumption by primary cultures of rat hepatocytes were studied in a medium containing all essential amino acids or in those deficient in some essential or nonessential amino acids. 2. The cells which were cultured in a medium containing all the essential amino acids responded to insulin by enhancing the consumption of amino acids and augmenting protein synthesis. 3. However, the cells did not respond to insulin significantly when they were cultured in a medium deficient in lysine or some other essential amino acids. 4. The results suggest that some essential amino acid deficiency impairs the transmission of the signal of insulin to the site of the metabolic changes induced by the hormone.

Amino Acids↗