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PubMed1993

An isotopic study of the effect of dietary carbohydrate on the metabolic fate of dietary leucine and phenylalanine.

The fate of dietary leucine and phenylalanine was studied in five healthy, young adult men, by using a dual, stable isotope-tracer infusion approach to estimate amino acid fluxes, splanchnic (Sp) uptake, and dietary of absorbed amino acid to the peripheral circulation. Subject received two, 4-h tracer infusions of [1-13C]leucine and [15N]phenylalanine infused through a feeding tube placed in the duodenum, and [5,5,5-2H3]leucine, [ring-2H5]phenylalanine, and [6,6-2H2]glucose infused simultaneously by vein. In one experiment subjects received an amino acid mixture (83 mg amino acid.kg-1.h-1) via the feeding tube and in the other experiment amino acids were supplied with carbohydrate (CHO) (167 mg.kg-1.h-1). Sp uptake of dietary leucine decreased with added dietary CHO (29% of ingested leucine for amino acids alone vs 20% with CHO; P < 0.05) but was not different for phenylalanine (P > 0.05). Addition of CHO decreased both release of leucine via protein breakdown and leucine oxidation and increased body leucine balance (P < 0.05).

Adult↗
PubMed2005

Transdermal delivery of amino acids and antioxidants enhance collagen synthesis: in vivo and in vitro studies.

One of the most visible changes associated with the aging process in humans relates to a progressive thinning of the skin. This results from a decline in both collagen and glycosaminoglycans, as well as from changes in their chemical structure and 3-dimentional organization. Transdermal administration of antioxidants, a -lipoic acid (LA) (0.5%) and proanthocyanidin PA) (0.3%) in a standard cosmetic vehicle base formulation supplemented with 2% benzyl alcohol as a penetration enhancer, a mixture of essential amino acids (0.2%), significantly enhanced collagen synthesis and deposition. The amino acid mixture was designed to mimic serum concentrations, with supplemental methionine added to provide additional sulfur. The histological appearance of the skin of mature female rats treated in this fashion reflected the increased deposition of collagen in the dermis as well as a thickened epidermal layer. The changes do not seem to be mediated by TGF- ss or PDGF, two growth factors known to stimulate collagen synthesis. At lower concentrations, a -lipoic acid did not affect cell proliferation but at higher doses, while it had an inhibitory effect on (3)H-thimidine uptake, it did enhance collagen production. Pronanthocyanidin did not affect cell proliferation but significantly increased collagen synthesis by cultured fibroblasts.

Administration, Cutaneous↗
PubMedDate not supplied

Effect of simultaneous ingestion of L-amino acids and whole protein on plasma amino acid and urea nitrogen concentrations in humans.

The effect of whole protein and L-amino acid ingestion on plasma amino acid (PAA) and urea nitrogen (UN) concentrations was investigated. Ten males ingested equivalent amounts of nitrogen as (trial 1) cottage cheese, (trial 2) an L-amino acid mixture, (trial 3) cottage cheese and L-amino acids. Mean changes in total PAA between trials 1 (342 mumol/liter) and 2 (719 mumol/liter) and trials 1 (342 mumol/liter) and 3 (981 mumol/liter) at 30 min and trials 1 (547 mumol/liter) and 3 (143 mumol/liter) at 150 min differed significantly. Mean changes in essential PAA between trials 1 (180 mumol/liter) and 2 (420 mumol/liter) and trials 1 (180 mumol/liter) and 3 (500 mumol/liter) at 30 min differed significantly. Mean changes in essential PAA between trials 1 (247 mumol/liter) and 3 (334 mumol/liter) at 60 min and between trials 1 (252 mumol/liter) and 3 (80 mumol/liter) at 150 min differed significantly. Mean increments in total and essential PAA were higher and peaked faster but decreased more quickly after trials 2 and 3 than after trial 1. Mean changes in plasma UN did not differ between trials. Ingestion of either L-amino acids, whole protein or the mixture of L-amino acids and whole protein was equally effective in increasing total PAA over 4 hr.

Administration, Oral↗
PubMed1996

Reduction of serotonergic function in rat brain by tryptophan depletion: effects in control and fluvoxamine-treated rats.

The administration of tryptophan (Trp)-free amino acid mixtures to depressed patients responding to serotonin [5-hydroxytryptamine (5-HT)] uptake inhibitors (SSRIs) worsens their clinical state. This procedure reduces Trp availability to brain and thus impairs 5-HT synthesis. We have examined the influence of Trp depletion on extracellular 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the rat brain using in vivo microdialysis. The treatment with the SSRI fluvoxamine significantly increased 5-HT content in dialysates from frontal cortex, as compared with control rats (10.2 +/- 2.7 vs. 3.1 +/- 0.4 fmol per fraction), whereas 5-HIAA was unaffected. Food deprivation for 20 h reduced dialysate 5-HT content to almost control values in fluvoxamine-treated rats (10.2 +/- 2.7 vs. 4.3 +/- 0.6 fmol per fraction) but did not alter dialysate 5-HIAA content (7.8 +/- 0.4 vs. 7.2 +/- 0.5 pmol per fraction). The administration of Trp-free amino acid mixtures to fluvoxamine-treated rats significantly attenuated the release of 5-HT in frontal cortex (approximately 50%) and, to a lesser extent, in the midbrain raphe nuclei. This effect was more marked in rats not deprived from food before the experiments (67% reduction of dialysate 5-HT content in frontal cortex) and was absent in control rats (treated with saline). In contrast, dialysate 5-HIAA was markedly affected by Trp depletion in all groups, including controls (65-75% reductions). These data show that the administration of an amino acid mixture with the same composition and dose (in milligrams per kilogram of body weight) as those inducing a severe mood impairment in depressed patients reduces 5-HT and 5-HIAA concentrations in brain dialysates. The reduction of 5-HT release, however, occurs only in animals previously treated with the antidepressant fluvoxamine for 2 weeks, which would be consistent with a marked reduction of 5-HT-mediated transmission in treated depressed patients but not in healthy controls.

Animals↗
PubMed2003

Quantitative analysis of immobilized proteins and protein mixtures by amino acid analysis.

Biomolecular surface engineering of materials often requires precise, versatile and efficient quantification of immobilized proteins at solid surfaces. Acidic hydrolysis of surface-bound proteins and subsequent HPLC analysis of fluorescence-derivatized amino acids were adapted and critically evaluated for that purpose. Contaminations and concentration-dependent amino acid retrieval during HPLC were found to influence the accuracy of the method. In addition to the choice of adequate conditions for hydrolysis, derivatization and chromatographic separation extensions of the data evaluation were suggested to improve the accuracy of the approach when applied to single protein systems: comparing the experimentally obtained amino acid ratio to the protein constitution enabled to identify the properly separated and detected amino acids. Those amino acids were selected for a more precise calculation of the amount of immobilized protein. To further increase the accuracy of the method, the retrieval of amino acids corresponding to protein amounts in the range between 0.5 and 4.0 microg was analyzed for a variety of proteins of interest to derive protein-specific correction factors. The evaluation of amino acid data was furthermore applied to quantify binary protein mixtures at similar settings. This method was proven useful to detect the composition of protein mixtures throughout a wide range of absolute and relative concentrations.

Amino Acids↗
PubMed1976

Nutrition of Bacillus brevis ATCC 9999, the producer of gramicidin S.

The nutrition of the gramicidin S (GS) producer Bacillus brevis ATCC 9999 was studied with respect to growth and antibiotic production. In a complex medium containing yeast extract and peptone, only glycerol, d-fructose, and meso-inositol contributed to growth, whereas other hexoses, pentoses, polyols, polysaccharides, and organic acids were inactive. Glycerol and fructose were inhibitory to GS formation; inositol had no effect. In chemically defined media containing a mixture of five amino acids (glutamine, methionine, proline, arginine, and histidine) necessary for good growth, again only glycerol, d-fructose, and meso-inositol served as effective carbon sources for growth. With respect to antibiotic formation, inositol was much poorer than glycerol or fructose. In the presence of glycerol and the five amino acids, addition of 0.1% l-phenylalanine specifically stimulated GS production. Growth kinetics in this defined medium showed two phases: early and rapid growth at the expense of the amino acid mixture, followed by glycerol utilization after a diauxic lag of 2 to 3 h; inositol utilization suffered a much longer lag period. GS formation was initiated after the diauxic lag. Ammonium sulfate was the best individual nitrogen source, but the combination of the five growth-stimulatory amino acids was more potent for GS production. The level of potassium phosphate influenced GS production. High levels stimulated the growth rate but progressively inhibited GS production. Methionine was the best sulfur source. A defined medium (F3/6) that supported rapid exponential growth (mu = 0.53 h(-1)) followed by progressively slower growth over a 30- to 40-h period was devised containing fructose, six amino acids, and mineral salts. GS formation was initiated as the cells left the exponential growth phase and reached high levels (1,500 mg of GS per liter; 0.19 mg of GS/mg of dry cell weight) after 40 to 50 h of incubation.

Bacillus↗
PubMed2005

Breastfeeding experience in inborn errors of metabolism other than phenylketonuria.

Breastfeeding has been recommended for the dietary treatment of infants with phenylketonuria, but studies documenting clinical experience in other inborn errors of metabolism are very few. Seven infants diagnosed with methylmalonyl-CoA mutase deficiency (n=2), ornithine carbamoyltransferase deficiency (n=1), propionic acidaemia (n=1), isovaleric acidaemia (n=1), maple syrup urine disease (n=1) and glutaric acidemia type I (n=1) were tried with breastfeeding over two years. After the control of acute metabolic problems, an initial feeding period with a measured volume of expressed breast milk plus a special essential amino acid mixture was continued with breastfeeding on demand and with the addition of a special essential amino acid mixture. Two patients with methylmalonic acidaemia and one patient with glutaric acidaemia type I tolerated breastfeeding on demand very well, with good growth and metabolic control for periods of 18, 8 and 5 months, respectively. In the patient with propionic acidaemia, on-demand breastfeeding continued for 3 months but was terminated after two acute metabolic episodes. The patient with isovaleric acidaemia had insufficiency of breast milk and formula supplementation ended with breast milk cessation. In the patient with severe ornithine carbamoyltransferase deficiency, breastfeeding was stopped owing to poor metabolic control. The patient with maple syrup urine disease also experienced problems, both in metabolic control and in insufficiency of breast milk, resulting in termination of breastfeeding. Breastfeeding of infants with inborn errors of protein catabolism is feasible, but it needs close monitoring with attention to such clinical parameters as growth, development and biochemistry, including amino acids, organic acids and ammonia.

Amino Acid Metabolism, Inborn Errors↗
PubMed1970

Regulation of ribonucleic acid synthesis by histidine and methionine during recovery of Escherichia coli from magnesium starvation.

During magnesium starvation of Escherichia coli B, most of the ribosomes break down to low-molecular-weight components. When magnesium is restored to the medium, the cells recover. The rate of recovery can be increased greatly by supplementing the growth medium with a mixture of 21 amino acids. This increased rate of recovery is shown to be due to the effect of only two amino acids, histidine and methionine, which initially stimulate accumulation of cellular ribonucleic acid without increasing the rate of protein synthesis. In contrast, histidine and methionine supplementation to logarithmically growing E. coli B is not as effective in stimulating growth as is the complete amino acid mixture. Since cells recovering from magnesium starvation preferentially synthesize ribosomes, it is possible that histidine and methionine play a special role(s) in ribosomal ribonucleic acid synthesis or stability.

Amino Acids↗
PubMed1995

Soy consumption and cholesterol reduction: review of animal and human studies.

Animal proteins such as casein are more hypercholesterolemic than soy protein or other plant proteins when fed to rabbits in low-fat, cholesterol-free, semipurified diets. A casein-amino acid mixture produces a hypercholesterolemia similar to that of casein. This appears to be mainly due to lysine and methionine, although other essential amino acids probably contribute to the effect. Arginine appeared to counteract the hypercholesterolemic effects of other essential amino acids. Soy protein gave a lower level of serum cholesterol in rabbits than did a soy protein-amino acid mixture, suggesting the presence of factors in soy protein that counteract the effects of hypercholesterolemic amino acids. Soy protein is also less hypercholesterolemic than casein in other animal species, particularly when the diet contains cholesterol, and substitution of soy protein for animal protein in the diet reduces the concentration of serum cholesterol in humans. This effect is somewhat variable but is generally greater in hypercholesterolemic than in normocholesterolemic subjects. The differing effects of dietary proteins on serum cholesterol concentrations in humans and in rabbits are primarily due to changes in LDL cholesterol, and the hypercholesterolemia produced by dietary casein is associated with down-regulation of hepatic LDL receptors.

Amino Acids↗
PubMed2006

Activity-dependent reversible inactivation of the general amino acid permease.

The general amino acid permease, Gap1p, of Saccharomyces cerevisiae transports all naturally occurring amino acids into yeast cells for use as a nitrogen source. Previous studies have shown that a nonubiquitinateable form of the permease, Gap1p(K9R,K16R), is constitutively localized to the plasma membrane. Here, we report that amino acid transport activity of Gap1p(K9R,K16R) can be rapidly and reversibly inactivated at the plasma membrane by the presence of amino acid mixtures. Surprisingly, we also find that addition of most single amino acids is lethal to Gap1p(K9R,K16R)-expressing cells, whereas mixtures of amino acids are less toxic. This toxicity appears to be the consequence of uptake of unusually large quantities of a single amino acid. Exploiting this toxicity, we isolated gap1 alleles deficient in transport of a subset of amino acids. Using these mutations, we show that Gap1p inactivation at the plasma membrane does not depend on the presence of either extracellular or intracellular amino acids, but does require active amino acid transport by Gap1p. Together, our findings uncover a new mechanism for inhibition of permease activity in response to elevated amino acid levels and provide a physiological explanation for the stringent regulation of Gap1p activity in response to amino acids.

Amino Acid Transport Systems↗
PubMed1977

Absence of the biochemical symptoms of essential fatty acid deficiency in surgical patients undergoing protein sparing therapy.

The biochemical symptoms of essential fatty acid deficiency appear within 7 to 10 days of fat-free total parenteral nutrition using glucose-amino acid mixtures. The linoleic acid (C18:2W6) content of all plasma lipid fractions decreases greatly and plasma eicosatrienoic acid (C20:3W9) increases. We have measured the fatty acid composition of the plasma lipid fractions in six surgical patients receiving parenteral nutritional solutions containing only amino acids, and completely free of glucose, before and after 10 to 14 days of such therapy. Biochemical symptoms of essential fatty acid deficiency did not occur. The fatty acid composition of all plasma lipid fractions remained unchanged after this time period. Mobilization of linoleic acid from the adipose tissue occurred with this treatment in contrast to the inhibition of lipolysis of adipose tissue triglyceride produced by continuous infusions of hypertonic glucose-amino acid mixtures.

Adult↗
PubMed1998

Serotonergic 'vulnerability' in affective disorder: a study of the tryptophan depletion test and relationships between peripheral and central serotonin indexes in citalopram-responders.

A double-blind study of the tryptophan depletion (TD) challenge was performed on a sample consisting of 20 patients with a major depressive disorder in clinical remission after citalopram treatment. TD was induced by the intake of 43 g of an amino acid mixture containing the five large neutral amino acids. The control group received the same mixture, to which 2.3 g tryptophan had been added. Five of the 12 challenged patients showed a worsening of depressive symptoms during the day of the test. In contrast, there was no mood alteration in the eight control patients. Baseline cortisol levels were significantly higher in responders to TD compared to those in non-responders and controls. Platelet serotonin-receptor function and plasma prolactin levels were correlated. There was a significant positive correlation in the baseline data between rated mood state and plasma cortisol and a significant inverse correlation between related mood state and plasma tryptophan concentration. Thus low mood appeared to be associated with low serotonin precursor availability as well as with high cortisol levels.

Adult↗
PubMed2006

Response of muscle protein and glutamine kinetics to branched-chain-enriched amino acids in intensive care patients after radical cancer surgery.

OBJECTIVE: Patients with cancer are characterized by decreased muscle protein synthesis and glutamine availability that contribute to an impaired immune response. These abnormalities worsen after surgical stress. We tested the hypothesis that pharmacologic doses of branched-chain amino acids would improve the early metabolic response after major cancer surgery. METHODS: By using a crossover experimental design, we compared the metabolic effects of isonitrogenous solutions of balanced and branched-chain-enriched amino acid mixtures infused at the rate of 82 mg x h(-1) x kg(-1) for 3 h in patients with colorectal or cervical cancer on the first and second days after radical surgery combined with intraoperative radiation therapy. The ratios of leucine to total amino acid (grams) in the two mixtures were 0.09 and 0.22, respectively. Muscle protein and glutamine kinetics were determined by using stable isotope of amino acids and the leg arteriovenous balance technique. Glucose and insulin were continuously infused throughout the 2-d study to maintain near euglycemia. RESULTS: Rates of muscle protein synthesis and degradation were not significantly affected by the balanced amino acid infusion. In contrast, the isonitrogenous, branched-chain-enriched amino acid mixture accelerated muscle protein turnover by stimulating (P <or= 0.05) protein synthesis. The rate of muscle glutamine de novo synthesis did not significantly change after infusion of the balanced amino acid mixture but increased (P <or= 0.05) by 263 +/- 69% during infusion of the branched-chain-enriched amino acid mixture. CONCLUSIONS: An excess of branched-chain amino acids in the presence of an optimal profile of other essential amino acids acutely increased muscle protein synthesis and glutamine flux from skeletal muscle in cancer patients after surgery.

Amino Acids, Branched-Chain↗
PubMed1979

Effect of SO2 and bisulfite on heterotrophic activity in an acid soil.

Glucose oxidation was inhibited in a forest soil (pH 4.01) previously exposed by 1.0 microliter of SO2 per liter, the extent of inhibition and the decline in pH being directly related to the length of exposure. The phase of rapid CO2 evolution in protein hydrolysate-amended soil previously treated with 5.0 microliter of SO2 per liter for 24 h or 1.0 microliter/liter for 48 h was delayed, but the degradation of the amino acid mixture then proceeded rapidly. Bacterial numbers in soil incubated for 48 h with 1.0 microliter of SO2 per liter were reduced, but the bacteria grew rapidly if glucose or an amino acid mixture was added after the exposure period. Low levels of bisulfite inhibited amino acid decomposition in soil at pH 3.89, but the effect was less pronounced in soil at pH 4.01. Comparable levels of sulfate were not toxic to carbon mineralization. Approximately 1.0 microgram of bisulfite S and about 20 microgram of sulfate S per g of soil appeared when the soil was treated with 1.0 microliter of SO2 per liter for 48 h. Bisulfite added to the soil disappeared readily. The possible ecological significance of the findings is discussed.

Air Pollutants↗
PubMed1990

Effect of the quantity of dietary amino acids on egg production and layings by ceratitis capitata (Diptera, Tephritidae).

1. Diets containing different amounts of an amino acid mixture were tested in terms of egg production and layings by Ceratitis capitata. The amino acid composition of the diet was identical to that of casein. The other components of the diet were: 1.0 g agar, 0.8 g of a salt mixture, 0.8 g of a vitamin mixture, 1.6 g corn oil, 0.2 g Tween 80, 0.5 ml propionic acid, 90 ml distilled water and 0.5 ml of a 20% alcohol solution of nipagin. Diets containing 0.4, 0.8, 1.2, 1.6 and 2.0 g of an amino acid mixture per 100 ml diet and an amino acid-free control diet were used. The diets were made isocaloric by adding 12.4, 12.0, 11.6, 11.2 and 10.8 g sucrose, respectively. 2. The diet containing 1.2 g amino acids proved to be the best, leading to 6.84 egg layings per female per day and to production of 7.72 eggs per female per day.

Amino Acids↗
PubMed1999

Acute tryptophan depletion in healthy young women with a family history of major affective disorder.

BACKGROUND: Acute tryptophan depletion (ATD), a means of reducing brain serotonin synthesis, lowers mood in normal males with a multi-generational family history of major affective disorder (MAD) and in normal women devoid of any family history of psychiatric illness. As both a family history of MAD and female sex are factors predisposing to depression, the hypothesis that a mood lowering response to ATD may reflect a susceptibility to depression was further investigated in young women with an extensive, multi-generational family history of MAD. In addition, the temporal stability of mood change following repeated trials of ATD was also assessed in this study. METHODS: To deplete tryptophan, a tryptophan deficient amino acid mixture was ingested on two separate occasions. The control treatment, administered on a third occasion, was a nutritionally balanced amino acid mixture containing tryptophan. RESULTS: A marked lowering of plasma tryptophan (85-90 %) was achieved by both depletions. In comparison to the balanced condition, family history positive (FH +) women showed no lowering of mood to either the first or second ATD (N = 13) and N = 12, respectively). Mood change between the two ATD trials (N = 13) exhibited poor temporal stability. CONCLUSIONS: These results may indicate that serotonin responsiveness is not an important characteristic of vulnerability to depression in these women. Alternately, these negative results may be due to the exclusion of a large number of FH + women who had already experienced an episode of depression, resulting in the selection of a biased FH + sample who are resistant to the mood lowering effects of ATD.

Adolescent↗
PubMed1986

Response of rats to diets of equal chemical score: effect of lysine or threonine as the limiting amino acid and of an amino acid excess.

The effect of lysine or threonine deficiency with or without excesses of all other amino acids was evaluated in a 21-d feeding study with male rats. Four amino acid mixtures were designed to be first limiting for the rat in lysine or threonine and contained either 0 or 50% excess of nonlimiting amino acids. These mixtures were incorporated into purified diets to provide seven levels [20-140% of the National Research Council (NRC) requirement] of the limiting amino acid. Food intake, body weight gain and carcass composition were measured for each rat to determine the effects of the identity of the limiting amino acid and of amino acid excess on the response to dietary chemical score. Significant effects and/or interactions of the identity of the limiting amino acid (i.e., Lys or Thr) and the presence of excess amino acids were seen for each of the measured responses. At equivalent dietary percentages of the NRC requirement, threonine deficiency supported greater body weight gain than did lysine deficiency. At equivalent deficiencies (Lys vs. Thr) threonine-deficient rats were more susceptible to adverse effects of excess amino acids. When the limiting amino acids were incorporated into the diet through incremental addition of the deficient amino acid mixture, rats responded to levels of lysine or threonine in excess of the NRC requirement. These results suggest that the current NRC requirements for these amino acids are too low and that aspects of the dietary amino acid composition other than the percentage deficit of the limiting amino acid can be important determinants of animal response.

Animals↗