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PubMed1980

Genetic disorders of glutathione and sulfur amino-acid metabolism. New biochemical insights and therapeutic approaches.

Important insights have recently been derived from studies of inborn human defects of sulfur metabolism. Metabolic lesions responsible for homocystinuria have been elucidated, with possible implications for understanding atherogenesis in the general population. The cause of cystinosis remains enigmatic, but important information has been gained on the origin of some stored cystine from degraded protein. Cysteamine and ascorbic acid deplete the cystine content of cystinotic fibroblasts in vitro, and clinical trials with these agents have been undertaken. Studies of patients with glutathione synthetase deficiency have provided new understanding of the roles of glutathione as in antioxidant and as a modulator of microtubule-related processes. Studies of patients with this disorder and glucose-6-phosphate dehydrogenase deficiency, in which the capacity to maintain glutathione in the reduced state is compromised, indicate that pharmacologic doses of vitamin E can correct certain functional consequences of an inadequate supply of reduced glutathione both in erythrocytes and polymorphonuclear leukocytes. Much remains to be learned about the mechanisms of membrane damage in these states of enhanced oxidative susceptibility.

Amino Acid Metabolism, Inborn Errors↗
PubMed2005

A new reversed-phase liquid chromatographic/tandem mass spectrometric method for analysis of underivatised amino acids: evaluation for the diagnosis and the management of inherited disorders of amino acid metabolism.

Seventy-six compounds of biological interest for the diagnosis of inherited disorders of amino acids (AA) metabolism have previously been demonstrated to be detectable in positive mode electrospray ionisation tandem mass spectrometry (ESI-MS/MS), after separation by ion-pairing reversed-phase liquid chromatography (RPLC). The separation method used tridecafluoroheptanoic acid as ion-pairing agent, and a gradient of acetonitrile for the elution of the most retained compounds. This method had previously been demonstrated to be suitable for the qualitative diagnosis of many AA disorders, and for the quantitative measurement of 16 AA in biological fluids, using their stable isotope labelled (SIL) AA as internal standard. For quantification of the other AA, an internal standard was chosen among the available SIL-AA, as close as possible to the analyte to be measured, in terms of structural analogy, and of retention time in the chromatographic system. The performances of the quantitative analysis of the other AA to be measured are reported here. They show validated results for several AA, allowing their accurate quantification, with another SIL-AA as internal standard. For some other AA, quantitative results were not accurate, allowing only semi-quantitative or qualitative determination for these parameters.

Amino Acid Metabolism, Inborn Errors↗
PubMed1990

Insulin-induced alterations in amino acid metabolism in the fetal lamb.

To investigate the role of insulin in modulation of fetal amino acid metabolism, insulin infusions were performed in 10 chronically-catheterized fetal lambs. Fetal insulin infusion caused a dose related fall in the arterial blood concentrations of 13 of 15 amino acids studied as well as a 15-25% decrease in total amino acid concentration. Fetal lambs exhibited a biphasic response of umbilical total amino acid uptake when compared to fetal blood insulin concentration, i.e., at achieved fetal insulin concentrations less than 100 microU/ml, umbilical uptake of 9 specific amino acids as well as summed amino acid uptake from the umbilical circulation were depressed, but at insulin concentrations of 100-350 microU/ml, amino acid uptakes were similar to or above control values. Insulin infusion also caused a drastic diminution in the rate of fetal urea excretion. These findings suggest that insulin acts in the fetus to depress amino acid catabolism, thus altering amino acid extraction and uptake. Depressed protein catabolism with or without enhanced amino acid uptake would have the theoretical effect of stimulation of net protein synthesis with a shift toward use of nonprotein substrates for energy purposes.

Amino Acids↗
PubMed1992

[Protein turnover and amino acids metabolism in septic rats].

This study was carried out to elucidate the protein and amino acids metabolism in septic rats, using constant infusion of 1-13C-leucine (4mg/hr), 5-13C-glutamine (2mg/hr), 1,2-13C-leucine (4mg/hr), or U-14C-leucine (2.0uCui/hr). Whole body protein kinetics showed that protein breakdown rate was increased in sepsis, but no change was found on protein synthesis rate (PSR). Intestinal mucosal fractional synthesis rate (FSR) was increased with sepsis. However, sepsis caused significant decrease of muscle FSR. Both leucine and glutamine oxidation rates were significantly increased in sepsis. Fraction of leucine degradation via glutamine was significantly increased in sepsis. We concluded that 1) both leucine and glutamine were utilized as important energy fuels in sepsis, 2) whole body PSR was influenced by the change of PSR in each organ, 3) the pathway from leucine to glutamine was significant in the degradation of leucine.

Amino Acids↗
PubMed1976

Alterations of myocardial amino acid metabolism in chronic ischemic heart disease.

Arteriovenous differences (A-V) of all naturally occurring amino acids, lactate, and oxygen were measured simultaneously with coronary sinus blood flow (CSBF) in 8 normal subjects and 11 patients with coronary artery disease at rest and during pacing stress. Mean values for CSBF and myocardial oxygen consumptions (MVO2) for the two groups were similar at rest and during pacing, although mean CSBF and MVO2 increased significantly in both groups in the paced as compared to the rest state. Alanine (ala) was the only amino acid released by the myocardium, while only glutamic acid(glu) demonstrated uptake. Mean A-V ala was negative at rest in the control and coronary disease groups (-4.8+/-3.8 vs. -22.0+/-3.0 nmol/ml, respectively), but was significantly more negative in the coronary group (P less than 0.001) and not statistically different than zero in the normals. A-V ala became significantly negative with pacing in the normals (-10.0+/-4.3 nmol/ml), remained unchanged in the coronary group (-23.0+/-2.9 nmol/ml), and was significantly more negative in the coronary group (P less than 0.05). Calculation of data on the basis of net ala flux ([A-V] X [CSBF X hematocrit]) yielded similar results as that obtained with A-V differences. A-V glu was significantly positive in normals (27.7 +/- 8.9 nmol/ml, P less than 0.01) and coronary patients (59.9 +/- 8.9 nmol/ml, P less than 0.01) at rest but significantly greater in the latter group (P less than 0.001). With pacing, A-V glu remained significantly greater than zero in coronary patients (35.3 +/- 6.3 nmol/ml) and decreased to zero in the normals (4.3 +/- 11.8 nmol/ml). Calculation of net glu flux (nmol/min) at rest yielded data similar to that based on A-V difference. With pacing, net glu flux in the coronary patients did not decrease due to the augmentation of CSBF. No relation between A-V glu or ala and CSBF, MVO2 or A-V lactate was noted. The data demonstrate that specific alterations of myocardial amino acid metabolism characterize patients with chronic ischemic heart disease.

Adult↗
PubMed1990

[Effect of prostaglandin E1 on amino acid metabolism of human skeletal muscle].

The influence of an intraarterial infusion of PGE1 on the amino acid metabolism of human skeletal muscle was examined in healthy volunteers using the forearm technique. A continuous increase of perfusion from 2.9 +/- 0.1 ml/100 g x min to 5.4 +/- 1.5 after 60 min could be observed. Muscular amino acid balances were not changed after 30 min but significantly after 60 min of PGE1 infusion. Muscular release of most of the amino acids was reduced or shifted to an uptake. The accumulated balance of the amino acids showed a significant increase from -21.9 to +33.2 nmol/100 g x min after 60 min. Thus the infusion of PGE1 led to an inhibition of muscular proteolysis and/or to a stimulation of proteosynthesis. In view of the fact that kinines are released during exercise and are partially effective via prostaglandine liberation, the protein-anabolic effect of exercise might be explained by action of prostaglandins.

Adult↗
PubMed1983

Effect of chronic hypernatremic dehydration and rapid rehydration on brain carbohydrate, energy, and amino acid metabolism in weanling mice.

This is a study of the effects of chronic hypernatremic dehydration and rehydration on carbohydrate, energy, and amino acid metabolism in the brains of weanling mice. Chronic hypernatremic dehydration induced by 4 days of water deprivation and salt loading was associated with severe weight loss (no other observed clinical effects), increased brain Na+ levels, and a decreased brain water content. Changes in the concentrations of brain glucose, glycolytic and citric acid cycle metabolic intermediates, and phosphocreatine were compatible with reduced cerebral metabolic rate. In adaptation to chronic hypernatremia, there was a significant increase in the content of the measured brain amino acids. Rapid rehydration over a 4-h period with 2.5% dextrose in water returned plasma Na+ levels and brain Na+ and water contents to normal. After rehydration, metabolites were altered in a manner consistent with increased fluxes through the glycolytic pathway and citric acid cycle; the brain glycogen content almost tripled. Brain taurine and glutamine levels were not lowered by rehydration, and the total content of the measured amino acids in brain was still significantly higher than in controls. We speculate that these metabolic perturbations may relate to the development of cerebral edema and seizures or coma following rapid rehydration of humans with chronic hypernatremic dehydration.

Amino Acids↗
PubMed1986

Extremity amino acid metabolism during starvation and intravenous refeeding in humans.

This study was designed to evaluate peripheral tissue amino acid metabolism in normal subjects who underwent starvation followed by intravenous administration of a nutritional repletion regimen with varying nonprotein caloric sources. Extremity amino acid (AA), arteriovenous differences, and blood flow were measured across forearm and/or leg of 12 healthy male subjects. Plasma AA flux [(arterial concentration - venous concentration) X flow X (1 - hematocrit); ml X min-1 X 100 ml tissue-1] was determined postabsorptively (PA), after 10 days of starvation (ST) and on the 10th day of intravenous feeding (IVF). There was a significant (P less than 0.05) decrease in efflux of total amino acids during the starvation study (-345 +/- 74) compared with the PA study (-1,463 +/- 263). Peripheral tissue AA uptake increased significantly (P less than 0.05) after 10 days of IVF (+276 +/- 79) compared with both PA and ST studies. There were no significant differences in extremity AA flux between those subjects who received 100% dextrose and those receiving 50% dextrose-50% lipid as a nonprotein caloric source. Linear relationships of AA infusion rate (IR) to AA flux (r = 0.845, P less than 0.001) and AA IR to [AA]art IVF (r = 0.842, p less than 0.001) were observed during IVF. Results of this study suggest that extremity flux determinations during IVF cannot be interpreted without correction for AA availability as reflected by AA infusion rate.

Amino Acids↗
PubMed1976

Amino acid metabolism in the piglet. 2. Influence of fasting on plasma free amino acid concentration and in vivo oxidation of methionine, isoleucine and threonine.

1. The influence of a 24 h fast on the concentrations of free amino acids in the plasma, and upon the oxidation rates of methionine, isoleucine and threonine was studied (using early weaned, 4-week-old piglets which were receiving a semi-purified diet. 2. There was no change in the total concentration of the essential amino acids as a result of the 24 h fast: the concentration of the branched-chain amino acids increased, but the effect of this was offset by decreases in the concentrations of arginine, histidine, lysine, methionine and phenylalanine. There was a reduction in the concentration of the non-essential amino acids. 3. The piglets received infusions of L-[I-14C]methionine, L-[U-14C]isoleucine and L-[U-14C]-threonine, and the recovery of the label in carbon dioxide was determined. Less than 5% of the activity from methionine was recovered in the CO2 from the fed piglets, whereas 12% was recovered from the fasted piglets. The corresponding values with threonine were 11 and 19% but there was no effect of fasting on the recovery of the label from isoleucine in CO2. 4. The initial dilution of a single dose of a labelled amino acid infused into the bloodstream depends on the plasma concentration of the amino acid. Nutritional regimens may effect the free amino acid concentration in the plasma. Thus comparisons based upon direct determination of activity recovered in CO2 from the labelled dose of an amino acid with animals on different nutritional regimens could not misleading, unless the differences in the concentrations of the amino acid in the plasma are considered.

Amino Acids↗
PubMedDate not supplied

[Protein and amino acid metabolism in the digestive tract of growing bull calves. 5. The amino acid flow into the duodenum].

The flow of the individual amino acids (AA) into the duodenum was determined after the feeding of 28 different rations to young bulls supplied with duodenal re-entrant cannulae in the live weight range between 140 and 460 kg. The distribution of AA into AA of bacterial origin and AA from the feed was made by difference calculation between the AA at the duodenum (corrected by the endogenous AA quota) and the AA from the bacteria crude protein, with our own results based on a constant AA composition of the bacteria crude protein; by the regression analysis from relative values according to AAD/app. dig. org. m. = a + b AAF/app. dig. org. m. and by the regression analysis of the absolute values according to AAD = b1 app. dig. org. m. + b2 AAF showed the same results from the regression methods but deviating ones from the difference method. The calculation of the flow of the individual AA into the duodenum from the AA content of the ration and the content of app. dig. org. m. of the ration is possible. The equations derived for this purpose of the individual AA are given.

Amino Acids↗
PubMed1981

Sulfur amino acid metabolism in the developing rhesus monkey brain: subcellular studies of the methylation cycle and cystathionine beta-synthase.

The subcellular distributions of the enzymes associated with the methylation and cystathionine-synthesizing portion of the sulfur amino acid metabolic pathway have been determined in the occipital lobe of the rhesus monkey. 5-Methyltetrahydrofolate-homocysteine methyltransferase and 5, 10-methylenetetrahydrofolate reductase activities are located mainly in the soluble compartment. Serine hydroxymethyltransferase activity is located primarily in mitochondria. Cystathionine beta-synthase is a soluble enzyme with a significant component occluded within the nerve endings. Glycine, serine, and cystathionine increase per gram of tissue during development. Glycine and serine are approximately 30% occluded within the nerve endings. These data are consistent with a localization of sulfur amino acid metabolism that supports a differential compartmentation of potential neurotransmitter function and methylation function in the primate.

Amino Acids, Sulfur↗
PubMedDate not supplied

Anabolic steroids support postoperative gut/liver amino acid metabolism.

The effects of an anabolic steroid (nandrolone decanoate, 5 mg/kg) on postoperative splanchnic fuel metabolism were studied in order to gain further understanding of the regulation of the altered gut/liver amino acid metabolism that occurs following catabolic illness. In addition to studying glutamine and alanine, which together transport 60% of whole blood amino acid nitrogen, we determined the fluxes of glutamate and glucose across the gastrointestinal tract and liver in 12 postoperative dogs. Substrate exchange (flux) was calculated by multiplying bloodflow by the arterial-venous concentration difference for each substrate. Arterial glutamine, glutamate, and alanine were significantly increased in dogs receiving the anabolic steroid (AS) compared to control animals (p less than 0.05). Intestinal bloodflow was unchanged, but gut glutamine uptake doubled in dogs receiving steroids (1.4 +/- 0.3 mumol/kg/min in controls vs 2.8 +/- 0.7 in AS, p less than 0.05). Simultaneously, gut alanine release was augmented by 100% in dogs receiving steroids (p less than 0.05). Control dogs demonstrated net glutamate release by the gut, while dogs treated with the anabolic steroid demonstrated glutamate balance (p less than 0.05). Liver bloodflow remained unchanged in AS dogs, but hepatic alanine uptake nearly tripled (p less than 0.01) and hepatic glucose production increased by 60% (p less than 0.05). Anabolic steroids appear to support postoperative splanchnic fuel metabolism by increasing blood amino acid levels, enhancing gut/liver amino acid uptake and processing, and augmenting hepatic gluconeogenesis.

Alanine↗
PubMed2005

Amino acid metabolism of the porcine blastocyst.

The pattern of depletion and appearance of a mixture of amino acids by single porcine blastocysts incubated in two different media has been determined non-invasively using high performance liquid chromatography. Zygotes were produced by the in vitro fertilisation of in vitro-matured, abattoir-derived immature oocytes and cultured in medium NCSU 23 with or without amino acids. Embryos grown in the absence of amino acids up to the blastocyst stage were transferred to amino acid-containing culture medium for measurement of turnover (Experiment 1). Blastocysts grown in NCSU 23+amino acids were transferred into fresh droplets of the same medium (Experiment 2). Although the specific pattern of amino acid production and depletion varied between experiments, a general pattern emerged, with arginine being significantly depleted (p<0.001) and alanine consistently appearing in the media, in quantities that varied depending with culture conditions. The data suggest that arginine is important during porcine blastocyst development, most likely contributing to the formation of nitric oxide and polyamines and that alanine is produced as a means of disposing of excess amino groups. A model for the interactions of amino acids during porcine early embryo development is proposed. The profile of amino acid metabolism by porcine blastocysts is qualitatively and quantitatively similar to that given by human embryos during the morula:blastocyst transition suggesting that the porcine blastocyst is a good model for the human.

Alanine↗
PubMed1992

Regulation of branched chain amino acid metabolism in ruminants.

The regulation of branched-chain amino acid (BCAA) metabolism has been studied in ruminants mainly during the last decade. Evidences support that the rate of BCAA catabolism is lower in ruminants than in monogastrics. This is associated with a low specific BCAA aminotransferase (first catabolic enzyme) activity and a relatively low degree of activation of the second catabolic enzyme in post-natal ruminant tissues. Similarly to monogastrics in vivo BCAA catabolism involves an interorgan cooperation in ruminants. The benefic effect of leucine excess in protein turnover has also been raised. By contrast leucine excess does not stimulate the rate of isoleucine and valine catabolism in ruminants as much as in monogastrics.

Amino Acids, Branched-Chain↗
PubMedDate not supplied

Stoichiometry, kinetics, and regulation of glucose and amino acid metabolism of a recombinant BHK cell line in batch and continuous cultures.

Batch and continuous cultures were carried out to study the stoichiometry, kinetics, and regulation of glucose and amino acid metabolism of a recombinant BHK cell line, with particular attention to the metabolism at low levels of glucose and glutamine. The apparent yields of cells on glucose and glutamine, lactate on glucose, and ammonium on glutamine were all found to change significantly at low residual concentrations of glucose (< 5 mmol/L) and glutamine (< 1 mmol/L). The uptake rates of glucose and glutamine were markedly reduced at low concentrations, leading to a more effective utilization of these nutrients for energy metabolism and biosynthesis and reduced formation rates of lactate and ammonium. However, the consumption of other amino acids, especially the essential amino acids leucine, isoleucine, and valine and the nonessential amino acids serine and glutamate, was strongly enhanced at low glutamine concentration. Quantitatively, it was shown that the cellular yields and rates associated with glucose metabolism were primarily determined by the residual glucose concentration, while those associated with glutamine metabolism depended mainly on the residual glutamine. Both experimental results and analysis of the kinetic data with models showed that the glucose metabolism of BHK cells is not affected by glutamine except for a slight influence under glucose limitation and glutaminolysis not by glucose, at least not significantly under the experimental conditions. Compared to hybridoma and other cultured animal cells, the recombinant BHK cell line showed remarkable differences in terms of nutrient sensitivity, stoichiometry, and amino acid metabolism at low levels of nutrients. These cell-line-specific stoichiometry and nutrient needs should be considered when designing an optimal medium and/or feeding strategy for achieving high cell density and high productivity of BHK cells. In this work, a cell density of 1.1 x 10(7) cells/mL was achieved in a conventional continuous culture by using a proper feed medium.

Amino Acids↗
PubMedDate not supplied

Effect of distal splenorenal shunt plus splenopancreatic disconnection on glucose and amino acid metabolism.

BACKGROUND/AIMS: The Warren-Zeppa distal selective splenorenal shunt (DSRS) is aimed at decompressing esophageal varices by a distal splenorenal shunt, at the same time ligaturing left gastric, gastroepiploic and umbilical veins. In the long-term follow-up the loss of shunt selectivity was observed in several cases. Therefore, Inokuti and Warren reported splenopancreatic disconnection (SPD) to prevent splenic collaterals from stealing portal venous blood. METHODOLOGY: This report presents metabolic data (K-glucose, IRI in iv-GTT, Fischer ratio) of 10 cirrhotic patients operated with DSRS plus SPD. RESULTS: K-glucose of iv-GTT was improved from 2.3 +/- 0.2 to 2.5 +/- 0.2. Fischer ratio was also improved from 1.58 to 2.0 after the operation. IRI behavior tends to be lower after operation as a result of devascularlization of the collateral circulation by the selective shunt. CONCLUSIONS: From these results it seems that DSRS+SPD has favorable effects on glucose and amino acid metabolism.

Amino Acids↗
PubMed1976

American Academy of Pediatrics. Committee on Nutrition: special diets for infants with inborn errors of amino acid metabolism.

A sufficient variety of semisynthetic dietary products is now available to permit control of amino acid imbalance in several inborn errors of metabolism. However, they must be used carefully, and their effects monitored closely. Continuing development of products for this type of special diet--to provide a wider variety--is necessary. Regionalization of treatment programs for patients with inborn errors of metabolism is recommended. Metabolic centers which are accumulating experience and have good laboratory support may be the most efficient way of providing adequate treatment for patients with inborn errors of metabolism.

Amino Acid Metabolism, Inborn Errors↗