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PubMed1985

Studies on requirements for amino acids in infants with disorders of amino acid metabolism. I. Effect of alanine.

Two infants with disorders of propionate metabolism were studied at 7 months of age to determine optimum levels of intake of protein and calories to meet the requirements for essential amino acid for growth in infancy, and at the same time minimize the accumulation of toxic intermediates. An effect of alanine was found that permitted growth at otherwise limiting levels of protein intake. This was not simply an effect of nonessential nitrogen as neither glycine nor glutamic acid could substitute for alanine in this protein-sparing effect. This appears to represent further evidence of the relationship between alanine and the branched-chain amino acids and of the importance of the alanine-glucose cycle in human physiology.

Alanine↗
PubMedDate not supplied

[Inborn disorders of amino acid metabolism as etiologic factors in progressive encephalopathy in the early neonatal period].

The authors report three cases of neonates with severe, progressive encephalopathy provoked by congenital disturbances of amino acid metabolism (hyperglycinemia, citrulinemia, and hyperamoniemia type: II). The occurrence of convulsions is particularly pointed out, because they are the most indicative signs of brain damage manifested in the first seven days of life.

Amino Acid Metabolism, Inborn Errors↗
PubMed1997

[Effect of recombinant growth hormone on amino acids metabolism in blood and urine after major operation].

To determine the effects of recombinant human growth hormone (GH) on postoperative amino acids metabolism, we performed a placebo-controlled randomized double-blind trial in 18 patients after elective gastrectomy or colectomy. The same amount of calories and amino acids were administered. Research group was daily injected growth hormone 0.15 IU/(kg.day) and control group was given placebo during the first postoperative week. All urine were analyzed for nitrogen balance and excretion of 3-methylhistidine. On the seventh postoperative day while the parenteral nutrients were being infused, amino acid exchange across the forearm was measured. On the seventh postoperative day all patients' amino acids in plasma were slightly increased by comparing with preoperative day but was not statistical significance. Forearm arterial-venous difference (A-V) measured on POD + 7 was markedly different between groups. There was continued release of amino acids from the forearm in the control subjects, while there was marked amino acid uptake in the GH patients (total amino acid nitrogen exchange was -398 +/- 158 mumol/L vs +165 +/- 61 mumol/L, P < 0.01). Excretion of urinary 3-methylhistidine in control group loss more than in GH group (7.3 +/- 1.0 mumol/(kg.24 h) vs 4.4 +/- 0.3 mumol/(kg.24 h), P < 0.05). The results demonstrated that GH can increase the uptake of amino acid from forearm and decrease the excreation of 3-methylhistidine in urine after operation, but did not disturb the balance of amino acids in plasma.

Amino Acids, Branched-Chain↗
PubMed2005

Ion-pairing reversed-phase liquid chromatography/electrospray ionization mass spectrometric analysis of 76 underivatized amino acids of biological interest: a new tool for the diagnosis of inherited disorders of amino acid metabolism.

Seventy-six molecules of biological interest for the diagnosis of inherited disorders of amino acids (AA) metabolism have previously been demonstrated to be detectable in electrospray ionization tandem mass spectrometry (ESI-MS/MS) positive mode without derivatization. Reversed-phase liquid chromatography (RPLC) separation on different C18 columns using various perfluorinated carboxylic acids as ion-pairing agents has been found suitable for coupling with MS/MS, and for the separation of AA. A new procedure was optimized in order to replace the usual ion-exchange chromatographic, post-column ninhydrin derivatization, time-consuming routine method. This procedure allowed an adequate separation of all the molecules from other known interfering compounds, and a throughput of two samples per hour. Quantification limits for each molecule were found to be compatible with their measurement in plasma and urine. We validated the qualitative part of the method by analyzing plasma and urine samples from patients affected with several inherited disorders of AA metabolism. We validated the quantification of 16 AA using their stable isotopes as internal standard. The calibration curves were linear over the range 0-3 mM. The quantitative results obtained with the new method on 105 plasma and 99 urine samples were in good agreement with those obtained by the established routine method. Spiking experiments and precision results were also satisfactory.

Amino Acid Metabolism, Inborn Errors↗
PubMed1986

Effect of starvation and a protein diet on the amino acid metabolism enzyme activities of the organs of domestic fowl hatchlings.

The activities of alanine and aspartate transaminases, adenylate deaminase, glutamine synthetase and glutamate and xanthine dehydrogenases have been measured in liver, yolk sac membrane, intestine and breast and leg muscle of domestic fowl hatchlings receiving for 3 or 5 days either a standard diet or hard boiled eggwhite as well as in 3 or 5 days starved animals. The patterns of activation of amino acid metabolism enzymes were fully comparable in protein-fed and starved groups with respect to fed controls; the differences with respect to the latter became more marked in 5- than in 3-days old chicks. In 5-days old chicks intestine alanine transaminase activity increased in parallel to that of liver in protein-fed animals but not in those starved, in agreement with an enhanced alanine transfer between both organs under this situation. Both, starvation and protein-feeding, induced a general decrease in the amino acid metabolizing ability of muscle. Glutamine (but not alanine) synthetizing capabilities were enhanced.

AMP Deaminase↗
PubMed1996

Influence of glutamine-supplemented parenteral nutrition on intestinal amino acid metabolism in rats after small bowel resection.

Glutamine (Gln)-supplemented total parenteral nutrition (TPN) has been shown to improve mucosal adaptation after massive small bowel resection (SBR); however, its influences on intestinal amino acid metabolism remain unknown. In this study, intestinal amino acid flux, circulating plasma aminogram, mucosal glutaminase activity and protein, and DNA content were measured 7 days after massive SBR in rats receiving either standard (Std) or Gln-supplemented TPN. Sham-operated rats and rats fed chow after enterectomy served as controls. The uptake of Gln and the release of citrulline (Cit) by the remaining intestine was significantly decreased, with reduced mucosal glutaminase activity after SBR in the Chow and Std-TPN groups. Glutamine supplementation resulted in significantly increased gut Gln uptake compared with Std-TPN (P < 0.01). Mucosal glutaminase activity, mucosal protein, and DNA content was also increased by Gln; however, the gut release of Cit remained unchanged (P > 0.05). The subsequent decrease in circulating arginine (Arg) in the Gln-TPN group compared with the Std-TPN group (P < 0.05) was attributed to an insufficient exogenous supply. These findings show that Gln-supplemented TPN improves mucosal growth and gut Gln uptake after SBR. However, the intestinal production of Cit, which remained low in both TPN groups, may lead to an insufficiency of endogenous Arg synthesis. Thus, both Gln and Arg may be essential amino acids after SBR.

Amino Acids↗
PubMed2002

Hepatic amino-acid metabolism in liver cirrhosis and in the long-term course after liver transplantation.

The aim of this study was to investigate the impact of orthotopic liver transplantation (OLT) on plasma levels and splanchnic turnover of key amino acids for muscular (branched-chain amino acids: BCAAs) and hepatic metabolism (aromatic amino acids (AAAs) and methionine) in 48 patients with cirrhosis, 14 patients after OLT, and 46 controls. Also, hepatic amino-acid supply and resting energy expenditure were measured. BCAA levels (no hepatic uptake) decreased in cirrhosis (P<0.001) and were improved, although not normalized, after OLT (P<0.001). AAA and methionine levels were raised in cirrhosis (P<0.001) and normalized after OLT (P<0.001). Hepatic supply of these amino acids increased in patients graded Child B and C and decreased significantly after OLT. Splanchnic uptake of AAAs and methionine increased significantly in Child-B and decreased in Child-C patients. After OLT, splanchnic extraction of AAAs and methionine was as in Child A. Circulating AAAs and methionine correlated with indocyanine-green half-life (r=0.71, P<0.001) and resting energy expenditure (r=0.50, P<0.001), indicating that levels of circulating AAAs and methionine in cirrhosis are determined by hepatic and extra-hepatic metabolic factors. This study demonstrates persistent changes in muscular metabolism of BCAAs after OLT, while the hepatic amino-acid metabolism is normalized due to (1) a significant reduction in the rate of peripheral proteolysis, and (2) improved liver function compared with that in patients with cirrhosis.

Adult↗
PubMed1994

Effects of essential phospholipids on the amino acid metabolism in whole body irradiated rats.

Ionizing radiation induces injury to cell membranes resulting in an increase of plasma amino acids concentration and catabolic response of the body. Essential phospholipids (EPL) administered before radiation protect the cell structures and can be used for their renewal. For this reason EPL are expected to have some effect on amino acid metabolism in radiation sickness. The adult male Wistar rats were injected with EPL in a dose of 125 mg EPL/kg b.w. (Essentiale) or saline solution. Three h later whole-body gamma irradiation with a single dose of 10 Gy was performed. Untreated pair-fed rats served as control. The rats were sacrificed 2 days after irradiation. In irradiated rats a decrease in body weight, increased concentrations of plasma amino acids, higher oxidation of branched chain keto acids in liver mitochondria, higher incorporation of leucine into liver proteins and decreased leucine incorporation into proteins of small intestine were observed. In EPL pretreated rats a longer survival time, a higher body weight, lower levels of plasma amino acids and higher protein synthesis in small intestine and in liver when compared with irradiated, saline treated rats were found. No significant changes were observed in branched chain amino acid oxidation measured by means of labeled ketoisocaproate in liver mitochondria.

Amino Acids↗
PubMed1990

Genetically altered brain amino acid metabolism in spontaneously hypertensive rats: a study by using young spontaneously hypertensive rats and renal hypertensive rats.

Previously we demonstrated altered amino acid levels in brainstem regions of adult spontaneously hypertensive rats (SHR). For comparison, in this study, we determined amino acid concentrations in discrete brainstem regions in young prehypertensive SHR and renal hypertensive rats. In prehypertensive SHR, the content of glutamate was increased in the rostral ventrolateral medulla and the caudal ventrolateral medulla, and the content of beta-alanine was decreased in the nucleus tractus solitarii. In renal hypertensive rats, there was no change in glutamate and beta-alanine contents in all the regions. The profiles of contents of glutamate and beta-alanine in the brainstem regions in young SHR but not in renal hypertensive rats are the same as those found previously in adult SHR. Thus, the results of the present study suggest that the altered amino acid metabolism in the brainstem of SHR may be genetically inherent.

Amino Acids↗
PubMed1998

A molecular model of human branched-chain amino acid metabolism.

To establish an accurate molecular model of human branched-chain amino acid (BCAA) metabolism, the distribution, activity, and expression of the first 2 enzymes in the catabolic pathway--branched-chain-amino-acid aminotransferase (BCAT) and branched-chain alpha-keto acid dehydrogenase (BCKD) complex--were determined in human tissues. The same enzyme activities were measured in rat and African green monkey tissues. Overall, the activities of BCAT and BCKD were higher in rat than in human and monkey tissues; nevertheless, the ratio of the 2 activities was similar in most tissues in the 3 species. Total oxidative capacity was concentrated in skeletal muscle and liver (> 70%) with muscle having a higher proportion of the total in humans and monkeys. In humans, brain (10-20%) and kidney (8-13%) may contribute significantly to whole-body BCAA metabolism. Furthermore, in primates the high ratio of transaminase to oxidative capacity in the entire gastrointestinal tract serves to prevent loss of essential BCAA carbon and raises the possibility that the gastrointestinal tract contributes to the plasma branched-chain alpha-keto acid pool. Quantitative polymerase chain reaction was used to examine expression of human branched-chain alpha-keto acid dehydrogenase kinase (BCKDK), the key enzyme that regulates the activity state of the human BCKD complex and human BCAT isoenzymes. To design the primers for the polymerase chain reaction, human BCKDK was cloned. BCKDK message was found in all human tissues tested, with the highest amount in human muscle. As in rats, there was ubiquitous expression of mitochondrial BCAT, whereas mRNA for the cytosolic enzyme was at or below the limit of detection outside the brain. Finally, the role of BCAA in body nitrogen metabolism is discussed.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1989

Peritoneal dialysis in the treatment of metabolic crises caused by inherited disorders of organic and amino acid metabolism.

Four neonates who presented with coma secondary to hyperammonaemia resulting in central respiratory failure were treated with peritoneal dialysis for between 16 and 120 hours. Underlying diseases were maple-syrup-urine disease, propionic acidaemia and citrullinaemia in two patients. Clinical improvement was observed in three patients within 16 to 72 hours after institution of peritoneal dialysis. Biochemical analysis revealed a rapid reduction in plasma concentration of leucine, isoleucine and valine as well as their alpha-keto-analogues in the infant suffering from maple-syrup-urine disease. Correction of ammonia, glycine, alanine and propionic acid concentrations was observed in the infant with propionic acidaemia 24-72 hours after institution of peritoneal dialysis. Severe hyperammonaemia (1,000-2,500mumol/l) in two infants with citrullinaemia before peritoneal dialysis was treated successfully in one infant; whereas the second infant showed no clinical improvement despite amelioration of biochemical parameters. Glucose-absorption from peritoneal dialysis solution was in the range of 216-441 mg/kg/h.

Amino Acid Metabolism, Inborn Errors↗
PubMed1993

Different sensitivity of glucose and amino acid metabolism to insulin in NIDDM.

NIDDM subjects are characterized by impaired glucose tolerance and insulin resistance with respect to glucose metabolism. To examine whether the defect in glucose utilization extends to amino acid metabolism, 6 NIDDM subjects (64 +/- 4 yr of age; ideal body weight of 107 +/- 3%) and 7 control subjects (58 +/- 4 yr of age; ideal body weight of 105 +/- 2%) were studied with the euglycemic insulin clamp technique, in combination with [1-14C]leucine and indirect calorimetry. All subjects participated in two studies. In study 1, after 3 h of tracer equilibration, a 3-h insulin clamp (40 mU.m-2 x min-1) was performed to define the effect of insulin on leucine kinetics and glucose metabolism. In study 2, subjects received a repeat 3-h insulin clamp, and a balanced amino acid solution was infused to increase the plasma amino acid concentrations approximately 2-fold to examine the effect of combined physiological hyperinsulinemia-hyperaminoacidemia on the rate of leucine and glucose disposal. Insulin-mediated total body glucose uptake was significantly reduced in NIDDM during both study 1 (5.6 +/- 0.4 vs. 6.9 +/- 0.6 mg.kg-1 x min-1, P < 0.01) and study 2 (5.2 +/- 0.4 vs. 6.8 +/- 0.6, P < 0.01). Basal plasma leucine (120 +/- 10 vs. 123 +/- 11 microM) and alpha-ketoisocaproic acid concentrations (28 +/- 3 vs. 25 +/- 2 microM) were similar in NIDDM and control subjects, respectively. In contrast, the basal plasma glucose concentration (8.9 +/- 0.8 vs. 4.7 +/- 0.2 microM) and the HbA1c (8.5 +/- 0.2 vs. 5.7 +/- 0.2%) were significantly increased in NIDDM (P < 0.01). In the postabsorptive state, endogenous leucine flux, leucine oxidation, and nonoxidative leucine disposal were similar in NIDDM and control subjects. When insulin was infused without amino acids (study 1), the decrement in plasma leucine (53 +/- 5 vs. 48 +/- 4 microM), endogenous leucine flux (13 +/- 2 vs. 11 +/- 1 mumol.m-2 x min-1), leucine oxidation (1.6 +/- 0.2 vs. 1.3 +/- 0.1 mumol.m-2 x min-1), and nonoxidative leucine disposal (10 +/- 1 vs. 8 +/- 1 mumol.m-2 x min-1) was comparable in both groups. During combined insulin and amino acid infusion (study 2), plasma leucine concentration (185 +/- 20 vs. 190 +/- 15 microM) rose similarly in NIDDM and control subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1987

Branched-chain amino acid metabolism in rat muscle: abnormal regulation in acidosis.

Branched-chain amino acid (BCAA) metabolism is frequently abnormal in pathological conditions accompanied by chronic metabolic acidosis. To study how metabolic acidosis affects BCAA metabolism in muscle, rats were gavage fed a 14% protein diet with or without 4 mmol NH4Cl X 100 g body wt-1 X day-1. Epitrochlearis muscles were incubated with L-[1-14C]-valine and L-[1-14C]leucine, and rates of decarboxylation, net transamination, and incorporation into muscle protein were measured. Plasma and muscle BCAA levels were lower (P less than 0.05) in acidotic rats. Rates of valine and leucine decarboxylation and net transamination were higher (P less than 0.05) in muscles from acidotic rats; these differences were associated with a 79% increase in the total activity of branched-chain alpha-keto acid dehydrogenase and a 146% increase in the activated form of the enzyme. We conclude that acidosis affects the regulation of BCAA metabolism by enhancing flux through the transaminase and by directly stimulating oxidative catabolism through activation of branched-chain alpha-keto acid dehydrogenase.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2003

ESI-MS/MS analysis of underivatised amino acids: a new tool for the diagnosis of inherited disorders of amino acid metabolism. Fragmentation study of 79 molecules of biological interest in positive and negative ionisation mode.

The diagnosis of inherited disorders of amino acids (AA) metabolism is usually performed on automated analysers by ion-exchange chromatography and quantification after ninhydrin derivatisation of about 50 different AA. A single run liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for these molecules can be an alternative to this time-consuming technique. The first step of this development is the infusion study of the fragmentation of 79 molecules of biological interest in electrospray ionisation tandem mass spectrometry (ESI-MS/MS), in positive and in negative ionisation mode. Among them, three molecules can be detected only in negative ionisation mode, 38 only in positive mode and 38 in the two modes. All the most abundant fragmentations are presented, with optimisation of the MS/MS parameters. The positive ionisation mode was retained for the simultaneous analysis of 76 molecules. One sensitive and/or specific transition is proposed for the monitoring of each molecule. Improvement in sensitivity of detection was obtained with the use of an acidic mobile phase. Flow injection analysis studies led us to highlight a number of interferences-due to isobaric molecules, to in-source collision-induced dissociation, or to natural isotopic distribution of the elements-which are listed. For a reliable quantification method, these molecules have to be separated by LC before analysis in the tandem mass spectrometer. Ion-pairing reversed-phase liquid chromatography (RPLC) using perfluorinated carboxylic acids as ion-pairing agents has already been found suitable for analysis of AA in MS/MS positive ionisation mode and is under development.

Amino Acid Metabolism, Inborn Errors↗
PubMed2004

An integrative model of amino acid metabolism in the liver of the lactating dairy cow.

The objective of this work was to construct a dynamic model of hepatic amino acid metabolism in the lactating dairy cow that could be parameterized using net flow data from in vivo experiments. The model considers 22 amino acids, ammonia, urea, and 13 energetic metabolites, and was parameterized using a steady-state balance model and two in vivo, net flow experiments conducted with mid-lactation dairy cows. Extracellular flows were derived directly from the observed data. An optimization routine was used to derive nine intracellular flows. The resulting dynamic model was found to be stable across a range of inputs suggesting that it can be perturbed and applied to other physiological states. Although nitrogen was generally in balance, leucine was in slight deficit compared to predicted needs for export protein synthesis, suggesting that an alternative source of leucine (e.g. peptides) was utilized. Simulations of varying glucagon concentrations indicated that an additional 5 mol/d of glucose could be synthesized at the reference substrate concentrations and blood flows. The increased glucose production was supported by increased removal from blood of lactate, glutamate, aspartate, alanine, asparagine, and glutamine. As glucose output increased, ketone body and acetate release increased while CO(2) release declined. The pattern of amino acids appearing in hepatic vein blood was affected by changes in amino acid concentration in portal vein blood, portal blood flow rate and glucagon concentration, with methionine and phenylalanine being the most affected of essential amino acids. Experimental evidence is insufficient to determine whether essential amino acids are affected by varying gluconeogenic demands.

Amino Acids↗
PubMed1979

Observations on the composition of milk-substitute products for treatment of inborn errors of amino acid metabolism. Comparisons with human milk. A proposal to rationalize nutrient content of treatment products.

We tabulated and compared the stated compositions of four milk-substitute products, now in wide use for the treatment of various inborn errors of amino acid metabolism, and the known composition of human milk. Variations between the treatment products is great not only in the content of amino acids but also in minerals and vitamins, for example. Different source materials and rationales for their manufacture appear to explain these differences. All four products deviate in many ways from the composition of human milk. Although the existing treatment products are quite effective clinically, we propose that a more rational approach to the feeding of young infants whose nutrition is compromised by inborn errors of metabolism would begin with a synthetic product based on the composition of human milk that could be modified specifically to fit the needs and tolerance of the individual patient.

Amino Acid Metabolism, Inborn Errors↗