[Laboratorium technics for the diagnosis of inborn errors of amino acid metabolism].
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Amino Acid Metabolism, Inborn Errors↗
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Hepatic amino acid metabolism during hyperinsulinemia and hyperaminoacidemia in conscious rabbit during late pregnancy.
To test whether pregnancy has any effect on amino acid metabolism, we examined in two experimental conditions (1) the effect of hyperinsulinemia on the blood concentration and net hepatic balance of amino acids, and (2) the effect of hyperaminoacidemia on the hepatic handling of amino acids. Experiments were performed in conscious virgin and pregnant rabbits after an 18-hour fast. In the first protocol (hyperinsulinemia), an increment in the plasma insulin level (approximately 45 and 20 microU/mL in the portal vein and artery, respectively) with euglycemia maintained causes a similar decrease (approximately 27% to 34%) in blood amino acid concentrations without any changes in the net hepatic uptake of amino acids in both groups of animals. The hepatic uptake of branched-chain amino acids (BCAA) was practically negligible, whereas there was a consistent uptake of gluconeogenic amino acids in pregnant and nonpregnant rabbits. In the second protocol, hyperaminoacidemia leads to a significantly lower increase in the net hepatic uptake of glycine and serine in pregnant rabbits as compared with nonpregnant rabbits. The same trend was observed for the uptake of individual BCAA, but it did not reach statistical significance. We conclude that in pregnant rabbits (1) insulin does not modify the hepatic uptake of amino acids, and its ability to suppress the release of amino acids from peripheral tissues does not seem to be affected when compared with that in nonpregnant animals, and (2) when hyperaminoacidemia occurs, a greater amount of gluconeogenic amino acids (glycine and serine) would escape the liver, suggesting a higher availability of these circulating amino acids for the fetus.
Amino Acids↗
[Effect of 5-fluorouracil in combination with Astragalus membranaceus on amino acid metabolism in mice model of gastric carcinoma].
OBJECTIVE: To study the effect of 5-fluorouracil-FU in combination with astragalus membranaceus(AM) on amino acid metabolism in mice model of gastric carcinoma induced by 3-methylcholanthrene(MC). METHODS: Mice gastric carcinoma models were established by 3-methylcholanthrene induction and randomly divided into different groups, and received 5-FU treatment (group A) 5-FU plus AM (group B), 5-FU plus a high dose of AM(group C), no treatment (group D). Normal mice were used as control (group N). Free amino acid in the tumor specimens were examined. RESULTS: The levels of free Valine, Methionine, Leucine, Arginine and cystine in the tumor specimens in group D were significantly higher than that in group N(P< 0.05). The levels of free serine in group A, B, C, D were significantly higher than that in group N. The levels of free glutamic acid in group A, B were significantly higher than that in group N(P< 0.05). The levels of free proline in group C, D were significantly higher than that in group P, N(P< 0.05). CONCLUSIONS: The increasing levels of free serine and proline in tumor specimens in gastric cancer mice model reveals metabolic disturbance of amino acid. 5-FU plus astragalus membranaceus can decrease the level of free glutamic acid in the mice models, and inhibit tumor growth.
Amino Acids↗
Muscle amino acid metabolism and the control of muscle protein turnover in patients with chronic renal failure.
Malnutrition is frequently observed in patients with end-stage renal disease. Studies indicate that poor nutritional status plays a major role among factors adversely affecting patients outcome. Therefore prevention and treatment of malnutrition in renal patients is a major issue. In this article the potential mechanisms for alterations in muscle protein metabolism in uremia are explored. Malnutrition has been mainly attributed to inadequate intake of nutrients, superimposed illnesses, or both. However, both clinical and experimental evidence show that uremia per se may adversely affect the control of muscle protein and amino acid metabolism. Available evidence suggests that catabolic factors appear to be distinct for patients at different stages of chronic renal failure and require different modalities of treatments. Both nutritional requirements and the prevalence of malnutrition increase as end-stage renal disease progresses. Muscle protein degradation is increased by metabolic acidosis, which is often found in uremic patients. Another relevant, but less proven cause for increased protein degradation is insulin resistance. Furthermore, specific defects in muscle amino acid metabolism, resistance to growth hormone, insulin-like growth factor 1, or a very low protein intake can reduce muscle protein synthesis. Finally, the hemodialytic procedure per se can stimulate protein breakdown or reduce protein synthesis. All these factors may potentiate the effects of concurrent catabolic illnesses, anorexia, and physical inactivity often found in uremic patients.
Acidosis↗
Amino acid metabolism in human cancer cachexia.
Cancer cachexia is a complex syndrome that occurs with variable incidence in patients with solid tumors and those with hematologic malignancies. It is associated with characteristic physical and laboratory findings, and at a more fundamental level, with significant abnormalities in carbohydrate, lipid, and protein metabolism. These alterations in intermediary metabolism are demonstrable early in the syndrome, even before the onset of weight loss, when the more characteristic features of cancer cachexia are evident. Progressive wasting of peripheral protein stores is a major feature of cancer cachexia and often one of the most graphic realities of malignancy for patients and their families. Unfortunately, significant problems with the animal models of cancer cachexia make conclusions derived from animal studies difficult to extrapolate to humans. Data from human studies indicate that human cancer cachexia is associated with minimal aberrations in circulating free amino acid concentrations; increased whole-body protein turnover, synthesis, and catabolism; reduced rates of skeletal muscle protein synthesis; and increased rates of hepatic protein synthesis. Whether or not these alterations represent pathologic responses or physiologic adaptation by the host to the presence of malignancy remains to be seen. Future investigations must focus on more careful evaluation of interorgan amino acid metabolism, investigation of skeletal muscle protein catabolic rates in cancer cachexia, and definition of the roles of altered hormonal and cytokine regulation of these processes. Such studies will more precisely define the level at which amino acid metabolism is altered significantly and, we hope, permit more specific therapeutic intervention designed to reverse the debilitating effects of cancer cachexia.
Amino Acids↗
Metabolic effects of prostaglandin E1 on human skeletal muscle with special regard to the amino acid metabolism.
The influence of intra-arterial (i.a.) prostaglandin E1 (PGE1) on the metabolism of amino acids, glucose and free fatty acids in healthy volunteers was determined by means of the forearm technique. The continuous increase of perfusion from baseline 2.9 +/- 0.1 ml/100 g x min to 5.4 +/- 1.5 after 60 minutes of PGE1 infusion, indicates an increase of basal glucose utilisation from 0.51 +/- 0.11 to 2.5 +/- 0.36 mumol/100 g x min via and additional raised glucose extraction rate. Furthermore, PGE1 resulted in a cessation of the basal muscular glycerol production and led to a change from a basal production of free fatty acids to a net absorption into the muscle. This change from an oxidation of free fatty acids to glucose results in an improved energetic gain of 0.72 mol ATP/mol 02. Baseline values showed a release of most amino acids which, after PGE1 decreased significantly or even changed to an intake. The overall balance of all amino acids changed from baseline -27.9 (i.e. release) to +33.2 nmol/100 x min (i.e. intake). This indicates an inhibition of muscular proteolyses and/or a stimulation of protein synthesis under i.a. PGE1. This additional metabolic effect of PGE1 might be an explanation as to why agents with purely vasodilating actions did not prove therapeutically effective in the treatment of peripheral arterial disease in the past.
Alprostadil↗
Amino acid metabolism in pediatric patients.
As with energy requirements, protein requirements are relatively much greater in infants and decline progressively with age. Amino acid metabolism in pediatric patients is characterized by the following differences. The requirement for essential amino acids in neonates is larger than that in adults. Because of low activity of phenylalanine hydroxylase and cystathionase, hyperphenylalaninemia and hypermethioninemia tend to occur, whereas tyrosine and cysteine tend to be deficient. In addition to cysteine and tyrosine, histidine, lysine, arginine and taurine are considered as semiessential amino acids. Nowadays there are different kinds of amino acid formulas to satisfy these specific requirements, and most of these formulas are intended to normalize the plasma aminogram. However, the nutritional benefit of these formulas for growth and development is still not completely proven, and the pharmacological use for specific diseases is expected with some modification of these formulas.
Adult↗
Effect of portacaval shunt on sulfur amino acid metabolism in rats.
Male rats were subjected to portacaval shunts (PCS). Postoperative growth curves were similar between PCS and sham-operated control animals, with complete recovery of preoperative body weight occurring within 7 days. PCS rats had 30% smaller livers and 39% larger spleens at autopsy. Total liver levels of reduced glutathione were decreased by 38% in PCS rats. Sulfur amino acid metabolism was studied 6 wk after PCS by injection of L-[methyl-14C]- or L-[1-14C]methionine with 14CO2 collection or by similarly administering L-[35S]methionine or L-[35S] cysteine and measuring 24-h urinary 35SO4, [35S]taurine, and total 35S. There were no significant differences in 14CO2 production over an 8-h period between PCS and sham rats. PCS rats excreted 31% more 35SO4 and 25% more total 35S when injected with 0.9 mmol of [35S]methionine and excreted 38% less [35S]taurine than controls when injected with [35S]-cysteine. These results indicate altered sulfur amino acid metabolism in PCS rats, an animal model of portal-systemic shunting.
Amino Acids, Sulfur↗
Amino acid metabolism in human subcutaneous adipose tissue in vivo.
1. Arteriovenous differences for alanine, glutamate and glutamine were measured across subcutaneous adipose tissue and forearm muscle in normal subjects. 2. After an overnight fast, adipose tissue showed net production of alanine and glutamine and uptake of glutamate in each of 11 subjects. 3. In seven subjects, adipose tissue blood flow was measured and the measurements were continued for 6 h after eating a mixed meal. The pattern of amino acid metabolism across the adipose tissue was remarkably little disturbed after the meal, except for a short period of apparent uptake of alanine as the concentration of that amino acid rose. 4. The pattern of amino acid metabolism across adipose tissue was qualitatively similar to that across the forearm, although it differed quantitatively in that glutamate uptake was more prominent (compared with glutamine release) in the adipose tissue. 5. The rates of alanine and glutamine release observed suggest that adipose tissue may play a substantial role in the whole-body production of these amino acids.
Adipose Tissue↗
[An electroencephalographic study of disorders of amino-acid metabolism during the first days of life (author's transl)].
The authors have attempted a systematic E.E.G. study in 32 neonates suffering from disorders of amino-acid metabolism, during the first days of life. These consisted of cases with ketosis (13 cases of leucinosis, 5 methylmalonic acidaemia, isovaleric acidaemia and 3 with hyperlactacidaemia) and cases without ketosis (6 cases of hyperglycinaemia and 3 with congenital hyperammonaemia). A study of the E.E.G. showed some characteristic features, the most typical of which were: -a periodic tracing with large sharps complexes intermingled with less active periods occurring in every case of hyperglycinaemia without ketosis, in 2 cases of leucinosis and 2 cases of methylmalonic acidaemia. This record indicates a poor prognosis. -a less stereotyped periodic tracing with variable evolution. -distinctive figures characterised by rapid Rolandic rhythms always found in cases of leucinosis compared with sharp spindles (between the 10th and 30th day). It is concluded that the E.E.G. patterns are not in close correlation with the anatomical lesions.
Amino Acid Metabolism, Inborn Errors↗
Amino acid metabolism of bovine blastocysts derived from parthenogenetically activated or in vitro fertilized oocytes.
The uptake and synthesis of 19 amino acids by fresh or frozen-thawed bovine blastocysts produced by parthenogenesis (PT) or in vitro fertilization (IVF) were compared in the present study. Fresh blastocysts, 180 h after IVF or PT activation, and frozen-thawed blastocysts, 168 h old and cultured for 12 h post-thawing, were cultured in synthetic oviduct fluid medium (SOFM) containing polyvinyl alcohol (PVA) with both essential and non-essential amino acids (EAA and NEAA, respectively) (Medium 1: M1) or SOFM containing PVA with only EAA (Medium 2: M2). In Experiment 1, when fresh or frozen-thawed PT blastocysts were cultured in M1, the uptake of glutamate (in fresh only), aspartate and arginine, and the synthesis of glutamine and alanine were significantly enhanced. In the culture with M2, serine, asparagine, glutamate, glutamine, glycine, arginine and alanine were significantly taken up. It was found that the glutamine concentrations was significantly higher (P < 0.001) in the culture medium drops containing embryos than in the drops without embryos. In Experiment 2, when PT blastocysts were cultured in M1, the uptake of aspartate and synthesis of alanine were greater (P < 0.01) than those by IVF blastocysts. When M2 was used, a significant (P < 0.01) production of serine, asparagine, glutamate, glutamine and alanine, and the uptake of arginine by PT blastocysts were observed. In Experiment 3, when IVF blastocysts were cultured in M1, fresh blastocysts depleted more aspartate and glutamate, and produced more glutamine and alanine than frozen-thawed blastocysts. When cultured in M2, frozen-thawed blastocysts depleted more threonine (P < 0.01) than fresh blastocysts. These results indicate that the uptake and synthesis of amino acids were different in fresh or frozen-thawed bovine blastocysts derived from PT or IVF. These differences in amino acid metabolism may be related to the viability of the blastocysts.
Alanine↗
[Amino acid metabolism in liver tissue].
Following determination by the method of ion-exchange chromatography of free amino acids in the blood drawn from the portal and liver veins and the abdominal aorta 30 minutes after introduction of a casein suspension to rats it was found that only 50 per cent of amino acids with ramified chain are retained in the liver. Most of the other amino acids, however, become metabolized largely in the liver and it is only their insignificant part that goes into the general circulation. These data may be of use in considering problems related to the peculiarities of metabolism of amino acids with ramified chain.
Amino Acids↗
Amino acid metabolism in isolated perfused rat liver.
Conflicting evidence concerning hepatic amino acid (AA) metabolism in the isolated perfused rat liver (IPRL) led us to investigate the response of IPRL using perfusates with various AA contents. Perfusion (n = 4) with whole rat blood diluted in Krebs buffer (1:3, v/v) led to acute proteolysis on account of AA deprivation, as shown by the large release of AA (approximately 1400 mumoles in 120 min), especially branched-chain AA (BCAA) (e.g., Leu, 35.4 +/- 10.4 nmole.min-1.g-1 the first hour, 34.3 +/- 5.5 nmole.min-1.g-1 the second hour). In a first attempt to prevent proteolysis, livers (n = 4) were perfused with the previous medium supplemented with AA known for their antiproteolytic activity, at twice their physiological concentrations. Results during the first hour showed uptake of several AA (mainly alanine, glutamine, and proline), reduced release of BCAA (leucine, 12.5 +/- 6.3 nmole.min-1.g-1), and an increase in glucose and urea production. However, during the second hour, because of the use of a recirculating system, progressive AA depletion induced a reappearance of proteolysis. A two-step AA loading technique, i.e., the addition of antiproteolytic AA at the beginning of the perfusion and the addition of a balanced AA mixture at 60 min caused a further decrease in proteolysis during the 2 hr of perfusion (n = 6). Under these conditions, most AA were taken up by the liver with uptake values comparable to those observed in vivo.
Amino Acids↗
[ON AMINO ACID METABOLISM IN THE PLACENTA].
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Amino Acids↗
[Episodic psychoses, porphyria and amino acid metabolism].
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Adult↗
[Role of nutrition in treating hereditary disorders of amino acid metabolism in children].
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Amino Acid Metabolism, Inborn Errors↗
[Diseases of altered amino acid metabolism].
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Alanine↗
Some disorders of amino acid metabolism in man.
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Amino Acid Metabolism, Inborn Errors↗