Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMINO ACID METABOLISM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed1996

Eicosanoid and amino acid metabolism in transient acute psychoses with psychedelic symptoms.

It has been hypothesized that a disturbance of glutathione (GSH) metabolism might be a common factor in many psychiatric disorders. The aim of the present study was to test this hypothesis in transient acute psychotic patients with distorted perceptions. Since the metabolism of GSH is related to that of thromboxane B2 (TXB2), prostaglandin E (PGE) and some amino acids, we determined these substances in the plasma of 15 patients and 17 normal controls. Plasma concentrations of TXB2 were significantly higher and concentrations of serine and tryptophan were significantly lower in patients than in controls. Large variation was observed in plasma PGE levels in patients, although mean values did not differ significantly from controls. These results are consistent with the hypothesis that the metabolism of GSH is impaired in transient psychotic states.

Adult↗
PubMed1978

Carbohydrate, lipid and amino acid metabolism following physical exercise in man.

To elucidate early metabolic adaptations of physical training obese and nonobese subjects were studied before and at different intervals after 1 h of bicycle exercise at 70% of maximal working capacity. Four h after exercise intravenous glucose tolerance (IVGT) and plasma level of alanine were decreased. Compared to the diurnal variation plasma concentration of cortisol was increased. Twenty-four hours after exercise plasma concentrations of cortisol and trihlycerides were decreased. Furthermore, plasma insulin during IVGT test was decreased and blood glycerol increased in the obese subjects. There were no changes in basal insulin, IVGT, or plasma levels of amino acids which were elevated in the obese subjects (valine, isoleucine, leucine, tyrosine, phenylalanine). Forty-eight hours after exercise plasma insulin during IVGT test and plasma triglycerides remained decreased in the obese subjects. Low cortisol levels 24 h after exercise might result in increased insulin effect leading to low plasma insulin levels seen in physically trained subjects. Elevated glycerol levels in the obese subjects might be the first sign of diminishing fat stores secondary to increased lipolysis.

Adult↗
PubMed1981

Effects of clofibric acid on amino acid metabolism in cultured rat skeletal muscle.

Well-differentiated cultured skeletal muscle cells (myotubes) obtained from adult rats were incubated for up to 48 h in Dulbecco's modified Eagle's medium. Medium glucose decreased from 4.9 +/- 0.1 mM at 0 h to 13 +/- 1 microM by 24 h; approximately 60% of glucose was converted to lactate. Pyruvate, alanine, and citrate were continuously produced, even during the period of 24-48 h when no glucose or lactate utilization was observed. Branched-chain amino acid utilization increased more than fourfold during the incubation period of 24-48 h; during this time, intracellular ATP, pyruvate, alpha-ketoglutarate, malate, and citrate levels were constant despite the absence of glucose or lactate consumption. Incubation of muscle cells with 2 mM clofibric acid resulted in a 76% inhibition of leucine metabolism. Coincident with the drug-induced inhibition of a branched-chain amino acid utilization, alanine and citrate production was blocked, and cell levels of pyruvate, alpha-ketoglutarate, malate, and citrate were markedly reduced. These studies suggest branched-chain amino acids contribute significantly to anaplerotic pathways in cultured skeletal muscle cells and that these pathways lead to the net production of alanine and citrate during periods of minimal carbohydrate utilization.

Alanine↗
PubMed1978

Skeletal muscle protein and amino acid metabolism in experimental chronic uremia in the rat: accelerated alanine and glutamine formation and release.

The kinetics and factors regulating alanine and glutamine formation and release were investigated in skeletal muscle preparations from control and experimentally uremic rats. These preparations maintained phosphocreatine and ATP levels in vitro which closely approximated levels found in vivo. Alanine and glutamine release from uremic muscle were increased 45.8 and 36.0%, respectively, but tissue levels were unaltered. The increased release of alanine by uremic muscle was not accounted for by decreased rates of medium alanine reutilization via oxidation to CO(2) or incorporation into muscle protein. The maximal capacity of added amino acids such as aspartate, cysteine, leucine, and valine to stimulate net alanine and glutamine formation was the same in uremic and control muscle. Epitrochlearis preparations were partially labeled in vivo with [guanido-(14)C]-arginine. On incubation, preparations from uremic animals showed a 54.6% increase in the rate of loss of (14)C-label in acid precipitable protein. Correspondingly, these same uremic preparations showed a 62.7% increase in (14)C-label appearance in the acid-soluble fraction of muscle and in the incubation media. Insulin decreased alanine and glutamine release to an extent threefold greater in uremic than in control preparations, and increased muscle glucose uptake approximately threefold in all preparations. Although basal rates of [4,5-(3)H]leucine incorporation into protein were decreased 25% in uremic muscles as compared with control muscles, insulin stimulated [(3)H]leucine incorporation nearly equally in both preparations. These data demonstrate increased alanine and glutamine production and release from skeletal muscle of chronically uremic rats. This increase appears to derive in part from an enhancement of net protein degradation which could be caused by an acceleration in the breakdown of one or more groups of muscle proteins, or by an inhibition of protein synthesis, or by both processes. The increased alanine and glutamine formation and release in uremia appears not to result from an insensitivity to insulin action. The implications of these findings for an understanding of the abnormal carbohydrate metabolism of uremia are discussed.

Adenosine Diphosphate↗
PubMed1982

Amino acid metabolism in patients with severe burns.

In this study we set out to determine, if relative to net catabolism of skeletal muscle protein as measured by phenylalanine release, the transamination of branched-chain amino acids (valine, isoleucine, and leucine) was greater in nonseptic burn patients than in controls. Arterial and femoral venous amino acid concentrations and circulating liver enzyme levels were measured. When the ratio of the arterial-femoral venous difference in concentration of each branched-chain amino acid to that of phenylalanine was determined, transamination of the branched chain amino acids, relative to net proteolysis, was not occurring at a greater rate in the burn patients. The net release of alanine relative to that of phenylalanine was not significantly greater in the burn patients, consistent with the conclusion that relative to the net rat of proteolysis, transamination of branched-chain amino acids in skeletal muscle is not increased in burn patients. This finding differs from that in septic dogs and septic humans. The mean arterial-femoral venous differences in concentration of alanine, valine, isoleucine, leucine, and phenylalanine were greater in the burn patients (P less than 0.03), indicating increased proteolysis in this group.

Adult↗
PubMed1984

Mutations affecting the sulphur assimilation pathway in Aspergillus nidulans: their effect on sulphur amino acid metabolism.

Several sul-reg mutants of Aspergillus nidulans isolated as constitutive for arylsulphatase were studied with respect to the regulation of enzymes involved in cysteine and homocysteine synthesis and to the pool of sulphur amino acids. All mutants examined showed a decreased concentration of glutathione as compared with the wild type, and all mutants, with one exception, had a decreased total pool of sulphur amino acids. The results suggest that the mutants are leaky in the sulphate assimilation pathway. They show derepression of cysteine synthase, homocysteine synthase, cystathionine beta-synthase and gamma-cystathionase. In spite of having derepressed homocysteine synthase, the enzyme which constitutes an alternative pathway for homocysteine synthesis, the sul-reg mutations do not suppress lesions in genes required for the main homocysteine-synthesizing pathway. This indicates that the derepression of homocysteine synthase is not in itself sufficient for physiological functioning of this enzyme, but seems to depend also on the effectiveness of cysteine synthesis and sulphide formation.

Amino Acids, Sulfur↗
PubMed1968

Effect of triperidol on carbohydrate and amino acid metabolism in rat brain-cortex slices.

1. The effect of triperidol on the metabolism of glucose, pyruvate, glutamate, aspartate and glycine was studied with rat brain-cortex slices, U-(14)C-labelled substrates and a quantitative radiochromatographic technique. 2. Triperidol at a concentration of 0.2mm decreased the oxygen uptake and the (14)CO(2) production by about 30% when glucose, pyruvate and glutamate were used as substrates, whereas no effects were observed with aspartate and glycine. 3. The drug did not alter qualitatively the metabolic pattern of the substrates. 4. Quantitatively, triperidol decreased the incorporation of (14)C from [U-(14)C]glucose and [U(14)-C]-pyruvate into glutamate, glutamine and gamma-aminobutyrate but not into lactate, alanine and aspartate. The overall utilization rates of glucose and pyruvate were decreased. The relative specific radioactivities of glutamate and aspartate were also decreased. 5. Triperidol increased the rate of disappearance of U-(14)C-labelled glutamate, aspartate and glycine from the incubation medium, and altered the distribution of their metabolites between medium and tissue. 6. No appreciable effect of triperidol on [1-(14)C]galactose disappearance was found.

Amino Acids↗
PubMed1990

Effect of infused branched-chain amino acids on muscle and whole-body amino acid metabolism in man.

1. Using the forearm balance method, together with systemic infusions of L-[ring-2,6-3H]phenylalanine and L-[1-14C]leucine, we examined the effects of infused branched-chain amino acids on whole-body and skeletal muscle amino acid kinetics in 10 postabsorptive normal subjects; 10 control subjects received only saline. 2. Infusion of branched-chain amino acids caused a four-fold rise in arterial branched-chain amino acid levels and a two-fold rise in branched-chain keto acids; significant declines were observed in circulating levels of most other amino acids, including phenylalanine, which fell by 34%. Plasma insulin levels were unchanged from basal levels (8 +/- 1 mu-units/ml). 3. Whole-body phenylalanine flux, an index of proteolysis, was significantly suppressed by branched-chain amino acid infusion (P less than 0.002), and forearm phenylalanine production was also inhibited (P less than 0.03). With branched-chain amino acid infusion total leucine flux rose, with marked increments in both oxidative and non-oxidative leucine disposal (P less than 0.001). Proteolysis, as measured by endogenous leucine production, showed a modest 12% decrease, although this was not significant when compared with saline controls. The net forearm balance of leucine and other branched-chain amino acids changed from a basal net output to a marked net uptake (P less than 0.001) during branched-chain amino acid infusion, with significant stimulation of local leucine disposal. Despite the rise in whole-body non-oxidative leucine disposal, and in forearm leucine uptake and disposal, forearm phenylalanine disposal, an index of muscle protein synthesis, was not stimulated by infusion of branched-chain amino acids. 4. The results suggest that in normal man branched-chain amino acid infusion suppresses skeletal muscle proteolysis independently of any rise of plasma insulin. Muscle branched-chain amino acid uptake rose dramatically in the absence of any apparent increase in muscle protein synthesis, as measured by phenylalanine disposal, or in branched-chain keto acid release. Thus, an increase in muscle branched-chain amino acid concentrations and/or local branched-chain amino acid oxidation must account for the increased disposal of branched-chain amino acids.

Adolescent↗