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PubMed2006

Proteomic characterization of the effects of clofibrate on protein expression in rat liver.

Clofibrate is a peroxisome proliferator known to induce liver tumours in rats. A proteomics study was conducted to provide new insights into the molecular mechanisms of clofibrate-induced non-genotoxic hepatocarcinogenesis. Rats were treated with 250 mg/kg day clofibrate orally and sacrificed after 7 days. Proteins extracted from the liver were analysed by 2-DE using DIGE technology. The protein identification performed by MS showed that clofibrate induced up-regulation of 77 proteins and down-regulation of 27 proteins. The highest expression ratios corresponded to proteins involved in a series of biochemical pathways such as lipid metabolism, fatty acid metabolism, amino acid metabolism, protein metabolism, citric acid cycle, xenobiotic detoxification and oxidative stress. Proteins implicated in cell proliferation and apoptosis, such as prohibitin, 10-formyl tetrahydrofolate dehydrogenase, senescence marker protein-30, pyridoxine 5'-phosphate oxidase and vimentin, were also identified as being regulated. These results provide leads for further investigations into the molecular mechanisms of liver tumours induced by clofibrate. In addition, MS results showed that a series of regulated proteins were detected as several spots corresponding to different pI and/or M(r). Differential effects on those variants could result from specific PTM and could be a specific molecular signature of the clofibrate-induced protein expression modulation in rat liver.

Amino Acid Sequence↗
PubMed1998

An evaluation of postabsorptive protein and amino acid metabolism in the lactating dairy cow.

The current protein system utilized in the US was formulated in 1985 with minor modifications in 1989 and has gained widespread acceptance. However, some of the assumptions that were adopted by the National Research Council (NRC) appear to be inconsistent with observational data. The marginal efficiency of conversion of absorbed protein to milk protein was assumed by NRC to be 70% until the requirement for absorbed protein was met and was 0% thereafter. The mean marginal efficiency observed for abomasal casein infusions reported in the literature and collected at the Purina Mills Research Center was 21%. Sorting the data into protein-sufficient and protein-deficient classes did not support the assumptions of 70% marginal efficiency in a deficient state and 0% marginal efficiency in the sufficient state. Analyses of nitrogen balance data and abomasal flow data and the work of Van Straalen et al. (77) indicated that energy status of the animal plays a role in determining the response to absorbed protein. Such a consideration was not included in the NRC model. The adoption of equations that describe metabolism at the organ level as opposed to the animal level would allow direct use of organ level data for parameterization and may provide better predictions. Simple representations of digestion and absorption, splanchnic metabolism, and mammary metabolism of amino acids or protein in aggregate are described. These representations could be used to improve the current system and could serve as a bridge to adoption of more complex models.

Amino Acids↗
PubMed1985

A review of the clinical presentation and laboratory findings in two uncommon hereditary disorders of sulfur amino acid metabolism, beta-mercaptolactate cysteine disulfideuria and sulfite oxidase deficiency.

Two hereditary disorders of sulfur amino acid metabolism, beta-mercaptolactate-cysteine disulfideuria and sulfite oxidase deficiency, were described twenty years ago. Other examples of these disorders have been limited to about 5 of each in the world literature since then. Reasons for the apparent rarity of these conditions are discussed and the analytical procedures to identify them are reviewed. The detection of the first depends on the positive result of a cyanide-nitroprusside test followed by positive identification of the specific mixed disulfide. The enzyme mercaptopyruvate sulfur transferase has been shown to be deficient. In the second disorder of sulfite oxidase deficiency, the clinical presentation with progressive dystonia and dislocated lenses in an infant should suggest further laboratory investigations for this disorder which would not be detected by conventional laboratory screening procedures. Laboratory diagnosis can be obtained by use of the Merckoquant sulfite test on a fresh urine sample. Quantitative thiosulfate and taurine measurements can also be made. Positive identification of the specific amino acid S-sulfo-L-cysteine should also be made. The enzyme sulfite oxidase is missing from such organs as liver, kidney and brain. This latter condition may also be associated with xanthinuria. For this combined disorder of sulfite oxidase and xanthine oxidase, a deficiency of a molybdenum-containing cofactor has been demonstrated.

Adolescent↗
PubMed1990

Protein and amino acid metabolism with reference to aging and the elderly.

In this short review, selected aspects of body protein and amino-acid metabolism during aging in human subjects have been explored. There is a progressive diminution of total body protein with aging, due largely to a loss of skeletal muscle protein. These changes are accompanied by a shift in the overall pattern of whole body protein synthesis and breakdown, with muscle mass estimated to account for about 30 percent of whole body protein turnover in the young adult, as compared with a lower value of 20 percent or less in elderly subjects. There is no evidence that the loss of muscle protein is related to a reduced "amino acid tolerance" to insulin, since leucine-insulin metabolic relationships appear to remain intact during advancing adult age. However, because skeletal muscle mass plays an important role in the response to body protein and amino-acid metabolism to stress, such as that due to infection or trauma, this decline in the contribution of muscle to total body protein metabolism might be a factor responsible for the reduced ability of older people to withstand such unfavorable circumstances. Recent observations on the importance of muscle as a source of glutamine that is essential for immune cell function support this contention. The dietary requirements for individual essential and for total protein are limited and often contradictory (see, for example, Young, et al, 1982). However, elderly individuals are more likely to be affected by various biological, environmental and social factors, which would generally increase protein and amino acid needs above those for younger adults. Thus, in practice, the protein needs in the elderly are likely to be higher than those in the young. The decline in energy intake, together with its possible consequences for reducing the efficiency of dietary protein utilization, also will tend to increase the protein need for elderly subjects, relative to that for physically more active young adults. Until more data become available, it is recommended, for food planning purposes, that an appropriate protein allowance would be about 15 percent of the total energy intake, for mixed food protein sources characteristic of the diets of industrialized countries. Epidemiological surveys of the protein nutritional status of healthy, free living elderly subjects and of institutionalized individuals without clinically apparent terminal or wasting illness are consistent with this recommendation.

Aged↗
PubMed1989

Comparative effects of tumour necrosis factor-alpha (cachectin), interleukin-1-beta and tumour growth on amino acid metabolism in the rat in vivo. Absorption and tissue uptake of alpha-amino[1-14C]isobutyrate.

The effects of acute administration of either tumour necrosis factor-alpha (cachectin) (TNF) or interleukin-1-beta (IL-1), or of tumour growth (Walker-256 carcinosarcoma), on blood amino acid concentrations and tissue alpha-amino[1-14C]isobutyrate (AIB) uptake in virgin and lactating rats were compared. Both monokines decreased the blood concentrations of those amino acids (serine, glycine, alanine and proline) transported via the A system. Tumour growth decreased the blood concentrations of serine, proline and histidine, whereas the concentrations of glutamine and leucine were increased. IL-1 decreased the intestinal absorption of AIB in all groups studied; TNF or tumour growth had no effect. Tissue AIB uptake was increased (1.5-2.5-fold) in liver, whereas it was decreased in heart and skeletal muscle of the three treatment groups (except skeletal muscle of the IL-1-treated rats). Lactating rats had lower hepatic uptake of AIB compared with livers of virgin rats. IL-1 increased the hepatic uptake of AIB in lactating rats, but not to the values seen in virgin rats treated with IL-1; there was no effect of the cytokine on muscle or mammary-gland uptake. In adrenalectomized rats, the stimulatory effect of IL-1 on hepatic AIB uptake was diminished, whereas that of TNF still persisted. IL-1 caused a marked decrease of AIB uptake in muscle and heart of adrenalectomized rats, which was accompanied by an increase in the blood concentrations of branched-chain amino acids. These effects did not occur with TNF. It is concluded that the effects of the cytokines on tissue amino acid metabolism may depend on a differential endocrine response involving glucagon and/or glucocorticoids.

Absorption↗
PubMed1979

[Penicillin biosynthesis and amino acid metabolism in Penicillium chrysogenum in experiments with washed mycelium].

The study of the amino acid metabolism in Penicillium chrysogenum with the use of washed mycelium showed that the amount of the free intracellular amino acids significantly decreased during the process of penicillin production. Still, such a decrease did not cover the nitrogen requirements of the culture for the antibiotic synthesis and mobilization of the protein nitrogen took place. By the end of the process the amount of the protein nitrogen markedly decreased. At the same time alpha-amino nitrogen was absent in the fermentation broth filtrate. About 14 amino acids (including cysteine and valine) which participate in constriuction of the penicillin molecule nucleus were found in the amino acid poll. However, the amounts of cysteine and valine were not high and probably other free intracellular amino acids participated in their synthesis. It was shown that one of the limiting factors in the process of penicillin biosynthesis was synthesis of cysteine, a sulphur-containing amino acid which is one of the precursors of the antibiotic molecule nucleus.

Amino Acids↗
PubMed1989

[Pulmonary encephalopathy and disturbance in amino acids metabolism].

18 kinds of serum free amino acids (SFAAs) were determined in 35 patients suffering from cor pulmonale (CP) with acute exacerbation of chronic obstructive pulmonary disease (COPD). We found that the branched-chain AAs/aromatic AAs ratio (BCAAs/AAAs) was smaller in patients with pulmonary encephalopathy (PE) than those with respiratory failure (RF) only. For the PE patients, this ratio was still smaller during unconscious period than during conscious period. Some SFAAs related to neurotransmitters were also altered during unconscious period. However, there was no significant difference between CP patients with simple RF and those without RF. When RF was controlled, the SFAAs remained unchanged. The above results suggested that disturbance in neutral AAs metabolism participates in the mechanism of PE formation.

Aged↗
PubMed1984

Amino acid metabolism in the brain with convulsive disorders. Part 3: Free amino acid patterns in cerebrospinal fluid in infants and children with convulsive disorders.

Free amino acid patterns of cerebrospinal fluid in infants and children with various types of convulsive disorders were compared with those in age-matched normal subjects. The total free amino levels in Lennox syndrome were higher than the normal values, and those in infantile spasms controlled by ACTH were higher than those in uncontrolled infantile spasms. Although the levels of only one or two amino acids in tonic-clonic seizure, focal seizure and febrile seizure were higher or lower than those of the controls, the levels of 8 amino acids in infantile spasms were lower and those of 10 amino acids in Lennox syndrome were generally higher compared to the controls. Among amino acids in CSF of children with tonic-clonic seizure, infantile spasms or Lennox syndrome, only the ornithine level was commonly lower than that of the controls. After the treatment, in tonic-clonic seizure, the levels of taurine, asparagine and glycine were increased, and in infantile spasms, those of asparagine, glutamine, glycine, alanine, phenylalanine, lysine and arginine were increased while that of taurine was decreased. These results suggest that each type of convulsive disorder shows the specific amino acid pattern, and the effects of anticonvulsants may be partially understood through the changes of the free amino acid patterns in the brain.

Adolescent↗
PubMed1984

Ammonium ions suppress the amino acid metabolism involved in the biosynthesis of protylonolide in a mutant of Streptomyces fradiae.

Protylonolide is a lactonic precursor of tylosin aglycone, produced by a mutant of Streptomyces fradiae. It originates from n-butyrate, propionate and acetate units. Studies were carried out using a protylonolide-producing mutant on the correlation between protylonolide biosynthesis, regulation by NH4+ and amino acid metabolism. Protylonolide production decreased in a defined medium containing high levels of NH4+, but was restored by adding lower fatty acids expected to serve as precursors of protylonolide biosynthesis. Resting cell studies demonstrated that 14C-labeled valine, threonine, leucine, isoleucine and alanine, but not lysine, were efficiently incorporated into protylonolide, indicating that these amino acids are metabolized to lower fatty acids. The incorporation of amino acids into protylonolide was reduced when the mutant strain was previously grown under high NH4+ conditions. We suggest that NH4+ suppresses the relevant amino acid metabolism, thereby reducing protylonolide formation.

Amino Acids↗
PubMed1998

Abnormal amino acid metabolism in patients with early stage Alzheimer dementia.

Plasma levels of several amino acids were studied in 14 patients with early stage probable Alzheimer's disease (AD) and 17 age-matched controls. In the AD patients a possible relationship between amino acid levels and behavioural symptomatology was also investigated. We found significantly reduced levels of tryptophan and methionine in plasma samples from the AD patients compared to the control subjects. Moreover, plasma tyrosine/large neutral amino acids (LNAA) ratio and the ratio of plasma taurine and the product of the plasma levels of methionine and serine (TSM-ratio) were significantly increased in the AD patients in comparison with the controls. However, no difference was found in plasma tryptophan/LNAA ratio and in homocysteine levels between both groups. Concerning the behavioural symptomatology no significant correlation was found between the Reisberg Behave AD scale and plasma amino acid levels or ratios. The reported findings suggest that abnormal amino acid metabolism is present in the early stages of AD. We hypothesize that this abnormality could play a role in the pathogenesis of behavioural changes occurring in later stages of AD.

Aged↗
PubMed2002

A study on the estimation of sulfur-containing amino acid metabolism by the determination of urinary sulfate and taurine.

Sulfate and taurine are major end products of sulfur-containing amino acid metabolism in mammals including humans, and they are excreted in urine. Average excretions micromol/mg of creatinine) in the morning urine of 58 female college students were: total (free plus ester) sulfate (a). 12.53 +/- 3.85; free sulfate, 11.57 +/- 3.69; taurine, 0.78 +/- 0.53. Ratio of total sulfate and taurine was 10 : 0.6. Regression lines obtained by plotting total sulfate, free sulfate, or total sulfate plus taurine against urea have shown that the former excretions are significantly correlated with urea excretion. Excretion of total sulfate at zero point of urea excretion (b). was 5.30, which corresponded to 42.3% of average excretion (12.53) and was assumed to be derived from dietary sulfate. The difference 7.23 (a - b) seemed to be derived from sulfur-containing amino acids. It was pointed out that the difference of average sulfate excretion and sulfate excretion at zero urea excretion, namely a - b, was appropriate for the metabolic index of sulfur-containing amino acids of the group examined. As free sulfate constituted 92.3% of total sulfate, excretion of ester sulfate was at a constant level, and that of taurine was not significantly correlated with urea excretion, the value of free sulfate corresponding to the value a - b of total sulfate mentioned above seemed to be a reliable and convenient index in the assessment of sulfur-containing amino acid metabolism.

Adolescent↗
PubMed1985

Abnormal amino acid metabolism in mutants of Saccharomyces cerevisiae affected in the initiation of sporulation.

Amino acid metabolism was examined during sporulation in a wild-type strain of Saccharomyces cerevisiae and in a mutant homozygous for the spd1 mutation (derepression of sporulation). In the wild-type initiation of sporulation involves a rise in intracellular glutamate. In the derepressed mutant there was no further increase of intracellular glutamate: glutamate was already present at a greater concentration than in the wild-type. These elevated glutamate levels are apparently due to reduction in the activity of 2-oxoglutarate dehydrogenase. One consequence of the elevated glutamate levels in diploids homozygous for the spd1 mutation is the production of considerable amounts of glycyl-L-proline, glutathione and saccharopine.

Amino Acids↗