Body condition prepartum and its association with term placentome nutrient transporters, one‑carbon metabolism pathway activity, and intermediate metabolites in Holstein cows

We investigated linkages among BCS prior to calving and placentome concentrations of metabolites, proteins in one‑carbon metabolism (OCM) and protein synthesis, and nutrient transport. Multiparous Holstein cows retrospectively divided by prepartal BCS at -4 weeks relative to parturition into high BCS (HBCS = 3.58 ± 0.23; n = 9) or normal BCS (NBCS = 3.02 ± 0.17; n = 13) were used. BCS was assessed using a 5-point scale (1 = thin, 5 = fat). Four placentomes per cow were collected at delivery and frozen in liquid N. Western blotting was used for protein abundance. Cystathionine-β-synthase (CBS) and betaine-homocysteine-S-methyltransferase (BHMT) activity were measured via 14C assays. Amino acids (AA) and metabolites in OCM were measured by liquid chromatography mass spectrometry (LC-MS). Compared with NBCS cows, the cellular stress sensor p-eIF2α was more than 2-fold greater (P = 0.04) in HBCS. Abundance of the AA-catabolism enzyme branched-chain α-ketoacid dehydrogenase complex was lower (P = 0.05) in HBCS cows. Although BHMT activity did not differ, greater concentration of betaine (P = 0.01) and lower (P = 0.05) concentration of dimethylglycine in HBCS cows suggested reduced flux through the methionine cycle. Despite a lack of difference in CBS activity, lower concentrations of cystathionine (P = 0.03) and hypotaurine (P = 0.04) along with lower cysteine and the tendency for lower total GSH (P = 0.10) in HBCS cows suggested a decrease in transsulfuration. Overall, associations between OCM in placentomes and BCS at calving exist. Identifying mechanisms responsible for these effects merits further research.

Differential response of methionine metabolism in two grain legumes, soybean and azuki bean, expressing a mutated form of Arabidopsis cystathionine γ-synthase

Methionine (Met) is a sulfur-containing amino acid that is essential in mammals and whose low abundance limits the nutritional value of grain legumes. Cystathionine γ-synthase (CGS) catalyzes the first committed step of Met biosynthesis, and the stability of its mRNA is autoregulated by the cytosolic concentration of S-adenosyl-l-methionine (SAM), a direct metabolite of Met. The mto1-1 mutant of Arabidopsis thaliana harbors a mutation in the AtCGS1 gene that renders the mRNA resistant to SAM-dependent degradation and therefore results in the accumulation of free Met to high levels in young leaves. To manipulate Met biosynthesis in soybean and azuki bean, we introduced the AtCGS1 mto1-1 gene into the two grain legumes under the control of a seed-specific glycinin gene promoter. Transgenic seeds of both species accumulated soluble Met to levels at least twice those apparent in control seeds. However, the increase in free Met did not result in an increase in total Met content of the transgenic seeds. In transgenic azuki bean seeds, the amount of cystathionine, the direct product of CGS, was markedly increased whereas the total content of Met was significantly decreased compared with control seeds. Similar changes were not detected in soybean. Our data suggest that the regulation of Met biosynthesis differs between soybean and azuki bean, and that the expression of AtCGS1 mto1-1 differentially affects the metabolic stability of sulfur amino acids and their metabolites in the two grain legumes.

Differential response of methionine metabolism in two grain legumes, soybean and azuki bean, expressing a mutated form of Arabidopsis cystathionine γ-synthase

Methionine (Met) is a sulfur-containing amino acid that is essential in mammals and whose low abundance limits the nutritional value of grain legumes. Cystathionine γ-synthase (CGS) catalyzes the first committed step of Met biosynthesis, and the stability of its mRNA is autoregulated by the cytosolic concentration of S-adenosyl-l-methionine (SAM), a direct metabolite of Met. The mto1-1 mutant of Arabidopsis thaliana harbors a mutation in the AtCGS1 gene that renders the mRNA resistant to SAM-dependent degradation and therefore results in the accumulation of free Met to high levels in young leaves. To manipulate Met biosynthesis in soybean and azuki bean, we introduced the AtCGS1 mto1-1 gene into the two grain legumes under the control of a seed-specific glycinin gene promoter. Transgenic seeds of both species accumulated soluble Met to levels at least twice those apparent in control seeds. However, the increase in free Met did not result in an increase in total Met content of the transgenic seeds. In transgenic azuki bean seeds, the amount of cystathionine, the direct product of CGS, was markedly increased whereas the total content of Met was significantly decreased compared with control seeds. Similar changes were not detected in soybean. Our data suggest that the regulation of Met biosynthesis differs between soybean and azuki bean, and that the expression of AtCGS1 mto1-1 differentially affects the metabolic stability of sulfur amino acids and their metabolites in the two grain legumes.

The role of amino acids in spina bifida

Our objective was to measure amniotic fluid amino acid concentrations in pregnant women diagnosed as having fetuses with spina bifida in the second trimester of pregnancy. Fifteen pregnant women who had fetuses with spina bifida detected by ultrasonography (spina bifida group) in the second trimester and 19 women who had abnormal triple screenings indicating an increased risk for Down's syndrome but had healthy fetuses (control group) were enrolled in the study. Amniotic fluid was obtained by amniocentesis. The chromosomal analysis of the study and control groups was normal. Levels of free amino acids were measured in amniotic fluid samples using EZ: fast kits (EZ: fast GC/FID free (physiological) amino acid kit) by gas chromatography (Focus GC AI 3000 Thermo Finnigan analyzer). The mean levels of alanine, cystathionine, cysteine, phenylalanine, tryptophane, and tyrosine amino acids were found to be significantly higher in fetuses of the control group than in the spina bifida group (p<0.05). The detection of significantly higher amino acid concentrations in the amniotic fluid of healthy fetuses suggests loss of amino acids from the fetus through the spinal cord may contribute to the etiology of spina bifida.

Standardless identification of selenocystathionine and its γ-glutamyl derivatives in monkeypot nuts by 3D liquid chromatography with ICP-MS detection followed by nanoHPLC–Q-TOF-MS/MS

A three-step chromatographic procedure using orthogonal separation mechanisms (size-exclusion, cation-exchange and ion-pairing reversed phase) was developed to purify three low molecular weight selenospecies, including the major compound, from the aqueous extract of monkeypot (Lecythis minor) nuts. The following reversed-phase nanoHPLC-electrospray Q-TOF-MS/MS allowed the formal standardless identification of selenocystathionine and two isoforms of gamma-glutamyl-selenocystathionine. This is the first MS and MS/MS-based formal evidence of the presence of these compounds in a biological sample.

Measurement of intracellular sulfur amino acid metabolism in humans

Methionine metabolism forms homocysteine via transmethylation. Homocysteine is either 1) condensed to form cystathionine, which is cleaved to form cysteine, or 2) remethylated back to methionine. Measuring this cycle with the use of isotopically labeled methionine tracers is problematic, because the tracer is infused into and measured from blood, whereas methionine metabolism occurs inside cells. Because plasma homocysteine and cystathionine arise from intracellular metabolism of methionine, plasma homocysteine and cystathionine enrichments can be used to define intracellular methionine enrichment during an infusion of labeled methionine. Eight healthy, postabsorptive volunteers were given a primed continuous infusion of [1-13C]methionine and [methyl-2H(3)]methionine for 8 h. Enrichments in plasma methionine, [13C]homocysteine and [13C]cystathionine were measured. In contrast to plasma methionine enrichments, the plasma [13C]homocysteine and [13C]cystathionine enrichments rose to plateau slowly (rate constant: 0.40 +/- 0.03 and 0.49 +/- 0.09 h(-1), respectively). The enrichment ratios of plasma [13C]homocysteine to [13C]methionine and [13C]cystathionine to [13C]methionine were 58 +/- 3 and 54 +/- 3%, respectively, demonstrating a large intracellular/extracellular partitioning of methionine. These values were used to correct methionine kinetics. The corrections increase previously reported rates of methionine kinetics by approximately 40%.

Is the increase in serum cystathionine levels in patients with liver cirrhosis a consequence of impaired homocysteine transsulfuration at the level of gamma-cystathionase?

BACKGROUND

It has been suggested that the major metabolic block in the methionine catabolic pathway in cirrhotics exists at the level of the enzyme S-adenosylmethionine synthetase because in previous studies using conventional amino-acid analyzers, no intermediates of transmethylation/transsulfuration were found to accumulate in plasma downstream of S-adenosylmethionine synthesis. We therefore measured serum concentration intermediates of methionine transmethylation/transsulfuration using an improved gas chromatography/mass spectrometry technique.

METHODS

Serum concentrations of methionine, homocysteine, cystathionine, N,N-dimethylglycine, N-methylglycine, methylmalonic acid, 2-methylcitric acid and alpha-aminobutyric acid were determined by gas chromatography/mass spectrometry in 108 consecutive patients with liver cirrhosis at Child stages A (mild cirrhosis, n = 27) and B/C (severe cirrhosis, n = 81), 18 outpatients with non-cirrhotic liver disease, and 55 healthy individuals.

RESULTS

Serum levels of methionine, N,N-dimethylglycine, N-methylglycine, cystathionine, and homocysteine were significantly higher in patients at Child stages B/C compared with those of healthy controls (P < 0.01), and they were also significantly higher than in patients with non-cirrhotic liver disease (P < 0.01 and P < 0.05 for homocysteine, respectively). They also correlated with the Child-Pugh score (P < 0.01). Homocysteine, cystathionine, N,N-dimethylglycine, N-methylglycine, methylmalonic acid, and 2-methylcitric acid correlated with serum creatinine. The mean cystathionine concentration was significantly higher in patients with creatinine > or = 1.4 mg/dl than in patients with normal creatinine values (P < 0.01). However, the differences between cirrhotics and healthy controls were still significant after correcting for creatinine.

CONCLUSIONS

Our data provides indirect evidence for two hitherto unrecognized alterations of methionine metabolism in cirrhotics, i.e. impairment of the transsulfuration of homocysteine at the level of cystathionine degradation and a shift in remethylation of homocysteine towards the betaine-homocysteine-methyltransferase reaction.

Detection of cystathionine ketimine and lanthionine ketimine in human brain

The sulfur containing imino acids cystathionine ketimine (CK) and lanthionine ketimine (LK) have been detected in the human brain by an HPLC procedure. The HPLC procedure takes advantage of the selective absorbance at 380 nm of the phenylisothiocyanate-ketimine adduct. Quantitation of cystathionine ketimine and lanthionine ketimine indicates a mean concentration (mean +/- SD, n = 4) of 2.3 +/- 0.8 nmol/g for CK and of 1.1 +/- 0.3 nmol/g for LK in four human cerebral cortex samples of neurosurgical source. The identification of these cyclic ketimine derivatives of L-cystathionine and L-lanthionine as normal human metabolites in human nervous tissue may have interesting metabolic and physiological implications.

Simultaneous determination of cystathionine and NAc-cystathionine using liquid chromatography atmospheric pressure chemical ionization mass spectrometry

A method for simultaneous determination of cystathionine and NAc-cystathionine in biological samples has been developed by using column liquid chromatography-mass spectrometry. The concentrations of cystathionine and NAc-cystathionine in urine, several tissues, and serum of propargylglycine-treated rats with experimental cystathioninuria were determined by scanning the [M + H]+ ions of each compound. The recoveries of authentic compounds were 95.69 +/- 4.44% (n = 10) for cystathionine and 91.59 +/- 5.26% (n = 10) for NAc-cystathionine after ion-exchange resin treatment. The contents of cystathionine and NAc-cystathionine in the urine of a patient with cystathioninuria were also measured. The results coincided well with those obtained using an amino acid analyzer.

Determination of sulphur amino acids by gas chromatography with flame photometric detection

A selective and sensitive method has been developed for the determination of sulphur amino acids by gas chromatography (GC). Sulphur amino acids were converted into their N(S)-isopropoxycarbonyl methyl ester derivatives and measured by GC with flame photometric detection using a DB-17 capillary column. The derivatives were sufficiently volatile and stable to give single symmetrical peaks. The detection limits of sulphur amino acids were ca. 0.5-1 pmol per injection, and the calibration curves were linear in the range 0.5-10 nmol for each sulphur amino acid. This method was successfully applied to small urine samples without prior clean-up, and sulphur amino acids in these samples could be analysed without any influence from coexisting substances. Overall recoveries of sulphur amino acids added to urine samples were 85-113%. The analytical results of free sulphur amino acid contents in urine samples of normal subjects are presented.

The simultaneous determination of oxidized and reduced glutathiones in liver tissue by ion pairing reverse phase high performance liquid chromatography with a coulometric electrochemical detector

The oxidized (GSSG) and reduced (GSH) forms of glutathione were quantified simultaneously in rat liver tissues by ion-pairing reverse phase high pressure liquid chromatography coupled to a coulometric electrochemical detector (HPLC-EC). Other biological thiols namely cysteine, cystathionine, homocysteine and methionine were shown to be well resolved from the glutathiones. Standard curves for GSH and GSSG were linear over the range of glutathione concentrations found in biological tissues with a correlation coefficient (r) greater than 0.999. Rat liver tissue content of GSH (16.96 +/- 4.29, n = 5) and GSSG (0.467 +/- 0.188 n = 5) found in this study are similar to results reported by other investigators. This method is also applicable to determine glutathione levels in rat bile samples. The advantages and disadvantages of employing coulometric over amperometric, as well as precautions in establishing HPLC-EC for the detection of oxidized and reduced glutathiones is discussed.

Selective metabolism of L-serine by Moniliformis (Acanthocephala) in vitro

In a series of in vitro experiments, adult male and female Moniliformis dubius were incubated at pH 6.88 and 37 degrees C for 3 h in a 2.5 mM solution of 18 amino acids. Fifteen of these were absorbed slightly from the medium, but L-serine was almost completely absorbed while the concentrations of glycine and alanine in the medium increased during the course of the incubation. By using L-[U-14C]serine, it was found that labelled ethanol and CO2 were the main end-products of metabolism excreted into the medium, with smaller amounts of labelled alanine, lactate and acetate. Small amounts of cystathionine with high specific radioactivity were found in extracts of the worms at the end of incubation, together with other radioactive metabolites including glucose, ethanol, lactate, succinate, malate, serine, glycine and alanine. Ammonia was found to be an excretory product of the amino acid metabolism of M. dubius. Possible metabolic pathways and suggestions for the significance of serine metabolism in this parasite are discussed.

[Developmental changes in taurine and other sulfur-containing amino acid concentrations in fetal and neonatal rats]

The concentrations of taurine and other sulfur-containing amino acids in the fetal, neonatal and maternal liver, placenta, and whole fetal body between the 15th day of gestation and the 14th day after birth were determined using an automatic amino acid analyzer. In the fetal liver and placenta, the taurine concentration was the highest among all ninhydrin positive compounds. In these tissues the concentration of taurine increased significantly with the number of gestational days. Moreover, the total amount of taurine per fetus increased markedly up to term after the 15th day of gestation, and reached almost the same value as the total amount for adult rat liver. A striking difference in the changes in taurine concentrations during gestation between the fetal and maternal rat liver was observed: In contrast to the increase in the fetal liver, a significant decrease in the maternal liver was observed near term. But in these organs, no significant change in methionine, cystathionine and cysteine concentrations was observed during the perinatal period. These results suggest that taurine is supplied to the developing rat fetus from the maternal liver throughout gestation.

Determination of cystathionine in rat tissues using isotachophoresis

A method for measurement of cystathionine in biological samples has been developed by using an isotachophoretic analyzer. The determination of the amount of cystathionine was carried out by measuring a zone length of cystathionine in isotachophoresis. The amount of cystathionine in brains of normal rats determined by using this method was 0.084 +/- 0.023 mumol/g. This value agreed well with earlier reports. The amount of cystathionine in rats with experimental cystathioninuria was determined in several tissues. The results determined by using this method for the determination of cystathionine in the rat tissues agreed well with the results obtained by using an amino acid analyzer.

Free amino acid pools of rodent mammary tumors

Intracellular pools of free amino acids were compared individually in mammary tumors of Wistar Furth and Sprague-Dawley rats and C3H and DBA/2 mice. Of 11 transplantable and 7,12-dimethylbenz[a]anthracene-induced adenocarcinomas of the rat, all nonmetastasizing tumors could be distinguished from metastasizing tumors by the accumulation of high glutamine pools and significant-to-high cystathionine pools. In primary mammary tumors of C3H mice and transplanted mammary tumors of DBA/2 mice, intracellular free arginine was frequently below that of the circulating plasma level and approached that in the arginine-destroying organ, the liver. Arginine pool depletion was also noted in normal mammary tissue, particularly in the actively lactating mouse. Individual rat or mouse mammary tumors also contained high levels of taurine, beta-alanine, and gamma-aminobutyric acid, which, like cystathionine, are distinctive for or are enriched in neural tissue. None of these pool enrichments were characteristic of normal rat or mouse mammary tissue. Free hydroxyproline was low in primary induced rat mammary tumors and higher in transplanted mammary tumors and in normal lactating mammary glands, particularly in the mouse. In contrast, the hydroxyproline residues of collagen, taken as an index of mesenchymal cell contribution, were very low in all tumors.

[Effect of stimulating pharmacological agents on the content of L-cystathionine in the rabbit brain tissues]

Concentration of L-cystathionine was distinctly increased in rabbit brain within the period of maximal action of drugs, stimulating the central nervous system (phenamine, strychnine corasole). A distinct decrease in content of L-cystathionine was observed within one hour after the administration of strychnine and corasole.

Amino acids in human epileptogenic foci

Free amino compounds were measured in 16 rapidly frozen epileptogenic foci excised from temporal or frontal cortex of nine patients with focal epilepsy, and in single cortical biopsy specimens obtained from 16 nonepileptic patients. Unlike the findings of a previous study, glutamic and aspartic acids were not diminished in the foci, nor was there a decrease in gamma-aminobutyric acid (GABA) or taurine levels. Glycine content was markedly elevated in two of 16 epileptogenic foci. These results do not suggest that deficiencies of GABA or of taurine, amino acids that may act physiologically as inhibitory neurotransmitters or modulators of inhibition, are causes of focal epilepsy, nor do they provide a logical basis for clinical trials of taurine in treatment of human epilepsy.