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© 2006 The American Society for Nutrition J. Nutr. 136:1716S-1721S, June 2006

Supplement: 5th Amino Acid Assessment Workshop: Session III

Screening of Toxicity Biomarkers for Methionine Excess in Rats1

Sakino Toue, Riho Kodama, Michiko Amao, Yasuko Kawamata, Takeshi Kimura and Ryosei Sakai2

Ajinomoto Co., Inc., Institute of Life Sciences, Kawasaki, Japan

2 To whom correspondence should be addressed. E-mail: ryosei_sakai{at}ajinomoto.com.


   ABSTRACT
TOP
 ABSTRACT
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 LITERATURE CITED
 
Although many animal studies have reported that dietary excess of methionine causes toxic changes including growth suppression and hemolytic anemia, the biochemical mechanism and biomarkers for methionine toxicity have not been well elucidated. The present study aimed to identify toxicity biomarkers from plasma metabolites in rats fed excessive methionine. Young growing rats were fed graded doses of additional methionine for 2 wk. Cluster analysis of multivariate correlations was performed on the physiological and toxicity variables with plasma metabolites detected by GC/MS, amino acid analyzer, and thiol-specific analysis. Indicative variables for hemolysis such as splenic nonheme iron content and plasma bilirubin were grouped in the same cluster as many methionine metabolites. Homocysteine and some undefined metabolites in this cluster were found to be strong discriminators between nontoxic and toxic levels of methionine intake. Product-to-precursor ratios of each methionine metabolite demonstrated that excessive methionine intake caused a marked decrease only in the ratio of cystathionine to homocysteine, suggesting that metabolism from homocysteine to cystathionine would be rate limiting in the disposal of excessive methionine. Collectively from these results, homocysteine appeared to be the most plausible biomarker to assess methionine excess as a surrogate marker both for toxicity and for setting a metabolic upper limit.

KEY WORDS: • amino acid • dietary reference intake • tolerable upper level • acceptable daily intake • adequate intake

Methionine is essential for maintaining proper growth and development in mammals, and its supplementation in domestic animals, such as chicks and pigs, contributes to better production efficacy (1–4). Supplementation of too much methionine, however, causes various toxic changes including suppression of feed intake and growth (2,5,6). Methionine toxicity is more pronounced than the toxicity of other amino acids because optimal intake levels of methionine are narrower than the others; 2% of additional methionine in the diet generally reduces rat growth, whereas 10% of additional leucine does not (2,7,8). Characteristic features of excessive methionine intake also differ from those of the others. Excessive intake of methionine causes typical hematological changes: excess promotes methemoglobin accumulation and Heinz-body formation in erythrocytes and causes morphological changes in the erythrocytic membrane, which leads to hemolytic anemia and to morphological changes such as darkening and enlargement of the spleen, erythrocyte accumulation in sinusoids, and hemosiderin deposition in the spleen (7,9–12).

Methionine itself does not seem to be directly responsible for its toxicity because no adverse symptoms are observed in patients with extremely high plasma levels of methionine (hypermethioninemia) secondary to inborn errors of metabolism (13). Thus, it appears that metabolites in the normal catabolic pathways (Fig. 1) or abnormal metabolites arising from the overloading of certain metabolic pathways might be responsible for toxicity. Homocysteine might be a "toxic metabolite" because toxicities of homocysteine both in vivo and in vitro have been reported previously (14–16) and because methionine intake has been shown to raise plasma homocysteine concentrations (17). 3-Methylthiopropionate (3MTP), one of the metabolites in the transamination pathway, is also a candidate because its addition to the diet causes similar hematological changes in rats to those in animals fed excessive methionine (18) and because downstream metabolites of 3MTP, such as methanethiol, hydrogen sulfide (H2S), and formate, are highly toxic (19). Another candidate is S-adenosylmethionine (SAM), one of the most important methyl donors for 1-carbon metabolism: the hepatic content of SAM is increased by methionine load, and the increase is prevented by glycine supplementation, which is known to alleviate methionine toxicity (20). Although there are several candidates for the "toxic metabolite," the biochemical mechanisms underlying methionine toxicity remain controversial, and biomarkers for the toxicity have yet to be elucidated.


Figure 1
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  		FIGURE 1  Methionine metabolism. The transmethylation pathway, metabolic processes from methionine to homocysteine via S-adenosylmethionine (SAM) and S-adenosylhomocysteine, plays a crucial role in single-carbon metabolism as SAM is an important methyl donor. Homocysteine is recycled to methionine through a remethylation process or catabolized to cysteine via cystathionine through an irreversible transsulfuration pathway. An alternative metabolism is the transamination pathway, in which 2-keto-4-methylthiobutyrate, a deaminated product of methionine, is catabolized to 3-methylthiopropionate (3MTP) via an irreversible decarboxylation process.

 
The dietary requirement for methionine has been assessed using various methods, and a revision of the dietary reference intake (DRI) has been made (21). However, the tolerable upper limit (UL) has not been set because of the lack of suitable data. In order to use a metabolic and toxicokinetic approach to the risk assessment of methionine excess, the identification of the "toxic metabolite" that is responsible for toxicity, or biomarkers that correlate well with toxicity, is necessary (22–24). We have developed analytic methods based on cluster analysis of multivariate correlations (CAMC) that could be used to identify metabolite profiles that correlate with toxicity endpoints (25). We have reported on the use of CAMC on GC/MS metabolic profiling data to identify potential candidate metabolites for the adverse effects of feeding excess leucine to rats (8).

In the present study, we aimed to identify biomarkers for methionine toxicity using the above strategy from plasma metabolites in rats fed excessive methionine.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 LITERATURE CITED
 
    Animals. The study received prior approval from Ajinomoto's Institutional Animal Care and Use Committee. Male Fischer rats (F-344, 5 wk old) purchased from Charles River Japan were maintained in a controlled condition of 12-h light (0700 to 1900), 12-h dark, at 23 ± 1°C and at 55 ± 10% humidity. The animals were housed individually in stainless metabolic cages and had free access to tap water and purified diets, based on the AIN-93G composition with some modification, for 1 wk (26). Groups of 9 rats were then given basal modified AIN-93G or the experimental diets containing graded dosage of crystallized L-methionine (0.3, 0.6, 1.2, and 2.4% by weight in the diet, corresponding to 1, 2, 4, and 7.7% of total N intake, respectively) in place of the cornstarch. On day 14 of the experimental diets, the diet was removed in the morning (0900), and then 24-h urine samples were collected. In the afternoon (1330 to 1500), the rats were anesthetized by ether for autopsy and for the collection of blood from the inferior vena cava. Plasma was separated using EDTA or heparin-Na as anticoagulant for metabolite analysis and biochemical analysis, respectively.

    Measurements of toxicity variables. Plasma biochemical parameters [the activities of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), creatine phosphokinase (CPK), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), total birilubin (T-BIL), phospholipid (PL), total cholesterol (T-CHO), triglyceride (TG), glucose, total protein (TP), blood urea nitrogen (BUN), creatine (CRE), Ca, Na, K, Cl, and inorganic phosphate (IP)] were measured using TBA-120FR biochemistry automatic analyzer (Toshiba, Japan). Whole-blood ammonia was quantified using Fuji Drychem 3030 analyzer (Fuji Medical Systems) immediately after the blood collection.

Hematological variables [red blood cell count (RBC), hematocrit (Ht), hemoglobin (Hb), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), red cell distribution width (RDW), hemoglobin concentration distribution width (HDW), platelet count (PLt), mean platelet volume (MPV), white blood cell count (WBC), and differential count of leukocytes (basophils, eosinophils, neutrophils, lymphocytes, monocytes, large unstained cells)] were measured by H1E hematology analyzer (Technicon).

Urinary Ca concentration was quantified by the o-cresolphthalein complexone (OCPC) method, and Ca excretion was expressed as the percentage of Ca intake. Aliquots of spleen were homogenized in distilled water, and nonheme iron in the supernatant was determined by measuring the optical density (490 nm) of the colored complex formed by Fe(II) with 1 µmol/L o-phenanthroline (27).

    Amino acid analysis. Amino acid concentrations in the plasma and urine samples were measured by an automatic amino acid analyzer (L-8800, Hitachi). Briefly, the samples were mixed with 2 volumes of 5% trichloroacetic acid (TCA) and centrifuged to remove protein. Amino acids separated by cation-exchange chromatography were detected spectrophotometrically after postcolumn reaction with ninhydrin reagent.

    Thiol compound analysis. Thiol compounds in the plasma were measured by HPLC using SBD-F (ammonium 7-fluoro-2-oxa-1,3-diazole-4-sulfonate) derivatization (within-batch precision 2.2%) as reported previously (28). Briefly, the plasma samples were deproteinized with 1 volume of 10% TCA containing 1 mmol/L EDTA. The supernatants were neutralized and incubated with 2 mmol/L tri-n-butylphosphine for 10 min at room temperature to reduce disulfide bonds. The specimens were then incubated in the presence of 5 mmol/L SBD-F at 60°C for 20 min. Thiol compounds were separated by HPLC using a µBondapak C18 column and quantified using a Shimadzu RF-10AXL fluorescence detector (Shimadzu).

    Preparation for GC/MS analysis. Plasma samples were mixed with 5 volumes of ethanol to precipitate protein, and the supernatant was dried under vacuum. The samples were dissolved in water, and organic acids were separated as ethyl acetate extracts (fraction A). The water phases of ethyl acetate extraction were applied to 1 mL bed volume of a cation-exchange column (Dowex 50Wx8, H+ form; Bio-Rad). Cation-binding metabolites were eluted with 3mol/L ammonia solution (fraction B). Both fractions A and B were dried under vacuum, dissolved in 100 µL of trimethylsilylation reagent mixture [100:1:100, by vol. of bis(trimethylsilyl)trifluoroacetamide, trimethylchlorosilane and pyridine; Sigma-Aldrich], and placed at room temperature for over 3 h before GC/MS analysis.

    GC/MS analysis. A Hewlett-Packard GC/MS system consisting of a Model 6890N gas chromatography equipped with HP-5MS column (30 m x 0.25 mm I.D., Hewlett Packard) and a Model 5973N mass spectrometer was used for the analysis. The GC temperature was increased from 60°C to 280°C at a rate of 5°C/min. Positive ions generated by electron impact ionization were monitored by SCAN mode (m/z 50–800) for metabolic profiling.

    Statistical analysis. Statistical significance versus basal control group was determined by Dunnett or Tukey test following an ANOVA for multiple comparisons. JMP version 5.1.2 (SAS Institute) was used for Cluster Analysis of Multivariate Correlations (CAMC).


   RESULTS
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 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 LITERATURE CITED
 
    General physiological and toxicological variables. The results of excessive methionine ingestion on general physiological and toxicological parameters that showed statistically significant differences with the control group parameters are summarized in Table 1. More than 1.2% of additional methionine reduced both food intake and body weight gain. Various changes indicating anemia, such as decreases in RBC, Hb, and Ht, were observed in rats fed 2.4% of additional methionine, as have been reported previously. Plasma T-BIL, one of the indicators for heme breakdown, was increased by feeding 2.4% of additional methionine. Splenic nonheme iron content was elevated by intakes of additional methionine at and above 1.2% and was accompanied by splenic enlargement at 2.4%, indicating acceleration of hemolysis in the spleen. Histological changes in the spleen such as increased hemosiderin deposition in phagocytes and accumulation of erythrocytes in sinusoids, indicators for increased hemolysis, were also evident in rats fed 2.4% of additional methionine (data not shown). Methionine addition of 1.2% or more increased HDW and decreased MCV and MCH, indicating changes of size in certain erythrocyte subpopulations.


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  		TABLE 1 Physiological and toxicity variables in male Fischer F-344 rats fed additional methionine1

 
Total cholesterol and phospholipids increased slightly but significantly in rats fed 0.3% or more additional methionine. Most of the other changes including hematological ones and those in plasma biochemical variables and organ weight were observed in the 1.2 and 2.4% methionine groups.

    Multivariate analysis of plasma metabolites and toxicity variables. More than 2000 metabolite peaks were detected in the profiling of plasma metabolites by GC/MS analysis. Amino acid analyzer and SH-specific analysis enabled the detection of 41 amino acids and 4 thiol compounds in the plasma. A total of 166 metabolites showed concentrations that were significantly affected by methionine.

The selected metabolites were used for cluster analysis of multivariate correlations together with toxicity variables that showed significant changes with additional methionine intake (Table 1). Indicators for anemia (Hb, Ht, and MCH), which decreased with methionine load, were grouped in the same cluster with food intake and body weight gain (Cluster 2 in Fig. 2). RBC and MCV, which also decreased with methionine addition, were grouped in another cluster (Cluster 1) closely related to Cluster 2. Variables increased by methionine, such as T-CHO, PL, BUN, urinary Ca excretion, testis weight per body weight, and Cl, were segmented in individual clusters. Interestingly, indicative variables for hemolysis or anemia, such as nonheme iron content in the spleen, spleen weight per body weight, T-BIL, and HDW, which increased with additional methionine, were grouped in a single cluster (Cluster 4 in Fig. 2). Cluster 4 contained several methionine metabolites [cysteine (including cystine), homocysteine (including homocystine), cystathionine, sarcosine, and methionine], 2 lysine metabolites ({alpha}-aminoadipate and piperidine carboxylate), and several unidentified metabolites detected by GC-MS (Fig. 3). Homocysteine, cystathionine, and unidentified peak Paa477 were the metabolites that were best at discriminating between nontoxic and toxic levels of methionine (i.e., 1.2% or more) in relation to hemolysis in the spleen. The other thiol compound, such as glutathione and cysteinylglycine, showed no correlation with methionine toxicity.


Figure 2
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  		FIGURE 2  Cluster analysis of multivariate correlations on general toxicological variables and plasma metabolites. Correlations of all parameters including concentrations of plasma metabolites are shown in a tree diagram. Among the parameters described are general toxicological parameters with significant changes with excessive methionine intake. WI, water intake; FI, food intake; the other abbreviations are given in the legend to Table 1. It is of interest that indicative variables for hemolysis such as T-BIL, spleen weight, splenic nonheme iron, and HDW gathered in the same cluster (Cluster 4).

 

Figure 3
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  		FIGURE 3  Metabolites related to hemolysis. A) Details of the cluster containing indicative variables for hemolysis (Cluster 4 in Fig. 2) are shown. Each superscript describes the method used to detect the plasma metabolite: 1,4GC/MS analysis in the cation-binding fraction or in the ethyl acetate extracts, respectively; 2thiol-specific analysis; and 3amino acid analyzer. Paa429, Paa226, Paa546 in GC/MS analysis were considered to be piperidine carboxylate, sarcosine, and methionine, respectively, based on their mass spectra compared with mass spectrum databases [NIST 98 (National Institute of Standard Techonology) and Wiley Registry (John Wiley & Sons)]. Paa552 and Paa554 were predicted to be the same as Peak 546 (presumably methionine), depending on their retention time and mass spectra. The other GC/MS peaks were undetermined. Paa477 and Paa587 were considered to be identical with Paa476 and Paa586, respectively. B) Concentrations of each plasma metabolite in rats fed additional methionine are plotted. The X-axis of each graph indicates dosages of dietary methionine (0, 0.3, 0.6, 1.2, and 2.4% from the left), and the Y-axis indicates the plasma concentrations (arbitrary unit for metabolites in GC/MS analysis, µmol/dL for the others).

 
    Plasma metabolite ratios. Ratios of metabolic product to precursor were used to analyze which methionine metabolites were accumulated most extensively (Fig. 4). The ratio of homocysteine to methionine did not change in the rats fed additional methionine. The ratios of cystathionine to homocysteine, however, decreased markedly in the rats fed 1.2% or more of additional methionine, indicating that accumulation of homocysteine in rats fed additional methionine was much greater than that of cystathionine. Although more than 1.2% of methionine addition increased the ratios of cysteine to cystathionine by 1.5-fold, there were no changes in the ratios of taurine to cysteine.


Figure 4
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  		FIGURE 4  Precursor-to-product ratios of methionine metabolites in the plasma. Plasma concentration ratios of homocysteine to methionine, cystathionine to homocysteine, cysteine to cystathionine, and taurine to cysteine are shown in rats fed additional methionine (0, 0.3, 0.6, 1.2, and 2.4%). Mean ± SD, *P < 0.05 vs. basal control (Dunnett test).

 
    Amelioration of methionine toxicity by addition of serine and glycine to the diet (Table 2). Nonheme iron accumulation in the spleen caused by 2.4% of additional methionine was partially ameliorated by 2.4% of serine addition to the diet. The same quantity of glycine addition to the methionine excess diet (2.4% wt:wt) abolished the nonheme iron accumulation completely. Addition of either serine or glycine to the high-methionine diet inhibited homocysteine elevation in the plasma induced by methionine excess. The inhibitory effect of glycine on plasma homocysteine elevation tended to be greater than that of serine, which was concordant with the degree of splenic nonheme iron accumulation.


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  		TABLE 2 Amelioration of methionine toxicity by glycine and serine in male Fischer F-344 rats1

 

   DISCUSSION
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 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
LITERATURE CITED
 
Additional methionine intake at a dosage of 2.4% in the diet reduced feed intake, inhibited general growth, and caused various changes in plasma biochemical and hematological variables including variables indicative of hemolytic anemia, as has been reported previously (11). When CAMC was performed on all available variables and plasma metabolites that showed significant changes by methionine load, indicative variables for anemia such as Ht, Hb, MCH, RBC, and MCV were grouped with food intake and body weight gain in 2 clusters that were closely related to each other (Fig. 2). It is of interest that indicative variables for hemolysis, such as splenic nonheme iron, spleen weight per body weight, T-BIL, and HDW that were increased by methionine load were grouped in the same cluster. This cluster also consisted of various plasma metabolites, mainly methionine metabolites such as cysteine, homocysteine, cystathionine, sarcosine, and methionine. These metabolites would be potential biomarker candidates for identification of hematological toxicity of methionine because of the close relation to the toxicity variables in CAMC. Among these metabolites, homocysteine seemed 1 of the best candidates because its plasma concentrations completely discriminated toxic levels of methionine intake from nontoxic levels. This is also supported by the observation that alleviation of methionine toxicity by addition of either serine or glycine to the diet was accompanied by lowered homocysteine levels.

The elevation of plasma homocysteine could also be a marker candidate for a metabolic upper limit of methionine. Although additional methionine intake raised plasma concentrations of all metabolites detected in the present study, the increases were not uniform; increases of methionine and homocysteine were most pronounced among these methionine metabolites. The ratio of cystathionine to homocysteine decreased at 1.2% of additional methionine or more, whereas there was no such change in the other product-to-precursor ratios, suggesting that homocysteine metabolism to cystathionine would be a rate-limiting process in methionine catabolism in rats fed excessive methionine. Cystathionine ß-synthase (CBS), which catalyzes cystathionine synthesis from homocysteine and serine, is considered to participate in the regulation of methionine homeostasis depending on intake levels; cystine supplementation under methionine-deficient conditions reportedly reduces CBS activity and promotes methionine recycling via remethylation of homocysteine to methionine (29). It has also been shown that chronic intake of excessive methionine promotes CBS activity (30). Thus, CBS would be an important enzyme for the maintenance of methionine homeostasis because it regulates metabolism through the transsulfuration pathway, which is consistent with the idea that CBS might be rate-limiting in methionine excess. Serine, another substrate for cystathionine, is known to stimulate homocysteine metabolism to cystathionine in cultured kidney cells (31). The present study has also shown that elevated plasma homocysteine levels in the rats fed excessive methionine were lowered by dietary addition of serine.

Homocysteine toxicities have been shown in both in vitro and in vivo studies. Feeding homocysteine reportedly reduces food intake and body weight gain in rats (14). Recent in vitro study has shown its hemolytic activity in the presence of polymorphonuclear leukocytes (15,16). Although the present study succeeded in identifying homocysteine as a biomarker candidate for methionine toxicity on erythrocytes, homocysteine is reportedly less toxic than methionine in feeding studies (14). Characteristic features of homocysteine toxicity differ from those of methionine: administration of homocysteine causes seizure and sudden death in rats, but methionine does not (14,32). Thus, there must be other "toxic metabolites" that are actually responsible for methionine toxicity on erythrocytes. Steele et al. (18) have reported that the feeding of 3MTP caused toxicity in erythrocytes similar to that produced by methionine excess, and downstream metabolites of 3MTP are highly toxic (19). However, urinary excretion of 3MTP was less than 0.001% of intake levels of methionine, and there was no increase in its excretion even when 2.4% additional methionine was fed to the animals in this study (data not shown). The dosages of 3MTP in the study by Steele et al. (18), in which 2.57% of 3MTP (equimolar to 2.7% of methionine) was added to the diet, would give an exposure to 3MTP that would be impossible from dietary methionine because the transamination pathway is only a minor component of methionine catabolism. Although accumulation of transamination metabolites has been reported in hypermethioninemic patients, their clinical outcome is usually normal (13). Collectively, 3MTP did not appear to be the cause of hemolytic anemia resulting from methionine excess. Cysteine and its downstream metabolites do not seem the cause of the toxicity either. The signs of cysteine toxicity are distinctly different from those of methionine, and supplements of glycine and serine, which ameliorate methionine toxicity, do not ameliorate cysteine toxicity (2). In the present study, some unknown metabolites in plasma were also found to be candidate biomarkers for methionine toxicity. These and the other undetected metabolites, such as SAM, might be involved in methionine toxicity. On the other hand, depletion of some metabolites, for example betaine, as reported by Finkelstein and Martin (30), might also be responsible for methionine toxicity.

Although the mechanism of methionine toxicity is still controversial, the present study has identified several biomarker candidates for methionine toxicity including homocysteine. Plasma homocysteine levels correlated well with the degree of toxicological changes even when methionine toxicity was alleviated by either serine or glycine. Furthermore, the elevation of plasma homocysteine appeared to reflect the upper limit of methionine metabolism when its intake was excessive. We therefore suggest that plasma homocysteine levels may be used as a surrogate biomarker for methionine toxicity and for the metabolic upper limit of dietary methionine intake.


   ACKNOWLEDGMENTS
 
We thank Dr. Kato (University of Tokyo) for valuable discussions.


   FOOTNOTES
 
1 Published in a supplement to The Journal of Nutrition. Presented at the conference "The Fifth Workshop on the Assessment of Adequate Intake of Dietary Amino Acids" held October 24–25, 2005 in Los Angeles. The conference was sponsored by the International Council on Amino Acid Science (ICAAS). The organizing committee for the workshop and guest editors for the supplement were David H. Baker, Dennis M. Bier, Luc Cynober, Yuzo Hayashi, Motoni Kadowaki, and Andrew G. Renwick. Guest editors disclosure: all editors received travel support from ICAAS to attend the workshop. Back

3Abbreviations used: ALAT, alanine aminotransferase activity; ALP, alkaline phosphatase activity; ASAT, aspartate aminotransferase activity; BUN, blood urea nitrogen; CAMC, cluster analysis of multivariate correlations; CBS, cystathionine ß-synthase; CPK, creatine phosphokinase activity; CRE creatine; DRI, dietary reference intake; Hb, hemoglobin; HDW, hemoglobin concentration distribution width; Ht, hematocrit; IP, inorganic phosphate; LDH, lactate dehydrogenase activity; MCH, mean cell hemoglobin; MCHC, mean cell hemoglobin concentration; MCV, mean cell volume; MPV, mean platelet volume; 3MTP, 3-methylthiopropionate; PL, phospholipids; PLt, platelet count; RBC, red blood cell count; RDW, red cell distribution width; T-BIL, total birilubin; TCA, trichloroacetic acid; T-CHO, total cholesterol; TG, triglyceride; TP, total protein; SAM, S-adenosylmethionine; SBD-F, ammonium 7-fluoro-2-oxa-1,3-diazole-4-sulfonate; UL, tolerable upper limit; WBC, white blood cell count.


   LITERATURE CITED
TOP
 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 LITERATURE CITED
 

1. Chung TK, Baker DH. Methionine requirement of pigs between 5 and 20 kilograms body weight. J Anim Sci. 1992;70:1857–63.[Abstract]

2. Harper AE, Benevenga NJ, Wohlhueter RM. Effects of ingestion of disproportionate amounts of amino acids. Physiol Rev. 1970;50:428–558.[Free Full Text]

3. Katz RS, Baker DH. Efficacy of D-, L- and DL-methionine for growth of chicks fed crystalline amino acid diets. Poult Sci. 1975;54:1667–74.[Medline]

4. Kaufman N, Klavins JV, Kinney TD. Methionine deficiency and iron retention in the rat. Br J Nutr. 1966;20:813–7.[Medline]

5. Edmonds MS, Baker DH. Amino acid excesses for young pigs: effects of excess methionine, tryptophan, threonine or leucine. J Anim Sci. 1987;64:1664–71.[Abstract/Free Full Text]

6. Katz RS, Baker DH. Methionine toxicity in the chick: nutritional and metabolic implications. J Nutr. 1975;105:1168–75.[Abstract/Free Full Text]

7. Klavins JV, Kinney TD, Kaufman N. Histopathologic changes in methionine excess. Arch Pathol. 1963;75:661–73.[Medline]

8. Matsuzaki K, Kato H, Sakai R, Toue S, Amao M, Kimura T. Transcriptomics and metabolomics of dietary leucine excess. J Nutr. 2005;135:1571S–5S.[Abstract/Free Full Text]

9. Benevenga NJ, Steele RD. Adverse effects of excessive consumption of amino acids. Annu Rev Nutr. 1984;4:157–81.[Medline]

10. Maede Y, Hoshino T, Inaba M, Namioka S. Methionine toxicosis in cats. Am J Vet Res. 1987;48:289–92.[Medline]

11. Mengel CE, Klavins JV. Development of hemolytic anemia in rats fed methionine. J Nutr. 1967;92:104–10.[Abstract/Free Full Text]

12. Klavins JV, Kinney TD, Kaufman N. Body iron levels and hematologic findings during excess methionine feeding. J Nutr. 1963;79:101–4.[Abstract/Free Full Text]

13. Mudd SH, Tangerman A, Stabler SP, Allen RH, Wagner C, Zeisel SH, Levy HL. Maternal methionine adenosyltransferase I/III deficiency: reproductive outcomes in a woman with four pregnancies. J Inherit Metab Dis. 2003;26:443–58.[Medline]

14. Benevenga NJ, Harper AE. Alleviation of methionine and homocystine toxicity in the rat. J Nutr. 1967;93:44–52.[Abstract/Free Full Text]

15. Olinescu R, Kummerow FA, Handler B, Fleischer L. The hemolytic activity of homocysteine is increased by the activated polymorphonuclear leukocytes. Biochem Biophys Res Commun. 1996;226:912–6.[Medline]

16. Ventura P, Panini R, Tremosini S, Salvioli G. A role for homocysteine increase in haemolysis of megaloblastic anaemias due to vitamin B(12) and folate deficiency: results from an in vitro experience. Biochim Biophys Acta. 2004;1739:33–42.[Medline]

17. Zhang R, Ma J, Xia M, Zhu H, Ling W. Mild hyperhomocysteinemia induced by feeding rats diets rich in methionine or deficient in folate promotes early atherosclerotic inflammatory processes. J Nutr. 2004;134:825–30.[Abstract/Free Full Text]

18. Steele RD, Barber TA, Lalich J, Benevenga NJ. Effects of dietary 3-methylthiopropionate on metabolism, growth and hematopoiesis in the rat. J Nutr. 1979;109:1739–51.[Abstract/Free Full Text]

19. Finkelstein A, Benevenga NJ. The effect of methanethiol and methionine toxicity on the activities of cytochrome c oxidase and enzymes involved in protection from peroxidative damage. J Nutr. 1986;116:204–15.[Abstract/Free Full Text]

20. Regina M, Korhonen VP, Smith TK, Alakuijala L, Eloranta TO. Methionine toxicity in the rat in relation to hepatic accumulation of S-adenosylmethionine: prevention by dietary stimulation of the hepatic transsulfuration pathway. Arch Biochem Biophys. 1993;300:598–607.[Medline]

21. Institute of Medicine of The National Academy of Sciences. Protein and amino acids. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). Washington, D.C.: The National Academy Press; 2005. p. 589–768.

22. Bier DM. Amino acid pharmacokinetics and safety assessment. J Nutr. 2003;133:2034S–9S.[Abstract/Free Full Text]

23. Renwick AG. The safety testing of amino acids. J Nutr. 2003;133:2031S–3S.[Abstract/Free Full Text]

24. Rodricks JV. Approaches to risk assessment for macronutrients and amino acids. J Nutr. 2003;133:2025S–30S.[Abstract/Free Full Text]

25. Noguchi Y, Sakai R, Kimura T. Metabolomics and its potential for assessment of adequacy and safety of amino acid intake. J Nutr. 2003;133:2097S–100S.[Abstract/Free Full Text]

26. Sakai R, Miura M, Amao M, Kodama R, Toue S, Noguchi Y, Kimura T. Potential approaches to the assessment of amino acid adequacy in rats: a progress report. J Nutr. 2004;134:1651S–5S; discussion 64S–66S, 67S–72S.[Abstract/Free Full Text]

27. Katsumata Y, Sato K, Aoki M, Suzuki O, Oya M, Yada S. A simple and accurate method for measurement of the hemoglobin content in blood by colorimetric iron determination. Z Rechtsmed. 1982;88:27–30.[Medline]

28. Krijt J, Vackova M, Kozich V. Measurement of homocysteine and other aminothiols in plasma: advantages of using tris(2-carboxyethyl)phosphine as reductant compared with tri-n-butylphosphine. Clin Chem. 2001;47:1821–8.[Abstract/Free Full Text]

29. Finkelstein JD, Martin JJ, Harris BJ. Methionine metabolism in mammals. The methionine-sparing effect of cystine. J Biol Chem. 1988;263:11750–4.[Abstract/Free Full Text]

30. Finkelstein JD, Martin JJ. Methionine metabolism in mammals. Adaptation to methionine excess. J Biol Chem. 1986;261:1582–7.[Abstract/Free Full Text]

31. House JD, Brosnan ME, Brosnan JT. Characterization of homocysteine metabolism in the rat kidney. Biochem J. 1997;328:287–92.

32. Sprince H, Parker CM, Josephs JA, Jr. Homocysteine-induced convulsions in the rat: protection by homoserine, serine, betaine, glycine and glucose. Agents Actions. 1969;1:9–13.[Medline]




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