Methionine Supply to Growing Steers Affects Hepatic Activities of Methionine Synthase and Betaine-Homocysteine Methyltransferase, but Not Cystathionine Synthase

Lambert, B.D.; Titgemeyer, Evan C.; Stokka, Gerald L.; DeBey, Brad M.; Löest, C.A.

doi:10.1093/jn/132.7.2004

Cited by 30 publications

(31 citation statements)

References 28 publications

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“…MTR activity was dramatically reduced when the cells were grown in Met+, although these conditions triggered maximal growth speed ( figure 1A and 3). Previous studies have already evidenced an influence of methionine on MTR activity [10,26,27]. Kamely et al observed an inhibitory effect of increasing concentrations of methionine on MTR activity of cells cultivated in presence of Hcy, Cbl and folates [10].…”

Section: Discussionmentioning

confidence: 96%

Homocysteine Increases Methionine Synthase mRNA Level in Caco-2 Cells

Ortiou

Alberto²,

Guéant³

et al. 2004

Cell Physiol Biochem

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Background: Methionine synthase (MTR) synthesizes methionine from homocysteine, using cobalamin as a cofactor and 5-methyltetrahydrofolate as a cosubstrate. Aim: To determine the influence of homocystine (Hcy, dimer of homocysteine) in the presence of either cobalamin or methionine on the transcription and the activity of methionine synthase in Caco-2, a human adenocarcinoma cell line. Methods: Methionine synthase activity and quantification of its mRNA by real-time RT-PCR were determined in cells cultivated under four differents conditions: Hcy with cobalamin (Hcy+ Cbl+), Hcy with methionine (Hcy+Met+), methionine with Cbl (Met+ Cbl+) and methionine only (Met+). Results: Activity (nmol/h/mg protein) was maximal in cells cultivated in Hcy+Cbl+ (2.45 ± 0.35), compared to cells cultivated in Hcy+Met+ (0.18 ± 0.01, p<0.001), in Met+ Cbl+ (1.60 ± 0.06, p<0.05), and in Met+ (0.40 ± 0.05, p<0.001), suggesting an adaptation of the cells to requirement in synthesized methionine. The mRNA level of MTR in Hcy+ Cbl+ and Hcy+Met+ (2.82 ±0.49 and 3.33 ± 0.48 AU, respectively ) was about 2.5 / 3.0-fold higher than that in Met+ Cbl+ and in Met+ (1.00 ±0.13 and 1.20 ±0.20 AU, respectively, p<0.001). Conclusion: Methionine synthase expression of Caco-2 cell is under a transcriptional control influenced by Hcy.

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Section: Discussionmentioning

confidence: 96%

Homocysteine Increases Methionine Synthase mRNA Level in Caco-2 Cells

Ortiou

Alberto²,

Guéant³

et al. 2004

Cell Physiol Biochem

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“…Frozen gut (jejunum and ileum) and liver tissues were homogenized (1:5, wt/vol) in 0.04 M potassium phosphate buffer (pH 7.5) containing 1 mM EDTA and 10 mM ␤-mercaptoethanol, as described by Lambert et al (20). Methionine synthase (MS) and cystathionine ␤-synthase (CBS) activities were determined as described previously (20) in the presence of 1 mM SAM for CBS activity assay (33).…”

Section: Enzyme Assaysmentioning

confidence: 99%

Sulfur amino acid deficiency upregulates intestinal methionine cycle activity and suppresses epithelial growth in neonatal pigs

Bauchart-Thevret

Stoll²,

Chacko³

et al. 2009

American Journal of Physiology-Endocrinology and Metabolism

129

119

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We recently showed that the developing gut is a significant site of methionine transmethylation to homocysteine and transsulfuration to cysteine. We hypothesized that sulfur amino acid (SAA) deficiency would preferentially reduce mucosal growth and antioxidant function in neonatal pigs. Neonatal pigs were enterally fed a control or an SAA-free diet for 7 days, and then whole body methionine and cysteine kinetics were measured using an intravenous infusion of [1-(13)C;methyl-(2)H(3)]methionine and [(15)N]cysteine. Body weight gain and plasma methionine, cysteine, homocysteine, and taurine and total erythrocyte glutathione concentrations were markedly decreased (-46% to -85%) in SAA-free compared with control pigs. Whole body methionine and cysteine fluxes were reduced, yet methionine utilization for protein synthesis and methionine remethylation were relatively preserved at the expense of methionine transsulfuration, in response to SAA deficiency. Intestinal tissue concentrations of methionine and cysteine were markedly reduced and hepatic levels were maintained in SAA-free compared with control pigs. SAA deficiency increased the activity of methionine metabolic enzymes, i.e., methionine adenosyltransferase, methionine synthase, and cystathionine beta-synthase, and S-adenosylmethionine concentration in the jejunum, whereas methionine synthase activity increased and S-adenosylmethionine level decreased in the liver. Small intestine weight and protein and DNA mass were lower, whereas liver weight and DNA mass were unchanged, in SAA-free compared with control pigs. Dietary SAA deficiency induced small intestinal villus atrophy, lower goblet cell numbers, and Ki-67-positive proliferative crypt cells in association with lower tissue glutathione, especially in the jejunum. We conclude that SAA deficiency upregulates intestinal methionine cycle activity and suppresses epithelial growth in neonatal pigs.

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“…Data were normalized to 18S ribosomal RNA (⌬⌬Ct analysis). CBS activity was determined as described (18,46). Separate reactions were carried out in the presence and absence of 1.0 mM SAM to test for allosteric induction of CBS.…”

Section: Cbs Measurementmentioning

confidence: 99%

Methionine transmethylation and transsulfuration in the piglet gastrointestinal tract

Riedijk

Stoll

Chacko

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

125

102

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Methionine is an indispensable sulfur amino acid that functions as a key precursor for the synthesis of homocysteine and cysteine. Studies in adult humans suggest that splanchnic tissues convert dietary methionine to homocysteine and cysteine by means of transmethylation and transsulfuration, respectively. Studies in piglets show that significant metabolism of dietary indispensable amino acids occurs in the gastrointestinal tissues (GIT), yet the metabolic fate of methionine in GIT is unknown. We show here that 20% of the dietary methionine intake is metabolized by the GIT in piglets implanted with portal and arterial catheters and fed milk formula. Based on analyses from intraduodenal and intravenous infusions of [1-13 C]methionine and [ 2 H3]methionine, we found that the whole-body methionine transmethylation and remethylation rates were significantly higher during duodenal than intravenous tracer infusion. First-pass splanchnic metabolism accounted for 18% and 43% of the whole-body transmethylation and remethylation, respectively. Significant transmethylation and transsulfuration was demonstrated in the GIT, representing Ϸ27% and Ϸ23% of whole-body fluxes, respectively. The methionine used by the GIT was metabolized into homocysteine (31%), CO 2 (40%), or tissue protein (29%). Cystathionine ␤-synthase mRNA and activity was present in multiple GITs, including intestinal epithelial cells, but was significantly lower than liver. We conclude that the GIT consumes 20% of the dietary methionine and is a significant site of net homocysteine production. Moreover, the GITs represent a significant site of whole-body transmethylation and transsulfuration, and these two pathways account for a majority of methionine used by the GITs.cystathionine ␤-synthase ͉ homocysteine ͉ intestine

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Methionine Supply to Growing Steers Affects Hepatic Activities of Methionine Synthase and Betaine-Homocysteine Methyltransferase, but Not Cystathionine Synthase

Cited by 30 publications

References 28 publications

Homocysteine Increases Methionine Synthase mRNA Level in Caco-2 Cells

Homocysteine Increases Methionine Synthase mRNA Level in Caco-2 Cells

Sulfur amino acid deficiency upregulates intestinal methionine cycle activity and suppresses epithelial growth in neonatal pigs

Methionine transmethylation and transsulfuration in the piglet gastrointestinal tract

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