Dietary methyl donors affect in vivo methionine partitioning between transmethylation and protein synthesis in the neonatal piglet

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• 作者：Jason L. Robinson ; Renee K. Bartlett ; Scott V. Harding ; Edward W. Randell…
• 关键词：Methionine sparing ; Remethylation ; 1 ; Carbon metabolism ; Infant feeding
• 刊名：Amino Acids
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：48
• 期：12
• 页码：2821-2830
• 全文大小：572 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Biochemistry
  Analytical Chemistry
  Biochemical Engineering
  Life Sciences
  Proteomics
  Neurobiology
  
• 出版者：Springer Wien
• ISSN：1438-2199
• 卷排序：48

文摘

Methionine metabolism is critical during development with significant requirements for protein synthesis and transmethylation reactions. However, separate requirements of methionine for protein synthesis and transmethylation are difficult to define because after transmethylation, demethylated methionine is either irreversibly oxidized to cysteine during transsulfuration, or methionine is regenerated by the dietary methyl donors, choline (via betaine) or folate during remethylation. We hypothesized that remethylation contributes significantly to methionine availability and affects partitioning between protein and transmethylation. 4–8-day-old neonatal piglets were fed a diet devoid (MD−) (n = 8) or replete (MS+) (n = 8) of folate, choline and betaine to limit remethylation. After 5 days, dietary methionine was reduced to 80 % of requirement in both groups of piglets to ensure methionine availability was limited. On day 7, an intragastric infusion of [13C₁]methionine and [2H₃-methyl]methionine was administered to measure methionine cycle flux. In MD− piglets, in vivo remethylation was 60 % lower despite 23-fold greater conversion of choline to betaine (P < 0.05) and transmethylation was 56 % lower (P < 0.05), suggesting dietary methyl donors spared 425 µmol methyl/day for transmethylation. The priority of protein synthesis versus transmethylation was clear during MD− feeding (P < 0.05), as an additional 6 % of methionine flux was for protein synthesis in those piglets (P < 0.05). However, whole body transsulfuration was unaffected in vivo despite reduced in vitro cystathionine-β-synthase capacity in MD− piglets (P < 0.05). Our data show that remethylation contributes significantly to methionine availability and that transmethylation is sacrificed to maintain protein synthesis when methionine is limiting in neonates, which should be considered when determining the methionine requirement.