title: Restriction of dietary methyl donors limits methionine availability and affects the partitioning of dietary methionine for creatine and phosphatidylcholine synthesis in the neonatal piglet.
abstract: Methionine is required for protein synthesis and provides a methyl group for >50 critical transmethylation reactions including creatine and phosphatidylcholine synthesis as well as DNA and protein methylation. However, the availability of methionine depends on dietary sources as well as remethylation of demethylated methionine (i.e., homocysteine) by the dietary methyl donors folate and choline (via betaine). By restricting dietary methyl supply, we aimed to determine the extent that dietary methyl donors contribute to methionine availability for protein synthesis and transmethylation reactions in neonatal piglets. Piglets 4-8 days of age were fed a diet deficient (MD-) (n=8) or sufficient (MS+) (n=7) in folate, choline and betaine. After 5 days, dietary methionine was reduced to 80% of requirement in both groups to elicit a response. On day 8, animals were fed [(3)H-methyl]methionine for 6h to measure methionine partitioning into hepatic protein, phosphatidylcholine, creatine and DNA. MD- feeding reduced plasma choline, betaine and folate (P<.05) and increased homocysteine ~3-fold (P<.05). With MD- feeding, hepatic phosphatidylcholine synthesis was 60% higher (P<.05) at the expense of creatine synthesis, which was 30% lower during MD- feeding (P<.05); protein synthesis as well as DNA and protein methylation were unchanged. In the liver, ~30% of dietary label was traced to phosphatidylcholine and creatine together, with ~50% traced to methylation of proteins and ~20% incorporated in synthesized protein. Dietary methyl donors are integral to neonatal methionine requirements and can affect methionine availability for transmethylation pathways.
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Robinson
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9.
authors.forename: Laura E
authors.initials: LE
authors.lastname: McBreairty
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9.
authors.forename: Edward W
authors.initials: EW
authors.lastname: Randell
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9.
authors.forename: Janet A
authors.initials: JA
authors.lastname: Brunton
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9. Electronic address: rbertolo@mun.ca.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Bertolo
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001622:Betaine / Q000008:administration & dosage; D002796:Choline Deficiency / Q000097:blood / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D003401:Creatine / Q000378:metabolism*; D004032:Diet / Q000009:adverse effects*; D005260:Female; D005494:Folic Acid Deficiency / Q000097:blood / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D006710:Homocysteine / Q000097:blood / Q000378:metabolism; D020138:Hyperhomocysteinemia / Q000097:blood / Q000209:etiology* / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000378:metabolism*; D008745:Methylation; D010713:Phosphatidylcholines / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D013552:Swine; D013556:Swine, Miniature; D014316:Tritium
chemical_list: D010713:Phosphatidylcholines; D006710:Homocysteine; D014316:Tritium; D001622:Betaine; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D008715:Methionine; D003401:Creatine
keywords: 1-Carbon metabolism; Betaine; Choline; Folate; Remethylation; Transmethylation