How much dietary methionine is required to maximize synthesis of protein and transmethylated products in neonatal piglets

Methionine is an indispensable sulfur-containing amino acid required for synthesizing protein as well as other critical metabolites. Methionine acts as a precursor for >50 transmethylation reactions to produce metabolites such as creatine, phosphatidylcholine (PC), and methylated DNA. In neonatal...

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Published in:Applied physiology, nutrition, and metabolism nutrition, and metabolism, 2018-01, Vol.43 (4), p.S2
Main Authors: Asiriwardhana, Mahesha, Kankayaliyan, Thillayampalam, Brunton, Janet, Bertolo, Robert
Format: Article
Language:English
Subjects:
Body fat
Exercise physiology
Glucose
Newborn babies
Peptides
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Summary:Methionine is an indispensable sulfur-containing amino acid required for synthesizing protein as well as other critical metabolites. Methionine acts as a precursor for >50 transmethylation reactions to produce metabolites such as creatine, phosphatidylcholine (PC), and methylated DNA. In neonatal piglets, because a lower fraction of dietarymethionine is incorporated into protein(1/3) compared tomethylated products (2/3), both protein and non-protein demands need to be considered when determining the methionine requirement. Our major objective is to quantify how much dietary methionine is required to maximize synthesis of protein as well as key transmethylated products (creatine, PC, methylated DNA). We hypothesized that a higher level of dietary methionine will be needed to maximize creatine and PC synthesis, with lower levels required to maximize protein synthesis. Twenty surgically altered Yucatan miniature piglets (8 d old; 1.6 kg) were fed complete diets for 5 d and then randomized to 20 test diets with methionine intakes ranging from 20%-220% of requirement (0.05-0.55g/kg/d). After 24 h of test diet, [3H-methyl]- methionine was infused for 6 h to measure methyl incorporation into transmethylated products. After the constant infusion, a 3H-phenylalanine flooding dose was given to measure tissue-specific protein synthesis. Break-point analysis using dual linear regression is used to identify the methionine required to maximize product synthesis. Plasma methionine increased above 0.3 g methionine/kg/d, reflecting the whole body requirement. 3H-PC synthesis maximized at 0.2 g/kg/d, while 3H-DNA did not change with increasing methionine intakes. Plasma homocysteine concentration positively correlated with dietary methionine levels (r2=0.787; P
ISSN:1715-5312