Methionine kinetics in adult men: effects of dietary betaine on L-(2H3-methyl-1-13C)methionine
- Laboratory of Human Nutrition, School of Science, Massachusetts Institute of Technology, Cambridge (USA)
The effects of a daily 3-g supplement of betaine on kinetic aspects of L-(2H3-methyl-1-13C)methionine (MET) metabolism in healthy young adult men were explored. Four groups of four subjects each were given a control diet, based on an L-amino acid mixture supplying 29.5 and 21.9 mg.kg-1.d-1 of L-methionine and L-cystine for 4 d before the tracer study, conducted on day 5 during the fed state. Two groups received the control diet and two groups received the betaine supplement. Tracer was given intravenously (iv) or orally. The transmethylation rate of MET (TM), homocysteine remethylation (RM), and oxidation of methionine were estimated from plasma methionine labeling and 13C enrichment of expired air. RM tended to increase (P = 0.14) but the TM and methionine oxidation were significantly (P less than 0.05) higher after betaine supplementation when estimated with the oral tracer. No differences were detected with the intravenous tracer. Methionine concentration in plasma obtained from blood taken from subjects in the fed state was higher (P less than 0.01) with betaine supplementation. These results suggest that excess methyl-group intake may increase the dietary requirement for methionine.
- OSTI ID:
- 5393006
- Journal Information:
- American Journal of Clinical Nutrition; (United States), Vol. 54:2; ISSN 0002-9165
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BETAINE
BIOCHEMICAL REACTION KINETICS
METHIONINE
METABOLISM
ADULTS
CARBON 13
CYSTINE
DEUTERIUM
DIET
INTRAVENOUS INJECTION
MAN
METHYLATION
NUTRITION
ORAL ADMINISTRATION
TRACER TECHNIQUES
AGE GROUPS
AMINES
AMINO ACIDS
AMMONIUM COMPOUNDS
ANIMALS
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DISULFIDES
DRUGS
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
INJECTION
INTAKE
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAMMALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PRIMATES
QUATERNARY COMPOUNDS
REACTION KINETICS
STABLE ISOTOPES
VERTEBRATES
550501* - Metabolism- Tracer Techniques