Document Detail

Leucine kinetics in reference to the effect of the feeding mode as three discrete meals.
MedLine Citation:
PMID:  10582545     Owner:  NLM     Status:  MEDLINE    
In a recent study, we observed that the 24-hour leucine oxidation measured when three equal meals providing a generous intake of leucine (approximately 90 mg x kg(-1) x d(-1)) are eaten during the day is 16% lower (P < .01) than that for the same diet given as 10 hourly, equal meals. We hypothesized that the pattern of meal intake at a lower level of dietary leucine would affect the 24-hour rate of leucine oxidation and possibly improve the retention of dietary leucine. A total of 11 healthy adults participated in this investigation. The daily leucine intake was 182 micromol x kg(-1) x d(-1) (38 mg x kg(-1) x d(-1)) given with an L-amino acid diet. All subjects received three discrete meals daily for 6 days prior to a 24-hour intravenous (IV) tracer infusion of L-[1-13C]-leucine on day 7 (study 1). Four of these subjects participated in two additional studies of similar design. Study 2 involved giving [1-13C]-leucine as a constant IV infusion together with tracer added to the amino acid mixture at each meal time. In study 3, subjects received the three meals with added [1-13C]-leucine tracer while [2H3]-leucine was given as a constant IV infusion. Total leucine oxidation in studies 1 and 2 was 238+/-66 and 231+/-85 micromol x kg(-1) x d(-1), respectively. Leucine balance was positive, amounting to 18% of the total (diet + tracer) intake. The estimated mean nitrogen balance was +8 mg x kg(-1) x d(-1). Leucine oxidation was higher (P < .01) for breakfast than for the lunch meal. This difference was associated with lower insulin and higher plasma leucine concentrations at breakfast versus lunch periods. The results from study 3 suggest that the higher rate of leucine oxidation observed at breakfast as compared with lunch is not due to a difference in the immediate splanchnic fate of absorbed leucine from each meal. In comparison to our previous small frequent-meal studies, the pattern of meal feeding influences overall leucine utilization at both generous and limiting leucine intakes. Hence, it is possible that the pattern of meal feeding may affect estimations of amino acid requirements using the tracer-balance approach. Longer-term dietary studies will be needed to establish whether and the extent to which this is so.
C A Raguso; A E El-Khoury; V R Young
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Metabolism: clinical and experimental     Volume:  48     ISSN:  0026-0495     ISO Abbreviation:  Metab. Clin. Exp.     Publication Date:  1999 Nov 
Date Detail:
Created Date:  1999-12-10     Completed Date:  1999-12-10     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0375267     Medline TA:  Metabolism     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1378-86     Citation Subset:  IM    
Laboratory of Human Nutrition, School of Science and Clinical Research Center, Massachusetts Institute of Technology, Cambridge 02139, USA.
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MeSH Terms
Amino Acids / pharmacokinetics
Carbon Isotopes
Energy Intake
Leucine / administration & dosage,  metabolism,  pharmacokinetics*
Reference Values
Time Factors
Reg. No./Substance:
0/Amino Acids; 0/Carbon Isotopes; 61-90-5/Leucine

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