Document Detail

Oxidation of leucine and alpha-ketoisocaproate to beta-hydroxy-beta-methylbutyrate in vivo.
MedLine Citation:
PMID:  1733247     Owner:  NLM     Status:  MEDLINE    
The oxidation of alpha-ketoisocaproate (KIC) to beta-hydroxy-beta-methylbutyrate (HMB) by the enzyme KIC dioxygenase has been previously described in rat and human liver; however, the importance of this pathway in normal leucine metabolism has not yet been assessed. A series of experiments was conducted in young lambs and pigs to determine whether HMB is produced from KIC in vivo and to estimate the importance of this pathway in leucine metabolism. In the first study, lambs were fed a bolus of KIC, and the change in plasma HMB concentration was monitored over a 24-h period. Administration of KIC increased plasma HMB from basal concentrations of 2 to approximately 7 microM 4 h after the supplementation. In the second experiment, lambs were infused with [6,6,6-2H3]KIC into the duodenum, and the appearance of labeled [2H3]HMB was measured. Under basal conditions, a minimum of 18% of the HMB was derived from KIC, but when unlabeled KIC was infused into the duodenum at a rate of 1.6, plasma HMB concentration doubled, and essentially 100% of the HMB present was derived from KIC. In a third experiment, young pigs were infused with [6,6,6-2H3]leucine. At steady state, [2H3]-leucine and HMB enrichments were nearly identical, indicating that plasma HMB is derived solely from leucine. In a fourth experiment, both lambs and pigs were injected intravenously with 600 mg of HMB daily, and urinary HMB excretion was quantitated.(ABSTRACT TRUNCATED AT 250 WORDS)
M Van Koevering; S Nissen
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The American journal of physiology     Volume:  262     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1992 Jan 
Date Detail:
Created Date:  1992-02-21     Completed Date:  1992-02-21     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  E27-31     Citation Subset:  IM    
Department of Animal Science, Iowa State University, Ames 50011.
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MeSH Terms
Keto Acids / metabolism*
Leucine / metabolism*
Osmolar Concentration
Valerates / blood*,  urine
Reg. No./Substance:
0/Keto Acids; 0/Valerates; 61-90-5/Leucine; 625-08-1/beta-hydroxyisovaleric acid; 816-66-0/alpha-ketoisocaproic acid

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