title: Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects.
abstract: The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of L-[ring-13C6]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 +/- 19% and +77 +/- 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial (P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials (P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 +/- 0.006 vs. 0.061 +/- 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 +/- 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.
authors.affiliation: Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. R.Koopman@HB.unimaas.nl
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.forename: Anton J M
authors.initials: AJ
authors.lastname: Wagenmakers
authors.forename: Ralph J F
authors.initials: RJ
authors.lastname: Manders
authors.forename: Antoine H G
authors.initials: AH
authors.lastname: Zorenc
authors.forename: Joan M G
authors.initials: JM
authors.lastname: Senden
authors.forename: Marchel
authors.initials: M
authors.lastname: Gorselink
authors.forename: Hans A
authors.initials: HA
authors.lastname: Keizer
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000328:Adult; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010649:Phenylalanine / Q000097:blood; D014443:Tyrosine / Q000097:blood
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D007328:Insulin; D009124:Muscle Proteins; D014443:Tyrosine; D010649:Phenylalanine; D007930:Leucine