title: Impact of protein coingestion on muscle protein synthesis during continuous endurance type exercise.
abstract: This study investigates the impact of protein coingestion with carbohydrate on muscle protein synthesis during endurance type exercise. Twelve healthy male cyclists were studied during 2 h of fasted rest followed by 2 h of continuous cycling at 55% W(max). During exercise, subjects received either 1.0 g·kg(-1)·h(-1) carbohydrate (CHO) or 0.8 g·kg(-1)·h(-1) carbohydrate with 0.2 g·kg(-1)·h(-1) protein hydrolysate (CHO+PRO). Continuous intravenous infusions with l-[ring-(13)C(6)]phenylalanine and l-[ring-(2)H(2)]tyrosine were applied, and blood and muscle biopsies were collected to assess whole body protein turnover and muscle protein synthesis rates at rest and during exercise conditions. Protein coingestion stimulated whole body protein synthesis and oxidation rates during exercise by 22 ± 3 and 70 ± 17%, respectively (P < 0.01). Whole body protein breakdown rates did not differ between experiments. As a consequence, whole body net protein balance was slightly negative in CHO and positive in the CHO+PRO treatment (-4.9 ± 0.3 vs. 8.0 ± 0.3 μmol Phe·kg(-1)·h(-1), respectively, P < 0.01). Mixed muscle protein fractional synthetic rates (FSR) were higher during exercise compared with resting conditions (0.058 ± 0.006 vs. 0.035 ± 0.006%/h in CHO and 0.070 ± 0.011 vs. 0.038 ± 0.005%/h in the CHO+PRO treatment, respectively, P < 0.05). FSR during exercise did not differ between experiments (P = 0.46). We conclude that muscle protein synthesis is stimulated during continuous endurance type exercise activities when carbohydrate with or without protein is ingested. Protein coingestion does not further increase muscle protein synthesis rates during continuous endurance type exercise.
authors.affiliation: Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands.
authors.forename: Milou
authors.initials: M
authors.lastname: Beelen
authors.forename: Antoine
authors.initials: A
authors.lastname: Zorenc
authors.forename: Bart
authors.initials: B
authors.lastname: Pennings
authors.forename: Joan M
authors.initials: JM
authors.lastname: Senden
authors.forename: Harm
authors.initials: H
authors.lastname: Kuipers
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000596:Amino Acids / Q000097:blood; D001628:Beverages; D001642:Bicycling / Q000502:physiology*; D001706:Biopsy; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004044:Dietary Proteins / Q000494:pharmacology*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D055815:Young Adult
chemical_list: D000596:Amino Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009124:Muscle Proteins; D019344:Lactic Acid; D014443:Tyrosine; D010649:Phenylalanine; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases