title: Branched-chain amino acid supplementation during bed rest: effect on recovery.
abstract: Bed rest is associated with a loss of protein from the weight-bearing muscle. The objectives of this study are to determine whether increasing dietary branched-chain amino acids (BCAAs) during bed rest improves the anabolic response after bed rest. The study consisted of a 1-day ambulatory period, 14 days of bed rest, and a 4-day recovery period. During bed rest, dietary intake was supplemented with either 30 mmol/day each of glycine, serine, and alanine (group 1) or with 30 mmol/day each of the three BCAAs (group 2). Whole body protein synthesis was determined with U-(15)N-labeled amino acids, muscle, and selected plasma protein synthesis with l-[(2)H(5)]phenylalanine. Total glucose production and gluconeogenesis from alanine were determined with l-[U-(13)C(3)]alanine and [6,6-(2)H(2)]glucose. During bed rest, nitrogen (N) retention was greater with BCAA feeding (56 +/- 6 vs. 26 +/- 12 mg N. kg(-1). day(-1), P < 0.05). There was no effect of BCAA supplementation on either whole body, muscle, or plasma protein synthesis or the rate of 3-MeH excretion. Muscle tissue free amino acid concentrations were increased during bed rest with BCAA (0.214 +/- 0.066 vs. 0.088 +/- 0.12 nmol/mg protein, P < 0.05). Total glucose production and gluconeogenesis from alanine were unchanged with bed rest but were significantly reduced (P < 0.05) with the BCAA group in the recovery phase. In conclusion, the improved N retention during bed rest is due, at least in part, to accretion of amino acids in the tissue free amino acid pools. The amount accreted is not enough to impact protein kinetics in the recovery phase but does improve N retention by providing additional essential amino acids in the early recovery phase.
authors.affiliation: Department of Surgery, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084, USA. tpstein@umdnj.edu
authors.forename: T P
authors.initials: TP
authors.lastname: Stein
authors.forename: M R
authors.initials: MR
authors.lastname: Donaldson
authors.forename: M J
authors.initials: MJ
authors.lastname: Leskiw
authors.forename: M D
authors.initials: MD
authors.lastname: Schluter
authors.forename: D W
authors.initials: DW
authors.lastname: Baggett
authors.forename: G
authors.initials: G
authors.lastname: Boden
mesh_terms: D000328:Adult; D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000008:administration & dosage; D000597:Amino Acids, Branched-Chain / Q000008:administration & dosage / Q000627:therapeutic use*; D001510:Bed Rest; D001798:Blood Proteins / Q000096:biosynthesis; D004032:Diet; D019587:Dietary Supplements; D005943:Gluconeogenesis; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D011506:Proteins / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D001798:Blood Proteins; D009124:Muscle Proteins; D011506:Proteins; D009584:Nitrogen; D000409:Alanine