Maintaining muscle protein anabolism after a metabolic stress: role of dextrose vs. amino acid availability.
The effect of chronic hypocaloric parenteral infusions of amino acids (AA) vs. dextrose (D) on protein homeostasis after a generalized metabolic stress was examined. Multicatheterized mongrel dogs were metabolically challenged by a 4-day fast and then administered a 4-day intravenous infusion of saline (S, n = 8), D (n = 8), or isocaloric AA (n = 7). Although nitrogen balance (g.kg.1.day-1) was similarly negative with S (-0.37 +/- 0.05), D (-0.28 +/- 0.03), and AA (-0.37 +/- 0.04) during the fasting period, it was less negative (P < or = 0.05) with AA (-0.06 +/- 0.04) than with D (-0.20 +/- 0.03) or S (-0.23 +/- 0.04) during nutrient infusion. AA resulted in net hindlimb uptake and D in net hindlimb release of essential AA (570 +/- 261 vs. -248 +/- 59 nmol.kg-1.min-1). Whereas S and D infusions led to net hindlimb muscle protein loss (-37 +/- 24 and -89 +/- 33 micrograms.kg-1.min-1, respectively, P < or = 0.05 vs. AA), parenteral AA resulted in net deposition (169 +/- 62 micrograms.kg-1.min-1) as measured using L-[ring-2H5]phenylalanine. Thus hypocaloric parenteral D infusion after a metabolic stress does not favor nitrogen conservation, because net whole body nitrogen loss, skeletal muscle protein catabolism, and hindlimb AA release were not blunted compared with S infusion. Conversely, hypocaloric AA infusion preserves whole body and muscle protein stores.
Borel
M J
MJ
Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Williams
P E
PE
Jabbour
K
K
Hibbard
J C
JC
Flakoll
P J
PJ
D000596:Amino Acids / Q000378:metabolism / Q000493:pharmacokinetics*; D000818:Animals; D001682:Biological Availability; D001835:Body Weight; D004285:Dogs; D005215:Fasting; D005947:Glucose / Q000493:pharmacokinetics*; D006614:Hindlimb / Q000098:blood supply; D006706:Homeostasis; D006728:Hormones / Q000097:blood; D007413:Intestinal Mucosa / Q000378:metabolism; D008102:Liver Circulation; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D012039:Regional Blood Flow; D013312:Stress, Physiological / Q000209:etiology / Q000378:metabolism*
D000596:Amino Acids; D006728:Hormones; D009124:Muscle Proteins; D005947:Glucose; D009584:Nitrogen