Provision of extra glutamine to the post-operative patient as the dipeptide L-Alanyl-L-Glutamine (Ala-Gln) results in improved whole body nitrogen balance. In the present studies the acute effects and the possible mechanisms of action of this dipeptide on muscle protein balance have been studied in 15 healthy post-absorptive subjects and in 16 intensive care unit patients who had undergone major elective abdominal surgery. Whole body and skeletal muscle protein turnover were investigated using primed, constant infusions of the stable isotope tracers L-[1-<SUP>13</SUP>C]leucine and L-[<SUP>15</SUP>N]phenylalanine, with determination of plasma leucine-C flux and <SUP>13</SUP>CO<SUB>2</SUB> production, assay of L-[1-<SUP>13</SUP>C]leucine incorporation into mixed anterior tibial muscle protein sampled by biopsy and arteriovenous forearm exchange of L-[<SUP>15</SUP>N]phenylalanine with net release of 3-methylhistidine from forearm tissues to assess muscle mixed protein turnover and myofibrillar protein breakdown respectively. Parenteral administration of the dipeptide Ala-Gln increased plasma and intramuscular glutamine concentrations in healthy subjects and in post-operative patients. In healthy postabsorptive subjects, mixed muscle protein synthesis was increased with no significant effect on mixed muscle protein breakdown or on whole-body protein turnover, although small reductions were observed in whole-body flux of leucine and phenylalanine. The increased glutamine availability in muscle <I>per se</I> appeared to stimulate muscle protein synthesis, calculated on the basis of the enrichments of plasma α-ketoisocaproate. Since Ala-Gln infusion does not appear to alter whole-body protein turnover it is likely that in the absence of availability of dietary amino acids, skeletal muscle protein synthesis is increased by glutamine at the expense of non-muscle protein, as the muscle free amino acid pool could not sustain such an increase for more than a few minutes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641356 |
| Date | January 1996 |
| Creators | Barua, Jayanta Malla |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/20619 |
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