NDT Advance Access published online on February 28, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn025
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Whole-body protein turnover in peritoneal dialysis patients: a comparison of the [15N]glycine end product and the [13C]leucine precursor methods
1 Departments of Internal Medicine, Epidemiology and Biostatistics, University Medical Center Rotterdam, The Netherlands 2 Erasmus MC, University Medical Center Rotterdam, The Netherlands
Correspondence and offprint requests to: H. L. Tjiong, Department of Internal Medicine, Erasmus MC's, Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. Tel: +31-10-7034610; Fax: +31-10-4633268; E-mail: h.tjiong{at}erasmusmc.nl
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Abstract |
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Background. Two well-described methods for measuring whole-body protein turnover (WBPT) are the precursor method using a primed continuous infusion of [1-13C]leucine and the end-product method with a single oral dose of [15N]glycine. We previously measured the effects of amino acid (AA)-containing dialysate on protein anabolism in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) using the [1-13C]leucine technique. Here, we examine whether the less invasive [15N]glycine method could also be appropriate for studying nutritional interventions.
Methods. We compared the results of WBPT measurements using a single oral dose of [15N]glycine with those obtained with the primed continuous infusion of [1-13C]leucine during AA and glucose (G) dialysis and G-only dialysis in 12 CAPD patients in the fed state.
Results. The end-product method showed a wide variation for protein synthesis and breakdown measurements. It did not detect a small but significant increase in protein synthesis with AA-containing dialysate as shown by the precursor method. However, a significant relation was found between both methods for net protein synthesis (i.e. protein synthesis minus breakdown) during AA and G (r = 0.75, P = 0.005) or during G-only dialysis (r = 0.86, P < 0.001). The agreement between the two methods for the net protein balance was good [intra-class correlation coefficient (ICC) = 0.88] with G-only dialysate and moderate (ICC = 0.70) with AA and G dialysate.
Conclusion. While the precursor method shows less variation, the more convenient end-product method may be useful in larger groups of selected patients including those on PD.
Keywords: amino acids; [13C]leucine infusion technique; [15N]glycine end-product method; peritoneal dialysis; whole-body protein turnover
Received for publication: 9.11.07
Accepted in revised form: 14. 1.08
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