Whole-body protein turnover in peritoneal dialysis patients: a comparison of the [15N]glycine end product and the [13C]leucine precursor methods

• Published in: Nephrology, dialysis, transplantation dialysis, transplantation, 2008-08, Vol.23 (8), p.2660-2665
• Main Authors: Tjiong, Hoey Lan, Swart, Roel, Rietveld, Trinet, Wattimena, Josias L., Hop, Wim C., Fieren, Marien W., Berg, Jacobus W. van den
• Format: Article
• Language: English
• Subjects: [13C]leucine infusion technique; [15N]glycine end-product method; Adult; Aged; amino acids; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Carbon Isotopes; Dialysis Solutions; Emergency and intensive care: renal failure. Dialysis management; Female; Glomerulonephritis; Glycine - administration & dosage; Glycine - pharmacokinetics; Humans; Intensive care medicine; Leucine - administration & dosage; Leucine - pharmacokinetics; Male; Medical sciences; Middle Aged; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Nitrogen Isotopes; peritoneal dialysis; Peritoneal Dialysis, Continuous Ambulatory; Proteins - metabolism; whole-body protein turnover
• ISSN: 0931-0509; 1460-2385
• DOI: 10.1093/ndt/gfn025

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.