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NDT Advance Access originally published online on February 28, 2008
Nephrology Dialysis Transplantation 2008 23(8):2660-2665; doi:10.1093/ndt/gfn025
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© The Author [2008]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.For Permissions, please e-mail: journals.permissions@oxfordjournals.org


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

Hoey Lan Tjiong1, Roel Swart1, Trinet Rietveld1, Josias L. Wattimena1, Wim C. Hop2, Marien W. Fieren1 and Jacobus W. van den Berg1

1 Departments of Internal Medicine, Epidemiology and Biostatistics 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



   Abstract
Top
 Abstract
Introduction
 Subjects and methods
 Results
 Discussion
 References
 
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



   Introduction
Top
 Abstract
 Introduction
Subjects and methods
 Results
 Discussion
 References
 
Stable isotope-labelled tracers have been used extensively to study whole-body protein turnover (WBPT) in humans [1]. Both [1-13C]leucine as a primed continuous infusion and [15N]glycine as a single oral dose are validated and commonly used techniques for measuring WBPT in humans [2–6]. In recent years, leucine is the most frequently used amino acid (AA). [1-13C]leucine given as a primed continuous infusion has been considered the reference tracer method for measuring WBPT [7]. However, this method requires a complex study protocol, the taking of several blood and breath samples, and cannot be performed in an outpatient setting [8]. Another method to measure WBPT is the end-product method using a single oral dose of [15N]glycine, which was introduced by Waterlow [9,10]. Due to its less invasive character, studies can be repeated without much discomfort to the patient in an outpatient setting, and it has been shown to be suitable for evaluating WBPT in a variety of conditions [11–18]. The end-product method is an attractive method for evaluating the acute and chronic effect of nutritional interventions on WBPT. To our knowledge, no studies have been reported comparing the end-product method with the precursor method to measure WBPT in patients on peritoneal dialysis (PD). Therefore, we studied WBPT in patients on continuous ambulatory peritoneal dialysis (CAPD) in the fed state using the precursor method with a primed continuous infusion of [1-13C]leucine and the end-product method using a single oral dose of [15N]glycine. The two methods were simultaneously applied and compared during dialysis with AA and glucose (G)-containing solutions (AAG) and with G-only solutions. The present report is focused on comparing the results obtained with the two isotope methods. In our previous publications [19,20], we discussed the clinical implications on the basis of the [1-13C]leucine precursor method, which is considered the ‘gold standard’.



   Subjects and methods
Top
 Abstract
 Introduction
 Subjects and methods
Results
 Discussion
 References
 
Patients
Twelve CAPD patients (Table 1) were recruited from the Peritoneal Dialysis Unit of the Erasmus MC. Inclusion criteria called for stable patients, on PD for >3 months and a weekly Kt/V > 1.7 (urea clearance adjusted for distribution volume, using PD adequest 2.0 software, Baxter). Exclusion criteria were peritonitis, other infectious or inflammatory diseases in the previous 6 weeks, malignancy and a life expectancy of <6 months. The Medical Ethics Committee approved the study and a written informed consent was obtained from all patients.


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  		Table 1 Characteristics of the patientsa

 
Study design
Previously we performed an open-label, randomized, crossover study on two days with a six-day interval compar- ing the effect of AAG dialysate [one bag of 2.5 L Nutrineal® 1.1%, containing 27 g AA, mixed with four bags of 2.5 L Physioneal® 1.36–3.86% (Baxter BV, Utrecht, The Netherlands), depending on ultrafiltration targets] with a control dialysate containing only G (five bags of 2.5 L Physioneal® 1.36–3.86%, individualized per patient depending on ultrafiltration targets). WBPT was measured using the precursor method with a primed continuous infusion of [1-13C]leucine.

In the present publication we compared the end-product method using a single oral dose of [15N]glycine with the precursor method to measure WBPT during a 9-h dialysis with AAG versus G-only dialysis in CAPD patients in the fed state (Figure 1). Frequent exchanges were carried out with an automated cycler, because metabolic steady-state conditions are required for WBPT using [1-13C]leucine, and these are not achieved with a conventional CAPD scheme. The dialysis took place during the day while the patients consumed a liquid complete diet, isonitrogeneous and isocaloric to their habitual diet, based on food records and a dietary interview. The total food intake was divided into 11 identical portions. The first two portions were given at half-hourly intervals and the remaining nine portions at hourly intervals to provide metabolic steady-state conditions. Patients were randomized to start with AAG or G on the first day by drawing 1 of 12 sealed envelopes. On the two study days the patients stayed in the Department of Nephrology of the Erasmus MC during the 9-h study period entering at 8.00 a.m. and leaving at the end of the study and after filling the abdomen with their usual nightly dialysate. Patients were not allowed to eat anything except their liquid diet during the whole study, but non-caloric fluids were permitted.


Figure 1
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  		Fig. 1 Schematic diagram of the study-day protocol. {blacktriangledown} denotes portions of the liquid food, the first two portions given half hourly and thereafter hourly. {blacktriangleup} denotes time points of blood sampling and {triangleup} breath sampling.

 
Whole-body protein turnover studies using [1-13C]leucine as a primed continuous infusion
On the two study days, rates of WBPT during the 9-h daytime dialysis and oral feeding were determined with a primed continuous intravenous infusion of [1-13C]leucine, which was carried out during the last 3 h of the dialysis period. To measure plateau plasma keto-isocaproic acid (KIC) [21] and CO2 13C-enrichment, blood and expired air samples were simultaneously collected at appropriate time points. Indirect calorimetry (Deltatrac® metabolic monitor, Datex, Finland) was performed to measure CO2 production (VCO2).

Whole-body protein turnover studies using a single oral [15N]glycine gift
On the two study days, rates of WBPT were studied with a single oral dose of [15N]glycine. At 08:00 the overnight dialysis fluid was drained and ‘dry’ body weight was measured using a chair wheel weight (Seca Corp. Scale, USA). At 8:30 a catheter was inserted into a superficial vein; blood samples were collected for baseline 15N-urea values. Oral liquid nutrition was then started. After emptying the bladder all voided urine was collected and blood samples were taken. At 9:30 (T0) 200 mg 15N of glycine dissolved in 50 ml water was given orally and dialysis was started, which ended at 18:30. 15N urea was determined in collected drained dialysate, plasma and all voided urine during the 9-h study period.

Analytical determinations and calculations
The WBPT based on [15N]glycine as a single oral dose was calculated according to Waterlow et al. [10]. Due to the very low amount of ammonia in the dialysate, only the end-product 15N urea was used for the analysis. Any traces of free ammonia were previously removed. Urea in plasma, dialysate and urine was converted by urease to ammonia and the formed ammonia was trapped in KHSO4 by the Conway diffusion method. Collected ammonium sulphate was combusted in an elemental analyser (Carlo Erba NC1500, Interscience BV, Breda, The Netherlands), and the effluent was led to an isotope ratio mass spectrometer (ABCA, Sercon LMTD, Crewe, UK) for 15N determination. Changes in the body urea pool were calculated from blood urea nitrogen measurements before (T0) and 9 h after the start of the experiment (T540 min) using total body water as distribution volume. Flux (Q), synthesis (S) and breakdown (B) were calculated on the basis of 15N-urea excretion disregarding the very low amount of 15N ammonia present in the dialysate and the data are expressed as g protein/kg/9 h. The flux (Q) is the rate of nitrogen flux (grams of nitrogen over 9 h) and was calculated using the equation Q = d(Ed + Eu + Ep)/ (ed + eu + ep); Ed, Eu and Ep are the amount N urea in the dialysate, urine and the corrected urea pool respectively; ed, eu and ep are the amount 15N urea in the dialysate, urine and the corrected urea pool respectively and d is the amount of isotope administered (grams of 15N).

Using calculated nitrogen intake (I) and measured total N loss (E), the synthesis by urea (Su), the breakdown to urea (Bu) was calculated using the equation Q = I + Bu = Su + E.

In the precursor method, the leucine carbon flux was calculated from the 13C-enrichment of {propto}-KIC; oxidation of L-[1-13C]leucine was determined by measuring breath CO2 13C-enrichment and flux (Q), synthesis (S) and breakdown (B) were calculated as previously reported [6,17]. To convert the results of the [15N]glycine-WBPT (grams of nitrogen over 9 h) to its protein equivalent, it was assumed that 1 g of N corresponds to 6.25 g of protein. The results of WBPT using [1-13C]leucine (mmol leucine/kg/min) are converted to grams of protein during the 9 h of dialysis, assuming a leucine content of 590 umol/g protein.

Statistical analysis
Data were analysed using the statistical program SPSS, version 11.0, for Windows (SPSS Inc., Chicago, IL, USA). Data are expressed as mean ± SD, or as indicated otherwise. The paired t-test was used to compare differences between the two treatment regimens (AAG versus G dialysis) with regard to leucine and glycine results. Pearson's correlation coefficient was used to assess the relations between the two methods for measuring net protein synthesis during the two treatment regimens. ICC and the Bland and Altman method were used to assess the agreement between the two methods. Differences were considered statistically significant when the two-sided P-value was <0.05.



   Results
Top
 Abstract
 Introduction
 Subjects and methods
 Results
Discussion
 References
 
The baseline characteristics of the 12 patients are summarized in Table 1. Three patients were anuric, whereas the remaining nine patients had a mean residual renal function of 4.45 ± 2.16 ml/min/1.73 m2. The study protocol was well tolerated by all patients. The liquid diet was consumed completely. None of the patients dropped out of the study. The baseline weight and the weight at the end of G-only dialysis were 77.1 ± 13 kg and 77.3 ± 13 kg, respectively, P = 0.015. The baseline weight and the weight at the end of AAG dialysis were 77.5 ± 13 kg and 77.6 ± 13 kg, respectively, n.s. Serum urea concentrations prior to the start and at the end of WBPT during G dialysis were 20.5 ± 7.6 mmol/l and 20.0 ± 6.9 mmol/l, respectively. Serum urea concentrations before the start and at the end of WBPT during AAG dialysis were 22.0 ± 7.6 mmol/l and 21.8 ± 6.5 mmol/l, respectively.

Flux and oxidation (excretion) were significantly higher using AAG compared with G-only dialysate, both with the precursor method (P < 0.05) and the end-product method (P < 0.05). Using AAG protein synthesis rate was significantly higher with the precursor method (P < 0.03), but with the end-product method a significant difference was not attained (P = 0.06) between AAG and G dialysate. There is a larger variation coefficient in the results with the [15N]glycine end-product method compared with the data found with the [1-13C]leucine method measuring protein synthesis and protein breakdown (Table 2). Both methods showed a significant correlation for net protein synthesis (i.e. protein synthesis minus breakdown) both during AAG (r = 0.75, P = 0.005) and during G-only dialysis (r = 0.86, P = 0.000). There was also a significant correlation between both methods for protein synthesis during AAG (r = 0.75, P = 0.005) and G-only dialysis (r = 0.58, P = 0.046). No significant correlation was found between both methods for protein breakdown either during AAG (r = 0.46, P = 0.13) or during G-only dialysis (r = 0.36, P = 0.25). Figure 1 shows moderate agreement between both methods (ICC = 0.70) for net protein synthesis during AAG dialysis. Figure 2 shows good agreement (ICC = 0.88) during G-only dialysis. The Bland and Altman plots show that for individual cases the difference between the two methods can be rather large and the limits of agreement are rather wide.


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  		Table 2 Comparison between [15N]glycine-WBPT and [13C]leucine-WBPT during both dialysis schemesa

 

Figure 2
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  		Fig. 2 Left panel: scatterplot of net protein synthesis (PS) during AAG dialysis of the glycine method (vertical axis) versus the leucine method (horizontal axis). Right panel: Bland and Altman plot for agreement of the two methods. The difference (diff) of the two methods glycine (gly) and leucine (leu) is plotted against the mean of the two methods.

 


   Discussion
Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
References
 
In this study we investigated whether the results of WBPT in patients undergoing CAPD, measured with the end-product method using a single oral dose of [15N]glycine, were comparable with those obtained with the precursor method with a primed continuous infusion of [1-3C]leucine [20]. Both methods were applied simultaneously in the same patients to measure WBPT during dialysis with AAG solutions and during dialysis with G-only solutions. To our knowledge this is the first study comparing the two methods in PD patients.

The two isotope methods used in this study are based on models of complicated metabolic processes. Each of the models makes use of different assumptions and calculations [7]. It has been reported that each of these methods gives an approximation of the true value for the process in question. These methods are however suitable for comparative studies and to detect trends in relative magnitude and direction of changes that might have clinical relevance.

The objective of the present publication is to compare data found for synthesis, breakdown and net protein synthesis obtained with each of the two methods. The data are represented in Table 2. The two methods show a good correlation for measuring the net protein balance (i.e. protein synthesis minus protein breakdown) during AAG dialysis and G-only dialysis as well (Figures 2 and 3). There is an acceptable agreement between both methods. The net protein synthesis can be regarded as the actual amount of protein changing in whole-body protein mass. Therefore this figure is most relevant for clinical practice.


Figure 3
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  		Fig. 3 Left panel: scatterplot of net protein synthesis (PS) during G dialysis of the glycine method (vertical axis) versus the leucine method (horizontal axis). Right panel: Bland and Altman plot for agreement of the two methods. The difference (diff) of the two methods glycine (gly) and leucine (leu) is plotted against the mean of the two methods.

 
Comparisons between the end-product and the precursor method performed in the same patients at the same time are scarce and it is difficult to compare our results with previously performed studies in non-dialysis patients [22,23]. In most of the studies in non-dialysis patients, the calculation of WBPT measured with [15N]glycine was based on the average of 15N-enrichment in urinary ammonia and urea [24]. Our calculations of WBPT were based on the method of Waterlow et al. [7]. However, our patients were treated with PD because of end-stage renal failure. Therefore, we measured 15N-enrichment in urea, not in ammonia, as the end product present in the dialysate, plasma and, if any, in urine. Complete collection of urine is essential for the calculations. The 15N-enrichment of ammonia was ignored because ammonia was found in minute amounts in dialysate. Some patients produced a small amount of urine, and in them, the analysis was also based on 15N urea. In contrast to the [1-13C]leucine precursor method, splanchnic retention is not taken into account in the calculation of the WBPT with the [15N]glycine method. Although the efficiency of intestinal absorption of [15N]glycine might be <100%, we assumed that the absorption was complete, because no gastrointestinal problems were present. The end-product method with a single oral dose of [15N]glycine gives results in calculated data (synthesis, breakdown) with wider variation coefficients than the precursor method (Table 2). One of the reasons is that patients with renal failure have a large urea pool in which 15N urea enrichment is measured. This might increase the error in its measurement. Body water content may also be abnormal in renal patients, and indeed more so in patients on dialysis. As body water has to be estimated in order to calculate the N-retention, the error in WBPT results might increase further. Calculations of the WBPT based on measured 15N-enrichment of urea as the end product entail a substantial potential error in results for synthesis, breakdown and net synthesis. In addition to difficulties related to renal failure, PD interferes with the end-product method in that total N (E) must be corrected for N in non-absorbed AA left behind in effluent dialysate. This interferes in particular with the comparison of AAG and G-only dialysis. Together these factors may explain why the [15N]glycine method failed to detect the subtle increase of whole-body protein synthesis during AAG dialysis as found with the precursor method.

The primed continuous infusion of L-[1-13C]leucine is a widely accepted method for measuring WBPT in all population groups including dialysis patients and is considered to be the reference method [7]. It is, however, an invasive method, which needs frequent blood sampling and admission to a hospital or a metabolic ward. The end-product method using a single oral dose of [15N]glycine is less invasive and more convenient. It can be performed in an outpatient setting, and it is therefore more suitable for population studies.

In conclusion our results demonstrate that in patients treated with CAPD, the end-product method shows a wider variation than the precursor method. Small, but clinically relevant changes may therefore be more difficult to detect with the [15N]glycine method as it has been found in this study. The basic assumptions differ between the two methods; especially PD complicates the end-product method. It is noteworthy that on average the results with both methods were in the same order of magnitude. Furthermore, the level of agreement between the two methods regarding net protein synthesis is acceptable. While the precursor method is preferable to study WBPT in small groups, the more practical end-product method is useful in larger groups of selected patients including those undergoing PD.



   Acknowledgments
 
This investigator-initiated study was supported by grants from Baxter Benelux. The authors thank the patients for their participation. They also thank Devada Kahriman and Laurens J. van Dijk, PD nurses; Adorée M. van der Wiel and José van der Steen, dieticians; and Marja Belder, nurse, for their cooperation in the study.

Conflict of interest statement. None declared.



   References
Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 

  1. Halliday D, Rennie MJ. The use of stable isotopes for diagnosis and clinical research. Clin Sci (1982) 63:485–496.[Web of Science][Medline]
  2. Kopple JD, Bernard D, Messana J, et al. Treatment of malnourished CAPD patients with an amino acid based dialysate. Kidney Int (1995) 47:1148–1157.[Medline]
  3. Swart GR, Van Den Berg JW, Wattimena JL, et al. Elevated protein requirements in cirrhosis of the liver investigated by whole body protein turnover studies. Clin Sci (1988) 75:101–107.[Web of Science][Medline]
  4. Goodship THJ, Lloyd S, Claque MB, et al. Whole body leucine turnover and nutritional status in continuous ambulatory peritoneal dialysis. Clin Sci (1987) 73:463–469.[Web of Science][Medline]
  5. Pacy PJ, Price GM, Halliday D, et al. Nitrogen homeostasis in man: the diurnal responses of protein synthesis and degradation and amino acid oxidation to diets with increasing protein intakes. Clin Sci (1994) 86:103–118.[Web of Science][Medline]
  6. Delarue J, Maingourd C, Objois M, et al. Effects of an amino acid dialysate on leucine metabolism in continuous ambulatory peritoneal dialysis patients. Kidney Int (1999) 56:1934–1943.[CrossRef][Medline]
  7. Duggleby SL, Waterlow JC. The end-product method of measuring whole-body protein turnover: a review of published results and a comparison with those obtained by leucine infusion. Br J Nutr (2005) 94:141–153.[CrossRef][Medline]
  8. Matthews DE, Motil KJ, Rohrbaugh DK, et al. Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-13C]leucine. Am J Physiol (1980) 238:E473–E479.[Web of Science][Medline]
  9. Waterlow JC. 15N end-product methods for the study of whole body protein turnover. Proc Nutr Soc (1981) 40:317–320.[CrossRef][Web of Science][Medline]
  10. Waterlow JC, Golden MHN, Garlick PS. Protein turnover in man measured with 15N: comparison of end products and dose regimes. Am J Physiol (1978) 235:E165–E174.[Web of Science][Medline]
  11. Stroud MA, Jackson AA, Waterlow JC. Protein turnover rates of two human subjects during an unassisted crossing of Antartica. Br J Nutr (1996) 76:165–174.[CrossRef][Medline]
  12. Stein TP, Schluter MD. Plasma protein synthesis after spaceflight. Aviat Space Environ Med (2006) 77:745–748.[Medline]
  13. Holt TL, Ward LC, Francis PJ, et al. Whole body protein turnover in malnourished cystic fibrosis patients and its relationship to pulmonary disease. Am J Clin Nutr (1985) 41:1061–1066.[Abstract/Free Full Text]
  14. Waardenburg DA, Deutz NEP, Hoos MB, et al. Assessment of whole body protein metabolism in critically ill children: can we use the [15N]glycine single oral dose method-grou? Clin Nutr (2004) 23:153–160.[CrossRef][Web of Science][Medline]
  15. Picou D, Taylor-Roberts T. The measurement of total protein synthesis and catabolism and nitrogen turnover in infants in different nutritional states and receiving different amounts of dietary protein. Clin Sci (Lond) (1969) 36:283–296.[Medline]
  16. Jeevanandam M, Horowitz GD, Lowry SF, et al. Cancer cachexia and protein anabolism. Lancet (1984) I:1423–1427.
  17. Arnal MA, Mosoni L, Boirie Y, et al. Protein pulse feeding improves protein retention in elderly women. Am J Clin Nutr (1999) 69:1202–1208.[Abstract/Free Full Text]
  18. Kondrup J, Nielsen K, Juul A. Effect of long-term refeeding on protein anabolism in patients with cirrhosis of the liver. Br J Nutr (1997) 77:197–212.[CrossRef][Medline]
  19. Tjiong HL, Van Den Berg JW, Wattimena JL, et al. Dialysate as food: combined amino acid and glucose dialysate improves protein anabolism in renal failure patients on automated peritoneal dialysis. J Am Soc Nephrol (2005) 16:1486–1493.[Abstract/Free Full Text]
  20. Tjiong HL, Rietveld T, Wattimena JL, et al. Peritoneal dialysis with solutions containing amino acids plus glucose promotes protein synthesis during oral feeding. Clin J Am Soc Nephrol (2007) 2:74–80.[Abstract/Free Full Text]
  21. Schwenk WF, Beaufrere, Haymond MW. Use of reciprocal pool specific activities to model leucine metabolism in humans. Am J Physiol (1985) 249:E646–W650. 1985; 39: 85–99.[Web of Science][Medline]
  22. Van Goudoever JB, Sulkers EJ, Halliday D, et al. Whole-body protein turnover in preterm appropriate for gestational age and small for gestational age infants: comparison of [15N]glycine and [1-13C]leucine administered simultaneously. Pediatr Res (1995) 37:381–388.[Medline]
  23. Pannemans DLE, Wagenmakers AJM, Westerterp KR, et al. The effect of an increase of protein intake on whole-body protein turnover in elderly women is tracer dependent. J Nutr (1997) 127:1788–1794.[Abstract/Free Full Text]
  24. Fern EB, Garlick PJ, Sheppard HG, et al. The precision of measuring the rate of whole-body nitrogen flux and protein synthesis in man with a single dose of [15N]-glycine. Hum Nutr Clin Nutr (1984) 38C:63–73.[Medline]
Received for publication: 9.11.07
Accepted in revised form: 14. 1.08


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H. L. Tjiong, R. Swart, J. W. van den Berg, and M. W. Fieren
AMINO ACID-BASED PERITONEAL DIALYSIS SOLUTIONS FOR MALNUTRITION: NEW PERSPECTIVES
Perit. Dial. Int., July 1, 2009; 29(4): 384 - 393.
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