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Urinary excretion of nucleosides varies with age and protein metabolism
ELSEVIER
Clinica Chimica Acta 234 (1995) 181-183
L e t t e r to the E d i t o r
Urinary excretion of nucleosides varies with age and protein metabolism B e r n h a r d H. P r a n k e l *a'b, P e t e r C. C l e m e n s b'c, J e n s G u n t e r B u r m e s t e r b'd aDepartment of Pediatrics, Christian-Albrechts-UniversitiitKiel, Schwanenweg 20, D-24105 Kiel, Germany bDepartment of Pediatrics, University of Hamburg, Martinistrafle 52, D-20251 Hamburg, Germany CDepartment of Pediatrics, Klinikum Schwerin, Wismarsche StraJ3e 397, D-19049 Schwerin, Germany dDepartment of Pediatrics, Kinderkrankenhaus Altona, Bleickenallee 38, D-22763 Hamburg, Germany Received 14 July 1994; revision received 28 October 1994; accepted 11 November 1994
Keywords: Phenylketonuria; Protein metabolism; Urinary excretion of nucleosides and nucleobases
Dear Editor, We read with interest the article of Itoh et al. [1] on urinary excretion patterns of modified nucleosides, pseudouridine and l-methyladenosine, in healthy individuals. The authors suggest, that 'in healthy individuals . ,. the metabolism of RNA molecules having pseudouridine and 1-methyladenosine as their constituents are strictly controlled without the influence of neither age or sex, or of any external factors' (emphasis added by us). In our own study we analysed 15 methylated and non-methylated nucleosides and bases out of 161 urine spot samples from 53 phenylketonuria (PKU) patients and 101 urines from age-matched controls. As a standard method the concentration of
* Corresponding author. 0009-8981/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0009-8981(94)05 994-4
B.H. Prankel et al./ Clinica Chimica Acta 234 (1995) 181-183
182 ¢-
6.
o~
t--
o 5" a.)
-•- -
I,_
¢._) o
4.
PKU (mean + sd) Control (mean - sd)
E 0
E =-
2"
0
3.5-7.5 ' 7.5-12.5 '12.5-17.5' >17.5 Age (years)
<3.5
Fig. !. l-Methyladenosine.
the RNA catabolites was related to creatinine. By this means, we could replace 24-h sampling by spot samples, as was shown in Ref. [2]. The diet of our patients was composed according to international agreement: (1) a low-protein diet to decrease the serum phenylalanine level below 0.6 mmol/1 (10 mg/dl); (2) a phenylalanine-free amino acid mixture according to the official recommendation [3] to ensure age-related intake of protein; and (3) a caloric intake Table 1 Age distribution in urinary excretion of pseudouridine and l-methyl-adenosine (nmol/t~mol creatinine) in healthy persons and in PKU patients Age (years)
Norm Mean
PKU S.D.
n
Mean
S.D.
n
l-Methyladenosine Sum <3.5 3.5-7.5 7.5-12.5 12.5-17.5 > 17.5
Pseudouridine Sum <3.5 3.5-7.5 7.5-12.5 12.5-17.5 > 17.5
1.62 2.81 2.05 !.64 1.14 0.98
44.6 97.1 50.3 39.9 29.7 27.7
0.69 0.62 0.39 0.25 0.26 0.16
25.3 26.2 16.7 9.6 4.9 8.6
92 12 19 19 23 19
89 11 20 20 22 16
2.07 3.80 2.31 2.07 1.65 1.46
44.0 73.2 51.1 42.0 34.0 35.1
0.93 1.69 0.50 0.48 0.48 0.38
20.3 25.3 23.5 12.1 12.3 5.9
102 10 15 30 38 9
80 I1 10 24 29 6
B.H. Prankel et al. /Clinica Chimica Acta 234 (1995) 181-183
183
according to the W H O / F A O guidelines [4]. The diet o f our control group matched these norms. Our method o f H P L C detection o f urinary methylated nucleosides, serving as a valid non-invasive method for the evaluation o f protein metabolism [5], was as described in Ref. [6]. It had m a x i m u m intra-assay and inter-assay variation coefficients o f 6.0% and sensitivity in the range o f 10 -9 mol [7]. As a result, analysis o f variance showed (Table 1 and Fig. 1) •
•
•
a highly significant negative correlation between the excretion o f R N A catabolites and age, which figured as the greatest source o f variance; in infancy, the course o f concentration by age could be described as a near logarithmic decrease; that P K U patients excreted significantly higher amounts of methylated and unmodified nucleosides and bases than controls (exceptions: pseudouridine and guanosine); no statistical difference in excretion as to sex (as found by Itoh et al. [1]).
With regard to the compromised amino acid pattern in P K U , these data show, in contradiction to Itoh et al., that the age as well as the protein metabolism, which is largely externally controlled and compromised by P K U , do influence nucleoside concentrations. Moreover, several authors show differences in nucleoside excretion due to age or diet in healthy persons as well as in patients with pathological metabolism (see, for example, Ref. [6]). As a consequence, we would like to supplement the publication of Itoh et al. by the recommendation that when using urinary methylated nucleosides as markers for malignancy, especially in children and in compromised protein metabolism (which often is evident in malignancy), one has to take into account the variability due to age and to protein metabolic state.
References [1] [2] [3] [4] [5] [6] [7]
Itoh K, Aida S, Ishiwata S, Sasaki S, Ishida N, Mizugaki M. Urinary excretion patterns of modified nucleosides, pseudouridine and 1-methyladenosine, in healthy individuals. Clin Chim Acta 1993;217:221-223 Sch6chU, HeUer-Sch6ch U. Molekularbiologie und klinische Bedeutung des Stoffwechsels normaler und modifizierter Nucleobasen. Helv Paedr Acta 1977;38(Suppl):1-171 MedicalResearch Council Working Party on Phenylketonuria. Recommendations on the dietary management of phenylketonuria. Arch Dis Child 1993;68:426-427 Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board Commission on Life Sciences, National Research Council. Recommended dietary allowances, 10th Edition. Washington DC: National Academic Press, 1989. Miiller-WickopJ, Lorenz H, Winkler K, Erb N. The age dependency of the creatinine-related concentration of ribonucleosides in human urine. Clin Chem Clin Biochem 1986;24:993-999 SanderG, Hiilsemann J, Topp H. Protein and RNA turnover in preterm infants and adults: a comparison based on urinary excretion of 3-methylhistidine and of modified one-way RNA-catabolites. Ann Nutr Metab 1986;30:137-142 Prankel BH. Untersuchungen zum Protein-Umsatz bei Phenylketonurie-Patienten. Die Messung von Bausteinen der Ribonucleins/iuren durch Hochaufl6sende Fiiissigkeitschromatographie (HPLC). Dissertation, University of Hamburg 1993
Clinica Chimica Acta 234 (1995) 181-183
L e t t e r to the E d i t o r
Urinary excretion of nucleosides varies with age and protein metabolism B e r n h a r d H. P r a n k e l *a'b, P e t e r C. C l e m e n s b'c, J e n s G u n t e r B u r m e s t e r b'd aDepartment of Pediatrics, Christian-Albrechts-UniversitiitKiel, Schwanenweg 20, D-24105 Kiel, Germany bDepartment of Pediatrics, University of Hamburg, Martinistrafle 52, D-20251 Hamburg, Germany CDepartment of Pediatrics, Klinikum Schwerin, Wismarsche StraJ3e 397, D-19049 Schwerin, Germany dDepartment of Pediatrics, Kinderkrankenhaus Altona, Bleickenallee 38, D-22763 Hamburg, Germany Received 14 July 1994; revision received 28 October 1994; accepted 11 November 1994
Keywords: Phenylketonuria; Protein metabolism; Urinary excretion of nucleosides and nucleobases
Dear Editor, We read with interest the article of Itoh et al. [1] on urinary excretion patterns of modified nucleosides, pseudouridine and l-methyladenosine, in healthy individuals. The authors suggest, that 'in healthy individuals . ,. the metabolism of RNA molecules having pseudouridine and 1-methyladenosine as their constituents are strictly controlled without the influence of neither age or sex, or of any external factors' (emphasis added by us). In our own study we analysed 15 methylated and non-methylated nucleosides and bases out of 161 urine spot samples from 53 phenylketonuria (PKU) patients and 101 urines from age-matched controls. As a standard method the concentration of
* Corresponding author. 0009-8981/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0009-8981(94)05 994-4
B.H. Prankel et al./ Clinica Chimica Acta 234 (1995) 181-183
182 ¢-
6.
o~
t--
o 5" a.)
-•- -
I,_
¢._) o
4.
PKU (mean + sd) Control (mean - sd)
E 0
E =-
2"
0
3.5-7.5 ' 7.5-12.5 '12.5-17.5' >17.5 Age (years)
<3.5
Fig. !. l-Methyladenosine.
the RNA catabolites was related to creatinine. By this means, we could replace 24-h sampling by spot samples, as was shown in Ref. [2]. The diet of our patients was composed according to international agreement: (1) a low-protein diet to decrease the serum phenylalanine level below 0.6 mmol/1 (10 mg/dl); (2) a phenylalanine-free amino acid mixture according to the official recommendation [3] to ensure age-related intake of protein; and (3) a caloric intake Table 1 Age distribution in urinary excretion of pseudouridine and l-methyl-adenosine (nmol/t~mol creatinine) in healthy persons and in PKU patients Age (years)
Norm Mean
PKU S.D.
n
Mean
S.D.
n
l-Methyladenosine Sum <3.5 3.5-7.5 7.5-12.5 12.5-17.5 > 17.5
Pseudouridine Sum <3.5 3.5-7.5 7.5-12.5 12.5-17.5 > 17.5
1.62 2.81 2.05 !.64 1.14 0.98
44.6 97.1 50.3 39.9 29.7 27.7
0.69 0.62 0.39 0.25 0.26 0.16
25.3 26.2 16.7 9.6 4.9 8.6
92 12 19 19 23 19
89 11 20 20 22 16
2.07 3.80 2.31 2.07 1.65 1.46
44.0 73.2 51.1 42.0 34.0 35.1
0.93 1.69 0.50 0.48 0.48 0.38
20.3 25.3 23.5 12.1 12.3 5.9
102 10 15 30 38 9
80 I1 10 24 29 6
B.H. Prankel et al. /Clinica Chimica Acta 234 (1995) 181-183
183
according to the W H O / F A O guidelines [4]. The diet o f our control group matched these norms. Our method o f H P L C detection o f urinary methylated nucleosides, serving as a valid non-invasive method for the evaluation o f protein metabolism [5], was as described in Ref. [6]. It had m a x i m u m intra-assay and inter-assay variation coefficients o f 6.0% and sensitivity in the range o f 10 -9 mol [7]. As a result, analysis o f variance showed (Table 1 and Fig. 1) •
•
•
a highly significant negative correlation between the excretion o f R N A catabolites and age, which figured as the greatest source o f variance; in infancy, the course o f concentration by age could be described as a near logarithmic decrease; that P K U patients excreted significantly higher amounts of methylated and unmodified nucleosides and bases than controls (exceptions: pseudouridine and guanosine); no statistical difference in excretion as to sex (as found by Itoh et al. [1]).
With regard to the compromised amino acid pattern in P K U , these data show, in contradiction to Itoh et al., that the age as well as the protein metabolism, which is largely externally controlled and compromised by P K U , do influence nucleoside concentrations. Moreover, several authors show differences in nucleoside excretion due to age or diet in healthy persons as well as in patients with pathological metabolism (see, for example, Ref. [6]). As a consequence, we would like to supplement the publication of Itoh et al. by the recommendation that when using urinary methylated nucleosides as markers for malignancy, especially in children and in compromised protein metabolism (which often is evident in malignancy), one has to take into account the variability due to age and to protein metabolic state.
References [1] [2] [3] [4] [5] [6] [7]
Itoh K, Aida S, Ishiwata S, Sasaki S, Ishida N, Mizugaki M. Urinary excretion patterns of modified nucleosides, pseudouridine and 1-methyladenosine, in healthy individuals. Clin Chim Acta 1993;217:221-223 Sch6chU, HeUer-Sch6ch U. Molekularbiologie und klinische Bedeutung des Stoffwechsels normaler und modifizierter Nucleobasen. Helv Paedr Acta 1977;38(Suppl):1-171 MedicalResearch Council Working Party on Phenylketonuria. Recommendations on the dietary management of phenylketonuria. Arch Dis Child 1993;68:426-427 Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board Commission on Life Sciences, National Research Council. Recommended dietary allowances, 10th Edition. Washington DC: National Academic Press, 1989. Miiller-WickopJ, Lorenz H, Winkler K, Erb N. The age dependency of the creatinine-related concentration of ribonucleosides in human urine. Clin Chem Clin Biochem 1986;24:993-999 SanderG, Hiilsemann J, Topp H. Protein and RNA turnover in preterm infants and adults: a comparison based on urinary excretion of 3-methylhistidine and of modified one-way RNA-catabolites. Ann Nutr Metab 1986;30:137-142 Prankel BH. Untersuchungen zum Protein-Umsatz bei Phenylketonurie-Patienten. Die Messung von Bausteinen der Ribonucleins/iuren durch Hochaufl6sende Fiiissigkeitschromatographie (HPLC). Dissertation, University of Hamburg 1993