Methylated nucleosides excretion

Nucleosides are metabolites of ribonucleic acid (RNA). As a result of excessive turnover of RNA, which occurs in such pathological conditions as cancer, inflammation, and AIDS, nucleosides are excreted into urine in increased amounts. Normal nucleosides (adenosine, guanosine, cytidine, uridine) either undergo further degradation into uric acid, p-alanine, or p-aminoisobutyrate or are reutilized. On the other hand, modified nucleosides, especially methylated nucleosides, are excreted unchanged in urine. Therefore, it seems that elevated levels of modified nucleosides could be an indicator of the presence of cancer and used as a diagnostic tool in cancer prognosis [23]. 

URINARY EXCRETION OF METHYLATED NUCLEOSIDES IN DIFFERENT STATES OF FAILURE TO THRIVE... 

The excretion of "one way" methylated nucleosides reflects the activity of RNA turnover. Therefore it can be interpreted as a new indicator of catabolism-anabolism. 

As far as quantitative chemical derivatization GC analysis is concerned, it is necessary to mention especially the work of Gehrke and his collaborators, who specified the fundamental concepts of quantitative GC analysis combined with the chemical derivatization of sample compounds and applied them to the accurate determination of the twenty natural protein amino acids and other non-protein amino acids as their N-TFA-n-butyl esters [5 ], the urinary excretion level of methylated nucleic acid bases as their TMS derivatives [6], TMS nucleosides [7] and other investigations. Further examples include a computer program for processing the quantitative GC data obtained for seventeen triglyceride fatty acids after their transesterification by 2 NKOH in n-butanol [8], a study of the kinetics of the transesterification reactions of dimethyl terephthalate with ethylene glycol [9] and the GC-MS determination of chlorophenols in spent bleach liquors after isolation of the chlorophenols by a multi-step extraction, purification of the final extract by HPLC and derivatization with diazoethane [10]. 

In addition to major nucleosides and bases, modified nucleosides and bases have also been isolated from tRNA hydrolysates and in physiological fluids of man. Unlike the major nucleic acid components, the methylated or otherwise structurally altered purine and pyrimidine compounds are not recycled in the salvage pathways but are excreted. It has been suggested that the measurement of these modified compounds may provide an indicator of the rate of tRNA metabolism. Furthermore, the altered patterns of excretion for these compounds may be used as biomarkers for the detection of disease states and aberrations in metabolic pathways. 

Urinary excretion of modified nncleosides, originating from tiansfer-RNA, may be nsed as a biomarker for tnmonrs and AIDS. Dudley et al. [54-57] reported method development for the analysis of urinary nucleosides by LC-MS. Initially, LC-MS conditions were optimized [54]. In positive-ion ESI-MS, detection limits were achieved ranging from 7 pmol for tubercidin to 110 pmol for uridine. Next, a comparison was made between GC-MS, LC-MS on an ion-trap instrament, and capillary LC-MS on a triple-quadmpole instmment [55]. These methods proved complementary rather than that just one could be selected as optimal. Therefore, in the next study [56], all three techniques were applied to identily the unexpected 5 -deoxycytidine in the urine of a patient suffering with head and neck cancer. In another study [57], they demonstrated the detection of dA, 1-methyl-dA, xanthosine, 7V-l-methyl-dG, 7V-2-methyl-dG, 7V-2,7V-2-dimethyl-dG, A-2,7V-2,A-7-trimethyl-dG, inosine, and 1-methylinosine in urine samples from various cancer patients. 

Therefore we followed the excretion of several methylated ribo-nucleosides in different states of failure to thrive caused by disturbances of nutrition or metabolism anorexia nervosa, acute enteritis and hypothyreoidism. In all three states an effective treatment can change the metabolic situation towards anabolism. 

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