Age-related changes in the levels of active DNA demethylation pathway products in urine and in DNA isolated from leukocytes

Abstract Background DNA methylation changes are recognized as a key hallmark of biological aging. We analyzed the products of active DNA demethylation pathways in DNA isolated from leukocytes and the urine of healthy volunteers aged between 1.5 and 71 years. Results A statistically significant inverse correlation between age and the analyzed modifications in urine was found for 5-hydroxymethyluracil, 5-hydroxymethylcytosine, 5-(hydroxymethyl)-2′-deoxycytidine, 5-methyl-2′-deoxycytidine, 5-carboxycytosine and 5-formylcytosine. The highest correlation coefficient was observed for 5-hydroxymethyluracil ( r = − 0.66). Interestingly, statistically significant inverse correlations were observed for 5-(hydroxymethyl)-2′-deoxycytidine and 5-methyl-2′-deoxycytidine in DNA. Conclusions Changes in epigenetic modifications with age are more pronounced in urine than in cellular DNA. However, DNA modifications are limited to a single tissue (leukocytes), whereas modifications detected in urine reflect processes occurring at the level of the entire organism.