In vivo evidence of ascorbate involvement in the generation of epigenetic DNA modifications in leukocytes from patients with colorectal carcinoma, benign adenoma and inflammatory bowel disease

Abstract

A positive correlation was observed between plasma concentration of ascorbate and levels of two epigenetic modifications, 5-hydroxymethylcytosine and 5-hydroxymethyluracil in leukocyte DNA. [...]a significant difference was found in the levels of these modifications in patients whose plasma concentrations of ascorbate were below the lower and above the upper quartile for the control group. [...]it is still unclear whether this phenomenon is limited solely to tumor tissue, or may occur also in surrogate materials from cancer patients, for example, leukocytes. [...]it cannot be excluded that active DNA demethylation taking place under altered conditions or in a different environment, for example in presence of chronic inflammation (that may induce oxidative stress) or in malnutrition (that may influence ascorbate level), may modulate TET activity and thus, affect the level of epigenetic modifications. In this study, we used our recently developed rapid, highly-sensitive and highly-specific isotope-dilution automated online two-dimensional ultra-performance liquid chromatography with tandem mass spectrometry (2D-UPLC-MS/MS) [19, 20] to analyze global methylation and to determine the levels of TET-mediated oxidation products of 5-mCyt and thymine: 5-hmCyt, 5-fCyt, 5-caCyt and 5-hmUra. [...]we analyzed the level of the best characterized marker of oxidatively modified DNA, 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), as well as the expression of TETs mRNA, and plasma concentrations of antioxidant vitamins: ascorbate, retinol and α-tocopherol. Furthermore, IBD patients presented with elevated levels of 5-fCyt.