title: Global Methylation and Hydroxymethylation in DNA from Blood and Saliva in Healthy Volunteers.
abstract: Aims. We describe a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify and compare simultaneously global methylation and hydroxymethylation in human DNA of different tissues. Materials and Methods. Blood and saliva DNA from fourteen volunteers was processed for epigenetic endpoints using LC-MS/MS and PCR-pyrosequencing technology. Results. Global DNA methylation was significantly lower in saliva (mean 4.61% ±  0.80%), compared to blood samples (5.70% ± 0.22%). In contrast, saliva (0.036% ± 0.011%) revealed significantly higher hydroxymethylation compared to blood samples (mean 0.027% ± 0.004%). Whereas we did not find significant correlations for both epigenetic measures between the tissues, a significant association was observed between global methylation and global hydroxymethylation in saliva DNA. Neither LINE-1 nor Alu elements of blood and saliva correlated, nor were they correlated with the DNA hydroxymethylation of blood or saliva, respectively. Conclusion. Global DNA methylation and hydroxymethylation of cytosine can be quantified simultaneously by LC-MS/MS. Saliva DNA cannot be considered as a surrogate for blood DNA to study epigenetic endpoints.
authors.affiliation: Centre Environment & Health, Department of Public Health and Primary Care, KU Leuven, Kapucijnenvoer 35/5, 3000 Leuven, Belgium ; IDEWE, External Service for Prevention and Protection at Work, 3001 Heverlee, Belgium.
authors.forename: Lode
authors.identifier: 0000-0003-4764-8835
authors.initials: L
authors.lastname: Godderis
authors.affiliation: Centre Environment & Health, Department of Public Health and Primary Care, KU Leuven, Kapucijnenvoer 35/5, 3000 Leuven, Belgium.
authors.forename: Caroline
authors.identifier: 0000-0003-1982-677X
authors.initials: C
authors.lastname: Schouteden
authors.affiliation: Centre Environment & Health, Department of Public Health and Primary Care, KU Leuven, Kapucijnenvoer 35/5, 3000 Leuven, Belgium.
authors.forename: Ali
authors.initials: A
authors.lastname: Tabish
authors.affiliation: Centre Environment & Health, Department of Public Health and Primary Care, KU Leuven, Kapucijnenvoer 35/5, 3000 Leuven, Belgium.
authors.forename: Katrien
authors.identifier: 0000-0003-4397-6831
authors.initials: K
authors.lastname: Poels
authors.affiliation: Centre Environment & Health, Department of Public Health and Primary Care, KU Leuven, Kapucijnenvoer 35/5, 3000 Leuven, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Hoet
authors.affiliation: Department of Environmental Health, Landmark Center, Suite 415 West, P.O. Box 15677, 401 Park Drive, Boston, MA 02215, USA.
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Baccarelli
authors.affiliation: Department of Oral Health Sciences, KU Leuven BIOMAT, 3000 Leuven, Belgium.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Van Landuyt
mesh_terms: D000328:Adult; D020087:Alu Elements / Q000235:genetics; D004247:DNA / Q000097:blood* / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D008297:Male; D012463:Saliva; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D004247:DNA