Indices of methylation in sperm DNA from fertile men differ between distinct geographical regions

TY - JOUR

T1 - Indices of methylation in sperm DNA from fertile men differ between distinct geographical regions

AU - Consales, C

AU - Leter, G

AU - Bonde, Jens Peter

AU - Toft, G

AU - Eleuteri, P

AU - Moccia, T

AU - Budillon, A

AU - Jönsson, B A G

AU - Giwercman, A

AU - Pedersen, H S

AU - Ludwicki, J K

AU - Zviezdai, V

AU - Heederik, D

AU - Spanò, M

N1 - © The Author 2014. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: [email protected].

PY - 2014/9

Y1 - 2014/9

N2 - STUDY QUESTION: Which are the main determinants, if any, of sperm DNA methylation levels?SUMMARY ANSWER: Geographical region resulted associated with the sperm methylation status assessed on genome-wide repetitive sequences.WHAT IS KNOWN ALREADY: DNA methylation level, assessed on repetitive sequences from peripheral blood lymphocyte, can vary with age, gender, alcohol consumption and white blood cell counts.STUDY DESIGN, SIZE, DURATION: A cross-sectional study. Individual data were collected from 269 young healthy men of proven fertility living in three geographical regions: Inuits from Greenland, Caucasians from Warsaw (Poland) and Kharkiv (Ukraine). Semen samples were collected between May 2002 and February 2004 and aliquots were immediately frozen.PARTICIPANTS/MATERIALS, SETTING, METHODS: We estimated sperm DNA global methylation level (DGML) in two ways. First DNA methylation in repetitive DNA sequences (LINE-1, Satα and Alu) was quantified by PCR pyrosequencing after bisulfite conversion and second by flow cytometry (FCM) using fluorescently labeled monoclonal antibodies anti-5-methylcytosine. We analyzed whether personal characteristics and habits, body mass index, semen quality parameters, sperm chromatin integrity, biomarkers of accessory gland function and the plasma concentration of reproductive hormones were associated with sperm DNA methylation levels in men. Associations were evaluated by analysis of variance and linear regression analyses.MAIN RESULTS AND THE ROLE OF CHANCE: The geographical location emerged as the main determinant when using the methylation level in repetitive sequences. FCM DGML results were not associated with those from repetitive sequence analysis. No other consistent associations between methylation markers and the assessed variables were identified across countries.LIMITATIONS, REASONS FOR CAUTION: The methods used are only surrogates of the actual sperm methylome and the methylation levels at individual specific loci were not explored.WIDER IMPLICATIONS OF THE FINDINGS: Sperm DGML is relatively independent from semen quality parameters and is a new candidate biomarker for epidemiological studies of the impact of environmental contaminants on male fertility.STUDY FUNDING/COMPETING INTERESTS: The study is part of the project CLEAR (Climate change, Environmental contaminants and Reproductive health) supported by the European Commission 7th framework program, contract no: FP7-ENV-2008-1-226217. No competing interest is declared.

AB - STUDY QUESTION: Which are the main determinants, if any, of sperm DNA methylation levels?SUMMARY ANSWER: Geographical region resulted associated with the sperm methylation status assessed on genome-wide repetitive sequences.WHAT IS KNOWN ALREADY: DNA methylation level, assessed on repetitive sequences from peripheral blood lymphocyte, can vary with age, gender, alcohol consumption and white blood cell counts.STUDY DESIGN, SIZE, DURATION: A cross-sectional study. Individual data were collected from 269 young healthy men of proven fertility living in three geographical regions: Inuits from Greenland, Caucasians from Warsaw (Poland) and Kharkiv (Ukraine). Semen samples were collected between May 2002 and February 2004 and aliquots were immediately frozen.PARTICIPANTS/MATERIALS, SETTING, METHODS: We estimated sperm DNA global methylation level (DGML) in two ways. First DNA methylation in repetitive DNA sequences (LINE-1, Satα and Alu) was quantified by PCR pyrosequencing after bisulfite conversion and second by flow cytometry (FCM) using fluorescently labeled monoclonal antibodies anti-5-methylcytosine. We analyzed whether personal characteristics and habits, body mass index, semen quality parameters, sperm chromatin integrity, biomarkers of accessory gland function and the plasma concentration of reproductive hormones were associated with sperm DNA methylation levels in men. Associations were evaluated by analysis of variance and linear regression analyses.MAIN RESULTS AND THE ROLE OF CHANCE: The geographical location emerged as the main determinant when using the methylation level in repetitive sequences. FCM DGML results were not associated with those from repetitive sequence analysis. No other consistent associations between methylation markers and the assessed variables were identified across countries.LIMITATIONS, REASONS FOR CAUTION: The methods used are only surrogates of the actual sperm methylome and the methylation levels at individual specific loci were not explored.WIDER IMPLICATIONS OF THE FINDINGS: Sperm DGML is relatively independent from semen quality parameters and is a new candidate biomarker for epidemiological studies of the impact of environmental contaminants on male fertility.STUDY FUNDING/COMPETING INTERESTS: The study is part of the project CLEAR (Climate change, Environmental contaminants and Reproductive health) supported by the European Commission 7th framework program, contract no: FP7-ENV-2008-1-226217. No competing interest is declared.

KW - Cross-Sectional Studies

KW - DNA

KW - DNA Methylation

KW - Fertility

KW - Genome, Human

KW - Geography

KW - Greenland

KW - Humans

KW - Male

KW - Poland

KW - Repetitive Sequences, Nucleic Acid

KW - Semen Analysis

KW - Spermatozoa

KW - Ukraine

U2 - 10.1093/humrep/deu176

DO - 10.1093/humrep/deu176

M3 - Journal article

C2 - 25035434

SN - 0268-1161

VL - 29

SP - 2065

EP - 2072

JO - Human Reproduction

JF - Human Reproduction

IS - 9

ER -