» Articles » PMID: 36379232

Epigenome-wide DNA Methylation in Leukocytes and Toenail Metals: The Normative Aging Study

Abstract

Background: Environmental metal exposures have been associated with multiple deleterious health endpoints. DNA methylation (DNAm) may provide insight into the mechanisms underlying these relationships. Toenail metals are non-invasive biomarkers, reflecting a medium-term time exposure window.

Objectives: This study examined variation in leukocyte DNAm and toenail arsenic (As), cadmium (Cd), lead (Pb), manganese (Mn), and mercury (Hg) among elderly men in the Normative Aging Study, a longitudinal cohort.

Methods: We repeatedly collected samples of blood and toenail clippings. We measured DNAm in leukocytes with the Illumina HumanMethylation450 K BeadChip. We first performed median regression to evaluate the effects of each individual toenail metal on DNAm at three levels: individual cytosine-phosphate-guanine (CpG) sites, regions, and pathways. Then, we applied a Bayesian kernel machine regression (BKMR) to assess the joint and individual effects of metal mixtures on DNAm. Significant CpGs were identified using a multiple testing correction based on the independent degrees of freedom approach for correlated outcomes. The approach considers the effective degrees of freedom in the DNAm data using the principal components that explain >95% variation of the data.

Results: We included 564 subjects (754 visits) between 1999 and 2013. The numbers of significantly differentially methylated CpG sites, regions, and pathways varied by metals. For example, we found six significant pathways for As, three for Cd, and one for Mn. The As-associated pathways were associated with cancer (e.g., skin cancer) and cardiovascular disease, whereas the Cd-associated pathways were related to lung cancer. Metal mixtures were also associated with 47 significant CpG sites, as well as pathways, mainly related to cancer and cardiovascular disease.

Conclusions: This study provides an approach to understanding the potential epigenetic mechanisms underlying observed relations between toenail metals and adverse health endpoints.

References
1.
Zaghlool S, Kuhnel B, Elhadad M, Kader S, Halama A, Thareja G . Epigenetics meets proteomics in an epigenome-wide association study with circulating blood plasma protein traits. Nat Commun. 2020; 11(1):15. PMC: 6941977. DOI: 10.1038/s41467-019-13831-w. View

2.
Li H, Huang K, Jin S, Peng Y, Liu W, Wang M . Environmental cadmium exposure induces alterations in the urinary metabolic profile of pregnant women. Int J Hyg Environ Health. 2019; 222(3):556-562. DOI: 10.1016/j.ijheh.2019.02.007. View

3.
Shi Y, Zhang W, Dai P, Deng J, Tan L . Comprehensive analysis of KCTD family genes associated with hypoxic microenvironment and immune infiltration in lung adenocarcinoma. Sci Rep. 2022; 12(1):9938. PMC: 9200823. DOI: 10.1038/s41598-022-14250-6. View

4.
Teschendorff A, Marabita F, Lechner M, Bartlett T, Tegner J, Gomez-Cabrero D . A beta-mixture quantile normalization method for correcting probe design bias in Illumina Infinium 450 k DNA methylation data. Bioinformatics. 2012; 29(2):189-96. PMC: 3546795. DOI: 10.1093/bioinformatics/bts680. View

5.
Guallar E, Vant Veer P, Bode P, Aro A, Gomez-Aracena J, Kark J . Mercury, fish oils, and the risk of myocardial infarction. N Engl J Med. 2002; 347(22):1747-54. DOI: 10.1056/NEJMoa020157. View