Metal co-exposures and telomere length in Bangladeshi children

Abstract

BACKGROUND AND AIM: Telomeres are non-coding DNA sequences that protect the ends of chromosomes and preserve genetic material during cell division. Telomere length is associated with the occurrence and progression of common chronic diseases. In younger populations, telomere length may represent a biomarker of disease susceptibility. Growing evidence suggests that environmental factors, such as metals, can substantially impact the mechanisms that control telomere length. METHODS: We investigated the association between a panel of metals measured in toenail samples by inductively-coupled plasma mass spectrometry and leukocyte relative telomere length (RTL) measured by Luminex assay, among 472 five- to seven-year-old children enrolled in the Bangladesh Environmental Research in Children's Health (BiRCH) cohort. RESULTS:Of the 18 metals tested, statistically significant correlations with RTL were observed with toenail arsenic (tAs) and mercury (tHg). In linear regression models adjusted for child age, sex, and father’s age at child’s birth, a doubling of log2-transformed tAs was associated with a -0.022 (95% CI: -0.033, -0.011; p=0.0001) decrease in RTL. Similarly, a doubling of log2-transformed tHg was associated with a -0.020 (95% CI: -0.032, -0.007; p=0.002) decrease in RTL. Similar associations were observed using co-exposure regression models including both tAs and tHg, adjusted for covariates. In this model, we observed independent, negative associations of both log2-transformed tAs and tHg with RTL, such that a doubling of tAs was associated with a -0.019 (95% CI: -0.031, -0.007; p=0.003) decrease in RTL and a doubling of tHg was associated with a -0.015 (95% CI: -0.028, -0.002; p=0.02) decrease in RTL. CONCLUSIONS:Our study suggests that both As and Hg may independently influence RTL, with detectable associations in early- to mid-childhood. Further studies are needed to confirm our findings and investigate the potential long-term impacts of As- and Hg- exposure associated telomere shortening in childhood on health outcomes in adult life. KEYWORDS: metals, telomeres, toenails, Bangladesh, children