Childhood location correlates with epigenetic age and methylation stability in British-Bangladeshi migrants

Background: Migration from one environment to another often causes marked changes in developmental conditions. Here we compare epigenetic ageing and stability of the epigenetic maintenance system among British-Bangladeshi women who grew up in Bangladesh (adult migrants), where there are higher pathogen loads and poorer health care, to second-generation Bangladeshis who grew up in the UK. In our previous studies of these migrants, those who spent their childhoods in Bangladesh also had lower levels of reproductive hormones and a shorter reproductive lifespan compared to those who grew up in the UK, suggesting life history trade-offs during development. In the present study, we hypothesised that women who grew up in Bangladesh would have i) an older epigenetic/biological age compared to the women with a childhood in the UK and ii) that differences in the pace of epigenetic ageing might also be reflected by altered stability of DNA methylation marks. Results: Illumina EPIC array methylation data from buccal tissue was used to establish epigenetic age estimates from 15 adult migrants and 11 second-generation migrants, aged 18-35 years. Using residuals from linear regression of DNA methylation-based biological age (DNAm age) on the chronological age, the results showed significant differences (p=0.016) in epigenetic age estimates: women whose childhood was in Bangladesh are on average 6.02 (± 2.34) years older, than those who grew up in London. We further investigated the efficiency of the epigenetic maintenance system which purportedly is reflected by epigenetic clocks. Methylation states of CpGs at the LHCGR/LHR locus, which contributes to Horvath9s multi tissue epigenetic clock were evaluated. Based on the Ratio of Concordance Preference (RCP) approach that uses double-stranded methylation data, we find that maintenance of epigenetic information is more stable in women who grew up in Bangladesh. Conclusions: The work supports earlier findings that adverse childhood environments lead to phenotypic life history trade-offs. The data indicate that childhood environments can induce subtle changes to the epigenetic maintenance system that are detectable long after exposure occurred. The implication of such a finding warrants further investigation as it implies that a less flexible epigenetic memory system established early in life could reduce the capacity to respond to different environmental conditions in adult life.