DNA methylation profiles in adults born at extremely low birth weight

Epigenetic signature of very low birth weight in young adult life

BACKGROUND

Globally, one in ten babies is born preterm (<37 weeks), and 1-2% preterm at very low birth weight (VLBW, <1500 g). As adults, they are at increased risk for a plethora of health conditions, e.g., cardiometabolic disease, which may partly be mediated by epigenetic regulation. We compared blood DNA methylation between young adults born at VLBW and controls.

METHODS

157 subjects born at VLBW and 161 controls born at term, from the Helsinki Study of Very Low Birth Weight Adults, were assessed for peripheral venous blood DNA methylation levels at mean age of 22 years. Significant CpG-sites (5'-C-phosphate-G-3') were meta-analyzed against continuous birth weight in four independent cohorts (pooled n = 2235) with cohort mean ages varying from 0 to 31 years.

RESULTS

In the discovery cohort, 66 CpG-sites were differentially methylated between VLBW adults and controls. Top hits were located in HIF3A, EBF4, and an intergenic region nearest to GLI2 (distance 57,533 bp). Five CpG-sites, all in proximity to GLI2, were hypermethylated in VLBW and associated with lower birth weight in the meta-analysis.

CONCLUSION

We identified differentially methylated CpG-sites suggesting an epigenetic signature of preterm birth at VLBW present in adult life.

IMPACT

Being born preterm at very low birth weight has major implications for later health and chronic disease risk factors. The mechanism linking preterm birth to later outcomes remains unknown. Our cohort study of 157 very low birth weight adults and 161 controls found 66 differentially methylated sites at mean age of 22 years. Our findings suggest an epigenetic mark of preterm birth present in adulthood, which opens up opportunities for mechanistic studies.

Cumulative risks predict epigenetic age in adult survivors of extremely low birth weight

Long-term sequelae of extremely low birth weight (ELBW; ≤1000 g) may contribute to accelerated biological aging. This hypothesis was examined by analyzing a range of risk factors with a molecular age marker in adults born at ELBW or normal birth weight (NBW; ≥2500 g). DNAm age-the weighted average of DNA methylation at 353 cytosine-phosphate-guanine (CpG) sites from across the genome-was derived from a sample of 45 ELBW (M_age  = 32.35 years) and 47 NBW control (M_age  = 32.44 years) adults, using the Illumina 850k BeadChip Array. At two assessments undertaken 9 years apart (at 23 and 32 years), cumulative risks were summed from six domains with potential to affect physiological and psychological health: resting respiratory sinus arrhythmia, blood pressure, basal cortisol, grip strength, body mass index, and self-esteem. At age 32 years, cumulative risks were differentially associated with epigenetic age in ELBW survivors (interaction, p < 0.01). For each additional risk factor they possessed, ELBW survivors (B = 1.43) were biologically 2.16 years older than NBW adults (B = -0.73), by the fourth decade of life. Developmental change, epigenetic maintenance, and intervention targets are discussed.