Epigenetic Programming by Maternal Behavior in the Human Infant

Abstract

: media-1vid110.1542/5804912859001PEDS-VA_2017-1890Video Abstract OBJECTIVES: We sought to determine if variations in maternal care alter DNA methylation in term, healthy, 5-month-old infants. This work was based on landmark studies in animal models demonstrating that nurturing care by dams would alter their newborns' stress responses through epigenetic mechanisms. We used breastfeeding as a proxy for animal maternal behavior. We hypothesized alterations in DNA methylation of the glucocorticoid receptor gene and less hypothalamic stress response in infants of mothers who breastfed their infants versus infants of mothers who did not breastfeed.

Methods: A cohort study of term, healthy infants and their mothers who did (n = 21) or did not (n = 21) breastfeed for the first 5 months was used in this analysis. Cortisol stress reactivity was measured in infant saliva by using a mother-infant interaction procedure and DNA methylation of an important regulatory region of the glucocorticoid receptor gene. Changes in DNA methylation of this gene in humans were compared to homologous regions of the rat gene. DNA samples were prepared from cheek swabs and subjected to quantitative analysis of the extent of methylation by using sensitive sequencing techniques.

Results: Breastfeeding was associated with decreased DNA methylation of the glucocorticoid receptor promoter and decreased cortisol reactivity in 5-month-old infants. Decreased DNA methylation occurred in the promoter region involved in regulation of the hypothalamic-pituitary-adrenal and immune system responses.

Conclusions: Maternal care in humans may impact the hypothalamic-pituitary-adrenal stress response through behavioral programming and manifest as offspring epigenetic change. These results explain, in part, some of the positive effects observed in children who are breastfed.

FIGURE 1

Mother-infant interaction procedure. A, Infant when playing as normal. B, Mother when playing as normal. C, Infant during the still-face period. D, Mother during the still-face period.

FIGURE 2

Differences in the extent of DNA methylation at CpG sites across the glucocorticoid receptor gene (NR3C1) in buccal cell–derived DNA from infants experiencing low (blue bar) or high (red bar) breastfeeding behaviors. Bar heights represent the mean methylation in all subjects within the group, and error bars represent the SEM. ^a False-discovery rate is q < 0.05.

FIGURE 3

Scatterplot of the correlation between amount of DNA methylation of the glucocorticoid receptor gene (NR3C1) at CpG site 10 and cortisol reactivity. Cortisol was measured from saliva collected before and after a mother-infant interaction still-face stress procedure. Cortisol reactivity was computed as a difference score (poststress micrograms per deciliter minus prestress micrograms per deciliter) from the log transformation shown on the y-axis. The mean percentage of DNA methylation of the glucocorticoid receptor gene (NR3C1) at CpG site 10 is shown on the x-axis. The line in the figure is the linear regression that was statistically significant (r = 0.41; P < .05), and the circles are the individual subjects. R² linear = 0.167.

FIGURE 4

Scatterplot of the correlation between amount of DNA methylation of the glucocorticoid receptor gene (NR3C1) at CpG site 12 and cortisol reactivity. Cortisol was measured from saliva collected before and after a mother-infant interaction still-face stress procedure. Cortisol reactivity was computed as a difference score (poststress micrograms per deciliter minus prestress micrograms per deciliter) from the log transformation shown on the y-axis. The mean percentage of DNA methylation of the glucocorticoid receptor gene (NR3C1) at CpG site 12 is shown on the x-axis. The line in the figure is the linear regression that was statistically significant (r = 0.35; P < .05), and the circles are the individual subjects. R² linear = 0.124.