Effects of folate depletion in utero and a high fat diet post-weaning on DNA methylation in the adult mouse small intestine

Abstract

Increasing evidence from animal studies shows that nutritional insults during development can lead to adverse health in later life. Altered patterns of DNA methylation is a potential mechanism for this programming effect because when DNA is methylated, gene expression is usually repressed. Folate is a major methyl donor so folate depletion in early life may affect DNA methylation and gene expression, leading to increased risk of disease throughout life (1,2) . We have reported that maternal folate depletion influences methylation in the fetal mouse gut (3) . Here we investigated the effects on adult offspring of maternal folate depletion and/or high dietary fat intake post-weaning on gene-specific methylation in the mouse proximal small intestine (SI). Female C57BL/6J mice were randomly assigned to folate-adequate (FA, 2mg/kg) or folate-depleted (FD, 0.4mg/kg) diets 4 weeks prior to mating and assigned diets were maintained during pregnancy and lactation. At weaning, offspring were randomised to a low fat (LF, 5%) or a high fat (HF, 20%) diet. Allocated diets were continued for 6 months when proximal SI samples were collected and snap frozen. DNA was extracted and gene-specific DNA methylation was quantified at ten loci within 6 genes (Esr1, Igf2-DMR1, Slc39a4CGI1 & -CGI2, p16, Obfc2a-amp1, -amp2 & -amp3, and Ppm1k-amp1 & -amp2) by Pyrosequencing. There were no significant effects of maternal folate supply on methylation at any of the loci investigated (n = 24 for FA, n = 24 for FD diet, ANOVA, p >0.05). However, as summarised in the table, methylation at all 9 CpGs and overall mean methylation across all nine CpGs in Slc39a4-CGI1 was significantly lower in DNA from mice fed the HF diet (n = 24 for LF, n = 24 for HF diet, ANOVA, p <0.05). Conversely, methylation at CpGs 3, 4, 5 and mean methylation across all nine CpGs at Obfc2a-amp1, CpGs 1, 4, 6, and overall mean across all nine CpGs at Obfc2a-amp2 were higher in the HF group. Similarly, higher methylation was found at CpGs 2, 4 and mean methylation across all five CpGs in p16; CpGs 1, 2, 4 and overall mean across all four CpGs in Ppm1k-amp1, and CpGs 2, 5, 7 and mean methylation across all seven CpGs in Ppm1k-amp2 in the HF group (ANOVA, p <0.05).