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 ⁽ Reference Waterland and Jirtle ^{1 ,} Reference Mathers and McKay2 ⁾. We have reported that maternal folate depletion influences methylation in the fetal mouse gut ⁽ Reference McKay, Wong and Relton ^{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, 2 mg/kg) or folate-depleted (FD, 0.4 mg/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, Slc39a4-CGI1 & -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).

* Yes=significant (p<0.05) effects observed, No=no significant effects observed on methylation in response to FD or HF diet within each locus, ↑=higher % methylation & ↓=lower % methylation observed in the HF diet group.

In conclusion, feeding a high fat diet from weaning influenced methylation at Slc39a4-CGI1, Obfc2a-amp1, -amp2, p16, Ppm1k-amp1 and -amp2 in adult mouse proximal SI. This effect was locus and CpG specific.