Feeding pregnant rats a protein-restricted diet persistently alters the methylation of specific cytosines in the hepatic PPARα promoter of the offspring

TLDR

Prenatal under‑nutrition can alter phenotypes through epigenetic changes in specific genes. The study examined how maternal protein restriction, with or without folic acid supplementation, affects CpG methylation of the hepatic PPARα promoter in juvenile and adult offspring. Pregnant rats received control or protein‑restricted diets with varying folic acid; offspring were sampled at days 34 and 80, and pyrosequencing measured methylation at 16 CpG sites in the PPARα promoter. Protein restriction lowered overall PPARα promoter methylation by 26 % and reduced methylation at CpGs 2, 3, 4, 16, while folic‑acid‑supplemented restriction increased methylation at CpGs 5 and 8; these patterns persisted to day 80, demonstrating persistent, site‑specific epigenetic alterations induced by prenatal nutrition.

Abstract

Induction of an altered phenotype by prenatal under-nutrition involves changes in the epigenetic regulation of specific genes. We investigated the effect of feeding pregnant rats a protein-restricted (PR) diet with different amounts of folic acid on the methylation of individual CpG dinucleotides in the hepatic PPARα promoter in juvenile offspring, and the effect of the maternal PR diet on CpG methylation in adult offspring. Pregnant rats (five per group) were fed 180 g/kg casein (control) or 90 g/kg casein with 1 mg/kg folic acid (PR), or 90 g/kg casein and 5 mg/kg folic acid (PRF). Offspring were killed on postnatal day 34 (five males and females per group) and day 80 (five males per group). Methylation of sixteen CpG dinucleotides in the PPARα promoter was measured by pyrosequencing. Mean PPARα promoter methylation in the PR offspring (4·5 %) was 26 % lower than controls (6·1 %) due to specific reduction at CpG dinucleotides 2 (40 %), 3 (43 %), 4 (33 %) and 16 (48 %) ( P < 0·05). There was no significant difference in methylation at these CpG between control and PRF offspring. Methylation of CpG 5 and 8 was higher (47 and 63 %, respectively, P < 0·05) in the PRF offspring than control or PR offspring. The methylation pattern in day 80 PR offspring was comparable to day 34 PR offspring. These data show for the first time that prenatal nutrition induces differential changes to the methylation of individual CpG dinucleotides in juvenile rats which persist in adults.