Dietary protein restriction of pregnant rats in the F0 generation induces altered methylation of hepatic gene promoters in the adult male offspring in the F1 and F2 generations

Abstract

Epidemiological studies and experimental models show that maternal nutritional constraint during pregnancy alters the metabolic phenotype of the offspring and that this can be passed to subsequent generations. In the rat, induction of an altered metabolic phenotype in the liver of the F1 generation by feeding a protein-restricted diet (PRD) during pregnancy involves the altered methylation of specific gene promoters. We therefore investigated whether the altered methylation of PPARalpha and glucocorticoid receptor (GR) promoters was passed to the F2 generation. Females rats (F0) were fed a reference diet (180 g/kg protein) or PRD (90 g/kg protein) throughout gestation, and AIN-76A during lactation. The F1 offspring were weaned onto AIN-76A. F1 females were mated and fed AIN-76A throughout pregnancy and lactation. F1 and F2 males were killed on postnatal day 80. Hepatic PPARalpha and GR promoter methylation was significantly (P<0 x 05) lower in the PRD group in the F1 (PPARalpha 8 %, GR 10 %) and F2 (PPARalpha 11 %, GR 8 %) generations. There were trends (P<0 x 1) towards a higher expression of PPARalpha, GR, acyl-CoA oxidase and phosphoenolpyruvate carboxykinase (PEPCK) in the F1 and F2 males, although this was significant only for PEPCK. These data show for the first time that the altered methylation of gene promoters induced in the F1 generation by maternal protein restriction during pregnancy is transmitted to the F2 generation. This may represent a mechanism for the transmission of induced phenotypes between generations

Fig. 1

Effect of maternal protein intake during pregnancy in the F₀ generation on hepatic (A) PPARα and (B) glucocorticoid receptor promoter methylation in the F₁ and F₂ male offspring. Values are mean (SEM) normalized to the offspring of the F₁ RD group (n 6 per group). * Indicates values significantly different (P<0.05) between maternal diets within a generation by 1-way ANOVA with Dunnett’s post hoc test (2-sided) using the RD F₁ group as reference. PRD, protein-restricted diet; RD, reference diet.