Effects of prenatal dietary methyl donor deficiency on development and epigenetic mechanisms in offspring : studies in the rat

Abstract

Human epidemiological and animal studies suggest that unbalanced maternal diet during pregnancy leads to low birth weight and predisposes offspring to the development of a number of pathological conditions like metabolic and cardiovascular diseases. This effect is referred to as fetal or developmental programming, however the underlying mechanism is yet unknown. An epigenetic mechanism of gene regulation, DNA methylation, has been suggested as a strong candidate for the underling mechanism of developmental programming due to the fact that establishment of DNA methylation patterns begins during early development and requires a constant supply of methyl donors. The main purpose of the present study was to determine whether a deficiency of methyl donors in the maternal diet during prenatal development would result in phenotypic changes and abnormal epigenetic gene regulation in the offspring. The study was designed to help understand whether DNA methylation provides an epigenetic basis to developmental programming. A new rat model of prenatal dietary methyl donor deficiency was established, whereby female rats were fed a diet deficient in methyl donors choline, folate and methionine two weeks prior to mating and throughout pregnancy. The effect of prenatal exposure to methyl donor deficiency on developmental programming was investigated by measuring systolic blood pressure, glucose metabolism, endocrine pancreas structure and behavioral changes in the adult offspring. To investigate immediate and delayed effects of maternal methyl donor deficiency on molecular processes in the offspring, liver, pancreas, kidney, lung and hippocampus tissues were being used for specific DNA methylation measurements by means of Matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Expression of target genes, suggested to be regulated by DNA methylation, was tested using a real time PCR-based technique. The offspring of methyl deficient mothers (MD) had low weight at birth. Young adult MD males had a transient increase in systolic blood pressure and altered pancreatic structure, but no changes in glucose metabolism. Aged female and male MD offspring demonstrated traits of anxiety-like behavior. MD females had improved learning abilities. At the molecular level, the offspring of MD mothers showed age, DNA region and tissue-specific changes in DNA methylation. The MD offspring also demonstrated differences in gene expression, which were not associated with changes in DNA methylation. In conclusion, the present study demonstrated that maternal methyl donor deficiency had a mild selective effect on development of phenotypic changes associated with developmental programming in the adult offspring. This study indicated that prenatal deficiency in methyl donors programmed changes in DNA methylation in the adult offspring, but its’ effect was rather complex and largely unrelated to the observed changes in gene expression.