Metabolic programming of DNA methylation patterns by intrauterine exposure to gestational diabetes mellitus

点击翻译按钮获取中文摘要

The epidemic increase in type 2 diabetes and obesity in industrialized countries cannot be explained by overnutrion and physical inactivity alone. Accumulating evidence suggests that prenatal factors, in particular hyperglycemia through gestational diabetes mellitus (GDM) mal-program the fetal metabolism for later life and thus, increase the risk for developing complex metabolic disorders. The mechanisms underlying fetal programming are still largely unclear. It is plausible that epigenetic changes, i.e. in DNA methylation of metabolic genes play an essential role. In a first hypothesis-free approach we will compare the epigenomes of newborns of mothers with and without GDM. To this end, we will analyze cord blood and fetal placenta of 24 pregnancies with dietetically treated GDM, 24 with insulin-dependent GDM and 48 without GDM, using Illumina Infinium HumanMethylation450 BeadChips. Bioinformatic analyses will identify genes and pathways showing significant between-group differences. The effects of confounding factors, in particular of maternal obesity will be considered. The best candidate genes (according to in silico prioritization) from genome-wide methylation analysis will be validated in cohorts of at least 100 independent GDM pregnancies and 100 controls. Bisulfite pyrosequencing and realtime RT PCR, respectively, will be used to quantify the methylation of conspicuous (by array analysis) gene regions and the expression of the transcripts controlled by these sites. For particularly interesting candidate genes, such as the already identified MEST gene, which is essential for adipocyte metabolism, we will perform high-resolution methylation and expression analyses of different regions/transcripts. This will be done in primary cell types (from cord blood, placenta, adult blood and fat tissue) as well as in cell types differentiated from adipose-derived mesenchymal stem cells. The role of 5-hydroxymethylcytosine in metabolic programming of our candidate genes will be elucidated by oxidative bisulfite sequencing. Collectively, our studies will demonstrate the effects of maternal diabetes and/or obesity on the epigenome of the offspring.