Investigation of changes in DNA methylation associated with alterations in gene expression resulting in differences between lean and obese adipogenesis.

DNA methylation (DNAm) is an important epigenetic regulator controlling various cellular activities, including cell proliferation and differentiation. In the present work, we examined alterations in DNAm associated with obesity using methylome and transcriptome data from 27 purified adipocytes (ACs) and 7 preadipocytes (preACs) in human visceral adipose tissue (VAT) samples. We identified differentially methylated probes (DMPs) using two methods: (i) DMPs that were obtained from a comparison of the DNAm levels between AC and preAC samples (AGDMPs) and (ii) DMPs that were obtained from a comparison of the DNAm levels between obese and lean AC samples (ACDMPs). These two classes of DMPs were obtained to identify a relationship between adipogenesis and obesity. We also investigated how hyper and hypomethylation of the promoter and/or gene body differentially affected changes in gene expression by estimating the odds ratios (ORs) of changes in gene expression without DMPs in the background. Interestingly, the magnitude of DNAm alterations during AC differentiation was greater under lean conditions than under obese conditions. In conclusion, several adipogenesis-related genes were affected by complicated methylation changes and ultimately cause differences in gene expression in ACs under lean and obese conditions.