Supplementary Material for: Experimental environment is a determinant of gene methylation and one-carbon metabolism in obese adult mice

Background: Diet-induced obesity (DIO) leads to insulin resistance (IR) and alters gene expression through epigenetic mechanisms, including DNA methylation. Here, we aimed to investigate whether experimental environment is an important variable in determining DNA methylation and one-carbon metabolism in DIO mice fed a multi-vitamin-mineral mixture (MVM). Methods: Three experiments with identical design were conducted in three independent animal facilities (i.e. experimental environments or locations). In each location, 12-week-old male C57BL/6J mice were randomly assigned to two dietary groups: high-fat (HF) and HF-MVM for an average of 10 weeks. Global and gene-specific methylation of adipose function related genes in epididymal white adipose tissue (eWAT), and insulin signaling genes in the liver were analyzed using bisulfite pyrosequencing. Hepatic 1-C metabolites were measured and the ratio of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) was used as an indicator of methylation potential. Results: Experimental location affected global methylation patterns in eWAT, but not in the liver. At the gene-specific level, experimental location, MVM, and their interaction altered the methylation of genes related to adipose function (Srebf1, Acaca, Fasn, Pparg, and Rbp4) in eWAT and insulin signaling (Pi3kr1 and Akt1) in the liver (P < 0.05). The SAM/SAH ratio was correlated with gene-specific methylation at some CpG sites of Srebf1, Pi3kr1, Acaca, Fasn, Pparg, Rbp4, and Akt1) genes (P < 0.05). Conclusion: The experimental environment is a significant determinant of the effects of micronutrient supplement on 1-C metabolism and the methylation of genes associated with IR in tissues of DIO adult male mice.