Effects of SLC19A1 silencing in human adipocytes. In vitro differentiated primary adipocytes were transfected with siSLC19A1. This resulted in (A) reduced intracellular folic acid, methionine, SAM levels, and SAM/SAH ratio and (B) an increase in global DNA methylation measured using an ELISA (detailed in Supplemental Table 2). (C) Venn diagram summarizing the bioinformatic approach to identify SLC19A1-regulated genes linked to altered methylation of proximal CpG loci. A total of 186 genes fulfilled the following criteria: regulated in SLC19A1 silenced adipocytes (purple circle), correlated with SLC19A1 expression in WAT (yellow circle; subcohort 1), and had at least one neighboring CpG in which methylation was associated with gene expression (gray circle; subcohort 1). Of these, 101 genes displayed a direction in expression congruent with data obtained in vitro and in vivo. (D) GO analyses of the 101 genes subdivided according to the direction of gene expression in relation to SLC19A1 expression in vitro and in vivo. The top five pathways according to statistical significance are shown; the full list is detailed in Supplemental Table 7. Analyses of (E) mRNA expression and (F) protein secretion confirmed that CCL2 was selectively upregulated in vitro on SLC19A1 silencing. In cohort 2, SLC19A1 expression in subcutaneous WAT was substantially associated with (G) CCL2 secretion (in multiple regression analysis, β coefficient, −0.34 and P = 0.003 after BMI correction) from WAT explants ex vivo and (H) serum CCL2 levels (in multiple regression analysis, β coefficient, −0.27 and P = 0.048 after BMI correction). *P < 0.05, **P < 0.01, ***P < 0.001.