Effects of a 10-days preventive treatment of grape seed proanthocyanidin extract (GSPE) on (A) GLP-1 receptor gene expression, (B) DNA methylation on five CpG sites of a region of the GLP-1R promoter, (C) average DNA methylation from the CpG sites of a region of GLP-1R promoter, (D) DNMT-1 relative gene expression, (E) localization of the CpG sites (numbered 1–5) and of the putative binding site for the indicated transcription factor (framing) in the region flanking the rat GLP-1R gene transcription start site (+1) studied, and (F) GgG relative gene expression in the ileum. The data are the mean ± standard error of the mean (S.E.M.; n = 7–10) One-way ANOVA p < 0.05 was used to compare differences between the groups, obtained by a DMS posthoc test and defined by different letters.