FOXO1 and type 1 diabetes mellitus: For example, L-Methionine (L-Met) regulates FoxO1 by altering the bivalent domain histone methylation marks H3K27me3 and H3K4me3 to increase FoxO1-mediated upregulation of the insulin transcription factor MafA and mitigate type 1 diabetes mellitus in rats (174).