SIRT1 and Hyperglycemia: Inhibition of the O-GlcNAc-modified form of SIRT1 contributes to hyperglycemia by promoting the transcription of PGC-1α and FOXO1, resulting in the increased expression of phosphoenolpyruvate carboxykinase (PEPCK) and G6Pase, therefore enhancing liver gluconeogenesis [69].