SIK1 and diabetes mellitus: Because phosphorylation at Ser577, which occurred either by the action of PKA or by autophosphorylation, cause the cytoplasmic localization of SIK1 and thus results in a reduction of the transcriptional modulating activity of SIK1 [6], we speculated that hyperglycemia might enhance PKA-mediated phosphorylation at Ser577 or autophosphorylation at Ser577 under diabetic conditions, thus leading to a significant increase in the level of SIK1 phosphorylation at Ser577, but further elucidation of phosphorylation of SIK1 at Ser577 will be needed in the condition of diabetes.