In this study, we found that the expression of hepatic SIK1 was markedly decreased in the HFD/STZ-induced T2DM rat model and that administration of Ad-SIK1 lowered fasting blood glucose and ameliorated fatty liver disease, suggesting that a reduction of SIK1 may contribute to the glucose and lipid metabolism disorder in diabetes. The gene discussed is SIK1; the disease is fatty liver disease.