Recent chronobiological studies found significant correlation between lack of clock function and metabolic abnormalities. We previously showed that clock gene expressions were dampened in the peripheral tissues of obese and diabetic ob/ob mice. However, the molecular mechanism of the disturbance remained to be determined. In this study, we demonstrated for the first time that acetylation levels of histone H3 lysine 9 (H3K9) at the promoter regions of clock genes, such as Dbp, Per2, and Bmal1, in the adipose tissue of ob/ob mice were significantly reduced compared with those of its control C57BL/6J mice. Treatment with histone deacetylase (HDAC) inhibitors increased Dbp, but not Per2 or Bmal1, mRNA expression in adipose tissue, and it decreased blood glucose in these animals. In addition, 2-deoxyglucose uptake activity was significantly suppressed by silencing Dbp expression in cultured adipocytes. These results suggest that reduced H3K9 acetylation and subsequent decreased mRNA expression of the Dbp gene in adipose tissue are involved in the mechanism of development of abnormal glucose metabolism in ob/ob mice.

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