Daphnetin Improves Insulin Resistance and Metabolic Dysfunction in High-Fat Diet-Fed Mice

Background: Daphnetin is a naturally occurring coumarin derivative that has diverse biological activities, but its effects on obesity-associated metabolic dysfunction and insulin resistance remain unclear. We therefore investigated the effects of daphnetin on glucose homeostasis, metabolic dysfunction, and adipocyte differentiation. Methods: Male C57BL/6 mice fed a high-fat diet (HFD), and 3T3-L1 cells were used to assess the effects of daphnetin. Additionally, the potential of DPP-4 as a molecular target of daphnetin was evaluated using molecular docking and molecular dynamics simulations together with a DPP-4 enzymatic activity assay. Results: Administration of daphnetin markedly improved glucose tolerance and insulin responsiveness in HFD-fed mice without changes in body weight and food intake. Moreover, daphnetin administration reduced hepatic lipid accumulation, decreased expression of lipogenic genes and increased expression of Cpt1a, which is associated with fatty acid oxidation. In adipose tissue, daphnetin treatment attenuated adipocyte hypertrophy and suppressed adipogenic and lipogenic gene expression in white adipose tissue. Consistent with these results, daphnetin treatment suppressed the expression of adipogenic and lipogenic marker genes and inhibited lipid accumulation in differentiating 3T3-L1 cells, without affecting cell viability. Molecular docking and molecular dynamics simulations supported a potential interaction between daphnetin and DPP-4. In vitro DPP4 activity assays showed that daphnetin inhibits DPP-4 activity in a dose-dependent manner. As such, daphnetin treatment promoted AMPK activation while decreasing ERK phosphorylation. Conclusions: Our findings suggest that daphnetin treatment attenuates the development of HFD-associated glucose intolerance and hepatic steatosis in mice.