Effects of grape seed extract and its ethylacetate/ethanol fraction on blood glucose levels in a model of type 2 diabetes

The present study observed the effects of grape seed extract (GSE) and its ethylacetate (E) and ethylacetate/ethanol (EE) fractions on blood glucose levels in C57BL/KsJ-lepr(db)/lepr(db) (db/db) mice at 4-12 weeks of age. In the GSE- and EE fraction-treated db/db group, the blood glucose concentration began to be lower than that in the vehicle-treated db/db group at 6 weeks after treatment, while the blood glucose concentration in the E fraction-treated db/db group was similar to that in the vehicle-treated db/db group. The glycosylated hemoglobin (HbA1c) level in the vehicle-treated db/db groups was 9.3%, whereas HbA1c levels in the GSE- and EE fraction-treated db/db group decreased significantly to 5.7% and 6.1%, respectively, at 8 weeks after treatment. However, administration of GSE and its EE fraction did not show any significant effects on body weights and food consumption in db/db mice. These results suggest that GSE and its EE fraction have a potential to decrease the blood glucose and HbA1c level, which is applicable to good healthy foods for reducing blood glucose levels.