Hypoglycemic Effects of Turmeric (Curcuma longa L. Rhizomes) on Genetically Diabetic KK-Ay Mice

The turmeric (Curcuma longa L. rhizomes) EtOH extract significantly suppressed an increase in blood glucose level in type 2 diabetic KK-Ay mice. In an in vitro evaluation, the extract stimulated human adipocyte differentiation in a dose-dependent manner and showed human peroxisome proliferator-activated receptor (PPAR)-γ ligand-binding activity in a GAL4-PPAR-γ chimera assay. The main constituents of the extract were identified as curcumin, demethoxycurcumin, bisdemethoxycurcumin, and ar-turmerone, which had also PPAR-γ ligand-binding activity. These results indicate that turmeric is a promising ingredient of functional food for the prevention and/or amelioration of type 2 diabetes and that curcumin, demethoxycurcumin, bisdemethoxycurcumin, and ar-turmerone mainly contribute to the effects via PPAR-γ activation.