Turmeric, the rhizome of
Curcuma longa L., has a wide range of effects on human health. Thechemistry includes curcuminoids and sesquiterpenoids as components, which are known to haveantioxidative, anticarcinogenic, and antiinflammatory activities. In this study, we investigated the effectsof three turmeric extracts on blood glucose levels in type 2 diabetic KK-A
y mice (6 weeks old,
n =5/group). These turmeric extracts were obtained by ethanol extraction (E-ext) to yield bothcurcuminoids and sesquiterpenoids, hexane extraction (H-ext) to yield sesquiterpenoids, and ethanolextraction from hexane-extraction residue (HE-ext) to yield curcuminoids. The control group wasfed a basal diet, while the other groups were fed a diet containing 0.1 or 0.5 g of H-ext or HE-ext/100g of diet or 0.2 or 1.0 g of E-ext/100 g of diet for 4 weeks. Although blood glucose levels in thecontrol group significantly increased (
P < 0.01) after 4 weeks, feeding of 0.2 or 1.0 g of E-ext, 0.5 gof H-ext, and 0.5 g of HE-ext/100 g of diet suppressed the significant increase in blood glucoselevels. Furthermore, E-ext stimulated human adipocyte differentiation, and these turmeric extractshad human peroxisome proliferator-activated receptor-
(PPAR-
) ligand-binding activity in a GAL4-PPAR-
chimera assay. Also, curcumin, demethoxycurcumin, bisdemethoxycurcumin, and ar-turmerone had PPAR-
ligand-binding activity. These results indicate that both curcuminoids andsesquiterpenoids in turmeric exhibit hypoglycemic effects via PPAR-
activation as one of themechanisms, and suggest that E-ext including curcuminoids and sesquiterpenoids has the additiveor synergistic effects of both components.Keywords:
Curcuma longa L.; turmeric extract; curcuminoid; sesquiterpenoid; type 2 diabetes; KK-A
y mice; PPAR-
ligand