Induction of uncoupling protein-1 and -3 in brown adipose tissue by kaki-tannin in type 2 diabetic NSY/Hos mice

Kaki-tannin, a highly polymerized-tannin from the young fruits of persimmon (Diospyros kaki ‘Hachiya’), has been shown to have bile acid-binding activity. To verify the effect of kaki-tannin on the metabolism of lipid and glucose in type 2 diabetes, type 2 diabetic NSY/Hos mice were fed an AIN76-modified high fat diet supplemented with 1% (w/w) kaki-tannin for 8 weeks. Kaki-tannin induced a 2-fold increase in fecal bile acid excretion and was significantly effective in the prevention of a rise in plasma cholesterol, triglyceride, and insulin levels. Kaki-tannin treatment also prevented fatty liver. To identify the molecular mechanism underlying these effects, gene expression analysis was performed on liver, brown adipose tissue (BAT), and skeletal muscle. The genes related to cholesterol metabolism, including 3-hydroxy-3-methylglutaryl-coenzyme A reductase and sterol regulatory element-binding protein 2, were increased in the liver of the kaki-tannin group. Interestingly, the uncoupling protein-1 (UCP1) gene and the UCP3 gene were significantly increased in the BAT of the kaki-tannin group, which was also confirmed at the protein level. These findings indicated that induction of UCP1 and UCP3 in the BAT by kaki-tannin treatment might influence the energy metabolism, thus contributing beneficial effects to type 2 diabetic NSY/Hos mice.